Journal of the Neurological Sciences, 1978, 38 : 207-213 © Elsevier/North-Holland Biomedical Press
207
PERIODIC NOCTURNAL MYOCLONUS IN A PATIENT WITH HYPERE X P L E X I A ( S T A R T L E DISEASE)
J. H. M. de GROEN and H. A. C. KAMPHUISEN Leiden University Medical Center, Leiden (The Netherlands)
(Received 7 March, 1978) (Accepted 3 May, 1978)
SUMMARY The periodic nocturnal myoclonus of a patient with hyperexplexia has been studied. Evidence has been given that the jerks are spontaneous arousal reactions. The temporal characteristics of the jerks have been analysed. The jerks appear to be correlated with the respiratory rhythm and the data suggest a correlation of the jerks with circulatory and respiratory higher order waves. The results are discussed with relation to the literature concerning spontaneous sleep jerks.
INTRODUCTION Hyperexplexia or startle disease is a hereditary (Suhren, Bruyn and Tuynman 1966; Gastaut and Villeneuve 1967) disease, characterized by an abnormal exaggerated startle reaction. An unexpected stimulus causes a short-lasting generalized muscular stiffness, associated with loss of voluntary muscle control. There is no disturbance of consciousness. The symptom probably is caused by hyperexcitability of the brain-stem arousal system. During sleep, patients with hyperexplexia sometimes show spontaneous sleep jerks, identical to those observed in normal subjects but more intense and frequent (Gastaut and Villeneuve 1967). This article reports the spontaneous sleep jerks of a child with hyperexplexia. Case history Our patient, K.W., is a girl, 2½years old, out of the family with hereditary hyperexplexia, studied by Suhren et al. (1966). After a normal pregnancy, birth was one week before term, but uneventful. The birth weight was 2380 g, the Apgar score 8 after 1 min. Soon after birth, the mentally retarded child presented the characteristic symptomsofhyperexplexia: hypertonia, hypokinesia and an abnormal startle reaction. She differs from the other afflicted members of her family, because of the severity of the symptoms and of the occurrence of periodic nocturnal myoclonus. Treatment with anti-epileptics and sedatives was unsatisfactory.
208
Neurologicalexamination: normalfindings.Therewereno abnormalitiesin the repeated EEG's, apart from a slight underdevelopmentof the physiologicalsleep activitiesduring N-REM sleep. Once, whenthechildwasabout2yearsold, leftRolandicspikes,not correlatingwith the nocturnalmyoclonus, occurred during N-REM sleep. In myoclonicepilepsythe Somato-SensoryEvoked Responseis augmented(Halliday1975). In our patientthe SSER was normaland amountedto 5 ltV. Photostimulation did not provoke irritative activity. Method of polygraphic sleep registration and data analysis Several periods of day-time sleep and the sleep of one whole night were registered polygraphically on a 20 channels Van Gogh EEG apparatus and in part on a tape recorder. There were 9 EEG-leads, 7 EMG-leads (surface electrodes submentally and on 6 extremity muscles), EOG, respiratory movement (strain gauge), ECG and PGR. The sleep stages of the night sleep record were scored manually, per minute, in agreement with international criteria. An unselected part of non-interrupted SW-sleep has been used for the calculation of the correlation between respiration and jerks. The interval histograms of the jerks have been plotted by means of a Data Retrieval Computer. RESULTS
(a) Hypnogram of the night sleep record (Fig. 1) The night sleep consists mainly of SW-sleep stages I, II and III, interrupted by short awakenings; 5 irregular sleep cycles may be discerned, only the 4th with a period of REM-sleep (A in Fig. 1). During relaxed waking and SW-sleep, the frequency of the jerks (B in Fig. 1) is about 5 min and fairly constant. During REM-sleep and during periods of alertness the jerks disappear (C in Fig. l).
(b) Analysis of the jerks The jerks consist of short-lasting bursts of activity, synchronous in all muscles. The EEG shows often an activation pattern: irritative EEG-phenomena are lacking. Each SW-sleep stage has a different EEG activation pattern during the jerk (Fig. 2). During relaxed waking (A in Fig. 2) the jerk is accompanied by a desynchronisation of the EEG-activity and opening of the eyes; during dozing (B in Fig. 2) the jerk is accompanied by a paradoxical a-0 pattern; during light sleep (C in Fig. 2) by 0-bursts and during deep sleep (D in Fig. 2) by primitive K-complexes. The EEG activation pattern coincides with the jerk or precedes it. The data concerning the H-reflex (F in Fig. 2) and the tendon reflex (G in Fig. 2) of the triceps muscle are obtained during a day-time sleep registration. The equal increase of both H-reflex and tendon reflex during the jerk suggests that the jerk mainly is caused by an excitability increase of a-motoneurones. The accompanying signs of EEG activation suggest that the jerks arise from sudden repeatedly occurring increase of muscle tone, as a part of spontaneous arousal reactions.
