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
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.
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
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
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