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Background: Cavernous malformations have generally been viewed as fairly benign vascular lesions with low potential for causing massive hemorrhage., Case Description: We present an interesting case of multiple CMs, several of which were formed de novo and exhibited aggressive biological behavior resulting in recurrent episodes of intracranial hemorrhage over a 10-year period. This case illustrates a dynamic and aggressive form of CMs. Recent advances in our understanding of the molecular pathogenesis of CMs implicate genetics as an important pathogenic factor, which is the most likely etiology of this patient's presentation., Conclusion: Special challenges exist in managing young children with multiple, highly aggressive CMs., (Copyright 2009 Elsevier Inc. All rights reserved.)

Background: Access to lesions located in the atrium of the lateral ventricle without causing neurologic deficit can be challenging. Here, we demonstrate the supracerebellar transtentorial transcollateral sulcus (STTS) approach as an alternative route to the atrium of the lateral ventricle using anatomical dissections in cadavers., Methods: Suboccipital craniotomy with extension above the transverse sinus was performed in 5 arterial and venous latex-injected cadaveric heads (10 hemispheres). After the dural opening, arachnoidal dissection of the supracerebellar space was performed, and the tentorium cerebelli was cut from lateral to medial. This revealed the parahippocampal and fusiform gyri and collateral sulcus (CS). The distance from the CS to the atrium was measured., Results: The atrium of the lateral ventricle was entered through the CS in each specimen. The cerebral hemispheres were removed from each cadaveric specimen, and dissections were performed. The distance from the CS to the atrium was 1.30 cm on the right side and 1.31 cm on the left. The CS was bifurcated in 62% of the hemispheres, whereas it was single in 38%. Through this approach, only the "u" fibers of the CS were damaged, and the fibers of the optic radiation in the inferolateral wall of the atrium were preserved., Conclusion: The STTS approach may be an effective alternative approach to lesions located in the medioposterior aspect of the atrium of the lateral ventricle in selected cases. Further clinical studies to evaluate the safety and efficacy of this approach are needed.

Background: Chiari III malformation (CM3) is rare among Chiari malformations (I-IV). Its definition has been expanded to include caudal medullary displacement and hindbrain herniation into encephaloceles in lower occipital and high cervical regions. Prognosis is recorded as dismal, with respect to survival and functional outcome., Methods: We describe the presentation, radiologic evaluation, and repair of this malformation using methyl-methacrylate cranioplasty and an occipital scalp rotation flap for closure. Outcome after surgery is addressed., Results: Adequate closure of the defect and protection of underlying structures was achieved without undue stress at incision site., Conclusions: This method of closure can be considered in cases of large occipital and cervical encephaloceles with poor skin cover and added osseous anomalies around the foramen magnum.

Background: The authors describe their surgical experience of a hydatid cyst in the brainstem, which is an unusual site. The cyst was internally decompressed and totally excised. Although the Dowling technique has been described to be the ideal method for removal of hydatid cysts, it may not be possible when the cyst is in a deep-seated, vital, and eloquent location. We report the use of internal decompression by aspiration followed by total excision as an alternative method when the cyst is located in vital areas of the brain., Case Description: A 40-year-old female presented with headache, progressive right-sided weakness, double vision, and unsteadiness of gait of 1-month duration. On examination, she had left one-and-a-half syndrome, right hemiparesis of 3/5, and left cerebellar signs. Computed tomographic and MRI scans of the brain revealed a solitary, stenciled-out cystic lesion in the brainstem more toward the left side with features suggestive of hydatid cyst. A left retromastoid craniectomy followed by left middle cerebellar peduncle approach, aspiration of the cyst, and total excision of the cyst was performed. Postoperatively, the patient improved progressively and was asymptomatic with minimal left cerebellar signs at 1-year follow-up., Conclusion: Hydatid cyst is a benign lesion. Appropriate management is mandatory for reducing the morbidity. Although the Dowling technique with its modifications is appropriate for cerebral parenchymal surfacing or superficial hydatid cysts, in deep-seated cysts located in eloquent and vital areas such as the brainstem, management by internal decompression by aspiration followed by extirpation of the cyst wall, protecting the surrounding cisterns and CSF spaces, is an alternative option.

