Progressive sixth nerve palsy secondary to intracavernous arachnoid cyst and complicated by contralateral optic nerve sheath meningioma.

INTRODUCTION

Optic nerve sheath meningiomas and intracavernous arachnoid cysts are both fairly rare conditions, and to the best of our knowledge, have not been previously reported to co-occur in the same patient. Both can cause diplopia, but only ONSMs have been documented to demonstrate progressive worsening of ocular motility.

CASE REPORT

A 67-year-old woman with blur and diplopia demonstrated a right optic neuropathy and limited ductions bilaterally. Neuroimaging revealed a right optic nerve sheath meningioma and left intracavernous arachnoid cyst. She was conservatively managed with neurosurgical surveillance for 1.5 years, until her diplopia worsened. Ocular motility re-evaluation demonstrated a worsening left abduction deficit, suggesting interval change of the intracavernous cyst, rather than the meningioma.

CONCLUSION

There are only a few reported cases of cranial nerve VI palsy secondary to a cavernous sinus arachnoid cyst. However, this is the first reported case in a patient with a concurrent optic nerve sheath meningioma, and the first case demonstrating progressive worsening of a sixth cranial nerve palsy from an intracavernous arachnoid cyst. Determining which comorbidity caused worsening of symptoms played a critical role in the management of this patient.