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OBJECTIVE The tumor characteristics and surgical outcomes of intracranial subependymomas are poorly defined. In this study the authors aimed to provide a comprehensive review of all clinical, pathological, radiological, and surgical aspects of this important neoplasm to inform future management strategies. METHODS A systematic review and meta-analysis of MEDLINE, EMBASE, Cochrane, and Google Scholar databases adherent to PRISMA guidelines was conducted. RESULTS Of the 1145 articles initially retrieved, 24 studies encompassing 890 cases were included. The authors identified 3 retrospective cohort studies and 21 case series, but no controlled trials. Mean age at presentation was 46.7 ± 18.1 years with a male predominance (70.2%). Common sites of tumor origin were the lateral ventricle (44.5%) and fourth ventricle (43.1%). Cumulative postoperative mortality and morbidity rates were 3.4% and 24.3% respectively. Meta-analysis revealed that male sex (HR 3.15, 95% CI 1.39–7.14, p = 0.006) was associated with poorer 5-year overall mortality rates. All-cause mortality rates were similar when performing subgroup meta-analyses for age (HR 0.50, 95% CI 0.03–7.36, p = 0.61), smaller subependymoma size (HR 1.51, 95% CI 0.78–2.92, p = 0.22), gross-total resection (HR 0.65, 95% CI 0.35–1.23, p = 0.18), and receipt of postoperative radiation therapy (HR 0.88, 95% CI 0.27–2.88, p = 0.84). Postoperative Karnofsky Performance Index scores improved by a mean difference of 1.62 ± 12.14 points (p = 0.42). The pooled overall 5-year survival rate was 89.2%, while the cumulative recurrence rate was 1.3% over a median follow-up ranging from 15.3 to 120.0 months. The pure subependymoma histopathological subtype was most prevalent (85.6%), followed by the mixed subependymoma-ependymoma tumor variant (13.7%). CONCLUSIONS Surgical extirpation without postoperative radiotherapy results in excellent postoperative survival and functional outcomes in the treatment of intracranial subependymomas. Aggressive tumor behavior should prompt histological reevaluation for a mixed subependymoma-ependymoma subtype. Further high-quality controlled trials are still required to investigate this rare tumor.

OBJECTIVETrapped temporal horn (TTH) is a rare subtype of loculated hydrocephalus that is often managed surgically. The natural history of TTH is not well understood, and there are few data on the outcomes of conservative management of this condition. The aim of this study was to analyze the clinical features and outcomes of conservatively and surgically managed cases of TTH.METHODSThe authors retrospectively reviewed the clinical data for 19 consecutive cases of TTH that developed after microsurgical resection of lateral ventricular trigone meningioma between 2011 and 2015.RESULTSThe 19 cases involved 6 male and 13 female patients (mean age [± SD] 39.9 ± 13.8 years). The mean time interval from tumor resection to onset of TTH was 3.2 ± 3.0 months (range 3 days–10 months). Symptoms of intracranial hypertension were the most common complaints at presentation. The mean Karnofsky Performance Scale (KPS) score at onset was 52.1 ± 33.3 (range 10–90). Midline shift was observed in 15 cases (78.9%), and the mean amount of midline shift was 6.0 ± 4.8 mm (range 0–15 mm). Eleven cases (57.9%) were managed with surgical intervention, while 8 cases (42.1%) were managed conservatively. All patients (100%) showed improved clinical status over the course of 4.8 ± 1.0 years (range 2.8–6.3 years) of follow-up. The mean KPS score at last follow-up was 87.9 ± 11.3 (range 60–100). Eighteen patients (94.7%) showed signs of radiographic improvement, and 1 patient (5.3%) exhibited stable size of the temporal horn. Significant differences were observed between the surgical and nonsurgical cohorts for the following variables: KPS score at onset, presence of intracranial hypertension, and midline shift. The mean KPS score at onset was greater (better) in the nonsurgical group than in the surgical group (82.5 ± 8.9 vs 30 ± 25.7, p = 0.001). A greater proportion of patients in the surgical group presented with symptoms of intracranial hypertension (81.8% vs 0%, p = 0.001). The extent of midline shift was greater in the surgical group than in the nonsurgical group (9.0 ± 3.8 mm vs 2.0 ± 2.4 mm, p = 0.001).CONCLUSIONSThe majority of patients with TTH presented in a delayed fashion. TTH is not always a surgical entity. Spontaneous resolution of TTH may be under-reported. Conservative management with clinical and radiological follow-up is effective in selected patients.

OBJECTIVEThe best approach to deep-seated lateral and third ventricle lesions is a function of lesion characteristics, location, and relationship to the ventricles. The authors sought to examine and compare angles of attack and surgical freedom of anterior ipsilateral and contralateral interhemispheric transcallosal approaches to the frontal horn of the lateral ventricle using human cadaveric head dissections. Illustrative clinical experiences with a contralateral interhemispheric transcallosal approach and an anterior interhemispheric transcallosal transchoroidal approach are also related.METHODSFive formalin-fixed human cadaveric heads (10 sides) were examined microsurgically. CT and MRI scans obtained before dissection were uploaded and fused into the navigation system. The authors performed contralateral and ipsilateral transcallosal approaches to the lateral ventricle. Using the navigation system, they measured areas of exposure, surgical freedom, angles of attack, and angle of view to the surgical surface. Two clinical cases are described.RESULTSThe exposed areas of the ipsilateral (mean [± SD] 313.8 ± 85.0 mm2) and contralateral (344 ± 87.73 mm2) interhemispheric approaches were not significantly different (p = 0.12). Surgical freedom and vertical angles of attack were significantly larger for the contralateral approach to the most midsuperior reachable point (p = 0.02 and p = 0.01, respectively) and to the posterosuperior (p = 0.02 and p = 0.04) and central (p = 0.04 and p = 0.02) regions of the lateral wall of the lateral ventricle. Surgical freedom and vertical angles of attack to central and anterior points on the floor of the lateral ventricle did not differ significantly with approach. The angle to the surface of the caudate head region was less steep for the contralateral (135.6° ± 15.6°) than for the ipsilateral (152.0° ± 13.6°) approach (p = 0.02).CONCLUSIONSThe anterior contralateral interhemispheric transcallosal approach provided a more expansive exposure to the lower two-thirds of the lateral ventricle and striothalamocapsular region. In normal-sized ventricles, the foramen of Monro and the choroidal fissure were better visualized through the lateral ventricle ipsilateral to the craniotomy than through the contralateral approach.

