Peripheral Nerve Injuries/Palsies

Peripheral Nerve Injuries → result from systemic diseases (eg. diabetes or autoimmune disease) or localised damage (eg. trauma, compression, tumours) and manifest with neuroligical deficits distal to the level of the lesion
Causes:
- Injury → from an accident can compress, crush or cut nerves
- Medical Conditions → diabetes, guillain-barre syndrome, carpal tunnel syndrome
- Autoimmune Disease → SLE, RA, sjogren’s syndrome
Types of Nerve Damage:
- Neuropraxia → compression injury causing temporary disruption of nerve conduction
- Axonotmesis → axon is damaged but the perineurium and epineurium remain intact
- Neurotmesis → complete nerve transection
- Traumatic Neuroma → benign, painful nodular thickening caused by nerve regeneration at the site of different forms of nerve injury

Clinical Features:

Motor Nerves → muscle weakness, painful cramps, uncontrollable muscle twitching
Sensory Nerves → paraesthesia in hands and feet (numbness + tingling), trouble sensing pain or changes in temperature, walking.
Autonomic Nerves → excessive sweating, changes in blood pressure, inability to tolerate heat, GI symptoms.
Nerve Palsies
GBS ⇒ immune-mediated demyelination of the peripheral nervous system often triggered by an infection (campylobactur jejuni). Back/leg pain as initial symptom. Progressive, symmetrical weakness of all the limbs, weakness is classically ascending (limbs are first), reflexes are absent. LP will show rise in protein with normal WCC. Decreased motor nerve conduction velocity due to demyelination.
Carpal Tunnel Syndrome ⇒ compression of median nerve in the carpal tunnel. Causes include pregnancy, rheumatoid arthritis, oedema. Pins and needles in thumb, index and middle finger. Weakness of thumb adduction, wasting of thenar eminence, tinel’s sign (tapping causes paraesthesia), phalen’s sign (flexion of wrist causes symptoms). Tx with steroid injections and wrist spints at night. Surgical decompression if severe.
Foot Drop ⇒ may be due to common peroneal nerve lesion (most common) or L5 radiculopathy. Common peroneal nerve lesion occurs due to compression at neck of fibula. Weakness of foot dorsiflexion and eversion. Weakness of hip abduction suggests L5 radiculopathy.

Investigations: