[Smith-Magenis syndrome is an association of behavioral and sleep/wake circadian rhythm disorders]

Smith-Magenis syndrome (SMS) is a genetic disorder characterized by the association of facial dysmorphism, oral speech delay, as well as behavioral and sleep/wake circadian rhythm disorders. Most SMS cases (90%) are due to a 17p11.2 deletion encompassing the RAI1 gene; other cases stem from mutations of the RAI1 gene. Behavioral issues may include frequent outbursts, attention deficit/hyperactivity disorders, self-injuries with onychotillomania and polyembolokoilamania (insertion of objects into bodily orifices), etc. It is noteworthy that the longer the speech delay and the more severe the sleep disorders, the more severe the behavioral issues are. Typical sleep/wake circadian rhythm disorders associate excessive daytime sleepiness with nocturnal agitation. They are related to an inversion of the physiological melatonin secretion cycle. Yet, with an adapted therapeutic strategy, circadian rhythm disorders can radically improve. Usually an association of beta-blockers in the morning (stops daily melatonin secretion) and melatonin in the evening (mimics the evening deficient peak) is used. Once the sleep disorders are controlled, effective treatment of the remaining psychiatric features is needed. Unfortunately, as for many orphan diseases, objective guidelines have not been drawn up. However, efforts should be focused on improving communication skills. In the same vein, attention deficit/hyperactivity disorders, aggressiveness, and anxiety should be identified and specifically treated. This whole appropriate medical management is underpinned by the diagnosis of SMS. Diagnostic strategies include fluorescent in situ hybridization (FISH) or array comparative genomic hybridization (array CGH) when a microdeletion is sought and Sanger sequencing when a point mutation is suspected. Thus, the diagnosis of SMS can be made from a simple blood sample and should be questioned in subjects of any age presenting with an association of facial dysmorphism, speech delay with behavioral and sleep/wake circadian rhythm disorders, and other anomalies including short stature and mild dysmorphic features.

Smith-Magenis syndrome

Smith-Magenis syndrome (SMS) is a mental retardation syndrome with distinctive behavioral characteristics, dysmorphic features, and congenital anomalies ascribed to an interstitial deletion of chromosome 17p11.2. Severe sleep disturbances and maladaptive daytime behavior have been linked to an abnormal circadian rhythm of melatonin with a diurnal instead of nocturnal secretion of this hormone. SMS provides a demonstration of a biological basis for sleep disorder in a genetic disease. Considering that clock genes mediate the generation of circadian rhythm, haploinsufficiency for a circadian system gene, mapping to chromosome 17p11.2, may cause the inversion of the melatonin circadian rhythm in SMS. The disorder of circadian timing in SMS may also affect entrainment pathway (retinohypothalamic tract), pacemaker functions (suprachiasmatic nuclei), or synthesis and release of melatonin by the pineal gland. Elucidating pathophysiological mechanisms of behavioral phenotypes in genetic disease can provide an original therapeutic approach in SMS: blockade of endogenous melatonin production during the day combined with exogenous melatonin administration in the evening.

Anatomical and functional brain imaging evidence of lenticulo-insular anomalies in Smith Magenis syndrome

Smith Magenis syndrome (SMS) is a clinically recognizable contiguous gene syndrome ascribed to an interstitial deletion of chromosome 17p11.2. The neurobehavioral phenotype of SMS includes mental retardation, speech delay, hyperactivity, attention deficit, decreased sensitivity to pain, self-injury, aggressive behavior and sleep disturbance. Therefore, we performed anatomical and functional brain imaging studies in five SMS boys. Anatomical magnetic resonance imaging (MRI) was analyzed using optimized voxel-based morphometry (VBM). This method can detect structural anomalies not apparent on visual inspection of the scans. Two comparison groups with similar mean age were studied: Group A with 12 healthy control children and Group B with 5 children with idiopathic mental retardation. In addition, positron emission tomography (PET) and water-labeled method were used to investigate a putative localized brain dysfunction in SMS. The control group was composed of mentally retarded children (Group B). A significant bilateral decrease of grey matter concentration was detected in the insula and lenticular nucleus in SMS children. In addition, a significant hypoperfusion was found in the same regions in SMS. These anatomo-functional evidences of bilateral insulo-lenticular anomalies in SMS are consistent with neurobehavioral symptoms of the disease. The identification of localized brain anomalies in SMS may help in understanding how this well-defined genetic entity can lead to a relatively specific severe neurobehavioral syndrome.

