The brachial plexus is formed from the spinal nerves or roots, the coalescence of the ventral (motor) and the dorsal (sensory) rootlets as they pass through the spinal foramen. The dorsal root ganglion contains the cell bodies of the sensory nerves; the cell bodies for the ventral nerves lie within the spinal cord.
Typically, the brachial plexus is formed from C5-T1; in some cases with there is a contribution from C4 (prefixed, 28-62%) or T2 (postfixed, 16-73%). All nerve supply to the upper extremity passes through this plexus. The brachial plexus starts at the scalenes, courses under the clavicle, and ends at the axilla. It is typically composed of 5 roots, 3 trunks, 6 divisions (2 from each trunk), 3 cords and terminal branches.
The 5 roots are named by the level with which they correspond. The C5-7 roots give off branches to form the long thoracic nerve, and the C5 root gives branches to form the dorsal scapular nerve. C5 and C6 gives branches to form the superior trunk, C7 the middle trunk, and C8 and T1 the inferior trunk. Each trunk has 2 divisions: 1 division of each of the trunks forms the posterior cord; the anterior division of the superior trunk and the anterior division of the middle trunk form the lateral cord. The anterior division of the inferior trunk forms the medial cord. The medial, lateral, and posterior cord designations describe their relationship to the axillary artery.
The superior trunk gives off the suprascapular nerve and a nerve to subclavius. The posterior cord has the upper and lower subscapular nerves, with the thoracodorsal nerve between them. The lateral pectoral nerve emanates from the lateral cord, and the medial pectoral nerve from the medial cord but with a connection between the pectoral nerves. The posterior cord then becomes the axillary and radial nerves.
The lateral cord continues as the musculocutaneous nerve; a branch from the medial and lateral cords becomes the median nerve; and a branch from the lateral branch joins the medial cord continuation as the ulnar nerve, after the medial cord gives off the medial brachial cutaneous and the medial antebrachial cutaneous nerves. The cords and branches are distal to the clavicle; the roots and trunks proximal. The plexus lies in close proximity to the axillary artery, which exits between the anterior and middle scalenes. Knowledge of this anatomy may allow localization of lesions from the physical examination.
The common mechanism for traction injuries of the brachial plexus is violent distraction of the entire forequarter from the rest of the body. These injuries usually result from a motorcycle accident or a high-speed motor vehicle accident. A fall from a significant height may also result in brachial plexus injury, either traction type or from a direct blow; penetrating injuries and low- or high-velocity gunshot wounds also are seen.
• Pain, especially of the neck and shoulder. Pain over a nerve is common with rupture, as opposed to lack of percussion tenderness with avulsion
• Paresthesias and dysesthesias
• Weakness or heaviness in the extremity
• Diminished pulses, as vascular injury may accompany traction injury.
The initial patient evaluation should occur as early as possible (usually by three months) following injury, or as soon as stabilization after the trauma permits.
The examination will consist of:
• Thorough medical history and physical examination
• Myelogram — During a myelogram, a special dye that absorbs X-rays is injected into the spinal fluid. The resulting X-ray picture shows whether the spinal nerves are injured at the spinal cord level.
• Electromyogram (EMG or electromyography) — This test measures how quickly nerves are carrying electrical signals to the muscles. A thin-needled electrode is inserted into the muscles that appear to be affected by a nerve injury. An instrument records the electrical activity in the muscle at rest and as the muscle moves (contracts).
Treatment options depend on the type and severity of the injury:
• Avulsion — the nerve is torn from the spine
• Rupture — the nerve is torn, but not where it attaches to the spine
• Stretch — the nerve has tried to heal itself (forming a neuroma), but scar tissue has grown around the injury, limiting nerve function
Immediately after injury, emphasis is placed upon physiotherapy, including range of motion activities and strengthening and controlling pain.
Improvement or recovery occurs in some patients within weeks or several months of the injury.
Surgery may be indicated if the patient doesn’t recover adequate function within several months. Surgery on the nerves, if required, should ideally occur within three to six months and not later than one year after the injury. When evaluation is delayed beyond six to nine months, treatment options are fewer and more limited, although evaluation and treatment will likely still be of value.
Microsurgical techniques are used to improve brachial plexus function. They include one or more of the following methods:
• Release from scar tissue (neurolysis)
• Nerve grafts — new nerve tissue is inserted to bridge gaps resulting from ruptured or stretched nerves (which may need to be removed). Nerve regeneration is slow, about 1 inch per month.
• Nerve transfer (neurotization) — part of a functioning nerve is transferred to replace irreparably injured nerve roots to allow more rapid recovery of function.
• In severe cases, one or more free muscle transfers may be necessary. In this procedure, a healthy muscle from the leg with its nerve and blood supply is grafted onto the injured area to restore function to the arm.
If surgery is delayed past a year, treatment may include free muscle transfer, tendon transfer and joint fusion.
PHYSIOLINE’S SPECIALISED PHYSIOTHERAPY HAS VITAL ROLE TO PLAY
At Physioline, all the members of the rehabilitation team work together so as to provide proper care and the therapy in order to:
• Relief pain
• Restore strength
• Muscle reeducation
• Restore sensation
• Prescription of orthoses
Visit Physioline for further Consultation and treatment