CARPAL TUNNEL SYNDROME

ANATOMY AND IMAGING

Dr SUMIT KUMARRADIOLOGY JR 2PONDICHERRY

DEFINITION

Carpal tunnel syndrome, the most common focal peripheral neuropathy, results from compression of the median nerve at the wrist.It is a cause of significant disability, and is one of three common median nerve entrapment syndromes; the other two being anterior interosseous nerve syndrome andpronator teres syndrome.

ANATOMY OF CARPAL TUNNEL

Boundaries of carpal tunnel:

Volarly : transverse carpal ligament

Dorsally : Carpal bones, deep volar carpal ligaments and volar interoseeous

ligaments

Laterally : scaphoid tuberosity & Trapezium

Medially : Pisiform & hook of hamate

Contents: 9 Tendons and median nerve

Tendons: The tendon of Flexor pollicis longus

4 tendons of Flexor digitorum profundus

4 tendons of Flexor digitorum superficialis

Transverse carpal Ligament : Flexor Retinaculum

Thick fibrous band from the tuberosity of scaphoid & a portion of trapezium to the

Pisiform & hook of hamate.

EPIDEMIOLOGY

Affects adult individuals

Three times more common in women than in men

High prevalence rates have been reported in persons who perform certain repetitive wrist motions (frequent computer users)

CAUSES

Aberrant

Anatomy

- Anomalous flexor tendons

- Congenitally small carpal

canal

- Ganglion cysts

- Lipoma

- Proximal lumbrical

muscle insertion

- Thrombosed artery

Infections

- Septic arthritis

- Mycobacterial infections

- Lyme disease

Inflammatory

conditions

- Flexor tenosynovitis

- Connective tissue diseases

- Gout or pseudogout

- Rheumatoid arthritis

Meatabolic conditions

- Acromegaly

- Hypothyroidism

- Amyloidosis

- Diabetes

Increased canal

volume

- Pregnancy

- Obesity

- Edema

- Congestive heart failure

CLINICAL FEATURES

Pain

Numbness

Tingling

Symptoms are usually worse at night and can awaken patients from sleep.

To relieve the symptoms, patients often “flick” their wrist as if shaking down a thermometer (flick sign).

Pain and paresthesias may radiate to the forearm, elbow, and shoulder.

Decreased grip strength may result in loss of dexterity, and thenar muscle atrophy may develop if the syndrome is severe.

CLINICAL FEATURES

DIAGNOSIS

History

Physical examination

Investigation

PHYSICAL EXAMINATION

Phalen’s maneuver

Tinel’s sign

Durkan Compression Test

CLINICAL FINDINGS

Sensory

disturbance

Weakness in thumb

abduction

Thenar atrophy

PHALEN’S MANEUVER

In this test the wrist is flexed upto 90 degrees for a period of one minute.

Patient is then asked for the complaints of tingling, numbness an or pain

in the first 3 fingers.

This test can be quantified by noting the time taken for the symptoms to

appear.

There are several ways of positioning the wrist for eliciting the test.

TINEL’S SIGN

Elicitation: Tap over the median nerve as it passes through the carpal

tunnel in the wrist.

Positive response: a sensation of tingling in the distribution of the

median nerve over the hand.

DURKAN COMPRESSION TEST

Gentle pressure directly over carpal tunnel paraesthesia in 30 seconds

or less

Better for wrists with limited motion

Highest sensitivity/specificity of all physical exam tests

SUMMARY OF TESTS

Test Sensitivity Specificity

Phalen’s 75% 62%

Tinel’s 64% 90%

Compression 87% 90%

Radiographic featuresUltrasound and MRI are the two imaging modalities which best lend themselves to investigating entrapment syndromes.

UltrasoundIn imaging median nerve syndromes, ultrasound is useful in examining CTS, potentially revealing, in fully developed cases, a triad of:

•Palmer bowing of the flexor retinaculum (>2 mm beyond a line connecting the pisiform and the scaphoid)•Distal flattening of the nerve•Enlargement of the nerve proximal to the flexor retinaculum.

Enlargement of the nerve seems to be the most sensitive and specific criterion, but what cut-off value for pathological size remains debated; normal cross-sectional area is given at 9-11 mm ², but the range of sizes deemed pathological is wide.

MRIIn CTS, MRI can demonstrate

•Palmer bowing of the flexor retinaculum.•Enlargement of the median nerve at the level of the pisiform, and flattening of the median nerve at the level of the hook of the hamate.•Other signs are edema or loss of fat within the carpal tunnel, and increased size/edema of the nerve on water-sensitive sequences.•Although sensitivity and specificity of mri in cts are low (23-96% and 39-87%, respectively),• MRI is especially well-suited for detecting masses, arthritic changes, or normal variants.

Segmental swelling of median nerve (arrows). Axial MR images (TR 2000, TE 20) at levels of pisiform (A) and hook of hamate (B). Left wrist viewed toward elbow with palm down. Note enlargement of nerve proximally (A) compared with normal caliber of nerve distally (B).

Axial T1 et T2FS : T1: enlarged median nerve T2: nerve signal increase. The normal fascicular appearance of the nerve has

disappeared

DIFFERENTIAL DIAGNOSTICS

Anterior interossous nerve syndrome

(Kiloh- Nevin syndrome)

Pronater teres syndrome

Kienbock's disease

Compression of the Median nerve at the elbow

TREATMENT

CONSERVATIVE TREATMENTS

• GENERAL MEASURES

• WRIST SPLINTS

• ORAL MEDICATIONS

• LOCAL INJECTION

• ULTRASOUND THERAPY

• Predicting the Outcome of Conservative Treatment

SURGERY

GENERAL MEASURES

Avoid repetitive wrist and hand motions that may exacerbate symptoms or make symptom relief difficult to achieve.

Not to use vibratory tools

Ergonomic measures to relieve symptoms depending on the motion that needs to be minimized

LOCAL INJECTION

A mixture of 10 to 20 mg of lidocaine (Xylocaine) without epinephrine and 20 to 40 mg of methylprednisolone acetate (Depo-Medrol) or similar corticosteroid preparation is injected with a 25-gauge needle at the distal wrist crease (or 1 cm proximal to it).

LOCAL INJECTION

Splinting is generally recommended after local corticosteroid injection.

If the first injection is successful, a repeat injection can be considered after a few months

Surgery should be considered if a patient needs more than two injections

ULTRASOUND THERAPY

•May be beneficial in the long term management

•More studies are needed to confirm it’s usefulness

SURGERY

Indications:

1. No response to conservative treatment2. Severe nerve entrapment demonstrated by Nerve conduction studies

3. Thenar atrophy,

4. Motor weakness.

It is important to note that surgery may be effective even if a patient has normal nerve conduction studies

CONCLUSION

Most common focal peripheral neuropathy

Pain and paresthesias in the distribution of the median nerve are the classic symptoms.

While Tinel’s sign and a positive Phalen’s maneuver are classic clinical signs of the syndrome, hypalgesia and weak thumb abduction are more predictive of abnormal nerve conduction studies.

CONCLUSION

Conservative treatment options include splinting the wrist in a neutral position and ultrasound therapy

local corticosteroid injections may improve symptoms.

If symptoms are refractory to conservative measures or if nerve conduction studies show severe entrapment, open or endoscopic carpal tunnel release may be necessary.