Factors affecting interictal spike discharges in adults with epilepsy

Sundaram, M.; Hogan, T.; Hiscock, Merrill; Pillay, Neelan

doi:10.1016/0013-4694(90)90114-y

Cited by 76 publications

(58 citation statements)

References 9 publications

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“…Patients with frequent (one per month) seizures are more likely to have IED than those with rare (one per year) attacks. 4 The timing of EEG recording may be important: investigation within 24 hours of a seizure revealed IED in 51%, compared with 34% who had later EEG. 5 Some patients show discharges mainly in sleep, or there may be circadian variation as in idiopathic generalised epilepsies.…”

Section: Specificity and Sensitivity Of Routine Eeg Cmentioning

confidence: 99%

EEG in the diagnosis, classification, and management of patients with epilepsy

Smith¹

2005

Journal of Neurology, Neurosurgery & Psychiatry

580

433

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T he human electroencephalogram (EEG) was discovered by the German psychiatrist, Hans Berger, in 1929. Its potential applications in epilepsy rapidly became clear, when Gibbs and colleagues in Boston demonstrated 3 per second spike wave discharge in what was then termed petit mal epilepsy. EEG continues to play a central role in diagnosis and management of patients with seizure disorders-in conjunction with the now remarkable variety of other diagnostic techniques developed over the last 30 or so years-because it is a convenient and relatively inexpensive way to demonstrate the physiological manifestations of abnormal cortical excitability that underlie epilepsy.However, the EEG has a number of limitations. Electrical activity recorded by electrodes placed on the scalp or surface of the brain mostly reflects summation of excitatory and inhibitory postsynaptic potentials in apical dendrites of pyramidal neurons in the more superficial layers of the cortex. Quite large areas of cortex-in the order of a few square centimetres-have to be activated synchronously to generate enough potential for changes to be registered at electrodes placed on the scalp. Propagation of electrical activity along physiological pathways or through volume conduction in extracellular spaces may give a misleading impression as to location of the source of the electrical activity. Cortical generators of the many normal and abnormal cortical activities recorded in the EEG are still largely unknown. Spatial sampling in routine scalp EEG is incomplete, as significant amounts of cortex, particularly in basal and mesial areas of the hemispheres, are not covered by standard electrode placement. Temporal sampling is also limited, and the relatively short duration of routine interictal EEG recording is one reason why patients with epilepsy may not show interictal epileptiform discharge (IED) in the first EEG study.If inappropriate questions are asked of the EEG, diagnostic errors will occur, and there will be poor yield of information that could be useful in the management of patients with seizure disorders. It is crucial to recognise that a normal EEG does not exclude epilepsy, as around 10% of patients with epilepsy never show epileptiform discharges. Secondly, an abnormal EEG demonstrating IED does not in itself indicate that an individual has a seizure disorder, as IED are seen in a small percentage of normal subjects who never develop epilepsy, and IED may also be found in patients with neurological disorders which are not complicated by epilepsy. Table 1 lists the areas in epilepsy diagnosis and management for which interictal and ictal EEG are useful, strongly so in some, but in a more limited way in others. SPECIFICITY AND SENSITIVITY OF ROUTINE EEG cEpileptiform activity is specific, but not sensitive, for diagnosis of epilepsy as the cause of a transient loss of consciousness or other paroxysmal event that is clinically likely to be epilepsy. EEG has relatively low sensitivity in epilepsy, ranging between 25-56%. Specificity is better, but...

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Section: Specificity and Sensitivity Of Routine Eeg Cmentioning

confidence: 99%

EEG in the diagnosis, classification, and management of patients with epilepsy

Smith¹

2005

Journal of Neurology, Neurosurgery & Psychiatry

580

433

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“…IED may represent decreased seizure susceptibility (Engel and Ackermann 1980), and may inhibit the expression of seizures (Barbarosie and Avoli 1997;Avoli 2001;de Curtis and Avanzini 2001;Librizzi and de Curtis 2003). Others found that the frequency of IED is the highest some days after the seizures (Sundaram et al 1990) and is primarily influenced by the preceding seizures (Gotman 1984;Gotman and Koffler 1990;Gotman and Marciani 1985).…”

Section: Discussionmentioning

confidence: 96%

Estimating short-run and long-run interaction mechanisms in interictal state

Ozkaya

Korürek

2009

J Comput Neurosci

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We address the issue of analyzing electroencephalogram (EEG) from seizure patients in order to test, model and determine the statistical properties that distinguish between EEG states (interictal, pre-ictal, ictal) by introducing a new class of time series analysis methods. In the present study: firstly, we employ statistical methods to determine the non-stationary behavior of focal interictal epileptiform series within very short time intervals; secondly, for such intervals that are deemed non-stationary we suggest the concept of Autoregressive Integrated Moving Average (ARIMA) process modelling, well known in time series analysis. We finally address the queries of causal relationships between epileptic states and between brain areas during epileptiform activity. We estimate the interaction between different EEG series (channels) in short time intervals by performing Granger-causality analysis and also estimate such interaction in long time intervals by employing Cointegration analysis, both analysis methods are well-known in econometrics. Here we find: first, that the causal relationship between neuronal assemblies can be identified according to the duration and the direction of their possible mutual influences; second, that although the estimated bidirectional causality in short time intervals yields that the neuronal ensembles positively affect each other, in long time intervals neither of them is affected (increasing amplitudes) from this relationship. Moreover, Cointegration analysis of the EEG series enables us to identify whether there is a causal link from the interictal state to ictal state.

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“…IED may represent decreased seizure susceptibility [1], and may inhibit the expression of seizures [4,7,37,40]. Others found that the frequency of IED is the highest some days after the seizures [60] and is primarily influenced by the preceding seizures [18][19][20].…”

Section: Discussionmentioning

confidence: 99%