Mononeuropathy

Mononeuropathy is a form of peripheral nerve disease in which a single peripheral nerve or its proximal branches is impaired, producing focal sensory loss and/or weakness in its distribution. It is distinct from polyneuropathy, which typically affects many nerves in a length-dependent, symmetric pattern.

Common causes include trauma, compression or entrapment (such as carpal tunnel affecting the median nerve, ulnar neuropathy at the elbow, or peroneal neuropathy at the fibular neck), ischemia or vasculitis, infections such as herpes zoster, and inflammatory or autoimmune conditions. Diabetes can contribute to focal nerve injuries, though it more often causes polyneuropathy.

Clinical features depend on the nerve involved: sensory loss in the nerve’s distribution, focal numbness or tingling, and weakness of the muscles innervated by that nerve. Examination reveals localized deficits and reduced reflexes; chronic compression may cause progressive weakness and pain.

Evaluation includes detailed history and neurologic examination, nerve conduction studies and electromyography to localize the lesion and assess severity. Imaging such as ultrasound or MRI can identify entrapment or structural causes. Laboratory tests may be indicated to search for metabolic, inflammatory, infectious, or autoimmune etiologies.

Management targets the underlying cause and symptom relief. Compressive mononeuropathies may respond to splinting, anti-inflammatory medications, corticosteroids, or surgical decompression. Inflammatory or infectious etiologies may require immunotherapy or antimicrobial treatment. Physical therapy helps maintain strength and prevent contractures. Prognosis varies with the cause and duration of nerve injury, ranging from complete recovery to persistent deficits. Mononeuritis multiplex, involvement of multiple noncontiguous nerves, is a related pattern often due to systemic processes.