Armin Mohamed

Temporal lobe epilepsy due to hippocampal sclerosis in pediatric candidates for epilepsy surgery

Objective: To characterize the clinical, EEG, MRI, and histopathologic features and explore seizure outcome in pediatric candidates for epilepsy surgery who have temporal lobe epilepsy (TLE) caused by hippocampal sclerosis (HS). Methods: The authors studied 17 children (4 to 12 years of age) and 17 adolescents (13 to 20 years of age) who had anteromesial temporal resection between 1990 and 1998. Results: All patients had seizures characterized by decreased awareness and responsiveness. Automatisms were typically mild to moderate in children and moderate to marked in adolescents. Among adolescents, interictal spikes were almost exclusively unilateral anterior temporal, as opposed to children in whom anterior temporal spikes were associated with mid/posterior temporal, bilateral temporal, extratemporal, or generalized spikes in 60% of cases. MRI showed hippocampal sclerosis on the side of EEG seizure onset in all patients. Fifty-four percent of children and 56% of adolescents had significant asymmetry of total hippocampal volumes, whereas the remaining patients had only focal atrophy of the hippocampal head or body. Subtle MRI abnormalities of ipsilateral temporal neocortex were seen in all children and 60% of adolescents studied with FLAIR images. On histopathology, there was an unexpectedly high frequency of dual pathology with mild to moderate cortical dysplasia as well as HS, seen in 79% of children and adolescents. Seventy-eight percent of patients were free of seizures at follow-up (mean, 2.6 years). A tendency for lower seizure-free outcome was observed in patients with bilateral temporal interictal sharp waves or bilateral HS on MRI. The presence of dual pathology did not portend poor postsurgical outcome. Conclusions: TLE caused by HS similar to those in adults were seen in children as young as 4 years of age. Focal hippocampal atrophy seen on MRI often was not reflected in total hippocampal volumetry. Children may have an especially high frequency of dual pathology, with mild to moderate cortical dysplasia as well as HS, and MRI usually, but not always, predicts this finding. Postsurgical seizure outcome is similar to that in adult series.

Epileptogenicity Correlated with Increased N‐Methyl‐d‐Aspartate Receptor Subunit NR2A/B in Human Focal Cortical Dysplasia

Summary: Purpose: Human cortical dysplasia (CD) is a frequent cause of medically intractable focal epilepsy. The neurotransmitter mechanisms of epileptogenicity in these lesions have been attributed to changes in various glutamate receptor subtypes. Increased N‐methyl‐d‐aspartate (NMDA) receptor (NR) 2A/B coassembled with NRI subunits has been shown in focal epileptic CD. The purpose of this study is to correlate in situ CD epileptogenicity and the expression of various glutamate receptor subtypes.

A new EEG recording system for passive dry electrodes

OBJECTIVE We present a new, low power EEG recording system with an ultra-high input impedance that enables the use of long-lasting, passive dry electrodes. It incorporates Bluetooth wireless connectivity and is designed to be suitable for long-term monitoring during daily activities. METHODS The new EEG system is compared to a standard and clinically available reference EEG system using wet electrodes in three separate sets of experiments. In the first two experiments, each dry electrode was surrounded by four standard wet electrodes and the alpha and mu-rhythms were recorded. In the third experiment, serial monopolar (referred to the left ear) recordings of flash visual evoked potential were performed using the new EEG system and a reference system. RESULTS These experiments showed that the signal recorded using the new EEG system is almost identical to that recorded with standard clinical EEG equipment; our measurements showed that the correlation coefficient between the dry electrode recordings and the average of the four standard electrodes surrounding each dry electrode is greater than 0.85. CONCLUSION We conclude that the new EEG system performs similarly to reference EEG systems, while providing the advantages of portability, ease of application and minimal scalp preparation. SIGNIFICANCE The proposed system using passive dry electrodes suitable for single use while performing as good as standard EEG equipment provides ease of application and minimal scalp preparation.

Postictal Diffusion-Weighted Imaging for the Localization of Focal Epileptic Areas in Temporal Lobe Epilepsy

Summary:  Purpose: Diffusion‐weighted MR imaging (DWI) is a novel technique to delineate focal areas of cytotoxic edema of various etiologies. We hypothesized that DWI may also detect the epileptogenic region and adjacent areas during the ictal and early postictal periods in patients with temporal lobe epilepsy (TLE).

