Cranial Nerve Palsies in the Setting of Arachnoid Cysts: A Case Series and Literature Review

Abstract

Background: Arachnoid cysts (ACs) are benign lesions typically believed to not cause neurologic defects in the adult population and are most often found incidentally on imaging. We describe 2 patients with ACs potentially leading to isolated cranial nerve (CN) dysfunction. Methods: We describe 2 patients, 1 with a fourth nerve palsy and the other with a sixth nerve palsy found to have ACs on MRI brain imaging in locations that potentially caused a compressive CN palsy. We review previous literature of ACs presenting with CN III, IV, or VI palsy. Results: Patient 1 was a 62-year-old man who presented with a 22-year history of diplopia with strabismus examination consistent with a congenital CN IV palsy. Despite multiple surgeries, his CN IV palsy insidiously worsened. An AC in the posterior fossa with mass effect on the quadrigeminal plate and asymmetric atrophy of the right superior oblique was identified on imaging. Patient 2 was an 80-year-old man who presented with an 18-year history of diplopia and was found to have a left esotropia and abduction deficit consistent with complete CN VI palsy. An AC in the left cavernous sinus was identified on imaging. He underwent strabismus surgery with satisfactory resolution of diplopia. We identified a total of 18 previously published cases: 8 reports of CN III palsy, 4 reports of CN IV palsy, and 6 reports of CN VI palsy. Patient ages ranged from 1 to 67 with a median of 34.5. In 16/18 (89%) cases, the diagnosis of ACs was made within 1 year of symptom onset. Surgical removal of the AC was successful in resolving diplopia in 7/12 (58%) cases. In no case was strabismus surgery performed as primary treatment. Conclusions: Although ACs are typically congenital asymptomatic lesions, we present a case series of 2 patients with ACs in anatomic locations that potentially caused chronic, progressive, isolated CN palsies leading to strabismus. Our literature review revealed that most published cases detailing this clinical scenario resulted in neurosurgical fenestration of ACs with mixed results. Our cases represent 2 patients with AC-associated CN palsy treated with strabismus surgery.