Wrist/Hand: Carpal tunnel syndrome

Question 1

Define Carpal tunnel syndrome

Answer 1

Collection of symptoms and signs caused by compression of the median nerve in the carpal tunnel

Question 2

Aetiology of Carpal tunnel syndrome

Answer 2

Development of raised pressure within the carpal tunnel and/or the median nerve segment that lies within the tunnel

Primary: idiopathic (40%)
Secondary: tenosynovitis, RA, amyloidosis, myeloma, acromegaly, osteoarthritis, fracture, tumour, pregnancy, nephrotic syndrome
Obesity, menopause, diabetes, end-stage renal disease

May lead to ischaemia and scarring of the nerve (likely to be the cause of the intermittent sensory symptoms) + demyelination

Question 3

Risk factors for Carpal tunnel syndrome

Answer 3

Female
>30 
high BMI
Pregnancy 
Occupations involving repeated wrist movement
Fractures of wrist
Rheumatoid arthritis
Diabetes
Dialysis

Question 4

Symptoms of Carpal tunnel syndrome

Answer 4

Numbness of the hand (dominant usually first and worst, intermittent, gradual onset)
Waking at night with paraesthesia/pain in hand/wrist
Weakness of hand
Clumsiness
Aching and pain in arm
Finger stiffness
Cold sensitivity

Question 5

Signs of Carpal tunnel syndrome on examination

Answer 5

Numbness in the medial nerve distribution (sparing of thenar eminence)
Weakness of thenar muscles and atrophy
Normal reflexes

Tinel’s sign: tapping nerve -> symptoms
Phalen’s sign: maximal flexion of wrist for 1 min -> symptoms
Signs of underlying cause

Question 6

Investigations for Carpal tunnel syndrome

Answer 6

Electromyogram (EMG):
Focal slowing of conduction velocity in the median sensory nerves across the carpal tunnel
Prolongation of the median distal motor latency
Possible decreased amplitude of median sensory and/or motor nerves

USS wrist: May identify SOL
MRI wrist: may identify SOL