Carpal tunnel syndrome

Epidemiology

·       Most common entrapment neuropathy.

·       F>M, usually 30-60 years.

·       Often bilateral, but worse in the dominant hand.

Predisposing conditions

·       Manual work.

·       Flexor tenosynovitis.

·       Pregnancy.

·       Medical – hypothyroidism, acromegaly, rheumatoid arthritis, amyloidosis.

Clinical features

·       Pain – usually the most prominent symptom.

·       Aching and burning pain in fingers, hand, wrist, forearm, sometimes upper arm.

·       Worst at night and in the morning.

·       Relieved by shaking or exercising the hand.

·       Sensory – tingling and pins and needles.

·       May not be localised to the median nerve distribution by the patient.

·       May or may not be altered sensation in the median nerve distribution.

·       Tinel’s sign – percussion over the median nerve at the wrist provokes sensory symptoms.

·       Phalen’s sign – sustained wrist flexion (30 seconds) provokes sensory symptoms.

·       Wasting and weakness – most do not have these, though there may be abductor pollicis brevis wasting.

Diagnosis

·       Clinical.

·       Nerve conduction studies can be used.
- electrodes taped to skin; forearm and hand x3
- stimulus delivery; analysis to determine if impulses are slowed within the carpal tunnel - localizes site of pathology
- evalutes for neuropathy with conduction delay; demyleinating condition (as opposed to other neuropathy; ie axon loss).
- hence can help in both localization and specificity of neuropathy; confirming diagnosis of carpal tunnel
- excludes other differentials; e.g. polyneuropathy, nerve root or plexus problems, motor neuron disease, myopathies
- note that in early phase of the disease, can be normal.

Treatment

·       Change occupation.

·       Diuretics.

·       Surgical decompression.


Capral Tunnel

What is Carpel tunnel syndrome

• Symptoms and signs related to compression of the median nerve in the carpel tunnel

What are the causes

Idiopathic – often associated with pregnancy. Female:Male 8:1. 40-50’s.

Distal radius fracture

• Disease which increase volume of tissue in carpel tunnel: Rheumatois synovitis, hypothyroidism, Acromegaly, amyloidosis, Gout, Lipoma, ganglion, neuroma.

• Renal failure with AV fistula

• Daibetes increases sensitivity of nerve to damage

• Other: Myeloma, haemophilia, occupational

How is the diagnosis made

• History.

• Phalen’s test: numberness over the median nerve distribution when the hands are pushing back

• Tinnel’s test

• Nerve conduction studies

 

How do evaluate nerve conduction study?

Motor NCS

Motor NCS are performed by electrical stimulation of a peripheral nerve and recording from a muscle supplied by this nerve. The time it takes for the electrical impulse to travel from the stimulation to the recording site is measured. This value is called the latency and is measured in milliseconds (ms). The size of the response - called the amplitude - is also measured. Motor amplitudes are measured in millivolts (mV). By stimulating in two or more different locations along the same nerve, the NCV across different segments can be determined. Calculations are performed using the distance between the different stimulating electrodes and the difference in latencies.

Sensory NCS

Sensory NCS are performed by electrical stimulation of a peripheral nerve and recording from a purely-sensory portion of the nerve, such as on a finger. The recording electrode is the more proximal of the two. Like the motor studies, sensory latencies are on the scale of milliseconds. Sensory amplitudes are much smaller than the motor amplitudes, usually in the microvolt (μV) range. The sensory NCV is calculated based upon the latency and the distance between the stimulating and recording electrodes.

What are the non-surgical treatments

Night splint, steroids injections, diuretics (non value)

 

 

What are the attachments of the flexor retinaculum

Radial: Tubercle of scaphoid and ridge of trapezium – splits on the radial side to enclose the tendon of FCR.

Ulna: Pisiform and hook of hamate

What structures pass superficial to carpel tunnel

Superficial branch of ulna nerve, ulna artery, palmaris longus tendon and palmar cutaenous branch of median nerve.

What are the contents of the carpel tunnel

• Flexor pollicis longus tendon – the radial bursa envelopes these tendons

• FDS tendons (in two rows)

• FDP tendons in a single row – a common synovial sheath enclosed the long flexors of the fingers which is open in the radial side (ulna bursa) to allow blood vessels to the tendons to enter

• Median nerve –lie between the FPL and FDS to middle finger

• FCR lies in its own compartment and is not part of the carpel tunnel

What is the arrangement of the tendons of FDS

Those to the ring and middle fingers form a superficial row with the tendons to the index and little finger in a deep row

What are the variations of the recurrent motor branch of the median nerve

50% - given off the radial side of the median nerve distal to the flexor retinaculum and is recurrent

33% - given off the radial side of the median nerve in the carpel tunnel and passes through the tunnel and then takes a recurrent course to innervate the thenar muscles

20% - arises from the radial side of the median nerve and passes through the flexor retinaculum  (non-recurrent)

Rare variants:

    Arising from ulna side of median nerve and takes a recurrent course across the superficial aspect of the flexor retinaculum

    High division of median nerve so two branches lie in the carpel tunnel

How do you differentiate the nerve from the tendons

The nerve is white with a fine vaso nervorum on its surface. The tendon bulge in their synovial sheaths

How do you perform carpel tunnel release

• In an appropriately consented, prepared patient

• I use nerve conduction studies to confirm diagnosis.

• I check the nerve conduction studies with the patient and mark the side for surgery in anesthetic bay

• GA without local anesthetic.

• Elevate and exsanguinate arm. Apply high arm tourniquet. Inflate to 200mmHg. Note tourniquet time.

