Incidence of spikes and paroxysmal rhythmic events in overnight ambulatory computer-assisted EEGs of normal subjects: a multicenter study

The borderland of migraine and epilepsy in children

OBJECTIVE

To provide a review on the spectrum of migraine-epilepsy disorders in children.

BACKGROUND

The migraine-epilepsy continuum covers a fascinating array of disorders that share many clinical similarities but also differ fundamentally in pathophysiology. In the pediatric population, its study can be complicated by the young age of those affected and the lack of clear understanding of the neurobiology of these disorders within the developing brain.

DISCUSSION

This review serves to discuss the borderland of migraine and epilepsy in children. It will focus on epidemiology and comorbidity of the two disorders, possible mechanisms for shared pathophysiology informed by basic and translational science, and an overview of clinical similarities and differences. It will also discuss differentiation of migraine aura from childhood occipital epilepsies. Finally, the review concludes with a discussion of current classification methods for capturing cases on the migraine-epilepsy spectrum and a call for a united approach towards a better definition of this spectrum of disorders.

CONCLUSION

Recent advances examining the migraine-epilepsy spectrum show clinicopathological similarities between the two disorders in children. Epidemiology demonstrates reciprocally increased incidences of epilepsy in migraineurs and of migraines in children with epilepsy, however, prospective longitudinal in children are currently lacking. Clinically, the two disorders show similarity in preictal, ictal, and postictal phenomena, with close temporal association of the two conditions described by the controversial term of "migralepsy." Basic science research has contributed significant improvements in understanding the generation of both of these episodic neurological conditions, with common links seen at a cellular level involving synaptic glutamate release and the provocation of varying propagation methods including cortical spreading depression in migraine and the paroxysmal depolarizing shift in epilepsy. Despite these significant gains in understanding, improved classification methods are required to identify and further study these interrelated conditions and move towards improved diagnosis and treatment of disorders on the migraine-epilepsy continuum in children.

Electroencephalogram variations in pediatric migraines and tension-type headaches

This study evaluates specific electroencephalogram abnormalities in pediatric migraine and tension-type headaches, and demonstrates the clinical value of these abnormalities. We studied 50 migraine patients and 50 tension-type headache patients. Their mean age ± SD was 10.62 ± 3.21 (range, 5-16) years in the migraine group, and 13.00 ± 2.37 (7-16) years in the tension-type headache group. Diagnoses were rendered according to the International Classification of Headache Disorders, 2nd Edition, First Revision, of the International Headache Society. All patients underwent two waking-state electroencephalograms, one during a headache, and the other when headache-free. Thirty-six percent (18/50) of migraine patients and 12% (6/50) of tension-type headache patients revealed specific electroencephalogram abnormalities in headache attack electroencephalograms (P < 0.05). In headache-free period electroencephalograms, 16% (8/50) of the migraine group and 2% (1/50) of the tension-type headache group revealed abnormalities (P < 0.05). Our results indicate that electroencephalogram abnormalities are particularly prevalent in migraines, especially during headache attacks. This study is the first, to the best of our knowledge, on electroencephalographic evaluation of pediatric migraine and tension-type headache patients during both headache attacks and headache-free periods.

Migraine detection through spontaneous EEG analysis

Spontaneous EEG patterns are studied to detect migraine patients both during the attack and in headache-free periods. The EEG signals are analyzed through the wavelets and both scale-dependent and scale-independent features are computed to characterize the patterns. The classification is carried out by a supervised neural network. The efficiency of the method is evaluated through the Receiver Operating Characteristic (ROC) analysis and the Wilcoxon-Mann-Whitney (WMW) test. Although a high discrimination is observed with one single neural output, a complete separation among MwA patients and healthy subjects is obtained when a scatter plot is drawn in the plane of two suitable neural outputs.

An audit of electroencephalography requests: Use and misuse

OBJECTIVE

To investigate whether electroencephalogram (EEG) requests at St George's Hospital (SGH) are being made according to clinical guideline recommendations.

METHODS

A retrospective audit at a regional neurology and neurosurgery referral centre, also serving a district population. All adult National Health Service patients undergoing standard EEG between 1st November 2003 and 31st January 2004, for whom the request originated within the hospital, were identified. Data was collected from each subject's case notes, request form and EEG report and compared to predetermined criteria.

RESULTS

Fifty sets of notes from ninety patients meeting the inclusion criteria were available for review. Twenty-six percent of requests were considered 'inappropriate', with respect to clinical guidelines, of which 92% were for 'funny turns' where there appeared to be insufficient clinical evidence to justify the request. The EEG contributed to diagnosis or management in only 22% of cases, all of which had been appropriately requested. Neurologists/epileptologists appeared better than non-specialists in terms of appropriateness of referrals, though the numbers were too small to reach significance (p = 0.173, Fisher's exact). Forty-two percent of all patients, and less than 10% of outpatients, had their EEG within the guideline target wait of 4 weeks.

