meningiomas account for 1320% of all intracranial tumors and of these 0.53% occur in intraventricular location . of the intraventricular meningiomas ,
clinical features and imaging are not characteristic to identify these lesions preoperatively , and most of them are thought to be some different tumor .
the importance of preoperative diagnosis lies in predicting the consistency and vascularity of tumor , which needs to be removed through narrow corridors to the fourth ventricle . here
, we discuss two cases harboring a primary fourth ventricular meningioma , which was surgically excised successfully .
a 50-year - old male had a headache and swaying while walking since 8 months and had developed diplopia on looking to the right side . on examination
computerized tomography ( ct ) scan showed an iso - hyperdense mass lesion in the fourth ventricle which was heterogeneously enhancing on contrast .
magnetic resonance imaging ( mri ) showed a t1 and t2 isointense heterogeneously enhancing mass lesion with areas of nonenhancing cavities .
the fourth ventricular floor appeared to be free from the lesion [ figure 1a  d ] . with this
( a ) t2-weighted image showing a heterogenous isointense intra fourth ventricular mass , ( b ) the lesion is isointense on t1-weighted imaging , ( c and d ) the lesion is enhancing on contrast administration , and it has multiple lobulations and is entirely inside the fourth ventricle .
( e and f ) contrast enhanced axial magnetic resonance imaging of and sagittal computed tomography , respectively of case 2 and ( g ) a postoperative computed tomography showing complete excision the patient underwent midline suboccipital craniotomy , telovelar approach , and excision .
lesion was located in the fourth ventricle toward the right displacing the vermis to left , entirely intraventricular , attached to the choroid plexus , and posterior inferior cerebellar artery feeders were seen , during surgery supplying the lesion , which was coagulated and removed .
histopathological examination of the lesion led to the diagnosis fibroblastic meningioma with brain invasion , who grade ii [ figure 2 ] .
photomicrograph showing interlacing fascicles of meningothelial cells on hematoxylin - eosin staining ( a ) , expression of epithelial membrane antigen ( b ) , and high mib-1 labeling ( c ) , on immunoperoxidase ( magnification = scale bar ) a 47-year - old female presented with a headache and neck pain of 1-year duration along with gait disturbance and recurrent falls of 4-month duration . on examination , she had features suggestive of papilledema .
mri of the brain showed a predominantly intra fourth ventricular mass with extension into the cerebellomedullary cistern .
it was isointense on t1 , iso to hyperintense on t2 with homogenous contrast enhancement .
there was no clear , identifiable plane between the lesion and fourth ventricular floor in mri [ figure 1e and f ] . in view , that the lesion was located a bit laterally and easily approachable through cerebellopontine angle cistern she underwent a right retromastoid suboccipital craniotomy , c1 arch excision and gross total excision of the meningioma .
postoperative computed tomogram of the head showed complete excision [ figure 1 g ] , and the patients are asymptomatic at follow - up of 9 months .
a 50-year - old male had a headache and swaying while walking since 8 months and had developed diplopia on looking to the right side . on examination
computerized tomography ( ct ) scan showed an iso - hyperdense mass lesion in the fourth ventricle which was heterogeneously enhancing on contrast .
magnetic resonance imaging ( mri ) showed a t1 and t2 isointense heterogeneously enhancing mass lesion with areas of nonenhancing cavities .
the fourth ventricular floor appeared to be free from the lesion [ figure 1a  d ] . with this
( a ) t2-weighted image showing a heterogenous isointense intra fourth ventricular mass , ( b ) the lesion is isointense on t1-weighted imaging , ( c and d ) the lesion is enhancing on contrast administration , and it has multiple lobulations and is entirely inside the fourth ventricle .
( e and f ) contrast enhanced axial magnetic resonance imaging of and sagittal computed tomography , respectively of case 2 and ( g ) a postoperative computed tomography showing complete excision the patient underwent midline suboccipital craniotomy , telovelar approach , and excision .
lesion was located in the fourth ventricle toward the right displacing the vermis to left , entirely intraventricular , attached to the choroid plexus , and posterior inferior cerebellar artery feeders were seen , during surgery supplying the lesion , which was coagulated and removed .
histopathological examination of the lesion led to the diagnosis fibroblastic meningioma with brain invasion , who grade ii [ figure 2 ] .
