AMA Guides® Newsletter - Issue Archive

Articles

1. Rating Upper Extremity Entrapment Neuropathies

   James B. Talmage

   Pages 1–3

   DOI: 10.1001/amaguidesnewsletters.2000.MarApr01

   Abstract

   Upper extremity entrapment neuropathies are chronic injuries to peripheral nerves, presumably from sustained pressure on the nerve in question. These conditions are controversial, and physicians disagree, unfortunately too often, about whether a neuropathy is present, what caused the neuropathy, and what the proper impairment rating should be. Carpal tunnel syndrome is the most common entrapment or “pressure neuropathy” and must be differentiated from other causes of nerve dysfunction such as viral illness, toxins (eg, heavy metals), and systemic diseases such as diabetes or vasculitis. Each of the upper extremity nerves has many potential sites of entrapment, which most frequently occurs secondary to a congenital anomaly such as anomalous fibrous band, muscle bellies, or arteries. Ganglion cysts, lipomas, tumors, and fracture callus or nonunion also have been reported as a cause of these rare neuropathies. Diagnosis of entrapment is challenging because entrapments are uncommon to rare, but arm pain is common in individuals who move their arms repetitively at work, avocation, or sport, and establishing causation also is controversial. Severe entrapment essentially is total destruction of the nerve involved, but, in a lifetime of practice, most physicians will not see a nerve entrapment that progresses to complete loss of all motor and sensory function.
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2. Questions and Answers

   Christopher R. Brigham, James B. Talmage

   Pages 3–3

   DOI: 10.1001/amaguidesnewsletters.2000.MarApr02

   Abstract

   Lesions of the peripheral nervous system (PNS), whether due to injury or illness, commonly result in residual symptoms and signs and, hence, permanent impairment. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) describes procedures for rating upper extremity neural deficits in Chapter 3, The Musculoskeletal System, section 3.1k; Chapter 4, The Nervous System, section 4.4 provides additional information and an example. The AMA Guides also divides PNS deficits into sensory and motor and includes pain within the former. The impairment estimates take into account typical manifestations such as limited motion, atrophy, and reflex, trophic, and vasomotor deficits. Lesions of the peripheral nervous system may result in diminished sensation (anesthesia or hypesthesia), abnormal sensation (dysesthesia or paresthesia), or increased sensation (hyperesthesia). Lesions of motor nerves can result in weakness or paralysis of the muscles innervated. Spinal nerve deficits are identified by sensory loss or pain in the dermatome or weakness in the myotome supplied. The steps in estimating brachial plexus impairment are similar to those for spinal and peripheral nerves. Evaluators should take care not to rate the same impairment twice, eg, rating weakness resulting from a peripheral nerve injury and the joss of joint motion due to that weakness.
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3. Quick Reference: Chapter 3: The Musculoskeletal System

   Pages 4–5

   DOI: 10.1001/amaguidesnewsletters.2000.MarApr03

   Abstract

   The November/December 1996 issue of The Guides Newsletter included an article regarding the challenges faced by those who evaluate carpal tunnel syndrome (CTS) impairment. A recent case highlights some of these challenges: Ms Kirby presented for an independent medical evaluation to address two issues, the work-relatedness of her left CTS and the percentage of anatomic impairment due to her surgically treated left CTS. Relevant clinical records noted nonspecific complaints of left-hand pain and paresthesia but no abnormalities of the peripheral neuromusculoskeletal system. Motor nerve conduction velocities were normal and showed relative prolonged latencies in the left vs right median nerve at the wrist. Left carpal tunnel release surgery was recommended and performed, but Ms Kirby reported no improvement in her symptoms and had a self-perception of substantial occupational incapacity. The evaluating physician determined that Ms Kirby had neither the specific hand/wrist symptoms nor the median nerve slowing necessary to establish a diagnosis of CTS and, therefore, could not have work-related CTS according to the criteria in the AMA Guides to the Evaluation of Permanent Impairment, Fourth Edition. The parties involved could not reach a settlement, and the case went to trial; the trial court relied on the testimony of the treating surgeon in finding that Ms Kirby's CTS was caused by her work and awarded her a substantial percentage of occupational disability.
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4. Impairment Tutorial: Rating Sensory and Motor Deficits of the Upper Extremity

   Charles N. Brooks

   Pages 5–7

   DOI: 10.1001/amaguidesnewsletters.2000.MarApr04

   Abstract

   The three components of electrodiagnosis useful in evaluation of the peripheral nervous system and spinal cord include electromyography (EMG), electroneurography (nerve conduction studies), and somatosensory evoked potentials. EMG examination involves introduction of a special recording needle into a muscle belly. Electrical potentials located within a few millimeters of the needle are picked up by an electrode and are transmitted from the muscle to amplifiers that filter and display results visually for the electromyographer. Three types of spontaneous activity in electrical potentials are of the greatest relevance: positive sharp waves, fibrillation potentials, and fasciculations (fasciculation potentials on the EMG result from irregular firing of motor units). Electromyography can help assess the status of nerve fibers indirectly, but the integrity of large myelinated sensory and motor neurons can be evaluated directly by nerve conduction studies (NCS), also known as electroneurography. NCS can assess motor neurons, sensory neurons, or mixed nerve trunks. Sensory nerve conduction velocity can be studied in a manner analogous to motor conduction velocity: sensory fibers can be directly stimulated, and the evoked response can be measured at the wrist and elbow. Somatosensory evoked potentials occasionally are useful as an adjunct to EMG and NCS in the diagnosis of peripheral nervous system pathology. These tests also are useful when it is unclear whether an individual has a true radiculopathy.
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5. Case Study: The Continuing Challenge of Evaluating Carpal Tunnel Syndrome Impairment

   Leon H. Ensalada

   Pages 8–8, 11

   DOI: 10.1001/amaguidesnewsletters.2000.MarApr05

6. Clinical Update: Electrophysiologic Studies

   Richard T. Katz

   Pages 9–11

   DOI: 10.1001/amaguidesnewsletters.2000.MarApr06