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Gold standard case presentation
Median nerve palsy
A median nerve palsy is a lower motor nerve (LMN) lesion or the peripheral nervous system. It is served by C6-C8 and T1. It follows the same path as axillary artery. Distal to the elbow, the median nerve serves the following muscles:
- pronator teres
- flexor carpi radialis
- palmaris longus
- flexor digitorum superficialis
Distally, the muscles that are served:
- flexor digitorum profundus
- flexor pollicis longus
- pronator quadratus
The most common cause is carpal tunnel syndrome (affects up to 3.8%), which is also the most common peripheral neuropathy of the upper limbs, and the compression of the median nerve is by the transverse carpal ligament.
Other causes of median nerve palsy
- Pronator syndrome (entrapment/compression at the pronator teres)
- Anterior interosseous nerve syndrome (aka Kiloh-Nevin syndrome – entrapment/compression of the proximal aspect of the forearm – the anterior interosseous nerve)
- C6-C7 Cervical radiculopathy
- Thoracic outlet syndrome
- Multiple sclerosis
Conditions associated with carpal tunnel syndrome
- Idiopathic (most common cause)
- Trauma (most likely in this case)
- Hypothyroid myxoedema
- Rheumatoid arthritis and other connective tissue disease
- Tuberculous tenosynovitis
- Positive family history
Common anatomical sites
- Nocturnal pain or pins-and-needles with radiation up the forearm
- Daytime hand clumsiness associated with wrist flexion
- Relief with shaking of the wrists
- Positive Tinel’s sign (tapping over the wrist at the median nerve)
- Positive Phalen’s test (flexing the wrist, which to ensure it is positive, need to hold for 1-minute unless symptoms appear earlier)
- Abductor pollicis brevis weakness
Nerve conduction study
This study requires small electrical pulses used to activate nerves over the forearm, in this condition, of the median nerve and then measuring the responses of the nerve. A lot of patients can be frightened about the concept of electrical shocks, but these are very safe and well tolerated.
A key contraindication for the study is the presence of a cardiac pacemaker – which is not absolute, but requires discussion with the cardiologist about where the electric shocks will be delivered and whether they will be near the chest wall or not.
For more information about nerve conduction studies can be found here.
Other investigations that can be done include ultrasound of the median nerve and MRI when exploring rarer causes.
- For mild to moderate symptoms
- Oral corticosteroids
- Corticosteroid injection
- Carpal tunnel release (release for the transverse carpal ligament)
- Good long term outcome in up to 90% of cases
For more information, here is a Review of Recent Literature.
- Review / Skip
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