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
What are the questions based around on the Kamath & Stothard CTQ?
- do the symptoms wake you at night?
- do you have trick movements (e.g. shaking the hand) to improve the symptoms?
- is the little finger affected?
if the little finger is affected, this makes carpal tunnel syndrome less likely
What is the main investigation for diagnosing CTS?
nerve conduction studies
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
What are the 4 management options for CTS?
- rest and altered activities
- wrist splint can be worn at night for a minimum of 4 weeks
- steroid injections
- surgery
