Posterior Fossa Mass Research Articles

Neonatal Movement Disorders

After completing this article, readers should be able to: 1. Delineate the characteristics that differentiate hyperkinetic neonatal movement disorders from neonatal seizures. 2. Describe the primary characteristics of and treatment for hyperekplexia. 3. Explain the relationship between gastroesophageal reflux and movement disorders in neonates. 4. Describe the primary ocular movement disorders in neonates. Neonates often exhibit paroxysmal behaviors that are nonepileptic in nature, such as oral-buccal-lingual movements, pedaling, stepping, and rotatory arm movements. The electroencephalogram (EEG) is of particular value for distinguishing these nonepileptic behaviors from subtle seizures. EEG and video-EEG studies in such movement disorders do not exhibit seizure discharges during the events. This distinction is important because nonepileptic events do not require treatment with anticonvulsants. Although the absence of surface ictal activity does not exclude entirely the possibility of seizures arising from deeper structures, it generally is accepted that these disorders are not epileptic. For the purposes of this review, we include common nonepileptic paroxysmal (episodic) movements that occur from birth to early infancy (onset between birth and 3 months of age). Many of these movement disorders may persist during infancy or early childhood. We do not discuss more persistent motor problems, such as spasticity, hypotonia, or myotonia. Also, disorders that occur after 3 months of age are not included. We have classified the movement disorders into two major categories: 1) hyperkinetic movements and 2) dystonic or extrapyramidal type of movements. Because the pathophysiologic mechanisms underlying neonatal movement disorders often are unknown, they are categorized on the basis of phenomenology, rather than presumed cause. Some of these disorders may have overlapping symptomatology. A third category encompasses “ocular movement disorders.” ### Jitteriness of the Newborn Jitteriness may be due to many factors, including metabolic disturbance, hypoxic-ischemic encephalopathy, drug withdrawal, hypoglycemia, and hypocalcemia. Although jitteriness may be mistaken for neonatal seizures, a distinguishing feature of jitteriness is that the …

Management strategies for treatment of the trapped fourth ventricle.

An isolated or trapped fourth ventricle (TFV) is an occasional, serious sequela of hemorrhagic, infectious, or inflammatory conditions of the central nervous system. The TFV usually occurs after successful shunting of the lateral ventricles. It may be heralded by delayed clinical deterioration after an initial period of symptomatic improvement. The typical clinical findings suggest an expanding posterior fossa mass lesion. Surgical treatments include CSF diversionary procedures as well as open and endoscopic approaches. Complications related to the treatment of the TFV are common and relate to catheter obstruction and cranial nerve or brainstem dysfunction. The author reviews the clinical features, pathophysiology, and available treatment options for the TFV, with special reference to complication avoidance and advances in ventriculoscopy and frameless stereotaxy. Treatment of the TFV remains a formidable challenge. However, prompt recognition and intervention may aid in the preservation of life and neurological function.

Dandy-Walker variant: Prenatal diagnosis by ultrasonography

The Dandy-Walker complex is a rare congenital intracranial malformation that comprises a spectrum of abnormalities of the posterior fossa which are classified as (a) Dandy-Walker malformation (cystic dilatation of the 4th ventricle, complete or partial agenesis of the cerebellar vermis and an enlarged posterior fossa) (b) Dandy-Walker variant (cystic posterior fossa mass with variable hypoplasia of the cerebellar vermis and no enlargement of the posterior fossa) and (c) Mega-cisterna magna (enlarged cisterna magna with normal cerebellar vermis and fourth ventricle). The prenatal sonographic diagnosis of the classic Dandy-Walker malformation is simple, however the definitive diagnosis of Dandy-Walker variant and Mega-cisterna magna is difficult before 18 weeks of gestation. This is because the sonographic appearance of normal cerebellum in the second trimester can resemble pathological anomalies as the posterior fossa structures are not established until then and the sonologist must exercise caution before reaching a final diagnosis of Dandy-Walker variant or mega-cisterna magna [1]. We report a case of Dandy-Walker variant which was diagnosed during routine antenatal ultrasonography at 22 weeks of gestation and subsequently confirmed by post natal CT scan of the brain.

