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Human embryos were studied to clarify controversies surrounding the developmental morphology of the basal ganglia and related structures. Eleven human embryos at Carnegie stages 12 through 21 were examined and reconstructed by the three-dimensional computer graphics technique. Findings on the neural morphology and telencephalic arteries reveal that (1) all parts of the basal ganglia and the amygdala are telencephalic structures; (2) the medial part of globus pallidus, preoptic area and medial septal nucleus originate from the medial ganglionic eminence; (3) the olfactory bulb, prepiriform area, caudate head, caudate body, caudate tail, nucleus accumben septi, putamen, lateral part of globus pallidus and the amygdala originate from the lateral gangiionic eminence.

"Dizziness" includes dizziness, vertigo, ataxia and psychogenic unsteadiness and is the second most common symptom next to pain. The diagnosis and treatment of dizziness is discussed, together with a discussion to differentiate life-threatening dizziness from non-life-threatening dizziness. A complaint of dizziness may be more serious than a complaint of vertigo, and danger signs include markedly dilated pupils. Dizziness with abnormal vital signs and with neurological and/or neuro-ophthalmological symptoms may indicate that the patient is in a very serious condition. Neurological therapy for dizziness includes tPA, Heparin, anticoagulants for CVA related dizziness, anti-Parkinsonism therapy for Parkinsonism related dizziness. In this report therapy for migraine without Ergotamine alkaloid for dizziness of brainstem migraine is discussed, together with therapy for cervical dizziness.

Objective To evaluate a contralateral approach to aneurysms located in the internal carotid artery cave and proximal C4 segments. Methods In six adult cadaveric head sides, proposed aneurysms in the carotid cave or proximal C4 segments were approached via contralateral craniotomies. We summarize the approach in the following steps: 1) frontotemporal orbital craniotomy, 2) drilling of the lateral sphenoid wing and opening of the dura along the frontotemporal base, 3) drilling of the planum sphenoidale and the tuberculum sellae more extensively toward the aneurysm side and opening of the sphenoid sinus, 4) drilling of the medial part of the anterior clinoid process on the side of the aneurysm and removal of the superior, medial, and inferior walls of the optic canal, 5) opening of the optic sleeve, and 6) opening of the space between the medial wall of the internal carotid artery C2-C3 segments and the lateral edge of the pituitary gland. Results The contralateral approach to expose the opposite internal carotid artery cave and proximal C4 segments provided excellent views of the region, without mobilization or retraction of either the optic nerve or the carotid artery. Conclusion We recommend that this approach be used only for selected aneurysms, which are small and directed medially, anteriorly, or inferiorly, in the defined locations.

Here we clone the human homologue of TBPIP [Tat binding protein 1(TBP-1)-interacting protein]. TBPIP is a molecule that has been cloned from mouse as a cofactor of TBP-1. Eighty-eight per cent of the deduced amino acid sequence of human TBPIP coincides with that of mouse TBPIP. CAT assay reveals that human TBPIP could interact with human TBP-1, then enhance the function of TBP-1 on HIV (human immunodeficiency virus)-Tat-mediated transactivation. Our radiation hybrid mapping indicates that TBPIP is located on chromosome 17q12–21. A DNA database search uncovers that an apparent part of TBPIP has been obtained as a BRCA1 locus-related gene (OV-4) and mapped onto chromosome 17q12–21. Interestingly, the nucleotide structure of human TBPIP is very similar to that of the GT198 gene, which has been cloned from a human breast cancer cell line and also mapped onto the BRCA1 locus. Since a very high rate of gene mutation is observed in the BRCA1-related region in breast cancers and expression of authentic GT198 mRNA could not be confirmed in either BT-474 (other kind of human breast cancer cell line) or normal human testis (where the strong expression of GT198 mRNA is reported), it is likely that GT198 is a mutated form of human TBPIP.

To evaluate the surgical approach and clipping of aneurysms located at the carotid cave region.Between 1980 and 1998 we have adopted the well known ipsilateral approach for exposure and securing of carotid cave aneurysms. In four patients, we had the opportunity to use a contralateral approach to carotid cave aneurysms, with easier dissection and application of a simple aneurysmal clip. The visual acuity of the patients did not deteriorate from the pre-operative level.Aneurysms located at the carotid cave region may be approached easily and safely through a contralateral craniotomy with application of the aneurysm clip from an angle medial and inferior to the optic nerve.

