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Nerve entrapment syndromes

Posted on 15. Apr, 2009 by admin in Anatomy

Nerve entrapment syndromes arise because of increased pressure applied to a nerve as it traverses a closed space.

The exact mechanism of nerve damage is not completely understood; it may include varying degrees of friction and ischemia.

Here is an image to visualize the SEVEN important locations of nerve entrapments commonly tested on the boards. Click on the image for a larger view.

The SEVEN important anatomical sites of nerve entrapments:

1. Thoracic outlet

2. Shoulder girdle

3. Elbows and forearm

4. Wrist and hand

5. Pelvic region

6. Knee region

7. Ankle and foot

1. THORACIC OUTLET SYNDROME

The thoracic out let is made up of three triangular outlets through which the subclavian vessels and the lower trunk of the brachial plexus pass through. (spaces are shown in orange on the right hand side)

The first triangle is (1) the space between the scalene muscles and the first rib.

The second triangle is (2) the space between the clavicle, superior margin of the scapula, and the first rib.

The third triangle is (3) the space beneath the Pectoralis minor muscle.

2. Shoulder girdle (Shoulder-girdle syndrome)

Entrapment of the long thoracic nerve can produce painless paralysis and winging of the scapula.

Impingement of the Suprascapular nerve causes diffuse shoulder pain with winging of scapula.

3. Elbows and forearm

Important entrapment to remember in these locations are:

• Radial tunnel syndrome

• pronator syndrome

• high radial nerve palsy

• lateral antebrachial cutaneous nerve entrapment syndrome

• ulnar nerve entrapment at the elbow and the forearm.

Radial tunnel syndrome(RTS) and Pronator syndrome

- radial tunnel syndrome may result from radial nerve compression in the region of the lateral epicondyle

- The pronator syndrome results from median nerve entrapment by the pronator muscle

RTS vs. Tennis elbow (Lateral Epicondylitis)

Night pain is more common in RTS than lateral epicondylitis.

The pain in RTS is usually a dull ache compared to the sharp, knife-like pain of lateral epicondylitis.

Cubital tunnel syndrome

The cubital tunnel is a fibroosseous canal formed by the medial condyle, ulnar collateral ligament, and flexor carpi ulnaris muscle. Elbow flexion decreases the volume of the channel.

Cubital tunnel syndrome presents with paresthesias along the lateral forearm, wrist, and fourth and fifth digits; it may be bilateral.

A positive Hoffman-Tinel test (tapping over the nerve) helps locate the site of entrapment, often at the ulnar groove. Pain also may be reproduced by directly palpating the nerve

4. Wrist and hand

Carpal tunnel syndrome

is the most common nerve entrapment disorder.

The clinical features of carpal tunnel syndrome are variable, but usually include pain and paresthesia in the thumb, first two fingers, and the medial half of the ring finger (the distribution of the median nerve).

5. Pelvic region

• Obturator nerve entrapment

• Lateral femoral cutaneous nerve entrapment (meralgia paresthetica)

Obturator nerve entrapment = pain in the groin and paresthesia that travels down the inner aspect of the thigh

Meralgia paresthetica = Entrapment of the lateral femoral cutaneous nerve most commonly occurs as it passes under the lateral aspect of the inguinal ligament, medial to the anterior superior iliac spine. Intermittent paresthesia, hypesthesia or hyperesthesia felt over the region of the upper anterolateral thigh.

6. Knee region

Entrapment of the peroneal nerve

at its crossing of head of the fibula

Causes:

• excessive crossing of legs
• diabetes mellitus
• marked weight loss
• Metastasis (rare)

Leads to peripheral motor weakness involving the ipsilateral foot. A foot drop may develop in more severe cases.

7. Ankle and foot

• Tarsal tunnel syndrome (TTS)

• Anterior tarsal tunnel syndrome

• Morton’s Neuroma

Tarsal tunnel syndrome = a fibroosseous canal formed by the laciniate ligament as it extends from the medial malleolus down onto the calcaneus. Compression of the posterior tibial nerve as it courses through this canal may cause numbness and tingling that is felt in the first three toes.

Anterior tarsal tunnel syndrome = the entrapment of the deep peroneal nerve as it descends over the top of the saddle bone deformity. A Tinel’s sign can be elicited at the top of the foot with a positive Tinel’s sign resulting in electrical shock sensation to the first and second toes. This syndrome is often seen in skiers who wear clogs or people who lace their shoe very tightly.

Morton’s Neuroma = a painful condition of the forefoot that is caused by the entrapment of the common intermetatarsal nerve as it passes through the forefoot to the toes.

-Admin

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