[Inversion of the circadian melatonin rhythm in Smith-Magenis syndrome]

Smith-Magenis syndrome (SMS) is a genetic disease ascribed to an interstitial deletion on chromosome 17 (del 17p11); the prevalence is 1/25,000 births. The diagnosis is made on high-resolution karyotype confirmed by FISH. Clinical features include mild dysmorphism, short stature, other malformations (heart, renal, neurologic diseases). Mental retardation is constant; there are major behavioral disturbances and severe sleep disorders. We studied sleep disorders and melatonin secretion in SMS children and we have shown inversion of the circadian rhythm of melatonin, abnormally secreted during the day. This is the first biological model of behavioral and sleep disorder in a genetic disease. Therapeutic approach using beta-blockers in the morning and melatonin in the evening, reset circadian rhythm of melatonin, improve behavior and restore sleep.

beta(1)-adrenergic antagonists improve sleep and behavioural disturbances in a circadian disorder, Smith-Magenis syndrome

Smith-Magenis syndrome (SMS) is a clinically recognisable contiguous gene syndrome ascribed to interstitial deletions of chromosome 17p11.2. Patients have a phase shift of their circadian rhythm of melatonin with a paradoxical diurnal secretion of the hormone. Serum melatonin levels and day-night behaviour were studied in nine SMS children (aged 4 to 17 years) given acebutolol, a selective beta(1)-adrenergic antagonist (10 mg/kg early in the morning). Cardiac examination, serum melatonin, motor activity recordings, and sleep diaries were monitored before and after drug administration. The present study shows that a single morning dose of acebutolol suppressed the inappropriate secretion of melatonin in SMS. A significant improvement of inappropriate behaviour with increased concentration, delayed sleep onset, increased hours of sleep, and delayed waking were also noted. These results suggest that beta(1)-adrenergic antagonists help to manage hyperactivity, enhance cognitive performance, and reduce sleep disorders in SMS.

Inversion of the circadian rhythm of melatonin in the Smith-Magenis syndrome

OBJECTIVE

The objective was to determine the circadian rhythm of melatonin in the Smith-Magenis syndrome (SMS), which causes behavioral problems and sleep disturbance.

STUDY DESIGN

Questionnaires, sleep consultations, and sleep diaries were obtained in 20 children with SMS (9 girls, 11 boys aged 4 to 17 years). Actigraphy, electroencephalography, and the circadian variations of plasma melatonin, cortisol, and growth hormone were recorded in 8 patients. Early sleep onset, early sleep offset, and sleep attack indicated sleep disturbance.

RESULTS

All children with SMS had a phase shift of their circadian rhythm of melatonin. Time at onset of melatonin secretion was 6 AM +/- 2 (control group: 9 P.M. +/- 2). Peak time was 12 PM +/- 1 (control group: 3:30 AM +/- 1:30), and melatonin offset was at 8 PM +/- 1 (control group: 6 AM +/- 1). Behavioral problems correlated with the inverted circadian rhythm of melatonin.

CONCLUSION

Considering that clock genes mediate the generation of circadian rhythms, we suggest that haploinsufficiency for a circadian system gene mapping to chromosome 17p11.2 may cause the inversion of the circadian rhythm of melatonin in SMS.

[Ambulatory EEG monitoring (Medilog 9000). Initial results in a pediatric population]

The authors report their experience of ambulatory EEG monitoring (Medilog 9000, Oxford Instruments) in a paediatric population. They describe the method of recording, the system of lecture and the paper reproduction possibilities. Thirty-four 24 h cassettes have been recorded and analysed in 30 children aged from 1 month to 17 years. Six infants (under 1 year) had convulsions or spasms; 20 children were epileptic and 5 children were recorded for different reasons. Sleep was obtained in all cases. Seizures were recorded in 5 of 6 infants under 1 year of age, and in 11 of 20 epileptic children. The advantages and applications of this method are discussed.