June 20, 2024

Carpal tunnel syndrome (CTS) is the most common compressive neuropathy in the upper extremity.

It is first reported by Paget (1854) as Median nerve neuropathy

Coined by Moersch as Carpel Tunnel Syndrome (CTS)

Median nerve compression at the carpal tunnel

Anatomy of Carpal tunnel

Formed by the transverse carpal ligaments (TCL) spanning the concave carpal arch

Contains the 9 flexor tendons and the median nerve

Carpel bone arching dorsally, hook of hamate and pisiform medially, scaphoid tubercle and trapezoid ridge laterally, roof by flexor retinaculum

Anatomy of carpal tunnel
Anatomy of carpal tunnel

The width of the carpal tunnel (Narrowest area)

20 mm (at the level of hook of hamate)

Proximal end:25mm

Distal end: 26 mm

Depth of the carpal tunnel

Narrowest point: 10 mm

Deepest point: 13mm

So it typically forms a Hour glass shape

Etiology

I. Idiopathic (Most common in adults)

II. Factors increasing the volume of carpal tunnel

(Mucopolysaccharidosis is most common in children)

III. Extrinsic factors that alter the contour of tunnel

IV. Exertional and Overuse conditions

V. Neuropathic factors (diabetics, alcoholism, nutritional deficiency, vitamin toxicity)

Pathophysiology of the carpal tunnel syndrome

Normal interstitial pressure: 2.5 mmHg

Can reach up to 30mmHg during maximum extension and flexion.

Increase in pressure above 30mmHg results in CTS (Nerve conduction decreases)

 CTS: This pressure increased to 99 mm Hg with 90 degrees of wrist flexion and to 110 mm Hg with the wrist at 90 degrees of extension.

Pathophysiology of the carpal tunnel syndrome
Pathophysiology of CTS

Clinical features

Primarily a clinical diagnosis

Tingling and numbness in the typical median nerve distribution

Pain, described as deep, aching, or throbbing, occurs diffusely in the hand and may radiate up the forearm

Thenar muscle atrophy

Paresthesia –the most frequent symptom- often awakens the patient with burning and numbness of hand and relieved by exercises

According to American academy of neurology guidelines of CTS
According to American Academy of Neurology guidelines

Maneuvers for diagnosing CTS

Provocative tests

Phallen test  (sensitivity 0.75, specificity 0.47)

Reverse phallen test

Tinel Sign  (sensitivity 0.60, specificity 0.67)

Durkan test  (sensitivity 0.87, specificity 0.90) is the most sensitive provocative test

Gilliat test(tourniquet test)

Sensory evaluation

Semmes-Weinstein monofilament test (sensitivity 0.83) is sensitive for diagnosing early CTS

Static two-point discrimination (5 mm)

Moving two-point discrimination (4 mm)

Large fibers (light touch and vibration) are affected early than small fibres (pain and temperature)

Tuning fork test (sensitivity 0.87)

Monofilament: inability to discern below 2.83 monofilament

2pd > 5mm

Tuning fork (256 cps): altered sensation

Katz Hand diagram

(Sensitivity 0.96 and Specificity 0.73)

A. In the classic pattern

B. The probable pattern

C. In the unlikely pattern

Katz Hand diagram

Boston Carpal Tunnel Questionaire

(A) In the classic pattern, symptoms affect at least two of digits 1, 2, or 3. It permits symptoms in the fourth and fifth digits, wrist pain, and radiation of pain proximal to the wrist, but it does not allow symptoms on the palm or dorsum of the hand. (B) The probable pattern has the same symptom pattern as the classic pattern, except palmar symptoms are allowed unless confined solely to the ulnar aspect. In the possible pattern (not shown), symptoms involve only one of digits 1, 2, or 3. (C) In the unlikely pattern, no symptoms are present in digits 1, 2, or 3.

Validity ??

Szabo et al. concluded that :

an abnormal hand diagram,

a positive Durkan test

abnormal Semmes-Weinstein sensitivity testing

night pain

Has a probability of 0.86 of having carpal tunnel syndrome.

In Normal cases: 0.0068

Electro diagnostics studies

(90% sensitive and 60% specific)

The criteria for diagnosing CTS are two or more of the followings:

• Prolonged conduction velocity of the median nerve across the wrist

• Increase duration of action potential

  • Polyphasic contour
3 electrode: Active (Black) kept in the muscle belly of APB muscle(mid point between distal wrist crease and MCP joint), Reference electrode (R,red) placed over APB tendon and ground electrode(Green) is placed on the palm or dorsum of the hand. Median nerve is stimulated between FCR and PL 8 cm proximal to A electrode. Sensory ACTIVE: proximal Phallynx of all digits, R: 4 cm distal to A, and ground: 14 cm proximal to A 

The Standard values in the diagnosis of CTS are as follows:

•Distal median motor >4.5 msec and conduction velocity > 0.5 m/s vs. opposite hand

•Distal sensory latency >3.5msec and conduction velocity > 1 m/s vs. opposite hand

•Compound muscle action potential (CMAP) <5 mV Amplitude of sensory nerve action potential (SNAP) <10mV is abnormal

Cherian A, Kuruvilla A. Electrodiagnostic approach to carpal tunnel syndrome. Ann Indian AcadNeurol 2006;9:177-82

Latency across wrist ( With the distance between stimulating and recording electrodes of 6.5 cm)

False-negative result of 16-34%

X-RAYS

Bony cause of CTS (malunited Distal radius fracture, perilunate dislocation)

A Carpal tunnel view is taken

The X-ray beam is placed along the volar aspect of the carpal tunnel to the point 2.5 cm distal to the base of 4th metacarpal at an angle of 25 -30 to the long axis

USG

Screening tool

•Increase in cross-sectional area(CSA) of the median nerve in carpal tunnel

• Cut-off value: 10.7 mm2  at the inlet  (sensitive 97%)

•Ratio of CSA at the level of pisiform and distal radius (swelling ratio) = >1.3

Mean inlet CSA 8.7mm2 (7.2-9.8)

Normal Swelling ratio = 1

Palmer bowing of the flexor retinaculum in grasp position measured at the level of hook of hamate is used

Treatment Options

Etiological factors should be diagnosed and treated first.

If the local cause for compression is ruled out

Conservative treatment (splinting and corticosteroid injection)

If symptoms are continuous or objective signs like sensory loss or motor loss are present then go for surgical decompression

Non-operative

1. To put the wrist in a neutral position, long use is avoided to prevent stiffness (Splintage)

2. Water-soluble steroids are injected into the carpal tunnel.

Single corticosteroid injection yields transient relief in approximately 80% of patients after 6 weeks, but only 20% are symptoms-free by 1 year

The median nerve should not be directly injected to avoid nerve injury

3. Nsaids, pregabalin, vitamin B6, Diuretics

4. Hatha yoga

Operative

Open Carpal Tunnel Release and Mini-Open

Endoscopic Carpal Tunnel Release

The long axis of the ring finger:1-1.5 cm long, distal to the distal wrist crease, and ulnar to palmaris longus tendon axis

Meta-analysis suggests that the patients treated with ECTR return to work 1 wk earlier with fewer complications like post-operative pain scar tenderness, immobilization