Girish Menon

Intratumoral Microhemorrhages on T2*-Weighted Gradient-Echo Imaging Helps Differentiate Vestibular Schwannoma From Meningioma

BACKGROUND AND PURPOSE: Vestibular schwannomas (VS) may be difficult to differentiate from cerebellopontine angle (CPA) meningiomas. Demonstration of microhemorrhages in VS on T2*-weighted gradient-echo (GRE) sequences may have potential value to differentiate VS from CPA meningiomas. Materials and METHODS: In this prospective study of 20 patients, MR imaging was performed with T2*-weighted GRE in addition to all basic sequences. Histopathologic examination was performed after surgery. Intratumoral hemosiderin was confirmed by pigment staining. RESULTS: There were 15 patients in the VS group with 16 VS and 5 in the meningioma group with 5 posterior fossa meningiomas. Fourteen of the 16 VS and all 5 meningiomas were treated surgically and were confirmed on histopathologic examination. T2*-weighted GRE identified microhemorrhages on T2*-weighted sequence in 15 (93.75%) of the 16 VS. CT excluded calcification in all VS. T2-weighted turbo spin-echo (TSE) and fluid-attenuated inversion recovery (FLAIR) images recognized microhemorrhages in 2 cases. Pigment staining confirmed hemosiderin in all 14 surgically treated VS, and none of the meningiomas showed microhemorrhages on MR imaging. For the detection of microhemorrhages, T2*-weighted GRE showed a sensitivity of 93.8%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 83.3%. The sensitivity of T2 TSE and FLAIR for microhemorrhage was 12.5%. The Fisher exact test showed a statistically significant difference in the differentiation of VS from meningioma on the basis of detection of microhemorrhages (P < .01). CONCLUSION: Most VS demonstrate microhemorrhages on T2*-weighted GRE. This finding is useful to differentiate VS from CPA meningiomas. T2*-weighted GRE should be used as a basic sequence to evaluate CPA tumors. Identification of microhemorrhages may have the potential to assess the aggressive biologic behavior of VS.

Adult medulloblastoma: clinical profile and treatment results of 18 patients.

The objective of this article is to examine the clinicoradiological features and surgical outcomes of adult patients (>16 years) with medulloblastoma. An attempt was made to identify the predictors of poor outcome and assess patterns of relapse and to compare these with pediatric medulloblastoma. Retrospective case record analyses were performed on 18 adults (>16 years) and 79 children (<16 years) operated upon after January 1990, who had at least 5 years of follow-up. The following variables were assessed by bivariate analyses: age, location of the lesion, brainstem invasion, extent of excision and histological subtype. Statistical analysis was performed using chi-square test, Fischers exact test and Students t-test. Results revealed there was no gender preference. The tumor was located in the vermis in 12 patients (66.6%) and in the cerebellar hemisphere in six (16.6%). Calcification was observed in two cases (11.1%) and hydrocephalus was seen in six (33.3%). MRI evidence of brainstem infiltration was seen in three patients (16.6%). Total excision was achieved in 13 cases (72.2%), near total excision in four (22.2%) and subtotal excision in one. Major complications included fresh cranial nerve deficits in four patients (22.2%), hemiparesis and gait unsteadiness in three (16.6%), mutism in one and meningitis in two. All patients underwent adjuvant radiotherapy in the form of craniospinal irradiation with a posterior fossa boost. On follow-up, 11 patients (61.1%) were observed to have recurrence and all were located in the posterior fossa. All 11 subsequently underwent chemotherapy. Two patients had re-operation for residual/recurrent lesions causing raised intracranial symptoms. Five-year follow-up data showed that 10 patients (55.5%) were alive, five (27.7%) had died while three (16.6%) were lost to follow-up. In spite of recent advances in management, patients with medulloblastoma still have a poor prognosis. However, adults fared better than children. Vermian location had a better outcome in adults, but not in children. Desmoplastic variant histology was not observed to be a significant prognostic factor in the adult group while brain stem invasion carried a poor prognosis.

Choroid plexus tumors: an institutional series of 25 patients.