Objective : To establish a simple method of determining the appropriate stimulus intensity for studying the dipole moment in somatosensory evoked fields. Methods : In 17 patients (20 hemispheres), the authors studied the relationship between the dipole moment and stimulus intensity, which was quantified using the threshold of thenar muscle twitch (TMT). The dipole moment was measured at 1.0, 1.5 and 2.0 TMT. Two measurements were obtained at 1.5 TMT to determine the procedure's margin of error. Results : There was no significant difference between the dipole moments measured at 1.5 and 2.0 TMT. Conclusions : Setting the stimulus intensity at 1.5 TMT or more ensures a consistent response.

In order to treat syringomyelia associated with adult type Chiari malformation, the authors developed a method of expansive suboccipital cranioplasty (ESC) that involves enlarging the small posterior fossa to obtain a sufficient flow of cerebrospinal fluid (CSF). The relative effectiveness of ESC with the obex plugged and not plugged was also examined, as well as other factors influencing the operative results. Twenty patients without arachnoid adhesion at the major cistern underwent ESC without opening the arachnoid membrane at the major cistern. After surgery, all improved with no recurrence and CSF flow study using magnetic resonance (MR) imaging showed significant improvement of the flow at the major cistern. Another 20 patients without arachnoid adhesion also underwent ESC but with obex plugging. Sixteen improved and one displayed only temporary improvement with recurrent syringomyelia due to postoperative arachnoid adhesions. The remaining three showed no change in spite of shrinkage of the syrinx on postoperative MR imaging. These three patients had displayed pre-operative symptoms over an approximately 10-year period involving almost the entire axial plain of the spinal cord, and presented a large syrinx before surgery. In 4 patients with arachnoid adhesions, all required intra-arachnoid procedures in addition to ESC. Intra-arachnoid procedures are not necessary to facilitate restoration of CSF flow in patients without arachnoid adhesions, because ESC can release the CSF flow blockage in the major cistern even without plugging of the obex. An associated arachnoid adhesion at the major cistern or a long-standing syringomyelia with irreversible damage of the spinal cord results in a poor operative prognosis. When posterior fossa surgery fails, insufficient decompression or postoperative arachnoid adhesions at the major cistern as the cause of treatment's failure should be evaluated by CSF flow studies using phase contrast MR imaging.

✓ The treatment of spinal intramedullary arteriovenous malformations (AVMs) with a diffuse-type nidus that contains a neural element poses different challenges compared with a glomus-type nidus. The surgical elimination of such lesions involves the risk of spinal cord ischemia that results from coagulation of the feeding artery that, at the same time, supplies cord parenchyma. However, based on evaluation of the risks involved in performing embolization, together with the frequent occurrence of reperfusion, which necessitates frequent reembolization, the authors consider surgery to be a one-stage solution to a disease that otherwise has a very poor prognosis. Magnetic resonance (MR) imaging revealed diffuse-type intramedullary AVMs in the cervical spinal cords of three patients who subsequently underwent surgery via the posterior approach. The AVM was supplied by the anterior spinal artery in one case and by both the anterior and posterior spinal arteries in the other two cases. In all three cases, a posterior median myelotomy was performed up to the vicinity of the anterior median fissure that divided the spinal cord together with the nidus, and the feeding artery was coagulated and severed at its origin from the anterior spinal artery. In the two cases in which the posterior spinal artery fed the AVM, the feeding artery was coagulated on the dorsal surface of the spinal cord. Neurological outcome improved in one patient and deteriorated slightly to mildly in the other two patients. Postoperative angiography demonstrated complete disappearance of the AVM in all cases. Because of the extremely poor prognosis of patients with spinal intramedullary AVMs, this surgical technique for the treatment of diffuse-type AVMs provides acceptable operative outcome. Surgical intervention should be considered when managing a patient with a diffuse-type intramedullary AVM in the cervical spinal cord.

