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Objective: Monitoring of the oculomotor system during cranial base or brainstem surgery requires extraocular intraorbital insertion of electromyography electrodes. We investigated the use of image-guidance technology for anatomically correct intraorbital electrode placement., Methods: For neuronavigation, an optical tracking system was used in a standard fashion. Needle electrodes were inserted percutaneously into the lateral rectus, inferior rectus, and superior oblique muscle along the axis of a hand-held pointer or by means of an electrode applicator to allow direct tracking with the navigation system. Electromyographic monitoring was performed by multichannel recordings of free running or evoked activity from the selected muscles., Results: We have used this method in 10 patients; 5 had cranial base tumors and 5 underwent operations for brainstem lesions. No additional instruments or resources were required compared with the routine setup, and no intraorbital structures were injured. Successful monitoring of oculomotor, trochlear, or abducent nerve function was possible in each case., Conclusion: This method may have the potential to increase the safety and success rate of intraoperative electro-ophthalmography during microsurgery focused on preservation of neurological function.

The aim of this study was to demonstrate that silent periods of the mentalis muscle are induced after facial nerve stimulation and cutaneous stimulation in normal subjects. When the marginal mandibular branch of the facial nerve and the cutaneous nerve in areas adjacent to the lower lip were stimulated during slight voluntary contraction of the mentalis muscle, silent periods were elicited with surface electrodes on the mentalis muscle. The early phase and the late phase of the silent period were elicited by marginal mandibular branch stimulation. The early phase of the silent period was recognized following the F waves and it disappeared at 36.3 msec. The average duration of the late phase of the silent period was 59.2 msec, with an average latency of 62.5 msec. Only the late phase of the silent period after cutaneous stimulation could be elicited, with a duration and latency of 55.9 msec and 54.0 msec respectively. The authors conclude that the silent period is able to be elicited in the mentalis muscle by peripheral nerve stimulation, and is one of the late responses in facial muscles.

Today, endoscopic third ventriculostomy is an established operative modality in occlusive hydrocephalus. The elemental step in third ventriculostomy is the perforation of the floor of the third ventricle. Especially with a thickened third ventricular floor, anatomical orientation can be disturbed and perforation of third ventricular floor technically difficult. The combination of a neuronavigation system with an endoscope provides interactive image-guided neuroendoscopy. Exact planning of the approach is thus possible and the ideal trajectory to the target area can be determined. We have combined interactive neuronavigation and intraoperative fluoroscopy for incorporating real-time feedback to optimize endoscopy in patients with a thickened third ventricular floor selected for third ventriculostomy.

Recently, the use of intra-operative image guidance has gained an increasing role in neurosurgery for both spinal and cerebral interventions. Some modern neuronavigation systems are able to register any surgical instrument and create a virtual pointer. A virtual elongation of the digitized instrument is frequently used for neuroendoscopic procedures and spinal instrumentation. The instrument is equipped with a universal instrument adapter clamp and digitized by touching the tip of the instrument into a calibration cone. An algorithm calculates the vector of the instrument using two points: the tip of the instrument, and the geometrical center of the instrument adapter geometry. If a virtual elongation of the calibrated instrument is performed, the neuronavigation software may calculate an incorrect virtual target point. We developed an instrument calibration matrix (ICM) that automatically calibrates the correct vector, tip, and diameter of the instrument used for image-guided surgery. The ICM is easy to handle and does not cause a time delay during surgery. Virtual elongation of the surgical instruments shows correct anatomic data, which are fundamental for planning ventricular tapping and spinal screw placement in particular. The instrument calibration matrix is essential if surgical instruments are digitized and used for neuronavigation. It helps to avoid mis-planning of surgical vectors and mis-placement of the used instruments.

Object: To date, both arteriovenous malformations (AVMs) and cavernomas have been considered to be congenital malformations. A recent survey of the literature has shown the potential for de novo generation of both familial and sporadic cavernomas as well as AVMs. Therefore, it was of interest to determine the biological behavior of these lesions in detail., Methods: The proliferative and angiogenic capacities of the endothelium of 13 cavernomas and 25 AVMs obtained in patients recently treated (1997-1998) at one institution were studied. Immunohistochemical staining for proliferating cell nuclear antigen (PCNA), MIB-1, and vascular endothelial growth factor (VEGF) and its receptor Flk-1 was performed using standard staining procedures. Positive immunostaining of the nuclei of endothelial cells was observed in specimens of both AVMs and cavernomas for PCNA (80% of AVMs and 85% of cavernomas), and Flk-1 (80% of AVMs and 31% of cavernomas). Endothelial expression of VEGF in the 18 incompletely embolized AVMs was found in 72% of cases but only in 28% of the seven cases in which patients did not undergo endovascular treatment: it was found in 38% of cavernomas. Endothelial expression of MIB-1 was found in 12% of AVMs but in no cavernomas., Conclusions: These results indicate that there is endothelial proliferation as well as neoangiogenesis in cerebral cavernomas and AVMs. The increased level of angiogenesis in only partially obliterated AVMs underscores the need for radical and complete occlusion of cerebral AVMs to avoid recurrences and further risks of morbidity.

We investigated the angiogenetic and proliferative activity of the endothelium of 30 consecutive surgical cases of AVM treated at our institution by immunohistochemical detection of the PCNA, MIB-1, Flk-1 and VEGF antibodies. Endothelial positive immunostaining was observed in 87% of the cases for PCNA, in 20% for MIB-1, and in 80% for Flk-1. Of 22 individuals treated with incomplete embolization prior to surgery, 17 showed an expression of VEGF (77%), but only two of the eight patients (25%) who were treated without prior embolization exhibited such an immunoreaction (P=0.0086). The proliferation and growth of cerebral AVMs is documented by endothelial expression of PCNA and MIB-1. The statistically significantly higher expression of VEGF in partially obliterated (embolized) AVMs is most likely caused by transient regional hypoxia within the AVM nidus that mediates neoangiogensis. It points out the clinical relevance of a complete occlusion in order to avoid neovascularization associated with subsequent morbidity and mortality.

Advances in computer technology have permitted virtual reality images of the ventricular system. To determine the relevance of these images we have compared virtual reality simulations of the ventricular system with endoscopic findings in three patients. The virtual fly-through can be simulated after definition of waypoints. Flight objects of interest can be viewed from all sides. Important drawbacks are that filigree structures may be missed and blood vessels cannot be distinguished clearly. However, virtual endoscopy can presently be used as a planning tool or for training and has future potential for neurosurgery.