Background: The pathogenetic mechanism of intraventricular arachnoid cyst development is still controversial, but is believed to originate from the vascular mesenchyme or as an extension of the arachnoid cyst in the subarachnoid space into the ventricle through the choroidal fissure. We report a case supporting the extension hypothesis and suggest differential points between an intraventricular arachnoid cyst that extended from the supracerebellar space and a lateral ventricular diverticulum that extended into the supracerebellar cistern., Case Description: A 12-month-old girl presented with macrocephaly and developmental delay. Her magnetic resonance imaging showed an arachnoid cyst that had developed from the supracerebellar space in the posterior fossa, and which extended into the left lateral ventricle resulting in expansion of the left lateral ventricle and displacing the choroids plexus anteriorly and laterally and the midline to the right. We treated an intraventricular arachnoid cyst by endoscopic fenestration resulting in dramatic reduction of the intraventricular arachnoid cyst with large bilateral subdural fluid collection. We performed a subduroperitoneal shunt for subdural fluid collection and subsequent cystoperitoneal shunt for the remnant cyst., Conclusion: We suggest that this case supports the extension hypothesis from the subarachnoid space through the choroidal fissure into the lateral ventricle. We also suggest that one of the radiological differential points between an intraventricular arachnoid cyst and a ventricular diverticulum is displacement and compression of the choroid plexus of the lateral ventricle.

Background: The aim of this study was to present our technique of posterior fossa surgery and to evaluate whether cerebellar retractors are needed., Methods: Since March 1989, more than 500 surgeries were performed through retrosigmoid approach, and our surgical technique was described. The data were evaluated whether or not cerebellar retractors were used in the operations., Results: The surgeries were vestibular neurectomy, acoustic neuroma removal, and neurovascular decompression in 351, 135, and 14 patients, respectively. Cerebellar retractors have not been used in vestibular neurectomies and in most acoustic neuroma surgeries. The cerebellar retractors have been used in all of the neurovascular decompression surgeries where better exposure of the root entry zones of the cranial nerves is needed, and intracranial endoscopy is applied for further exposure and decompression of the vascular loop., Conclusion: There is no need for cerebellar retractors when adequate conditions such as patient positioning, adequate anesthesia techniques, and surgical manipulations are applied in posterior fossa approach except for neurovascular decompression and some of the acoustic neuroma surgeries.

Background: Lhermitte-Duclos disease is a cerebellar lesion, characterized by an overgrowth of cerebellar ganglion cells, which replace granular cells and Purkinje cells. Lhermitte-Duclos disease may be a manifestation of Cowden syndrome (multiple hamartoma-neoplasia syndrome). The nature of LDD, whether neoplastic, dysplastic, or hamartomatous, is still not exactly understood. Metabolic imaging of the amino acid metabolism using PET could be useful for noninvasive characterization of these lesions., Methods: To define the Meth-PET imaging characteristics of these lesions, we undertook a Meth-PET study in 4 patients with LDD after obtaining informed consent. All 4 patients had clinical signs of Cowden syndrome. In 2, the diagnosis was made with MRI; in 2, it was confirmed histologically., Results: Using Meth-PET, the cerebellar lesions had a high methionine uptake, except in the subtotally resected lesion. The uptake of the lesions was markedly higher than that of the contralateral normal regions. The mean L/C ratio was 2.07., Conclusion: 11C-methionine positron emission tomography visualizes the lesion of Lhermitte-Duclos disease as a high uptake area. This amino acid hypermetabolism may be related to the slow growth of the lesions, and is an argument to suggest that patients with LDD should be followed up carefully to detect progression of the cerebellar lesion.

Background: Lesions located in the posterolateral brain stem, particularly the middle cerebellar peduncle, have presented surgeons with a challenge associated with significant morbidity., Methods: We present a case of a 20-year-old woman who had a hematoma in the right middle cerebellar peduncle with a ventricular rupture. Angiography revealed an arteriovenous malformation (AVM) located in the same portion, extending from the lateral surface near the entry zone of the trigeminal nerve to the paraventricular area of the fourth ventricle, which was completely resected through a posterior transpetrosal approach. We also describe the microsurgical anatomy of this region in a cadaveric specimen, presenting the anatomic landscape at the target when approaching through this route., Results: The patient's postoperative course was uneventful and her neurologic deficits progressively but gradually improved. When a lesion exists at or close to the surface of the middle cerebellar peduncle, the best approach, in our estimation, is a transpetrosal approach because the lesion can be approached perpendicularly with a short working distance, various angles for dissection are available, and minimal retraction of the temporal lobe and cerebellum is required., Conclusion: An AVM embedded in the middle cerebellar peduncle can be successfully resected using a posterior transpetrosal approach, though we concede this approach is slightly labor-intensive and time-consuming.

