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Video Script Intro Pat M: Carpal Tunnel Syndrome, henceforth abbreviated as CTS, is a mononeuropathic entrapment syndrome caused by pressure on the median nerve within the carpal tunnel. Anatomy The carpal tunnel is located within the wrist. It is formed by the deep arch of the carpal bones and the flexor retinaculum, a broad connective tissue sheet that spans the space between the medial and lateral sides of the arch. The carpal bones that the flexor retinaculum attaches to are the pisiform and hook of hamate medially, and the tubercles of scaphoid and trapezium laterally. The structures that pass through the carpal tunnel include; the four tendons of flexor digitorum superficialis, the four tendons of flexor digitorum profundus, the tendon of flexor pollicis longus, and the median nerve. The carpal tunnel functions to keep these structures in position as they pass into the hand, preventing the tendons from bowing. Flexor digitorum superficialis originates at the medial epicondyle of the humerus and bifurcates to attach on either side of the middle phalanx of digits 2-5. Flexor digitorum profundus lies deep to flexor digitorum superficialis, extending from the ulna to the base of the distal phalanx of digits 2-5. Together, these muscles act to flex digits 2-5. Flexor pollicis longus is also a deep muscle, extending from the radius to the base of the distal phalanx of the thumb. As its name suggests, this muscle functions to flex the thumb. The tendons of flexors digitorum superficialis and profundus are surrounded by a single synovial sheath, whilst the tendon of flexor pollicis longus is surrounded by its own synovial sheath. These tendinous sheaths prevent damage caused to the tendons by friction and rubbing. This is significant because these tendinous sheaths may become inflamed and contribute to CTS. The median nerve lies anteriorly to the aforementioned tendons. It passes through the carpal tunnel and divides into digital branches in the hand. It supplies the skin over the lateral 3 ½ fingers, including the nail beds. The median nerve also innervates the first two lumbricals and the three muscles of the thenar eminence; opponens pollicis, abductor pollicis brevis and flexor pollicis brevis. The first two lumbricals flex the metacarpophalangeal joint of digits 2 and 3. Opponens pollicis causes opposition of the thumb, abductor pollicis brevis abducts the thumb and flexor pollicis brevis flexes the thumb. MCQ1 What structures pass through the carpal tunnel? a. Tendons of flexor digitorum profundus b. Tendons of flexor digitorum superficialis c. Tendon of flexor pollicis longus d. Median nerve e. All of the above Answer: E Cause Jamie: Carpal Tunnel Syndrome occurs as the result of a combination of repetitive activities and predisposing health conditions. Often it is difficult to isolate a single cause, hence the condition can be termed idiopathic. Ultimately however, the causes of CTS result in an increase in pressure on the median nerve as it travels through the carpal tunnel. Most commonly, this increase in pressure is due to inflammation of the ligaments and tendon sheaths that pass through the carpal tunnel. Some of the main causes are: repetitive wrist actions, bone fracture and regrowth, underlying illnesses and predisposing conditions. Repetitive or extreme wrist motions, vibrations, and using fingers with high force all increase the likelihood of developing CTS. Situations where this would occur include: Forceful hand movements involved in hammering all day Repetitive finger movements like those used in typing Hand to arm vibration when using a power tool Long periods of work while remaining stationary or in awkward positions Bone breakage and regrowth can also cause CTS. If someone breaks their wrist or dislocates the carpal bones, the carpal tunnel space may decrease as new bone growth, healing bones and bone spurs will begin to reform over the fracture. This leads to compression of the median nerve and tendons which can lead to tenosynovitis. Underlying illnesses that contribute to swelling in soft tissues and joints in the upper limb or reduce blood flow to the hands can also cause CTS. These include: rheumatoid arthritis, gout, diabetes, lupus, hypothyroidism, all of which increases pressure by reducing the available area in the carpal tunnel itself. Other condtions that may cause CTS are: congenital predisposition, over activity of the pituarity gland, fluid retention, known as edema, during pregnancy or menopause, a cyst or tumor in the carpal tunnel, and obesity. MCQ2: What causes carpal tunnel syndrome? a. Rheumatoid arthritis, edema, fracture of the fingers and narcolepsy b. A lesion in the wrist, obesity, laceration of the wrist and congenital predisposition c. Hypothyroidism, rheumatoid arthritis, broken wrist and pectoral tear d. A tumor in the carpal tunnel, edema, over-activity