EEG in epilepsy: current perspectives

Intracerebral electrographic activity following a single dose of diazepam nasal spray: A pilot study

OBJECTIVE

Rescue benzodiazepine medication can be used to treat seizure clusters, which are intermittent, stereotypic episodes of frequent seizure activity that are distinct from a patient's usual seizure pattern. The NeuroPace RNS® System is a device that detects abnormal electrographic activity through intracranial electrodes and administers electrical stimulation to control seizures. Reductions in electrographic activity over days to weeks have been associated with the longer-term efficacy of daily antiseizure medications (ASMs). In this pilot study, electrographic activity over hours to days was examined to assess the impact of a single dose of a proven rescue therapy (diazepam nasal spray) with a rapid onset of action.

METHODS

Adult volunteers (>18 years old) with clinically indicated RNS (stable settings and ASM usage) received a weight-based dose of diazepam nasal spray in the absence of a clinical seizure. Descriptive statistics for a number of detections and a sum of durations of detections at 10-min, hourly, and 24-h intervals during the 7-day (predose) baseline period were calculated. Post-dose detections at each time interval were compared with the respective baseline-detection intervals using a 1 SD threshold. The number of long episodes that occurred after dosing also were compared with the baseline.

RESULTS

Five participants were enrolled, and four completed the study; the excluded participant had recurrent seizures during the study. There were no consistent changes (difference >1 SD) in detections between post-dose and mean baseline values. Although variability was high (1 SD was often near or exceeded the mean), three participants showed possible trends for reductions in one or more electrographic variables following treatment.

SIGNIFICANCE

RNS-assessed electrographic detections and durations were not shown to be sensitive measures of short-term effects associated with a single dose of rescue medication in this small group of participants. The variability of detections may have masked a measurable drug effect.

PLAIN LANGUAGE SUMMARY

Rescue drugs are used to treat seizure clusters. Responsive neurostimulation (RNS) devices detect and record epilepsy brain waves and then send a pulse to help stop seizures. This pilot study looked at whether one dose of a rescue treatment changes brain activity detected by RNS. There was a very wide range of detections, which made it difficult to see if or how the drug changed brain activity. New studies should look at other types of brain activity, multiple doses, and larger patient groups.

A study of the significance of photoparoxysmal responses and spontaneous epileptiform discharges in the EEG in childhood epilepsy

AIM

In clinical practice, there is a prevailing notion that photosensitivity mostly occurs in children with epilepsy (CWE) with idiopathic generalized epilepsy. We investigated the distribution of epilepsy types and etiology in photosensitive children and the associations with specific clinical and electroencephalogram (EEG) variables.

METHODS

In this retrospective cohort study, clinical data were acquired from all children that showed photosensitivity during systematic intermittent photic stimulation (IPS), over a 10-year interval at a tertiary level Children's Hospital, Winnipeg. Patient demographics, EEG findings, and clinical data and symptoms during IPS were abstracted. Classification of diagnoses using the International League Against Epilepsy (ILAE) 2017 guidelines was done by an expert panel.

RESULTS

Seventy-eight photosensitive children were identified. Forty (51.3%) had generalized epilepsy (idiopathic: 27, structural: 2, other: 11) compared with 19 (24.4%) focal (idiopathic: 1, structural: 2, other: 16), 8 (10.3%) combined focal and generalized (structural: 4, other: 4), and 11 (14.1%) unknown epilepsy (other: 11); (χ² (3) = 32.1, p = .000). Self-sustaining or outlasting photoparoxysmal responses (PPRs) occurred in association with all epilepsy types; however, the EEGs of focal CWE without treatment comprised almost solely of PPRs which outlasted the stimulus (8/10), in contrast to only 8/17 of focal CWE with treatment and to 13/26 of generalized epilepsy without treatment. Most frequency intervals in individual patients were less under treatment: a decrease in standardized photosensitivity range (SPR) was seen in 5 CWE, an increase in 2, and no change in 1 during treatment. Both CWE with focal and generalized epilepsy showed abnormal activity on EEG during hyperventilation (40% vs 65.7%). Thirteen out of 14 CWE with clinical signs during IPS had independent spontaneous epileptiform discharges (SEDs) in the EEG recording.

CONCLUSION

Photosensitivity occurs in all types of epilepsy rather than in idiopathic generalized epilepsy alone. Surprisingly, there is a tendency for focal epilepsy to be associated with self-sustaining PPRs, especially when no treatment is used. Treatment tends to make the PPR more self-limiting and decrease the SPR. There is a tendency that clinical signs during IPS occur in EEGs in individuals with SEDs.

