Planned ictal FDG PET imaging for localization of extratemporal epileptic foci.

PURPOSE: This work demonstrates the feasibility of planned ictal positron emission tomography (PET) with [18F]fluoro-2-deoxy-glucose (FDG) for localization of epileptic activity in patients with frequent partial seizures of extratemporal origin. METHODS: Ictal PET imaging was performed in four patients (two men and two women, ages 28-61) with continuous or very frequent (every 3-15 min) partial seizures. All patients had abnormalities apparent on magnetic resonance (MR) or computed tomographic (CT) imaging, two with extensive brain lesions that precluded precise localization of the seizure focus with interictal PET or single-photon emission tomography (SPECT) imaging. RESULTS: Ictal PET imaging demonstrated a restricted area of focal hypermetabolism concordant with surface electroencephalographic (EEG) recording in all cases. The PET images were registered to MR imaging data for further anatomic localization of hypermetabolic regions in three cases. The ictal PET data were used to guide neurosurgical intervention in one case. CONCLUSIONS: We conclude that planned ictal PET imaging may be a useful and potentially superior approach to ictal SPECT for identifying the epileptic focus in a selected group of patients with continuous or frequent simple partial seizures.

Technical advantages of digital EEG.

Digital EEG (DEEG) is the paperless recording of an EEG using computer-based instrumentation. The data are stored on electronic media, such as magnetic drives or optical disks, and displayed on a monitor. DEEG has many advantages compared to analog EEG including automatic event detection, storage, quantification, and networking capabilities. The flexibility of DEEG allows for changes of recording parameters, such as montage, filters, and horizontal and vertical display scales retrospectively during record review. In this review numerous clinical EEG examples are used to demonstrate how these post hoc changes, particularly reformatting the montage, allow for more accurate interpretation of the EEG.

Cross-country digital EEG survey 1998.

A survey of digital EEG (DEEG) in clinical practice was recently completed by electroencephalographers in North America. Most had used DEEG for 3 or more years. They clearly preferred digital to analog EEG. The cost of operating DEEG was lower, and DEEG laboratories were more efficient. Reformatting was considered the best single feature of DEEG. However, problems continued to be encountered with equipment, service, and networking.

Electrographic tachyphylaxis to etomidate and ketamine used for refractory status epilepticus controlled with isoflurane.

Etomidate and ketamine controlled seizures but acute tachyphylaxis occurred. Isoflurane was then used to control seizures.

EEG spectral abnormalities and psychosis as predictors of cognitive and functional decline in probable Alzheimer's disease.

We examined whether either psychotic features (e.g., delusions and hallucinations) or EEG abnormalities are associated with more rapid progression of Alzheimer's disease (AD). AD patients with psychosis have exhibited more EEG abnormalities than those without psychosis, and both abnormal EEG and psychosis have been noted to be predictors of functional and cognitive decline in AD. Ninety-five probable AD patients participating in a longitudinal study of dementia had an EEG and a semistructured psychiatric interview at baseline. Using EEG spectral analysis, we classified records as normal/abnormal based on the parasagittal mean frequency. Patients with abnormal EEGs were more functionally (e.g., Blessed Rating Scale for activities of daily living) and cognitively (e.g., Mini-Mental State) impaired than patients with normal EEG. AD patients with psychosis were only more functionally impaired than patients without psychosis. A two-factor analysis showed no interaction between abnormal EEG and psychosis. In addition, using a Cox proportional hazard model adjusted for age and education, the presence of an abnormal EEG or psychotic symptom at study entry was associated with higher risk of reaching severe cognitive and functional impairment during follow-up. Neither abnormal EEG nor the presence of psychosis predicted death. These results indicate that both abnormal EEG and psychosis are independent predictors of disease progression but not of physical survival.

Electroencephalography in syncope.