Background: Mutism has been associated with injury to midline cerebellar structures secondary to degenerative disease, tumors, hemorrhage, or surgery. Typically, cerebellar mutism syndrome (CMS) has been seen in children and only rarely described in adults after surgery of the posterior fossa. This syndrome typically arises 48 hours after the initiating event and resolves approximately 7 to 8 weeks later. Characteristics of CMS include complete absence of speech without impaired consciousness, other cranial nerve deficits, or long tract signs., Case Description: The authors report on 2 patients each of whom developed cerebellar mutism after tumor resection using a posterior fossa approach. The first patient underwent gross total resection of a pineal region tumor via a supracerebellar approach. The second patient underwent posterior fossa decompression for a left cerebellar hemispheric renal cell carcinoma metastasis with adjacent hemorrhage. One patient displayed a variant of cerebellar mutism with severe ataxic dysarthria without complete absence of speech, whereas the other demonstrated frank mutism. After neuroimaging studies confirmed the absence of a surgically treatable postoperative cause for the patients' symptoms, they were managed in a supportive fashion (eg, speech therapy) and improved within 3.5 months and 1 year, respectively., Conclusion: It is paramount that neurosurgeons be aware of cerebellar mutism with regard to its very rare occurrence in adults, its time of onset, and typical self-limiting course.

Background: Meningeal melanocytomas are rare primary melanotic tumors of the leptomeninges. According to our review of the literature, just 22 cases of meningeal melanocytoma (MM) of the posterior fossa have been previously reported. Some aspects related to diagnosis, radiological appearance, histopathologic features, and management are discussed in this paper., Case Description: We describe the case of a 42-year-old female presenting with severe headache, nausea, and vomiting. Computed tomography and magnetic resonance imaging demonstrated a posterior fossa lesion that was surgically treated. Histopathologic examination showed a highly cellular melanocytic neoplasm with numerous dark pigments in the cytoplasm. Immunoperoxidase staining S-100 protein and HMB 45 demonstrated immunoreactivity for both, confirming the diagnosis of MM., Conclusions: In conclusion, MMs are rare histologically benign tumors that can be cured by complete surgical resection alone, which should be the goal of the treatment. These lesions, although rare, should be considered in the differential diagnosis of tumors of the posterior fossa.

Background: Craniocerebral missile injuries have steadily increased to become the most common form of penetrating neurotrauma in our environment resulting in continued morbidity and neuropsychological sequelae. Civilian infratentorial gunshot injuries are uncommon but generally regarded as fatal injuries, with many patients dying before reaching hospital., Methods: A retrospective analysis of 1,069 patients with civilian gunshot wounds (GSW), admitted to our unit over a 14-year period (1986-2000), identified 26 patients with infratentorial gunshot injuries (2.4%). A detailed analysis of these patients was carried out, which included demographic factors, clinical and anatomic correlation, computed tomography scans, surgical management, and outcome., Results: All patients were male. The mean age was 26.5 +/- 11.5 years and the mean admission Glasgow Coma Score 11.8 +/- 2.7. Twenty-four of 26 patients required cerebrospinal fluid (CSF) diversion to control secondary hydrocephalus. The second commonest surgical procedure was posterior fossa decompression. Five of 26 patients died (19.2%). Severe morbidity was noted in 9 of 21 surviving patients (42.8%). Significant predictors: good outcome was associated with primary missile entry of the infratentorial compartment (p = 0.005), while patients with supratentorial to infratentorial missile trajectory were noted to have a poorer outcome (p = 0.041). Location of cerebellar injury (lateral or medial) and missile caliber had no significant influence on patient outcome., Conclusion: Early control of incipient or established hydrocephalus and aggressive surgical management where appropriate, with careful postoperative monitoring, is necessary for good outcome in patients with civilian infratentorial missile injuries.

Background: The authors describe a case of ruptured distal superior cerebellar artery (SCA) aneurysm in a patient with systemic lupus erythematosus (SLE)., Case Description: A 31-year-old female who had been treated for SLE for 13 years presented with a subarachnoid hemorrhage. Cerebral angiography demonstrated an aneurysm arising from the cisternal portion of the left superior cerebellar artery. The patient underwent early endovascular coil embolization and was discharged from our hospital without neurological deficit., Conclusion: Aneurysms arising from peripheral segments of cerebellar arteries are rare, and delayed surgical clipping has been recommended for these lesions. In addition, the outcomes of SLE patients with ruptured cerebral aneurysms are reported to be very poor due to the systemic complications of SLE. However, our patient had a favorable outcome with early endovascular treatment for the ruptured aneurysm and with appropriate medical treatment for the accompanying SLE. Therefore, early endovascular coil embolization is worthy of consideration among the options for therapeutic intervention in these conditions.

