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PEDIATRICS Vol. 111 No. 3 March 2003, pp. e197-e202

ELECTRONIC ARTICLE

Stimulus-Induced Drop Episodes in Coffin-Lowry Syndrome^V

Gregg B. Nelson, MD, Jin S. Hahn, MD

From the Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California; and Lucile Packard Children’s Hospital at Stanford, Stanford, California

--> Objective. Coffin-Lowry syndrome (CLS) is a rare disorder characterized by moderate to severe mental retardation, facial dysmorphism, tapering digits, and skeletal deformity. Paroxysmal drop attacks occur in patients with CLS, characterized by sudden loss of muscle tone induced by unexpected tactile or auditory stimuli. Our objective is to characterize these attacks better using neurophysiologic studies.

View larger version (138K): [in this window] [in a new window]   Fig 1. Four frames of video clip showing a typical episode in case 1. In this 16-year-old boy with CLS, an unexpected pull on the shoulders by the examiner leads to a sudden loss of tone with an abrupt drop to the ground. He recovers rapidly, and there is no loss of consciousness (see video clip 1). This brief episode occurs at 00:09 after the start of the clip. The numbers on the bottom left corner of each frame (MM:SS.000) represent the time after the stimulus.

 

View larger version (158K): [in this window] [in a new window]   Fig 2. Four frames of video clip 2 showing a typical startle-like episode to sound in our second patient with CLS at 13 years of age. These episodes were triggered by a loud noise and consisted of sudden arm extension and forward lurching of the body (00:41). If they had occurred while he was standing, then he would have fallen to the ground. At 6 years of age, he had a different type of drop episodes. Video clip 2 associated with this case also demonstrates the earlier drop episodes that were triggered by bumping into the furniture while backing up (00:16) or by a pull on his EEG leads (00:26). The numbers on the bottom left corner of each frame (MM:SS.000) represent the time after the stimulus.

 
Methods. We report 2 teenage boys with CLS and stimulus-induced drop episodes (SIDEs). Simultaneous surface electromyogram (EMG) and video electroencephalogram were performed during SIDEs on our 2 patients.

Results. Both patients had SIDEs stimulated by a loud noise, unexpected light touch stimulation, or visual threat that were characterized by abrupt episodes of complete or partial loss of lower extremity tone. These events were not associated with impairment of consciousness, and immediate recovery was noted. Simultaneous surface EMG and video electroencephalogram revealed no epileptiform discharges in either patient. In the first patient, after unexpected tactile or auditory stimulation, tonic EMG activity in paraspinal muscles was lost briefly, similar to that seen in cataplexy. In the second patient, at 6 years of age, sudden nonepileptic drop episodes were induced by an unexpected tactile, auditory, or visual stimulation. At 11 years of age, his episodes had changed to brief myoclonic jerk and tonic spasm that were triggered by unexpected tactile and auditory stimuli. An increase in tonic EMG activity occurred during the attacks, consistent with hyperekplexia.

Conclusions. Our data suggest that SIDEs in CLS are a heterogeneous group of nonepileptic events that may manifest features of both cataplexy and hyperekplexia, even in the same patient.

Key Words: Coffin-Lowry syndrome • drop episodes • nonepileptic events • hyperekplexia • cataplexy

Abbreviations: CLS, Coffin-Lowry syndrome • SIDE, stimulus-induced drop episode • sEMG, surface electromyogram • VEEG, video electroencephalogram

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Received for publication Aug 12, 2002; Accepted Oct 9, 2002.

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