Anatomy of Carpal Tunnel:
Posterior side: 8 carpal bones
Anterior side: Transverse carpal ligament
9 Flexor tendons
Median Nerve Distribution in Hand:
Origin: From lateral and medial cords of brachial plexus
Lumbricals: 1st and 2nd
Muscles of thenar eminence: Opponens pollicis, Abductor Pollicis Brevis and Flexor Pollicis Brevis)
Mnemonic: LOAF (Lumbricals, Opponens pollicis, Abductor Pollicis Brevis and Flexor Pollicis Brevis)
Skin of the palmar side of the thumb, the index and middle finger, half the ring finger, and the nail bed of these fingers (3 and 1/2 digits)
Lateral part of the palm by palmar cutaneous nerve (unaffected in Carpal tunnel syndrome)
Carpal Tunnel Syndrome
It is a syndrome characterized by the compression of the median nerve as it passes beneath the flexor retinaculum in carpal tunnel.
Any space occupying lesion (SOL) of carpal tunnel can cause carpal tunnel syndrome –
- Rheumatoid arthritis
- Wrist osteoarthritis
- Colle’s fracture
Mnemonic: MEDIAN TRAP
- Edema premenstrually
- Rheumatoid arthritis
It usually occurs in females between the age of 40 and 70. They complain of tingling, numbness or discomfort in the lateral 3 and 1/2 fingers i.e. distribution of median nerve. They also complain of intermittent attacks of pain in the distribution of the median nerve on one or both sides. The attacks frequently occur at night. The reason symptoms are worse at night may be related to the flexed-wrist sleeping position and/or fluid accumulating around the wrist and hand while lying flat. Pain may be referred proximally to the forearm and arm.
Motor changes: Ape-like thumb deformity, loss of opposition of thumb, index and middle fingers lag behind when making the fist
Sensory changes: Loss of sensations on lateral 3 and 1/2 digits including the nail beds and distal phalanges on dorsum of hand
Vasomotor changes: The skin areas with sensory loss is warmer due to arteriolar dilation; it is also drier due to absence of sweating due to loss of sympathetic supply
Tropic changes: Long-standing cases of paralysis lead to dry and scaly skin. The nails crack easily with atrophy of the pulp of fingers.
To approximate where along the wrist the median nerve runs, gently flex and radially (laterally) deviate your wrist. Two tendons will become palpable and even visible—palmaris longus (in midline) and flexor carpi radialis
(lateral to it). However, 15% of people do not have a palmaris longus muscle. The median nerve runs deep between these tendons.
This position should be held for about 1 minute.
Positive test : numbness or tingling along the median nerve distribution
With the palm up, tap over the carpal tunnel area of the wrist 5 or 6 times
Positive test : tingling or paresthesia in the median nerve distribution
Press thumb over carpal tunnel and hold pressure for 30 seconds.
Positive test: Onset of pain or paresthesia in the median nerve distribution
Nerve conuction studies are done for diagnosis these days
- Immobilizing braces/Splints
- Analgesics like NSAIDs
- Local injection of steroids
- Surgery: Dividing the flexor retinaculum
Carpal Tunnel Syndrome as Occupational Disease
- repetitive hand motions
- awkward hand positions
- strong gripping
- mechanical stress on the palm
- Farmers (milking cow)
- Office workers (keyboarding)
- Painter, etc.