Objects: Intradural perimedullary spinal arteriovenous fistula (AVF) is a synonym for type IV spinal arteriovenous malformation (AVM). It is an important clinical differential diagnosis in all patients with slowly progressive or acute spinal symptoms. Perimedullary AVFs are rare in the paediatric age group. We report the treatment regimen and the clinico-radiological findings for these malformations at our institution., Methods: Of four paediatric patients, three individuals with persistent fistulas after endovascular treatment were operated on. The malformations were obliterated completely in all patients without any morbidity. In three patients previously documented neurological symptoms resolved during follow-up., Conclusions: If slowly progressive or acute radicular or medullary symptoms arise in children, a spinal arteriovenous malformation should be ruled out by MRI. A combined endovascular and surgical treatment of paediatric spinal AVM type IV (perimedullary AVFs) carries a low risk of morbidity and is reasonably effective.

Short latency response (SLR), middle latency response and long latency response (LLR) are elicited in facial muscles by transcranial magnetic stimulation. Although it has been said that the LLRs are elicited by the trigeminal nerve stimulation, a trigeminofacial reflex is recorded easily in normal subjects by the electrical stimulation in orbicularis oculi muscles as a blind reflex, but a trigeminal-facial reflex recorded in orbicularis oris, namely a snout reflex, is more difficult to record in normal subjects. The aim of this study is to demonstrate the LLR of lower facial muscles (mentalis muscle) by the transcranial magnetic stimulation, using a circular coil. The transcranial magnetic stimulations were performed over parieto-occipital scalp with frequencies of random and 0.3 Hz in 11 normal subjects and the responses in the mentalis muscle were recorded. The LLR of the mentalis muscle was recorded in all 11 subjects following SLRs. The latency, duration and LLR/SLR ratio were 37.4 msec, 20.3 msec and 9.1%, respectively. The waveform of the LLR varied trial to trial showing habituation with a stimulation of 0.3 Hz. At this time the LLR of the masseter muscle was not recorded following this transmagnetic stimulation. It was suggested that the LLR of the mentalis muscle is recorded by the transcranial magnetic stimulation of the trigeminal nerve with a circular coil. The ease and reliability of their recording make it possible to apply this LLR clinically as well as a blink reflex.

Sympathetic storm phenomena are well known therapeutic problems in patients with severe brain injury. We have treated four patients with intrathecal baclofen (ITB) who suffered from severe hypertension, tachycardia and other sympathetic storm phenomena after different primary events. In all patients conventional therapy with sedatives and antiadrenergic medication had been taken to the upper limits before initiating ITB. Autonomic dysfunction immediately improved in three of four patients. In all patients ITB, via lumbar or ventricular route, proved safe and without complications. The anatomical and pharmacological basis of the GABA-B agonist action on such sympathetic storm phenomena are not yet fully understood. However, the positive results observed in three out of four patients are promising and require further investigation. ITB is a new therapeutic approach to control otherwise unresponsive sympathetic storm phenomena in severe brain injury., (Copyright 2000 Harcourt Publishers Ltd.)

Background: Tumors of the skull base frequently encase or extend into normal neural and vascular structures. Preoperative planning and intraoperative identification of anatomic landmarks is especially important in complex tumors since it helps avoid or minimize surgical morbidity., Methods: By creating a surgical plan the image guidance software offers help in the establishment of a surgical approach. During surgery, the neuronavigation system displays the location of anatomic landmarks of the skull base regardless of any erosion or displacement., Results: A series of 10 patients with complex tumors in various skull base locations is reported. Osseous structures are easily identified using the CT-based image guidance since these landmarks do not shift due to CSF loss. Image fusion of CT and MRI data gives additional information on the displacement of soft tissue structures. Image fusion in a substraction mode is helpful when a tumor has invaded bony structures or when the encasement of major vessels has to be visualized., Conclusion: The preoperative data preparation (planning of the approach, image fusion) plays a vital role in modern neuronavigation and contributes useful information during surgery for complex skull base tumors. Such advanced neuronavigation increases the efficacy and safety of intraoperative maneuvers. Eroded and distorted anatomic landmarks are not subject to a significant amount of intraoperative shift throughout the surgical procedure.

An association between hyperglycemia and outcome in spontaneous subarachnoid hemorrhage (SAH) has been sporadically reported. Our hypothesis was that hyperglycemia is a sign of central metabolic disturbance linked with specific appearances on computerized tomography (CT) scans reflecting different degrees of corresponding brain injury. The admission plasma glucose level, initial CT findings, and outcome after 6 months were analysed in a cohort of 99 patients with SAH in Hunt & Hess Grade IV or V. The CT scans were quantitatively assessed for subarachnoid blood, intracerebral hematoma, intraventricular hemorrhage, hydrocephalus, midline shift and compression of the perimesencephalic cisterns. These findings were combined to determine a three-point CT severity score. All patients showed elevated (>5.8 mmol/l) plasma glucose levels on admission. Mortality among 33 patients with glucose concentration below 9.0 mmol/l was 33.3%, 71.1% for the 45 patients with glucose level between 9.0 and 13.0 mmol/l, and 95.2% for the 21 patients with concentration above 13.0 mmol/l (P<0.0001). Glucose level was higher in Grade V than in Grade IV patients (mean+/-SD) (11.8+/-3.2 vs 9.8+/-2.9 mmol/l; P=0.0012). Patients with mild CT findings (n=10) had the lowest glucose level (8.9+/-1.8 mmol/l; P=0.0082), whereas patients with severe findings (n=56) had the highest glucose (11.4+/-3.5 mmol/l; P=0.011). Despite association with clinical grade and extent of CT findings, logistic multiple regression revealed the admission plasma glucose level to be an independent prognosticator of outcome. The prognostic potential of the initial plasma glucose level may be beneficial in management protocols of poor-grade SAH patients.

Aneurysms of the posterior cerebral artery (PCA) are rare and imply a variety of treatment modalities. We present a case of an incidental, nonruptured posterior cerebral artery aneurysm, which was successfully occluded by coil embolization after a bypass between the occipital artery and the distal posterior cerebral artery was created. MR imaging in a neurologically normal 26-year-old man, performed in the course of a work-up for nonrelated symptoms, incidentally revealed a partially thrombosed and calcified aneurysm of the left posterior cerebral artery (P2 segment). This was confirmed by angiography. Due to aneurysm configuration and localization in the asymptomatic patient, primary clipping or endovascular occlusion was considered to be too hazardous. Four weeks after successful microvascular connection of the left occipital artery to the distal posterior cerebral artery, the PCA was occluded at the level of the aneurysm with a detachable coil. The patient remained asymptomatic, without visual field defects. The above presented combined microvascular (bypass) and endovascular (coil embolization) treatment with excellent result should be considered as alternative in patients with nonruptured, asymptomatic P2 aneurysms, which are high risk for primary clipping or endovascular occlusion.

