Title: The etiologies of isolated fourth cranial nerve palsy: a 10-year review of 158 cases
Abstract: To identify the etiologies of isolated fourth cranial nerve palsy in Ramathibodi hospital, Thailand. Patients diagnosed with isolated fourth nerve palsy from January 1, 2009, through July 31, 2020 in Ramathibodi Hospital, were included in this retrospective, observational case series. The demographic data of patients, age at presentation, the etiologies of isolated fourth nerve palsy and neuroimaging results (if indicated) were recorded. We identified 154 unilateral and 4 bilateral cases of isolated fourth nerve palsy. Mean age at presentation was 38.89 ± 25.71 years old. Most of the unilateral cases were congenital (57.79%), with microvasculopathy (27.92%), intracranial neoplasm (8.44%) and other etiologies. Trauma with closed head injury was the most common etiology of bilateral cases (75%), followed by ruptured arteriovenous malformation (25%). Twenty-one of the 43 (48.84%) patients with microvasculopathy fourth nerve palsy underwent neuroimaging, with normal findings, and all patients' symptoms resolved within 6 months of symptom onset. In our series, most of the isolated fourth nerve palsy cases were congenital, followed in frequency by microvasculopathy and intracranial tumor, as in many studies. In cases of microvasculopathy, the clinical signs and symptoms resolved within 6 months in all cases: observation was sufficient, with no necessity for neuroimaging. However, neuroimaging should be considered in cases with atypical presentations, such as headache, periorbital pain, or if there is rapid progression or no recovery.