Prolonged apnoea with severe arterial hypoxaemia resulting from complex partial seizures

Cardiorespiratory abnormalities during epileptic seizures

Sudden unexpected death in epilepsy (SUDEP) is a leading cause of death in young and otherwise healthy patients with epilepsy, and sudden death is at least 20 times more common in epilepsy patients as compared to patients without epilepsy. A significant proportion of patients with epilepsy experience cardiac and respiratory complications during seizures. These cardiorespiratory complications are suspected to be a significant risk factor for SUDEP. Sleep physicians are increasingly involved in the care of epilepsy patients and a recognition of these changes in relation to seizures while a patient is under their care may improve their awareness of these potentially life-threatening complications that may occur during sleep studies. This paper details these cardiopulmonary changes that take place in relation to epileptic seizures and how these changes may relate to the occurrence of SUDEP.

Comparison of cardiorespiratory and EEG abnormalities with seizures in adults and children

Cardiopulmonary dysfunction and postictal generalized EEG suppression (PGES) are proposed as possible risk factors for the occurrence of SUDEP. The evolution of cardiorespiratory abnormalities with seizures has not been systematically studied for any age-related findings. Additionally, not many studies have looked into the possible effect of age-related brain maturation on PGES. The purpose of this study was to compare these SUDEP risk factors in adults versus children. We prospectively recorded cardiopulmonary abnormalities during seizures using pulse oximetry, EKG, and respiratory inductance plethysmography. Linear and logistic regression models adjusting for multiple seizures in a single patient were used to compare the cardiorespiratory and EEG findings between adults and children. We recorded 101 seizures in 26 children and 55 seizures in 22 adults. Ictal central apnea and bradycardia occurred more often in children than in adults (p=0.02 and p=0.008, respectively), while ictal tachycardia occurred more often in adults (p=0.001) than in children. Postictal generalized EEG suppression of longer duration occurred more often in adults (p=0.003) than in children. Minimum O2 saturation and seizure duration/generalization/lateralization did not significantly differ between adults and children (p>0.1). Children had more frontal lobe seizures, and adults had more temporal lobe seizures recorded (p=0.01). There may be an age-related effect on cardiorespiratory and EEG abnormalities associated with seizures, with higher rates of apnea and bradycardia in children and a much higher prevalence of PGES of longer duration in adults. This may indicate why, despite lower rates of cardiopulmonary dysfunction, adults die more frequently from SUDEP than children.

Cardiopulmonary complications during pediatric seizures: a prelude to understanding SUDEP

PURPOSE

Sudden unexpected death in epilepsy (SUDEP) is an important, unexplained cause of death in epilepsy. Role of cardiopulmonary abnormalities in the pathophysiology of SUDEP is unclear in the pediatric population. Our objective was to assess cardiopulmonary abnormalities during epileptic seizures in children, with the long-term goal of identifying potential mechanisms of SUDEP.

METHODS

We prospectively recorded cardiopulmonary functions using pulse-oximetry, electrocardiography (ECG), and respiratory inductance plethysmography (RIP). Logistic regression was used to evaluate association of cardiorespiratory findings with seizure characteristics and demographics.

KEY FINDINGS

We recorded 101 seizures in 26 children (average age 3.9 years). RIP provided analyzable data in 78% and pulse-oximetry in 63% seizures. Ictal central apnea was more prevalent in patients with younger age (p = 0.01), temporal lobe (p < 0.001), left-sided (p < 0.01), symptomatic generalized (p = 0.01), longer duration seizures (p < 0.0002), desaturation (p < 0.0001), ictal bradycardia (p < 0.05), and more antiepileptic drugs (AEDs; p < 0.01), and was less prevalent in frontal lobe seizures (p < 0.01). Ictal bradypnea was more prevalent in left-sided (p < 0.05), symptomatic generalized seizures (p < 0.01), and in brain magnetic resonance imaging (MRI) lesions (p < 0.1). Ictal tachypnea was more prevalent in older-age (p = 0.01), female gender (p = 0.05), frontal lobe (p < 0.05), right-sided seizures (p < 0.001), fewer AEDs (p < 0.01), and less prevalent in lesional (p < 0.05) and symptomatic generalized seizures (p < 0.05). Ictal bradycardia was more prevalent in male patients (p < 0.05) longer duration seizures (p < 0.05), desaturation (p = 0.001), and more AEDs (p < 0.05), and was less prevalent in frontal lobe seizures (p = 0.01). Ictal and postictal bradycardia were directly associated (p < 0.05). Desaturation was more prevalent in longer-duration seizures (p < 0.0001), ictal apnea (p < 0.0001), ictal bradycardia (p = 0.001), and more AEDs (p = 0.001).

