Clinical course and characteristics of acute presentation of fourth nerve paresis.

PURPOSE: Many cases of acute-onset cranial nerve paresis have benign etiologies such as microvascular occlusion. Most will resolve completely and neuroimaging is usually unnecessary. Few reports exist on acute fourth nerve paresis.

METHODS: A retrospective review was conducted of all patients presenting with diplopia to the emergency department for 1 year caused by isolated fourth cranial nerve paresis from any cause including trauma.

RESULTS: Thirty-two patients met the criteria, 26 (81%) males and 6 (19%) females, with an average age of 59.5 years (range: 14 to 80 years). Eighteen (56%) had a microvascular etiology with diabetes mellitus, hypertension, or both; 6 were already taking medication. Six (19%) had decompensating fourth nerve paresis (2 had hypertension and 1 had recent head trauma). Closed head trauma accounted for 2 patients, migraine and herpes zoster virus accounted for one each, and 4 remained unknown. Nineteen patients (59%) were prescribed prisms and 2 patients were given occlusion. Diplopia resolved without treatment in 23 patients (72%) within 2 weeks to 10 months, but 89% of patients with microvascular etiology resolved spontaneously. Three patients continued with prisms, one patient underwent surgery.

CONCLUSION: The prognosis for complete and spontaneous resolution of microvascular fourth nerve paresis was excellent, with 89% completely resolved within 10 months.