Peripheral Nerve Entrapment Impairments Revisited: Part I

The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Sixth Edition, introduced the concept of diagnosis-based impairments (DBI), and a modified version of this method can be used in rating peripheral nerve injury in general (Section 5.4) and upper limb entrapment syndromes (Section 15.4f). The first portion of this article reviews the evaluation of upper extremity nerve impairment and summarizes inclusion criteria and causation correlation for carpal tunnel syndrome, Guyon's canal syndrome, cubital tunnel syndrome, anterior interosseous, Wartenberg's syndrome, and radial tunnel syndrome. Very mild nerve entrapments do exist and may fail to meet the AMA Guides criteria for impairment related to a diagnosis of nerve entrapment. Electrodiagnostic examination includes nerve conduction studies that assess the largest, most heavily myelinated axons, and needle electromyelography, which detects muscle membrane instability but not the sensory function of nerves. A case example from the AMA Guides, Sixth Edition, shows the process of permanent impairment rating in a case of carpal tunnel syndrome. Determination of impairment for peripheral nerve entrapments can be easily accomplished once one understands how to determine if the nerve under consideration from the electrodiagnostic evaluation demonstrates a conduction delay, a conduction block, or an axon loss. This establishes the test findings that usually are the only objective findings present.