Birth brachial plexus palsies
These result from difficulties during birth and are frequently associated with shoulder dystocia in manipulating the head to one side to free the shoulders, the brachial plexus (the large network of nerves that connect the spinal cord to the arm and hand) may be stretched and damaged.
A Brachial plexus lesion can be associated with a broken collar bone (clavicle) or upper arm bone (humerus) and Horner's Syndrome (eyelid droop and a smaller pupil on the same side as the weak arm). Birth brachial plexus injuries are classified according to severity:
- Group 1. There is a paralysis of the shoulder muscles, deltoid, supra and infraspinatus and of the biceps. This implies a lesion of C5 and C6 only. Complete recovery is seen in 90% of the cases.
- Group 2. The C7 nerve root is affected in addition to C5 an C6 and this results in a lack of wrist extension as well as shoulder and elbow impairment. Full recovery still occurs in about 70% of these children but the whole process is much slower than in the first group.
- Group 3. This is a complete brachial plexus lesion with all nerves involved and it is obviously a more severe lesion. At birth the palsy of shoulder, elbow, wrist and hand is complete. Less than 50% of these children show good functional recovery.
- Group 4. This is a complete brachial plexus lesion with an associated Horner’s syndrome. Only few children have good spontaneous functional recovery.
Whether to operate on the nerves or not is decided following clinical examination and neurophysiological studies (EMGs). An initial assessment by the surgeon is recommended at one month of age not only to determine requirement for surgery but also to direct the rehabilitation process.
Of major importance in the treatment of these children is the risk of long term secondary deformities such as shoulder subluxation/dislocation and the correction of lack of function by means of muscular transfers. In our Unit we have been working in the last five years on new surgical procedures to correct the shoulder deformity and maximise function as the child grows.
Adult brachial plexus injury
The brachial plexus is formed by five spinal nerves from C5 to C8 and one thoracic T1, which exit from the spinal cord and emerge in the posterior triangle of the neck where they constitute the upper (C5-C6), middle (C7) and lower trunk (C8-T1).
The brachial plexus connects the brain and the spinal cord to all the structures in the upper limb, providing control of movement and perception of varied sensations. All the trunks divide just above the clavicle level. The suprascapular and axillary nerves, formed mainly by the 5th cervical nerve, supply the muscles of the shoulder. The musculocutaneous nerve, which is mainly formed by the 5th and the 6th cervical nerves, innervates the muscles for elbow flexion. The radial nerve, which is formed by 6th, 7th and 8th cervical nerves, passes to the posterior aspect of the limb and gives branches to muscles responsible for elbow, wrist and fingers extension. The median and ulnar nerves pass down to the anterior aspect of the limb and they are responsible for innervation of the muscles of flexion of wrist and fingers and all the small muscles of the hand. These two major nerves bring sensory impulses from the hand to the cerebral cortex.
Injury in adults usually results from motorcycle or car accidents or sports trauma. These injuries may involve each individual root:
- Avulsion – the root is torn from the spinal cord.
- Rupture - a tear is located at the root level.
- Lesion in continuity – the nerve is ruptured inside but still in continuity outside.
Symptoms of brachial plexus injury can include loss of sensation or partial or complete paralysis in the limb. When pain with neuropathic characteristics is present from the beginning the most likely diagnosis is of avulsion. If there is a Tinel’s sign (an electric sensation shooting down the arm) when tapping in the posterior triangle of the neck the most likely diagnosis is rupture. An urgent clinical assessment is always required and an urgent operation performed if indicated. The outcome of nerve repairs is significantly better if carried out within hours/days from the injury.
Secondary surgery at a later stage, even after many years by means of muscular transfers can improve limb function. Physiotherapy and occupational therapy are essential in the rehabilitation process and must be started as soon as the clinical picture allows it and must be supervised by the treating surgeon.
Injuries to the lumbosacral plexus
In the same way that the brachial plexus connects the spinal cord to the upper limb, the lumbo-sacral plexus provides all the nerves to the lower limb. A complete or partial injury to the lumbo-sacral plexus therefore leaves the patient with a deficit in the sensation and/or movement in the lower limb and pain which has got the typical characteristics of burning/cramping or sometimes tingling. Movements of hip, knee, ankle, foot and toes can be affected to a different degrees up to a complete injury where the whole limb is flail and there is no control of the hip with complete paralysis of the gluteal muscles. If the gluteal muscles are still working the possibility of a lesion of the sciatic nerve proper is more likely.
The treatment and the likelihood of full recovery depends on the cause and the delay between damaging event and treatment itself. In some cases the lesion is at the level of the origin of the lumbo-sacral plexus and that means inside the spinal canal where the nerves originate. In these cases the only surgical option is reconnection of the nerves at this level. Sometimes the reconnection is performed with nerve grafts (nerves taken from other parts of the body, usually the sural nerve) directly to the femoral and sciatic nerve).
Peripheral nerve injuries in upper and lower limbs
Trauma to the nerves in upper and lower limbs is often caused by road traffic accidents, industrial or sporting injuries. They may or may not be associated with bony injury in the form of fractures. The severity of injury can be classified as:
- Degenerative: the axon has been damaged with complete loss of function (tapping on the terminal part of the damaged nerve filament the patient perceives a sort of “electric” sensation running down within the distribution of the damaged nerve.