Traumatic acute subdural haematomas of the posterior fossa: clinicoradiological analysis of 24 patients

We report 24 patients with a traumatic acute subdural haematoma of the posterior fossa managed between 1997 and 1999 at 8 Italian neurosurgical centres. Each centre provided data about patients' clinico-radiological findings, management, and outcomes, which were retrospectively reviewed. A poor result occurred in 14 patients (58.3%). Ten patients (41.7%) had favourable results. Patients were divided into two groups according to their admission Glasgow Coma Scale (GCS) scores. In Group 1 (12/24 cases; GCS score, > or =8), the outcome was favourable in 75% of cases. In Group 2 (12/12 cases; GCS score, <8), the outcome was poor in 91.6% of cases. Nineteen patients underwent posterior fossa surgery. Factors correlating to outcome were GCS score, status of the basal cisterns and the fourth ventricle, and the presence of supratentorial hydrocephalus. Multivariate analysis showed significant independent prognostic effect only for GCS score (P<0.05). acute posterior fossa subdural haematomas can be divided into two distinct groups: those patients admitted in a comatose state and those with a moderate/mild head injury on admission. Comatose patients present usually with signs of posterior fossa mass effect and have a high percentage of bad outcomes. On the contrary, patients admitted with a GCS of 8 or higher are expected to recover. In these patients the thickness of the haematoma (<1 cm) seems to be a guide to indicate surgical evacuation of the haematoma.

Long-term outcome of trigeminal neurinomas with modified classification focusing on petrous erosion

Background The authors present a retrospective analysis of 29 consecutive patients with trigeminal neurinomas. Modified classification based on the tumor distribution over petrous ridge is suggested to select the optimal surgical approach and to predict the outcome. Methods Preoperative computed tomography (CT) or magnetic resonance (MR) images were analyzed to measure a long diameter of tumor axis (LD), which divided into middle and posterior fossa and a width of the petrous erosion (PW) by the tumor on axial image. The tumors were classified into four groups (M, tumor confined to middle fossa; Mp, tumor mainly in middle fossa; M = P, tumor equally distributed into both middle and posterior fossa; Pm, tumor mainly in cisternal space of posterior fossa with slender, rarely round extension into Meckel’s cave), and extent of removal was compared between the groups. Long-term outcomes were based on recurrence-free survival. Results Total removal was achieved in 16 patients including stage operation (55%). Excluding three tumors, which underwent gamma knife for residual tumor, 8 of 10 subtotally removed tumors recurred at 50 months on average. The LD and PW are significantly different among the tumor types. The M = P type is the largest in both parameter, while the M type is the smallest in LD; Pm type is the smallest in PW, respectively. The tumors with equal or lager posterior fossa component (M = P and Pm type) were more difficult to remove totally by single attempt than those with smaller or nil posterior fossa mass (Mp and M type). Also, the corrected PW (PW over the tumor diameter of minor portion) shows a tendency to influence the extent of removal as the relatively narrow PW hindered the total removal. Conclusions Aggressive attempt for total removal using skull base approach is recommended, especially for those having dominant posterior fossa component and for those having relatively narrow PW.

Uncommon presentation of medulloblastoma.

Medulloblastoma commonly occurs in children as a midline posterior fossa mass arising from the vermis, which appears as a hyperdense, homogeneously enhancing mass on CT scan and is associated with the clinical profile of posterior fossa syndrome. This unique clinico-radiological pattern is considered 'typical', but then medulloblastomas do not follow the typical clinico-radiological pattern in a significant number of cases. Out of the 42 cases of medulloblastoma operated on at SGPGIMS from 1988 to 1998, 29 cases were retrospectively and 13 cases were prospectively studied to detect the atypical clinico-radiological features. The typical radiological feature of a hyperdense homogeneously enhancing mass was seen in only 23 of the 42 patients, while 5 patients had hypodense nonenhancing masses, 13 had cystic changes, and 6 patients had calcifications in their tumours. Three patients presented with tumours in a very unusual location, i.e. the cerebellopontine angle cistern. During follow-up, which ranged from a minimum period of 1 year to a maximum of 9 years, patients came back with metastases at very unusual sites. There were 5 cases of metastases in the frontal and subfrontal area (developed between 5 months and 5 years following surgery), and 1 patient developed a cervical intramedullary metastasis. Two patients developed abdominal metastases and ascites 2 years after definitive surgery and ventriculo-peritoneal shunting. Each of these 2 patients, however, had received a full course of craniospinal irradiation following surgery. Thus, we had a number of cases with an unusual clinical, radiological and metastatic pattern.