Electroencephalography in mesial temporal lobe epilepsy: a review

Electroencephalography (EEG) has an important role in the diagnosis and classification of epilepsy. It can provide information for predicting the response to antiseizure drugs and to identify the surgically remediable epilepsies. In temporal lobe epilepsy (TLE) seizures could originate in the medial or lateral neocortical temporal region, and many of these patients are refractory to medical treatment. However, majority of patients have had excellent results after surgery and this often relies on the EEG and magnetic resonance imaging (MRI) data in presurgical evaluation. If the scalp EEG data is insufficient or discordant, invasive EEG recording with placement of intracranial electrodes could identify the seizure focus prior to surgery. This paper highlights the general information regarding the use of EEG in epilepsy, EEG patterns resembling epileptiform discharges, and the interictal, ictal and postictal findings in mesial temporal lobe epilepsy using scalp and intracranial recordings prior to surgery. The utility of the automated seizure detection and computerized mathematical models for increasing yield of non-invasive localization is discussed. This paper also describes the sensitivity, specificity, and predictive value of EEG for seizure recurrence after withdrawal of medications following seizure freedom with medical and surgical therapy.

Neuropsychological characteristics of nonepileptic seizure semiological subgroups

The present study sought to identify neuropsychological characteristics of patients with nonepileptic seizures (NESs) based on seizure semiological subgroups and to make comparisons among NES subgroups and with patients with temporal lobe epilepsy (TLE). A total of 173 patients with NESs and 180 patients with TLE were included in this study. Statistical comparisons were made between a NES four-subgroup model, a NES two-subgroup model, and patients with TLE on neurocognitive measures. A trend toward declining performance was noted across the subjective, catatonic, minor motor, and major motor subgroups, respectively. The nonmotor subgroup showed stronger performance on verbal intelligence, naming, verbal learning, and verbal memory compared with the TLE group. The motor subgroup generally performed equivalently to the patients with TLE. Results indicate that patients with more dramatic seizure semiology appear to have lower neurocognitive functioning at a level comparable to that of patients with TLE. Patients with NESs with the least dramatic semiology appear to have fewer neurocognitive abnormalities.

Is epilepsy a preventable disorder? New evidence from animal models

Epilepsy accounts for 0.5% of the global burden of disease, and primary prevention of epilepsy represents one of the three 2007 NINDS Epilepsy Research Benchmarks. In the past decade, efforts to understand and intervene in the process of epileptogenesis have yielded fruitful preventative strategies in animal models.This article reviews the current understanding of epileptogenesis, introduces the concept of a "critical period" for epileptogenesis, and examines strategies for epilepsy prevention in animal models of both acquired and genetic epilepsies. We discuss specific animal models, which may yield important insights into epilepsy prevention including kindling, poststatus epilepticus, prolonged febrile seizures, traumatic brain injury, hypoxia, the tuberous sclerosis mouse model, and the WAG/Rij rat model of primary generalized epilepsy. Hopefully, further investigation of antiepileptogenesis in animal models will soon enable human therapeutic trials to be initiated, leading to long-term epilepsy prevention and improved patient quality of life.

Electroencephalographic features of temporal lobe epilepsy

Electroencephalography (EEG) is an important tool for diagnosing, lateralizing and localizing temporal lobe seizures. In this paper, we review the EEG characteristics of temporal lobe epilepsy (TLE). Several "non-standard" electrodes may be needed to further evaluate the EEG localization, Ictal EEG recording is a major component of preoperative protocols for surgical consideration. Various ictal rhythms have been described including background attenuation, start-stop-start phenomenon, irregular 2-5 Hz lateralized activity, and 5-10 Hz sinusoidal waves or repetitive epileptiform discharges. The postictal EEG can also provide valuable lateralizing information. Postictal delta can be lateralized in 60% of patients with TLE and is concordant with the side of seizure onset in most patients. When patients are being considered for resective surgery, invasive EEG recordings may be needed. Accurate localization of the seizure onset in these patients is required for successful surgical management.

The dilemma on treatment of the EEG: a justified perspective

Electroencephalography is an important, noninvasive, and useful technique for identifying an epileptogenic region. Electroencephalogram (EEG)-identified interictal epileptiform discharges (IEDs) have been found to correlate well with local metabolic changes in the brain as studied by neuroradiological examinations. In-depth studies on IEDs have revealed not only their multidimensional influence on neural functioning, but also a potential damaging effect on neurons signifying their nonbenign nature. Yet, the issue of treatment of the EEG has remained a topic of intense debate. In this brief article an attempt is made to justify the significance of treatment of the EEG and its impact on the overall prognostic outcome and quality of life of patients with abnormal EEGs.

