Unilateral adduction deficit in idiopathic intracranial Hypertension from tortuous optic nerve sheath

Idiopathic intracranial hypertension (IIH) is a syndrome of elevated intracranial pressure (ICP) without any identifiable brain pathology and with normal cerebrospinal fluid (CSF) composition. Diagnostic criteria allow only for involvement of the 2nd and 6th; cranial nerves. Other focal neurological deficits exclude the diagnosis. Common orbital imaging findings include prominent subarachnoid space within the optic nerve (ON) sheaths with flattening of the posterior sclera at the ON insertions, and tortuosity of; ONs. We present a case of IIH causing pseudo-INO due to mass effect of the expanded optic nerve sheath on the extraocular muscles.