Postoperative posterior fossa syndrome: unraveling the etiology and underlying pathophysiology by using magnetic resonance imaging.

BACKGROUND: Posterior fossa syndrome (PFS) is a severe, postoperative complication occurring in about 25 % of pediatric patients undergoing surgery for midline tumors in the posterior fossa. In recent years, MRI-based research elucidated the cause of PFS and shed new light on its putative pathophysiology. This review highlights the major advances arising from research of this topic. RESULTS: Postsurgical damage patterns in patients after posterior fossa surgery show that PFS results from bilateral surgical damage to the proximal efferent cerebellar pathways (pECPs). Surgical pECP disruption has other MRI-detectable effects that are more remote. Patients with PFS tend to develop global supratentorial cortical hypoperfusion, likely representing reversed, cerebello-cerebral diaschisis. Because this hypoperfusion is most prominent in frontal regions, cerebellar mutism may indicate a dominantly frontal lobe dysfunction, hence a peculiar form of speech apraxia. Injury to the pECP also leads to contralateral inferior olivary nucleus degeneration. When bilateral hypertrophic olivary degeneration (HOD) is observed after posterior fossa surgery, affected patients have clinical PFS. Therefore, it is suggested that bilateral HOD may be a sensitive and, in appropriate clinical settings, reliable a posteriori surrogate imaging indicator of bilateral disruption of the pECPs and consequently of PFS. Having such a "validation tool" presents new opportunities to develop better definitions for the phenotypes within the clinical spectrum of PFS. CONCLUSIONS: Anatomical and functional MRI techniques are suitable and valuable tools with which to detect structural changes and pathophysiological processes in the development and evolution of PFS and may be key, integral components of future clinical research endeavors.

Odontoid process and clival regeneration with Chiari malformation worsening after transoral decompression: an unexpected and previously unreported cause of "accordion phenomenon".

PURPOSE: Transoral odontoidectomy followed by occipito-cervical fixation is a widely used approach to relieve ventral compressions at the craniovertebral junction (CVJ). Despite the large amount of literature on this approach and its complications, no previous reports of odontoid process and clival regeneration following transoral odontoidectomy are present in the English literature. METHODS: We report the case of odontoid process and clival regeneration following transoral odontoidectomy. RESULTS: A 7-year-old boy presented with symptoms of brainstem and upper cervical spinal cord compression due to a complex malformation at the CVJ including a basilar invagination with Chiari malformation. A successful transoral microsurgical endoscopic-assisted odontoidectomy extended to the clivus was performed along with occipito cervical instrumentation and fusion. Clinical and radiological resolution of the CVJ compression was evident up to 2 years post-op, when the child had a relapse of some of the presenting symptoms and the follow-up CT and MRI scans showed a quite complete regrowth of the odontoid process, clival partial regeneration and recurrence of preoperative Chiari malformation. CONCLUSIONS: Besides the need of an accurate complete resection of the periosteum, which apparently was incompletely performed in our case, our experience suggests the need of resection of the odontoid down to the dentocentral synchondrosis and an accurate lateral removal of the bone surrounding the anterior tubercle of the Clivus is advised when an anterior CVJ decompression is required in children presenting a still evident synchondrosis at neuroradiological investigation.

[VEGETATIVE REACTIONS AS PROGNOSTIC FACTOR IN POSTERIOR FOSSA SURGERY].

Mortality rate related to posterior fossa tumors resection varies from 1 to 8 percent, according to various authors. It depends on tumor size and its growth characteristics. To determine the physiological acceptability of surgery, physiological significance of vegetative reactions associated with tumors resection has to be assessed. We divide these reactions (centrogenic reactions - CR) into 2 main groups. The first group has a relatively precise morphofunctional structure, similar to the classic reflex arc. They appear due to irritation of local centers or cranial nerves nuclei with mixed motor-vegetative structure. In most cases they are not connected with anatomic damage of CNS structures. The second group of CR is correlated with dysfunction of brain and represents brain s attempt to turn into a new functional state. Their presence should be considered as a functional degradation symptom, which might be even irreversible. Emergence from anesthesia in the operative room is not recommended in this clinical situation. Neurovegetative stabilization should be provided for a period of 6 to 24 hours after tumor resection.