Surgical outcome of intramedullary spinal cord ependymoma was investigated in order to define the treatment strategy. We have operated on 18 cases of intramedullary spinal cord ependymoma based on the principle of radical resection. The follow-up periods ranged from 10 months to 249 months with an average of 86.2 months. Postoperative neurological status in the long follow-up periods was compared to the pre-operative status and was correlated with the histological grade of malignancy. Total removal of the tumour was achieved in 17 cases, and subtotal removal followed by radiation therapy was conducted in 1 case. There was neither surgical mortality nor radiological evidence of recurrence in the long-term follow-up periods. The final outcome of the neurological condition was improved in 1 case, unchanged in 15 cases (including a case of subtotal removal) and deteriorated in 2 cases. The deterioration was in the form of gait disturbance due to the worsening of proprioception in 2 cases and dysaethesia in 1 case. Histological examination showed no evidence of anaplasia in 6 cases, evidence of early anaplasia in 10 cases, and moderate evidence of anaplasia in 2 cases. No relationship between the histological malignancy and clinical course was found. Intramedullary spinal cord ependymoma should be removed radically as early as possible while taking great care to avoid posterior column injury. Histologically malignant ependymoma might be a clinical exception.

Object. Cavernous sinus cavernomas are rare lesions associated with high rates of intraoperative mortality and morbidity resulting from profuse bleeding. In this paper, the authors report their experience in treating five patients with histologically confirmed cavernous sinus cavernomas and describe the efficacy of induced hypotension in facilitating excision of the lesion.Methods. All five patients were women ranging in age from 25 to 54 years, with an average age of 42 years. The mass was small in one and large (> 3 cm in diameter) in four. In one patient with a large mass, cardiac arrest occurred after the craniotomy, and remarkable reduction in the size of the cavernoma was evident on postmortem examination. The other three large lesions were successfully removed piecemeal after induction of hypotension (60–80 mm Hg systolic pressure), which remarkably reduced the mass and the bleeding during surgery. In the remaining patient, who had a small lesion, the cavernoma was removed in one piece.Conclusions. Cavernous sinus cavernoma can be thought of as a cluster of sinusoidal cavities, the size of which varies depending on the systemic blood pressure. During surgery, reduction of the mass and control of bleeding from the cavernoma can be achieved by inducing hypotension, which enables the safe excision of this lesion. This technique should be considered by surgeons resecting a cavernous sinus tumor, especially when cavernoma is suspected.

The extended middle fossa approach with an oticocondylar osteotomy is more extensive than the anterior transpetrosal approach. The mandibular head is dislocated anterointeriory after transection of the mandibular neck, and the external auditory meatus is unroofed. By these two procedures, the middle fossa can be exposed widely with minimal brain retraction. Regions accessible with this approach include the suprasellar, petroclival, clival region from the posterior clinoid process down to the jugular tuberculum and the infratemporal region from the pterygoic fossa to the jugular foramen. Precise approximation of the transected mandibular neck with a titanium miniplate allows normal function of the temporomandibular joint. This approach can be used alone or in combination with the orbitozygomatic approach or the presigmoidal transpetrosal approach. This approach was used for 56 lesions, including 23 meningiomas, 8 craniopharyngiornas, 6 chordomas or chondrosarcomas, 4 trigeminal neurinomas, and other lesions. Malocclusion of the mouth resulting from reconstruction failure on mandibulotomy in the initial two cases and transient facial palsy resulting from retraction of the nerve during exposure of the mandibular neck in three cases were complications of this surgery. The extended middle fossa approach thus allows wide exposure of central and middle skull base lesions avoiding undue injury to the temporal region.

A 66-year-old female developed exophthalmos, impaired visual acuity (perception of light), and diplopia one day after sudden onset of headache. Neurological examination revealed proptosis, chemosis, impaired vision, and ophthalmoplegia. Carotid angiography showed direct carotid-cavernous sinus fistula concomitant with an intracavernous aneurysm on the right side. Intraaneurysmal embolization using the Guglielmi detachable coils (GDCs) via the transarterial route was performed and complete occlusion of the fistula successfully achieved. The neurological deficits resolved completely by 6 months after embolization. Intraaneurysmal GDC embolization via the transarterial route may be an alternative for the treatment of direct carotid-cavernous sinus fistula due to rupture of intracavernous aneurysm.

PET with L-methyl-11C-methionine (Met-PET) is a useful tool for differentiating cerebral tumor from normal brain tissue, but some observations showed a high accumulation of methionine in non-tumorous lesions.We evaluated whether Met-PET was clinically useful in distinguishing tumor from non-tumor in intracranial lesions. We investigated 50 cases of brain lesions. We had four non-tumorous lesions with an accumulation (false positive) and five tumorous lesions with no accumulation (false negative) in Met-PET. It should be kept in mind that there is a possibility of tumorous or non tumorous lesions in the presence of a low or high accumulation of methionine.