The effectiveness of intrathecal opioid therapy when applied to different pain mechanisms, in particular neuropathic and nociceptive pain conditions, was studied retrospectively in 43 patients suffering from cancer pain. On the basis of clinical and radiological data, the pain mechanisms were categorized as nociceptive (n = 23) and neuropathic (n = 20). The average duration of treatment of nociceptive pain was 5 months, of neuropathic pain only 2.5 months. The initial median reduction of pain with intrathecal opioid therapy was 77.8% for nociceptive and 61.1% for neuropathic pain. Long-term results with patients suffering nociceptive pain showed a continuing good median pain reduction of 66.7%. Patients suffering from neuropathic pain showed poor long-term results (11.1% median pain reduction). Neuropathic pain in the extremities reacted least to the application of intrathecal opioids. Optimal results were obtained for nociceptive pain in the trunk area of the body., (Copyright 2001 S. Karger AG, Basel)

Objective: We first applied a novel haemostatic strategy involving Argon Plasma Coagulation (APC), an innovative no-touch electrocoagulation technique in which a high-frequency alternating current is delivered to the tissue through ionized argon gas, to brain tumour surgery, and report its usefulness and limitations., Methods: The APC system we used comprised an APC 300 developed by ERBE Elektromedizin GmbH, Germany. We applied APC to 13 brain tumours in 12 patients (5 meningiomas, 4 sarcomas, 2 glioblastomas, and 2 pituitary adenomas). To avoid unnecessary thermal injury to the tissue as much as possible, power/gas flow settings of 20 and 40 W were used. The impact time was varied individually but was around several seconds per one impact. The argon jet (1.5-4.5 L/min) clears a field of pooled blood and evenly conducts electrical energy to the target tissue. A thin and flexible probe particularly increased the usefulness of APC for haemostasis on deep-seated skull base tumour operations under a microscope., Conclusion: All patients were successfully treated and satisfied with the surgical results without any complications due to APC. APC appears to be an excellent alternative strategy for achieving haemostasis on vascular-rich brain tumour surgery, and may be valuable for the management of patients with coagulation defects.

We report on the dislocation of the tip of a lumbo-peritoneal shunting catheter into the cerebral parenchyma 10 months after insertion. The progressive migration towards the deep structures of the brain, once the catheter had left the peritoneal cavity, might have been caused by CSF-flow. Such hypothesis is supported by modern MRI technology visualizing CSF-flow in a spino-cerebral direction.

Background and Purpose--It has been demonstrated that moderate hypothermia attenuates brain damage, but the mechanism whereby this is achieved has not been clearly shown. Recently, the role of leukocytes as mediators of secondary brain damage after brain ischemia has been discussed. The aim of this study is to examine the effects of moderate hypothermia on leukocyte-endothelium interaction in the rat pial microvasculature after transient middle cerebral artery occlusion (MCAO). Methods--Rhodamine 6G-labeled leukocytes in brain surface were visualized with intravital fluorescence videomicroscopy through a closed cranial window. We analyzed the number of leukocytes adhering to the venular and arteriolar endothelium before ischemic insult and up to 3 hours after reperfusion. Rats were divided into 4 experimental groups. Group I (n=6) consisted of sham-operated animals. Groups II (n=6) and III (n=6) received left MCAO for 1 hour under normothermia (36 degrees C to 37 degrees C, group II) and under moderate hypothermia (30 degrees C to 32 degrees C, group III). Group IV (n=4) received left common carotid artery occlusion for 1 hour under normothermia. Results--The number of adhering leukocytes in venules in groups II and IV increased significantly (P<0.001) after reperfusion compared with the group I, but that in group III did not increase significantly (P>0.05). The number of adhering leukocytes in arterioles in group II increased significantly (P<0.01) compared with the other groups, although the adhering leukocytes were not as numerous as those seen in venules. Conclusions--It is demonstrated that hypothermia attenuates adhering leukocytes in venules and arterioles after reperfusion of MCAO. The inhibition of the leukocyte function may be an important factor in the neuroprotective effect of hypothermia.

Traumatic posterior circulation aneurysms in the absence of fractures and penetrating wounds are extremely uncommon, especially in children. To our knowledge this is the first traumatic posterior inferior cerebellar artery(PICA) aneurysm reported that cannot be related to a skull fracture or a trauma caused by the edge of a rigid meningeal structure. In the present case, the initial subarachnoid hemorrhage (SAH) was caused by a perforating artery, originating from the PICA, which was torn out as the result of a deceleration trauma. Such a mechanism explains both the initial SAH and the development of the false aneurysm responsible for the second SAH.

The primary aim of the present study was to compare the immune adjuvanticity of two different groups of glycolipids, i.e., the newly discovered basidiolipids from Basidiomycete mushrooms (Bl-1, Bl-2, Bl-3, and Bl-4), and saponin fractions from Quillaja saponaria. The basidiolipids, though with differential effectiveness of the Bl-components, stimulated the expression of serum immune globulins in mice that recognized co-injected antigens, bovine serum albumin (BSA) or a keyhole-limpet hemocyanin-ganglioside Gfpt1 conjugate (KLH-Gfpt1), respectively. The immune adjuvanticity of the basidiolipids was comparable to that of acidic (QAS2, QAS5, QAS10), and novel neutral (QNS1, QNS2, QNS3) saponin compounds isolated and purified from Quillaja saponaria bark bulk material. Basidiolipids, as well as, the Q. saponin fractions were only marginally antigenic. MPL-A, by contrast, a comparable immune adjuvant, stimulated the expression of specific antibodies that recognized this glycophospholipid. Different from the Q. saponins with restricted toxicity, the basidiolipids displayed no toxic or hemolytic properties.

Nauta et al. reported on a successful punctate midline myelotomy (PMM) for the treatment of intractable pelvic pain. The authors describe an other case history of a patient with multiple anaplastic carcinomas of the small intestine, peritoneal carcinosis and retroperitoneal lymphomas, suffering from severe visceral pain in the hypo-, meso-, and epigastrium. Nauta's PMM was successfully performed at the Th4 level. Narcotic medication was tapered from 30 mg i.v. morphine per hour pre-operatively to 5 mg per hour within 5 days postoperatively. Intensity of pain decreased from 10 to 2-3 on the visual analog scale. Only minor transient side effects appeared and the patient was discharged 5 days postoperatively. The pain reduction was maintained until the patient died from the extended disease five weeks later. We conclude that punctate midline myelotomy sufficiently controls not only pelvic visceral pain, but also visceral pain generated in the meso- and epigastrium. The findings support the concept of a midline dorsal column visceral pain pathway.

