8025 - Myasthenia gravis
DBQ: Link to Index of DBQ/Exams by Disability for DC 8025
Acronym: MG
Definition
Myasthenia gravis is an autoimmune neuromuscular transmission disease marked by episodes of muscle weakness, primarily in muscles innervated by cranial nerves.
Etiology
The condition is caused by an autoimmune attack (the body's response to a portion of itself when it does not recognize the portion as part of itself) on the neuromuscular junction, jeopardizing normal neuromuscular transmissions. The exact cause of the autoimmune attack is unknown. The onset is usually insidious. The condition may be detected by a coincidental infection that leads to exacerbation of symptoms. The condition may occur in association with other diseases such as thyrotoxicosis, rheumatoid arthritis (see Diagnostic Code: 5002 Arthritis, rheumatiod) or lupus erythematosus (see Diagnostic Code: 7809 Discoid lupus erythematosus or subacute cutaneous lupus erythematosus).
Signs & Symptoms
Signs and symptoms may fluctuate in intensity during the day, and over the course of hours to days. Signs and symptoms may include: fluctuating weakness of commonly used voluntary muscles, resulting in ptosis; diplopia; difficulty in chewing; dysphagia; dysarthria; respiratory difficulties; limb weakness, or some combination of the aforementioned signs and symptoms. There is usually an increase in weakness of affected muscles due to activity. There may also be alterations in the voice; nasal regurgitation; and choking. A myasthenic crisis with life-threatening respiratory muscle involvement may develop. The condition may follow a slowly progressive course, and may have a fatal outcome due to respiratory complications.
Tests
Myasthenia gravis is confirmed by improvement in the strength of weak muscles, with a short-acting anticholinesterase drug. Tests may include: electrophysiologic tests with needle electromyography (EMG); neuromuscular transmission studies; and computed tomography (CT) scan of the chest as well as specific blood tests.
Treatment
Treatment may include anticholinesterase medications, which briefly improve muscle weakness. Corticosteroid, immunosuppressive medications may be given to alter the disease course, and a thymectomy may be done. Respiratory support from a mechanical ventilator may be required.
Residuals
Residuals may include side effects of medications, which must be monitored carefully. Residuals may include respiratory paresis, which may require respiratory support by a mechanical ventilator. There may be long-term, spontaneous relapses and remissions that may last for weeks to months. Residuals will vary from individual to individual, and may include any or all of the signs and symptoms to include complete disability.
Special Considerations
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This disease shall be granted service connection although not otherwise established as incurred in or aggravated by service if manifested to a compensable degree within the applicable time limits under 38 CFR 3.307 following service in a period of war or following peacetime service on or after January 1, 1947, provided the rebuttable presumption provisions of 38 CFR 3.307 are also satisfied [38 CFR 38 CFR 3.309 . [Disease subject to presumptive service connection], 38 CFR 3.309 (a) [chronic disease].
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In those cases where there is severe neurologic deficit, consider entitlement under 38 CFR 3.350 [Special monthly compensation ratings]; competency under 38 CFR 3.353 [Determinations of incompentency and competency], and ancillary benefits under 38 CFR 3.807,38 CFR 3.808 [Automobiles or other conveyances; certification], 38 CFR 3.809 [Specially adapted housing under 38 U.S.C. 2101(a)], and 38 CFR 3.809a [Special home adaptation grants under 38 U.S.C. 2101(b)].
Notes
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It is required for the minimum ratings for residuals under diagnostic codes 8000-8025, that there be ascertainable residuals. Determinations as to the presence of residuals not capable of objective verification, i.e., headaches, dizziness, fatigability, must be approached on the basis of the diagnosis recorded; subjective residuals will be accepted when consistent with the disease and not more likely attributable to other disease or no disease. It is of exceptional importance that when ratings in excess of the prescribed minimum ratings are assigned, the diagnostic codes utilized as bases of evaluation be cited, in addition to the codes identifying the diagnoses.
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Disability in this field is ordinarily to be rated in proportion to the impairment of motor, sensory or mental function. Consider especially psychotic manifestations, complete or partial loss of use of one or more extremities, speech disturbances, impairment of vision, disturbances of gait, tremors, visceral manifestations, injury to the skull, etc. In rating disability from the conditions in the preceding sentence refer to the appropriate schedule. In rating peripheral nerve injuries and their residuals, attention should be given to the site and character of the injury, the relative impairment in motor function, trophic changes, or sensory disturbances. 38 CFR 4.120
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With the exceptions noted, disability from the following diseases and their residuals may be rated from 10 percent to 100 percent in proportion to the impairment of motor, sensory, or mental function. Consider especially psychotic manifestations, complete or partial loss of use of one or more extremities, speech disturbances, impairment of vision, disturbances of gait, tremors, visceral manifestations, etc., referring to the appropriate bodily system of the schedule. With partial loss of use of one or more extremities from neurological lesions, rate by comparison with the mild, moderate, severe, or complete paralysis of peripheral nerves” 38 CFR 4.124a