We report the skull radiograph, CT and MRI findings in three patients with lymphocytic adenohypophysitis mimicking pituitary adenoma. All cases were associated with pregnancy. CT demonstrated a pituitary mass but did not differentiate lymphocytic adenohypophysitis from pituitary adenoma. The skull radiographs showed either a normal sella turcica or minimal abnormalities; they did not show ballooning or destruction. The MRI appearances were distinctive: relatively low signal on T1-weighted images; preservation of the bright posterior pituitary lobe despite the presence of a relatively large pituitary mass, less common in macroadenomas; marked contrast enhancement compared with pituitary macroadenomas; and dural enhancement adjacent to a pituitary mass.

Background In patients with malignant glioma, neuroimaging studies cannot identify the true tumor margins, and tumor disappearance on neuroimaging studies does not necessarily indicate histologic disappearance of the tumor.

We investigated the characteristic features of intramedullary spinal cord tumour associated with neurofibromatosis type 1 (NF-1). We have experienced 44 cases of pathologically confirmed intramedullary spinal cord tumour. Diagnosis of NF-1 was done according to the criteria set by the National Institute of Health Consensus Development Conference. Within the described population NF-1 was diagnosed in two patients. Both the patients were male and histopathologically the tumours were anaplastic astrocytoma and glioblastoma multiforme respectively. 6 cases of NF-1 associated with intramedullary spinal cord tumour based on the above diagnostic criteria have so far been reported, including our 2 cases. Of these 6 cases, 5 were male and in one sex was not described. The tumour was an astrocytoma in all 6 cases. This finding suggested that intramedullary spinal cord tumour associated with NF-1 tends to occur predominantly in males and that histopathologically the tumour is likely to be an astrocytoma. We conclude that the criteria proposed by the National Institute of Health Consensus Development Conference are contributory in making an accurate pre-operative pathological diagnosis of intramedullary spinal cord tumour associated with NF-1.

To improve cerebral hypoperfusion in the ischemic type of Moyamoya disease, we have applied superficial temporal artery–middle cerebral artery (STA–MCA) double anastomoses in combination with encephalo-myo-synangiosis (EMS) for 19 hemispheres of 10 children (age from 5 to 11 years at surgery). Two branches of the STA were anastomosed to the two cortical arteries which were selected in the watershed area of the cerebral hemisphere estimated as a hypoperfusion area on the preoperative angiograms. Before surgery transient ischemic attacks (TIAs) developed from every month to every 6 months in association with hyperventilation or sobbing. No perioperative completed stroke or wound complications was observed, although single TIA developed in four patients within 1 month after surgery. Postoperative angiogram demonstrated that, not only the preoperative watershed area, but also the most of the middle cerebral artery territory was oppacified via the 2 branches of the STA in all 19 hemispheres. In a mean follow-up period of 4 years, no ischemic episode was induced by hyperventilation, and there was no mental or neurological deterioration. STA–MCA double anastomoses, to the cerebral watershed area, in combination with EMS are safe and effective even for younger children with Moyamoya disease.

In classic human embryology, one of the most important techniques to observe embryonic structures three-dimensionally (3-D) was to reconstruct embryos or their parts using wax plate models from serial histological sections. However, wax plate reconstruction does not allow observation of internal structures and lumens unless the models are cut after reconstruction. The development of computer graphics has enabled us to reconstruct various biologic structures on the viewing screen and to manipulate the computer images as freely as we desire. Nevertheless, until now computer reconstruction has not been used frequently to study human organogenesis. We reviewed and photographed serial histological sections of early human embryos, projected these photographed slides onto a screen and traced the outlines of specific structures under study on a digitizing pad that was interfaced with a 16 bit computer. The digitized images were combined using a software for 3-D reconstruction. With this technique, we were able to visualize the anatomical localization and interrelation of various structures inside the human head during the embryonic period. The 3-D reconstruction technique should be of potential use for the study of normal and abnormal morphogenesis.

