A peripheral nerve injury (one that occurs in an area away from the brain and spinal cord) could be sustained from a blunt force, fracture, crushing injury, or cut. The most frequently injured nerve areas are the upper limbs.
When you suffer from an injury to your nerves, the healing needed can be quite extensive, especially in cases of neurotmesis (this can take months or even years to recover from). However, this will depend on the extent of the damage caused and what the injury is like.
To provide you with a better understanding of neurotmesis, its signs, and how it can be treated, we’ll explore the nerve structure before comparing it to other nerve injuries. Finally, we’ll explain how these types of injuries can be treated.
Peripheral Nerve Histology
Axons and Schwann cells create the peripheral nerve, with these either being covered in a layer of myelin (myelinated) or not (unmyelinated). This myelin sheath provides the nerves with insulation and enhances their function, but it isn’t always present.
If a nerve is myelinated, the Schwann cells create a sheath that covers each axon, whereas nerves that are unmyelinated consist of groups of Schwann cell-sheathed axons. When an axon has a sheath of Schwann cells, it also has an endoneurium layer (this is a layer of connective tissue).
Where there are several endoneurial tubes, a nerve bundle (also known as a nerve fascicle) is created. In turn, each of these bundles are covered in yet another layer (the perineurium layer) with the epineurium layer covering several of these fascicles.
The epineurium makes up the outer layer of connective tissue that surrounds the peripheral nerve and normally surrounds a number of nerve bundles and blood vessels. Some of these blood vessels also supply the perineurium.
What’s the significance of all of these layers?
Because in neurotmesis, all of these layers and the nerve itself are severed, which completely divides the nerve. This can result in complete paralysis.
Neurotmesis vs. Axonotmesis and Neuropraxia
To classify a nerve injury, a physician will often refer to the Seddon and Sunderland classification system. This places the nerve injuries one may sustain into a number of different degrees – these are neurotmesis, axonotmesis, and neuropraxia, with neurotmesis being the most severe.
Neurotmesis is the severest nerve injury because the axons and sheath are completely divided. This also means a spontaneous recovery does not occur after this type of injury. Surgical repair of a nerve is possible but complete recovery is not because of the degenerative effect the injury causes. Nevertheless, the sooner surgery can be performed, the better.
In contrast, neuropraxia is the least severe type of nerve injury, this is because the fibers of the nerve remain intact (the axon and sheath). Cases of neuropraxia tend to occur when the nerves are stretched (i.e., because of a dislocation or fracture) or after a blunt injury or extended pressure to the nerve. This causes some of the electrical signals that travel through the nerves to become blocked. Spontaneous recovery is possible with this type of nerve injury, and this can even occur within several hours of the injury – or it may take some months.
A medium-level nerve injury is axonotmesis where severe damage is caused to the axons of the nerve, but the layers that surround it remain intact. Axonotmesis is often the result of a severe crush or contusion and if this force is removed from the nerve rapidly, it allows prompt regeneration of the axon. Therefore, full recovery is possible from this nerve injury, but it can take months or years.
The Symptoms and Treatment of Neurotmesis
If you’re suffering from neurotmesis you may experience pain in the injured area, uncomfortable sensations (dysesthesias) and loss of motor and/or sensory function in the nerve that has been affected. You should visit your doctor as soon as you start displaying any of these symptoms or sustain an injury.
To diagnose neurotmesis, your doctor will need to carry out a number of tests as it’s often difficult to distinguish between the different forms of nerve injuries (particularly neurotmesis vs. axonotmesis).
The only way for your doctor to know whether or not it is neurotmesis is to allow for nerve regeneration to occur. If, after some of this has taken place, there is still significant degeneration and muscle paralysis, this indicates a neurotmesis injury. Various clinical evaluations, physical examinations, and tests will be conducted at your local hospital, too.
Treatment may require surgery. But in the first instance, your doctor will try to control any pain you are experiencing. They may also try splinting the injured area to protect it and enhance its function.
Unfortunately, as we’ve already seen, when someone has neurotmesis, they do often get a poor prognosis. It’s highly likely full functionality will never be regained in the nerve – however, surgical techniques often help you regain some function.