Meningiomas are slowly growing neoplasms thought to arise from meningothelial cells found within arachnoid granulations. The majority of meningiomas are supratentorial, with a large number located along the convexities, only about 10% occur in the posterior fossa. Approximately 5% occur along the cerebellar convexity, 2 to 4% at the tentorium cerebelli, and 2 to 4% within the cerebellopontine angle.¹ Most meningiomas compress and protrude into the underlying brain without true invasion. True invasion implies penetration of the pial membrane. . According to 2007, WHO criteria², meningiomas are classified as benign (gradeI), atypical (grade II), or anaplastic/malignant (grade III), which are further subclassified into

• Benign (Grade I) – (90%) – meningothelial, fibrous, transitional, psammomatous, angiomatous,microcystic,secretory,lymphoplasmacyte- rich,metaplastic
• Atypical (Grade II) – (7%) – chordoid, clear cell,
• Anaplastic/malignant (Grade III) – (2%) – papillary, rhabdoid,

The three most common histologic subtypes are the meningothelial (syncytial), transitional, and fibroblastic meningiomas^3,4. Posterior fossa meningioma was classified according to their location in the posterior fossa into cerebellopontine angle, convexity, clival, petroclival, tentorial, jugular foramen, foramen magnum and unclassified .⁵There may be various clinical presentations of posterior fossa meningioma depending on their location. Depending on the location, different surgical procedures can be used like retrosigmoid, subtemporal, translabyrinthine and transcondylar approaches .^6-8

Aim of the study

To find out clinical presentations, locations, surgical approaches, outcomes and histological types in posterior fossa meningioma.

This is a prospective observational study from march 2022 to September 2024 conducted in patients who were admitted to department of Neurosurgery, SCB Medical College & Hospital and were diagnosed as case of posterior fossa meningioma based on clinical examination and preoperative CT and MRI brain with contrast. A Performa was made for patients who were included in the study, in which details of the patient regarding age, sex, clinical symptoms and signs, MRI findings, surgical approaches, histopathological diagnosis and postoperative complications were documented. Postoperatively, CECT brain was done in all patients.

To describe the results,number and percentage were used.

TABLE-1GENDER

In this study, out of 30 patients,20 were females and 10 were males.

TABLE-2

AGE DISTRIBUTION

The most common age group affected were 45-54 years(33.3%) followed by 55- 64(26.6%).Only 2 patients were above 65 years.

TABLE-3

CLINICAL PRESENTATION

In this study, ,most patients (80%) complained headache as their primary complaint. Most common cranial nerve involved was trigeminal nerve presenting as decreased sensation along trigeminal nerve distribution(53.3%)

.Cerebellar manifestations like ataxia, dysmetria present in 9 cases(30%).

TABLE-4

LOCATION

Cerebellopontine angle meningioma occurred in 10 cases(33.3%). This was the most common location of the posterior fossa meningioma in this study.

Cerebellar convexity location occurred in 23.3% of cases, followed by tentorial meningioma (20%), petroclival(13.3%) and lastly by foramen magnum meningioma (10% ).

TABLE-5HISTOLOGIAL SUBTYPES

Fibrous and transitional subtypes represented the most common subtype (33.3% each) followed by the meningothelial subtype (26.6%) in this study. The least common was the atypical type (6.6%).

TABLE-6 SURGICAL APPROACHES

Retrosigmoid approach was the most commonly used approach (60% of cases). Suboccipital craniotomy was done in 7 cases. Subtemporal approach was done for two cases of petroclival meningioma. Farlateral approach was utilized for 2 cases of foramen magnum meningioma.Midline suboccipital with c1

laminectomy approach was used in one patient with foramen magnum meningioma .

TABLE-7

EXTENT OF RESECTION

60 % of cerebellopontine angle tumors were removed completly. None of the four petroclival meningioma cases were removed totally . Four tentorial meningioma were removed totally and rest two removed partially.All convexity meningioma cases removed completly. The two foramen magnum meningioma cases were removed partially, while one foramen magnum meningioma case was removed totally .

TABLE-8

POSTOPERATIVE COMPLICATIONS

The most common postoperative complication encountered one was new or worsening cranial nerve palsy present in 9 cases(30%).Altered sensorium from disoriented to stuporous ,who were preoperatively normal, found in 7 cases 23.3%). Postoperative CSF leak occurred in 4 cases (13.3%) . Death occurred in only 2 cases(6.6%) .

FIG-1,2- T1 contrast saggital and T1 contrast coronal image of right petroclival meningioma

FIG-3-Post operative CT scan of the above case operated by right subtemporal approach ,subtotal excision done.

FIG-5

FIG-4

FIG-6                                                                                                          

FIG-4,5- T1 contrast coronal & T1

contrast saggital MRI showing right cerebellopontine meningioma ,FIG-6 -Post operative CT scan showing gross total excision of the same case

FIG-7,8- T1 contrast coronal & saggital MRI showing right cerebellar convexity meningioma

FIG-9- Post op CT scan showing after suboccipital paramedian approach, grosstotal excision of tumor done

Meningiomas are the most frequent CNS tumor in adults.10% of all intracranial meningiomas arise in posterior fossa. Sekhar and Wright classified these tumors according to their anatomical origin.5 We conducted a prospective study from march 2022 to September 2024 in posterior fossa meningioma patients who were operated and then follow up done upto 1 year.