Cerebellar haemorrhage in the extremely preterm infant.

AIM: The aim of this study was to investigate the incidence, risk factors and developmental outcomes of cerebellar haemorrhage in the extremely preterm infant. METHODS: Over a 4-year period from January 2004, all patients with cerebellar haemorrhage born at 24-27 weeks gestation or with a birthweight < 1000 g were identified from database review. All patients had cranial ultrasound scans including views from the mastoid fontanelle. To verify the incidence, a review of all reports over the 4-year period and a review of all cranial imaging over a 2-year period were carried out. RESULTS: From the data analysed on 339 neonates, five cases of cerebellar haemorrhage were identified, four on ultrasound scan (1.2%) and one on magnetic resonance imaging (1.5% total). Two cases were associated with grade III peri-intraventricular haemorrhage. The cases had diverse maternal, antenatal and post-natal risk factors. The two with associated peri-intraventricular haemorrhage have developmental delay. The cases with isolated cerebellar haemorrhage had good neurodevelopmental outcomes. CONCLUSIONS: A low incidence of cerebellar haemorrhage identified from the mastoid fontanelle was demonstrated. The neurodevelopmental outcome was better than that described in previous reports.

Multiple cranial neuropathy as the initial presentation of metastatic prostate adenocarcinoma: case report and review of literature.

The skull base is an atypical metastatic site for prostate carcinoma. It is usually encountered late in the disease process in patients with known advanced disease. However, skull base involvement causing cranial nerve palsies may rarely be the presenting sign of prostate carcinoma. Such patients may present to a number of specialties including neurosurgery and can pose a diagnostic challenge in the absence of lower urinary tract symptoms. Here, we describe an unusual case of prostate adenocarcinoma presenting as a central skull base tumour with multiple cranial neuropathy.

Interdural haemorrhage of the posterior fossa due to infraclinoidal carotid artery aneurysm rupture.

Several anatomical studies indicate that the intracranial pachimeninges consist of two dural layers joined together, which divide while bordering the venous sinuses, therefore located in an interdural space. We present here an uncommon case of haematoma due to rupture of an infraclinoidal internal carotid artery aneurysm. The dome of the aneurysm leaned against the posterior wall of the cavernous sinus and, following laceration, pierced the inner dural layer and caused its detachment from the periosteal layer, thus determining a truly interdural haematoma which progressively involved the whole posterior fossa. A 42-year-old female was admitted to our institution with a recent history of thunderclap headache and right ophthalmoparesis. Two cerebral computerised scan tomographies performed elsewhere tested negative for subarachnoid haemorrhage. A cerebral magnetic resonance imaging (MRI) showed a thin collection of blood adjacent to the clivus and all along the wall of the posterior fossa and foramen magnum. A right infraclinoid internal carotid artery aneurysm was also diagnosed, subsequently better highlighted on angiography. The patient underwent surgery with aneurysm clipping. Post-operative course was uneventful, and control angiography showed complete exclusion of the aneurysm from blood circulation. The patient was discharged 5 days later. At 3 months follow-up ophthalmoplegia had disappeared, and the patient had fully recovered. The possibility of a truly interdural location, particularly in cases of non-traumatic parasellar or clival haematomas, must be included in the differential diagnosis of posterior fossa extra-axial haemorrhages. MRI is the test of choice for diagnostic purposes.

Spinal cord lipoma without dysraphism in the infancy that extends intracranially. Case report and review of the literature.

BACKGROUND: Spinal intramedullary lipoma extending to the posterior fossa is very rare in children. We made a revision of the literature and report the diverse opinions and surgical procedures. CASE DESCRIPTION: We report the case of a 16-month-old male infant who was operated on in the Pediatric Neurosurgical Unit of our hospital; his clinical and surgical outcome are related. CONCLUSION: Intramedullary lipoma of the spinal cord with intracranial extension in infancy is a very rare pathology reported in the literature. Our patient was treated with decompression and subtotal removal; he had a critical postoperative course but was recovering slowly after that. Most authors prefer incomplete resection because these lesions do not have a clear-cut margin. Another neurosurgeon performed a decompression only, without resection. Some authors performed the surgical treatment before symptom progression. Another surgeon reported that the surgical indication is debatable when the neurologic manifestations are poor or absent. The surgical indication and the strategy for treatment are controversial and they depend on the clinical situations of the patients.

