Axonotmesis

Axonotmesis is nerve injury where severe disruption of axons and surrounding endoneurial sheaths takes place. Axonotmesis is characterized by axonal injury with subsequent degeneration or regeneration. The result of an Axonotmesis injury is motor, sensory and autonomic paralysis. In Axonotmesis, if the force creating nerve damage is removed in timely manner, then the axon may regenerate leading to recovery from this nerve injury. Axonotmesis is a more severe nerve injury with disruption of the neuronal axon. But in axonotmesis, the Schwann sheath is maintained. Seddon classified the nerve injury based on the extent of damage to the nerves following 'pathotofical types' on the basis of structural changes in cut nerves. The Seddon classification divides nerve injuries into three types:

Axonotmesis: Microscopic division of nerve fibers without obvious discontinuity of nerve sheath.

Neurotmesis: Complete anatomic division of the nerve fibers with obvious discontinuity of the nerve sheath.

Neuropraxia: There in injury without any anatomical discontinuity but resulting in functional disruption or nerve concussion. It is a local transient conduction blockage along the nerve.

Axonotmesis as a birth injury

As a birth injury, axonotmesis is often extremely frightening. With present day advances in the medical delivery process, there are many precautions that can be taken to lower risk for nerve injury like axonotmesis at birth. However, it must be borne in mind that not all birth related injuries are preventable. Symptoms of axonotmesis include motor and sensory loss due to blockage of conduction by demyelination. There is loss of reflex due to damage to sensory nerves. Atrophy may follow. In addition to general examination, tests may be conducted for systemic diseases such as glucose, kidney functions. A nerve conduction test is done to determine the extent of the injury. Nerve conduction test determines the speed and the amplitude of the signal transmitted by nerve cells which can reveal the extent of the nerve injury - nerve cells or the protective myelin sheath. Electromyography is another diagnostic test used in axonotmesis.

In axonotmesis a complete absence of sensory modalities takes place. However, the investing sheaths of the nerve remain intact. Therefore unlike neurotmesis, recovery though delayed is likely to take place. If damage to the nerve cells has also caused destruction of the axons, there can be recovery if the supporting structures of the cells are intact. But complete recovery may not be possible. Recovery from axonotmesis can take many months. Depending upon the severity of Axonotmesis injury, full recovery can even take up an entire year. The recovery largely relies upon removal of the compressing force, timely intervention and the ability of the axon to regenerate.

Neurotmesis

Neurotmesis refers to most serious and severe nerve injury. Neurotmesis is brachial plexus injury. These brachial plexus injuries can occur in live births. The type of injury to the brachial plexus and the stretch damage will determine where the injury takes place. Various types of injuries can occur once the nerve rootlets form mixed nerve root. In some instances, the extent of the nerve damage may not be fully apparent but complete loss of motor, sensory and autonomic functions occurs. This type of complete rupture of the brachial plexus is called neurotmesis. Neurotmesis is part of Seddon's classification scheme used to classify nerve damage. Seddon classified the nerve injury based on the extent of damage to the nerves following pathotofical types on the basis of structural changes in cut nerves. The Seddon classification divides nerve injuries into three types namely:

Neurotmesis: Complete anatomic division of the nerve fibers with obvious discontinuity of the nerve sheath.

Axonotmesis: Microscopic division of nerve fibers without obvious discontinuity of nerve sheath.

Neuropraxia: There is injury without any anatomical discontinuity but resulting in functional disruption or nerve concussion. This is short term or sometimes lasts months with severe compression.

Common symptoms of neurotmesis include loss of sensation and change in taste, expression and speech. There might be emotional and psychological disturbances. In the final stages, there could be a complete loss of motor, sensory and autonomic functions. Special tests for assessment of neurotmesis include electromyography, Strength duration curve, nerve conduction study and thermography. Recovery from trauma is dependent on the age of the patient, type of injury and degree of injury. Without surgical intervention and repair this injury has very poor prognosis. Even with surgical repair, there could be significant loss of motor and sensory neurons which are responsible for normal conduction.

Smiths fracture

In the US, about 17% of the emergency room visits are due to wrist injuries. Injury of the forearm bone near the wrist joint is known as Smith's fracture. Smith's fracture is a fracture of the distal radius occurring about 2.5 cm from the wrist joint. The fracture is the result from a backward fall onto the outstretched hand. It was the orthopedic surgeon Robert William Smith who described this fracture in his book 'A treatise on fractures in the vicinity of joints, and on certain forms of accidents and congenital dislocations' published in 1847. This fracture is named after him. Smith's fracture is often described as a garden-spade deformity.

Hands perform so many tasks that are fundamental and delicate. Therefore even a minor injury to the hand and wrist can have devastating consequences. Smith's fracture is unstable as the ulnar head can be displaced dorsally and therefore requires urgent attention. The hand and the wrist are so dependent on each other. Therefore when an injury occurs, it affects both the hand and wrist. Smith's fracture are classified as:

Type I: Most stable, extra articular transverse distal radial fracture with palmar and proximal displacement.

Type II: Barton type, palmar-lip fracture of the distal radius with dislocation of the carpus
Type III: Unstable, oblique juxta articular fracture of the distal radius and tilted palmar.

• A Smith's fracture is most commonly caused by people falling onto hard surface and breaking their fall with flexed wrists.
  
• Smith's fracture most commonly occurs in older post- menopausal women exhibiting osteoporosis.
  
• Smith's fracture occurs in adolescent boys and girls with joint surface displacement.
  
• Smith's fracture can be considered as a sports injury
  
  Common complications from Smith's fracture:

• Ulnar nerve injury
  
• Carpal tunnel syndrome
  
• Post traumatic radio carpal osteoarthritis with limited range of motion
  
• Heterotopic ossification
  
• Reflex sympathetic dystrophy
  
• Tendon rupture
  
• Nonunion
  
• Radial shortening

Treatment for Smith's fracture depends much upon the severity of the fracture and other factors such as connective tissue injuries, musculoskeletal structure and neuroanatomy, and dislocations involved. If the fracture is an undisplaced fracture, then it can be treated simply with a 'cast' alone. Nevertheless, casting needs close watch so as to ensure that the fracture stays in proper position.