Supratentorial Intracerebral Schwannoma : Its Fate and Proper Management
A 25-year-old man presented with recent aggravation of focal seizure activities on the right arm was referred to our clinic. His first seizure attack took place 9 years ago which started with involuntary right arm tremors followed by a loss of consciousness and generalized tonic-clonic convulsions. When he first visited the neurology clinic at that time, a neurologic examination revealed no abnormalities. He had no relevant medical history, no stigmata of neurofibromatosis and no family history of this disorder. His magnetic resonance images (MRI) of the brain revealed a small mass measuring 1.5×1.0×1.1 cm at the left precentral gyrus. The mass was predominantly hypointense to gray matter on the T1 weighted images, heterogeneously hyperintense on the T2 weighted images and showed intense enhancement on gadolinium injection (). Peritumoral edema was observed, affecting mainly the left precentral gyrus. No cystic change was found. Initial radiologic differential diagnoses were a pleomorphic xanthoastrocytoma, ganglioglioma, and dysembryoplastic neuroepithelial tumor. Since he was free of symptoms between seizure attacks and well tolerated his condition after taking anti-epileptic medication, he refused to undergo surgical treatment. During the 9 years of follow-up, he had no trouble in carrying on with his daily life. He complained of only intermittent focal seizures presented as right arm tremors and transient weakness, and these seizure attacks mostly occurred under stress conditions like sleep deprivation and heavy alcohol consumption combined with poor drug compliance. A brain MRI which was taken two years after the initial image work-up, revealed no interval change. Because the patient's symptom was stable, no further imaging study was pursued.\nNine years later, he complained of sudden prolonged seizure duration with right arm weakness, which became progressively worse over the past month prior to his visit. A neurological examination revealed a grade IV weakness of the right elbow and hand. Immediate brain computed tomography and MRI were taken. The size of the enhancing portion had increased to 2.3×1.9×1.6 cm, and a large peritumoral cyst measuring about 5.5 cm in diameter had newly appeared (). No intratumoral calcification and cystic wall enhancement were observed.\nSince the mass was located at the precentral gyrus, awake craniotomy was performed to minimize postoperative motor and sensory deficit. A rectangular fronto-parietal craniotomy was done to expose the enhancing mass with the help of a neuronavigation system. Sonography was used to identify the mass located just beneath the cortical surface which appeared to have a bluish discoloration (). By direct cortical stimulation with a nerve stimulator, we confirmed that the motor cortex of the right wrist and hand were located just on the posteromedial side of the mass. Dissection started from the anterior part of the mass. It was well circumscribed from adjacent brain tissue and could be removed in an en bloc fashion. During removal, slight yellowish but cerebrospinal fluid like clear fluid gushed out from the cyst. The patient did not present any worsening of neurologic deficit during the surgery.\nThe patient's postoperative course was uneventful and his right forearm and hand weakness improved. One month after the operation, he had a postoperative MRI which revealed no residual enhancing mass, but the cyst remained although its size was somewhat decreased (). At one year and six months of follow-up, he has remained seizure free since the operation and his right hand and arm weakness has recovered to near normal status, with no difficulty in his daily living.\nThe specimen consisted of several fragments of soft tissues, measuring 2.0×1.0 cm in the largest dimension. Grossly, the cut surfaces showed a gray yellow myxoid appearance. Under light microscopy, the tumor was composed of alternating Antoni A and B areas, i.e., cellular and less cellular areas (). There was neither hemorrhage or necrosis or cystic change. The tumor had fascicular arranged spindle cells with elongated nuclei without nuclear pleomorphism. There was few mitoses (1/10 HPF) and the MIB-1 (Ki67) labeling index was low (1.03%). The tumor cells were robustly positive for S100 protein. Electron microscopic examination was consistent with Schwannoma, which showed elongated cells surrounded by a continuous external lamina and scattered Luse bodies (long space collagen).