CT stereotaxy guided lateral trans-cerebellar programmable fourth ventriculo–peritoneal shunting for symptomatic trapped fourth ventricle

A trapped fourth ventricle is a rare clinico-radiological entity producing symptoms suggestive of a progressive posterior fossa mass lesion. It is mainly reported in children as a late complication of lateral ventricular shunting to relieve infantile post-meningitic or post-hemorrhagic hydrocephalus. Optional treatment of the trapped fourth ventricle remains controversial. Placement of fourth ventricular shunting via a conventional midline approach can be fraught with complications in about 40% of the patients. Authors report a successful CT Stereotaxy guided high pressure (80 mm H 2O) programmable fourth ventriculo–peritoneal shunting via a lateral trans-cerebellar approach in a 14-year-old girl with a trapped fourth ventricle, which occurred as a late complication of ventriculo-peritoneal shunting in her infancy. Her preoperative symptoms of raised intracranial pressure, bobble-head doll syndrome and bilateral abducens palsies completely improved following the surgery. Lateral trans-cerebellar stereotactic placement of the fourth ventricular catheter and the use of high-pressure (low flow) programmable shunt (to avoid complications associated with over drainage) are beneficial in some patients with trapped fourth ventricle.

Posterior Fossa Decompression and Clot Evacuation for Fourth Ventricle Hemorrhage after Aneurysmal Rupture: Case Report

Massive intraventricular hemorrhage due to aneurysmal rupture is associated with a dismal prognosis. An intraventricular clot causing fourth ventricle dilation can cause compression to the brainstem similar to other posterior fossa masses such as cerebellar hemorrhage or infarction. The presence of fourth ventricle dilation carries a very high risk of death within 48 hours. Neither ventricular drainage nor fibrinolytic infusion has been successful in eliminating clots of the fourth ventricle. Posterior fossa decompression and direct evacuation of the clot could have good results in relieving brainstem compression caused by the clot. A 45-year-old woman was admitted to our intensive care unit after experiencing an aneurysmal subarachnoid hemorrhage. The neurological examination at admission revealed that she was in Grade V according to the World Federation of Neurological Surgeons grading system, but brainstem reflexes were present. Computed tomographic scanning revealed a massive intraventricular hemorrhage, with fourth ventricle dilation caused by an intraventricular clot. Bilateral external ventricular drains were placed to relieve elevated intracranial pressure. Cerebral angiography revealed a 1-cm basilar tip aneurysm, which was embolized with Guglielmi detachable coils (Boston Scientific, Boston, MA) during the same procedure. Given the patient's poor neurological condition, it was decided that brainstem compression should be relieved. A posterior fossa decompressive craniectomy was performed immediately after coil therapy, with direct evacuation of the intraventricular clot. The patient experienced a clear improvement in the level of consciousness and has achieved a good neurological result at early follow-up. Dilation of the fourth ventricle by an intraventricular clot is a sign of brainstem compression that can be relieved by posterior fossa decompression and direct clot evacuation.

Extradural Endodermal Cyst of Posterior Fossa: Case Report, Review of the Literature, and Embryogenesis

Posterior fossa endodermal cysts are rare. They are located in the midline, in ventral or ventrolateral locations, or intrinsic to the neural axis. Accordingly, various theories of embryogenesis have been proposed. We report the first case of an extradural, dorsolaterally situated endodermal cyst. An adult male patient presented with a short history of headache and cerebellar ataxia. Neuroimaging revealed an extra-axial cystic posterior fossa mass. An entirely extradural cyst was found and was totally excised. Immunohistochemistry confirmed the diagnosis of endodermal cyst. The extradural, dorsal location of the endodermal cyst suggests gaps at the cranial end of the notochord causing ectodermal-endodermal adhesions during early gastrulation and the persistence of endodermal remnants in the dorsal mesenchyme of the blastemal cranium. The literature is reviewed, and proposed theories of embryogenesis are discussed.