Significance of the EEG in the decision to initiate antiepileptic treatment in patients with epilepsy: a perspective on recent evidence

The significance of electroencephalography in the prediction of seizure recurrence after a first unprovoked seizure remains a topic of debate. Opinion on the initiation of antiepileptic treatment after a first seizure also remains divided. However, in view of recent evidence, this article is intended to highlight the significance of a properly performed EEG in the decision to initiate antiepileptic drug treatment as early as possible to prevent further morbidity and other consequences.

The Personality Assessment Inventory as a tool for diagnosing psychogenic nonepileptic seizures

Using 184 subjects with valid personality assessment interview (PAI) profiles and video-electroencephalography (VEEG)-confirmed diagnoses of epileptic seizures (ES; n = 109) or psychogenic nonepileptic seizures (PNES; n = 75), we present the diagnostic test performance of the PAI PNES Indicator and other PAI scales when used to differentiate PNES from ES. Subjects with PNES reported significantly higher somatic, conversion, depressed, anxious, and suicidal symptoms. As a diagnostic tool, the PNES Indicator does not add additional accuracy beyond the conversion subscale (SOM-C). The somatization (SOM-S) and physiological depression (DEP-P) subscales perform as well as the SOM-C subscale. The SOM-C scale (cut point > or =70) was 58.7% sensitive and 83.5% specific at diagnosing PNES. Assuming a 30% prevalence of PNES, the SOM-C scale has a positive predictive value (PPV) of 60.4% and negative predictive value (NPV) of 82.5%. Overall, the PAI SOM-C subscale does not appear more accurate than other psychometric tests used to differentiate PNES from ES.

Motor map expansion in the pilocarpine model of temporal lobe epilepsy is dependent on seizure severity and rat strain

Functional alterations in movement representations (motor maps) have been observed in some people with epilepsy and, under experimental control, electrically-kindled seizures in rats also result in persistently larger motor maps. To determine if a single event of status epilepticus and its latent consequences can affect motor map expression, we assessed forelimb motor maps in rats using the pilocarpine model of temporal lobe epilepsy. We examined both pilocarpine-induced seizures, and status epilepticus (SE) in two strains that differ in their propensity for epileptogenesis; Wistar and Long-Evans. Pilocarpine was administered intraperitoneally at dosages that resulted in equivalent proportions of seizures, SE, and survival in both strains. Rats from both strains were given saline injections as a control. Diazepam was administered to all rats to attenuate seizure activity and promote survival. All rats had high-resolution movement representations derived using standard intracortical microstimulation methodologies at 48 h, 1 week, or 3 weeks following treatment. Pilocarpine-induced seizures only gave rise to motor map enlargement in Wistar rats, which also showed interictal spiking, and only at 3 weeks post-treatment indicating altered motor map expression in this strain following a latent or maturational period. Pilocarpine-induced SE yielded larger motor maps at all time points in Wistar rats but only a transient (48 h) map expansion in Long-Evans rats. Our results demonstrate that seizures and SE induced by a convulsant agent alter the functional expression of motor maps that is dependent on seizure severity and a genetic (strain) predisposition to develop epileptiform events.

Distinguishing childhood absence epilepsy patients from controls by the analysis of their background brain electrical activity

Background electroencephalography (EEG), recorded with scalp electrodes, in children with childhood absence epilepsy (CAE) and control individuals has been analyzed. We considered 5 CAE patients, all right-handed females and aged 6-8 years. The 15 control individuals had the same characteristics of the CAE ones, but presented a normal EEG. The EEG was obtained using bipolar connections from a standard 10-20 electrode placement (Fp1, Fp2, F7, F3, Fz, F4, F8, T3, C3, Cz, C4, T4, T5, P3, Pz, P4, T6, O1 and O2). Recordings were undertaken in the resting state with eyes closed. EEG hallmarks of absence seizure activity are widely accepted, but there is a recognition that the bulk of interictal EEG in CAE appears normal to visual inspection. The functional activity between electrodes was evaluated using a wavelet decomposition in conjunction with the Wootters distance. Then, pairs of electrodes with differentiated behavior between CAE and controls were identified using a test statistic-based feature selection technique. This approach identified clear differences between CAE and healthy control background EEG in the frontocentral electrodes, as measured by Principal Component Analysis. The findings of this pilot study can have strong implications in future clinical practice.

