Nerve damage explained - Nerves are like the underground tube network in our body

By Marco Sinisi, consultant neurosurgeon, at The Wellington Hospital’s Peripheral Nerve Injury Unit

Nerves are cables to the muscles. They bring electricity to the muscles and enable them to move and bring feeling from our skin. Nerves are like the underground tube network in our body, everything is connected to nerves and impulses travel to the peripheral nerves and brain in order to function. If the tubes are cut, they will stop sending signals and we lose feeling or movement, just as disrupted signals cause delays on the tube. 

Sometimes, particularly in partial nerve damage, pain can be present. This is different to any other kind of pain we experience and is very distinct. You might feel a burning or tingling sensation or feel electrical pulses in the damaged area.

There are two nervous systems the peripheral and central system. The central system includes the brain and spinal cord. The peripheral system includes all the nerves that connect the central system to the muscles and organs around the body.

There are different severities of peripheral nerve damage and general symptoms can include:

• gradual numbness or a tingling feeling.
• sharp freezing or burnings pains.
• loss of movement.
• extreme sensitivity of touch.

But there are three distinct degrees of peripheral nerve damage which require different treatments.

First degree nerve damage - conduction block

This is the mildest form of nerve damage. It is caused when a nerve is compressed or stretched but remains alive. Nerves need oxygen to function and if the blood supply to them is stopped they cannot work. This will result in paralysis and lack of feeling. It can happen for example when a nerve is squeezed between two bones and the oxygen is cut off. This degree of nerve damage will usually fully recover once the nerve becomes uncompressed and there is no requirement for surgical treatment to the nerve. It does recover in minutes/hours from when the compression is removed.

Second degree nerve damage - prolonged conduction block

Second degree nerve damage is where a conduction block takes place but the force applied to the nerve is much bigger than in first degree nerve damage.

The nerve is not broken but there is a change in the insulation. This type of injury could be seen as a result from a birth-related injury, such as brachial plexus, or in association with bone fractures, closed stretching injuries. It can take up to six months to repair but should make a full recovery providing the cause of the blockage is able to be removed. At times surgery is required.

Third degree nerve damage- axonotmesis and neurotmesis

Axonotmesis means that the fibres which constitute the nerve (axons) are damaged but the nerve outside is still present. This provides the necessary “tube” for the nerve fibres to grow back towards their targets at a rate of 1 mm/day. At times the compression which is stopping the nerve to grow back needs to be removed surgically. In this scenario full recovery is still possible. 

Neurotmesis instead is the most severe type of damage and is when a nerve is completely lacerated or so badly ruptured that recovery cannot occur at all unless the nerve is repaired. Neurotmesis is most commonly caused by a serious injury with forceful impact and, in a lot of instances, a laceration that cuts through the nerve. 

Whenever there is either an axonotmesis or a neurotmesis there is a Tinel sign. This means that tapping on the point of the broken nerve, the patient will feel “electricity” going towards the skin normally supplied by the affected nerve. With a bit of imagination it can feel like touching an exposed wire. 

The difference between the Tinel sign in axonotmesis and neurotmesis is that in the first case, as the nerve grows back the Tinel sign will progressively migrate towards the periphery (hands, feet for example), whilst in the neurotmesis it will remain stationary where the damage occurred in the first place.

The faster it can be surgically treated the higher the chance of recovery. Surgery consists of nerve grafting, using a donor nerve to restore a “tube” for the nerve to grow or at times even nerve transfers, moving a working nerve and attaching it to a broken nerve to repair it. If surgery is successful, the nerve will grow back at a rate of 1mm a day. The functional recovery process, when possible, is slow and can take months or years.

To book an appointment with Mr Marco Sinisi at The Wellington Hospital’s Peripheral Nerve Injury Unit call 0207 483 5232.