OBJECTIVE The relationship of the white matter tracts to the lateral ventricles is important when planning surgical approaches to the ventricles and in understanding the symptoms of hydrocephalus. The authors' aim was to explore the relationship of the white matter tracts of the cerebrum to the lateral ventricles using fiber dissection technique and MR tractography and to discuss these findings in relation to approaches to ventricular lesions. METHODS Forty adult human formalin-fixed cadaveric hemispheres (20 brains) and 3 whole heads were examined using fiber dissection technique. The dissections were performed from lateral to medial, medial to lateral, superior to inferior, and inferior to superior. MR tractography showing the lateral ventricles aided in the understanding of the 3D relationships of the white matter tracts with the lateral ventricles. RESULTS The relationship between the lateral ventricles and the superior longitudinal I, II, and III, arcuate, vertical occipital, middle longitudinal, inferior longitudinal, inferior frontooccipital, uncinate, sledge runner, and lingular amygdaloidal fasciculi; and the anterior commissure fibers, optic radiations, internal capsule, corona radiata, thalamic radiations, cingulum, corpus callosum, fornix, caudate nucleus, thalamus, stria terminalis, and stria medullaris thalami were defined anatomically and radiologically. These fibers and structures have a consistent relationship to the lateral ventricles. CONCLUSIONS Knowledge of the relationship of the white matter tracts of the cerebrum to the lateral ventricles should aid in planning more accurate surgery for lesions within the lateral ventricles.

OBJECTIVEThe septum pellucidum is a bilateral thin membranous structure representing the border between the frontal horns of the lateral ventricles. Its most examined components are the septal veins due to their surgical importance during endoscopic septum pellucidotomy (ESP), which is a well-accepted method for surgical treatment of unilateral hydrocephalus. It is widely accepted that the septum pellucidum contains nerve fibers as well, but interestingly, no anatomical study has been addressed to its neural components before. The aim of the present study was to identify these elements as well as their relations to the septal veins and to define major landmarks within the ventricular system for neurosurgical use.METHODSNine formalin-fixed human cadaveric brains (18 septa pellucida) were involved in this study. A central block containing both septa pellucida was removed and frozen at −30°C for 2 weeks in 7 cases. The fibers of the septum pellucidum and the adjacent areas including the venous elements were dissected under magnification by using homemade wooden spatulas and microsurgical instruments. In 2 cases a histological technique was used to validate the findings of the dissections. The blocks were sliced, embedded in paraffin, cut in 7-µm-thick slices, and then stained as follows: 1) with H & E, 2) with Luxol fast blue combined with cresyl violet, and 3) with Luxol fast blue combined with Sirius red.RESULTSThe septum pellucidum and the subjacent septum verum form the medial wall of the frontal horn of the lateral ventricle. Both structures contain nerve fibers that were organized in 3 groups: 1) the precommissural fibers of the fornix; 2) the inferior fascicle; and 3) the superior fascicle of the septum pellucidum. The area directly rostral to the postcommissural column of the fornix consisted of macroscopically identifiable gray matter corresponding to the septal nuclei. The histological examinations validated the findings of the authors’ fiber dissections.CONCLUSIONSThe nerve elements of the septum pellucidum as well as the subjacent septum verum were identified with fiber dissection and verified with histology for the first time. The septal nuclei located just anterior to the fornix and the precommissural fibers of the fornix should be preserved during ESP. Considering the venous anatomy as well as the neural architecture of the septum pellucidum, the fenestration should ideally be placed above the superior edge of the fornix and preferably dorsal to the interventricular foramen.

OBJECT The cerebral isthmus is the white matter area located between the periinsular sulcus and the lateral ventricle. Studies demonstrating the fiber tract and topographic anatomy of this entity are lacking in current neurosurgical literature. Hence, the authors’ primary aim was to describe the microsurgical white matter anatomy of the cerebral isthmus by using the fiber dissection technique, and they discuss its functional significance. In addition, they sought to investigate its possible surgical utility in approaching lesions located in or adjacent to the lateral ventricle. METHODS This study was divided into 2 parts and included 30 formalin-fixed cerebral hemispheres, 5 of which were injected with colored silicone. In the first part, 15 uncolored specimens underwent the Klinger’s procedure and were dissected in a lateromedial direction at the level of the superior, inferior, and anterior isthmuses, and 10 were used for coronal and axial cuts. In the second part, the injected specimens were used to investigate the surgical significance of the superior isthmus in accessing the frontal horn of the lateral ventricle. RESULTS The microsurgical anatomy of the anterior, superior, and inferior cerebral isthmuses was carefully studied and recorded both in terms of topographic and fiber tract anatomy. In addition, the potential role of the proximal part of the superior isthmus as an alternative safe surgical corridor to the anterior part of the lateral ventricle was investigated. CONCLUSIONS Using the fiber dissection technique along with coronal and axial cuts in cadaveric brain specimens remains a cornerstone in the acquisition of thorough anatomical knowledge of narrow white matter areas such as the cerebral isthmus. The surgical significance of the superior isthmus in approaching the frontal horn of the lateral ventricle is stressed, but further studies must be carried out to elucidate its role in ventricular surgery.

OBJECTIVEPostoperative decrease in ventricle size is usually not detectable either by visual assessment or by measuring the Evans index in patients with idiopathic normal pressure hydrocephalus (iNPH). The aim of the present study was to investigate whether the angle between the lateral ventricles (the callosal angle [CA]) increases and ventricular volume decreases after shunt surgery in patients with iNPH.METHODSMagnetic resonance imaging of the brain was performed before and 3 months after shunt surgery in 18 patients with iNPH. The CA and Evans index were measured on T1-weighted 3D MR images, and ventricular volume contralateral to the shunt valve was measured with quantitative MRI.RESULTSThe CA was larger postoperatively (mean 78°, 95% CI 69°–87°) than preoperatively (mean 67°, 95% CI 60°–73°; p < 0.001). The volume of the lateral ventricle contralateral to the shunt valve decreased from 73 ml (95% CI 66–80 ml) preoperatively to 63 ml (95% CI 54–72 ml) postoperatively (p < 0.001). The Evans index was 0.365 (95% CI 0.35–0.38) preoperatively and 0.358 (95% CI 0.34–0.38) postoperatively (p < 0.05). Postoperative change of CA showed a negative correlation with change of ventricular volume (r = −0.76, p < 0.01).CONCLUSIONSIn this sample of patients with iNPH, the CA increased and ventricular volume decreased after shunt surgery. The relative difference was most pronounced for the CA, indicating that this accessible, noninvasive radiological marker should be evaluated further as an indirect method to determine shunt function in patients with iNPH.

Object Recent neuroimaging and surgical results support the crucial role of white matter in mediating motor and higher-level processing within the frontal lobe, while suggesting the limited compensatory capacity after damage to subcortical structures. Consequently, an accurate knowledge of the anatomofunctional organization of the pathways running within this region is mandatory for planning safe and effective surgical approaches to different diseases. The aim of this dissection study was to improve the neurosurgeon's awareness of the subcortical anatomofunctional architecture for a lateral approach to the frontal region, to optimize both resection and postoperative outcome. Methods Ten human hemispheres (5 left, 5 right) were dissected according to the Klingler technique. Proceeding lateromedially, the main association and projection tracts as well as the deeper basal structures were identified. The authors describe the anatomy and the relationships among the exposed structures in both a systematic and topographical surgical perspective. Structural results were also correlated to the functional responses obtained during resections of infiltrative frontal tumors guided by direct cortico-subcortical electrostimulation with patients in the awake condition. Results The eloquent boundaries crucial for a safe frontal lobectomy or an extensive lesionectomy are as follows: 1) the motor cortex; 2) the pyramidal tract and premotor fibers in the posterior and posteromedial part of the surgical field; 3) the inferior frontooccipital fascicle and the superior longitudinal fascicle posterolaterally; and 4) underneath the inferior frontal gyrus, the head of the caudate nucleus, and the tip of the frontal horn of the lateral ventricle in the depth. Conclusions Optimization of results following brain surgery, especially within the frontal lobe, requires a perfect knowledge of functional anatomy, not only at the cortical level but also with regard to subcortical white matter connectivity.