Interictal Epileptiform Discharges in Temporal Lobe Epilepsy Due to Hippocampal Sclerosis Versus Medial Temporal Lobe Tumors

Summary: Purpose: It remains controversial whether a specific pattern of interictal epileptiform activity exists that may help to differentiate temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS) from other forms of TLE. In this study, we characterized the distribution of interictal epileptiform discharges in TLE due to HS as compared with those in patients with tumors restricted to the medial temporal lobe structures.

Periictal diffusion-weighted imaging in a case of lesional epilepsy.

Summary: Purpose: Diffusion‐weighted MR imaging (DWI) has been used for the early diagnosis of acute ischemic lesions in humans and in animal models of focal status epilepticus. We hypothesized that DWI may be a sensitive, noninvasive tool for the localization of the epileptogenic area during the periictal period.

The topography and significance of extratemporal hypometabolism in refractory mesial temporal lobe epilepsy examined by FDG‐PET

Purpose:  This study aims to map the temporal and extratemporal 18‐fluorodeoxyglucose positron emission tomography (FDG‐PET)–defined hypometabolism in mesial temporal lobe epilepsy (MTLE). We hypothesize that quantitative analysis will reveal extensive extratemporal glucose hypometabolism (EH), that the EH is related to seizure propagation beyond the temporal lobe, hypometabolism restricted to one temporal lobe predicts a good outcome following surgery, and EH predicts a poor outcome.

Examining factors related to accelerated long-term forgetting in epilepsy using ambulatory EEG monitoring

Some patients with epilepsy demonstrate normal memory when this is tested at relatively short intervals (e.g., 30 min), but substantial loss over longer delay periods (e.g., days or weeks) when compared to healthy control subjects. This pattern of “accelerated long‐term forgetting” (ALF) affects the everyday lives of patients, yet goes undetected by standard neuropsychological memory tests, and its pathophysiologic basis is poorly understood. By testing memory over a period of concurrent ambulatory electroencephalography (EEG), the current study aimed to investigate possible factors contributing to ALF.

The utility of prolonged outpatient ambulatory EEG

PURPOSE ILAE guidelines recommend the use of prolonged EEG where the diagnosis of epilepsy or the classification of the seizure syndrome is proving difficult. Due to its limited provision, video EEG monitoring is unavailable to many patients under investigation(1). The aim of this study was to examine the utility of the alternate investigation of outpatient ambulatory EEG. METHODS In this retrospective study we analysed 324 consecutive prolonged outpatient ambulatory EEGs lasting 72-96 h (4-5 days), without medication withdrawal. EEG data and the clinical record were reviewed to investigate the utility of the investigation. RESULTS Of 324 studies: 219 (68%) studies gave positive data, 116 (36%) showed interictal epileptiform discharges (IEDs), 167 (52%) had events. 105 (32%) studies were normal. Overall 51% of studies changed management of which 22% of studies changed the diagnosis and 29% of studies refined the diagnosis by classifying the epilepsy into focal or generalised. CONCLUSION The present study confirms the diagnostic utility of outpatient ambulatory EEG in the diagnosis of paroxysmal events.

Rates of DSM-IV mood, anxiety disorders, and suicidality in Australian adult epilepsy outpatients: A comparison of well-controlled versus refractory epilepsy

Despite recent research into the impact of seizure control on mood disorders in epilepsy, it is often assumed that rates of psychiatric disorders are higher in people with refractory rather than well-controlled epilepsy. We assessed the point prevalence of mood and anxiety disorders and suicide risk using the Mini International Neuropsychiatric Interview (MINI) in a consecutive sample of epilepsy outpatients from a tertiary referral center. One hundred and thirty patients, whose epilepsy was categorized as well-controlled versus drug-treatment-refractory epilepsy (69; 53% well-controlled epilepsy) were recruited. High rates of mood disorders (n = 34; 26%), anxiety disorders (n = 37; 29%) and suicide risk (n = 43; 33%) were found. However, there was no difference in rates of disorders or suicide risk for those with refractory versus well-controlled epilepsy. These results underscore the importance of assessment and management of psychopathology in all people with epilepsy, regardless of their seizure control.