From the edible mushroom, the basidiomycetes Agaricus bisporus and Agaricus campestris, a novel carbohydrate-homologous series of four glyco-inositol-phospho-sphingolipids, designated basidiolipids, was isolated and the constituents purified. The chemical structures of the basidiolipids were elucidated to be: Manpbeta1-2inositol1-phospho-ceramide, Galpalpha-6[Fucpalpha-2]Galpbeta-6Manpbeta-2i nositol1-phospho-ceramide, Galpalpha-6Galpalpha-6[Fucpalpha-2]Galpbeta- 6Manpbeta-2inositol1-phospho-ceramide and Galpalpha-6Galpalpha-6Galpalpha-6[Fucpalpha-2] Galpbeta-6Manpbeta-2ino sitol1-phospho-ceramide. All four glycolipids contained a ceramide which was composed of phytosphingosine and predominantly alpha-hydroxy-behenic and alpha-hydroxy-lignoceric acid.

Complex demands and new indications in neurosurgery have led to the need for new electrosurgical generators (ESUs). For the first time, newly developed, automatically controlled ESUs make it possible to use extremely small and flexible instruments safely and to achieve reproducible microcuts and microcoagulations. These specifications make them suitable for neuroendoscopic interventions. In a series of more than one hundred patients with different intracranial and intraspinal pathologies the new electrosurgical devices and probes were used not only for coagulation but also for cutting. The main indications were endoscopic ventriculo-cisternostomy, ventriculo-cystostomy, and membranectomy. The electrosurgical generators as well as the bipolar microcoagulation and -cutting probes proved to be safe and effective for neuroendoscopic interventions.

Objectives: An in vivo closed spinal window technique in rats was designed for observing the spinal microcirculation, such as the change of vessel diameter, leukocyte adhesion, and red blood cell (RBC) velocity, which has been very rarely examined in vivo in the spinal cord., Methods: We made a very precise closed spinal window with a laminectomy at the C5 level using a dental acrylic resin and a cover glass (7 mm in diameter). Through this closed window, the dorsal surface of the rat cervical cord was observed with a video microscope, and the fluorescent images of rhodamine 6G-labeled leukocytes and fluorescein isothiocyanate-labeled RBCs were recorded and analyzed with a silicon-intensified target tube camera (30 frames/s) and an image-intensified high-speed video camera system (1000 frames/s)., Results: During CO2 inhalation, the pial arterioles responded with vasodilation of 12.4+/-10.4% (P<0.01) in 11 arterioles of seven rats. The adhering leukocytes significantly increased in 41 venular segments of seven rats after superfusion of the neutrophil chemoattractant, N-formyl-methionine-leucine-phenylalanine solution for 15 minutes (P<0.001) but not after superfusion of only artificial cerebrospinal fluid for 15 minutes. During these experiments, no adhering leukocyte was seen in the pial arterioles. Fluorescein isothiocyanate-labeled RBCs look like shooting stars in arterioles with silicon-intensified target tube camera processing at 30 frames per second, but individual fluorescein isothiocyanate-labeled RBCs could be recognized frame by frame with the image-intensified high-speed video camera system. In 13 arterioles of four rats, the RBC velocity was 5.3+/-2.0 mm per second., Conclusion: This closed spinal window technique in rats is available and applicable for the study of the spinal microcirculation, such as the pathophysiology of a secondary injury.

Background: Craniotomy with a mechanical twist drill is a standard, minimally invasive procedure in neurosurgery, widely used for the drainage of chronic subdural hematomas and the placement of ventricular drains. Nevertheless, the use of a standard twist drill trephine bears the risk of causing cerebral lesions., Method: A commercially available mechanical twist drill system has been modified by a special self-controlling drill and a pre-adjustable distance holder that limits intracerebral penetration. After initial cadaver testing, the modified trephine has been used for 65 trephinations in patients (37 chronic subdural hematomas, 21 external ventricular drains, 6 frontal hygromas, 1 tumor cyst)., Results: There were no complications related to the modified trephine; cerebral lesions caused by drilling too deeply or by uncontrolled penetration were safely prevented. In our series no procedure related infections occurred, and the drilling time was reduced significantly., Conclusion: The described modified mechanical twist drill enables fast, easy, and safe craniotomy without jeopardizing the advantages of a mechanical twist drill. Therefore, it can be recommended particularly for difficult emergency conditions.

Background: Endovascular treatment of cerebral aneurysms is a relatively new method, since only a few animal models and data are available. The present experimental study was performed in order to establish an appropriate aneurysm animal model, to determine the rate of permanent occlusion, and to correlate radiologic and morphologic findings., Methods: End-to-side anastomoses of both common carotid arteries were performed microsurgically in 53 chinchilla rabbits. Venous pouches were adapted into the newly created bifurcation, resulting in berry-shaped aneurysms comparable to those in humans with regard to size and hemodynamics. Platinum and tungsten coils were used for endovascular embolization. The embolized aneurysms were investigated radiologically and morphologically., Results: Twenty-three carotid bifurcation aneurysms remained for testing endovascular therapeutic approaches. The morphologic examinations of 13 embolized aneurysms revealed in no instance a complete obliteration, even in the three cases that were considered completely embolized according to angiographic criteria., Conclusions: The present animal model is an optimal tool for endovascular research. Analysis of the results of coil obliteration revealed a considerable discrepancy between radiologic and pathologic findings. The radiologic degree of aneurysm occlusion was overestimated.

We report the treatment strategies and results of 70 patients with spinal vascular malformations. Forty-six had dural arteriovenous fistulas, 12 spinal cavernous angiomas, nine intramedullary angiomas, and three intradural arteriovenous fistulas. The diagnosis was established for cavernomas by magnetic resonance images only and in the other cases by selective spinal angiography in patients whose neurological deficits, myelograms or magnetic resonance images suggested the presence of a spinal vascular malformation. All patients had symptomatic vascular malformations and were treated microsurgically. Intramedullary angiomas were operated when embolization seemed too dangerous or impossible and when they had a contact to the dorsal or lateral surface of the spinal cord. All but one were completely resected. In one angioma a small ventral residual fistula area was left. Complete obliteration of all fistulas was achieved. The cavernomas were primarily resected. Apart from one postoperative permanent deterioration with a paresis of the left arm in a patient with an intramedullary angioma, 16 cases presented only a transitory worsening of their neurological status after surgery. The long-term outcome of all these patients was good. Five patients had to be operated on again: three patients showed difficult localizations of dural fistulas which were still visible in the postoperative angiograms, one patient suffered a spinal epidural hematoma, and another patient showed a cerebrospinal fluid accumulation. We conclude that spinal dural arteriovenous fistulas, small intradural fistulas, spinal cavernomas, and symptomatic spinal angiomas with contact to the lateral or dorsal surface can be treated microsurgically with low perioperative morbidity.