SIGNIFICANCE

Potentially life-threatening cardiopulmonary abnormalities such as bradycardia, apnea, and hypoxemia in pediatric epileptic seizures are associated with predictable patient and seizure characteristics, including seizure subtype and duration.

Cyanotic breath-holding spell: a life-threatening complication after radical resection of a cervicomedullary ganglioglioma

Cyanotic breath-holding spell is a benign and self-limiting disease of young children but occasionally associated with sudden, unexpected death. The authors report a rare case in a 2-year-old girl with a severe form that started after radical resection of a cervicomedullary ganglioglioma. She was admitted to our hospital because of delayed and unstable gait. Since magnetic resonance imaging showed a cervicomedullary tumor, she underwent a radical resection and histology showed the tumor to be a ganglioglioma. Postoperatively, the function of the lower cranial nerves and cerebellum deteriorated and hemiparesis on the left became apparent, but she returned to the preoperative state in a few months. In addition, mild sleep apnea (Ondine curse) and severe cyanotic breath-holding spells occurred. The former responded to medication but the latter failed and continued several times per day with a rapid onset and progression of hypoxemia, loss of consciousness, sweating and opisthotonos. Five months after the operation, the patient returned home with a portable oxygen saturation monitor equipped with an alarm. This case indicates that cyanotic breath-holding spell, as well as sleep apnea, is critical during the early postoperative period. This is the first report observing that such spells may occur as a complication of radical resection of a cervicomedullary tumor.

Apnoeic attacks as an isolated manifestation of epileptic seizures in infants

Apnoea as an isolated manifestation of seizures is well described in neonates but is only occasionally observed in infants. We present data from four infants, with apnoea as the sole manifestation of seizures, documented by polygraphic ictal electroencephalogram (EEGC) and video recording. The four infants, after normal pregnancy and delivery at term, showed the first apnoea at the age of 2-11 months. The interictal EEG was normal. The ictal EEG and video recording showed in all infants a focal rhythmic alpha or theta activity with or without generalization, which lasted 40-120 seconds. The apnoea appeared a few seconds after the beginning of rhythmic activity and the heart rate remained unchanged during the apnoea. At 2 years' follow-up, three children are seizure-free under anti-epileptic therapy with normal psychomotor development in two, and a slight delay in the third infant. The fourth child has partial seizures and is severely retarded.

Nemaline myopathy: current concepts. The ENMC International Consortium and Nemaline Myopathy

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Sporadic apnea: paradoxical transformation to eupnea by perturbations that inhibit inspiration

We speculate that sporadic apneas may be initiated and terminated by stochastic neural perturbations arising within or impinging upon the respiratory oscillator. A curious situation can then arise in which tiny perturbations that inhibit inspiration, paradoxically stimulate breathing. The plausibility of the hypothesis is supported by numerical analysis of a noisy attractor-cycle oscillator, and in studies of a preterm sleeping infant with sporadic apnea; low-level vibratory stimulation transformed the irregular apneic rhythm to eupnea.

Apparent life-threatening event: a neurologic perspective

Of 46 infants who were investigated for apparent life-threatening events, central nervous system disorders were diagnosed in seven (15%). Convulsive disorders, intraventricular hemorrhage and hydrocephalus, absent corpus callosum, and development deficits were found. In four of the seven, no neurologic deficit was suspected before the event. Electroencephalographic studies (overnight in two) would have identified the disorder in all four. Electroencephalography is therefore a recommended routine procedure in investigation of apparent life-threatening events. Central nervous system disorders should be routinely ruled out in cases of apparent life-threatening event, even in the absence of clinical clues.

