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Neurology India, Vol. 59, No. 4, July-August, 2011, pp. 635-637 Letter to Editor Anterior interhemispheric fissure meningioma without dural attachment in an adult Aniruddh Kulkarni, A Arivazhagan, S Sampath, BA Chandramouli Department of Neurosurgery, National Institute of Mental Health and Neurosciences, Bangalore, India PMID: 21891955 DOI: 10.4103/0028-3886.8435 Extra-ventricular meningiomas without dural attachment are very rare. We report a case of a large meningioma in the anterior interhemispheric fissure without dural attachment. A 40-year-old lady presented with apathy, paucity of speech output and social incontinence of four months' duration. On examination, the patient was conscious, disoriented with inappropriate laughter. She had abulia and frontal lobe release reflexes. Ocular fundi revealed papilledema. Magnetic resonance imaging (MRI) of brain revealed a large extra-axial well-defined lesion measuring 7.0×7.5×6.5 cm in the anterior interhemispheric region, extending to both sides and compressing the adjacent brain. It was isointense on T1 and hyperintense on T2 sequences and brilliantly enhancing on contrast, probably attached to the falx at the junction of the anterior one-third and middle one-third [Figure - 1]a-c. A cerebral angiogram revealed that the tumor had displaced the pericallosal artery inferiorly while the callosomarginal artery was coursing through and above the tumor. There was no significant tumor blush from both the internal carotid arteries and both external carotid arteries [Figure - 1]d-g. The patient underwent bifrontal craniotomy, interhemispheric approach and total excision of the tumor. Intraoperatively, a relatively well-defined moderately vascular tumor was noted in the interhemispheric fissure. However, there was no attachment to the falx. The tumor was firmly adherent only to the arachnoid layer covering the left pericallosal artery. The tumor was excised with great attention to preserve the artery, which required leaving a small sleeve of tissue on the pericallosal artery. Histopathology revealed transitional meningioma [Figure - 1]h and i. She had transient worsening of dysphasia, which improved with anti-edema measures postoperatively. Meningiomas are thought to arise from the arachnoid cap or meningothelial cells in the arachnoid membrane which are in close apposition to the overlying dura, accounting for the usual finding of these tumors being attached to the duramater. [1] These arachnoid cap cells are not only found near the arachnoid villi, but also cover the arachnoid membrane in all locations. [2] This raises the interesting possibility for meningiomas to develop in locations without dural attachment. Excluding the ventricles, meningiomas without dural attachment are far less frequent and have been reported within the sylvian fissure or the posterior fossa. [2],[3],[4] Meningiomas in the intraparenchymal, sulcal or fissure locations are considered to arise from the arachnoid cap cells in the Virchow Robin spaces along the blood vessels or from the piamater. [5] Zhang et al., reviewed all patients with meningiomas without dural attachment and classified them. It was noted that among the cerebral fissures, meningiomas have been reported to occur in the sylvian fissure, pineal region and in the cerebellomedullary cistern. [4],[6] In the present case, the cerebral angiogram revealed that the tumor was forked between the pericallosal and callosomarginal arteries which is unusual, in retrospect. In falcine meningiomas, both the branches at the bifurcation are often displaced inferiorly by the tumor. We also noted that there was no tumor blush from the external carotid arteries (ECAs). It has been reported earlier that these meningiomas without dural attachment are not supplied by ECA branches, but by the branches of the internal cerebral artery or vertebral artery. [3],[6],[7] We noted that the tumor was densely adherent only to and probably arising from the arachnoid over the left pericallosal artery. Some authors have reported that a similar pattern was noted in sylvian fissure meningiomas, which arise from the arachnoid over the middle cerebral arteries. [2],[8] This observation merits mention to stress the necessity to identify and preserve the major arteries, whose covering arachnoid can be the origin of meningiomas, especially when no dural attachment is noted intraoperatively. References
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