Aneurysms of the vertebral artery (VA) and posterior inferior cerebellar artery (PICA) account for only about 3% of all diagnosed intracranial aneurysms. The surgical therapy of these aneurysms is complex and difficult due to the close topographical relationship between the neurovascular structures. Here, we report upon 27 patients with 29 such aneurysms. Of these, 22 patients (81%) were hospitalized because of a subarachnoid hemorrhage. Sixteen of these patients (72%) had an additional intraventricular hemorrhage. Twenty-one patients (78%) were surgically treated for their aneurysms, three of them also for an associated arteriovenous malformation. Aneurysms of the VA and the proximal PICA were exposed via a transcondylar (n = 11) or lateral suboccipital (n = 3) approach, those originating from the distal PICA via a paramedian suboccipital (n = 7) route. Endovascular therapy was used in three patients. A patient with a fusiform aneurysm of the vertebrobasilar junction was treated with a ventriculoperitoneal shunt only. Three aneurysms with a complex morphology were not treated. Of the patients operated upon, two died postoperatively due to vasospasm. Two other patients developed an incomplete dorsolateral medullary syndrome. One individual was lost for follow-up. The median follow-up period was 4.6 years (range 3-86 months). Both, the overall mortality (2/27) and morbidity (2/27) were 7.5%, respectively. Our results show that even complex vascular lesions of the posterior fossa can be treated with a satisfactory long-term outcome in the majority of our patients (85%). The multimodal management and an individually tailored microsurgical approach are key issues for the treatment of such aneurysms.

Refractory periods and recovery curves have been used to investigate the physiologic importance and disturbance of peripheral nerves, but the refractory periods of the central nervous system (CNS) have seldom been investigated. We estimated the refractory periods and the recovery curves of the ascending and descending conductive spinal cord evoked potentials (SCEP) in cats. The absolute refractory period of the first and second potentials of both the ascending and descending SCEP was approximately 0.4-0.5 ms. The amplitudes of the first potentials of the ascending and descending SCEP elicited by test stimuli exhibited significant differences, but their latencies did not differ significantly except at the interstimulus interval (ISI) of 1.5 ms, which implies that the same type of fibers was stimulated in the first potentials of the ascending and descending SCEP. The second potential of the descending SCEP elicited by test stimulus showed > 100% amplitude and a maximal recovery of 200% when the ISI was 3.0 ms. The third potential was produced in the test response more easily when a lower vertebral level (L4) was used as the recording site and the ISI was between 1.0 and 4.0 ms. We consider these phenomena to be the result of elimination of the synaptic inhibitory influence by the conditioning stimulus of the paired stimuli for the descending SCEP.

Study Design: This study was designed to examine the possibility of a new spinal cord monitoring method using measurement of the refractory period to monitor spinal cord function., Objectives: To determine whether measuring the refractory period and the recovery rate of conductive spinal cord evoked potential is a useful method for estimating spinal cord function., Background: Measuring the refractory period and constructing the recovery curve have been used to investigate peripheral nerve function. Spinal cord evoked potential elicited by the single stimulus usually is used to evaluate spinal cord function, and it has been said that 50% attenuation of the amplitude is the critical alarm level., Methods: In anesthetized cats, amplitude, area, and latency were measured on a personal computer from subtracted data collected with a paired-stimulation technique. The authors constructed recovery curves of ascending and descending conductive spinal cord evoked potentials and measured the refractory period during spinal cord compression., Results: When the amplitude of the ascending spinal cord evoked potential began to decrease during spinal cord compression, the amplitude of the response elicited by the second stimulus with interstimulus intervals of 0.8 msec and 1.0 msec decreased more significantly. When the amplitude of the ascending spinal cord evoked potential decreased to 50% of the precompression amplitude, the mean value of the absolute refractory periods of the ascending and descending spinal cord evoked potentials became prolonged from 0.40 +/- 0.007 msec to 0.53 +/- 0.014 msec, and the mean values of their amplitude and area recovery rates decreased from 75% +/- 1% to 35% +/- 2% (interstimulus interval, 0.8 msec) and from 81% +/- 1% to 46% +/- 2% (insterstimulus interval, 1.0 msec)., Conclusions: The change of the responses elicited by the paired stimuli is more sensitive than those elicited by the single stimulus in the spinal cord evoked potentials. The absolute refractory periods and the recovery rate during 50% attenuation of the precompression amplitude is the critical alarm level in spinal cord monitoring.

Collins' law, known as period of risk for recurrence (PRR), has been discussed as a reliable scheme for the prediction of recurrence or cure of embryonal tumours including medulloblastomas. The PRR is defined as the age at diagnosis plus 9 months of gestation. According to Collins' law, a patient who has no clinical evidence of recurrence within this time period is considered cured. We have applied this system to 66 patients (age range from 0 to 47 years) who underwent surgery for medulloblastoma at a single center between 1975 and 1990. Three patients in whom a recurrence could not be verified died within 6 months. Eight patients (12.1%, age range from 1 to 14 years) survived the PRR without relapse and are free of risk for recurrence according to Collins' law. Of the remaining 55 patients, 35 showed a relapse within the PRR with a mean latency of 18 months (0-78); Twenty patients are alive with no recurrence as yet, but are still within the PRR Three patients had non-recurrent benign brain tumours not connected to the initial tumours with a mean latency of 10 (8-14) years after medulloblastoma surgery. Thus, all our patients fulfilled the criteria for Collins' law. In conclusion, a patient's risk for medulloblastoma recurrence is significantly higher before than after the completion of the PRR. Therefore, the PRR is a helpful prognostic parameter that provides additional information about the risk of medulloblastoma recurrence. A medulloblastoma cure cannot be presumed with certainty by Collins' law because relapses after the PRR have been reported in other studies (1.4% of the cases). Intracranial lesions detected after a long follow-up might be radiotherapeutically induced second tumours.