The gravimetric method to determine the tissue water content is widely used for studying brain edema because the tissue water content can be calculated from only the density of the wet tissue using a gradient column. This method has been used in only a few studies of cerebellar water content. We estimated the water content of the cerebellar cortex by the gravimetric method and compared the results with those measured by the conventional drying-weighing method, and found a significant difference. We therefore propose modified coefficients for the equation for the water content of the cerebellar cortex as follows: % tissue water content = 456.13(1/wet tissue density) - 356.13 This equation and the drying-weighing method were used to investigate normal and edematous cerebellar cortices after compression with an epidural balloon. The modified equation provided results consistent with the drying-weighing method. Differences in the total experimental system including the breed and pre-experimental condition of the cats may be factors in variations in measured values. We recommend that investigators establish equation coefficients valid for individual experimental systems.

To understand the anatomy and the surgical approaches to the petrous, 19 adult human skulls (38 specimens) were studied. The foramen spinosum, groove for greater petrosal nerve, superior and posterior margins of the internal auditory meatus, fissure for the endolymphatic sac, and anterior margin of the groove for sigmoid sinus were the constant, easily identifiable bony landmarks located strategically; they served as guides during the transpetrosal approach. Measurements between various points helped both to understand the local anatomy better and to decide the degree and direction of safe bony removal during transpetrosal surgery.

We report a 20-month-old girl with an unruptured aneurysm of the middle cerebral artery. The initial sign was complex partial seizures. Magnetic resonance angiography showed an aneurysm of the right middle cerebral artery. Cerebral angiography confirmed the presence of a saccular aneurysm. After 3 months, the aneurysm spontaneously thrombosed without neurological deficit. The seizures were controlled by anti-convulsants. The aneurysm was probably near the focus of the complex partial seizures. This is a rare case of a childhood cerebral artery aneurysm that first manifested itself by complex partial seizures.

✓ A young woman with a fourth ventricular ependymoma underwent radiotherapy following tumor excision. Twenty months later she developed a progressive neurological deficit at the C-2 vertebral level. Gadolinium-enhanced magnetic resonance imaging, showed an intramedullary lesion at the C-2 level. Although radiation myelopathy was suspected, tumor recurrence could not be excluded. Re-exploration and histopathology both confirmed a diagnosis of radiation myelopathy. A retrospective review of the case indicated findings favoring radiation myelopathy. The pertinent literature is reviewed and the findings discussed.

An unusual case of a giant prolactinoma extending to the nasopharynx and nasal cavity is presented. A 35-year-old man admitted for nasal obstruction and visual disturbances was found to have bilateral anosmia, right homonymous hemianopsia, and a right hemiparesis. The serum prolactin level was 13,300 ng/mL. Radiological examination revealed a large mass invading the skull base and extending into the suprasellar region and the left frontal lobe superiorly and into the nasopharynx inferiorly. Subtotal removal was done through a bilateral orbitofrontal craniotomy, which was followed by radiotherapy and bromocriptine administration. Immunohistochemical analysis confirmed a prolactinoma. The rarity of such a tumor, its location and extension, and the usefulness of magnetic resonance imaging and immunohistochemistry are stressed. Pertinent literature is reviewed.

The authors present two patients with subarachnoid hemorrhage caused by ruptured intracranial saccular aneurysms of the persistent primitive hypoglossal artery. A standard unilateral suboccipital approach in one patient resulted in incomplete neck clipping since the operative field was restricted by a protruding jugular tubercle. Successful aneurysmal neck clipping was achieved in the second patient via a unilateral-transcondylar-suboccipital approach with resection of the jugular tubercle and rim of the foramen magnum.

Craniotomy repair with newly designed titanium miniplates is described. The miniplates, made of malleable titanium, include burr hole covers and kerf covers for use over the craniotomy line. The plates are easily contoured by hand and have been successfully placed in 39 cases with no incidence of infection and no cosmetic problems.

We reviewed the MRI of seven patients with syringomyelia associated with surgically proven adhesive spinal arachnoiditis to describe clinical and MRI findings in this condition. Using 0.5, 1.0 or 1.5 tesla units, we obtained sagittal T1- and T2-weighted spin-echo and axial T1-weighted images. Additional sagittal T2-weighted images were obtained without using motion-artefact suppression. Contrast medium was given intravenously to five patients. The syrinx cavities were thoracic in five cases, cervicothoracic in one, and extended from C4 to L1 in one. No Chiari malformation or craniovertebral junction anomaly was demonstrated. Meningeal thickening was seen on T2-weighted sagittal images only in one case. Cord deformity due to adhesion or displacement due to an associated arachnoid cyst was seen in all cases best demonstrated on axial images. Focal blurring of the syrinx wall on axial images was seen in six patients. Flow voids were seen in the syrinx fluid in all cases on T2-weighted images obtained without motion-artefact suppression. No abnormal contrast enhancement was demonstrated.