photomicrograph showing interlacing fascicles of meningothelial cells on hematoxylin - eosin staining ( a ) , expression of epithelial membrane antigen ( b ) , and high mib-1 labeling ( c ) , on immunoperoxidase ( magnification = scale bar )
a 47-year - old female presented with a headache and neck pain of 1-year duration along with gait disturbance and recurrent falls of 4-month duration . on examination , she had features suggestive of papilledema .
mri of the brain showed a predominantly intra fourth ventricular mass with extension into the cerebellomedullary cistern .
it was isointense on t1 , iso to hyperintense on t2 with homogenous contrast enhancement .
there was no clear , identifiable plane between the lesion and fourth ventricular floor in mri [ figure 1e and f ] . in view , that the lesion was located a bit laterally and easily approachable through cerebellopontine angle cistern she underwent a right retromastoid suboccipital craniotomy , c1 arch excision and gross total excision of the meningioma .
postoperative computed tomogram of the head showed complete excision [ figure 1 g ] , and the patients are asymptomatic at follow - up of 9 months .
meningiomas arising in the ventricular system without dural attachment is extremely rare , with an incidence of 0.53% among all intracranial meningiomas and still rare are these located in the fourth ventricle .
fourth ventricle meningioma ( fvm ) was first described and surgically removed by sachs in 1983 . since then 50 fvm
it appears that it is more common in females and occur at the average age of 45 years ( range : 1471 years ) .
they can present with a wide variety of symptoms like intracranial hypertension related to obstructive hydrocephalus , cerebellar dysfunction , focal neurological deficits such as diplopia , facial nerve paralysis , long tract signs , and even fluctuating symptoms due to the intermittent occlusion of the fourth ventricle .
fvm is unlikely to be considered in differential diagnosis of fourth ventricular tumors in adults because it has no characteristic imaging features on ct scan or mri .
metastasis , pilocytic astrocytoma , medulloblastoma , ependymoma , and choroid plexus papilloma are usually considered as differential diagnosis .
features such as heterogeneous enhancement , anatomical detail , ill - defined margin , and tumor extent are clues for diagnosis of meningioma in this location .
malignant tumors show lower apparent diffusion coefficient ( adc ) values ; on the other hand , the adc values of pilocytic astrocytoma , hemangioblastoma , and ependymoma are higher .
meningiomas in posterior fossa without dural attachment have been classified as type i : meningiomas that arise from the choroidal plexus of the fourth ventricle and located entirely inside ventricular cavity , type ii : meningiomas that arise from the inferior tela choroidea and partially located cerebellar hemisphere , and type iii : meningiomas located within the cisterna magna but not implanted in the dura mater . according to this classification ,
although almost all reported cases have been totally resected , the technical nuances may cause a potential problem due to the consistency and location . as these tumors may be firm and fibrous depending on the type of meningioma , resection may cause bleeding , and difficulty maneuvering in the narrow operative corridor , and may need vermian splitting in few cases .
intraoperative neurophysiological monitoring is an important and adjunct helps to prevent operative injury of cranial nerves and the brainstem . in our cases ,
perioperative cerebrospinal fluid diversion would be necessary only in cases with severe hydrocephalus or to tide over severe raised intracranial pressure if any , preoperatively .
the majority of the reports are grade i meningioma 's , four cases are reported to be grade ii , and there are no reports of recurrences . however
, if there is residue in case of higher grade meningiomas , then radiotherapy may have to be considered .
both our reported cases are grade i. like any other meningioma cases , we recommend follow - up based on the histopathological grade and extent of resection , closer follow - up will be required in higher grade meningiomas , especially if the lesion is incompletely excised .
meningiomas which occur primarily in the fourth ventricle are very rare and this only the second report from india .
total removal of the lesion with good microsurgical technique is the standard and has a good outcome with low operative risk .
understanding the clinical features and a careful preoperative radiological examination is required to differentiate this tumor from more commonly occurring lesions at this location . as more and more such cases are being reported the differential diagnosis of meningioma
 meningioma 's occurring intraventricular region are rare and these occurring in the fourth ventricle is even rare . because of the rarity , it is not usually considered as a differential diagnosis in any age group . 
 clinical features and imaging is not characteristic , and most of them are thought to be some different tumor . here , we discuss two cases harboring a primary fourth ventricular meningioma grade ii , which was surgically excised successfully . total excision was achieved in both cases and as the tumor was firm to soft and vermian splitting was not required . 
 understanding the clinical features and a careful preoperative radiological examination is required to differentiate this tumor from more commonly occurring lesions at this location . 
Introduction
Case Reports
Case 1
Case 2
Discussion
Conclusion
Financial support and sponsorship
Conflicts of interest