[Lumbar Spinal Disease or Peripheral Nerve Disorder? The Role of Neurological Examination in Differential Diagnosis].

Lower-limb numbness, pain, and weakness are common clinical complaints that require differentiation between cauda equina or radicular lesions associated with lumbar spinal disease and peripheral nerve disorders. Because degenerative findings on lumbar imaging are common, particularly among older adults, the responsible lesion should not be determined based on imaging findings alone. In this context, neurological examination contributes to anatomical localization and is central to the differential diagnosis. Particular emphasis is placed on interpreting muscle weakness and sensory disturbance according to myotomal, dermatomal, and peripheral nerve distributions. Other neurological findings, including gait disturbance, neurogenic claudication, bladder or bowel dysfunction, nerve stretch signs, and reflex changes, also provide important clues for localization. This review further addresses common diagnostic challenges encountered in daily practice, including differentiation of L5 radiculopathy from fibular neuropathy in patients with foot drop, distinction between cauda equina lesions and polyneuropathy, recognition of immune-mediated polyradiculoneuropathies, and identification of amyotrophic lateral sclerosis when it mimics lumbar spinal disease. Ancillary tests such as nerve conduction studies, needle electromyography, somatosensory evoked potentials, nerve ultrasound, and imaging should be interpreted in relation to the lesion localization suggested by neurological examination.