Extradural Endodermal Cyst of Posterior Fossa: Case Report, Review of the Literature, and Embryogenesis

OBJECTIVE AND IMPORTANCE Posterior fossa endodermal cysts are rare. They are located in the midline, in ventral or ventrolateral locations, or intrinsic to the neural axis. Accordingly, various theories of embryogenesis have been proposed. We report the first case of an extradural, dorsolaterally situated endodermal cyst. CLINICAL PRESENTATION An adult male patient presented with a short history of headache and cerebellar ataxia. Neuroimaging revealed an extra-axial cystic posterior fossa mass. INTERVENTION An entirely extradural cyst was found and was totally excised. Immunohistochemistry confirmed the diagnosis of endodermal cyst. CONCLUSION The extradural, dorsal location of the endodermal cyst suggests gaps at the cranial end of the notochord causing ectodermal-endodermal adhesions during early gastrulation and the persistence of endodermal remnants in the dorsal mesenchyme of the blastemal cranium. The literature is reviewed, and proposed theories of embryogenesis are discussed.

Dural Cavernous Haemangioma with Bony Infiltration: Case Reports

We report the findings in a 5-year-old boy with headache, intermittent vomiting and blurred vision who was found to have an enhancing, dural based extra-axial posterior fossa mass. This was proven histologically to be a dural cavernous haemangioma with bony infiltration. These uncommon lesions may closely resemble meningioma on computed tomography (CT), magnetic resonance imaging (MRI) and angiography in terms of location, enhancement, bony changes and signal characteristics [1,2]. To our knowledge this is the first report of a dural cavernous haemangioma with bony infiltration as seen on CT and only the second in the literature [3].

Imaging features of posterior fossa neoplasms in children and adults

Masses in the posterior fossa may be divided into extra-axial and intra-axial lesions. Because of its multiplanar capabilities, improved soft-tissue resolution and contrast, and the absence of scanning artifacts related to the osseous skull base, which are frequently present on CT, MRI is the imaging modality of choice in evaluating lesions arising in the posterior fossa. It is the best means of critically localizing lesions and determining the extent of disease. Analysis of the signal characteristics of a lesion on multiple different imaging sequences (T1-weighted, T2-weighted, and enhanced images) may provide information about the tissue constituents within a mass/neoplasm, such as the presence of cellularity, necrosis, and hemorrhage. MRI is also useful in guiding localization for brain tumor biopsies and assists in planning radiation therapy. However, CT also plays an important role. CT is frequently the first imaging study performed in patients with posterior fossa masses who often present with nausea, vomitting, ataxia, and other signs of increased intracranial pressure. It is a quick, available, and relatively inexpensive study to assess neurological emergencies including hydrocephalus, hemorrhage, and herniation syndromes. In addition, it frequently provides complimentary information, such as the presence of calcification or bony remodeling (osteosclerosis or osteolysis), which MRI is less sensitive in detecting.

Intracranial malignant lymphomas: clinicopathological study of 26 autopsy cases.

We examined 26 autopsy-proven cases of intracranial malignant lymphoma (IML) in immunocompetent patients to determine the extent of neoplastic involvement of the central nervous system (CNS) and to evaluate the effects of radiation on the tumor and brain tissue. All tumors were identified as diffuse non-Hodgkin's lymphomas of B-cell origin. In six patients who had not received radiotherapy, the clinical course of the disease was short and extensive infiltration of the tumor was seen. The remaining 20 patients were treated with radiotherapy and had a longer survival time. Leptomeningeal involvement was common, but extensive subarachnoid proliferation of the tumor was seen in only two cases. The posterior, but not anterior, lobe of the pituitary was involved in 5 of 22 cases, and choroid plexus involvement was seen in 4 of 21. Direct invasion of the tumor into the spinal cord, which tended to occur in patients with posterior fossa masses, was observed in 5 of 21 cases. Following irradiation, coagulation necrosis was frequently found in the invading zone as well as in the tumor mass, and degeneration of the white matter was also seen. We suggest that IML can extensively infiltrate into the CNS, including the posterior lobe of the pituitary and spinal cord, and that radiation injury to the brain appears to occur relatively easily in this disease.

Neurosurgical outcomes in a modern series of 400 craniotomies for treatment of parenchymal tumors.

