MEDIAN NERVE

PATH OF MEDIAN NERVE.

It is formed from the merger of the medial and lateral cords of the Brachial Plexus. It courses with the brachial artery on the medial side of the arm between biceps brachii and brachialis. It is initially lateral to the brachial artery, but in the distal arm it crosses anteriorly to run medial to it.

Through the cubital fossa the medial nerve passes medial to the brachial artery, in front of the ulna tuberosity and deep to the biceps.

The median nerve arises from the cubital fossa and passes between the two heads of pronator teres. As it passes through pronator teres, it gives off the anterior interosseus nerve, which runs along the interosseus membrane to supply FPL, FDS, pronator quadratus and the lateral half of FDP.

The unbranched nerve continues down the forum between FDS and FDP. The median nerve innvervates all the anterior superficial and intermediate muscles of the forearm except for FCU. Just before the wrist, the median nerve becomes superficial, lying between FCU and FDS. Here it gives off the palmar cutaneous branch which supplies the central part of the palm and the thenar eminence. Because the palmar cutaneous branch passes superficial to the retinaculum, it is not damaged in carpal tunnel syndrome, and thus sensation is still felt in the supplied areas.

The median nerve then continues through the carpal tunnel and passes anterior and lateral to the FDS tendons. From there it sends off a recurrent branch to the thenar compartment. It also gives off digital cutaneous branches which supply the lateral 3.5 digits of the palmar side, and the index, ring and middle finger of the dorsal side.

Confirm Diagnosis of CTS - Frank

Examination
Diagnosis of carpal tunnel syndrome is based on the history of symptoms, presence of risk factors, physical and neurological examination, and diagnostic tests. 

Neurological examinations test the three thenar muscles that abduct, flex and oppose the thumb (the abductor pollicis brevis, flexor pollicis brevis and opponens pollicis respectively). 

Following this there are three main tests designed to reproduce symptoms. Look for wasting in the median nerve distribution, and loss of motor (thenar muscle strength: weak thumb abduction) and sensory function. 
Tinel’s Sign – Holding the wrist in extension and tapping the palm sharply causing tingling sensation.
Phalen’s Maneuver – Hold the wrist in passive wrist flexion for roughly 60 seconds. 
Durkan Test – Examiner presses thumb over carpal tunnel, holding pressure for around 30 seconds. 

The Durkan test is the most reliable of the three, having proven to be accurate 90% of the time in Durkan’s study. Tinel’s sign is the least reliable with negative diagnoses in up to 30% of patients with electrophysiologically proven median nerve compression. Phalen’s test has a false negative rate of postive LR 1.3, negative LR 0.7).

Other conditions may also be misdiagnosed as carpal tunnel syndrome including inflammation (radiculopathy) of nerve roots C6 and C7 in the cervical spine and compression of the median nerve outside the carpal tunnel. Thus, if, based on history and physical examination, a CTS diagnosis is suspected but not clear, patients will likely be tested electrodiagnostically with nerve conduction studies and electromyography; MRI or ultrasound imaging are also used.

Electro Diagnosis
Nerve conduction velocity (NCV) and electromyography (EMG) are used to evaluate nerve and muscle function. 

NCV involves placing electrodes on the skin above the median nerve to monitor the speed at which an impulse travels along the nerve. 
In essence, NCV uses deploys electrodes at different parts of the skin over the nerve, where one electrode stimulates and the others monitor the subsequent electrical activity. The time for the electrical impulse to travel and the distance between the electrodes is used to calculate the speed. Slowing across the wrist for the motor and sensory latencies of the median nerve indicates focal compression of the median nerve at the wrist.

An EMG detects the electrical potential generated by muscle cells when these cells contract, and also when the cells are at rest. For CTS, EMG involves placing small electrodes in the form of a needle into the abductor pollicis brevis muscle to detect abnormalities that may indicate that the median nerve supplying the muscle is damaged. 

