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.

EEG spectral findings in healthy, elderly men and women--sex differences.

Computerized spectral analysis of the EEG was performed in 119 healthy, elderly men and women, ranging in age from 60 to 87 years with an x age of 70.4 years, to evaluate gender-related variance. The groups did not differ in age, education levels or Folstein score. We compared the parasagittal derivations in men (n = 53) to women (n = 66), controlling for the effect of age by decade. Compared to men, women had a significant (usually P < 0.01) increase in the parasagittal mean frequency (1-30 Hz and 4-20 Hz), beta 1 and beta 2, while alpha 2 and theta-beta were decreased. Mean frequency did not differ significantly by decade, nor were there significant sex-age interactions. Our results extend previous EEG spectral findings to older, healthy, elderly subjects. Although the basis for the gender-related differences is uncertain, we suggest that quantitative EEGs establish gender-based norms in elderly adults.

Relationship between prolonged and self-limited photoparoxysmal responses and seizure incidence: study and review.

Photoparoxysmal responses (PPRs) are generalized epileptiform abnormalities occurring during photic stimulation. Prolonged PPRs, which outlast the stimulus, can be distinguished from self-limited PPRs, which cease spontaneously or when the flashes stop. Reilly and Peters (1973) found a higher incidence of seizures in patients with prolonged, rather than self-limited, PPRs. More recently, Jayakar and Chiappa (1990) reported a similar seizure incidence in the prolonged and self-limited groups. In order to assess these discordant results, we reviewed EEG records performed in our laboratory from 1983 to 1988. Sixty-eight EEGs had PPRs (19 prolonged and 49 self-limited). Patients with PPRs had a significantly higher incidence of seizures than controls (total patients versus controls, p less than 0.001; prolonged subgroup compared to controls, p less than 0.001; self-limited subgroup versus controls, p less than 0.01). Comparing PPR groups, we found that a prolonged PPR was associated with a higher incidence of seizures than a self-limited response (p less than 0.05); however, patients with a prolonged PPR more often had other epileptiform abnormalities than the self-limited group (p less than 0.001). There was no difference in seizure incidence between the PPR groups when comparing patients whose EEGs also contained other epileptiform abnormalities. Meta-analysis suggests apparent differences among the three studies are superficial.

Risk factors for stroke as predictors of platelet membrane fluidity in Alzheimer's disease.

We have previously reported that increased platelet membrane fluidity identifies a subgroup of patients with Alzheimer's disease who have distinct clinical features including an earlier age of symptomatic onset, a more rapidly progressive cognitive decline, and a decreased prevalence of focal electroencephalographic findings. In the current study, these patients also exhibited a decreased prevalence of risk factors for stroke compared with patients who had normal platelet membrane fluidity. Our findings suggest that the platelet membrane abnormality describes a clinical subgroup of patients with Alzheimer's disease who are less likely to have coexisting cerebrovascular disease than the remaining patients who meet clinical consensus criteria for probable Alzheimer's disease.

Alzheimer's disease with delusions and hallucinations: neuropsychological and electroencephalographic correlates.

We longitudinally evaluated the neuropsychological functions, rate of progression, and waking EEG findings in 17 patients with probable Alzheimer's disease (AD) with delusions and hallucinations, and compared them with those of matched AD patients without delusions and hallucinations. AD patients with delusions and hallucinations had a more rapid rate of decline, as measured by the Mini-Mental State Examination, a specific defect in receptive language, and a greater frequency of aggression and hostility. Visual EEG analysis showed that these patients had a significantly greater proportion of moderately abnormal EEGs, and spectral analysis confirmed the increased amount of delta and theta activity. These data demonstrate that AD patients with delusions and hallucinations have a greater degree of cerebral dysfunction and a relatively focal neuropsychological defect, which may indicate a localized pathologic abnormality.

Age at initial onset of depression and waking EEG variables in the elderly.

Depressive illness with initial onset after age 60 has different clinical and prognostic features compared to depression beginning at a younger age. We evaluated waking electroencephalograms (EEGs) in 61 elderly depressed patients (32 early onset, 29 late onset) without cognitive impairment and not receiving psychotropic medications. The groups were comparable for age, severity of Hamilton depression score, education, and Folstein Mini-Mental State scores. Conventional visual EEG analysis revealed no significant differences in the mean alpha rhythm, incidence of abnormal records, or types of EEG abnormalities. Computerized spectral EEG analysis was also performed in 48 patients (23 early onset, 25 late onset). There were no significant differences in the pooled parasagittal mean frequency, theta--beta difference, combined delta and theta percentage, or relative power of the frequency bands. Thus, waking EEGs do not differentiate between elderly patients with the initial onset of the depression before or after age 60.

Utility of EEG in delirium: past views and current practice.

The EEG is a useful and, at times, an essential test in the evaluation of delirium. In most patients with delirium, the EEG will show diffuse slowing and thus is helpful in differentiating organic etiologies from functional, psychiatric disorders. The degree of the EEG changes correlates with the severity of the encephalopathy so that the EEG may be used to help monitor therapy. In some delirious patients, the EEG may indicate whether the patient is suffering from focal, rather than global, impairment. Furthermore, the EEG is the only test that can identify an ongoing epileptic state (e.g., nonconvulsive status epilepticus) as being responsible for the clinical picture of confusion. Other electrophysiological tests that may prove helpful in the evaluation of delirium, such as computerized EEG spectral analysis, topographic brain mapping, and sleep studies, are briefly reviewed.

Myoclonic status epilepticus: a clinical and electroencephalographic study.

We reviewed the clinical features and ictal EEGs in 23 adults with myoclonic status epilepticus (MSE). Anoxic encephalopathy was the most common cause of MSE, occurring in 15 patients; 8 developed MSE within 14 hours following the anoxic insult. Metabolic encephalopathies were present in 4 patients, while 2 had degenerative CNS disorders. In 2 patients with generalized epilepsy, MSE developed during a medication change. Five types of EEG patterns were associated with MSE. Generalized periodic complexes (usually spikes, polyspikes, or sharp waves), often with attenuation of background activity between complexes (11 patients) or a burst-suppression pattern (4 patients), were the most common types. Outcome was poor: 20 patients died without regaining consciousness, while 1 remains in a vegetative state. The 2 patients with generalized epilepsy, both of whom were conscious during MSE, survived without sequelae.

Xenon-enhanced computed tomography compared with [14C]iodoantipyrine for normal and low cerebral blood flow states in baboons.

The correlation between the acute, invasive diffusible [14C]iodoantipyrine technique for cerebral blood flow and the noninvasive xenon-enhanced computed tomographic method has been assessed by simultaneous measurements in the baboon. Blood flows in small tissue volumes (about 0.125 cm3) were directly compared in normal and low flow states. These studies demonstrate a statistically significant association between the two methods (p less than 0.001). Similar correlations were obtained by both the Kendall (tau) and the Spearman (r) methods (r = 0.67 to 0.92, n greater than or equal to 19 for each study). The problems and limitations of such correlations are discussed.

Periodic EEG patterns: classification, clinical correlation, and pathophysiology.

In this article, we review periodic EEG patterns, which have been classified into four different types based on their interval duration (short or long) and topographic distribution (lateralized, bilaterally independent, or diffuse and synchronous). The four patterns are: (1) periodic lateralized epileptiform discharges; (2) bilateral independent periodic lateralized epileptiform discharges; (3) periodic short-interval diffuse discharges; and (4) periodic long-interval diffuse discharges. We also discuss morphology, etiologies, and clinical correlates of each pattern and possible pathophysiological mechanisms of periodicity.