Clinical course and characteristics of acute presentation of fourth nerve paresis

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.

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.

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.

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