Objective: The transcallosal route has been propagated as a safe approach to midline tumors. The present study was performed in order to elucidate the neurobehavioral late sequelae in patients after transcallosal microsurgery on near-midline tumors., Experimental Design: The present study was performed retrospectively with a delay between surgery and follow-up examination ranging from 2 to 36 months (mean 10.2 months)., Setting: The study was performed in the Department of Neurosurgery, University Hospital of the University of Technology (RWTH) Aachen, Germany., Patients: A consecutive series of 18 patients treated for an intracranial lesion by transcallosal surgery was included into the study. The patients had to be not younger than 16 and not older than 67 years. The age mean was 38.9 years (range 16 to 65 years)., Interventions: The surgical approach was performed along the falx cerebi under microneurosurgical conditions with direct use of the microscope after opening the dura., Measures: Beyond neurological examinations, the patients were submitted to an extensive neuropsychological testing battery. Furthermore, quality of life was examined by means of a questionnaire., Results: Surgery was performed without persistent new neurological deficits. Cognitive deficits were found in short- and long-term memory, motor fine-coordination, reaction time, divided attention and fronto-cortical capacity. The quality of life was particularly impaired in the area of cognitive capacity in daily life. These findings could be related to the duration of preoperative symptoms and to the tumor location., Conclusions: The deficits found cannot be explained by surgical damage to the corpus callosum itself. Rather, they seem to correspond to an extra-callosal pathology. Further studies with a prospective evaluation of larger patient samples are called for in the future.

The recovery cycle, following the conduction of action potentials along a nerve fiber, consists of the absolute refractory period (ARP), the relative refractory period (RRP) and the supernormal period (SNP). The recovery cycle of the descending conductive spinal cord evoked potential (SCEP) was shown during normal state, ischemia and after ischemia using paired stimuli in cats. During ischemia the refractory period revealed a trend towards increment. Five minutes after reperfusion the refractory period decreased transiently compared with the normal level and within 30 min the refractory period returned to the normal level. The recovery curve of the 2nd potential showed different pattern compared with that of the 1st potential. Moreover, during ischemia, firstly the 3rd potential and secondly the 2nd potential of the SCEP elicited by the 2nd stimulus were disturbed. These results demonstrated that there is increased excitability of the spinal cord to the second stimulus after a brief period of ischemia, and that the 2nd and 3rd potentials are evoked synaptically and easily disturbed during ischemia. Measuring the SCEP elicited by paired stimuli or constructing the recovery curve of the SCEP is useful for the electrophysiological assessment of spinal cord function.

The surgical aim in the treatment of symptomatic lumbar spinal stenosis is the relief of the patient's complaints by an adequate neural decompression. Unilateral laminotomy and bilateral spinal canal decompression represents such a safe, effective and minimally invasive surgical method. This technique has been successfully used in the operative treatment of 29 patients with symptomatic mono- or multisegmental lumbar stenosis. There was no surgically induced neurological deterioration. In one patient, an inadvertent dural tear occurred, and due to unchanged symptoms another patient with a multisegmental stenosis had to be re-operated on at an additional level. Postoperatively, 25 of the 27 patients with neurogenic claudication (93%) demonstrated a marked improvement of the walking distance. The follow-up of 25 patients (mean follow-up time was 18 months) demonstrated an excellent result without pain in 7 patients (28%); a good outcome with mild residual pain, but a normal working capacity in 15 patients (60%); and a fair outcome with unchanged postoperative low-back pain but markedly improved working capacity and walking distance in 3 patients (12%). Postoperative morphometric evaluation as well as the clinical improvement of the patient's symptoms clearly demonstrated that bilateral ligamentectomy and recess decompression were adequately and successfully achieved via unilateral approach.

During the 10th meeting of the WSSFN in Maebashi in 1989, we discussed 'endoscopic stereotaxy', and presented our preliminary results. This technique was first designed to optimize stereotactic biopsy, but it proved to be effective for other neurosurgical indications as well, including endoscopic stereotactic evacuation of intraparenchymal and intraventricular space-occupying cysts, endoscopic stereotactic cystoventriculostomy, third ventriculostomy, evacuation of brain abscess and intracerebral hematoma, and retrieval of adherent or free-floating ventricular catheters. Our results with endoscopic stereotaxy in different indications are encouraging, compared to conventional microsurgical techniques and pure stereotactic techniques. From 1989 to 1997 we have performed more than 400 stereotactic endoscopic procedures. The mortality rate is below 1%, the operative morbidity is below 3%.

A unilateral laminotomy for bilateral access to the lumbar spinal canal was investigated in human cadaver spine specimens to test its practicability in the treatment of spinal stenosis. Micro-surgical decompression was performed by partial resection of the ipsilateral facet, the medial portion of the laminar arch, the contralateral facet and by complete removal of the ligamentum flavum. Anatomical, radiological and morphometrical studies on 4 adult cadaver spine specimens have proved the feasibility of this unilateral approach. Complete bilateral flavectomy and partial bilateral facetectomy were the essential surgical steps for an adequate operative decompression.

The authors present a detailed account of the microsurgical production of bifurcation aneurysms in chinchilla rabbits for basic studies of endovascular coil embolization of aneurysms. End-to-side anastomoses of both common carotid arteries (CCAs) were performed, and a venous pouch was fitted into the newly created bifurcation. These experimental aneurysms closely mimic human cerebral aneurysms in size and hemodynamic features. Sixty-three animals underwent operation. Fifteen animals died in the course of the experiment and 15 were excluded because of a CCA occlusion within the carotid bifurcation. Electrical detachable platinum coils, also known as Guglielmi detachable coils (GDCs), and tungsten mechanical detachable coils (MDCs) were used for the endovascular occlusion of 26 bifurcation aneurysms (16 rabbits were treated with GDCs and 10 with MDCs). Initially, complete angiographic obliteration (95%-100% occlusion of the aneurysm) was achieved in nine rabbits and incomplete obliteration (< 95% occlusion) was seen in 17 animals. Final angiography 3 to 6 months later demonstrated complete occlusion in only four and partial occlusion in 22 aneurysms. At present, the histopathological examination of 17 embolized aneurysms has revealed incomplete obliteration of all aneurysms, even in those three cases that were thought to be completely embolized according to angiographic criteria. A general overestimation of the radiological degree of aneurysm obliteration was found.

Strength-duration curves of the ascending and descending conductive spinal cord potentials (SCEPs) in cats were obtained using constant current stimuli. For the formulation of numeric indices of excitability, the rheobase is defined as the minimal current strength below which response cannot occur even if the current continues, and the chronaxie is defined as the minimal duration of a current required to evoke the potential at twice the rheobase strength. The chronaxies and rheobases were calculated from the constructed strength-duration curves. The purpose of this study is to produce strength-duration curves and to evaluate the utility of chronaxies and rheobases for SCEPs. This study showed the following results: (1) there was a hyperbolic relationship between stimulus strength and stimulus duration at threshold values, similar to that seen in peripheral nerves; (2) the ascending and descending tracts of SCEP were mediated through the same pathway (based on the similar chronaxies and rheobases); (3) following spinal cord compression the chronaxie and rheobase increased significantly (P < 0.05), which is similar to peripheral nerve disturbance. However, the rheobase decreased significantly following slight spinal cord compression (P < 0.05) and systemic cooling (P < 0.01), and the strength-duration curve shifted showing a tendency towards decrease of the galvanic threshold, therefore, amplitude augmentation with slight compression and with decrease in temperature seems to contribute to the reduction of the threshold. The strength-duration curve, the chronaxie and the rheobase may be useful in assessing spinal cord function.

