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    Nerve Injury

    What is a nerve?

    A nerve is like a cable with an outer layer that protects the multiple thin inner cables (nerve fibres). The inner cables,that carry messages back and forth to the brain and information about feeling and from the brain to tell the muscles to contract.

    What are the modes of nerve injury?

    There are various causes of nerve injury like trauma, stretch injury, compression like carpal tunnel/ cubital tunnel syndrome, tumor etc.

    How do you explain nerve injury?

    There are three basic types of injury to a nerve:

    • Type I: the nerve is bruised and stops working properly for a short period of time. All the inner cables (nerve fibres) remain intact. With this type of injury the nerve normally recovers fully and leaves no deficit.
    • Type II: the inner cables (nerve fibres) of the nerve are damaged but the outer layer remains intact.
    • Type III: Where the nerve is completely divided. Here both the outer layer and inner cables (nerve fibres) are divided. This type of injury requires the nerve to be repaired to get recovery.

    What happens in a nerve injury?

    When the inner cables (nerve fibres) are damaged the part of the cable that is beyond the level of the injury dies leaving an empty tube. The inner cable above the level of the injury remains alive as it is nourished by the nerve cells close to or within the spinal cord. For the nerve to recover the inner cables (nerve fibres) have to grow back down the tubes.

    What are the clinical presentations of nerve injury?

    • Loss or alteration of sensation.
    • Loss of muscle power which may result in weakness of grip or a feeling of clumsiness.
    • There may be dryness of the skin due to loss of normal sweating.
    • Pain with variable intensity.
    • A lot of individuals notice sensitivity to the cold. Less often gentle touching or stroking of the skin in the affected area may produce an unpleasant feeling.

    What are the signs of a nerve injury?

    • Sensation testing will demonstrate varying degrees of loss of feeling.
    • Testing individual muscles will show weakness.
    • Thinning of the pulps of the fingers, loss of the skin creases at joints, visible muscles wasting.

    What investigation can help in nerve injury?

    Nerve injury is evaluated with neurophysiological testing. In NCV where the nerves are stimulated with an electric current and the speed at which the nerve conducts is measured. In EMG very fine needles may be inserted into an affected muscle and recordings made of the activity in that muscle. This information can help to decide what level of damage there has been to the nerve

    What are the possible treatment options?

    If there are signs of a nerve injury with open wound, then a definite surgical indication to look for nerve and if there it has been partly or completely cut, need to be repair with micro sutures.

    If there is no wound then “wait & see” policy will be considered. During this period further investigations may be carried out to assess nerve injury. This is evaluated with neurophysiological testing (NCV, EMG), which can help in planning further treatment and giving information on the potential outcome of the injury.

    What are the complications of a nerve injury?

    Where the nerve is injured and the nerve fibres are damaged, the damaged fibres can’t find their way down the empty tubes will sprout out and form a bundle of unconnected nerve ends which is called a neuroma. This neuroma can produce a lot of unpleasant sensations if it is knocked or tapped.

    Sometimes a nerve is badly damaged over a long length, in this situation it may be necessary to repair the nerve by putting in nerve grafts, and this will leave a small loss of sensation in the skin, where the nerve graft is taken from.

    What is the outcome after nerve repair?

    The result of a nerve injury depends on many variables so recovery is also variable. Unfortunately nerves recovery is slow as we grow older. This is partly due to the ability of younger nervous system to adapt to loss of normal function in a nerve. The important thing to remember is that nerves take many months to regrows, it grows at the rate of about 1mm per day.

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