Correspondence

Case 11-1997: Critical-Illness Myopathy

N Engl J Med 1997; 337:862-863September 18, 1997

Article

To the Editor:

In discussing Case 11-1997 (April 10 issue),1 Sandrock directs attention to a “critical-illness myopathy associated with myosin deficiency.” This diagnosis is clearly based on, in addition to pathological muscle findings, the electrophysiologic studies performed on the 34th and 78th hospital days. However, the reported results of nerve-conduction studies, which included F-wave recordings, point to contemporaneous peripheral-nerve involvement. At the first examination in particular, median, ulnar, and tibial F waves were absent; at the second examination, the median F wave was still absent, the compound muscle responses were further prolonged, and the recovery in the amplitude of the compound muscles was slight and actually absent in one nerve. Indeed, the involvement of the peripheral nervous system is suggested mainly by the absence of sensory-nerve (ulnar and sural) action potentials and by the significant reduction in amplitude (from 12.4 to 5.4 μV in the median nerve) recorded in the second study. No clinical data in keeping with these findings are reported. Our opinion is that the patient had a critical-illness neuromyopathy, even if there was prominent muscle damage. The coexistence of a mild neuropathic process has been previously described in such patients 2-5 and probably results from a variety of causes. As stated,1 muscle denervation could facilitate a particularly severe form of corticosteroid-induced myopathy.

Alberto Primavera, M.D.
Michele Abbruzzese, M.D.
University of Genoa, 16132, Genoa, Italy

5 References

1. 1

   Case Records of the Massachusetts General Hospital (Case 11-1997). N Engl J Med 1997;336:1079-1088
   Full Text | Web of Science | Medline

2. 2

   Op de Coul AA, Lambregts PC, Koeman J, van Puyenbroek MJ, Ter Laak HJ, Gabreels-Festen AA. Neuromuscular complications in patients given Pavulon (pancuronium bromide) during artificial ventilation. Clin Neurol Neurosurg 1985;87:17-22
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   Hirano M, Ott BR, Raps EC, et al. Acute quadriplegic myopathy: a complication of treatment with steroids, nondepolarizing blocking agents, or both. Neurology 1992;42:2082-2087
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   Lacomis D, Smith TW, Chad DA. Acute myopathy and neuropathy in status asthmaticus: case report and literature review. Muscle Nerve 1993;16:84-90
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   Faragher MW, Day BJ, Dennett X. Critical care myopathy: an electrophysiological and histological study. Muscle Nerve 1996;19:516-518
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Author/Editor Response

Dr. Sandrock replies:

To the Editor: Primavera and Abbruzzese raise the important issue of coexisting disease in severely weak, critically ill patients. We, too, have frequently observed features of both neuropathy and myopathy in the same patient. In Case 11-1997, however, the possibility of a neuropathic contribution to the primary illness was dismissed because when the electrophysiologic studies were performed on the 34th hospital day, the amplitudes of the sensory-nerve action potentials were normal; motor- and sensory-nerve conduction velocities were normal; there was no definite evidence of conduction block; and there was no spontaneous electromyographic activity. As Primavera and Abbruzzese point out, the same study also showed that the F waves were absent, a common finding in neuropathies, especially those affecting proximal-nerve segments, plexuses, or roots. However, when the amplitudes of compound muscle action potentials are markedly reduced, the lack of persistence of F waves or their absence is difficult to interpret and cannot establish the diagnosis of neuropathy. In fact, the muscle biopsy did not show evidence of neurogenic changes. Thus, all the clinical, electrophysiologic, and pathologic features of acute illness can be explained entirely by the myosin-deficient myopathy.

By the 78th hospital day, however, I agree that there were electrophysiologic features of both nerve and muscle disease. As they point out, the amplitudes of the sensory-nerve action potentials were reduced; some were even unrecordable. Moreover, the electromyogram appears to have demonstrated two groups of motor units: some that were neuropathic and some that were myopathic. Thus, at some time during the second and third month of hospitalization, a neuropathic component seems to have intervened. However, although the neuropathy may have complicated the patient's recovery, I do not believe it contributed substantially to the initial weakness.

Perhaps it should not be surprising that more than one cause of weakness is often discovered in critically ill patients at some time during their often protracted hospitalizations. Such patients may be exposed to a multitude of “risk factors” for neuromuscular disease during their illness, including prolonged inactivity, treatment with muscle relaxants, corticosteroid therapy, sepsis, or a combination of these. Thus, it is probable that most critically ill patients have some degree of critical-illness polyneuropathy as well as critical-illness myopathy.

Alfred Sandrock, M.D., Ph.D.
Massachusetts General Hospital, Charlestown, MA 02129

Citing Articles (1)

Citing Articles

1. 1

   Howard W. Sander, Marianna Golden, Moris J. Danon. (2002) Quadriplegic areflexic ICU illness: Selective thick filament loss and normal nerve histology. Muscle & Nerve 26:4, 499-505
   CrossRef