Carpal Tunnel

Question 1

Clinically Relevant Anatomy

Answer 1

The carpal tunnel (CT) is formed by non extendable osteofibrous wall surrounding its content. The wall of the tunnel tunnel consists of carpal bones, joint capsule, carpal ligamets, flexor carpi radialis tendon and the flexor retinaculum. Carpal bones form an arch like base for the tunnel. Flexor retinaculum spanning from the pisiform bone and the hamulus of the hamate bone to the scaphoid and the trapezium complete and close the tunnel.

CT allows passage of multiple structures between hand and proximal segments of body. Tendons of flexor digitorum profundus, flexor digitorum superficialis and flexor pollicis longus muscles and the median nerve form the content of carpal tunnel. The median nerve passes from the forearm to the palmar aspect of the hand, Its sensory axons convey sensory stimulation for median nerve distribution consisting of palmar aspect of thumb and fingers, except for the fifth digit and ulnar half of fourth digit. Motor axons of median nerve supply the muscles of thenar eminence

Question 2

Clinical presentation

Answer 2

CTS onset is generally gradual with tingling or numbness in median nerve distribution of affected hand.

Patients may notice aggravation of symptoms with static gripping of objects as phone or steering wheel but also at night or early in the morning. Many patients will report improvement of symptoms following shaking or flicking of their hand.

As the disorder progresses, the feeling of tingling or numbness may become constant and patients may complain of burning pain.
The final symptoms are weakness and atrophy of muscles thenar eminence.
These combined effects of sensory deprivation and weakness may result in complaint of clumsiness and loss of grip and pinch strength or dropping things,

Question 3

Differential diagnosis

Answer 3

Process of differential diagnosis should give consideration to all conditions which could potentially cause a dysfunction of median nerve, or its contributories in brachial plexus, C 5 to 8 nerve roots and central nervous system.

For example: an injury of nn. digitales in the palm, pronator teres syndrome or cervicobrachial syndrome, particularly when C7 nerveroot is involved. Even though the neurological symptoms of this pathology have a distinct dermatomal character, the C7-C8 dysfunction with radiculopathy will overlap with CTS in location of paraesthesia of hand
Other conditions to be aware of when diagnosing CTS include:

neuralgic amyotrophy 
ntracranial neoplasms
multiple sclerosis [
Cervical syringomyelia
brachial plexus injury
pancoast tumor

Question 4

Tests

Answer 4

1. Phalen’s test
   The patient flexes his wrist for one minute and reports any symptoms that may occur. The test is described in many different positions. As described by G. A. Phalen (1966) the patient holds his forearm vertically and lets his wrist drop down in 90° flexion [61]. The arm can also be held horizontally in front of the patient with the wrist hanging down. Another common way of executing the test is to hold both wrists against each other in 90° flexion with elbows also flexed and fingers pointing in the patient’s direction.
   The Reverse Phalen’s test, where the patient holds his wrist and fingers in full extension, provokes the same symptoms as the original test, which are the symptoms that are usually experienced by patients with CTS, such as tingling, paresthesia or pain in the fingers.
2. Tinel’s sign
   The examiner taps with his fingers of with a tendon hammer on the inside of the wrist onto the medial nerve at carpal tunnel level. Patients with CTS will not feel pain, but experience a tingling sensation in their hand.
3. Hand elevation test (Roos Stress Test)
   Isn’t this a test for thoracic outlet syndrome? The Roos Stress Test is indeed an indicative test for TOS and not for CTS. The hand elevation test is however a CTs test. The link to Roos Stress Test should be removed.The patient hold his arm above his head as straight as possible and holds this position for a minimum of two minutes. The test is positive when the patient experiences typical CTS symptoms, such as a numb or tingling feeling in the fingers or pain or stiffness in the fingers, palm or wrist. Some patients also experience soreness in the shoulder.

This test is only considered meaningful if the results can be duplicated by other, more specific CTS tests.

4. Scratch Collapse Test
   Cheng et al. introduced this test in 2008 as an improved method to diagnose CTS among other syndromes. The test is executed with the patient facing the examiner with his arms adducted, elbows flexed and hands outstretched with the wrists in neutral position. The patient has to resist the external rotation movement the examiner is trying to make by pushing both the patient’s forearms out. The examiner then scratches the median nerve at carpal tunnel level and the previous exercise is repeated. A brief loss of resistance against the external rotation force of the affected side after scratching the median nerve is considered a positive scratch collapse test.
5. Durkan’s Carpal Compression Test
   The examiner externally applies pressure directly over the carpal tunnel. This test is also positive when the typical CTS symptoms occur while the pressure is applied.

Question 5

Etiology and epidemiology

Answer 5

Idiopatic carpal tunnel syndrome

Idiopathic CTS occurs more frequently in females (65–80%) and between the ages of 40 and 60 years; 50–60% of the cases are bilateral.

Idiopathic CTS is correlated with hypertrophy of the synovial membrane of the flexor tendons caused by degeneration of the connective tissue, with vascular sclerosis, edema and collagen fragmentation

genetic and anthropometric factors (size of the carpal tunnel) were of most importance followed by other correctable predisposing factors of clinical importance as:
besity
smoking
excessive alcohol consumption

Secondary carpal tunnel syndrome

Abnormalities of the walls of CT

Any condition that modifies the walls of the carpal tunnel may cause compression of the median nerve.
Abnormalities of the shape or position of the carpal bones: dislocation or subluxation of the carpus
Abnormalities of the shape of the distal extremity of the radius: fractures (translation of more than 35%) or skewed consolidation of the distal radius; osteosynthesis material on the anterior face of the radius;
Joint abnormalities: wrist arthrosis, inflammatory arthritis (due to synovial hypertrophy, bone deformation an/or carpal shortening), infectious arthritis, rhizarthrosis or villonodular synovitis
Acromegaly.
Abnormalities of the content of CT

Tenosynovial hypertrophy;
Inflammatory tenosynovitis: inflammatory rheumatism[16] lupus and infection
Metabolic tenosynovitis: diabetes mellitus (abnormality of collagen turnover), primary or secondary amyloidosis (chronic hemodialysis with deposition of beta-2-microglobulin),gout and chondrocalcinosis;

Dynamic carpal tunnel syndrome

The pressure inside the carpal tunnel increases during wrist extension and flexion Repetitive extension and flexion movements of the wrist, along with flexion of the fingers and supination of the forearm, have been implicated in this increase Incursions of muscle bodies from the superficial and deep flexors of the fingers, when the wrist and fingers are extended, have been found in 50% of the cases This particular movement can be seen in occupational pathological condition