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Biomedical subjects

R N Harner

Publications and source records attributed to R N Harner.

At least 19 recordsLinked to original sources
PubMed1992

Presurgical electroencephalographic patterns and outcome from anterior temporal lobectomy.

We reviewed data from 48 patients after anterior temporal lobe resection for medically intractable epilepsy. All had ictal electro-encephalographic (EEG) evidence of unilateral temporal lobe onset. Depth electrodes were used in 19 patients. Successful surgical outcome correlated significantly with factors that suggested a temporal lobe focus, particularly in the interictal scalp EEG. The most successful outcome occurred in patients with well-localized unilateral interictal temporal spikes (100% improved). The group with well-localized bilateral temporal spikes also did well (76% improved). Patients with extratemporal spread of the interictal spike on scalp EEG, either unilaterally or bilaterally, did less well. Only one third improved, despite extensive extracranial and intracranial monitoring, when indicated. The interictal scalp EEG may be the only EEG necessary for the presurgical evaluation of selected patients with intractable temporal lobe epilepsy.

Adolescent↗
PubMed1992

Interictal EEG topography of frontal lobe epilepsy.

Ictal localization of seizure discharges in the frontal lobe is difficult and not easily resolved by simple translation of techniques that have proved useful for localization within the temporal lobe. There is need for improved interictal localization of functional abnormalities within the frontal lobe utilizing CET and other methods of functional localization including magnetoencephalography, cerebral blood flow, and cerebral metabolism. It is likely that improved localization within the frontal lobe and clarification of clinical syndromes of frontal epilepsy will be obtained through the use of a combination of these interictal methods, aided by the results of intracranial ictal recording and surgical extirpation (7a,b,10a,b,15a-c).

Adult↗
PubMed1990

Singular value decomposition--a general linear model for analysis of multivariate structure in the electroencephalogram.

The application of Singular Value Decomposition (SVD) to analysis of EEG and evoked potential data has led to a hypothesis concerning the underlying structure of the EEG recorded from multiple channels. Based on the SVD algorithm the EEG is considered to be the linear combination of a sufficient number of features, each of which is defined in terms of its spatial distribution, temporal distribution, and amplitude. Use of this model leads to clear concepts concerning sampling, data reduction, normalization, and calculation of statistical significance, some of which are less evident when analysis is restricted to a single domain of interest.

Brain↗
PubMed1989

Computed EEG topography in acute stroke.

The potential for clinical application of computed EEG topography (CET) has been known since 1978. However, studies relating to the focal brain lesions are few. We have studied 19 cases of acute stroke involving the cerebral hemispheres. CET and EEG were recorded as soon as possible, usually within 1-3 days of onset. Repeat maps were recorded at 1 wk. Symptoms, neurologic exam, routine EEG and CT scan were compared with the CET of power spectral and flash evoked potential data. Statistical criteria were also applied. Good correlation was noted between CET and EEG and CT. Occasionally, CET was noted to provide information beyond EEG or CT. These early studies suggest a potential utility for CET in the early diagnosis of stroke.

Adolescent↗
PubMed1989

Initial experience with SPECT imaging of the brain using I-123 p-iodoamphetamine in focal epilepsy.

Nineteen patients with complex partial seizures refractory to medical treatment were examined with routine electroencephalography (EEG), video EEG monitoring, computed tomography or magnetic resonance imaging, neuropsychological tests and interictal single photon emission computed tomography (SPECT) with I-123 iodoamphetamine (INT). In 18 patients, SPECT identified areas of focal reduction in tracer uptake that correlated with the epileptogenic focus identified on the EEG. In addition, SPECT disclosed other areas of neurologic dysfunction as elicited on neuropsychological tests. Thus, IMP SPECT is a useful tool for localizing epileptogenic foci and their associated dynamic deficits.

Adolescent↗
PubMed1987

Magnetic resonance imaging after corpus callosotomy.

Magnetic resonance imaging (MRI) can visualize the extent of corpus callosotomy performed for medically intractable epilepsy not amenable to focal surgery. Five patients underwent complete callosotomy and one an anterior callosotomy, aged 19 to 24 years, 21 to 53 months (prior to scanning). T1 images showed complete absence of the callosal shadow in five cases and visualization of the genu and splenium in the sixth case. T2-weighted pulse sequence spin-echo MRI showed intense image throughout the region of the entire callosum in the two cases with the longest postoperative course. The two middle cases showed intense T2 signal from the splenium, and the two latest showed no increase in T2 signal. We believe the increase in T2 signal in the transected callosum may represent an in vivo example of anisomorphic gliosis. T1 images demonstrate the anatomic extent of transection, while T2 images demonstrate the chemical and pathophysiologic sequence of transection. Thus, MRI is the imaging test of choice to evaluate callosotomy patients.

Adolescent↗
PubMed1987

Computed EEG topography in epilepsy.

Computed EEG Topography (CET) of 74 cases of epilepsy demonstrates the potential utility of this method beyond that of the analog EEG for the quantification and localization of regions of epileptogenesis. For the detection and localization of focal epilepsy, CET was equal to or better than the EEG in 77 p. 100 of cases and provided more evidence of focal abnormality in 8.5 p. 100. The topography of spectral power and of early and late, extravisual, components of the averaged evoked potential to flash were abnormal in the region of interictal spike activity.

Adolescent↗
PubMed1978

EEG patterns at the time of focal seizure onset.

We studied the electroencephalographic pattern at the time of focal seizure onset in 41 patients. Progressive rhythmic EEG activity was characteristic of spontaneous focal seizures in man. Focal hypersynchrony was present in 49% of cases and served as an accurate localizing indication of cortical irritability. Interictal sharp or spike discharges were absent in 34% of cases. When present, spike and sharp discharges characteristically attentuate at the onset of rhythmic ictal activity. Recognition of the pattern of rhythmic ictal transformation is often essential for the electroencephalographic diagnosis of focal seizures.

Adolescent↗
PubMed1978

Computed EEG topography.

Using the method of sequential analysis, clinical EEGs are transformed into a temporal sequence of individual events with specification of amplitude, wave or segment interval, channel of origin and paroxysmal character in relation to background activity. These data can be viewed immediately in graphic form and stored for subsequent display or numerical analysis. The speed, format, and high information content of this method of data reduction allow real time topographic display of individual background and paroxysmal events - computed EEG topography (CET). Alpha asymmetry, slow activity, paroxysmal events and bilateral spike-wave activity are vividly represented and distinguished. There appears to be a close correlation between the usual method of EEG interpretation and the independent interpretation of a very compact quasi-anatomic CET with respect to nature and localization of normal and abnormal EEG activity. Initial observations suggest particular value of the CET in defining the extent of functional disturbance related to an anatomical lesion and in communicating this information to the electroencephalographer and to the clinician.

Computers↗
PubMedDate not supplied

Application of singular value decomposition to topographic analysis of flash-evoked potentials.

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↗