Oculomotor Nerve Palsy—Etiologies, Symptoms and Diagnosis: A Systematic Review with Meta-Analysis

Background/Objectives: Oculomotor nerve palsy (OMNP) is a clinically significant condition that may represent the earliest manifestation of life-threatening intracranial pathology, particularly aneurysmal compression or neoplasia. Despite its neurosurgical relevance, comprehensive meta-analytic evidence synthesizing OMNP etiologies, clinical presentation, and contemporary diagnostic pathways remains limited. Methods: Following PRISMA 2020 guidelines, MEDLINE, Scopus, and Web of Science were systematically searched for studies reporting quantitative data on OMNP. Pooled prevalence estimates were calculated using random-effects models for causes and symptoms, while a structured narrative synthesis was performed for diagnostic modalities because outcome reporting was heterogeneous and unsuitable for meta-analysis. Risk of bias was assessed using the Joanna Briggs Institute (JBI) risk of bias tool. Results: Twenty-four studies involving 5541 patients were included. Using a multivariate multilevel model to account for within-study dependence, the most common etiological category was vascular disorders (35.62%), followed by idiopathic (16.47%) and neoplastic (12.10%). Head trauma and aneurysms accounted for 11.26% and 10.08% of cases, respectively. Diplopia (60.63%) and ptosis (54.12%) remained the predominant clinical symptoms, while pupil involvement was identified in 40.62% of the pooled population. Diagnostic paradigms have shifted decisively toward non-invasive neuroimaging, with magnetic resonance imaging reported in 66% of included studies and magnetic resonance or computed tomographic angiography increasingly employed to identify surgically relevant vascular lesions. Conclusions: Although vascular disorders represented the most common etiological category, the notable prevalence of aneurysmal and neoplastic causes underscores the importance of prompt high-resolution neuroimaging and early neurosurgical assessment. Early recognition and etiological stratification remain essential to optimize management and prevent irreversible neurological morbidity.