of the pituitary gland and diabetes e. Lupus, power tool usage, throwing a ball and cyst in the lower back Answer: D Effects Andrew: The median nerve supplies all the flexors of the forearm except flexor carpi ulnaris and the medial half of flexor digitorum profundus. It also supplies the palmar surface of the lateral 3.5 digits including the nail beds and finger tips. Damage that occurs to the median nerve in the carpal tunnel does not affect the flexor muscles, so they will still function as normal. However, it will lead to a loss of function of all the thenar muscles in the hand resulting in a condition known as “ape hand”. The sufferer of ape hand is unable to abduct their thumb away from the rest of their hand. This inability to abduct the thumb results in a loss of precision grip. Similarly, a patient with CTS will feel paraesthesia, commonly known as “pins and needles” along the lateral 3.5 fingers. The more the nerve is irritated the stronger the tingling sensation along these fingers will be. Although the median nerve impingement is localised to the carpal tunnel, the patient may feel pain anywhere along the entire upper limb. This pain can disrupt daily life and sleep, affecting their quality of life. In severe cases individuals will be unable to perform basic tasks such as brushing their hair without pain. Because the patient cannot abduct their thumb due to impaired nerve supply, atrophy of the thenar muscles occurs. This can be observed by a decrease in the thenar eminence over time. MCQ3: What is not an effect of median nerve damage in the carpel tunnel: a. Ape hand b. Numbness of the lateral 3.5 digits c. Thenar eminence atrophy d. Hand of Benediction e. Waking during the night from pain Answer: D Diagnosis + Treatment Pat C: Diagnosis of CTS is based on a series of clinical tests and is ultimately confirmed by electrodiagnostics. Initial tests (such as X-rays, laboratory tests) and consulting the patient’s medical history are used to assess any possible underlying medical disorders that may be contributing to or mimicking the condition. Physical examinations may include asking the patient to: - Produce certain movements: flexion, abduction and opposition of the thumb - Make a grip and testing the strength of the grip - React to sensory stimulation of the skin and two-point discrimination test on the fingertips Specific diagnostic tests such as Tinel’s test and Phalen’s manoeuvre work to induce CTS symptoms, which are indicators of CTS: - Tinel’s sign test: The Tinel’s sign test involves tapping or pressing on the median nerve at the wrist. The test is positive if it elicits a tingling or shock-like sensation. - Phalen’s manoeuvre: For the Phalen’s manoeuvre, the patient is asked to flex both wrists and orient their hands so that the dorsal surfaces are pressed against each other. They are then asked to maintain this position for 60 seconds. If within the timeframe, the patient experiences discomfort identical to that of carpal tunnel syndrome (increasing tingling, numbness), the test result is positive. This test measures the severity of carpal tunnel syndrome: the quicker the onset of symptoms, the severe the case. Electrodiagnostic tests are performed to confirm carpal tunnel syndrome provided the provocative tests are positive. Nerve conduction studies measure the speed at which an impulse is transmitted from one nerve to the next. The presence of a time delay or changes in intensity is an indicator of CTS. Electromyography measures electrical activity and can determine the extent of damage to the median nerve. Early detection and treatment of CTS is crucial to avoid further damage to the median nerve. Resting – patients should avoid activities at home or work that may trigger the symptoms. Night splints are custom-made device that immobilises the wrist in a neutral position. Medications such as non-steroidal anti-inflammatory drugs (NSAIDs) or corticosteroid injections relieve pain symptoms, but may not be effective for longterm resolution. Surgery is usually considered as a last resort, except for patients with severe CTS. The procedure involves making an incision through the skin at the base of the palm. A smaller incision is made in the flexor retinaculum to release the pressure from the tunnel. The cut is left unclosed, so that through healing, the formation of scar tissue across the flexor retinaculum expands the volume of the carpal tunnel, allowing it to accommodate the inflamed tendons and reduce nerve compression. Although the symptoms are relieved after surgery, a full recovery of the wrist may take several months during which patients may experience loss of strength at the wrist. MCQ4: Which ONE of the following clinical examinations involves tapping the median nerve to elicit paraesthesia at the fingers? a. Phalen’s manaoeuvre b. Nerve conduction study c. Electromyography d. Tinel’s test e. Westphal’s sign Answer: D