An 8-year-old girl experienced five repeated hemorrhagic episodes around the cerebellar vermis. Surgical specimens histologically showed abnormal vascular components invaded by tumor cells. Autopsy disclosed medulloblastoma disseminating in the subependymal zone of the ventricles. An atypical clinical course is reported with special attention to the cause of hemorrhage.

Our experience with the transpetrosal-transtentorial approach to retrochiasmatic craniopharyngiomas is herein reviewed and an operative technique is described. Excellent exposure of the retrochiasmatic and suprasellar regions is gained with a minimal retraction of the temporal lobe and cerebellum. Eight cases of retrochiasmatic craniopharyngiomas that extended into the posterior hypothalamus were operated on utilizing this approach. The operative results were excellent in five patients, good in one, and poor in one. There was one death later. The principal advantage of this technique is that it allows the hypothalamus, even in cases in which the structure is remarkably displaced upwards, the third ventricular walls in cases of the intraventricular extension of the tumor, and the inferior surface of the optic chiasma and nerves to be visualized directly and thus safely preserved.

A series of 64 patients with pineal region tumors operated on between 1981 and 1985 at the Beijing Neurosurgical Institute is reported. All were approached using an occipital transtentorial technique. A gross total or radical subtotal removal was achieved in 87% with a total mortality and morbidity of less than 10%. The relative advantages of this particular approach to the pineal region are discussed. It is concluded that the transtentorial approach to the pineal region provides excellent visualization and circumvents many of the pitfalls of other approaches to this region.

The treatment alternatives for the patient who becomes comatose following nontraumatic infarction of the cerebellum are discussed. The acute hydrocephalus produced by the swollen cerebellum is readily diagnosed by computed tomography scan and is identified as a hypodense mass without contrast medium uptake that obliterates the fourth ventricle. Two typical cases are described, one managed medically and one surgically. All available reports in the world literature of similar patients treated surgically are reviewed. Based on the outcome analysis of the foregoing, a strategy is offered for the handling of future cases.

A three-quarter prone, operative approach to the pineal region is described: the three-quarter prone, operated-side-down position. This approach avoids the disadvantages of the approaches from other directions to this region and provides a comfortable position for the surgeon and assistant, minimal retraction of the parietal-occipital lobe, and access to the third ventricle, pineal region, midbrain, and superior vermis.

A 60-year-old man with vertebrobasilar ischemia unrelieved by anticoagulation was found to have a midbasilar stenosis with an inadequate basilar collateral circulation. He underwent a right superficial temporal-superior cerebellar artery bypass. Following this operation he had a subarachnoid hemorrhage and right third nerve palsy that was due to formation of a pseudoaneurysm at the site of the anastomosis. This aneurysm was managed by ligation of the right superficial temporal artery. Subsequently it became necessary to perform a left superficial temporal artery-superior cerebellar artery bypass because of severe posterior circulation ischemic symptoms.

The authors report a very rare case of ruptured aneurysm in the fourth ventricle. This aneurysm arose at the elongated supratonsillar segment of the right posterior inferior cerebellar artery and successful clipping was carried out after splitting the lower vermis.

Aneurysms of the posterior inferior cerebellar artery are relatively rare. Fourteen such aneurysms (10 vertebral, 4 peripheral) are reported, and their clinical presentation, surgical therapy, and outcome are discussed. All 14 patients had suffered a subarachnoid hemorrhage; 93% (n = 13) underwent direct clipping of the aneurysm while 7% (n = 1) underwent coating of the aneurysm. Two patients died in the perioperative period (one from vasospasm and one from rebleeding). Full activity was achieved by all but one (92%) of the remaining patients in extended follow-up.

Does cerebellar retraction during operations in the posterior fossa contribute to increased morbidity and mortality, and if so, what are the critical factors involved? In order to answer these questions, graded retractor pressures of 10, 20, and 30 mm Hg were applied for one hour to the cerebellar hemispheres of dogs in the sitting position. It was noted that the amount of mechanical pressure and the difference between systemic perfusion pressure and retractor pressure were important determinants of the outcome. The mechanism of damage from retractor pressure is discussed.