Carpal Tunnel Syndrome

Definition                 collection of symptoms and signs due to compression or traction of the MN at the level of the CT

Symptomatic compression neuropathy of the Median Nerve at the wrist underneath the transverse carpal ligament

Incidence                 3%            (14% in DM)

Age         

Sex           female:male=6:1

Aetiology                 Unknown

Predisposing factors             

I                 Idiopathic

C                Colles, Cushings

R                RA

A               Amyloid, Acromegaly

M              Myxoedema, Mass, (Diabetes) Mellitus

P                Pregnancy

S                Sarcoid

Anatomy

Carpal tunnel:         Hook of Hamate and Pisiform to Scaphoid tubercle and ridge of trapezium

Floor = carpus, roof= transverse carpal ligament [flexor retinaculum]

Contents 4 x FDS tendon [34/25] 4 x FDP tendon [2345], FPL, Median nerve

Kaplan’s line =distal border abd thumb to hook of hamate (intersection of line with vertical line from ulnar border RF).  Deep palmar arch lies deep to Kaplan’s line.  Superficial arch = 2cm distal (proximal palmar crease)

Distal boundary = Kaplan’s line

Proximal boundary=distal wrist crease

 

Motor branch Median nerve                50% extraligamentous

                                                                  30% Subligamentous

                                                                  20% transligamentous

Superficial branch

1. Normal: arises 5cm proximal to CT, runs on ulnar side of FCR tendon sheath.  Divides over flexor retinaculum to medial and lateral branches

2. Branching occurs proximal to CT

3. Nerve pierces flexor retinaculum to enter CT

4. Sensory supply to palm replaced by ulnar n or radial n

Pathophysiology:

Vascular compromise.  Mechanical compression →venous congestion,endoneurial oedema, relative anoxia

Endoneurial oedema→ ↑fibroblasts→fibrosis→barrier to nutrient exchange→segmental demyelination

Clinical features

Muscle wasting

Paraesthesia in median nerve distribution

Worse at night

40% bilateral

Decreased senstion (2-point discrimination)

Tests

Tinels,                                                                              Sens=74%                                 Spec=90%

Phalens,                                                                          Sens=61%                                  Spec=83%

Durkan’s (direct pressure over median nerve)        Sens=86%                                  Spec=83%

Investigations

Nerve conduction studies

Abnormal:               prolonged distal motor latency >4ms [demyelination]

Sensory conduction prolonged >3.5ms

Decreased amplitude [axonal loss]

Prognosis

Differential Diagnosis (Radial wrist pain)

Cervical disk disease C5/6

Peripheral neuropathy

Pronator syndrome

SC lesions-syrinx, MS, tumour

Classification (Neurophysiological classification)

Grade 0Normal

Grade 1Very mild. CTS demonstrable only with most sensitive tests

Grade 2Mild. slow sensory nerve conduction velocity, normal terminal motor latency;

Grade 3Moderate. sensory potential preserved with motor slowing

Grade 4Severe sensory potentials absent but motor response preserved,

Grade 5Very severe

Grade 6Extremely severe. sensory and motor potentials effectively unrecordable

Management

Non-operative splint, NSAIDS, steroid injection-for mild, intermittent symptoms, no muscle wasting eg pregnancy

Operative

Open CTD                95% good results.  Recurrence or persistence in ≤20%:

Inadequate release

Wrong diagnosis

Double crush

Endoscopic CTD     intended to reduce pillar pain (not proven).  Probably earlier functional recovery, but no difference at 1y

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Management: Conservative

                          Injection.  For consent form click here:

                          Decompression

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