Treatment of interictal epileptiform discharges in cerebral palsy patients without clinical epilepsy: hope for a better outcome in prognosis

Cerebral palsy (CP) is a motor disorder due to cerebral damage. It is commonly associated with neuro-psychological retardation and also with epilepsy; hence, its management warrants a multi-dimensional approach. In a significant number of CP patients, interictal epileptiform discharges (IEDs) are obtained in their EEG even in absence of clinical epilepsy. Epileptiform discharge-firing cortical neurons are found to be associated with elevated intracellular Ca(2+) levels and exhibition of abnormal response on exposure to excitotoxic glutamate; both these features have been found to lead to subsequent death of these neurons. This further damage is likely to aggravate the already existing cortical damage in CP patients thereby worsening their prognosis. IEDs are also known to be associated with other neuro-psychological disorders like cognitive impairment and behavioral problems even in absence of clinical epilepsy. Thus, the IEDs cannot be viewed as benign events and their occurrence even in absence of clinical epilepsy cannot be ignored. A few trials aimed at treating IEDs in autistic patients without epilepsy and in children with behavior problems have yielded favorable results. Based on these studies, the author proposes inclusion of EEG investigation in the management protocol of CP patients and treatment of IEDs (when detected even in absence of clinical epilepsy) for a better outcome in their prognosis.

Ongoing epileptiform activity in the post-ischemic hippocampus is associated with a permanent shift of the excitatory-inhibitory synaptic balance in CA3 pyramidal neurons

Ischemic strokes are often associated with late-onset epilepsy, but the underlying mechanisms are poorly understood. In the hippocampus, which is one of the regions most sensitive to ischemic challenge, global ischemia induces a complete loss of CA1 pyramidal neurons, whereas the resistant CA3 pyramidal neurons display a long-term hyperexcitability several months after the insult. The mechanisms of this long-term hyperexcitability remain unknown despite its clinical implication. Using chronic in vivo EEG recordings and in vitro field recordings in slices, we now report spontaneous interictal epileptiform discharges in the CA3 area of the hippocampus from post-ischemic rats several months after the insult. Whole-cell recordings from CA3 pyramidal neurons, revealed a permanent reduction in the frequency of spontaneous and miniature GABAergic IPSCs and a parallel increase in the frequency of spontaneous and miniature glutamatergic postsynaptic currents. Global ischemia also induced a dramatic loss of GABAergic interneurons and terminals together with an increase in glutamatergic terminals in the CA3 area of the hippocampus. Altogether, our results show a morpho-functional reorganization in the CA3 network several months after global ischemia, resulting in a net shift in the excitatory-inhibitory balance toward excitation that may constitute a substrate for the generation of epileptiform discharges in the post-ischemic hippocampus.

Do interictal spikes drive epileptogenesis?

Interictal spikes are periodic, very brief bursts of neuronal activity that are observed in the electroencephalogram of patients with chronic epilepsy. These spikes are useful diagnostically, but we do not know why they are so strongly associated with the spontaneous seizures that characterize chronic epilepsy. Interictal spikes appear before the first spontaneous seizures in animal models of acquired epilepsy, and spikes are sufficient to induce long-term changes in synaptic connections between neurons. Thus, spikes may guide the development of the neuronal circuits that initiate spontaneous seizures. If so, then attempts to prevent or cure epilepsy may best be directed at spikes rather than seizures.

Sensitivity and specificity of procedures for the differential diagnosis of epileptic and non-epileptic seizures: a systematic review

OBJECTIVES

Non-epileptic seizures (NES) present a considerable challenge in clinical practice. This paper reviews published evidence for the reliability of a number of procedures for the differential diagnosis of NES and epilepsy.

METHODS

Papers identified from MEDLINE and PsychInfo Databases (1980-2001) and additional hand searches were independently reviewed using methods for evaluating evidence in systematic reviews [Liddle, J., Williamson, M. Irwig, L. Method for evaluating research guideline evidence. New South Wales Department of Health; 1996 [State Health publication no. (CEB) 96-204]; SIGN. An introduction to SIGN methodology for the development of evidence based clinical guidelines. Scottish Intercollegiate Network; 1999]. Included studies had to have an NES group and a control group of people with epilepsy (each n> or =10), allocated using EEG linked video-recording of concurrent behaviour, and sensitivity and specificity values had to be stated or be calculable.

