Meningioma is the most common type of intracranial tumours. It accounts for almost one quarter to one third of the total intracranial mass. They are slow growing tumours arising from the meninges which surround the brain and spinal cord. Meningiomas are classified into three groups1 according to the tumour grade and its potential for recurrence.
WHO Type 1: It is a low grade tumour (less aggressive form) with less chances of recurrence. Histologicaly they are benign. This is the most common type of meningioma.
WHO type 2: Also called as atypical meningioma with more aggressive behaviour compare to the type1 and are associated with poor outcome.
WHO type 3: It is also called anaplastic menigioma. They have obvious malignant features like invasion into the brain parenchymal tissue and a high mitotic index.
Meningioma can occur in any site of CNS with a meningeal covering. According to the location it is classified into Spinal and cranial, where the cranial meningioma represents the majority and a mere 12% consists of spinal meningioma.
Rarely meningiomas can arise from outside the dural covering of brain or spinal cord. They are called extradural /extracranial meningiomas or ectopic meningioma. They consist of less than 1% of all meningiomas.Most common locations of the ectopic meningiomas are head and neck.
The radiological findings of these extradural menigiomas are not pathogonomic. However a well circumscribed enhancing mass with presence of calcification in a tumour which is located adjacent to a cranial nerve or skull base/sinuses should allow the radiologist to raise a possibility of this rare and atypical condition.
In our case report we described a case of an extracranial meningioma, which was presented to us with a cheek swelling for evaluation.
A 52 y old female with no significant past medical history, presented with left sided cheek swelling .She noticed this swelling 2 years back which was initially negligible size but gradually progressed to the size of around 3 cm over a period of 2 years. Swelling was also associated with headache (left hemicranium) and photophobia. It was not associated with pain or symptoms of facial nerve involvements or difficulty in jaw movements.
On local examination Swelling was noted on the left side of cheek, diffuse, non tender and was about 3×3 cm. Swelling was not fixed to underlying tissue /bone and no associated local rise of temperature noted. General and other systemic examination was normal.
After the routine blood investigations patient underwent a multislice contrast Computed tomography of brain and neck.
Contrast enhanced CT revealed a large ill defined heterogenously enhancing isodense lesion , measuring 5 x 4.3 x 4 cm (ap x ml x cc).centered in the left infratemporal fossa (retro maxillary space ) and masticator space. The lesion is noted to have both intracranial and extracranial extension.
Extracranially the lesion was noted to extend into the buccal space, left nasal cavity and posterior ethmoid sinuses. The lesion is also noted causing enlargement o f the left foramen rotundum, suggestive of left maxillary nerve involvement.
There was also intracranial extra axial spread of the tumour along the meninges in the left parasellar region. A possibility of meningioma or an atypical schwanomma was given after detailed analysis.
Following this USG guidance FNAC of the tumour was done which showed high cellular loose cohesive clusters of large polygonal cells which are syncitial along with tight whorls of ovoid cells. These cells have a bland nuclear morphology with fine chromatin and abundant eosinophilic cytoplasm.Areas of calcifications are also noted which was suggestive of meningioma.
The patient underwent excision under local General anesthesia. Intra operatively the lesion described above was noted to be close to V2 trigeminal nerve. Lesion separated from trigeminal nerve and removed from pterygopalatine and infratemporal fossa, upto the meckels cave.
Meningiomas can exist as intracranial or extracranial brain tumors.Prevelance of extracranial meningiomas are very less compare to intracranial and they are more common in females. These extra-cranial meningiomas have been classified into primary and secondary extra-cranial meningiomas. Primary extra-cranial meningiomas are not associated with an intra-cranial mass, whereas secondary extra-cranial meningiomas are extensions from some intra-cranial pathology.
Hoye et al has put forward four theories for the formation of extracranial meningioma.
Type A: Involves direct extension from a primary intracranial tumor through the foramina of the base of the skull.
Type B: Involves extracranial growth from arachnoid cells within the sheaths of cranial nerves. Most of the reported primary extracranial meningiomas in the parapharyngeal region of the neck are related to the cranial nerves, particularly VII.
Type C: Involves extracranial growth from embryonic rests of arachnoid without any apparent connection to the foramina of the skull base or cranial nerves.
Type D: Involves distant metastases from intracranial meningioma.There have been cases reported of intracranial meningiomas metastasizing to the liver and lungs.
Our case is most likely a meningioma arising from an ectopic arachnoid cell with no obvious association from cranial nerve which is Type C.
Radiological investigations like CT and MRI will help in diagnosis as well as precise extension of tumour. In CT it appears Iso to hyperdense with uniform contrast enhancement .30% of lesion shows calcifications within. On T1-weighed MRI, meningiomas are isointense to the brain, and less commonly they are hypointense. They become isointense (50%) or hyperintense (40%) on T2- weighed MR images. Meningiomas frequently show intense and homogenous enhancement with gadolinium. However, the final diagnosis of an extracranial meningioma is made by histopathological analysis.
An extracranial meningioma presenting as a cheek swelling can create a diagnostic dilemma as it is a rare condition. It should be considered in all slow growing tumours of cheek, neck and head. CT and MRI are important modality in diagnosing and to look for the extend of lesion which is inevitable for surgical excision. Complete excision is the treatment modality for this extracranial meningioma and histopathological and immunohistiochemistry should be done to confirm the pathology.
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