Makindo Medical Notes.com

The median nerve is involved in carpal tunnel syndrome. There are typically no actual neurological findings in the exam of a patient with this syndrome.

About

• Commonest mononeuropathy
• Compression of the median nerve within the Carpal tunnel

Aetiology

• The median nerve is compressed with 9 tendons into the confines of the Carpal tunnel.
• Signs may be evident with thenar wasting and difficulty with thumb opposition and abduction
• Entrapment of the median nerve at the wrist causes weakness to the intrinsic muscles of the hand

Causes

• Rheumatoid arthritis, Pregnancy, Acromegaly
• Colles fracture, Idiopathic, Minor trauma
• Amyloid related to dialysis - B2 microglobulin deposition
• Myxoedema, Obesity

Clinical

• Sensory loss and pain and paraesthesia on the palm of the hand on the radial 3 and a half fingers but may actually be the whole hand. This is related to the greater cortical representation of the thumb and first 2 fingers.
• Weakness - look for weakness in abductor pollicis brevis and opposition and eventually wasting of the thenar muscles.
• Positive Tinel's test - percussion over the median nerve at the level of the flexor retinaculum causes electric shock sensation in the fingers.
• Try Phalen's test - forceful wrist flexion for 1 minute which recreates symptoms.
• Symptoms of pain extending as far up as the shoulder occur mainly at night

Investigations

• FBC and U&E are usually normal
• ESR, PPE, BJP - Myeloma
• B12 - should be checked in all peripheral neuropathies
• TFT - exclude Myxoedema
• Nerve conduction tests and needle EMG to estimate severity especially if surgery is considered. Will show conduction delay at the wrist

Differential

• Cervical C6-7 radiculopathy who may also have neck pain

Management

• Treat underlying cause
• Simple analgesia may help. Light splints for a few weeks - especially may be worn in bed at night hold the wrist in a neutral position
• Localised Steroid Injection into the Carpal tunnel with long-acting steroid though there may be a slight worsening post-injection
• Surgical Decompression by dividing the flexor retinaculum is for patients with intractable symptoms and/or evidence of weakness