The goals were to critically review all complications resulting within 30 days after craniotomies performed for excision of intra-axial brain tumors relative to factors likely to affect complication rates and to assess the value of these data in predicting the risk of surgical morbidity, particularly for surgery in eloquent brain regions. Neurosurgical outcomes were studied for 327 patients who underwent 400 craniotomies for removal of intra-axial parenchymal brain neoplasms in a 21-month period. Tumors removed included gliomas (206 tumors) and metastases (194 tumors) located both supratentorially (358 tumors) and infratentorially (42 tumors). The major complication incidence was 13%, and the operative mortality rate was 1.7%. The overall morbidity rate was 32%, but more types of complications were considered than in previous studies. The major neurological morbidity rate was 8.5%. Based on pre- versus postoperative (at 4 wk) Karnofsky Performance Scale scores, 9% of patients deteriorated neurologically, 32% improved, and 58% showed no change. The median postoperative hospital stay was 5 days. Tumors were defined as Grade I, II, or III based on their location relative to brain function, and this tumor functional grade was the most important variable affecting the incidence of any neurological deficit. Patients with tumors in eloquent (Grade III) or near-eloquent (Grade II) brain areas incurred more neurological deficits than did patients with tumors in noneloquent areas (Grade I). Neither repeat surgery for recurrent disease nor extent of surgical resection affected outcome significantly. Although most tumors in this study, including those in eloquent regions, were removed by gross total resection, this did not lead to more major neurological deficits. Regional complications (at the surgical sites) and systemic complications (medical) were more prevalent among older patients (age >60 yr) with lower preoperative Karnofsky Performance Scale scores (< or = 50) and posterior fossa masses. We showed how our data can be used to predict the total risk of surgical morbidity for a given patient, to facilitate patient counseling and surgical decision-making. The finding that gross total resections could be performed in eloquent brain regions with an acceptable level of neurological impairment suggested that the mere presence of a tumor in eloquent brain does not automatically contraindicate surgery. Our results have practical risk-predictive value, and they should aid in the construction of subsequent outcome studies, because we have identified the key areas to monitor.

Cerebellar Mutism after Posterior Fossa Surgery

Six children, aged 6 to 12 years, who developed cerebellar mutism after surgery for a posterior fossa mass or as a result of trauma are reported from the Children’s Hospital, Los Angeles, CA.

Cerebellar mutism in children: Report of six cases and potential mechanisms

Cerebellar mutism is a rare finding associated with resection of posterior fossa tumors or cerebellar hemorrhages. We reviewed the medical records of six children, aged 6 to 12 years, who developed cerebellar mutism after resection of a posterior fossa mass or as a result of posterior fossa trauma. From 1989 to 1994, 210 children underwent posterior fossa resection at our institution, and four developed mutism (an incidence of 1.6%). All four patients had primitive neuroectodermal tumors. The fifth patient experienced trauma, and another patient had an arteriovenous malformation (AVM). In four children, hydrocephalus developed as a result of their tumor or AVM. Four developed cerebellar mutism 24 to 48 hours after surgery or trauma, and one developed cerebellar mutism 5 days after surgery, coincident with hydrocephalus. In one, mutism occurred after a second resection was performed for a recurrence of his posterior fossa tumor. Cerebellar mutism lasted 10 days in one patient and 2 to 8 weeks in the other four. Dysarthria was apparent in four patients during the recovery phase. We suggest trauma to the dentate nucleus and/or its outflow tract, the superior cerebellar peduncle, as a cause of reversible mutism. Because posterior fossa tumors are common in children, mutism should be recognized as an important side effect of surgery.

Endoscopic transsphenoidal resection of a large chordoma in the posterior fossa

Encouraged by an experience with endoscopic transsphenoidal pituitary surgery, an endoscopic transsphenoidal technique was applied in a patient with a large chordoma in the posterior fossa. The patient was a 40-year-old man with a two-year history of progressive ataxia, a memory disorder and emotional instability. A magnetic resonance (MR) scan of the brain revealed a midline posterior fossa mass measuring 4 cm in diameter located between the clivus and the brainstem. The basilar artery and its bifurcation were encased by the tumor and the brainstem was also distorted by the tumor. Obstructive hydrocephalus was treated previously with a ventriculoperitoneal shunt and fractionated external beam radiation treatment was given without histological diagnosis at another hospital. Subtotal resection of the tumor was achieved utilizing an endoscopic transphenoidal technique through the patient's nostril. The portion of the tumor located behind the basilar artery was not resected in order to protect the brainstem perforating arteries. The patient showed dramatic improvement of his symptoms postoperatively. Residual tumor located behind the basilar artery was treated by stereotactic gamma-knife surgery. This is the first reported case of a large posterior fossa chordoma being treated by an endoscopic transsphenoidal technique.

