Acquired Ocular Motor Nerve Palsy in Neurology Clinics: A Prospective Multicenter Study

BACKGROUND AND PURPOSE: This study aimed to determine the patterns and etiologies of acquired ocular motor nerve palsy (OMNP) diagnosed in neurology clinics. We also investigated the clinical features that may predict the causes other than microvascular ischemia in isolated OMNP. METHODS: We performed a prospective multicenter study that had recruited 298 patients with acquired OMNP from the neurology clinics of referral-based 9 university hospitals in Korea. We finally selected 235 patients with isolated OMNP and divided them into older (age ≥50 years, n=188) and younger (age <50 years, n=47) groups. We investigated the underlying etiologies of acquired OMNP. We also estimated the frequency of microvascular ischemia and other causes in isolated OMNP, and sought to determine the clinical features that can predict the causes other than microvascular ischemia. RESULTS: Abducens nerve palsy was the most common (40%) of the acquired OMNPs, followed by oculomotor nerve palsy (27%), trochlear nerve palsy (23%), and multiple OMNPs (10%). The etiologies included microvascular ischemia (47%), inflammatory (21%), stroke (5%), trauma (5%), neoplasm (3%), and others (2%), with the cause not being determined in 13% of the patients. Microvascular ischemia was the most common cause (83%) in patients aged ≥50 years with isolated OMNP, followed by inflammation (6%), stroke (6%), neoplasm (3%), and aneurysm (1%). Microvascular ischemia was more common in the older than the younger group (83% vs. 49%, p<0.001). The intensity of headache was the only risk factor for causes other than microvascular ischemia in isolated OMNP. CONCLUSIONS: Vascular and inflammatory disorders are the most common causes of acquired OMNP diagnosed in neurology clinics. Microvascular ischemia was the predominant cause of isolated OMNP. Severe headache indicates causes other than microvascular ischemia in isolated OMNP.