Electroencephalographic (EEG) findings in syncope are reviewed. There are four major categories of syncope: neurally mediated (neurocardiogenic), neurologic, decreased cardiac output, and orthostatic hypotension. However, regardless of cause, whether the syncope is due to a vasovagal effect, a cardiac arrhythmia, an epileptic seizure, or hypotension, EEG findings are similar and reflect cerebral hypoperfusion. Initially there may be a slowing of background rhythms. This is followed by high amplitude delta activity, maximal anteriorly. If the hypoperfusion persists there is subsequent flattening of the EEG. The EEG returns to normal in the reverse sequence. In cases with severe and prolonged ischemia, convulsive syncope may occur at the time of the EEG flattening. Although not an epileptic phenomena, clinically this is often mistaken for epilepsy. Conversely, epileptic disorders, such as the ictal bradycardia syndrome, may occasionally mimic syncope. Therefore, in patients in whom EEGs are performed for the evaluation of an episode of loss of consciousness, simultaneous ECG should be used.

Stimulus-sensitive seizures in postanoxic coma.

PURPOSE: To describe four patients with stimulus-sensitive seizures and myoclonus following severe hypoxic-ischemic injury. METHODS: In 22 months, four adult patients with myoclonus, generalized tonic-clonic, and clonic seizures following tactile stimulation were identified. EEG and hospital records were reviewed. RESULTS: EEGs showed bursts of generalized spike and polyspike activity following tactile stimulation associated with the clinical seizures. No cerebral activity was present between the epileptiform bursts. At times, prolonged periods of suppression were recorded. All patients failed to respond to antiepileptic drugs and died. CONCLUSIONS: Stimulus-sensitive seizures and myoclonus following anoxia are associated with poor clinical outcome. The presence of seizures and myoclonus in conjunction with epileptiform discharges on EEG confirms that post-anoxic myoclonus is an epileptic state.

Triphasic waves in a psychiatric population: a retrospective study.

In a retrospective study of 15.326 EEGs performed from 1983 to 1992 in a psychiatric institute, 83 EEGs (62 patients-13 men and 49 women ranging in age from 59 to 90 years, with a mean age of 74 years) had triphasic waves (TWs). All 62 patients were awake, though they were often confused. Most (n = 56) had dementia, usually severe; 15 also had delirium. There were six nondemented patients (age range, 59-79 years, with a mean age of 67 years). Infrequent etiologies included neuroleptic malignant syndrome (n = 1) and hepatic encephalopathy (n = 1); in four, the cause was uncertain, although all were receiving lithium. EEG features analyzed included frequency of background rhythms, distribution of the TWs, periodicity, and epileptiform abnormalities. Background rhythms were slow in all but seven patients (mean, 6.2 +/- 1.7 [SD] Hz). TWs were maximal posteriorly in 47 patients and anteriorly in six and were diffuse in nine. Neuroimaging studies showed prominent posterior abnormalities in only one case. Periodicity was prominent in four patients; in two the TWs were maximal anteriorly. Interictal epileptiform activity was present in six, a history of seizures in eight, and myoclonus in four. TWs are uncommon in a psychiatric population; they occur primarily in elderly, severely demented patients. They are usually associated with background slowing, are often maximal posteriorly, and occasionally are periodic.

Electroencephalographic correlates of periventricular white matter lesions in probable Alzheimer's disease.

We evaluated the relationship between periventricular white matter lesions (PWMLs) and EEG abnormalities in probable Alzheimer's disease (AD). We visually analyzed the EEG of 27 probable AD patients with mild to moderate degree of cognitive impairment participating in a longitudinal study of dementia. Patients had both CT and MRI scans performed at baseline examination, which also included an EEG. PWMLs were rated in CT and MRI films using a semiquantitative method. The EEGs were classified according to the Mayo Clinic Classification System. Abnormal EEGs correlated with PWMLs rating scores were detected on CT, but not on MRI. These data suggest that the presence of PWMLs contribute to the abnormal EEGs observed in AD patients, and that white matter abnormalities in CT correlate better with both the clinical findings and EEG than does the more sensitive but less specific MRI.