Endoscopic transsphenoidal resection of a large chordoma in the posterior fossa

The authors report their encouraging experience using an endoscopic technique for transsphenoidal surgery in a patient with a large chordoma in the posterior fossa. The patient was a 40-year-old man with a 2-year history of progressive ataxia, a memory disorder, and emotional instability. A magnetic resonance (MR) image of the brain revealed a midline posterior fossa mass measuring 4 cm in diameter located between the clivus and the brainstem. The basilar artery and its bifurcation were encased by the tumor, which also distorted the brainstem. The patient had been treated at another hospital for obstructive hydrocephalus with a ventriculoperitoneal shunt and he received fractionated external-beam radiation treatment, although no histological diagnosis was ever made. The authors achieved a subtotal resection of the tumor through the patient's nostril using an endoscopic transsphenoidal technique. The portion of the tumor located behind the basilar artery was not resected to protect the brainstem perforating arteries. The patient showed dramatic improvement of his symptoms postoperatively. Residual tumor located behind the basilar artery was treated by stereotactic gamma knife surgery. This is the first reported case of a large posterior fossa chordoma treated by an endoscopic transsphenoidal technique.

Mutism and Pseudobulbar Symptoms after Resection of Posterior Fossa Tumors in Children

MUTISM AND A variety of other neurobehavioral symptoms have been reported anecdotally after the removal of posterior fossa mass lesions. To determine the incidence and clinical spectrum of this syndrome, a detailed review was performed of patients undergoing resection of infratentorial tumors at our institution during the last 9 years; 12 of 142 patients (8.5%) manifested this syndrome, the largest series of such patients reported to date. Each child had a lesion that involved the vermis; seven had medulloblastomas, three had astrocytomas, and two had ependymomas. The incidence among children with vermian neoplasms was 13%. Ten children underwent division of the inferior vermis during tumor resection, and three had a superior vermian incision; one child underwent both superior and inferior vermian incisions. In 10 children, mutism developed in a delayed fashion postoperatively. The speech disturbance was associated with poor oral intake in 9 children, urinary retention in 5, long-tract signs in 6, and bizarre personality changes, emotional lability, and/or decreased initiation of voluntary movements in all 12. Neuropsychiatric testing, performed in seven children, confirmed impairments not only in speech but also in initiation of other motor activities. Ten children regained normal speech, bladder control, and neurological functioning, other than ataxia and mild dysarthria, within 1 to 16 weeks; two children had significant residual deficits. Characteristically, affect and oral intake returned to their preoperative baseline before the speech difficulties began to resolve. A detailed radiological review of these cases in parallel with 24 cases of vermian tumors without mutism identified only one factor that was significantly associated with the mutism syndrome, bilateral edema within the brachium pontis (P < 0.01). Neither the size of the tumor nor the length of vermian incision was associated with the development of mutism. The clinical features of this syndrome in the context of these imaging findings suggest that the mutism syndrome results from transient impairment of the afferent and/or efferent pathways of the dendate nuclei that are involved in initiating complex volitional movements. The clinical courses of our patients are presented and compared with those of similar cases in the literature in an attempt to evaluate the validity of this hypothesis.

Continuous venovenous hemodialysis

Hemodialysis and peritoneal dialysis are the main renal replacement therapies for patients with acute renal failure. These patients are often unable to tolerate drastic fluid shifts and other complications of conventional dialysis. Continuous hemodialysis, however, provides protection from the hemodynamic consequences and osmotic stressors of conventional dialysis and is rapidly becoming the treatment of choice for critically ill patients. We present a case in which a patient with a spontaneous cerebellar hemorrhage developed acute renal failure. Surgical evacuation was not an option. Clinical management included the use of continuous venovenous hemodialysis, which is described in the setting of a patient with a posterior fossa mass. The risks of anticoagulation, hemodynamic instability, and development of dialysis disequilibrium syndrome are discussed.