Temporal Intermittent Rhythmic Delta Activity (TIRDA) in the Diagnosis of Complex Partial Epilepsy: Sensitivity, Specificity and Predictive Value

Abstract

Temporal interictal rhythmic delta activity or TIRDA was found in 45 of the 127 recordings of patients with complex partial epilepsy (CPE) referred for both awake and sleep E E C TIRDA was more abundant during drowsiness and light sleep; it occurred more characteristically as trains of 50-100 ^.v sinusoidal or saw-toothed l-4Hz activity, recorded predominantly from anterior temporal regions. When occurring bilaterally and independently, TIRDA varied from side to side. TIRDA is often found in association with anterior temporal spikes or sharp waves (TS) particularly during sleep, as observed in 43 out of 45 EEGs. TIRDA can nevertheless occur as an isolated abnormality, as noted in two sleep and 12 awake study recordings. Because of its high specificity and positive predictive value over a large range of prevalence, TIRDA should be singled out as an accurate interictal indicator of CPE. In patients with isolated TIRDA, the cost of prolonged EEG recording during sleep for the purpose of activating TS has to be weighed against the yield of eventually confirming the obvious. RESUME: TIRDA ou activite rythmique temporale inter-critique dans le diagnostic de I'epilepsie partielle complexe: sensibilite, specificite et valeur predictive Chez 35 % des malades adresses pour investigation d'une epilepsie partielle complexe, l'electroencephalogramme a revele en temporal une activite delta rythmique inter-critique (TIRDA). Plus abondant durant somnolence et sommeil leger, le TIRDA se presente plus classiquement sous forme de train d'ondes de 1 a 4Hz, d'une amplitude allant de 50 a 100 |J.v. Lorsque bilateral, le TIRDA survient de facon asynchrone et avec une morphologie distincte de chaque cote. Souvent associe a des pointes temporales anterieures (TS), le TIRDA peut se retrouver n6anmoins de facon isolee. A cause de sa tres grande specificite et de sa valeur predictive elevee pour un large spectre de prevalence, le TIRDA merite d'etre retenu comme un indicateur intercritique pathognomonique de I'epilepsie partielle complexe. Les inconvenients d'un enregistrement prolonge pendant le sommeil, a la recherche de la pointe temporale classique, meritent d'etre souspeses lorsque le TIRDA represente la seule anomalie recueillie lors d'un electroencephalogramme initial.

Non-epileptiform EEG abnormalities: an overview

“…When it is due to a focal lesion and presented as bilateral and symmetric, this lesion classically is near the third ventricle, diencephalic or mesencephalic midline, brainsteim or cerebellum 15,26 . Intermittent rhythmic delta activity occurring well localized over the temporal region (temporal intermittent rhythmic delta acitivity -TIRDA) is indicative of potential epileptogenicity of the ipsilateral temporal lobe 8,29 . It was first described by Reiher et al 8 , in 1989, and it was defined as short bursts or trains of 3 seconds or more of repetitive, rhythmic, saw-toothed or sinusoidal 1.0 to 4.0 Hz activity of 50-100 µV in amplitude, predominantly over the anterior temporal region 8,24,29 .…”

“…Intermittent rhythmic delta activity occurring well localized over the temporal region (temporal intermittent rhythmic delta acitivity -TIRDA) is indicative of potential epileptogenicity of the ipsilateral temporal lobe 8,29 . It was first described by Reiher et al 8 , in 1989, and it was defined as short bursts or trains of 3 seconds or more of repetitive, rhythmic, saw-toothed or sinusoidal 1.0 to 4.0 Hz activity of 50-100 µV in amplitude, predominantly over the anterior temporal region 8,24,29 . It has a strong association with hippocampal atrophy and mesial temporal sclerosis in patients with temporal lobe epilepsy, but may infrequently occur in extratemporal epilepsy 6 .…”

“…Its encounter in these patients has the same meaning of interictal epileptiform activity, particularly during sleep, although it is not classified as an epileptiform activity 13,24 . Sometimes, interictal epileptiform activity and TIRDA can coexist in the same patient 8 . Gennaro et al 29 studied 129 patients affected by drug-resistant partial epilepsy and found in 52 (40.3%) significant correlations between TIRDA and mesial and mesio-lateral temporal lobe epilepsy, mesial temporal sclerosis, interictal epileptiform discharge localized over the anterior temporal regions and 5.0 to 9.0 Hz temporal ictal discharges.…”

“…The EEG provides valuable information on the investigation of patients with signs of acute cerebral suffering, rapidly progressive dementia, toxicmetabolic encephalopathy, coma and brain death, among others [2][3][4] . It is worth remembering that the non-epileptiform EEG abnormalities may be present in patients with epilepsy [5][6][7][8][9] . Vanrumste et al 5 demonstrated the presence of non-epileptiform activity arising from the same area as epileptiform activity in five children with focal epilepsy, using an automated technique.…”

Slow Oscillations (≤1 Hz) Mediated by GABAergic Interneuronal Networks in Rat Hippocampus

“…Overall, fast rhythms of Ն15 Hz occur in arousal or active states, whereas slow oscillations of Յ1-4 Hz dominate during deep sleep (Niedermeyer, 1993;Steriade, 1993) or some epileptiform activities (Reiher et al, 1989;Gambardella et al, 1995;Normand et al, 1995). Alterations in these oscillations are associated with or result from substantial changes in brain structure and f unction, and detection of these abnormalities by electroencephalography (EEG) is a widely used diagnostic approach in clinical practice.…”