| Nerve injury includes total and partial transection of the nerve from cutting and shearing as well as crushing injuries.
Nerve injury may complicate accidents, altercations, or other acute trauma, or it may develop more slowly from gradual compression caused by repetitive movements, as in carpal tunnel syndrome, or by sustained positions, as in radial nerve palsy. It may occur during or after surgery because of traction or casting putting pressure on a nerve or because of incidental injury to a nerve located in the operative field.
There are five grades of nerve injury classified by the degree of pathological change in the nerve. The mildest injury is classified as grade I and the most severe as grade V. Grade I nerve injury is called neurapraxia and is a minor injury from which full recovery occurs. Type II, called axonotmesis, is a more severe injury, and although some secondary reparative processes occur, recovery eventually takes place. A situation in which the nerve is severely damaged by crushing or complete transection is called neurotmesis and is classified as grades III, IV, or V, all of which result in some degree of permanent impairment. If a motor nerve is injured, the muscle(s) that the nerve supplies loses function. If a sensory nerve is injured, the area supplied (innervated) by the nerve loses sensation. The closer the nerve is to its origin in the spinal cord, the lower the chance of recovery.Risk: There are no sexual or racial predilections for nerve injuries. Certain occupations may predispose individuals to nerve injuries, as can some sports activities. Incidence and Prevalence: Because nerves are usually injured along with other structures, there are no good incidence figures for nerve injuries themselves. |
Source: Medical Disability Advisor
| History: The individual may complain of pain, reduced sensation (hypoesthesia), or weakness of an extremity after trauma. Sometimes, no specific trauma is revealed. Physical exam: General physical examination may reveal associated injuries. A standard neurologic exam may show some of the degree of involvement, with confirmation of the complaints noted above. Peripheral nerve testing should include tests of light touch, pain, temperature, and vibration sensation. Other sensory tests include the ability to distinguish two pinpricks applied closely together (two-point discrimination) and the ability to appreciate small movements of the joint (joint position sense). Motor testing includes tests of strength of muscles supplied by the affected nerve. In nerve injuries related to entrapment or compression, lightly tapping over the nerve where it is compressed may cause a painful or tingling sensation. In carpal tunnel syndrome, for example, tapping over the median nerve at the wrist elicits pain in the fingers (Tinel's sign). Reflexes are typically depressed or absent in affected muscle groups. Tests: Electromyogram (EMG) helps differentiate between grade I and higher grades of injury (II to V). A nerve conduction study, done by stimulating the nerve using an electrical stimulus on the skin and measuring the nerve response, indicates which motor and sensory nerves are affected. These tests become abnormal 2 to 3 weeks after the injury. A single test cannot distinguish between the lesions that will demonstrate eventual recovery (II, III) and those that are less likely (IV, V), but repeated tests can show whether improvement is occurring over time. Somatosensory evoked potentials are abnormal immediately after nerve injury, making this a useful test for monitoring nerve function during surgery that might compromise the nerve.
The skin surrounding the nerve may be examined using a magnifying lens or light scope (ophthalmoscope) to examine for patterns of sweating. This test, called a "sweat test," can indicate if the nerve fibers controlling sweating and blood vessel dilation (parasympathetic nerves) are affected. |
Source: Medical Disability Advisor
| The timing of treatment of open wound nerve injuries is critical. The wound is explored, and if a clean cut of the nerve is found, the proximal and distal nerve ends are matched and brought together so that microneurosurgical repair (neurorrhaphy) can be carried out.
The repair may be done at a later date; the timing of nerve repair is dictated by the nature of the nerve injury and may be performed after the wound has healed, when some of the swelling and scarring has resolved. Delayed repairs usually require nerve grafting using a piece of another nerve to connect across the injured area.
In a closed injury (crush or shear), there is no indication for immediate surgery. The degree of nerve injury should be diagnosed as soon as possible. The individual is periodically examined over a 3-month period. During this period, gentle active motion of the involved extremity keeps the joints and soft tissue supple. If by 3 months there is some clinical or electrical evidence of recovery, the individual continues to be monitored. However, if there is no clinical or electrical (EMG) evidence of return of function at 3 months, the nerve is explored and tested. If the test indicates any activity across the injury, then corrective nerve surgery is performed. If there is no activity, the injured area is cut out (excised) and grafted. |
Source: Medical Disability Advisor
| With grade I and II injuries, full recovery will eventually occur. With grade III, scarring will result in a less than perfect reinnervation with an extremely variable pattern. There is no recovery from grade IV and V nerve injuries. The outcome also depends on the location and territory supplied by the injured nerve and on whether there is overlap in function with neighboring nerves that are not injured. In some cases, these nerves may be able to take over some functions of the injured nerves. |
Source: Medical Disability Advisor
| Following nerve injury, physical therapy may be indicated to promote gradual recovery of muscle strength through strengthening exercises and to prevent contractures or stiffening of injured areas. Occupational therapy may help the individual regain independence in activities of daily living and may assist in selection and use of appropriate assistive equipment. Vocational rehabilitation may help determine specific work restrictions and assist the individual in retraining for another job or returning to work with modifications. |
Source: Medical Disability Advisor
| Open wounds may be complicated by wound infection and systemic infection (sepsis). Contractures of joints around the affected nerve may complicate motor nerve injury. Loss of sensation may lead to accidental burns or other injuries. Scarring may occur in and around the injured nerve, resulting in the formation of a neuroma. |
Source: Medical Disability Advisor
| The extent of injury, associated motor and sensory disability, and type of work will dictate the type of work restrictions or accommodations necessary. |
Source: Medical Disability Advisor
| If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case. Regarding diagnosis:
- Does individual have a history of trauma, surgery, or repetitive task-type injury to the affected area?
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Does individual have complaints of pain, lack of sensation, increased sensitivity, or unpleasant sensation to the affected area?
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Did the diagnostic workup include a neuro-sensory exam of the affected area?
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Has the nerve injury been identified and quantified using an electromyelogram and/or nerve conduction study?
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Were additional diagnostic studies, such as MRI, done to rule out blood clot, foreign body, or other mass that could be interfering with nerve function and repair?
Regarding treatment:
- Has surgical repair been considered? Should it be immediate or delayed?
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Are associated injuries and underlying conditions being treated appropriately?
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Might individual benefit from second opinion consultation to consider management strategies? Has individual been receiving physical and occupational therapy?
Regarding prognosis:
- Was there a prolonged time between the initial injury and the surgical repair?
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Did individual suffer any complications such as wound infection following surgery that could impact recovery and prognosis?
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Has individual suffered associated muscle wasting or muscle contracture that could impact recovery and prognosis?
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Source: Medical Disability Advisor
| Rochkind, S., and M. Alon. "Microsurgical Management of Old Injuries of the Peripheral Nerve and Brachial Plexus." Journal of Reconstructive Microsurgery 16 7 (2000): 541. |
Source: Medical Disability Advisor
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