Dysrhythmias of the respiratory oscillator

Breathing is regulated by a central neural oscillator that produces rhythmic output to the respiratory muscles. Pathological disturbances in rhythm (dysrhythmias) are observed in the breathing pattern of children and adults with neurological and cardiopulmonary diseases. The mechanisms responsible for genesis of respiratory dysrhythmias are poorly understood. The present studies take a novel approach to this problem. The basic postulate is that the rhythm of the respiratory oscillator can be altered by a variety of stimuli. When the oscillator recovers its rhythm after such perturbations, its phase may be reset relative to the original rhythm. The amount of phase resetting is dependent upon stimulus parameters and the level of respiratory drive. The long-range hypothesis is that respiratory dysrhythmias can be induced by stimuli that impinge upon or arise within the respiratory oscillator with certain combinations of strength and timing relative to the respiratory cycle. Animal studies were performed in anesthetized or decerebrate preparations. Neural respiratory rhythmicity is represented by phrenic nerve activity, allowing use of open-loop experimental conditions which avoid negative chemical feedback associated with changes in ventilation.In animal experiments, respiratory dysrhythmias can be induced by stimuli having specific combinations of strength and timing. Newborn animals readily exhibit spontaneous dysrhythmias which become more prominent at lower respiratory drives. In human subjects, swallowing was studied as a physiological perturbation of respiratory rhythm, causing a pattern of phase resetting that is characterized topologically as type 0. Computational studies of the Bonhoeffer-van der Pol (BvP) equations, whose qualitative behavior is representative of many excitable systems, supports a unified interpretation of these experimental findings. Rhythmicity is observed when the BvP model exhibits recurrent periods of excitation alternating with refractory periods. The same system can be perturbed to a state in which amplitude of oscillation is attenuated or abolished. We have characterized critical perturbations which induce transitions between these two states, giving rise to patterns of dysrhythmic activity that are similar to those seen in the experiments. We illustrate the importance of noise in initiation and termination of rhythm, comparable to normal respiratory rhythm intermixed with spontaneous dysrhythmias. In the BvP system the incidence and duration of dysrhythmia is shown to be strongly influenced by the level of noise. These studies should lead to greater understanding of rhythmicity and integrative responses of the respiratory control system, and provide insight into disturbances in control mechanisms that cause apnea and aspiration in clinical disease states. (c) 1995 American Institute of Physics.

Partial seizures presenting as life-threatening apnea

Apneic episodes, quite common in newborns, are considered rare after age 1 month, when gastroesophageal reflux, cardiac arrhythmias, idiopathic central apnea, and seizures become included in differential diagnosis. Determining the cause of apnea is important as treatment differs significantly and can be harmful; Caffeine given for presumed idiopathic central apnea is reported to have precipitated seizures in 2 patients with apneic seizures. Two cases of partial seizures presenting as apnea in infants were studied. Interictal EEG was normal in 1 and showed focal spikes in the other. Video EEG monitoring (16 channel) showed focal ictal discharge originating from temporal areas clearly preceding onset of apnea in both patients. Because therapeutic options are sometimes diametrically opposite and interictal EEGs are particularly unreliable for diagnosis, we recommend video-EEG monitoring if there is any doubt about the diagnosis before starting treatment in patients with apneic episodes.

Diagnosis and management after life threatening events in infants and young children who received cardiopulmonary resuscitation

OBJECTIVE

To determine the mechanisms and thereby appropriate management for apparent life threatening events treated with cardiopulmonary resuscitation in infants and young children.

DESIGN

Prospective clinical and physiological study.

SETTING

Royal Brompton Hospital or in patients' homes, or both.

SUBJECTS

157 Patients referred at median age 2.8 months (range 1 week to 96 months), 111 (71%) had recurrent events, 44 were born preterm, 19 were siblings of infants who had died suddenly and unexpectedly, and 18 were over 12 months old.