CONCLUSIONS

Over a quarter of EEG referrals are not being made in accordance with guidelines, mainly because of the misconception that an EEG can confirm or exclude a diagnosis of epilepsy in patients with "funny turns". In addition, less than 10% of out patient requests are being met within 4 weeks. Strategies to maximise service utilisation are discussed.

The electroencephalogram as a screening tool in pilot applicants

The electroencephalogram (EEG) is used to screen pilot candidates for professional licensure irrespective of medical history in many European countries; applicants with paroxysmal abnormalities are excluded. The aim is to reduce the risk of later seizures in flight, which may cause accident or death, but there is no clear evidence that EEG screening can lead to any significant risk reduction. This is partly due to the low predictive value of the EEG, the low risk of seizure in healthy young adults, and the low risk of commercial aircraft accidents. Later-onset seizures, unrelated to the results of earlier screening, cannot be predicted or prevented by screening. Some benefit cannot be excluded, but may be difficult to demonstrate in prospective studies. Specialized screening of targeted populations, such as for photosensitivity in helicopter pilot candidates, may be justifiable; prospective studies with standardized recording and interpretation protocols are needed to assess this.

Electroencephalography in migraine: a review with focus on quantitative electroencephalography and the migraine vs. epilepsy relationship

EEG-studies in migraine in the last decade has contributed modestly to the understanding of headache pathogenesis. Headache patient groups seem to have increased EEG responses to photic stimulation, but a useful biological marker for migraine in single patients has not been found. In future EEG and QEEG studies we recommend to use follow-up designs and record several EEGs across the migraine cycle. It is also important to use a blinded study design in order to avoid selection bias. A clinical EEG should be performed in patients with acute headache attacks when either epilepsy, basilar migraine, migraine with prolonged aura or alternating hemiplegia is suspected. Unequivocal epileptiform abnormalities usually suggest a diagnosis of epilepsy. In children with occipital spike-wave activity the probable diagnosis is childhood epilepsy with occipital paroxysms (CEOP). The final diagnosis of either an epilepsy syndrome or migraine must be mainly based on a clinical judgement [corrected].

New horizons in ambulatory electroencephalography

Since its inception 30 years ago, AEEG has continued to evolve--from four-channel tape recorders to 32-channel digital recorders with sophisticated automatic spike and seizure detection algorithms. AEEG remains an important tool in epilepsy evaluation. In the near future, smaller, faster, and more sophisticated AEEGs will be developed. Seizure detection/anticipation systems will allow the wearer to be forewarned of a seizure so that appropriate safety measures can be taken. With further refinement in our understanding of nonlinear dynamic analysis to define the pre-ictal state, AEEG will be coupled with an accurate seizure anticipation device in a closed-loop system, providing a time window during which therapeutic intervention can occur, to prevent a seizure. The therapeutic intervention will most likely involve vagus nerve or deep brain stimulation. An alternative is that the patient may learn to recognize early symptoms of the pre-ictal state and use behavioral biofeedback interventions to avoid a clinical seizure. In order to achieve convenient ambulatory recording and seizure detection that could realistically improve the lives of patients with refractory epilepsy, the process of miniaturization of such a device to a convenient size must be accomplished. One of the aspects of epilepsy that patients find most frustrating, and that most limits activities, is the vulnerability to sudden unexpected incapacitation due to the occurrence of a seizure. With miniaturization of AEEG and seizure anticipation technology, and advancements in our ability to identify the transition from pre-ictal to ictal state, there is realistic hope that patients with refractory epilepsy may gain control over their seizures and enjoy significantly improved quality of life.

Long-term EEG monitoring: a clinical approach to electrophysiology

Long-term electroencephalographic monitoring (LTM) is the capability of recording the EEG over long periods of time and not a specific duration. Prolonged EEG recording is used primarily for epilepsy monitoring, but LTM is also used in the intensive care unit, the operating room, and in the emergency department. The purpose of LTM is to expand the limited time sampling associated with shorter "routine" EEG recording. Audiovisual monitoring may also be used in conjunction with LTM to evaluate simultaneously a specific clinical behavior that may or may not be associated with EEG alteration. This is typically performed in a hospital setting for safety and ancillary testing purposes. LTM is used most frequently in the diagnosis and management of seizures and "spells," but has also gained wider application in the evaluation of sleep disorders, cerebrovascular disease, psychiatric conditions, and movement disorders. Computer-assisted LTM systems that process, analyze, compress, and store data digitally have become widely available in clinical practice both in the hospital as well as outside the hospital when the patient is ambulatory.