Carpal Tunnel Syndrome Flashcards
What causes carpal tunnel syndrome?
- it is caused by compression of the median nerve as it travels through the carpal tunnel
- this causes pain / numbness in the median nerve distribution on the hand
What is the carpal tunnel and what travels through it?
- the flexor retinaculum is a fibrous band that wraps across the front of the wrist
- a passageway is formed between the carpal bones and the flexor retinaculum
- the median nerve and flexor tendons pass through the carpal tunnel
flexor retinaculum is also called transverse carpal ligament
How can the contents of the carpal tunnel become compressed?
- swelling of the tendon sheaths due to repetitive strain injury
- narrowing of the carpal tunnel
Which branch of the median nerve travels through the carpal tunnel and what does it supply?
palmar digital cutaneous branch
- this supplies sensory innervation to the palmar aspects and full fingertips of:
- thumb
- index finger
- middle finger
- lateral half of the ring finger
Which branch of the median nerve does NOT pass through the carpal tunnel?
palmar cutaneous branch
- this is NOT affected by carpal tunnel syndrome
- it originates before the carpal tunnel
What muscles are affected in carpal tunnel syndrome?
thenar muscles
- these are all supplied by the median nerve
- abductor pollicis brevis
- flexor pollicis brevis
- opponens pollicis
What usually causes carpal tunnel syndrome?
it is usually idiopathic and no clear cause can be found
What are the risk factors for carpal tunnel syndrome?
- repetitive strain
- obesity
- perimenopause
- rheumatoid arthritis
- diabetes
- acromegaly
- hypothyroidism
What conditions are associated with bilateral carpal tunnel syndrome?
- acromegaly
- diabetes
- hypothyroidism
- rheumatoid arthritis
What is acromegaly?
- a condition in which the body produces too much growth hormone during adulthood
- results in abnormally large hands and feet
- there may also be enlargement of the forehead, jaw and nose
usually diagnosed between ages of 30-50
What is the typical onset of symptoms in carpal tunnel syndrome like?
- there is a gradual onset of symptoms
- the symptoms are initially intermittent
- they are often worse at night
What are the sensory symptoms associated with carpal tunnel syndrome?
- numbness
- paraesthesia (pins & needles / tingling)
- pain
- burning sensation
these symptoms are in the distribution of the palmar digital cutaneous branch of the median nerve
When do sensory symptoms of carpal tunnel syndrome tend to be worse?
- symptoms tend to be worse at night
- they may wake the patient from sleep
- patient may shake their hand to try and relieve the symptoms
What are the motor symptoms associated with carpal tunnel syndrome?
- weakness of thumb movements
- weakness of grip strength
- difficulty with fine movements involving the thumb
- wasting of the thenar muscles (atrophy)
all of the motor symptoms affect the thenar muscles
What are the 2 special tests for carpal tunnel syndrome?
- Tinel’s test
- Phalen’s test
What is Phalen’s test?
- the wrist is fully flexed and held in this position for 30 seconds
- the patient is asked to perform the “reverse prayer” sign
- the test is positive when this position triggers the sensory symptoms of carpal tunnel
- there will be numbness and paraesthesia in the distribution of the median nerve
What is Tinel’s test?
- the wrist is tapped at the location where the median nerve passes through the carpal tunnel
- the test is positive when this triggers the sensory symptoms of carpal tunnel syndrome
remember tapping a tin can
What scoring system is used to predict the likelihood of carpal tunnel syndrome?
Kamath & Stothard carpal tunnel questionnaire (CTQ)
- a high score can replace the need for nerve conduction studies to confirm the diagnosis
How are nerve conduction studies performed?
- a small electrical current is applied by an electrode to the median nerve on one side of the carpal tunnel
- recording electrodes at the median nerve on the other side of the tunnel record the electrical current reaching them
- this demonstrates how well signals are passing through the carpal tunnel