OBJECTIVE Conventional approaches to the atrium of the lateral ventricle may be associated with complications related to direct cortical injury or brain retraction. The authors describe a novel approach to the atrium through a retrosigmoid transtentorial transcollateral sulcus corridor. METHODS Bilateral retrosigmoid craniotomies were performed on 4 formalin-fixed, colored latex–injected human cadaver heads (a total of 8 approaches). Microsurgical dissections were performed under 3× to 24× magnification, and endoscopic visualization was provided by 0° and 30° rigid endoscope lens systems. Image guidance was provided by coupling an electromagnetic tracking system with an open source software platform. Objective measurements on cortical thickness traversed and total depth of exposure were recorded. Additionally, the basal occipitotemporal surfaces of 10 separate cerebral hemisphere specimens were examined to define the surface topography of sulci and gyri, with attention to the appearance and anatomical patterns and variations of the collateral sulcus and the surrounding gyri. RESULTS The retrosigmoid approach allowed for clear visualization of the basal occipitotemporal surface. The collateral sulcus was identified and permitted easy endoscopic access to the ventricular atrium. The conical corridor thus obtained provided an average base working area of 3.9 cm2 at an average depth of 4.5 cm. The mean cortical thickness traversed to enter the ventricle was 1.4 cm. The intraventricular anatomy of the ipsilateral ventricle was defined clearly in all 8 exposures in this manner. The anatomy of the basal occipitotemporal surface, observed in a total of 18 hemispheres, showed a consistent pattern, with the collateral sulcus abutted by the parahippocampal gyrus medially, and the fusiform and lingual gyrus laterally. The collateral sulcus was found to be caudally bifurcated in 14 of the 18 specimens. CONCLUSIONS The retrosigmoid supracerebellar transtentorial transcollateral sulcus approach is technically feasible. This approach has the potential advantage of providing a short and direct path to the atrium, hence avoiding violation of deep neurovascular structures and preserving eloquent areas. Although this approach appears unconventional, it may provide a minimally invasive option for the surgical management of selected lesions within the atrium of the lateral ventricle.

OBJECTIVE Many colloid cyst patients present with obstructive hydrocephalus that resolves after resection of the cyst. However, a proportion of patients with these cysts will require cerebrospinal fluid shunting after tumor resection, despite resolution of the obstruction at the foramina of Monro. The goal of this study was to determine if colloid cyst size or preoperative ventricular volume predicted the need for postresection shunting. METHODS In a retrospective study design, ICD-9 codes 742.2 (colloid cyst) and 348.0 (brain cyst) were used to identify patients who had undergone resection of a colloid cyst at the University of Florida over the last 20 years. Preoperative imaging (CT or MRI) with a stereotactic software program developed at the University of Florida was used to measure volumes of the colloid cyst and the lateral ventricles. The relationships among ventricular volume, colloid cyst volume, and postoperative shunting were analyzed. RESULTS The number of patients included in the study was 67, and their mean age was 37.7 years. Forty percent of the patients were female. Overall, 49.2% of the patients had a transcallosal approach, 35.8% a transcortical approach, and 14.9% an endoscope-assisted surgery. Mean preoperative ventricular volume was 76.5 cc in patients who never received a ventriculoperitoneal shunt (VPS) and 98.1 cc in those who were eventually treated with a VPS (p = 0.305). Patients with a postoperative VPS had an initial mean colloid cyst volume of 1.8 cc compared with 0.9 cc in patients without a VPS postoperatively (p = 0.019). Patients with colloid cysts larger than 0.6 cc (1-cm diameter) had a 12.8 increased odds of needing a VPS postoperatively (95% CI 1.81–275). CONCLUSIONS Larger colloid cysts are associated with an increased need for postresection shunting independent of preoperative ventricular size. Prospective studies of patients with colloid cysts are necessary to further identify risks of permanent hydrocephalus.

Occlusion of both foramina of Monro following third ventriculostomy is a very rare complication. The authors present the case of a 30-year-old female who underwent endoscopic third ventriculostomy (ETV) for occlusive hydrocephalus due to aqueductal stenosis. Thirty months after the ETV, she reported recurrent headaches. Magnetic resonance imaging demonstrated bilateral enlargement of the lateral ventricles with a collapsed third ventricle caused by bilateral stenosis of the foramina of Monro. Left-sided endoscopic foraminoplasty and stenting of the left foramen of Monro were performed with immediate neurological improvement.

Object The authors examined the accuracy of anatomical targeting during electrode implantation for deep brain stimulation in functional neurosurgical procedures. Special attention was focused on the impact that ventricular involvement of the electrode trajectory had on targeting accuracy. Methods The targeting error during electrode placement was assessed in 162 electrodes implanted in 109 patients at 2 centers. The targeting error was calculated as the shortest distance from the intended stereotactic coordinates to the final electrode trajectory as defined on postoperative stereotactic imaging. The trajectory of these electrodes in relation to the lateral ventricles was also analyzed on postoperative images. Results The trajectory of 68 electrodes involved the ventricle. The targeting error for all electrodes was calculated: the mean ± SD and the 95% CI of the mean was 1.5 ± 1.0 and 0.1 mm, respectively. The same calculations for targeting error for electrode trajectories that did not involve the ventricle were 1.2 ± 0.7 and 0.1 mm. A significantly larger targeting error was seen in trajectories that involved the ventricle (1.9 ± 1.1 and 0.3 mm; p < 0.001). Thirty electrodes (19%) required multiple passes before final electrode implantation on the basis of physiological and/or clinical observations. There was a significant association between an increased requirement for multiple brain passes and ventricular involvement in the trajectory (p < 0.01). Conclusions Planning an electrode trajectory that avoids the ventricles is a simple precaution that significantly improves the accuracy of anatomical targeting during electrode placement for deep brain stimulation. Avoidance of the ventricles appears to reduce the need for multiple passes through the brain to reach the desired target as defined by clinical and physiological observations.