A case with prepontine (clival) arachnoid cyst manifested as trigeminal neuralgia.

Most cases of "idiopathic" trigeminal neuralgia are thought to originate from vascular compression of the trigeminal root entry zone. In this case, we describe a young man presenting with the symptoms of trigeminal neuralgia associated with a prepontine (clival) arachnoid cyst.

Intractable hiccups as a presenting symptom of Chiari I malformation.

INTRODUCTION: Hiccups as the only presenting symptom in neurosurgical practice is uncommon. CASE HISTORY: We report a case of a 22-year-old man who was evaluated for a 9-month history of intractable hiccups. He was diagnosed with a case of Chiari malformation type I. DISCUSSION: Surgical decompression improved the symptoms of the patient. The cause and pathogenesis of hiccups are discussed. CONCLUSION: Chiari malformation should be considered in patients with intractable hiccups, who are otherwise asymptomatic for any neurological problems.

Primary spontaneous CSF rhinorrhea through the clivus: possible etiopathology.

Primary spontaneous cerebrospinal fluid (CSF) rhinorrhea is rare. Only two such cases with a defect in the clivus have been previously reported in the world literature. The purpose of this report is not to discuss the operative approach or results but the etiopathogenesis of the defect at this very rare site. One patient had a defect in the posterior wall of the sphenoid sinus, just caudal to the dorsum sellae. In the other, a psuedomeningocele (thickened arachnoid outpouching) was found protruding into the sphenoid sinus through a defect in the middle of the clivus. Both cases were successfully managed with transsphenoidal surgery. Two additional cases of primary spontaneous CSF rhinorrhea through a defect in clivus are reported. The possible mechanism of the fistulae are discussed.

Radiologically atypical congenital posterior fossa dermoid cyst presenting late in life.

We report the case of a 74-year-old woman who presented with deterioration in gait, short-term memory loss and urinary incontinence. She had a past history of excision of a cervical dermal sinus tract at the age of 5 years. CT scan in 2004 revealed ventriculomegaly and an extremely hypodense ovoid structure lying in the midline low posterior fossa with calcification anteriorly. On MRI, the lesion was hypointense on T1-eighted and hyperintense on T2-weighted images, with incomplete suppression on fluid-attenuated inversion-recovery images and marked restriction on diffusion weighted images. Cerebrospinal fluid isotope study revealed non-communicating hydrocephalus. Posterior fossa crainectomy and removal of the lesion was undertaken. Pathological study revealed a dermoid cyst. Post-operatively, her hydrocephalus persisted and a ventriculo-atrial shunt was inserted with excellent functional recovery.

Cervicomedullary compression secondary to massive calcium pyrophosphate crystal deposition in the atlantoaxial joint with intradural extension and vertebral artery encasement.

BACKGROUND: Deposition of CPPD crystals occurs in the fibrous and hyaline cartilage of the joints and intervertebral disks of the spine. Half of patients known to have chondrocalcinosis had asymptomatic calcification in the odontoid region. The cases of 12 patients with a spinal cord syndrome secondary to CPPD deposition in the odontoid region were published in the literature. In all those cases, the mass lesion was extradural in location with good outcome after surgical decompression via the transoral route. CASE DESCRIPTION: We report on a rare case of large periodontoid CPPD deposition causing cervicomedullary compression, erosion of the overlying bone, and underlying dura with intradural extension and vertebral artery encasement. CONCLUSIONS: Calcium pyrophosphate dihydrate is a rare cause of cervicomedullary compression. Intradural extension of periodontoid CPPD has not been reported on.

Tentorial dural arteriovenous fistulas.