• Sterile prep and drape with arm on arm table using a hand board or lead hand to control fingers

• Mark incision with pen: line of ulna side of ring finger. From distal dominant crease of wrist to transverse line drawn from base of outstretched thumb

• Incise through skin. Use skin hooks to place palmar aponeurosis on tension and incise through using scapel. Care not to damage superficial palmar arch at distal limit of wound

• Place small self retaining retractor. Make a nick in the flexor retinaculum with scalpel to the ulna side of midline.

• I place a Macdonald dissector under the flexor retinaculum to clear any adhesions

• With the Macdonald dissector separating any underlying structures I incise the flexor retinaculum under direct vision from the distal limit using the scalpel whilst keeping the median nerve in direct vision.

• I identify and protect the motor branch of the median nerve.

• I inspect the tunnel for other space-occupying lesions – Lipoma or ganglion

• I lift the skin of the wound proximally using the skin hooks to ensure that there is no remaining restriction of the nerve. If any fibers remain these are divided under vision (without extending the skin incision) protecting the median nerve with the Macdonald dissector using iris scissors.

• It is my practice to deflate the tourniquet and achieve secure haemostatsis with biplaor diathermy.

• I observe pulsitile vascular flow to the median nerve

• Once haemostasis is complete, I close the skin using interrupted 4/0 Nylon to skin only.

• I apply a Telfor dressing, velban and crepe so that the wrist is held in a position of dorsiflexion to prevent bow stringing of the tendons

What are the complications

• Damage to the motor branch of median nerve – if this occurs repair immediately using an operating microscope

• Damage to superficial palmar branch of median nerve causing anesthesia and painful neuroma

 

What is the pathogenesis of nerve compression syndromes

Direct compression against the nerve is associated with ischaemia

• Initial temporary ischaemia with certain positions produces parasthesia

• With consistent chronic compression, demyelination occurs with persistent symptoms of pain and weakness

• As compression progresses Wallerian degeneration occurs and the nerve segment ceases to function

What other processes lead to nerve damage

• Transection – unless the nerve epineureum is re-approximated nerve re-growth cannot occur

Nerve infarct due to vasculitis or atherosclerotic disease

Infalmmatory disorder – monomyelic amyotrophy – a focal motor neuron cell loss

Metabolic disorders – Diabetes, hypohyroidism

What is the significance of asymptomatic nerve conduction defects

If slowing occurs across a certain segment without symptoms, a clinical syndrome is not considered to exist until symptoms develop.

How do you interpret nerve conduction studies

• Focal entrapments of radial, median or ulna nerves show evidence of conduction slowing and block across the affected segments.

• Electromyography confirms the diagnosis and provides insight into lesion severity

In plexopathy, abnormalities are found in several nerves emanating from one region of brachial plexus (eg upper trunk). EMG may show fibrillation potentials and positive sharp waves and chronic reinnervation in muscles innervated by the upper trunk

In radiculopathy sensory and motor studies are usually normal. Abnormalities are identified on needle examination and affect the muscles derived from involved roots.

What about imaging

• MRI of cervical spine may complement EMG findings or provide additional information

What are the other nerve compression syndromes

• Commonly ulna and median nerve entrapments

• Ulna neuropathy at elbow may be due to

Compression in the epicondylar groove due to repeated subluxation of the nerve with elbow flexion over the medial epicondyle.

Cubital tunnel syndrome: Compression of the nerve between the two heads of flexor carpi ulnaris with repeated elbow flexion.

• Compression of the ulna nerve at the elbow is the second most common nerve compression. Can be diagnosed with nerve conduction studies showing conduction velocity slowing and high resolution US showing nerve thickening

• Commonly treated with nocturnal splinting at 60 degrees and injection of steroids

• Surgical options are to split the aponeurosis between the two heads of flexor carpi ulnaris and transpose the nerve from the medial epicondylar groove into the forearm

Compression of ulna nerve at the wrist

Compression in Guyon’s canal – Compression in the space between the pisiform and the hamate through which the ulna nerve passes into the hand. May be occupational (due to hand posture during work) due to reduced volume in canal due to ganglion cyst, trauma, arthritis or compression against a bicycle handle.

• Diagnosis confirmed by nerve conduction and EMG

• Non-surgical treatment includes a wrist brace, occupational therapy to reduce pressure on nerve at wrok, NSAIDS

• Surgical decompression of Guyon’s canal

Pronator syndrome

Entrapment of median nerve in proximal forearm where it passes through pronator teres muscle

• Caused by hypertrophy of muscle in active people (eg professional bicycle riders).

• Produces forearm pain and loss of sensation over thenar eminence

• Treatment is to reduce activity producing symptoms, NSAIDS, injection of methylprednisolone and lignocaine.  Surgical decompression is used if the disability persists

Meralgia parasthetica

• Entrapment or compression of the lateral Cutaneous nerve of the thigh as it passes between the ilium and inguinal ligament.

• The syndrome consists of pain and anesthesia in the distribution of the nerve in the anterolateral thigh.

  Nerve conduction studies are unhelpful generally

• Common causes include obesity, tight garments and scar tissue.

• Pregnancy and diabetes may be contributory factors

• Inject LA with or without US-guidance to confirm diagnosis (pain goes away)

• Conservative treatment by advice to wear less tight clothes, loose weight is used first

• Local steroid injections

• Anticonvulsants

• Surgical decompression (sectioning the inferior slip of the attachment of the inguinal ligament to ASIS) or sectioning the LFCN as it exits the pelvis

• An incision is made 1cm medial to ASIS extending 4cm into thigh

• The deep fascia is incised (as the nerve lies deep to deep fascia of thigh).

• The nerve is found at the anterior border of sartoius and followed proximally to entrapment site beneath inguinal ligament

• All constricting bands are divided so that the nerve lies quite free.

• For recurrent disease, the nerve is pulled down and divided close to the inguinal ligament so that the divided end lies above the inguinal ligament.