Object The mechanism of ventricular dilation in normal-pressure hydrocephalus remains unclear. Numerical finite-element (FE) models of hydrocephalus have been developed to investigate the biomechanics of ventricular enlargement. However, previous linear poroelastic models have failed to reproduce the relatively larger dilation of the horns of the lateral ventricles. In this paper the authors instead elaborated on a nonlinear poroplastic FE model of the brain parenchyma and studied the influence of the introduction of these potentially more realistic mechanical behaviors on the prediction of the ventricular shape. Methods In the proposed model the elasticity modulus varies as a function of the distension of the porous matrix, and the internal mechanical stresses are relaxed after each iteration, thereby simulating the probable plastic behavior of the brain tissue. The initial geometry used to build the model was extracted from CT scans of patients developing hydrocephalus, and the results of the simulations using this model were compared with the real evolution of the ventricular size and shape in the patients. Results The authors' model predicted correctly the magnitude and shape of the ventricular dilation in real cases of acute and chronic hydrocephalus. In particular, the dilation of the frontal and occipital horns was much more realistic. Conclusions This finding suggests that the nonlinear and plastic mechanical behaviors implemented in the present numerical model probably occur in reality. Moreover, the availability of such a valid FE model, whose mechanical parameters approach real mechanical properties of the brain tissue, might be useful in the further modeling of ventricular dilation at a normal pressure.

✓Cholesterol granulomas (CGs) are benign lesions resulting from an inflammatory reaction to cholesterol and hemosiderin. These masses most often arise within the temporal bone or nasal sinuses; intracerebral CGs are extremely rare. In this report the authors present an unusual case of a CG arising within the lateral ventricle. The patient presented with transient hemiparesis and numbness. Computed tomography and magnetic resonance imaging demonstrated a cystic partially enhancing midline mass within the right lateral ventricle, expanding the ventricle and displacing the septum pellucidum. The patient underwent an interhemispheric, transcallosal resection of the lesion. Microscopic examination revealed a granulomatous inflammatory lesion containing cholesterol clefts, macrophages, and hemosiderin. Embedded within the granulomatous response were foci of tiny cystlike structures lined by nonciliated flattened cuboidal epithelium, consistent with the diagnosis of CG. To the authors' knowledge this is the first reported case of CG presenting as an intraventricular mass. The origin of this lesion is unclear, but it may relate to prior traumatic brain injury. The authors describe the presentation, imaging findings, histopathological characteristics, and surgical treatment of this rare lesion and related pathological entities.

✓ A rare case of chordoid meningioma in the lateral ventricle observed in an adult is reported. The first clinical manifestation of the disease was a prolonged fever of unknown origin. Abnormalities in the patient's blood chemistry, principally polyclonal hypergammaglobulinemia (immunoglobulin [Ig]G, IgA, and markedly IgE) and an elevated serum level of C-reactive protein, were associated with the disease. The tumor was histologically confirmed to be a chordoid meningioma, and its surgical removal resulted in complete resolution of the patient's symptoms. By combining reverse transcription—polymerase chain reaction and immunohistochemical analysis, it may be shown that cytokine production, including that of interleukin (IL)-6, IL-1β, and vascular endothelial growth factor, plays a role in the pathogenesis of chordoid meningioma associated with Castleman syndrome.

Object. Knowledge of normal variations in ventricular morphological features is important in endoscopic neurosurgery. Classically, two elevations are described on the medial wall of the occipital horn of the lateral ventricle: an upper bulb and a lower calcar avis. Nevertheless, a third, as yet unreported elevation may be present at the junction of the medial wall and the floor of the occipital horn. The authors report the frequency with which this third elevation was found in a series of cadaveric brains. Methods. The medial wall of the occipital horn of the lateral ventricle was studied in the three orthogonal planes in 45 formalin-fixed cadaveric hemispheres. The underlying structures responsible for the observed intraventricular prominences were exposed by microdissection. A third elevation was present, lying ventrorostral to the calcar avis, in seven (47%) of the 15 single hemispheres, and bilaterally in six (40%) of the 15 whole brains. After microdissection, a fiber bundle from the splenium of the corpus callosum was seen emerging in the occipital horn at the angle between the tail of the hippocampus and the bulb of the occipital horn. The most rostral fibers fanned out inferolaterally along the floor of the collateral trigone. The larger, posterior part protruded into the medial wall along the ventral border of the calcar avis as far as the tip of the occipital horn. Conclusions. Besides its importance as a variation of normal ventricular morphological features, the close relationship of this accessory intraventricular prominence to the tail of the hippocampus should be kept in mind when intervening neurosurgically so that damage to the underlying commissural fibers can be avoided.

Corpus callosotomy offers useful palliation for selected patients with medically intractable seizures, particularly those with uncontrolled and disabling drop attacks. Here the authors present their technique for performing a corpus callosotomy that allows for complete sectioning of the callosum while avoiding entry into the lateral ventricles. The anatomical basis for the technique is the presence of a definable cleft just ventral to the corpus callosum in the midline, formed by the fusion of the two laminae of the septum pellucidum. This small cleft is typically present even in the absence of a cavum septum pellucidum on MR imaging. The authors have found that dividing the body of the corpus callosum by exploiting the cleft of the septum pellucidum in the absolute midline is a simple and expeditious way to perform a callosotomy without entering the lateral ventricles.

The temporal horn of the lateral ventricle is a complex structure affected by specific pathological conditions. Current approaches to the temporal horn involve a certain amount of corticotomy and white matter disruption. Surgeons therefore set aside anterior temporal lobectomy as a last resource and avoid it in the dominant hemisphere. The authors propose a minimally invasive endoscopic intraventricular approach to the temporal horn and describe a standardized analysis and technical assessment of the feasibility of this approach.To determine the best trajectory, angulation, and entry point to the temporal horn of the lateral ventricle, the authors evaluated 50 cranial MRI studies (100 temporal lobes) from healthy patients. They studied and systematized the neurosurgical endoscopic anatomy. They also simulated the proposed approach in 9 cadaveric specimens (18 approaches).Mean scalp entry point coordinates (± SD) were 2.7 ± 0.28 cm lateral to the inion and 5.6 ± 0.41 cm superior to the inion. The mean total distance from the uncal recess to the scalp (± SD) was 10.64 ± 0.6 cm. The mean total intraparenchymal distance crossed by the endoscope was 3.76 ± 0.36 cm. The approach was successfully completed in all studied specimens.In this study, the endoscopic intraventricular approach to the temporal horn is standardized. The morphometric analysis makes this approach anatomically feasible and replicable. This approach provides minimally invasive endoscopic access to the uncal recess, amygdala, hippocampus, fornix, and paraventricular temporal lobe structures. The following essential strategies enabled access to and maneuverability inside the temporal horn: tailored preoperative planning of the trajectory and use of anatomical and radiological references, constant irrigation, and an angled endoscopic lens. Safety assessment and novel instruments and techniques may be proposed to advance this very promising route to pathological changes in the temporal lobe.