The EMG is often performed simultaneously with the NCV, and thus the two are often referred to together as EMG/NCV studies.

http://www.medterms.com/script/main/art.asp?articlekey=34030
http://www.arthritis-treatment-and-relief.com/nerve-conduction-test-carpal-tunnel-syndrome.html
http://www.neurohaven.com/emg1.htm
http://www.fpnotebook.com/Ortho/Exam/CrplCmprsnTst.htm
http://www.ejbjs.org/cgi/content/abstract/73/4/535
http://www.neurologychannel.com/carpaltunnel/diagnosis.shtml
http://www.ninds.nih.gov/disorders/carpal_tunnel/detail_carpal_tunnel.htm

PCL 08 Ulnar nerve palsy- Alan

Ulnar nerve palsy is defined as compression, damage or trapping of the ulnar nerve as it runs towards the hand from the brachial plexus.

 

Symptoms and signs

-          Numb and tingling feeling on little finger, ulnar half of ring finger

-          Weakness of grip

-          Clawed hand

-          Intrinsic muscle wasting (rare)

 

Causes

Compression: fracture, dislocation or leaning on the elbow, wrist

-          Dislocation of the elbow joint can cause entrapment of the ulnar nerve

Golfer’s elbow (aka Pitcher’s elbow)

-          Medial epicondylitis

-          Can occur with repeated use of wrists and clenching fingers

Cubital tunnel syndrome

-          Ulnar nerve is elongated during elbow flexion, intraneural pressure is increased leading to compression of the nerve

Guyon canal syndrome

-          Compression of the ulnar nerve by the Guyon Canal between pisiform and hamate carpal bones

-          Caused by repeated wrist and hand movement, pressure (cyclists, weightlifters), cyst within canal, hamate fracture, arthritis, clotting of ulnar artery

 

Reference

http://www.doctorslounge.com/neurology/diseases/ulnar_palsy.htm

http://www.patient.co.uk/showdoc/40001161/

http://www.emedicine.com/orthoped/TOPIC479.HTM

http://www.orthogate.org/patient-education/hand/guyons-canal-syndrome.html

 

Causes/ Risk Factors

- more likely to occur in woman(thought to be due to smaller carpal tunnel in woman)
- usually affects dominant hand
- trauma or injury to the wrist that cause swelling
- overactivity of the pituitary gland
- hypothyroidism
- rheumatoid arthritis
- mechanical problems in the wrist joint
- work stress
- repeated use of vibrating hand tools;
- fluid retention during pregnancy or menopause
- the development of a cyst or tumor in the canal

Prognosis for CTS - Fern

Without surgery:
- If CTS is due to an inflammatory arthritis (eg rheumatoid arthritis) then symptoms may be reduced by treating the underlying cause
- untreated, nerve and muscle damage can occur.
- Long-term compression commonly leads to thenar atrophy and weakness of the thumb and index fingers.
With surgery:
- Complications: nerve damage (usually temporary), infection, pain, scarring, stiffness.
- Usually gives a substantial improvement, with about 70% of people “completely or very satisfied with the outcome of their surgery”
- Some patients get immediate relief
- May still have residual numbness, pain, stiffness or weakness
- lower levels of satisfaction associated with consuming > two alcoholic drinks a day, smoking, lower mental and physical health status before surgery, and exposure to repetitive, forceful activity ( not including keyboard use)
- return to strenuous work can cause return of symptoms
- may take weeks to months to regain maximal use of the hand and wrist
- Operating on both hands at once will make someone completely incapacitated for 2 weeks, requiring help at home
- Recovery time may be quicker after endoscopy than open release
- Physical therapy can help patients recover faster - hand exercises can help restore circulation, muscle strength, and joint flexibility in the hand and wrist

Anatomy of the Wrist

Anatomy of the Wrist - Penny

Bones

Some Lovers Try Positions That They Can't Handle

(Scaphoid Lunate Triquetrum Pisiform Trapezium Trapezoid Capitate Hamate)

