Extra axial adult cerebellopontine angle medulloblastoma: An extremely rare site of tumor with metastasis

A 22-year-old male patient presented with headache, vomiting, ataxia, and left facial weakness of one-month duration. Vision was normal. Fundus examination showed papilloedema. He had left lower motor neuron facial paresis, left IX and X cranial nerve paresis, and left cerebellar signs. Computed tomography scan of the brain showed a left CP angle mixed-density nonenhancing lesion (5.4 × 2.8 cm) with broad-based tentorial attachment and displacement of the fourth ventricle causing obstructive hydrocephalus [Figure 1]. Findings were confirmed by magnetic resonance imaging (MRI) [Figure 2]. He had previously undergone right ventriculo peritoneal shunt for obstructive hydrocephalus elsewhere. He underwent left retromastoid craniectomy and gross total excision of the lesion. There was clear plane between the tumor and cerebellum, whereas it was adherent to tent laterally. Histopathology showed a highly cellular tumor composed of rosettes of small round cells, with high nucleus-cytoplasm ratio and increased mitotic figures—suggestive of classical medulloblastoma—WHO grade IV [Figure 3]. Postoperatively, he improved. He was advised craniospinal radiotherapy which he failed to receive and presented 15 months later with progressive quadriparesis and sensory impairment of five-month duration with bladder and bowel involvement. On examination, he had 3/5 motor power in the upper limbs and 2/5 in lower limbs and sensory impairment below D4 dermatome. All deep tendon reflexes were brisk with bilateral extensor plantar reflexes. All superficial reflexes were absent. MRI of the brain and spine showed recurrent left CP angle medulloblastoma and intramedullary lesion at cervical level and intradural extramedullary lesion at sacral level, suggestive of drop metastasis in the spine from CP angle medulloblastoma [Figure 4].