✓ The authors present a rare case of a giant intracranial mucocele associated with an orbitoethmoidal osteoma in a patient suffering from a generalized convulsive disorder. The broad pedicle of the osteoma had penetrated the cribriform plate and extended intracranially to form a nodular mass in the olfactory groove. The intracranial portion of the osteoma was surrounded by a mucocele. Both the cyst wall and multilayered intracystic septations of the mucocele were indented by layers of the osteoma. Although the extracranial portion adhered to the mucosa of the ethmoidal sinus, there were no signs of sinus obstruction. No direct communication other than the osteoma was identified between the mucocele and the ethmoidal mucosa. The large cerebral defect, which the mucocele occupied, communicated directly with the lateral ventricle without any intervening membranous structures. A frontal craniotomy is recommended for exposure of the lesion and plastic repair of the dural defect.

Object. In this report the authors review their 3-year experience with the endoscopic management of patients with hydrocephalus who harbored cysticercal cysts within the third and lateral ventricles. The management plan was to utilize an endoscopic approach to remove the cysts and to incorporate techniques useful in treating obstructive hydrocephalus. The ultimate goals were to avoid having to place a complication-prone cerebrospinal fluid shunt and to eliminate the risk of complications related to cyst degeneration.Methods. A retrospective analysis of 10 patients with hydrocephalus and cysticercal cysts within the third or lateral ventricles who were endoscopically managed was performed. A general description of the instrumentation and technique used for removal of the intraventricular cysts is given. At presentation, neuroimaging revealed findings suggestive of obstructive hydrocephalus in eight patients.Seven of the 10 patients treated endoscopically were spared the necessity of shunt placement. Three successful third ventriculostomies and one therapeutic septum pellucidotomy were performed. Despite frequent rupture of the cyst walls during removal of the cysts, there were no cases of ventriculitis. The endoscopic approach allowed successful removal of a cyst situated in the roof of the anterior third ventricle. One patient suffered from recurrent shunt obstructions secondary to a shunt-induced migration of cysts from the posterior fossa to the lateral ventricles.Conclusions. The endoscopic removal of third and lateral ventricle cysticercal cysts, combined with a third ventriculostomy or septum pellucidotomy in selected cases, is an effective treatment in patients with hydrocephalus and should be considered the primary treatment for this condition.

Object Cadavers are often used in the teaching of various neurosurgical procedures. One aspect of this resource that has not been previously explored is the postmortem dilation of the ventricular system, which is often collapsed, for the purpose of training neurosurgeons in the use of intraventricular endoscopy. Methods Nine adult cadavers without a history of hydrocephalus or other known intracranial pathology were used for this study. Four specimens were obtained post embalming, and 5 specimens were fresh (time from death until the procedure < 5 hours). In all cadavers catheters were placed into the lateral ventricles; saline and then air were injected into the ventricles through the catheters. Ventriculostomy sites were filled with rubber stoppers, and in fresh specimens, formal embalming was performed with cadavers in the Trendelenburg position. Lastly, serial horizontal sectioning of the cranium was performed in all cadavers to verify ventricular dilation. Results None of the 4 embalmed specimens were found to have ventriculomegaly following injection. However, this condition was found in 4 of the 5 fresh specimens. In the single fresh cadaver without ventriculomegaly, the cause of death had been massive intracranial subarachnoid hemorrhage, which distorted the ventricular system. This may have prevented cannulation of the ventricle and ventricular expansion in this specimen. Conclusions The ventricular system of fresh human cadavers can be dilated postmortem. The method described herein may be useful to neurosurgical trainees or those trained neurosurgeons wishing to practice intraventricular endoscopy.

Object. The authors describe a subgroup of patients with shunt-proven normal-pressure hydrocephalus (NPH) who presented with focal fissural and sulcal dilation on imaging studies. The specific radiological features and methods of differentiating this condition from cortical atrophy are delineated. Methods. Normal-pressure hydrocephalus has been described as dilation of the ventricles that is out of proportion to the sulci. Sulcal dilation has been taken as evidence of cortical atrophy and has even been used as a criterion to exclude patients from undergoing a shunting procedure. The authors describe five cases of patients with shunt-proven NPH who presented with focal dilation of cortical fissures and sulci. In three of the cases, there was a paradoxical decrease in the size of the dilated fissures and sulci that paralleled the decrease in the size of the lateral ventricles following successful shunting. Conclusions. This study demonstrates that focal fissural and sulcal dilation may represent reservoirs of cerebrospinal fluid analogous to the ventricular system. Patients should not be denied a shunting procedure solely on the basis of focally dilated fissures of sulci.

Object The atrium of the lateral ventricle is often affected by tumors, and some patients with these tumors suffer neurological deficits, including hemiparesis after surgery. The authors of this study investigated the possible mechanisms causing the relatively high incidences of ischemic complications associated with surgery approaching the atrium of the lateral ventricle. Methods Clinical records and radiological images of 28 patients were retrospectively studied. These patients had their lateral ventricles opened at the atrium during the resection of gliomas as well as other nonbenign brain tumors, and were treated for gliomas at our tertiary referral center in the Tohoku district, Japan, between January 2008 and December 2010. Results Routine postoperative diffusion-weighted MR images obtained within 72 hours after surgery detected infarction in the periatrial/periventricular regions in 7 patients, presumably corresponding to the lateral posterior choroidal artery (LPChA) territory. Five of these 7 patients suffered neurological sequelae with varying severities. The choroid plexus at the atrium was coagulated to achieve hemostasis during the surgery in all of these patients. Detailed analysis of microangiograms revealed ventriculofugal arteries arising from the lateral ventricle. Damage of the subependymal artery that supplies the ventriculofugal arteries caused by coagulation of the choroid plexus at the atrium probably resulted in the infarction in these patients. Conclusions Neurosurgeons must be aware of the possibility of LPChA territory infarction during surgery in the atrial or periatrial regions caused by subependymal artery obstruction after manipulating or coagulating the choroid plexus near the atrium.

✓ The authors studied the effects of hydrocephalus on the high-energy phosphate metabolism of the brain and the impact of ventriculoperitoneal (VP) shunting on these changes in an experimental model of hydrocephalus. High-energy phosphate metabolism was analyzed using in vivo magnetic resonance (MR) imaging and 31P MR spectroscopy. Hydrocephalus was produced in 34 1-week-old kittens by cisternal injection of 0.05 ml of a 25% kaolin solution. Sixteen litter mates were used as controls. A VP shunt with a distal slit valve was implanted in 17 of the 34 hydrocephalic animals 10 days after induction of hydrocephalus. Both MR imaging and 31P MR spectroscopy were obtained 1 and 3 weeks after either kaolin or distilled water injection. Untreated hydrocephalic animals had marked dilatation of the lateral ventricles and periventricular edema. Magnetic resonance spectroscopy showed a significant decrease in the energy index ratio of phosphocreatine (PCR): inorganic phosphate (PI) and an increase in the PI:adenosine triphosphate (ATP) ratio. There was a direct correlation between the decrease in the energy index and ventricular size. Compared with preoperative scans, shunted animals showed no periventricular edema, and the ventricles decreased in size. Also, PCR:PI and PI:ATP ratios were within the levels of controls. This study suggests that neonatal hydrocephalus results in a mild hypoxic/ischemic insult that is treatable by VP shunting.

