Case 31 History ---- The patient is a 59 year old woman with a clinical/radiological diagnosis of left cerebellopontine angle AVM, who underwent Gamma knife radiosurgery in January 2000 and subsequently was treated with endoscopic third ventriculostomy on 5/23/2012 and a ventriculoperitoneal shunt on 10/5/2012. On 10/23/2012 she began developing vertigo, nausea, vomiting and ataxia. A left cerebellopontine angle 2.5 x 2.0 x 2.0 cm arteriovenous malformation was predominantly fed by the left anterior inferior cerebellar artery with free draining veins which were distributed to the left and right transverse sinuses and the superior vermian vein. This was a complex lesion in the left cerebellar hemisphere containing areas of old and subacute blood products as well as areas of solid internal enhancement, surrounded by areas of more patchy enhancement and extensive edema. Radiological imaging shows avid enhancement within the left CPA lesion (interpreted as consistent with radiation necrosis) with interval increase in the surrounding edema and increased mass effect on the fourth ventricle and brain stem. The patient was seen in the clinic following evaluation in conjunction with her recent head CT which showed a progressive increase in the density of the left cerebellar mass which suggested neovascularity in the setting of radiation necrosis. Given the clinical history of gamma knife treatment for a cerebellar arterial venous malformation in this region as well as the findings from today's angiogram, this lesion is favored to represent post radiation changes in the AVM nidus with superimposed late radiation necrosis of the surrounding brain tissue. Operative procedure: Left retrosigmoid craniotomy with biopsy and resection of underlying lesion.
