Masayuki Shimohira

Motor disturbance during REM sleep in group A xeroderma pigmentosum

We investigated motor phenomena during rapid eye movement (REM) sleep in 13 patients with group A xeroderma pigmentosum aged from 11 to 39 months, and compared them with those obtained from 12 age‐matched controls. At the time of sleep study, they had no abnormality on routine electrophysiological examinations. The amount of REM sleep and the incidence of motor phenomena during REM sleep in patients were similar to those in age‐matched controls. However, using the newly designated indices, we demonstrated disturbance on both the tonic motor inhibition occurring during the whole REM sleep period and the phasic one acting simultaneously with horizontal rapid eye movements in these patients. Since the motor inhibition during REM sleep is mediated by the subcortical structures, our study indicate that these structures are functionally impaired in group A xeroderma pigmentosum even during the early stage of the illness.

Brainstem control of phasic muscle activity during REM sleep" a review and hypothesis

For the generation of phasic muscle activity during rapid eye movement (REM) sleep, strong motor excitation to overcome both tonic and phasic inhibition is needed at the motoneuron level. Descending pathways originating in the rostral pons (cholinoceptive (nucleus reticularis pontis oralis-->nucleus reticularis gigantocellularis, peri-locus coeruleus pars alpha-->nucleus reticularis magnocellularis) and cholinergic (pedunculopontine tegmental nucleus-->nucleus reticularis paramedianus) pathways) are involved in motor inhibition during REM sleep. Since the origins of excitatory drives related to phasic muscle activity during REM sleep are also in the brainstem, the occurrence of phasic muscle activity can be said to be determined by brainstem activity. We review the basic and clinical studies on phasic muscle activity during REM sleep and propose the possibility that it can be a beneficial parameter for assessing brainstem activity, especially in relation to its maturation during early stage of life.

Sleep Disturbance in Children with Growth Hormone Deficiency

We examined the effects of growth hormone (GH) deficiency on sleep development by performing all-night polysomnography in three female children with GH deficiency (GHD). The percentage of REM sleep seemed to be reduced before the treatment in 2 cases, and human GH (hGH) compensation slightly increased it. Submental twitch movements (mTMs), i.e., body movements during sleep localized in the submental muscle and lasting less than 0.5 seconds, were commonly disturbed in the three patients. Rapid eye movements in REM sleep (REMs) were reduced before the therapy in one case, this decrease being reversed on hGH compensation. REMs also seemed to increase after hGH treatment in the other two cases. Dopamines and cholinergic muscarinic agonists can cause GH release, while mTMs and REMs might be related to dopaminergic and cholinergic systems in the human brain. It is intriguing that GHD, and the disturbance of mTMs and REMs coexisted in children with GHD. Since a relatively poor social outcome in patients with GHD has been reported, even after hGH compensation, it is important to monitor their neurological development by means of evaluation of their sleep disturbance.

Phasic muscle activity during REM sleep in infancy-normal maturation and contrastive abnormality in SIDS/ALTE and West syndrome.

SUMMARY  The generation of phasic muscle activity during REM sleep is regulated by the brainstem. We proposed two sleep indices for phasic muscle activity during REM sleep, and examine their usefulness in assessing normal brainstem maturation and functional brainstem impairment during infancy. One ‐ the dissociation index (DI) ‐ seems to reflect maturation of the tonic inhibitory system functioning during REM sleep, and the other ‐ % body movements in REMs bursts (%BMs‐R) ‐ to reflect that of the phasic one. In normal infants, DI showed a gradual, linear and significant increase with age, whereas %BMs‐R showed a gradual and significant decrease with age. In infants with sudden infant death syndrome (SIDS) and one who had experienced apparent life‐threatening events (ALTE), the DI values were lower than those in controls, although %BMs‐R values were identical in the controls. In contrast, DI was variable in infants with West syndrome (WS), while %BMs‐R exceeded normal values. The tonic inhibitory system seemed to be specifically involved in SIDS and ALTE, but the phasic inhibitory one in WS. Anatomical differences between these inhibitory systems are also discussed.