Nerves

Ulnar Nerve

Median Nerve

Radial Nerve

Arteries

Veins

PCL 08 Signs and Symptoms of Median Nerve Palsy

There are three main entrapment syndromes involving the median nerve and its branches

• Carpel Tunnel Syndrome

- painful during night time and relieved by changing hand posture
- numbness and parathesia (burning and tingling sensation) in thumb, index and middle fingers
- difficulty gripping and forming a fist
- wasting of thenar muscles in chronic patients

• Anterior Interosseus Nerve Palsy (Kiloh-Nevin Syndrome)

Interosseus is a branch off the Median nerve and supplies the deep muscles in the forearm (FDP, Flexor pollicus longus, pronator quadratus). Compression of this nerve affects these muscles.

- weakness in index finger and thumb
- weakness of interphalangeal joint (FDL) in thumb and distal interphalangeal joint (FDP) in index
-can be seen through pinching attitude:
normally pinching of thumb and index are flexed (forms a circle)
with nerve deficiet the finger and thumb are extended/hyperextended (flat oval)

• Pronator Syndrome

Occurs when the median nerve is compressed at pronator teres. Uncommon, easy to misdiagnose as CTS

- almost identical symptoms to CTS due to compression of median nerve
- differences:
pain is exacerbated by repetitive elbow flexion
pain on the volar surface of the forearm after prolonged pronation
not aggrivated during night time (pronator teres not associated with wrist flexion)

Myat

Anatomy of the Arm

In the arm, the ulnar nerve is the largest of the two terminal branches of the medial cord of the brachial plexus. The Ulnar nerve runs inferior and medial to the axillary artery in the axilla and upper arm. It then passes anterior to the triceps muscles and enters the ulnar groove between the medial epicondyle of the humerus and the olecranon. The ulnar nerve is superficial and easily palpated posteior to the medial epicondyle. Before entering the forearm the ulnar nerve sends articular bracnhes to the elbow joint.

In the proximal forearm the ulnar nerve passes between the two heads of the flexor carpi ulnaris, descending deep to the muscle on the surface of the flexor digitorum profundis (accompanied by the ulnar artery) and then passes medial to the artery and lateral to the flexor carpi ulnaris, becoming relatively superficial in this distal part of the forearm being covered only by fascia and skin. Near the pisiform bone it passes superficial to the flexor retinaculum and ends by dividing into superficial and deep branches.

In the forearm the ulnar gives off 4 branches, 2 muscular branches of ulnar nerve (ennervating Flexor carpi ulnaris and ulnar half of the Flexor digitorum profundus), the palmar branch of ulnar nerve and the dorsal branch of ulnar nerve.

In the forearm it branches into two the superficial branch of ulnar nerve and the deep branch of ulnar nerve.

The movements that the ulnar is responsible for are:
-adduction and abduction of the fingers (interossei)
-adduction of the thumb (adductor pollicis)
-flexion and adduction at the wrist (interossei)

Sources:
http://www.acnr.co.uk/pdfs/volume3issue2/v3i2anatomy.pdf
http://depts.washington.edu/anesth/regional/ulnarnerve.html

Definition of carpal tunnel syndrome - Eunice

Definition

Carpal tunnel syndrome (CTS) or median nerve neuropathy at the wrist, a condition in which the median nerve is compressed at the wrist, can cause pain, tingling, numbness, and weakness in the fingers and thumb. True carpal tunnel only elicits symptoms in the thumb, index and middle fingers, along the median nerve distribution, but some patients may experience symptoms in the palm as well.

http://www.medicinenet.com/carpal_tunnel_syndrome/article.htm#1whatis

Carpal Tunnel Syndrome -- Management

GENERAL TREATMENT
1. Avoid repetitive wrist and hand motions that may exacerbate symptoms or make symptom relief difficult to achieve.
2. Ergonomic measures to relieve symptoms depend on the motion that needs to be minimized. Patients who work on computers, for example, may benefit from improved wrist positioning or the use of wrist support (still is controversial).
3. Wrist splints may be helpful for patients in professions that require repetitive wrist motion.
4. Conservative treatments include oral corticosteroid therapy and local corticosteroid injections.
5. Surgery --> considered when carpal tunnel syndrome does not respond to conservative measures.