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207
PERIODIC NOCTURNAL MYOCLONUS IN A PATIENT WITH HYPERE X P L E X I A ( S T A R T L E DISEASE)
J. H. M. de GROEN and H. A. C. KAMPHUISEN Leiden University Medical Center, Leiden (The Netherlands)
(Received 7 March, 1978) (Accepted 3 May, 1978)
SUMMARY The periodic nocturnal myoclonus of a patient with hyperexplexia has been studied. Evidence has been given that the jerks are spontaneous arousal reactions. The temporal characteristics of the jerks have been analysed. The jerks appear to be correlated with the respiratory rhythm and the data suggest a correlation of the jerks with circulatory and respiratory higher order waves. The results are discussed with relation to the literature concerning spontaneous sleep jerks.
INTRODUCTION Hyperexplexia or startle disease is a hereditary (Suhren, Bruyn and Tuynman 1966; Gastaut and Villeneuve 1967) disease, characterized by an abnormal exaggerated startle reaction. An unexpected stimulus causes a short-lasting generalized muscular stiffness, associated with loss of voluntary muscle control. There is no disturbance of consciousness. The symptom probably is caused by hyperexcitability of the brain-stem arousal system. During sleep, patients with hyperexplexia sometimes show spontaneous sleep jerks, identical to those observed in normal subjects but more intense and frequent (Gastaut and Villeneuve 1967). This article reports the spontaneous sleep jerks of a child with hyperexplexia. Case history Our patient, K.W., is a girl, 2½years old, out of the family with hereditary hyperexplexia, studied by Suhren et al. (1966). After a normal pregnancy, birth was one week before term, but uneventful. The birth weight was 2380 g, the Apgar score 8 after 1 min. Soon after birth, the mentally retarded child presented the characteristic symptomsofhyperexplexia: hypertonia, hypokinesia and an abnormal startle reaction. She differs from the other afflicted members of her family, because of the severity of the symptoms and of the occurrence of periodic nocturnal myoclonus. Treatment with anti-epileptics and sedatives was unsatisfactory.
208
Neurologicalexamination: normalfindings.Therewereno abnormalitiesin the repeated EEG's, apart from a slight underdevelopmentof the physiologicalsleep activitiesduring N-REM sleep. Once, whenthechildwasabout2yearsold, leftRolandicspikes,not correlatingwith the nocturnalmyoclonus, occurred during N-REM sleep. In myoclonicepilepsythe Somato-SensoryEvoked Responseis augmented(Halliday1975). In our patientthe SSER was normaland amountedto 5 ltV. Photostimulation did not provoke irritative activity. Method of polygraphic sleep registration and data analysis Several periods of day-time sleep and the sleep of one whole night were registered polygraphically on a 20 channels Van Gogh EEG apparatus and in part on a tape recorder. There were 9 EEG-leads, 7 EMG-leads (surface electrodes submentally and on 6 extremity muscles), EOG, respiratory movement (strain gauge), ECG and PGR. The sleep stages of the night sleep record were scored manually, per minute, in agreement with international criteria. An unselected part of non-interrupted SW-sleep has been used for the calculation of the correlation between respiration and jerks. The interval histograms of the jerks have been plotted by means of a Data Retrieval Computer. RESULTS
(a) Hypnogram of the night sleep record (Fig. 1) The night sleep consists mainly of SW-sleep stages I, II and III, interrupted by short awakenings; 5 irregular sleep cycles may be discerned, only the 4th with a period of REM-sleep (A in Fig. 1). During relaxed waking and SW-sleep, the frequency of the jerks (B in Fig. 1) is about 5 min and fairly constant. During REM-sleep and during periods of alertness the jerks disappear (C in Fig. l).
(b) Analysis of the jerks The jerks consist of short-lasting bursts of activity, synchronous in all muscles. The EEG shows often an activation pattern: irritative EEG-phenomena are lacking. Each SW-sleep stage has a different EEG activation pattern during the jerk (Fig. 2). During relaxed waking (A in Fig. 2) the jerk is accompanied by a desynchronisation of the EEG-activity and opening of the eyes; during dozing (B in Fig. 2) the jerk is accompanied by a paradoxical a-0 pattern; during light sleep (C in Fig. 2) by 0-bursts and during deep sleep (D in Fig. 2) by primitive K-complexes. The EEG activation pattern coincides with the jerk or precedes it. The data concerning the H-reflex (F in Fig. 2) and the tendon reflex (G in Fig. 2) of the triceps muscle are obtained during a day-time sleep registration. The equal increase of both H-reflex and tendon reflex during the jerk suggests that the jerk mainly is caused by an excitability increase of a-motoneurones. The accompanying signs of EEG activation suggest that the jerks arise from sudden repeatedly occurring increase of muscle tone, as a part of spontaneous arousal reactions.
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