Maturation of motility and motor inhibition in rapid-eye-movement sleep

OBJECTIVE To describe the age-related changes in the number of movements in rapid eye movement (REM) sleep, and to quantify the functional maturation of motor inhibition. STUDY DESIGN Gross movements, phasic mentalis muscle activity (PMMA), and a new index that expressed the shortness of PMMA (the proportion of short PMMA among all PMMA) were examined cross-sectionally in 87 healthy children from premature babies to preadolescents by means of a single (all-night) polysomnography. RESULTS The incidence of gross movements and long PMMA decreased with age, whereas that of short PMMA increased with age. The new index exhibited an age-related increase, with the highest correlation with age among sleep parameters examined, and reached an adult level after 6 years of age. CONCLUSION We found that the age-related reduction of PMMA duration, which was expressed by a new index, occurred in parallel with the maturation of the inhibitory system that is tonically activated during REM sleep. We named this index the tonic inhibition index and concluded that the neuronal system involved in motor inhibition during REM sleep was still maturing during early childhood. We propose the tonic inhibition index as a useful quantitative indicator for the maturity of the inhibitory system.

Video analysis of gross body movements during sleep

Abstract Gross body movements (GM) during sleep, classified into four GM types by the involved parts of body, were evaluated using two‐dimensional video analysis in five normal children aged 4–12 years. The rate of occurrence of all GM types showed apparent sleep stage dependency. Among four GM types, GM‐1 (GM with axial rotation) was the most frequent. Averaged duration of GM‐1 was the longest. A total of 77.2% of GM‐1 started with the contraction of chin muscle and 35% of total sleep changes (tSC) were related to GM. A total of 5.6% of tSC following GM shifted to the deeper stage. Further evaluation is necessary in order to understand the physiological mechanism of GM.

Phasic motor activity reduction occurring with horizontal rapid eye movements during active sleep in human

We describe the phasic reduction of motor activity occurring with horizontal rapid eye movements (REMs) during active sleep in 15 children (12 healthy children and 3 patients with severe brain damage). A REM-related decrease in intercostal muscle activity was demonstrated by averaging integrated surface electromyograms. In the healthy subjects, this reduction had a mean latency from the REM onset of 37.1 ms and a duration of 225.9 ms. This phenomenon was also observed in the 3 patients who had lost cerebral function. We hypothesized a brainstem origin for the effect. A REM-related mentalis muscle activity loss, detected by averaging mentalis muscle twitches, was observed in 10 healthy children among the subjects. This loss began at 59.1 ms before the onset of REMs and lasted for 230.2 ms on average. In addition, a transient decrease in integrated REM activity surrounding mentalis muscle twitches (a twitch-related reduction of REMs) was observed. We discuss the similarity between REM-related phasic reduction of muscle activity obtained for intercostal and mentalis muscles and pontogeniculo-occipital (PGO) wave-related inhibitory postsynaptic potentials reported for feline lumbar and trigeminal motoneurons, respectively. We then assume the presence of a phasic event generator, functioning during active sleep in healthy humans, which triggers at least three generators; that is, the generator of PGO waves (or REMs), motor inhibition, and of motor excitation including muscle twitches.

Tuberous sclerosis : epileptogenicity and multimodal presurgical evaluations

Abstract. We report on a patient with tuberous sclerosis-related epilepsy who benefited from surgical treatment. Various presurgical evaluations, including positron emission tomography (PET), made it possible for us to localize the epileptic focus accurately. In this paper, we stress the importance of performing multimodal evaluations to determine which tubers really possess epileptogenicity. In addition, the implications of PET in tuberous sclerosis-related epilepsy are described.

Nocturnal Enuresis and the Pontine Reticular Formation

Objectives: To assess the previously proposed hypothesis that enuretic patients have a dysfunction in the pontine reticular formation.Methods: In 18 patients with intractable nocturnal enuresis, rapid eye movement (REM)–related phasic chin muscle activity loss in REM sleep was examined by means of a single–night polysomnography.Results: In 5 of 18 patients, this physiologically seen phenomenon was found to be disturbed.Conclusions: Since REM–related phasic chin muscle activity loss is disturbed by the functional impairment in the pontine reticular formation, some enuretic patients could be considered as presenting a dysfunction in this structure.

A patient with mitochondrial myopathy associated with isolated succinate dehydrogenase deficiency

We report on a boy with normal mental development who had muscle hypotonia and congenital dislocation of the hip and knee joints. Histochemical and biochemical examinations of his muscle specimen revealed no succinate dehydrogenase (SDH) activity. Since the NADH cytochrome c reductase and cytochrome c oxidase activities were normal, we concluded that he had an isolated SDH deficiency. Our patient provides further evidence for the clinical variability of this disorder.