Corpus callosotomy offers useful palliation for selected patients with medically intractable seizures, particularly those with uncontrolled and disabling drop attacks. Here the authors present their technique for performing a corpus callosotomy that allows for complete sectioning of the callosum while avoiding entry into the lateral ventricles. The anatomical basis for the technique is the presence of a definable cleft just ventral to the corpus callosum in the midline, formed by the fusion of the two laminae of the septum pellucidum. This small cleft is typically present even in the absence of a cavum septum pellucidum on MR imaging. The authors have found that dividing the body of the corpus callosum by exploiting the cleft of the septum pellucidum in the absolute midline is a simple and expeditious way to perform a callosotomy without entering the lateral ventricles.

V ENTRICULOGRAPHY and encephalography, combined or separate, are established procedures in the preoperative diagnosis and localization of mass lesions of the brain, but seldom have they been utilized to study the evolution of anatomic changes following operation. In the course of a larger study being carried on at the Hospital of the University of Pennsylvania, we have had occasion to observe, by ventriculography and ventriculo-encephalography, three patients with mass lesions causing an internal hydrocephalus, before and after relief of the hydrocephalus. The significant feature that we wish to emphasize in this report is that dilatation of the lateral ventricles caused by obstructing lesions in the third or fourth ventricle may, in certain instances, be reversible.

The posterior interhemispheric transprecuneus gyrus approach is one of the surgical routes that has been suggested to reach the atrium of the lateral ventricle. It has the advantage of avoiding the disruption of the optic radiations; however, it has a narrow working area that at times makes the execution of this approach rather challenging. The aim of this study was to test a modification of the approach that might create a better surgical angle and a wider corridor by accessing the atrium from the contralateral side after transection of the falx. The authors named this new approach the "posterior interhemispheric transfalx transprecuneus approach."The posterior interhemispheic transfalx transprecuneus approach was performed bilaterally on 6 fresh adult cadaveric specimens for a total of 12 procedures. Every head was held in the semisitting position and a parasagittal parietooccipital craniotomy on the contralateral side of the targeted ventricle was executed. The dura mater was opened and reflected based on the sagittal sinus. Then the falx was cut in a triangular fashion based on the inferior sagittal sinus. Using the parietooccipital artery and sulcus as landmarks, the contralateral precuneus gyrus was indentified, and a small area of the gyrus was transected to gain access to the atrium. A neuronavigational system was also used to conduct this approach. The working angle of this approach and other distances were measured.The authors were able to visualize the ventricular atrium, posterior part of the temporal horn, pulvinar, and choroid plexus in all specimens. The temporal horn could be exposed for a length of 20-30 mm from the atrium. The working angle of the approach was better than that of the classic posterior interhemispheric transprecuneus approach with a mean value of 44.5° as opposed to 25.8°. The distance from the middle point of the corticotomy to the splenium ranged from 11 to 16 mm (mean 13.3 mm); the distance to the torcula, from 34 to 53 mm (mean 41.3 mm); and the distance to the atrium, from 22 to 31 mm (mean 25.7 mm).Results of this study suggested that the proposed approach can expose the atrium and the posterior part of the temporal horn of the lateral ventricle with a wider surgical angle compared with the conventional homolateral posterior interhemispheric transprecuneus gyrus approach. Moreover, by minimizing the amount of brain retraction homolateral to the target, this approach could make navigation more accurate.

Ventriculomegaly is a common imaging finding in many types of conditions. It is difficult to determine whether it is related to true hydrocephalus or to an atrophic process by using only imaging procedures such as MR imaging after traumatic injury, stroke, or infectious disease. Diffusion tensor (DT) imaging can distinguish the compression characteristics of white matter, indicating that increased diffusion anisotropy may be related to white matter compression. In this preliminary study, the authors compared the DT imaging findings of ventriculomegaly with those of chronic hydrocephalus or atrophy to clarify the potential of diffusion anisotropy in the identification of hydrocephalus.Ten patients with chronic hydrocephalus, 8 patients with atrophy (defined by conventional devices and surgical outcome), and 14 healthy volunteers underwent DT imaging. Images were acquired before and after shunting or once in cases without shunting. The fractional anisotropy (FA) values at many points around the lateral ventricle were evaluated.The FA patterns around the lateral ventricle in the chronic hydrocephalus and atrophy groups were different. Especially in the caudate nucleus, FA was increased in the chronic hydrocephalus group compared with the atrophy group. Furthermore, the FA values returned to normal levels after shunt placement.Assessment of the FA value of the caudate nucleus may be an important, less invasive method for distinguishing true hydrocephalus from ventriculomegaly. Further research in a large number of patients is needed to verify the diagnostic ability of this method.

Emergency access to the ventricular system is sometimes necessary for the treatment of raised intracranial pressure with ensuing herniation. One procedure described in the literature is a transorbital approach performed using a spinal needle. Because past publications have been case reports with minimal definition of external landmarks, the present study was performed.Five adult cadavers (10 sides) underwent transorbital puncture of the lateral ventricles. This approach was performed following an axial section through the cranium that exposed the lateral ventricular system. Landmarks for the ideal placement of catheters into the ventricular system were then evaluated.The authors found that the lateral ventricular system was consistently entered just superior to the level of the foramen of Monro by puncturing the roof of the orbit just medial to a midpupillary line, with the trajectory of the perforation aimed 45 degrees from a horizontal line and 15-20 degrees medial to a vertical line.Although it is uncommon, transorbital ventriculostomy may be used in emergency cases of raised intracranial pressure. Such refined landmarks as described in the present study may be of use to the neurosurgeon.

✓ Xanthogranulomas involving the choroid plexus of the lateral ventricles are generally asymptomatic lesions. The case is reported of a 50-year-old man in whom a xanthogranuloma of the choroid plexus had occluded the left trigone, causing unilateral hydrocephalus of the left temporal horn and neurological symptoms. A review of the literature shows that xanthogranulomas of the glomus of the lateral ventricles differ from the xanthomatous cystic lesions of the third ventricle, which are probably akin to colloid cysts.