RESULTS

Thirty-three papers were identified, of which 13 satisfied criteria. Excluded studies are briefly described. Those retained comprised a range of procedures [seizure induction, MMPI assessment, physiological assessment (prolactin, SPECT), pre-ictal pseudosleep, and ictal/post-ictal characteristics]. No procedure emerged with both high sensitivity and specificity and adequately replicated findings, although high levels of specificity were more commonly reported than high levels of sensitivity. This suggests that procedures were generally better at excluding a possible diagnosis.

CONCLUSIONS

No procedure attains reliability equivalent to EEG video-telemetry. Further rigorous evaluation, using standardised and replicable methodologies, is required. The range of symptoms presented in NES suggests that a multi-method approach may be required. This too would require evaluation.

Seizure Recurrence after Planned Discontinuation of Antiepileptic Drugs in Seizure-free Patients after Epilepsy Surgery: A Review of Current Clinical Experience

PURPOSE

Although epilepsy surgery, especially temporal lobe epilepsy surgery, is well established to control seizures in patients remaining on antiepileptic drug (AED) treatment, less information is available about how many seizure-free surgical patients will relapse after discontinuation of AEDs under medical supervision.

METHODS

A literature review yielded six retrospective clinical observations.

RESULTS

After planned discontinuation of AEDs in patients rendered seizure free after epilepsy surgery, most often various forms of temporal lobe surgery, the mean percentage recurrence rate in adults in four studies was 33.8%[95% confidence interval (CI), 32.4-35.2%], with maximum follow-up ranging from 1 to 5 years. Seizure recurrence increased during the follow-up of 1 to 3 years and occurred within 3 years of AED discontinuation. In one study of children with temporal lobe epilepsy, the recurrence rate was 20%. More than 90% of adult patients with seizure recurrence regained seizure control with reinstitution of previous AED therapy. Seizure recurrence was unaffected by the duration of postoperative AED treatment; as a consequence, delaying discontinuation beyond 1 to 2 years of complete postoperative seizure control seems to have no added benefit. The occurrence of rare seizures or auras after surgery did not eliminate the possibility of eventual successful AED discontinuation.

CONCLUSIONS

AED discontinuation is associated with a seizure recurrence in one in three patients rendered seizure free by epilepsy surgery. These results will be useful in counseling patients about discontinuing AED treatment after successful epilepsy surgery.

Transition from interictal to ictal activity in limbic networks in vitro

The transition from brief bursts of synchronous population activity characteristic of interictal epileptiform discharges (IEDs) to more prolonged epochs of population activity characteristic of seizures (ictal-like activity) was recorded in juvenile rat hippocampal-entorhinal cortex slices and hippocampal slices using multiple-site extracellular electrodes. Epileptiform activity was elicited by either increased extracellular potassium or 4-AP. IEDs originated in the CA3 a-b region and spread bidirectionally into CA1 and CA3c dentate gyrus. The transition from IEDs to ictal-like sustained epileptiform activity was reliably preceded by (1) increase in IED propagation velocity, (2) increase in IED secondary afterdischarges and their reverberation between CA3a and CA3c, and (3) shift in the IED initiation area from CA3 a-b to CA3c. Ictal-like sustained network oscillations (10-20 Hz) originated in CA3c and spread to CA1. The pattern of hippocampal ictal-like activity was unaffected by removal of the entorhinal cortex. These findings indicate that interictal and ictal activity can originate in the same neural network, and that the transition from interictal to ictal-like-sustained activity is preceded by predictable alterations in the origin and spread of IEDs. These findings elucidate new targets for investigating the proximate causes, prediction, and treatment of seizures.

Utility of electroencephalography in the evaluation of common neurologic conditions in children

The objective of this study was to assess the utility of electroencephalography (EEG) in the evaluation of common neurologic conditions in children. The EEG recordings of 534 consecutive children (aged < 20 years) were prospectively read by a certified pediatric neurologist. Common diagnostic indications included the following: clinical seizures (33.8%), definite epilepsy (31.2%), attention-deficit hyperactivity disorder (ADHD) (9.1%), headache (8%), syncope (3.5%), learning disabilities (2%), tic disorders (1.4%), and sleep disorders (1.1%). Overall, 63.8% of EEG records were normal, slowing background activity was noted in 6.1%, ADHD was noted in 35.3% (definite epilepsy), and epileptiform activity was noted in 37.1% of the cases of definite epilepsy and 13.2% of the clinically suspected cases. Epileptiform activity was rarely found in the patients without epilepsy. All EEG records of children with syncope (n = 19) and headache (n = 43) were normal. These findings indicate that although EEG plays an important diagnostic role in epilepsy, interictal EEG is being overused during evaluation of various neurologic disorders in children, and a normal EEG is highly predictable in children with nonepileptic conditions.

