Temporal ictal electroencephalographic frequency correlates with hippocampal atrophy and sclerosis

Abstract

We studied 328 complex partial seizures (CPS) in 63 consecutive patients with temporal lobe epilepsy who underwent scalp electroencephalography/video monitoring, magnetic resonance imaging (MRI), and surgery. The initial ictal discharge (IID), defined as the first sustained electrical seizure pattern localized to the surgical site, was determined. If the IID was rhythmic waves, the median frequency was measured. To determine if IID frequency correlates with hippocampal atrophy (HA) or sclerosis (HS), hippocampal volume ratios (HVRs) were measured (n = 52) or assessed visually (n = 11) on MRI, and mesial temporal histopathology specimens (n = 22) were graded for HS. Sixteen patients (25%) had no or mild HA (HVR = 0.78-1.02), and 47 patients (75%) had moderate-to-marked unilateral (HVR = 0.33-0.76), or bilateral, HA. Theta frequency IIDs were significantly more commonly associated with moderate-to-marked HA than were delta IIDs. Theta frequency IIDs occurred in 19% of patients with mild or no HA, and 79% of patients with moderate-to-marked HA; delta IIDs occurred in 63% of patients with little to no HA, and 13% of those with moderate-to-marked HA. In addition, the median IID frequency inversely correlated with HVR and directly correlated with HS severity. In conclusion, faster frequency rhythmic IIDs during temporal lobe CPS correlate with greater degrees of ipsilateral HA on MRI, and higher grades of HS.

MR-based in vivo hippocampal volumetrics: 2. Findings in neuropsychiatric disorders

“…[22][23][24][25][26][27][28][29][30][31] These methods are superior to visual inspection of MR images. 32 Hippocampal volumetric analysis with MRI is not always able to detect hippocampal sclerosis accurately, 33 however, in those cases the additional analysis of entorhinal cortex volume or volume ratio analysis may be able to provide accurate lateralization of seizure focus (see Bernasconi et al 34 and Vossler et al, 35 respectively). These methods have demonstrated considerable efficacy, especially with the addition of T2 relaxation time data.…”

Experimental Neonatal Status Epilepticus and the Development of Temporal Lobe Epilepsy with Unilateral Hippocampal Sclerosis

“…1,4 Hippocampal sclerosis is implicated as the cause of seizures and also associated cognitive deficits and seizure intractability, in patients with TLE. 3,[5][6][7][8] Hippocampal sclerosis is less common in children than adults with TLE, but may nevertheless be present in up to half or more patients. 9 -11 Pathology and neuroimaging studies have suggested seizures in children are the precipitant of hippocampal sclerosis, and hippocampal sclerosis the cause of TLE.…”

EEG Patterns in Persons Exposed to Ionizing Radiation as a Result of the Chernobyl Accident. Part 2: Quantitative EEG Analysis in Patients Who Had Acute Radiation Sickness

“…22 Consequently, doserelated reduction of h-activity in the left temporal region could be explained as cortical and limbic, particularly, hippocampal damage. [23][24][25][26][27] Dose-related diffusive depression of ␣-power in the EEG PATTERNS AND IONIZING RADIATION frame of current neurophysiological theories could be outlined as 1) thalamic, 2) thalamocortical, 3) cortical, 4) hippocampal and/or 5) diffusive brain damage. 28 Diffusive reduction of b-power in confirmed ARS patients could be explained as dysfunction (inhibition) of corticocortical and thalamocortical transactions 19 and decreased thalamic and nucleus caudate input on cortex.…”