Data from intracranial pressure (ICP) recordings in patients with hydrocephalus were reviewed to determine whether intracranial pulsatility within the cerebrospinal fluid (CSF) of cerebral ventricles (ICP(LV)) may differ from that within the brain parenchyma (ICP(PAR)), and whether pulsatility may differ between noncommunicating ventricles.The authors retrieved data from recordings previously obtained in 7 patients with hydrocephalus (noncommunicating in 4 and communicating in 3) and shunt failure who received both an external ventricular drainage (EVD) and an ICP sensor as part of surveillance during intensive care. Simultaneous ICP(LV) and ICP(PAR) signals were available in 6 cases, and simultaneous signals from the lateral and fourth ventricles (ICP(LV) and ICP4V, respectively) were recorded in 1 case. The recordings with both signals were parsed into 6-second time windows. Pulsatility was characterized by the wave amplitude and rise time coefficient, and differences in pulsatility between the ICP(LV) and ICP(PAR) signals (6 cases) or ICP(LV) and ICP4V signals (1 case) were determined.There was uneven distribution of intracranial pulsatility in all 7 patients, shown as significantly elevated pulsatility (that is, higher wave amplitudes and rise time coefficients) within the ventricles (ICP(LV)) than within brain parenchyma (ICP(PAR)) in 6 patients, and significantly higher pulsatility in the fourth (ICP4V) than in the lateral (ICP(LV)) ventricles in 1 patient. Differencesor = 1 mm Hg in ICP wave amplitude were found in 0.5-100% (median 9.4%) of observations in the 7 patients (total number of 6-second time windows, 68,242).The present observations demonstrate uneven distribution of intracranial pulsatility in patients with hydrocephalus, higher pulse pressure amplitudes within the ventricular CSF (ICP(LV)) than within the brain parenchyma (ICP(PAR)). This may be one mechanism behind ventricular enlargement in hydrocephalus.

Melanocytomas are rare tumors of the central nervous system that are believed to arise from leptomeningeal melanocytes. A young girl presented with a contrast-enhancing cystic mass in the temporal horn of the left lateral ventricle. Microsurgical resection of a black-colored vascular tumor supplied by the anterior choroidal artery was performed. Appropriate immunohistochemical staining and electron microscope evaluations were used to confirm the pathological diagnosis. The patient made an excellent recovery; follow-up imaging revealed no recurrent or residual tumor. This is the first documented primary occurrence of a melanocytoma in an intraventricular location. The intraventricular occurrence of this tumor suggests that melanocytes may migrate into the choroidal fissure and may infrequently undergo neoplastic proliferation in that location. This case contains implications for the differential diagnosis of intraventricular tumors.

✓The authors report a case of inflammatory pseudotumor that developed in the choroid plexus of the lateral ventricle. The patient was a 73-year-old man who had undergone surgery for rectal cancer at another hospital 5 years earlier. He was referred to the authors' department, with his chief symptoms consisting of disorientation, right hemiparesis, and gait disorder that had gradually developed during the preceding month. On computed tomography and magnetic resonance imaging, a well-demarcated and homogeneously contrasted tumorous lesion was noted in the region from the trigone to the medial wall of the inferior horn of the left lateral ventricle. Expansion of the inferior horn was also evident. Intraoperative findings showed that the tumor originated from the choroid plexus of the lateral ventricle, and the histopathological diagnosis was inflammatory pseudotumor. There are only 4 previously reported cases of inflammatory pseudotumor that developed in the choroid plexus; the authors review the literature and discuss the clinicopathological characteristics of the condition.

Object In this study, the authors used a fiber-dissection technique to describe the optic radiation. They focused on the morphological characteristics (length and breadth) of this structure, its course, and its relationships with neighboring fasciculi and the lateral ventricle. Methods The authors dissected 10 previously frozen, formalin-fixed human brains with the aid of an operating microscope by following the fiber dissection technique described by Klingler in 1960. Lateral, inferior, and medial approaches were made. The optic radiation, also known as the Gratiolet radiation, extended from the lateral geniculate body to the calcarine fissure. The average distance from the tip of the anterior Meyer loop to the calcarine sulcus was 105 mm (range 95–114 mm). The breadth of the optic radiations, one on each side of the brain, averaged 17 mm at the level of the inferior horn (range 15–18 mm). This tract could be divided into three main segments: the anterior or Meyer loop, the body, and the end of the optic radiation. Adjacent anatomical structures included: laterally, the inferior longitudinal fasciculi; medially, the tapetum of the corpus callosum; and the ependyma of the inferior horn of the lateral ventricle. Conclusions Various practical surgical approaches are discussed. The knowledge gained by studying this particular anatomy will help prevent injury to the optic radiations during neurosurgery.

✓ A case is reported of hydrocephalus due to overproduction of cerebrospinal fluid (CSF) caused by villous hypertrophy of the choroid plexus in the lateral ventricles. A 7-year-old girl with mental retardation developed gait disturbance; hydrocephalus and a Dandy-Walker cyst were detected on computerized tomography. She was initially treated with a ventriculoperitoneal shunt; however, shunting failed to control the hydrocephalus. The excessive outflow of CSF suggested choroid plexus abnormality, and magnetic resonance (MR) imaging revealed enlargement of the choroid plexus in both lateral ventricles. The patient was therefore diagnosed as having hydrocephalus induced by overproduction of CSF, which was controlled by resection of the choroid plexus. Histological examination showed the structure typical of normal choroid plexus. This is a rare case of villous hypertrophy of the choroid plexus in which MR imaging assisted in the diagnosis.

In recent years endoscopic procedures have been used more frequently to treat loculated hydrocephalus. The trapped temporal horn, a specific type of loculation, has traditionally been treated by means of ventricular shunt placement. By opening up loculations, however, this procedure can be simplified or, in some cases, even avoided. In this report the author discusses a case of trapped temporal horn that was caused by fungal meningitis and treated using endoscopically guided fenestration of the choroidal fissure, leading to clinical and radiographic resolution of the syndrome. Using this simple procedure allows the surgeon to take advantage of normal temporal horn anatomy and landmarks, avoiding the scarred and distorted region of ventricular obstruction.

Object. The goal of this study was to compare the freehand technique of catheter placement using external landmarks with the technique of using the Ghajar Guide for this procedure. The placement of a ventricular catheter can be a lifesaving procedure, and it is commonly performed by all neurosurgeons. Various methods have been described to cannulate the ventricular system, including the modified Friedman tunnel technique in which a soft polymeric tube is inserted through a burr hole. Paramore, et al., have noted that two thirds of noninfectious complications have been related to incorrect positioning of the catheter.Methods. Forty-nine consecutive patients were randomized between either freehand or Ghajar Guide—assisted catheter placement. The target was the foramen of Monro, and the course was through the anterior horn of the lateral ventricle approximately 10 cm above the nasion, 3 cm from the midline, to a depth of 5.5 cm from the inner table of the skull. In all cases, the number of passes was recorded for successful cannulation, and pre- and postplacement computerized tomography scans were obtained. Calculations were performed to determine the bicaudate index and the distance from the catheter tip to the target point.Conclusions. Successful cannulation was achieved using either technique; however, the catheters placed using the Ghajar Guide were closer to the target.

✓ The authors report on a case of solitary neurocysticercosis located in the anterior third ventricle of a 21-year-old Hispanic man who presented with progressive headache, nausea, and mental decline. The appearance of the lesion on computerized tomography and magnetic resonance studies was typical of that of a colloid cyst, which was the presumptive preoperative diagnosis. A transcortical-transventricular microsurgical approach was used, and inspection of the anterior third ventricle via the ipsilateral foramen of Monro revealed no lesion. Inspection of the floor of the ipsilateral lateral ventricle revealed the intact cyst, which had migrated since the preoperative studies had been obtained. The lesion was removed intact, and histopathological examination confirmed the diagnosis of neurocysticercosis. The authors review the radiographic findings in this case and further illustrate the potential for neurocysticercosis to masquerade as other intracranial lesions.

