Suresh Kotagal

Fluctuations in autonomic nervous activity during sleep displayed by power spectrum analysis of heart rate variability.

Objective The use of an efficient noninvasive method to investigate the autonomic nervous system and cardiovascular control during sleep. Background Beat-to-beat heart rate variability displays two main components: a low-frequency (LF) one representing sympathetic and parasympathetic influence and a high-frequency (HF) component of parasympathetic origin. Sympathovagal balance can be defined as LF/HF ratio. Methods/design We reviewed normal, standardly staged all-night polysomnograms from 10 healthy children aged 6 to 17 years. Recorded 256-second traces of heart rate and respiration were sampled. Power spectra of instantaneous heart rate and respiration were computed using a fast Fourier transform method. Results The study revealed a decrease in LF during sleep, with minimal values during non-REM slow-wave sleep and elevated levels similar to those of wakefulness during REM. HF increased with sleep onset, reaching maximal values during slow-wave sleep, and behaved as a mirror image of LF. LF/HF ratio displayed changes similar to those in LF. Conclusion The sympathetic predominance that characterizes wakefulness decreases during non-REM sleep, is minimal in slow-wave sleep, and surges toward mean awake levels during REM sleep. The autonomic balance is shifted toward parasympathetic predominance during slow-wave sleep. This noninvasive method used to outline autonomic activity achieves results that are in complete agreement with those obtained with direct invasive tools.

Childhood-onset restless legs syndrome.

The clinical characteristics of childhood‐onset restless legs syndrome are described. Thirty‐two of 538 subjects (5.9%) examined in our sleep disorders center received diagnoses of restless legs syndrome. They were classified based on published criteria into probable (n = 9/32 or 28%) and definite (n = 23/32 or 78%) categories. Apart from an earlier age of diagnosis of the probable group, no differences were found between the two categories. Sleep onset or sleep maintenance insomnia was the most common symptoms, being present in 28 of 32 subjects (87.5%). Inattentiveness was seen in 8 of 32 subjects (25%). Serum ferritin levels were measured in 24 of 32 subjects and were below 50μg/L in 20 of 24 subjects (83%). A family history of restless legs syndrome was present in 23 of 32 (72%) subjects, with mothers almost three times more likely to be affected than fathers (p = 0.02). We conclude that iron deficiency and a strong family history are characteristic of childhood‐onset restless legs syndrome. Ann Neurol 2004.

SLEEP ABNORMALITIES IN PATIENTS WITH SEVERE CEREBRAL PALSY

The all‐night polysomnographic findings of nine patients with spastic quadriparesis (mean age 36‐7 months) were analysed retrospectively and compared with those of nine age‐matched controls (rnean age 37‐4 months). The cerebral palsy group had significantly more respiratory disturbances per hour of sleep, with five of nine being diagnosed as having obstructive sleep apnea. They also had fewer changes in body position during the night. Interictal epileptiform discharges averaged 23‐3 per cent of the total arousals in the cerebral palsy group. Obstructive apnea, decreased ability to change body position, and interictal epileptiform discharges are prevalent in the sleep of patients with severe cerebral palsy, and contribute towards its disruption.

Autonomic cardiovascular control in children with obstructive sleep apnea

Autonomic cardiorespiratory control changes with sleep-wake states and is influenced by sleep-related breathing disorders. Power spectrum (PS) analysis of instantaneous fluctuations in heart rate (HR) is used to investigate the role of the autonomic nervous system (ANS) in cardiorespiratory control. The two spectral regions of interest are the low frequency component (LF) and high frequency component (HF).The aim of the present study was to investigate the autonomic cardiorespiratory control in children with obstructive sleep apnea (OSA) syndrome. We studied 10 children with OSA versus 10 normal children. All subjects underwent whole night polysomnography. Spectral analysis of the HR and breathing signals was performed for 256 second long, artifact-free epochs in each sleep-wake state. The LF power was higher in the OSA group compared with control subjects for all states, reflecting enhanced sympathetic activity in OSA subjects. The results indicated sympathetic predominance during REM sleep in all subjects and parasympathetic predominance in slow wave sleep only in controls. The autonomic balance (LF/HF) was significantly higher in OSA patients than in control subjects, at all stages during night sleep, and while awake before sleep onset. An index of overall autonomic balance (ABI) was computed for each subject and correlated well with the measured respiratory disturbance index (RDI).