PURPOSE Choroid plexus tumors (CPT) are rare neoplasms that pose considerable treatment challenges. This study reviews a single institutes experience with 25 patients of CPT and attempts to contribute to the general body of knowledge on CPT. MATERIALS AND METHODS A retrospective analysis of the case records of 25 patients operated for CPT since January 1998 and having a minimum of 1 year follow-up. RESULTS The study group included 12 (48%) cases of choroid plexus papilloma (CPP), 09 (36%) cases of choroid plexus carcinoma (CPC) and 4 cases of atypical CPP. The mean age at presentation was 18.6 years (range, 6 months to 54 years; SD, 18.7) and a male preponderance was noted (17:8). Raised intracranial pressure was the commonest presenting symptom (72%). The tumors were distributed as follows: lateral ventricle (16; 64%), fourth ventricle (5; 20%), fourth ventricle with cerebellopontine angle extension (3; 12%), and third ventricle (1; 4%). A complete surgical excision was achieved in 11 cases of CPP and 8 cases of CPC. Operative complications include pneumocephalus (40%), focal deficits (36%), subdural effusion (32%), and persistent hydrocephalus requiring shunt (24%). All patients with CPP had a good outcome at the end of a mean follow-up of 5.4 years, whereas the median survival for patients with CPCs who underwent a subtotal resection with adjuvant therapy was 36 months. CONCLUSION CPTs include a spectra ranging from CPP to CPC. Radiologic and histologic characterization of these tumors is difficult and newer immunohistochemical and genetic studies should be done to differentiate them from each other. Total excision offers a good prognosis and should be attempted for all forms of CPTs. CPPs carry a good prognosis, and adjuvant therapy is not indicated even after partial excision. CPCs and atypical CPCs carry a poor prognosis, and adjuvant therapy improves survival marginally after total excision. Spinal drop metastases are common for CPC and screening of the spine for possible metastasis should be part of the routine preoperative and postoperative investigation protocol.

Telovelar approach: technical issues for large fourth ventricle tumors

ObjectsFourth ventricle is conventionally accessed via resection of the part of the vermis for total excision of the tumors at the expense of significant morbidity. Numerous avenues have been identified to minimize the morbidity; some of which include transforaminal, subtonsillar, telovelar approaches, etc. These approaches are devised on the basis that accurate dissection along the natural avascular planes will avoid injury to the important structures in this area minimizing morbidity. We attempt to emphasize the technique of telovelar approach and the problems encountered while employing this technique for excision of large fourth ventricle tumors.Materials and methodsFifteen patients with fourth ventricle tumors were operated during January to September 2005 at Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, India. Fourteen of these cases were medulloblastomas, and one was ependymoma. All the patients were operated in prone oblique position via telovelar approach.ConclusionClear understanding of the normal anatomy will help in meticulous dissection and will result in reduced morbidity. Significant incidence of postoperative ataxia and mutism is seen with this approach in large tumors, and this can be avoided by staged dissection of the uvulotonsillar cleft.

Factors predicting the need for cerebrospinal fluid diversion following posterior fossa tumor surgery in children.

Background: No consensus exists regarding the management of hydrocephalus in children with posterior fossa tumors before, during or after surgery. In the present study we analyze the factors that predispose to persistent hydrocephalus and the need for a postoperative cerebrospinal fluid (CSF) diversion procedure. Methods: Pediatric patients who underwent surgery for posterior fossa tumors with hydrocephalus at our hospital were reviewed to evaluate the need for a postoperative CSF diversion procedure. Patients having undergone CSF diversion preoperatively were excluded from the study group. The case records of 84 patients were reviewed. The factors evaluated included age at diagnosis, duration of symptoms, severity of preoperative hydrocephalus, tumor size, tumor location, tumor histology, extent of tumor resection and postoperative complications that could be related to CSF circulation disorders. Results: At the time of presentation, 80/84 (95.2%) patients had symptomatic hydrocephalus; 25/84 (29.8%) patients required a CSF diversion procedure in the postoperative period. Children presenting with symptom duration of less than 3 months had a significantly higher requirement for postoperative CSF diversion in comparison to those with longer symptomatology (p = 0.016). Evan’s index and frontal and occipital horn ratio on preoperative imaging were found to correlate closely with the need for postoperative shunt (p = 0.001 and p < 0.001, respectively). The requirement for shunt was statistically higher in patients with midline tumors in comparison to laterally placed lesions (p = 0.04) and in children with medulloblastoma (p < 0.001) and ependymoma (p = 0.016) as the tumor subtypes. Children who underwent intraoperative external ventricular drainage (EVD) had a shunt insertion rate of 39.6% compared with 16.7% of those who did not have an EVD (p < 0.001). Patients with meningitis and pseudomeningocele in the postoperative period had a statistically significant higher risk of shunt requirement (p = 0.008 and p = 0.016, respectively). The mean age at diagnosis and the extent of tumor resection did not correlate with the need for CSF diversion. Conclusion: The fact that less than one-third of patients require a CSF diversion after posterior fossa tumor resection refutes the role of prophylactic endoscopic third ventriculostomy. Awareness regarding the factors that can predict persistent postoperative hydrocephalus is essential for the surgeon during patient counseling and surgical planning, and also in deciding the intensity of postoperative clinical and radiological monitoring.

Meningiomas of the lateral ventricle - a report of 15 cases.