✓ The fiberoptic endoscope has never gained popularity among neurosurgeons although it is ideally suited for navigating within the cerebral ventricles. Recent advances in optics and miniaturization make the application of endoscopy in neurosurgery more practical. The authors report eight children who underwent ventriculoscopic fenestration of symptomatic loculated cerebrospinal fluid (CSF) collections. These CSF collections were either isolated ventricular cysts or trapped lateral ventricles secondary to obstruction at the foramen of Monro. Cyst wall dissection was carried out with a “saline torch” dissector which was introduced through a working channel in the ventriculoscope. The torch was used to coagulate vessels and to sculpt large windows in cyst walls or in the septum pellucidum. Ventriculoscope-guided cyst fenestration can be performed safely and easily under direct vision. The technique may permit simplification of shunt systems in some patients and elimination of shunts in others.

✓ Nine cases with arteriovenous malformations (AVM's) predominantly involving the lateral ventricle are presented. All the AVM's were small, but caused intraventricular hemorrhage in eight cases. Only two patients had an intracerebral hemorrhage large enough to warrant evacuation. Eight patients were under the age of 40 years at the onset of their disease. Computerized tomography demonstrated intraventricular hemorrhage in eight patients, and after intravenous administration of contrast medium a small area of enhancement with dilated subependymal draining veins was seen in seven. The lateral ventricles were of normal size in seven cases, and only two patients required a shunting procedure. Angiography demonstrated that the lesion was an AVM in eight patients, and did not visualize the lesion in the ninth. One patient suffered a recurrent intraventricular hemorrhage when the AVM was demonstrated, although repeated angiography had failed to disclose a vascular lesion at his first intraventricular hemorrhage 14 months before. All nine lesions were resected by microsurgical techniques, and the results were excellent in eight patients. Of four caudate lesions, three were resected through a frontal transcortical approach and the other was operated on through an anterior transcallosal approach; the results were excellent in three of these patients. Only one (Case 4) was left with neurological deficits; he had confusion and disorientation following a right frontal transcortical approach. Even in the dominant hemisphere, lesions in the head of the caudate nucleus could be safely resected by an anterior transcallosal approach. Two choroidal lesions located in the temporal horn and trigone on the dominant side were resected through a middle temporal gyrus approach, and three thalamic lesions through a posterior transcallosal approach, all with excellent results. In all cases the brain opening required was about the width of the retractor (maximum 2.0 cm, average 1.5 cm).

✓ The authors report a patient with bilateral papillomas of the choroid plexus of the lateral ventricles with documentation of cerebrospinal fluid (CSF) hypersecretion causing hydrocephalus. Special attention is given to the large volume of CSF produced by these tumors (removal of one tumor reduced CSF outflow by one-half) and to the fact that CSF diversion was not required after both tumors were removed. Since tumor removal alone was sufficient to stop the progression of hydrocephalus, we feel that this case supports the concept that elevated CSF production by itself is sufficient to cause hydrocephalus in patients with papillomas of the choroid plexus.

✓ Bilateral xanthogranulomas arising from both choroid plexuses were found in a 6-year-old child with epileptic seizures and psychomotor retardation. Both masses were surgically removed without adding any neurological deficits. The xanthogranulomas were fairly large, and the posterior part of both lateral ventricles were slightly dilated, but clinical symptoms and the location of the xanthogranulomas could not be clearly correlated in this case.

✓ The effectiveness of transependymal absorption of cerebrospinal fluid in hydrocephalus was studied by correlating the measured water content of feline hydrocephalic white matter with the rate of enlargement of the ventricles. Two groups of cats were subjected to opening of either the calvaria or the calvaria and dura before the intracisternal injection of kaolin to obtain two profiles of ventricular enlargement. The water content 1, 2, and 3 mm from the lateral ventricles was measured in each group using the dry/wet weight and microgravimetric techniques after sacrificing the animals in each group at 2, 3, or 6 weeks after inducing hydrocephalus. In the animals with both calvarial and dural opening, the ventricles enlarged rapidly in the first 2 to 3 weeks and then continued to increase but at a slower rate. Concomitant with this early increase of ventricular size was a progressive increase in white matter water content both adjacent to and remote from the ventricles, which continued through 6 weeks. When only the calvaria was opened, ventricular size increased gradually, but continued to increase at a constant rate throughout the 6 weeks. Water content adjacent to the ventricle did not increase until the 3rd week, with little spread to adjacent areas by the 6th week. The central canals of the spinal cord were enlarged in both groups at all sampling levels. Neither increased periventricular water nor dilatation of the central canal was associated with stabilization of ventricular size in these studies. The authors conclude that these pathways are not sufficient to arrest the hydrocephalic process in these models.

✓ Accidental death brought to autopsy a 19-year-old girl with an asymptomatic arachnoid cyst which had expanded from the region of the interpeduncular cistern so as to replace the third ventricle and extend into both lateral ventricles. Associated with this expansion was a significant degree of hydrocephalus, compression of the walls of the lateral ventricle, and obliteration of the normal structures of the floor of the third ventricle. The histological structure of the cyst wall and its relationship to the normal arachnoid are defined and found to consist of a reduplication of the normal arachnoid membrane resulting in a space within the arachnoid tissue. It is suspected but not proven that the cyst was congenital, resulting from an abnormality in development. Some suggestions are offered regarding the mechanism for its enlargement.

✓ The case history of a patient with a xanthogranuloma of the third ventricle is presented. This type of lesion formed by desquamation of epithelium is usually noted as an incidental autopsy finding in the choroid plexus of the lateral ventricles. Total removal via a transcortical transventricular route led to complete recovery. These tumors should be suspected in the geriatric population. The computerized tomography findings and a review of the literature are included.

✓ Experimental subarachnoid hemorrhage (SAH) was induced in adult rabbits by three repeated cisterna magna injections of autologous nonheparinized blood. One week after the last blood injection the animals were sacrificed and examined for morphological change. No vasculopathy was noted in the basilar arteries and no periarterial thrombus was seen around the majority of these arteries. Gross and microscopic changes were observed in both the ventricles and choroid plexus. Ventricular changes included dilation of the lateral ventricles, destruction of ciliated ependymal cells, and deposition of small amounts of blood throughout the ventricular system. These ventricular changes are similar to the pathological sequelae of SAH in patients. Choroid plexus changes included electron-dense cytoplasmic inclusions and dilation of the lateral and subcellular spaces. The ventricular surface and the choroid plexus are both affected by the intracisternal injection of blood. The hydrocephalus that follows SAH may be potentiated by ependymal disruption and loss of ciliated activity in the ventricles. Changes in choroid plexus function may also occur.