Hemangioblastomas of the spinal cord and the brainstem make up 4% of all spinal tumors and are less common than cerebellar hemangioblastomas. CT and MRI are essential for preoperative diagnosis. Nevertheless, cerebral and spinal angiography are also mandatory, since they allow a detailed study of the vascular situation, which is decisive for exact planning of a surgical strategy. The purpose of this study was to evaluate the diagnostic and therapeutic factors which influence surgical morbidity and postoperative outcome. Twelve patients harbouring spinal(8 cases) or medullary (4 cases) hemangioblastomas, all symptomatic with sensorimotor deficits corresponding to the level of the lesion were evaluated. All patients were treated in our department between December 1989 and September 1994. Complete resection of the lesion was achieved in each case. Postoperatively, none of the patients showed deterioration. Nine patients had immediate postoperative improvement of neurological signs and symptoms; in three patients the initial neurological deficits remained unchanged during the in-patient period. Late postoperative outcome demonstrated a clear improvement; in only one patient was there no change of the clinical signs, while in the other 11 patients a significant improvement of pre-existing neurological deficits was experienced. We conclude that microsurgical resection of spinal and medullary hemangioblastomas with low morbidity is feasible.

Fourteen cases of midline vertebro-basilar trunk aneurysms were operated on by four routes of surgical approach: middle fossa anterior transpetrosal approach (ATP), presigmoid transpetrosal approach (PTP), conventional lateral suboccipital approach (LSO) or suboccipital transcondylar approach (STC). There was no mortality, but the morbidity was different depending on the surgical approach. In basilar trunk aneurysms located higher than the internal auditory canal, excellent results were obtainable by ATP, especially in the case of posteriorly projecting aneurysms. For midline vertebral aneurysms located lower than the internal auditory canal, STC resulted in less surgical complications than LSO. Extradural resection of the jugular tubercle was necessary for aneurysms located on the distal vertebral artery at or close to the vertebro-basilar junction. For vertebro-basilar junction aneurysms located at the level of the internal auditory canal, hearing was preserved by STC, but not by ATP or PTP. However, choice of the surgical approach may depend on the direction of the aneurysm and the technical accessibility of the skull base. All these skull base approaches reduced surgical complications of retraction damage to the cranial nerves and the brain stem. This holds true for all aneurysms arising from the midline vertebro-basilar trunk.

The choice of the surgical approach and operative technique for the management of cerebrospinal fluid (CSF) fistulas of the anterior cranial fossa are still a controversially discussed topic. Although "extracranial" approaches through the paranasal sinuses are becoming increasingly more popular among otolaryngologists and maxillo-facial surgeons, most neurosurgeons traditionally prefer the "intracranial" repair of CSF fistulas by a craniotomy. We present an approach through the frontal sinus for the repair of dural defects behind the posterior wall of the frontal sinus and at the floor of the anterior cranial fossa. The operative procedure comprises the following main steps: 1) exposure of the anterior wall of the frontal sinus by a bicoronal incision; 2) excision of the anterior wall without frontal burr holes; 3) bilateral removal of the posterior wall of the frontal sinus; 4) extradural inspection of the dura behind the frontal sinus and above the cribriform plate, ethmoidal roof, and orbital roof bilaterally; 5) closure of dural tears by direct suture and a periosteal graft; 6) reinsertion of the anterior wall of the frontal sinus and fixation with titanium micro plates. Twenty-five patients operated upon using this technique are described. The aetiology of the frontobasal lesion was traumatic in 23, and an ethmoid carcinoma in two. In all patients, the dural fistulas were successfully repaired during the initial procedure. One patient died from sudden circulatory arrest after an uneventful postoperative course of nine days. Otherwise, there were no postoperative complications. This technique affords atraumatic extradural inspection and repair of dural fistulas bilaterally behind the frontal sinus, and above the cribriform plate and the ethmoidal and orbital roofs with none or minimal brain retraction. It therefore allows early repair of CSF fistulas also in patients with severe brain injury. Although we consider the extradural closure of fistulas the method of choice, this approach also allows for a combined extradural-intradural procedure, thus enabling the surgeon to treat associated intradural pathologies, such as traumatic lesions or tumours of the frontal cranial base.

In 14 patients (eight men, six women; mean age 58 [31-72] years) with intracranial aneurysm (basilar artery in nine, anterior branches in five) the aneurysm was occluded by electrically detachable platinum coils, advanced into the aneurysm introduced via a percutaneously introduced catheter system, under local anaesthesia and fluoroscopic control. Ten patients had acute subarachnoid haemorrhage (stage II-IV). In two patients several sessions were required before complete occlusion was achieved. In one patient, with a basilar artery aneurysm, the aneurysmal wall was perforated (angiographically demonstrated contrast-medium extravasation), but this remained clinically asymptomatic. There has been no recurrence or renewed bleeding during a follow-up period of 6-12 months. The method is a highly promising addition to the micro-neurosurgical treatment of such aneurysms. However, as long-term results are still awaited, indications for using the method should be strict and only those patients should be so treated in whom operation would be associated with a high risk or who are inoperable.

Selection of the approach and technique for surgical repair of aneurysm of the vertebrobasilar artery system is mainly based on angiographic features. This report emphasizes that planning the surgical procedure should also include preoperative evaluation of the individual skull base configuration, as well as the relationship between aneurysm site and surrounding bony structures. These features are evaluated on thin slice CT scans using bone tissue algorithms and are particularly important for adequate exposure of distal vertebral artery (VA) or midline aneurysms, because these cases require drilling of the jugular tubercle. For the use of lateral approaches, the surgeon must be familiar with the extradural and intradural anatomy of the foramen magnum region and may rely on at least five anatomical landmarks for orientation during surgery: 1) the dural entrance of the vertebral artery; 2) the posterior condylar emissary vein; 3) the medial rim of the distal sigmoid sinus; 4) the hypoglossal canal; 5) the jugular tubercle. To increase the safety of the procedure, the authors recommend an individualized tailoring of the surgical approach according to the variable morphological situation of each patient.