The authors describe a new surgical technique to minimise the postoperative recurrence of adhesion after microlysis of adhesion to treat syringomyelia associated with spinal adhesive arachnoiditis. A 47 year old male presented with numbness of the lower extremities and urinary disturbance and was demonstrated to have a case of syringomyelia from C1 to T2 which was thought to be secondary to adhesive spinal arachnoiditis related to a history of tuberculous meningitis. Following meticulous microlysis of the adhesions, maximal expansion of a blocked subarachnoid space was performed by expansive duraplasty with a Gore-Tex surgical membrane, expansive laminoplasty and multiple tenting sutures of the Gore-Tex graft. Postoperatively, the syringomyelia had be en completely obliterated and improvement of the symptoms had been also achieved. The technique described may contribute to improvement of the surgical outcome following arachnoid dissection by maintaining continuity of the reconstructed subarachnoid space.

Mouse newborns find their mother’s nipples and suckle milk by themselves. It has been argued which sense organ they use when locating their mother’s nipples to suckle milk. Olfactory or tactile sensory systems are primary candidates. In the present study, we investigated the trigeminal-whisker sensory and olfactory systems in genetic arhinencephaly mouse embryos (Pdn/Pdn). Pdn/Pdn newborns do not suckle milk and die within 1 day after birth. Dysfunction of nipple-searching behavior was clear in Pdn/Pdn newborns. Pdn/Pdn newborns had a complete developmental failure in the olfactory nerve projection to the central nervous system and no olfactory bulb architecture. The trigeminal-whisker system was intact in this strain. From the results of these experiments, it was suggested that the olfactory system is essential for nipple-searching behavior and suckling milk and that the trigeminal-whisker system is not able to substitute for the lack of olfactory input in mouse newborns.

A patient developed delayed facial nerve palsy at the level of House-Brackmann grade I to grade III 10 days after vestibular schwannoma surgery by the suboccipital transmeatal approach. The palsy had completely recovered after one month. Immunological study showed reactivation of herpes simplex and magnetic resonance (MR) imaging demonstrated an abnormal enhancement pattern of the facial nerve; intense enhancement of the distal intracanalicular segment and labyrinthine segment, similar to the MR findings for Bell's palsy. A prospective control study on the enhancement pattern of the functionally preserved facial nerve after vestibular schwannoma surgery in six cases showed a similar pattern to that of the normal facial nerve. Based on these findings, we propose the hypothesis that herpes simplex reactivation is an underlying cause of delayed facial palsy after vestibular schwannoma surgery.

Object. In this paper the authors report on sigmoid sinus occlusion as a surgical complication in seven of 143 operations in which a presigmoidal—transpetrosal approach was used. Methods. Five patients (Cases 1–5) developed occlusion within 40 days after surgery, and in the remaining two (Cases 6 and 7) occlusion was detected 5.4 and 6.4 years postsurgery by means of cerebral venography, which was performed in 40 of the remaining 138 patients. Of the two patients with occlusion of the hypoplastic transverse sinus, one (Case 1) did not develop symptoms and the other (Case 2) developed brain edema with transient aphasia. Of the three patients suffering from occlusion of the dominant sigmoid sinus, one (Case 3) developed severe intracerebral hemorrhages and had a poor prognosis; one (Case 4) developed profuse supra- and infratentorial brain edema with consciousness disturbance; and the other (Case 5) developed hemorrhagic infarction in the temporal lobe accompanied by aphasia. Two patients whose sinus occlusion was detected later (Cases 6 and 7) did not develop symptoms and displayed well-communicated transverse sinuses. In Case 7, a dural arteriovenous malformation formed at the site of the sinus occlusion. Laceration of the sigmoid sinus was suspected as the cause of occlusion in Cases 2, 3, and 7; compression of the sinus in Cases 5 and 6, sinus laceration and postoperative dehydration in Case 4; and laceration and compression of the sinus in Case 1. Conclusions. Differences in the clinical course among these patients were attributed to anatomical variations in the venous system. Occlusion of the sigmoid sinus should be weighed as a potential complication when selecting candidates for the presigmoidal—transpetrosal approach.