Extracorporeal Membrane Oxygenation for Newborn Respiratory Failure

Jugular vein-carotid artery extracorporeal membrane oxygenation (ECMO) was utilized in 22 newborns (16 male and 6 female) 1 to 12 days old with respiratory failure due to meconium aspiration (12 patients), diaphragmatic hernia (4), persistent fetal circulation (3), hyaline membrane disease (2), and Rh incompatibility (1). Prior to ECMO, all patients had alveolar-arterial O2 pressure gradients greater than 580 mm Hg (predicted mortality greater than 90%), weighed more than 1,800 gm, had a gestation period of longer than 35 weeks, and had no cerebral hemorrhage. The duration of ECMO was 41 to 310 hours (mean, 134.5 hours). Nineteen (86%) of the 22 patients survived ECMO. Death was caused by lung disease (2) and cerebral hemorrhage (1). Four other patients died 6 to 40 days after ECMO of pulmonary hypoplasia (1), pneumonia (1), cerebral edema (1), and hepatorenal failure (1). Complications during ECMO were few and easily managed. Fifteen infants (68%) are alive 1 to 18 months after ECMO. Three have neurological deficit (2 severe, 1 mild). Bayley Developmental Examinations in 4 survivors now more than 12 months old are normal. Extracorporeal membrane oxygenation is an aggressive but effective technique of life support in newborns refractory to conventional respiratory management. Potential complications of ECMO mandate strict aseptic technique, constant monitoring, and multidisciplinary patient management.

Conservative management of spinal epidural hematoma in hemophilia

Two patients with hemophilia and spinal epidural hematoma, who were treated successfully with serial Factor VIII infusions, are reported. This form of conservative therapy may circumvent the need for decompressive laminectomy and its attendant complications in instances in which the neurologic deficit is mild or stable. Somatosensory evoked potential studies were useful in documenting spinal cord dysfunction in 1 of the 2 patients.

Sleep Apnea in Patients Receiving Growth Hormone

Among 145 patients treated with recombinant human growth hormone (GH), four devel oped sleep apnea (two obstructive, two mixed) associated with tonsillar and adenoidal hypertrophy in three. These four patients had no local risk factors predisposing to upper airway obstruction (i.e., frequent pharyngitis or sinusitis). Clinical and/or polysomnographic features of sleep apnea improved following cessation of GH therapy in one patient, and following tonsillectomy and adenoidectomy in all patients. The present observations indicate that, albeit rarely, obstructive and/or central sleep apnea may occur in children treated with GH. Polysomnography should be considered if symptoms of snoring, interrupted sleep, daytime somnolence—particularly if associated with tonsillar hypertrophy—appear in children during GH therapy.

Ependymal Abnormalities in Lissencephaly/Pachygyria

The ependyma was examined in eight children with neuroblast migratory disorders of diverse origin: three cases of lissencephaly type 1 with severe to mild degrees of agyria/pachygyria, four cases of lissencephaly type 2 in Fukuyama muscular dystrophy and the Walker-Warburg syndrome, and one case of hemimcgalencephalic pachygyria. Morphological and immunohistochemical abnormalities of the ependyma were strikingly similar in all. Discontinuities were disproportionate to the degree of ventriculomegaly. In some regions, the ependyma remained a pseudostratified columnar epithelium, though basal processes were absent. The poles of the horns of the lateral ventricles were replaced by extensive heterotopic ependymal rosettes. Rosettes and rows of ependyma also were in other subventricular sites. Subependymal nodules of large astrocytes and their processes bulged into the ventricular lumen after infancy. Ependymal cells did not express glial fibrillary acidic protein, but showed persistent expression of S-100 protein, cytokeratin CK-904 and sometimes vimentin long after these proteins normally disappear. An abnormal ependyma in lissencephaly/pachygyria may contribute to disturbances in neurono-genesis, guidance of axonal projections and neuroblast migrations; it may be a primary factor in pathogenesis.

Narcolepsy in children.

Childhood narcolepsy is frequently under-diagnosed. Hypersomnolence may not always be accompanied by cataplexy, sleep paralysis, or hypnagogic hallucinations in the early stages. Pathophysiologic considerations revolve around an altered central nervous system catecholamine-acetylcholine balance. Both idiopathic and symptomatic forms have been described. Serial polysomnography and multiple sleep latency tests may be required to establish a definitive diagnosis. The long-term management requires the provision of both pharmacological and non-pharmacological forms of therapy.

Hypersomnia, bithalamic lesions, and altered sleep architecture in Kearns‐Sayre syndrome

An 11-year-old boy with Kearns-Sayre syndrome developed hypersomnia associated with bithalamic lesions and had complete absence of sleep spindles on a nocturnal polysomnogram.