Nine consecutive cases of surgically treated spinal cavernous angiomas are presented. Our series consists of 6 men and 3 women with the following intramedullary spinal location of the cavernomas: 4 cervical, 4 thoracic and 1 thoraco-lumbar. All 9 patients were symptomatic with signs of myelopathy and senorimotor deficits corresponding to the level of the lesion. Six patients underwent laminectomy and in three patients a hemilaminectomy was performed to approach the lesion. A complete resection of the cavernoma was achieved in each case. Five patients showed transient neurological deterioration, in three cases the neurological status remained unchanged, and one patient experienced a slight improvement of symptoms during the early postoperative period. At follow-up examination (mean 14 months postoperative), a clear improvement of the clinical signs was demonstrable in 6 patients, and a complete resolution of the pre-existing symptoms and signs was achieved in two individuals. In one case the clinical state remained unchanged. It is concluded that microsurgical resection is the treatment of choice in cavernomas of the spinal cord.

Although primary treatment of medulloblastoma is now successful in a high percentage of patients, its secondary manifestations still bear a poor prognosis. Thorough studies of secondary manifestations are therefore pivotal to plan therapeutic approaches for the long-term management of medulloblastoma. Here we describe the incidence of secondary tumour manifestations in 66 patients of a single centre who underwent surgery for medulloblastoma between 1975 and 1990. No patient was excluded due to a poor postoperative course. Thirty-five patients showed evidence of secondary tumour growth. Of these, 17 suffered from local recurrence, and 27 developed metastastatic disease. The median latencies for secondary manifestations were 25 months for local recurrence (n = 17), 11 months for spinal metastases (n = 10), 15 months for supratentorial metastases (n = 8), 8 months for subleptomeningeal dissemination (n = 6), and 23 months for systemic metastases (n = 8). Two patients developed primary metastatic spread to the posterior fossa. Of 8 patients with supratentorial metastases, 6 developed fronto-basal lesions. In our patients, 89% of secondary lesions occurred within less than 3 years after primary diagnosis. 85% of patients with extra-axial tumour spread had been treated with a permanent shunt. Radical tumour resection and radiotherapy with 30 Gy to the neuraxis and 20 Gy boost to the posterior fossa was an important prognostic factor in this series. Patients with additional chemotherapy did not benefit significantly from this treatment. We conclude that optimal management of the primary lesions should aim at (i) total resection, (ii) avoid permanent shunting, and (iii) completion of the radiotherapy with inclusion of the medial frontobasal cisterns in the radiotherapeutic regimen. Our analysis suggests that adequate postoperative screening programmes should consist of 3-monthly scans of the neuraxis in the first three postoperative years and 6-monthly scans thereafter.

Although recently survival of some medulloblastoma patients increased remarkably, it remains a serious diagnosis in others. In order to predict the postoperative prognosis in patients treated for medulloblastoma, a new staging, scoring and grading system was developed. Sixty-six patients operated on microsurgically between 1975 and 1990 at a single neurosurgical center were fully followed-up. No patient was excluded due to a poor postoperative course. Completion of commonly used radiotherapy protocols was attempted in all patients. Survival of patients was evaluated by the Kaplan-Meier method. The following 5 parameters were selected to define subgroups: patients' age, tumour location and histology, degree of resection and presence or absence of metastases. Patients older than 10 years had a better prognosis than individuals aged 10 or less (p < 0.01), patients with lateral tumours had a better prognosis than patients with midline tumours with brain stem infiltration (p < 0.05), patients with complete tumour resection had a more favourable prognosis than individuals with subtotal (p < 0.01) or partial resection (p < 0.001), patients without metastases at the time of diagnosis had a better prognosis than individuals without such evidence (p < 0.001), patients with the desmoplastic tumour variant had a better prognosis than patients with classical tumour histology (p < 0.01). According to the prognosis of a distinct subgroup, scoring points were distributed which correlated with the degree of inter-subgroup significances. The sum of a single patient's scoring points was called the total score. Based on this score, three groups of prognosis were distinguished.(ABSTRACT TRUNCATED AT 250 WORDS)

We carried out 22 examinations to determine the value of three-dimensional (3D) volumetric CT (spiral CT) for planning neurosurgical procedures. All examinations were carried out on a of the first generation spiral CT. A tube model was used to investigate the influence of different parameter settings. Bolus injection of nonionic contrast medium was used when vessels or strongly enhancing tumours were to be delineated. 3D reconstructions were carried out using the integrated 3D software of the scanner. We found a table feed of 3 mm/s with a slice thickness of 2 mm and an increment of 1 mm to be suitable for most purposes. For larger regions of interest a table feed of 5 mm was the maximum which could be used without blurring of the 3D images. Particular advantages of 3D reconstructed spiral scanning were seen in the planning of approaches to the lower clivus, acquired or congenital bony abnormalities and when the relationship between vessels, tumour and bone was important.

A new experimental model is described that uniquely allows the in vivo observation and quantification of vascular caliber changes on the dorsal surface of the feline spinal cord. The model consists of a rectangular Plexiglas window that is sutured to the lumbar dura and is supported by a special holder. Inlet and outlet tubes attached to the window serve for topical applications of mock cerebrospinal fluid or vasoactive agents to the surface of the cord and for continuous monitoring of intrathecal pressure. Pial vessels below the window were observed at 200-fold magnification with the aid of a microvideo camera. Spinal arterioles reacted to hypercarbia and superfusion with acetylcholine solution in a manner similar to cerebral arterioles. Tests with increased intrathecal pressure showed that the window remained watertight between 25 and 130 mm Hg, with an average leakage pressure of 57.8 +/- 33.5 mm Hg. To promote the use of this model in other laboratories, the authors give a detailed description of the closed spinal window preparation and report their experiences gained from 50 experiments. It is concluded that the closed spinal window is a highly reproducible model, suitable for the study of the feline spinal microcirculation for several hours in vivo.

In a series of 10 patients with stereotactically treated basal ganglia haematoma rtPA was used to dissolve remaining clots. Pre-operative haematoma volume ranged between 39 and 111 cm3 (average 56 cm3). Stereotactic aspiration alone yielded an average volume reduction of 60% (range 23 to 78%). Haematoma cavity was instillated with rtPA repeatedly beginning 24 hours after the stereotactic intervention. At the end of rtPA therapy between 2 and 4 days after onset of the haemorrhage 67 to 92% (average 84%) of the initial haematoma was removed in all patients. More than 80% of the pre-operative clot could be removed in 8 out of 10 patients between day 2 and 4. There were no signs of rtPA related toxicity. At the end of the follow-up period (between 4 and 17 months--mean 8 months) 6 patients were awake, oriented and with a residual hemiparesis able to live in their familiar environment. It is concluded that local rtPA instillation is an effective additional treatment to further resolution of deep seated intracerebral haematomas after stereotactic aspiration.