Convulsant and anticonvulsant effects on spontaneous CA3 population bursts

This paper analyzes the effects of a convulsant and an anticonvulsant manipulation on spontaneous bursts in CA3 pyramidal cells in the in vitro slice preparation under conditions of low (3.3 mM [K(+)](o)) and high (8.5 mM [K(+)](o)) burst probability. When burst probability was low, the anticonvulsant, pentobarbital, produced the anticipated effects: the burst duration decreased and interburst interval increased. However, when burst probability was high, both anticonvulsant and convulsant manipulations decreased the interburst interval and the burst duration. To reconcile these findings, we utilized a model in which CA3 burst duration is limited by activity-dependent depression of CA3 excitatory recurrent collateral synapses and the interburst interval is determined by the time required to recover from this depression. We defined the burst end threshold as the level of synaptic depression at which bursts terminate, and the burst start threshold as the level of synaptic depression at which burst initiation is possible. Synapses were considered to oscillate between these thresholds. When average burst duration and interburst interval data were fit using this model, the paradoxically similar effects of the convulsant and anticonvulsant manipulations could be quantitatively interpreted. The convulsant maneuver decreased both the burst start and end thresholds. The start threshold decreased more than the end threshold, so that the thresholds were closer together. This decreased the time needed to transition from one threshold to the other, i.e., the interburst interval and burst duration. The anticonvulsant manipulation primarily increased the burst end threshold. This also decreased the difference between thresholds, decreasing both interburst interval and burst duration. This model resolves the paradoxical proconvulsant effects of pentobarbital in the CA3 preparation and provides insights into the effects of anticonvulsants on epileptiform discharges in the human EEG.

Assessment of the utility of paediatric electroencephalography

Electroencephalography (EEG) is an important tool in investigating children with neurological disorders, particularly epilepsy. The objectives were to examine the relationship between clinical indications and EEG results, and assess the predictability of a normal result. 438 consecutive paediatric EEGs were included prospectively. One certified electroencephalographer (EEGer) reviewed EEG requisitions and recorded his prediction of a normal result. EEGs were reviewed separately and the relationship between the clinical indications and EEG abnormalities was recorded. The children's mean age was 5 years (SD 4.2). Paediatric neurologists ordered 32% of EEGs. The first EEG was studied in 65% of cases. Overall, 55% of the EEGs were abnormal. Repeat EEGs were twice as likely to be abnormal (95% CI 1.3-3, P= 0.001). Established epilepsy, using antiepileptic drugs, and sleep record, highly correlated with an abnormal result ( P< 0.0001). The EEGer predicted 26% of the EEGs to be normal. A normal EEG was correctly predicted in 97% of non-epileptic paroxysmal events, however, normalization of EEG was correctly predicted in only 54% of children with seizures. EEGs of 15 (3.4%) children with epilepsy revealed unexpected findings that completely changed their management. To conclude, a normal EEG is highly predictable in non-epileptic paroxysmal events. EEGs of children with epilepsy are not predictable and may yield unexpected results.

Computerised audiovisual event recording for infant apnoea and bradycardia

Event recording, by differentiating between true and false events, has advanced the diagnosis and management of infants on home cardiorespiratory monitors; however, the pathogenesis of many events remains obscure. To clarify infant behaviours around the time of apnoea/bradycardia alarms, a computerised audiovisual event recording system (CAVERS) triggered by the apnoea/bradycardia recorder, has been developed. The audiovisual recording can begin up to 3 min before the alarm and can continue for up to 3 min after the alarm. CAVERS information is recorded for a total of 65 events in 13 infants. The CAVERS proves most helpful in documenting infant position and the wide variety of behaviours associated with bradycardic events. These behaviours range from sleep or quiet wakefulness to crying and generalised movements. Post-event activity is also highly variable. Interestingly, 20 of 65 events appear to terminate when the infant wakes to the audible monitor alarm. Nursing intervention is documented for 14 of 42 bradycardic events but only one of 23 apnoeic events. The CAVERS, by elucidating infant behaviours, provides information complementary to that given by cardiorespiratory event recording. It is suggested that infant monitors of the future should incorporate both audiovisual and cardiorespiratory data to elucidate optimally apparent life-threatening events, apnoeas and bradycardias.