BACKGROUND: Tentorial dural arteriovenous fistula is uncommon but is a life-threatening lesion. We present our experience with 5 patients with TDAVFs, review the relevant literature, and present the rationale of our current management strategy. METHOD: The data of 5 patients with TDAVFs treated in Huashan Hospital, Shanghai, China, between June 2002 and May 2003 were reviewed retrospectively, including their illness history, neuroimaging, operation records, and follow-up data. RESULTS: There were 3 females and 2 males with ages from 25 to 52 years (average, 38 years). Clinical manifestations were acute SAH in 2 patients and progressive neurologic deficits in 3 patients. Magnetic resonance imaging and DSA were major diagnostic and follow-up modalities. All cases belonged to Borden classification type 3. A tentorial marginal type was present in 3 cases, a tentorial lateral type in 1 case, and a tentorial medial type in 1 case. Preoperative transarterial embolization was done in 3 patients. All patients underwent craniotomy with the coagulation of the fistulas and surrounding tentorial dura mater, and the disconnection of leptomeningeal venous drainage. The surgical approaches were via transanterior petrous approach in 3 cases, subtemporal intradural approach in 1 case, and unilateral occipital and transtentorial approach in 1 case. All patients had clinical improvement. There was no surgical mortality and morbidity. Postoperative DSA confirmed obliteration of TDAVFs in 3 cases; MRI demonstrated the thrombosis of venous aneurysm and disappearance of previous brainstem edema in 1 case, and partial thrombosis of venous aneurysm in another case. Follow-up study ranging from 2 to 3 years (average, 2.5 years) showed no recurrence, and all patients have resumed their normal activities. CONCLUSIONS: Tentorial dural arteriovenous fistulas are aggressive vascular lesions causing SAH and progressive neurologic deficits. Prompt diagnosis and definite treatment are mandatory. Obliteration of the fistulas and/or leptomeningeal venous drainage should be the goal of treatment. Microsurgical procedures with/without endovascular intervention are the best choice of treatment.

Disproportionately large communicating fourth ventricle with syringomyelia: case report.

A 13-year-old boy presented with syringomyelia associated with disproportionately large communicating fourth ventricle (DLCFV) manifesting as symptoms attributable to hydrocephalus and characteristic posterior fossa symptoms. Magnetic resonance imaging demonstrated remarkable dilation of the fourth ventricle and syringomyelia. Ventriculoperitoneal shunting completely resolved all symptoms as well as the ventricular and spinal cord abnormalities. Pre- and postoperative cine magnetic resonance imaging revealed the change of cerebrospinal fluid flow signal in the area of the foramen magnum. We concluded that the syringomyelia could be described as enlargement of the central canal with DLCFV.

Subdural effusions in the posterior fossa associated with spontaneous intracranial hypotension.

BACKGROUND: Misdiagnosis of spontaneous intracranial hypotension remains a problem, despite increasing recognition. METHODS: Three patients with spontaneous intracranial hypotension presented with typical findings on lumbar puncture, magnetic resonance (MR) imaging, and radioisotope cisternography. All patients showed subdural effusions in the posterior fossa on axial T2-weighted MR imaging. Axial MR images of 112 patients with other conditions were also screened for this finding. RESULTS: One of three patients had typical orthostatic headache, and the other two had continuous headache. The finding of subdural effusions in the posterior fossa on axial T2-weighted MR imaging disappeared after treatment. Similar findings were found in 14 of 112 patients with other conditions. Most of the patients were over 60 years old or had dementia or previous radiation therapy. CONCLUSIONS: Subdural effusions in the posterior fossa can be identified by T2-weighted axial MR imaging, and are useful for the diagnosis of spontaneous intracranial hypotension and for verifying the effectiveness of treatment.

Middle and posterior fossa aspergilloma.

BACKGROUND: Aspergilloma of the brain is a rare disease. Among its varied presentations, a solitary intracranial mass is very uncommon. A preoperative diagnosis of it is very difficult, but a perioperative squash smear/frozen section can identify the pathology. Because of its rarity in immunocompetent patients and the difficulty in preoperative diagnosis, we have illustrated this case and its presentation and management. METHODS: A 27-year-old man presented with an h/o right-sided weakness along with headache and ear discharge. A computed tomographic (CT) scan showed a large irregular, space-occupying lesion in the middle and posterior cranial fossa. He had a mastoidectomy done 3 years before for chronic suppurative otitis media. After a symptom-free interval of 1 year, he was investigated for severe earache on the same side. A CT scan at that time showed a space occupying mass in the right temporal bone and right inferior temporal lobe. A biopsy and histopathology of the lesion revealed a chronic granulomatous mass. He was started on antituberculous drugs and was on it for 7 months at the time of presentation. RESULTS: He underwent a suboccipital craniectomy and total excision of the mass. Postoperatively, his consciousness improved but began to deteriorate on the third postoperative day. A repeat CT scan showed hydrocephalus and total removal of the mass. An external ventricular drain was put and he was ventilated, but he died on the fourth postoperative day. Histopathology report came as aspergilloma. CONCLUSION: This report highlights the rare presentation of aspergilloma in an immunocompetent patient. It emphasizes the importance of suspecting this disease in such patients and the role of intraoperative squash smear preparations or frozen section in the diagnosis as routine diagnostic procedures that will help in early pharmacotherapeutic interventions in adjunct to surgery.