WRIST SPLINTS
Splinting the wrist at a neutral angle helps to decrease repetitive flexion and rotation, thereby relieving mild soft tissue swelling or tenosynovitis.
--> Most effective when applied within three months of the onset of symptoms.
The optimal splinting regimen depends on the patient's symptoms and preferences.
--> Nightly splint use is recommended to prevent prolonged wrist flexion or extension.
--> Some patients choose to wear a wrist splint all of the time. Full-time use has been shown to provide greater improvement of symptoms and electrophysiologic measures.

ORAL MEDICATIONS
Diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs), pyridoxine (vitamin B6), and orally administered corticosteroids have been used with varying degrees of success in patients with carpal tunnel syndrome.
But… Few high-quality trials have evaluated these treatments.
--> Orally administered corticosteroids have been shown to be more effective than NSAIDs or diuretics in the short-term treatment of carpal tunnel syndrome. The optimal corticosteroid dosage remains to be determined.

LOCAL INJECTION
Combined injection of a corticosteroid and a local anaesthetic into or proximal to the carpal tunnel can be used in patients with mild to moderate carpal tunnel syndrome. Such injections can be diagnostic as well as therapeutic.
Direct injection into the carpal tunnel carries the potential for needle injury to the median nerve, intratendinous injection and tendon rupture, or dysesthesias (secondary to intrafascicular injection) that may persist for months.

An alternative approach is to place the injection proximal to the carpal tunnel, rather than directly in it. This approach lowers the risk of damage to the median nerve and theoretically treats concomitant swelling at the volar side of the forearm.

With any method, injection of corticosteroid into the median nerve must be avoided.
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. While a poor response to local corticosteroid injection does not predict a poor surgical result, a favourable response has been associated with a satisfactory surgical outcome.

ULTRASOUND THERAPY
Ultrasound therapy may be beneficial in the longer term management of carpal tunnel syndrome.

SURGERY
Carpal tunnel release surgery should be considered in patients with symptoms that do not respond to conservative measures and in patients with severe nerve entrapment as evidenced by nerve conduction studies, thenar atrophy, or motor weakness.
--> Surgery may be effective even if a patient has normal nerve conduction studies.

Carpal tunnel release surgery is an outpatient procedure that is performed using regional anaesthesia. The traditional surgical approach uses a long palmar curvilinear incision to facilitate division of the transverse carpal ligament and its overlying structures.

Endoscopic carpal tunnel release is a newer procedure that allows division of the transverse carpal ligament with the overlying structures left intact. Use of this procedure purportedly lessens scar formation and allows an earlier return to work and activities of daily living. The wrist is generally splinted for three to four weeks after surgery.

Complications of surgery include:
- injury to the palmar cutaneous or recurrent motor branch of the median nerve
- hypertrophic scarring
- laceration of the superficial palmar arch
- tendon adhesion.
- Postoperative infection
- Hematoma
- Arterial injury
- Stiffness
- Reflex sympathetic dystrophy
If carpal tunnel release is incomplete, symptoms may recur.

PREGNANCY
Alterations in fluid balance may predispose some pregnant women to develop carpal tunnel syndrome. Symptoms are typically bilateral and first noted during the third trimester. Conservative measures are appropriate, because symptoms resolve after delivery in most women with pregnancy-related carpal tunnel syndrome.35

http://www.aafp.org/afp/20030715/265.html
http://www.emedicine.com/pmr/topic21.ht