Primary Intra-Axial Benign Brain Schwannoma: A Systematic Review with Pooled Individual Patient-Level Analysis

Background: Intra-axial brain schwannomas are exceptionally rare, accounting for less than 1% of all intracranial schwannomas. Their rarity and non-specific radiological features make diagnosis and management challenging. This study provides a systematic review of the existing literature to summarize the clinical, radiological, histopathological, surgical, and outcome characteristics of reported cases. Methods: A systematic review was conducted following PRISMA guidelines. A comprehensive search of PubMed and Scopus was performed using predefined keywords. Studies reporting intra-axial brain schwannomas were included. Data were extracted on patient demographics, clinical presentation, radiological features, tumor location, surgical management, histopathological findings, and outcomes. In total, 80 studies comprising 131 patients were included. Results: The pooled analysis showed that intra-axial schwannomas most commonly occur in young adults, with a median age of 23 years. The most frequent presenting symptoms were seizures, headache, and focal neurological deficits. Radiologically, lesions typically demonstrated heterogeneous contrast enhancement with frequent cystic degeneration. The frontal and temporal lobes were the most commonly affected sites. Surgical resection, most often via craniotomy with gross total resection, was the predominant management strategy. Overall, most reported cases demonstrated favorable postoperative outcomes. Conclusions: Intra-axial brain schwannomas are rare entities that should be considered in the differential diagnosis of intra-axial brain tumors. Surgical resection remains the mainstay of treatment and is generally associated with excellent outcomes.