Neonatal posterior fossa haemorrhage associated with vacuum extractor.

We report one case of posterior fossa intracranial haemorrhage in a full-term Malay baby boy following vacuum assisted delivery. The patient, a term baby boy was delivered by a vacuum extraction and later developed signs of increased intracranial pressure 72 hours after birth. Computed tomography (CT) of the brain showed a posterior fossa intracranial haemorrhage with acute obstructive hydrocephalus. He was initially treated with isolated ventricular shunting which later caused an upward cerebellar herniation. An immediate suboccipital craniectomy for evacuation of cerebellar haematoma was performed which resulted in a gradual recovery.

Cerebral oxygen metabolism and blood flow in human cerebral ischemic infarction.

Fifteen patients with acute cerebral hemispheric infarcts have been studied with positron emission tomography and the oxygen-15 steady-state inhalation technique. Thirteen follow-up studies were also performed. The values of cerebral oxygen metabolism (CMRO2), cerebral blood flow (CBF), and oxygen extraction ration (OER) have been calculated for the infarcted regions, their borders, the symmetrical regions in contralateral cerebral hemispheres, and the cerebellar hemispheres. This study demonstrates that in the completed stroke there are thresholds for regional CMRO2 and regional CBF below which the general clinical outcome of the patients is usually poor. The ischaemic lesions invariably produce an uncoupling between the greatly decreased metabolic demand and the less affected blood supply, with very frequent instances of relative hyperperfusion. Remote effects of the hemispheric infarcts have been demonstrated, such as crossed cerebellar diaschisis and contralateral transhemispheric depression. The level of consciousness correlates with oxygen uptake and blood flow both in the posterior fossa and in the contralateral cerebral hemispheres. The follow-up studies of individual patients underline the high variability of metabolism-to-flow balance during the acute phase of the illness, and stress the need for more studies focused on repeated assessments of homogeneous patient populations.

Syringomyelia-Chiari complex: magnetic resonance imaging and clinical evaluation of surgical treatment.

Thirty patients with syringomyelia-Chiari complex who underwent posterior fossa decompression or syringosubarachnoid shunting were studied clinically and by magnetic resonance (MR) imaging to assess the changes in the syrinx and in their clinical picture after surgery. When symptoms of posterior fossa compression were present, posterior fossa decompression was performed; however, when symptoms of posterior fossa compression were absent, the choice of posterior fossa decompression or syringosubarachnoid shunting depended, respectively, on whether the syrinx was narrow or wide on MR imaging. At least 1 year after surgery, subjective improvement or arrest of disease was recorded in 73% of the patients. The present study suggests that: 1) the symptoms attributed to spinal cord damage have no significant relationship to the size of the syrinx on MR images; 2) the surgical techniques employed in this series (posterior fossa decompression or syringosubarachnoid shunt) were equally useful in inducing syrinx collapse; and 3) when posterior fossa decompression is performed, plugging of the obex is not necessary for syrinx collapse.

Neurophysiological monitoring of cranial nerves during posterior fossa surgery.

Intraoperative neurophysiological monitoring of cranial nerve functions in surgery for microvascular decompression and tumors of the posterior fossa is important for minimizing risk of permanent damage to the nerves. In particular, intraoperative BAEP and the EMG function of muscle innervated by trigeminal and facial muscle have been found useful. We report here our experiences with intraoperative monitoring of brainstem auditory evoked potentials (BAEP) and EMG recorded from muscles supplied by the trigeminal and facial nerves.