Volume 121 Number 5, Part 1
Electrodiagnosis of botulism To the Editor Graf and colleagues, in their article entitled "Electrodiagnosis Reliability in the Diagnosis of Infant Botulism (J PEDIATR 1992; 120:747-9), suggest that electrodiagnostic techniques are not reliable in the diagnosis of infant botulism. We question that assertion on the basis of our experience with 10 patients with botulism (6 adults, 4 infants). 1, 2 The authors do not clearly define the electrophysiologie measurements used in the evaluation of their patients. They state that 30 Hz nerve stimulation failed to show an incremental response of the compound muscle action potential (CMAP). Whether other criteria were used is uncertain. We concur with the authors that an incremental response of the C M A P to rapid nerve stimulation is not a reliable indicator of botulism. This incremental response was also not present in some of the patients we studied. 1 However, posttetanie facilitation of the C M A P has been present in all our patients. With the patient at rest, one expects to have a small or borderline-small CMAP in response to a single supramaximal nerve stimulus. After a 10-second period of rapid, repetitive nerve stimulation, there is enlargement of this initially small C M A P of at least 40%; it may be several times larger than the initial potential. This enlargement of the C M A P after a brief period of tetanus (posttetanic facilitation) persists for many minutes; this does not occur with other disorders of neuromuscular transmission and is a unique feature of botulism, l, 2 At the same time, the posttetanic facilitation alone is a strong indication that botulism is the diagnosis. This posttetanic facilitation occurs early in the course of the illness and gradually disappears with recovery. We have found this diagnostic procedure to be quick, reliable, and easy, even in the intensive care unit environment, and we believe that posttetanic facilitation of the C M A P is a reliable indicator of botulism.
Ludwig Gutmann, MD John Bodensteiner, MD Alvaro Gutierrez, MD Department of Neurology West Virginia University School of Medicine Morgantown, W V 26506 9/35/40707
REFERENCES 1. Gutmann L, Pratt L. Pathophysiologic aspects of human botulism. Arch Neurol 1976;33:175-9. 2. Fakadej A, Gutmann L. Prolongation of post-tetanic facilitation in infant botulism. Muscle Nerve 1982;5:727-9.
before the technique can be regarded as a reliable indicator of botulism. The pain and discomfort that would accompany needle stimulation for 10 seconds at 50 Hz appear difficult to justify.
William D. Graf MD Ross M. Hayes, MD Paul M. Mendelman, MD Divisions of Congenital Defects, Rehabilitation, and Infectious Disease Children's Hospital and Medical Center Seattle, WA 98105 9/35/40706
Serum valproate concentrations and control of seizures To the Editor: Cloyd et al., 1 in their article about syrup and sprinkle formulations of valproate, seem to assume that slower absorption and diminished peak-to-trough variation are advantageous in terms of the efficacy of the drug and that there is a close and temporally related correlation between serum concentration and antiepileptic effect. It would be difficult to support such an assumption with facts. The authors' quotation of Dr. Aicardi 2 is selective. He writes (p. 332) that "the half-life of the drug is indeed brief and would seem to [my italics] imply repeated administration as there are rapid and marked fluctuations of blood levels . . . . There are suggestions, however, that anticonvulsant effect is maintained even at low blood levels and the use of a single daily dose is advocated by some." The relationship between seizure control and serum concentrations of valproate is more complex than Cloyd et al. suggest and it is by no means proved that steady serum concentrations are desirable.
D. P. Addy, MB, FRCP, DCH Consultant Paediatrieian West Birmingham Health Authority Dudley Road Hospital Birmingham B18 7QH, United Kingdom 9/35/40917
REFERENCES 1. Cloyd JC, Kriel RL, Jones-Saete CM, Ong BY, Janeik JT, Remmel RP. Comparison of sprinkle versus syrup formulations of valproate for bioavailability, tolerance, and preference. J PEDIATR 1992;120:634-8. 2. Aicardi J. Epilepsy in children. New York: Raven Press, 1986.
To the Editor."
To the Editor:
The findings of Dr. Gutmann and colleagues raise an important issue. They found posttetantic facilitation of the compound muscle action potential to be a reliable indicator of botulism in both adults and infants. Although this technique may be useful, their sample size of four patients is small, and further evaluation is necessary
Dr. Addy makes an important point about the significance of peak-to-trough variation in serum valproate concentrations. We agree that some patients can take valproate once daily without loss of seizure control or development of side effects. Many of these patients have received monotherapy with minimal fluctuation of