- Non degenerative: the nerve is still intact and therefore potentially able to work but it is non-functional. This may be due to a lack of local blood supply to a nerve or where the nerve has been compressed at a point of relative fixity in the course of sustaining an injury. In both situations the nerve loses the capacity to effectively transmit electrical signals to the muscles. This situation may persist for days, weeks and sometimes months. If a compression force is released from the nerve, the recovery will be full. Where compression persists, recovery may not occur or may be sub-optimal or cause residual neuropathic pain.
Fractures or joint dislocations with associated nerve injuries
The particular mechanism of an injury causing bone fracture or joint disclocation can lead to a range of damage to nerves such that they no longer transmit impulses normally. A greater incidence of high-grade nerve injuries occurs with open fractures, with nerves either being lacerated or interposed between fracture fragments. Dysfunction of peripheral nerves results from damage to the neuron, to the Schwann cells (that insulate the nerve axons), or to the outer myelin sheath. For example, the force of injury in shoulder dislocation will affect the type of nerve injury sustained. Where fractures are associated with dislocations, as is often seen in shoulder dislocations, it is vitally important to anatomically reduce and fix any bone fractures seen. This enables good function to be restored when nerve recovery occurs.
Compression injuries can be induced by fractures, hematomas, and compartment syndrome, which causes high pressure in the surrounding tissue that compresses the arterial blood supply of the nerve, with possible cell damage and cell death. Although the peripheral nervous system is relatively robust, delays in assessment and treatment of compartment syndrome can lead to nerve injury in the forearm. In a fracture, concussion or compression of the nerve causes neurapraxia and fractures of the humerus can cause radial nerve paralysis.
In cases of traumatic hip dislocation, such as a bad fall or road traffic accident, the sciatic nerve can be compressed by the head of the femur, or lacerated by bone fragments. Imperfect healing can also lead to nerve damage, for example in elbow trauma, scarring can jeopardize the normal gliding of the ulnar nerve in the elbow because of adherence to scar tissue, fracture callus, or heterotopic bone.
Nerve injury may be apparent immediately after injury but may also develop later. For example, even without fracture or dislocation of the knee, nerve function to the foot may be affected by a stretch or contusion injury.
Nerve injuries sustained at time of operation
The severity and range of injury resulting from, for instance, a motor accident may mean that the complex surgery required to repair multiple fractures and joint dislocations could also damage surrounding nerve tissue. Complications from surgery can include infection, bleeding and delayed wound healing or scarring of the primary surgical site, there is a risk that nerve function in the region of the injury – with respect to sensory or motor function – will be lessened, or pain may develop.
In hip replacement surgery, nerve damage may be sustained either by direct trauma, by traction or as a result of pre-operative intraneural anaesthetic injection. In cases of nerve crush injury, surgery may be delayed for several weeks after any operation to fix a fracture or replace a joint to see what nerve function recovery is achievable by normal nerve re growth.
Benign and malignant tumours of nerves
Nerve tumours can be divided into benign and malignant. Benign lesions are usually Schwannomas or neurofibroma and can be removed without any added neurological deficit by working inside the nerve and preserving all the fascicles which are working. The risk of postoperative nerve partial dysfunction is less than 1% in a specialized unit. For malignant lesions the operation is life saving and the function of the nerve must not be protected, given that it is the nerve itself which is the organ of origin of the tumour. In these cases a radical resection is required.
Sometimes radiotherapy and/or chemotherapy can be helpful, depending upon the exact type of tumour diagnosed.
Entrapment neuropathy including neurogenic thoracic outlet syndrome
A number of different peripheral nerves may have their normal function impaired by entrapment, with abnormal compression causing loss of sensation, pain or limb function. For example, the ulnar nerve runs the length of the arm from the brachial plexus in the shoulder to the hand. It is often injured in an elbow fracture or dislocation as it is near the skin where it crosses the elbow.
As the nerves pass from the shoulder down the arm to the hand, they can be pinched in a number of tunnels and outlets, which give their names to a range of conditions, including:
Thoracic outlet syndrome
Produced by compression of brachial plexus as these nerves pass from the neck to the arm. Pressure on the nerve may result from movement of the collar bone (e.g. when fractured) or shoulder girdle or by swelling or abnormalities in the surrounding muscles. Commonly, this occurs in neck injury following road accidents and sometimes in young athletes such as basketball players where much of the activity is overhead. Some people develop a characteristic pattern of muscle wasting and altered sensation with or without pain caused by compression of the lower trunk of the brachial plexus. This is termed neurogenic thoracic outlet syndrome or Gilliatts syndrome.
Carpal tunnel syndrome
This is produced by entrapment of the median nerve which leads to numbness in the thumb, index, middle and half of the ring fingers.
Cubital tunnel syndrome
Compression of the ulnar nerve at the elbow may cause impaired movement or loss of sensation in the wrist and hand. Initial numbness may persist and eventually become associated with weakness in the hand and cause the two smallest fingers to curl up.
Neurogenic pain surgically
Damage to peripheral nerves during surgery or in trauma may result in neuropathic (or neurogenic) pain. In some circumstances this may be significantly improved by surgical decompression of the peripheral nerve trunk involved. Best results are seen where a clear tether of the nerve is seen at operation and where the operation is carried out promptly.
Limb function restoration with surgical reconstruction after peripheral nerve injury
Several methods are available to restore limb function following a nerve injury, these include:
- Muscle transfers (diverting a muscle from one function to restore another).
- Nerve transfers (diverting a nerve or part thereof to restore function to another muscle).
- Joint fusions (stopping a joint from moving in order to maximise the function of available working muscles).