Neurotmesis (in Greek tmesis signifies "to cut") is a complete transection of a peripheral nerve, and is part of Seddon's classification scheme used to classify nerve damage. It is the most serious nerve injury in the scheme. In this type of injury, both the nerve and the nerve sheath are disrupted. While partial recovery may occur, complete recovery is impossible.
Symptoms
Symptoms of neurotmesis include but are not limited to pain, dysesthesias (uncomfortable sensations), and complete loss of sensory and motor function of the affected nerve. Within 30 minutes after injury, intracellular processes that promote repair and regeneration have already been activated. Schwann cells play an indispensable role in promoting regeneration by producing neurotrophic factors and by increasing their synthesis of surface cell adhesion molecules, and by elaborating basement membrane containing extracellular matrix proteins, such as laminin and fibronectin. In most cases, due to the extreme nature of the injury, there is typically complete loss of function.
Mechanisms
Trauma is the most frequent cause of peripheral nerve lesions. The only way to know for sure if a nerve injury is in fact neurotmesis is to allow for the normal progression of nerve regeneration to take place (nerves regenerate at a rate of approximately 2–4 mm/day proximal to the lesion), and if, after that time, there is still profound muscle paralysis and degeneration in these areas, then it is likely to have been a neurotmesis injury. These injuries are almost always reversed and a recovery takes place within days or weeks. The second classification of the Seddon system is referred to as axonotmesis which is a more severe case of peripheral nerve injury. Axonotmesis is classified by an interruption of the axons, but a preservation of the surrounding connective tissues around the axon. The last and most severe case of peripheral nerve injury is known as neurotmesis, which in most cases cannot be completely recovered from even with surgical repair.
The second classification of nerve injury is known as the Sunderland classification which is more complex and specific. This classification uses five different degrees of nerve injury, the first one being the least severe and the equivalent to neurapraxia and the most severe being the fifth degree and having the same classification as neurotmesis. The second through fourth degrees are dependent on the variance of axon discontinuity and are classified under Seddon's classification of axonotmesis.
Treatment
The first line of treatment is often to treat the patient's pain with neuropathic drugs such as tricyclic antidepressants, Serotonin–norepinephrine reuptake inhibitor, and anticonvulsants. The second lines of drugs to treat pain are non-steroidal anti-inflammatories, tramadol, and opioids. Other techniques used to facilitate healing of the nerve and pain are either static or dynamic splinting that can both help protect the injured part as well as improve function.