Electroencephalographic activation with methohexital in an epileptic population

Forty-one epileptics with normal or nonspecific EEG changes were subjected to methohexital and pentylenetetrazol activations (Group I). Fifteen epileptic patients with specific epileptiform discharges were subjected to methohexital activation procedures (Group II). The present study showed that, though it is a safe agent, methohexital is not an effective electroencephalographic activator for the epileptic population. In this study, it activated only 7% of the epileptics with normal records or minimal and nonspecific EEG abnormalities and it activated only 33.3% of epileptics who had previously demonstrated a specific paroxysmal epileptiform discharge in a routine recording.     

Electroencephalographic assessment of patients with epileptic seizures

This article reviews the role of EEG in the diagnosis and management of patients with epilepsies. We review the morphologic and behavioral characteristics of the interictal and ictal EEG markers of the different types of epilepsy that should guide recording strategies to augment its diagnostic yield, and we attempt to delineate those particular features that may be relevant to the main epilepsy syndromes. Particular emphasis is placed on the activation methods, including hyperventilation, sleep deprivation and sleep, and specific triggers, as well as how these may differ between idiopathic and cryptogenic/symptomatic generalized and focal epilepsies, commenting on possible diagnostic pitfalls and areas of uncertainty. We also consider the indications for long-term recordings (video--telemetry and ambulatory) and emphasize the diagnostic value of polygraphic recordings.     

Electroencephalographic patterns in unresponsive pediatric patients

To study the occurrence and incidence of various electroencephalographic patterns, the electroencephalograms of unresponsive pediatric patients admitted to the intensive care unit were analyzed. The interpreters were unaware of the patients' clinical diagnoses. A total of 178 electroencephalographic studies performed on unresponsive patients were analyzed over a period of 3 years. The mean age of the study patients was 7.9 years. Sixty-six patients were less than 1 year old. The following electroencephalographic patterns were observed: 58 patients (33%) manifested electroencephalographic patterns consistent with nonconvulsive status epilepticus. Of the patients with nonconvulsive status epilepticus, 32 patients (18%) had generalized nonconvulsive status epilepticus and 26 patients (14%) manifested partial nonconvulsive status epilepticus. The remaining 120 patients (67%) manifested diffuse cerebral dysfunction, with the majority having severe diffuse cerebral dysfunction. Only 4 patients (2%) had triphasic waves, suggesting a metabolic encephalopathy. Thirty-six percent of the patients under the age of 1 year had electroencephalographic patterns consistent with nonconvulsive status epilepticus. Nonconvulsive status epilepticus is a relatively common electroencephalographic pattern in unresponsive pediatric patients. Metabolic encephalopathy is uncommon in this patient group.     

Electroencephalographic spiking activity, drug levels, and seizure occurrence in epileptic patients

We investigated the relationships among the electroencephalographic spiking rate, drug levels, and seizure occurrence in 44 patients with focal epilepsy. Seizure occurrence was continuously monitored by personnel or videorecording and spiking rate was quantified by an automatic detection method. Results indicate that drug levels do not influence spiking rate, and spiking rate does not change before seizures but increases markedly after them, particularly secondarily generalized seizures. This increase can last several days and is observed during wakefulness and sleep. High or low spiking rates do not influence the occurrence of seizures. We suggest that interictal spikes may passively reflect damage to the brain, a damage which is worsened by further seizures. Spikes may not be directly related to seizure generation.     

Epilepsy and electroencephalographic anomalies in chromosome 2 aberrations. A review

Epilepsy and electroencephalographic (EEG) anomalies are common in subjects carrying chromosomal aberrations. We report clinical and EEG investigations on 13 patients carrying chromosome 2 anomalies, including two patients with inversions, six with translocations, two with partial duplications and three with interstitial deletion syndromes. Epilepsy and/or EEG anomalies were found in one patient with a chromosome 2 translocation, in both of those carrying partial duplications and in all three with interstitial deletion syndromes. No epilepsy or EEG anomalies were detected in the remaining patients. CONCLUSIONS: Epilepsy may be associated with chromosome 2 aberrations. Gross rearrangements involving the long arm of chromosome 2 might be more often associated with epilepsy than those involving the short arm. The association of epilepsy with chromosome 2 duplications is less clear. In particular, our observations and a review of the literature appear to suggest that a strict relationship between epilepsy and interstitial deletions involving the 2q24-q31 region. In the latter disorder tonic and focal seizures occur early in life. Generalized and focal myoclonic jerks tend to appear in infancy and are subsequently followed by seizures mixed in type. Seizures usually persist up to late childhood and are drug resistant. Further studies are necessary to better define the electroclinical patterns of patients carrying deletions in 2q24-q31. These may help to direct systematic study of this--probably underestimated--cause of severe epilepsy.     

X chromosome inactivation patterns in brain in Rett syndrome: implications for the disease phenotype

Skewed X chromosome inactivation (XCI) has been implicated in modulating the severity of Rett syndrome (RTT), although studies by different groups have yielded conflicting results. In this study we have characterised the XCI pattern in various neuroanatomical regions of nine RTT brains and non-neural tissue in two of these patients to determine whether or not variable XCI patterns occur in different brain regions or somatic tissues of the same patient. The mean XCI patterns for frontal and occipital cortex were compared between RTT and control subjects, and showed no significant differences when comparing RTT frontal to control frontal cortex or RTT occipital to control occipital cortex. However, one RTT subject displayed variability across the different neuroanatomical regions of the brain and skewing in some non-neural tissues. This observation adds another dimension to the epigenetic factors that may contribute to the phenotype in RTT. It also mandates that caution should be exercised in factoring XCI, including assumptions based on the blood XCI pattern, into the development of phenotype-genotype correlations.