INTERVENTIONS

Multichannel physiological recordings, including oxygenation, in hospital (n = 150) and at home (n = 61). Additional recordings with electroencephalogram, video, or other respiratory measures were used to confirm diagnoses. Management involved monitoring of oxygen at home, additional inspired oxygen, anticonvulsant treatment, or child protection procedures.

MAIN OUTCOME MEASURES

Abnormalities on recordings compared to published normal data and their correlation with clinical events; sudden death.

RESULTS

53 of 150 patients had abnormalities of oxygenation on hospital recordings, 28 of whom had an accompanying clinical event. Home recordings produced physiological data from 34 of 61 patients during subsequent clinical events. Final diagnoses were reached in 77 patients: deliberate suffocation by a parent (18), hypoxaemia induced by epileptic seizure (10), fabricated history and data (Munchausen syndrome by proxy; seven), acute hypoxaemia of probable respiratory origin (40), and changes in peripheral perfusion and skin colour without hypoxaemia (two). Four patients died: three suddenly and unexpectedly (none on home oxygen monitors) and one from pneumonia.

CONCLUSIONS

Identification of mechanisms is essential to the appropriate management of infants with apparent life threatening events.

Carpal tunnel syndrome in the mucopolysaccharidoses and related disorders

Eighteen patients with various mucopolysaccharidoses or mucolipidosis III were studied electrophysiologically to determine the presence or absence of carpal tunnel syndrome. In 17 patients this was clearly demonstrated, the only exception being a boy with mucopolysaccharidosis II, age 6 months at testing. All patients had a remarkable lack of symptoms. Carpal tunnel syndrome is a very common complication of the mucopolysaccharidoses and mucolipidosis III and should be actively looked for in affected patients. Early diagnosis and treatment offer the best chance of a good response to surgery.

Investigation of cyanotic/apneic episodes and sleep-related upper airway obstruction by long-term non-invasive bedside recordings

Over a 4 year period, investigations were performed on 226 infants and children suffering cyanotic episodes and 160 suspected to be the victims of sleep-related upper airway obstruction. These investigations have been considerably aided by long-term tape recordings of multiple cardiorespiratory and neurophysiological variables from non-invasive sensors. In addition to identifying the underlying mechanisms responsible for cyanotic episodes, recordings have identified the presence or absence of airway obstruction, documented its severity by its effects on oxygenation and on sleep-state organization, and evaluated objectively the effects of treatment. The recording system, which is transportable, has been especially developed for use outside of the specialized sleep laboratory and was used on patients in hospital wards and at home.

Hyperventilation in the awake state: potentially treatable component of Rett syndrome

Hyperventilation, which occurs in some patients with severe mental handicap, is a prominent feature in the histories of most girls with Rett syndrome but its mechanism and effects have not been established. Respiratory function was therefore studied in 18 patients with Rett syndrome and 23 healthy controls. Ten of the patients (56%), but none of the controls, hyperventilated only when awake, and began doing so after a period of normal breathing without hypoxaemia. After hyperventilation was established it was interspersed with prolonged periods of apnoea (over 19 seconds) accompanied by Valsalva manoeuvres. Hypoxaemia (less than 90%) occurred in 47% of these periods of apnoea and five (50%) of the patients had oxygen saturation values of under 50%. During hyperventilation severe hypocapnia developed in every patient, and recorded arterial pH measurements ranged from 7.47 to 7.60. A further four patients (22%) did not hyperventilate, but had clear histories of hyperventilation when younger. All had frequent apnoeic pauses accompanied by Valsalva manoeuvres. The remaining four girls (22%) neither hyperventilated nor gave a clear history of doing so. Three had occasional apnoeic pauses associated with the Valsalva manoeuvres. All but one of the 18 patients had increased quantities of periodic apnoea compared with the control subjects. The hypocapnic alkalaemia and hypoxaemia resulting from hyperventilation may contribute to the cerebral impairment in Rett syndrome. Since the hyperventilation is 'primary', and not secondary to preceding apnoea, it is potentially treatable. Further studies will determine if treatment is practical and of benefit.