Lateral ventricular meningiomas are rare tumours that pose considerable surgical challenge. This study attempts to analyse some of the important clinical features of these tumours and review technical considerations in surgery for lateral ventricular meningiomas. A retrospective analysis of the case records of patients with lateral ventricular meningiomas operated in our institute since 1998 with a minimum of one year follow up was done. The variables analysed included age, sex, clinical presentation, imaging characteristics, histopathology and operative details. Outcome was analysed using the Glasgow outcome score (GOS). Fifteen patients with a mean age of 40.6 years formed the study group. A female preponderance was observed (M:F 5:10). Raised intracranial pressure was the predominant symptom at presentation (10/15; 66%) followed by visual field deficits (6/15; 40%) and contralateral motor deficits (5/15; 33.3%). One patient presented with evidence of intratumoural bleed. The tumour was on the right side in 7 patients and on the left side in 8 patients. The lesion was located in the trigone of the lateral ventricle in 13 patients and in the body of the ventricle in two. The tumours were excised through a parietooccipital approach in 11 (73.33%) patients and through a middle temporal gyrus approach in 4 (26.66%).The tumour recurred in 2 patients, both tumours being histologically fibroblastic variants. Fresh operative complications included motor deficits in 3, contralateral homonymous hemianopia in 2, dysphasia in 1, refractory seizures in 2 and loculated hydrocephalus in one. We had no operative mortality. At last follow-up for 10 patients were in GOS 5, two were in GOS 4 and three in GOS 3. Lateral ventricular meningiomas are difficult tumours to operate. Total surgical excision through a superior parietal lobule or middle temporal gyrus approach is possible in most cases with minimal morbidity.

A single institution series of cavernomas of the brainstem

We retrospectively analyzed a series of patients with brainstem cavernomas of the medulla, pons, or midbrain to attempt to define the natural history, indications for surgery, and outcome after surgical resection. Between 1993 and 2008, 52 patients with cavernomas of the brainstem presented to our institute and were managed either surgically or conservatively. Twenty-three patients underwent surgical excision using standard skull base approaches. Outcomes were correlated to the number of preoperative hemorrhages, location of the cavernoma, timing of surgery in relation to the hemorrhage and the preoperative neurological status. Nine patients improved after surgery, 12 deteriorated and two died. In the conservatively managed group, 15 patients had a good outcome, 11 deteriorated and one died. Multiple hemorrhages, poor preoperative neurological status and surgery during the acute phase were predictive of the surgical outcome. Excision of brainstem cavernomas should be considered in patients with symptomatic hemorrhages whose lesions approach the pial surface. Patients with minimal stable neurologic deficits without recurrent bleeds should be managed conservatively.

Long term outcome in surgically treated posterior fossa epidermoids

OBJECTIVES To study posterior fossa epidermoids treated surgically at our institute and to compare their long term outcome with respect to extent of surgical decompression. MATERIALS AND METHODS Retrospective analysis of 50 cases of posterior fossa epidermoid surgically treated at our institute between 1997 and 2007. RESULTS The mean duration from onset of symptoms to surgery was 2.5 years. Patients with cerebellopontine angle (CPA) epidermoids presented predominantly with trigeminal neuralgia (35%) and hearing loss (29%) while patients with fourth ventricle epidermoids had features of raised intracranial pressure (ICP) and gait ataxia (69.2% each). The rate of recurrence was 9% in tumors considered totally removed and 93% in those subtotally removed. Of the 17 patients with recurrences, 3 (7.9%) underwent a second operation. The mean duration of follow up at first recurrence was 9.3 years. CONCLUSION Based on our experience, the rate of recurrence is significantly higher after subtotal removal as compared to total removal of epidermoids on long-term follow up. Symptomatic recurrence requiring re-exploration is evident only after a long duration (∼10.9 year) following primary surgery. Hence, total removal without producing new neurological deficits should be the standard goal when operating on posterior fossa epidermoid cysts.

Symptomatic posterior fossa and supratentorial subdural hygromas as a rare complication following foramen magnum decompression for Chiari malformation Type I.

Symptomatic subdural hygroma due to foramen magnum decompression for Chiari malformation Type I is extremely rare. The authors present their experience with 2 patients harboring such lesions and discuss treatment issues. They conclude that the possibility of subdural hygromas should be considered in all patients presenting with increased intracranial tension following foramen magnum decompression for Chiari malformation Type I. Immediate neuroimaging and appropriate surgical intervention provides a good outcome.

Advanced magnetic resonance imaging with histopathological correlation in papillary tumor of pineal region: report of a case and review of literature.

Papillary tumors of the pineal region are recently described as rare mass lesions with limited literature available on their natural history and imaging features. Magnetic resonance imaging (MRI) including perfusion, diffusion, and spectroscopic features were described in an 18-year-old girl with papillary tumor of pineal region. A well-defined, T1 hyperintense and contrast-enhancing mass lesion was noted in pineal region with few cystic spaces within. Solid portion of lesion showed minimal diffusion restriction with average apparent diffusion coefficient of 0.812 Χ 10 -3 mm 2 /s; on MR spectroscopy elevated myo-inositol peak with reduced N-acetylaspartate and elevated choline in the tumor. On perfusion study there was significantly high relative cerebral blood volume (rCBV) (6-9 times) and relative cerebral blood flow (rCBF). Our findings agree with previous descriptions of cystic areas with T1 hyperintense appearance of this tumor but very high level of tumor perfusion, diffusion restriction, and presence of myo-inositol peak are important imaging findings and may correlate with the recent reports of high tumor recurrence in these cases.