Total patients included in this study were thirty, out of which 20 were females and 10 were males, which makes a female to male ratio 2:1.Most studies in literature on meningioma show female predominance. William T. Couldwell reported 40 males and 69 females in a ratio of 1:1.72 in his study about petroclival meningioma .9-11

In our study, the youngest patient reported was 32 year old female and the oldest patient was 70 year male. The most common age group affected were 45-54 years(33.3%) followed by 55-64(26.6%).Only 2 patients were above 65 years(TABLE-2). Data from the Central Brain Tumor Registry of the United States (CBTRUS) revealed that an increasing risk with age.12 William T. Couldwell in his series of 109 cases having petroclival meningioma operated, the age ranged from 25 to 75 years with a mean of 51 years13-15, which is similar to our study.

Clinically, headache(80%) was the most common symptom complained by patients in our study, mostly in the suboccipital region. This is because of the location of the tumor in the posterior fossa and causing obstructive hydrocephalus. 21 patients had cranial nerve involvement, out of which trigeminal nerve involvement in the form of decreased sensation in one half of the face as compared to other half in trigeminal nerve distribution was present in 16(53.3%) cases, mild to moderate hearing loss was dictated by audiometry in 8 cases, facial palsy in 10 cases and lower cranial nerve palsy present only in 4 cases. Blurring of vision due to raised ICP was present in 6 cases(20%).Symptoms and signs due to cerebellar compression either due to direct compression of cerebellum or as a result of compression of cerebellar pathways to brain stem was present in present in 9 cases(30%)(TABLE-3) . In his study about posterior fossa meningioma ,Fabio Robert et al reported that the most common presenting symptoms were disturbance of gait (44%) and headache (50%) and the most common neurological signs on admission were cranial neuropathies.16

The most common location of the posterior fossa meningioma in this study was Cerebellopontine angle meningioma ,which occurred in 10 cases(33.3%). The second most common location was cerebellar convexity present in 23.3% of cases, followed by tentorial meningioma (20%), petroclival(13.3%) and lastly by foramen magnum meningioma (10% ) (Table 4). Roberti F. et al. reported petroclival (110 cases), foramen magnum (21 cases),cerebellar hemispheric, lateral tentorial (14 cases), cerebellopontine angle (9 cases), and jugular foramen (7 cases) in his experience in 161 cases of posterior fossa meningioma.5 30% posterior fossa meningioma were present in CP angle region and 20% in Petroclival region in classical series of Yassargil et al.17

In our study,fibrous and transitional subtypes found to be the most common subtype (33.3% each) followed by the meningothelial subtype (26.6%). The least common was the atypical type (6.6%) (Table 5) . N.Ianovici et al reported that grade I meningioma occurred in 82% of cases,grade II in 11% of cases, while grade III occurred in 5% of cases and the most common histological subtypes were fibrous and psammomatous in his study of posterior fossa meningioma .18-21

Retrosigmoid approach was the most commonly used approach (60% of cases) in this study,as this approach is familial to neurosurgeons ,suitable for all sized tumor and provides a wide exposure of all CPA structures. Suboccipital approaches were used in 7 cases. Subtemporal approach for petroclival meningioma was done in 2 cases. Farlateral approach was utilized for 2 cases of foramen magnum meningioma.Midline suboccipital with c1 laminectomy approach was used in one patient with foramen magnum meningioma .

The key to successful removal of posterior fossa meningioma are adequate craniotomy, early devascularization, debulking of tumor and not breaching arachinoid plane but total excision can not be possible in case of difficult location of tumors ,tumors found adjacent to or engulfing vital structures .In 60% of cerebellopontine angle meningiomas, tumor was gross totally excised as they were found posterior to internal auditory meatus. Subtotal excision of tumor done in all 4 cases of petroclival meningioma as the tumors were deep seated and to avoid injury to neurovascular structures or brainstem. Complete removal of tumor done in all cases of cerebellar convexity meningioma as they were superficially located. Four tentorial meningioma were removed totally and rest two removed partially. The two foramen magnum meningioma cases were removed partially, while one foramen magnum meningioma case was removed totally (Table 7).Overall, we had 19 cases (63.3%) which were removed completely.Lobato et al ,in his 80 cases of posterior meningioma had acheived gross total excised of tumor in 62.5% cases, which was similar to our study.22

Post operatively, the most common complication encountered in this study was new or worsening cranial nerve palsy ,which was present in 9 cases(30%),6 patients had worsened facial palsy, 1 patient developed facial palsy,who had preoperatively normal facial nerve function.Five patients improved after few months on follow up but in two patients, it did not improve In 3 patients, lower cranial nerve palsy developed in the form of nasal regurgitation of food, dysphagia .They were kept on ryles tube feeding initially, later improved after few months . 7 patients(23.3%) had altered sensorium from disoriented to stuporous in postoperative period . This was due to post operative edema, that was managed with steroids,improved in 4 cases but three cases had brain stem injury, which was evident on post operative scan ,so the deficit was permanent. Wound Infection was present in four cases ,which were superficial infections that resolved with antibiotics and daily dressing. In 4 cases (13.3%) ,CSF leak was present ,that responded well to oral acetazolamide . Roberti F,in his series, had a postoperative CSF leak in 22 cases (13.6%) . Only 2 cases(6.6%) died postoperatively, in 1st case death occurred due to aspiration pneumonia and septisemia and the other one, due to brainstem infarction and seizure,mostly due to injury to blood vessals and both cases were petroclival meningiomas(Table 8). Lobato et al,in his series, had a postoperative mortality of 6.2% ,which was similar to our study.22

Due to close proximity to cranial nerve and vessals, safe excision of posterior fossa meningioma is challenging. The simplicity and familiality of retrosigmoid approach to neurosurgeons make it the most commonly used procedure for used for cp angle meningioma, cerebellar convexity meningioma,lateral tentorial meningiomas and some of petroclival meningiomas. Petroclival meningioma is associated with high morbidity and mortality risk.

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