Isolated sixth nerve palsy as an initial presentation of primary angiitis of the central nervous system

Primary angiitis of the central nervous system (PACNS) is a newly-emerging disease, and it is known that early diagnosis with treatment is important for the improvement of prognosis.

Here, we report the case of a previously healthy 13-year-old girl who presented with right eye abduction failure, attributed to isolated right sixth nerve palsy, as the initial symptom of PACNS. Magnetic resonance angiography (MRA) showed stenosis in the distal portion of the right internal carotid artery, and delay alternating with nutation for tailored excitation (DANTE)-prepared contrast-enhanced magnetic resonance imaging confirmed vasculitis at the same site. The patient was subsequently treated with three courses of pulse corticosteroid therapy (methylprednisolone intravenously 30 mg/kg/day for three consecutive days). Diplopia completely resolved within 3 months after three course of steroid pulse therapy, and when taking 10 mg PSL daily. Follow-up MRA confirmed complete resolution of the arterial narrowing, and no relapse was observed after 2 months of steroid cessation.

This case report illustrates an unusual presentation of PACNS with isolated sixth nerve palsy. PACNS was thought to cause insults on a single cranial nerve either through local spread of inflammation or hypoxic-ischemic insults on the nerve root due to involvement of feeding microvessels. The decision to perform imaging studies in cases of isolated sixth nerve palsy remains controversial because of the possibility of spontaneous recovery. Our case supports the existing literature that recommends that even an isolated symptom of unilateral abducens nerve palsy requires timely imaging studies.