Research progress on the diagnosis and treatment of far-out syndrome

Abstract Far-out syndrome (FOS) is a rare cause of L5 radiculopathy, resulting from extraforaminal compression of the L5 spinal nerve within the lumbosacral tunnel. The diagnosis requires the simultaneous fulfillment of two necessary conditions: compression located within this specific anatomical space and the presence of corresponding clinical symptoms. This review aimed to evaluate the diagnostic approaches and treatment strategies for FOS. We conducted a structured literature search in PubMed and Ovid MEDLINE for articles published from database inception to December 6, 2025, using search terms designed to cover the pathogenesis, diagnostic methods, and treatment options of FOS. Because FOS symptoms overlap with those of common lumbar degenerative diseases, it is easily overlooked in clinical practice. Lumbar computed tomography (CT), Lumbar magnetic resonance imaging (MRI), electrophysiological studies, and selective nerve root blocks can all serve as adjunctive examinations in the diagnosis of FOS; combining multiple modalities for comprehensive evaluation may improve diagnostic accuracy. The core of surgical treatment for FOS is decompression of the L5 nerve root. Open surgery has confirmed efficacy, while microscopic and endoscopic techniques can also achieve favorable outcomes with less tissue trauma; the choice of a specific procedure should still be individualized based on each patient's condition. This narrative review summarizes the current understanding of FOS, aiming to enhance its clinical recognition and provide guidance for future research.