Giant posterior fossa arachnoid cyst causing tonsillar herniation and cervical syringomyelia
This was a case report of a 28-year-old female patient presented with a history of paraesthesia involving right upper limb of 8 months duration. She had a spontaneous abortion 3 weeks ago. Following that, she developed sudden onset of weakness of both lower limbs (left side greater than the right side). There was a history of headache on and off increased by coughing. Her bowel and bladder functions were normal and also general and systemic examination was normal. Cranial nerves were normal. Fundus examination was normal. She had a weakness of all four limbs (lower limbs more than upper limbs). Deep tendon reflexes were exaggerated in lower limbs and sluggish in upper limbs. Planters were extensors. There was also dissociated sensory loss on her right arm and shoulder. Patient was investigated with magnetic resonance imaging (MRI) brain and cervical spine and it showed giant retrocerebellar arachnoid cyst extending into the left cerebellopontine angle causing descent of the cerebellar tonsils across the foramen magnum with a syringomyelic cavity extending from C1 down and associated ventriculomegaly []. The patient underwent midline suboccipital craniectomy, foramen magnum decompression and C1 arch excision with duroplasty. Part of the cyst wall was excised. Histopathological examination of the cyst wall showed a cuboidal layer of arachnoid cells suggestive of arachnoid cyst []. Follow-up images showed a reduction in the size of the cyst and reduction in the mass effect over cerebellum and brain stem structures []. At 10 months follow-up, patient made an uneventful recovery and doing well.