Singular value decomposition is a robust numerical method for decomposing a matrix of multichannel EEG or EP data into a sharply reduced set of features with corresponding waveform, amplitude, and spatial vectors. In 19 normal subjects aged 19 to 40 years, the three largest features computed by the SVD algorithm accounted for 93-98 percent of the total variance of the averaged flash-evoked potential. There was good separation of major brain areas as well as clustering of related electrode sites. Orthogonal rotation of the three spatial vectors is essential to see clustering of brain areas across subjects. Three-dimensional display showed the regular presence of orthonormal occipital, frontopolar, and vertex spatial vectors. Since the spatial feature vectors cluster tightly and yet are orthonormal, statistical comparison of patients with normal control groups will be facilitated.

Adult↗

PubMedDate not supplied

Ictal blindness and status epilepticus amauroticus.

Five cases of ictal blindness are presented. All are documented to be ictal by simultaneous EEG monitoring during the period of blindness. In three cases, the blindness was complete; in two, it manifested as a homonymous hemianopia. Three cases (including the two with hemianopia) were secondary to vascular lesions; one case was due to a metastatic lesion; and there was one case of idiopathic epilepsy. Age ranged from 13 to 74 years. In all cases, the blindness was reversible with anticonvulsant therapy. All cases but one lasted from hours to days, meeting a criterion of "status epilepticus amauroticus." In the literature, ictal blindness is seldom reported and even less often documented. Unexplained cortical blindness might represent unrecognized seizure activity more often than is appreciated.

Adolescent↗

PubMedDate not supplied

Bicycling movements as a manifestation of complex partial seizures of temporal lobe origin.

Alternating movements of the limbs during a seizure, especially bicycling movements of the legs, are often taken as strong evidence for the psychogenic origin of seizure activity in an adult population. A recent review of pseudoseizure manifestations concluded that alternating limb movements were "highly characteristic of pseudoseizures." We report two adult patients with complex partial seizures of temporal lobe origin, confirmed by ictal video EEG recording, in whom bicycling movements were the prominent ictal manifestation. Bicycling occurred 5-30 s after ictal onset and lasted 15-30 s. Use of video EEG recording continues to increase our understanding of the wide range of behaviors which may occur in the course of an epileptic seizure, particularly complex partial seizures. Few absolute clinical criteria remain to distinguish epileptic seizures from pseudoseizures. These two cases and one other reported case clearly remove bicycling movements from that category.

Adult↗

PubMedDate not supplied

Utilization of a two-channel, microprocessor-based EEG device for monitoring cognitively vulnerable patients.

Several experiments were conducted to validate the use of a two-channel microprocessor-based electroencephalographic (EEG) device for detecting changes in EEG background rhythm in the clinic or at the bedside. The reliability of background measures in healthy individuals was evaluated by obtaining EEG data on 20 control subjects on two occasions separated by at least 1 day. The sensitivity to an experimental toxic encephalopathy was evaluated using measures of EEG and the Buschke Memory Selective Reminding Test after the administration of scopolamine hydrobromide, 0.86 mg subcutaneously, to three healthy volunteers. Postdrug measures of the EEG showed significant group differences from controls at 1 and 2 hours for relative alpha and relative theta power. The drug-induced change for each individual exceeded the predicted range calculated from data on control subjects. These findings suggest the feasibility and the potential utility of this method. This approach was extended to the elderly with measures on 102 subjects (average age, 85 years) living in an institutional setting. EEG measures in the population were of acceptable reliability and were significantly correlated with Mini-Mental State Examination (MMSE) scores (r = -.375 for theta and .357 for beta). Preliminary findings suggest that this method may detect metabolic encephalopathies in the elderly. The study demonstrates the potential value of this approach and suggests the need for further research.

Age Factors↗