J.M. Van Buren

On the nature of the “absence” in centrencephalic epilepsy: A study of some behavioral, electroencephalographic and autonomic factors☆☆☆

Abstract 1. (1) A group of eighteen centrencephalic patients were examined on tests designed to measure the effects of spike and wave type EEG activity on sustained attention, sensory input, memory and simple motor behavior. In addition, measurements were made simultaneously of the following autonomic variables: blood pressure, heart rate, finger plethysmogram, skin resistance, esophageal and gastric motility and respiration. 2. (2) A total of 1,267 bursts of spike and wave were recorded in conjunction with the several tests. The behavioral correlates of the bursts were analyzed from the point of view of character (form), organization, maximal discharge, voltage, frequency, length, the background activity and several time-related variables. All of these were shown to be related to behavior on one or more of the tests. 3. (3) Bursts which are symmetrical, regular and bilaterally synchronous tend to produce more behavioral deficit than other bursts; tests requiring the complete attentive act (reception, discrimination, motor response) are more impaired during bursts than those which require only a part of this sequence; the motor task tended to be affected least. In addition, there is a retrograde amnestic effect. 4. (4) The most frequent autonomic changes were arrest of respiration, finger vasoconstriction, fall in skin resistance and increase in esophageal motility. These were not related in a one-to-one fashion to the behavioral modifications. 5. (5) In addition to the systematic relation between burst characteristics and the measures of behavior, three lines of evidence argue for the spike and wave pattern and attention impairment being considered as separable symptoms: These patients were impaired on the attention test in the absence of observable bursts; the behavior loss tends to lead the electrographic symptom in time; in some patients, lack of behavioral change was observed even in the presence of well-organized symmetric bursts. 6. (6) These findings were discussed in relation to previous studies of the behavioral effects of spike and wave complexes and to possible pathophysiological mechanisms in centrencephalic epilepsy.

Mechanism and Localization of Speech in the Parietotemporal Cortex

Cortical stimulation of the supramarginal and angular gyri elicited dysphasia. Delays in verbal response, misnaming, and difficulties in speech production were also elicited from this region. In two patients speech arrest occurred when stimulation was extended into the occipital cortex and the cortex medial to the supramarginal gyrus, respectively. In a left-handed patient, with speech representation presumed to be in the right hemisphere, neither stimulation nor ablation of the angular gyrus resulted in dysphasia. After anterior temporal resections two patients exhibited dysphasia in association with cortical edema. In one of these an additional resection in the inferior temporo-occipital region produced a marked but transient dyslexia. Observations of the disintegration of speech function during stimulation suggest that such stimulation interferes with a search mechanism by which the nonverbal concept of a visual stimulus is linked to a specific word in memory that is then withdrawn for use. A review of autopsy specimens demonstrates how close the cortex bearing indispensable speech representation lies to the occipital pole and the parietal midline. Because the gyral pattern is obscured by the meninges and is subject to anomalies, elective resection in these areas should be preceded by cortical stimulation and functional mapping.

The question of thalamic participation in speech mechanisms

Summary A late case of aphasia, predominantly in the audioreceptive sphere was studied by serial section reconstruction to demonstrate the regions in the anterior superior pulvinar related to the cortical destruction and speech disability. Critical review of the functional results of thalamic stimulation and primary intrathalamic lesions suggests caution in assigning to the dominant thalamus more than a minor role in the total speech mechanism.

Depth and direct cortical recording in seizure disorders of extratemporal origin.

This study is based on 28 patients with intractable seizures in whom exclusively extratemporal or a combination of temporal and extratemporal electrodes were chronically implanted for the localization of the epileptogenic process and possible surgical treatment. Clinical and electrographic data are briefly summarized, the indications for the use of implanted electrodes are outlined, and the number and position of the electrodes and the findings in each individual case are given. Four illustrative examples are described in greater detail. Mainly on the basis of data derived from this particular technique of investigation, surgical treatment was eventually carried out in 14 patients. It is concluded that the use of implanted electrodes in seizure disorders of probable extratemporal origin can be of real diagnostic benefit in certain specific situations. In most instances, however, this technique simply serves to demonstrate the complexity of an apparently simple case or, of greater clinical consequence, might tend to oversimplify cases that are actually very complex. Indeed, many data in this study raise some doubts about the validity of the classic concepts of “focal” epilepsy.

The fronto-striatal arrest response in man ☆

Abstract The “arrest response” produced by stimulation in the posterior frontal region and adjacent striatum has been studied in 30 patients. In essence it consists in the arrest of voluntary movement and may show additional features such as post-stimulation confusion, inappropriate or garbled speech, overt mood changes, contraversive movement of head and eyes, and occasionally somatic sensation. In two cases the response was produced from both hemispheres in the same individual. There was no evidence of a relationship between the lateralization of effective stimuli and handedness. In addition to interruption of speech, simple repetitive movements of the hand were usually inhibited and a formal continuous performance test (pressing a key to specific visual stimuli) showed marked impairment during stimulation. EEG monitoring failed to show post-stimulation epileptiform activation in 285 stimuli in thirteen patients at currents sufficient to produce arrest. In one case with prolonged post-stimulation confusion, slow wave activity was recorded from the stimulation site and recovery from this coincided with return of the patients responses to normal. Autonomic responses, predominantly arrest of respiration, were recorded from areas overlapping those of the arrest response. Ancillary evidence was reviewed supporting the role of the striatum as a modulator of sensory-motor activity and in this way being an essential mechanism in the anatomical representation of consciousness.

Fluorometric monitoring of NADH levels in cerebral cortex: preliminary observations in human epilepsy

In 14 patients operated upon for focal cerebral seizures under local anesthesia, cortical electrical activity was compared with the levels of nicotinamide adenine dinucleotide (NADH) observed fluorometrically. NADH levels fell 3 to 15% in response to 5-second intervals of cortical stimulation in 42 of 70 observations. Although a rough correlation was seen between the quantity of current delivered (milliamperes X seconds) and the NADH decrease, this varied from case to case. The presence of cortical afterdischarge often, but not invariably, corresponded to a greater percentage of change in the NADH levels. Averaging the NADH response to sporadic interictal epileptiform discharges failed to demonstrate concomitant NADH reductions. A similar lack of change was seen in four patients in whom low frequency spike foci were induced by topically applied penicillin in cortex destined for excision. Preliminary studies of the topography of spread of NADH change after cortical stimulation indicate that this is usually asymmetrical in human epileptogenic cortex. Under experimental conditions in cats, it seemed possible to differentiate primary from projected epileptiform activity, in that the projected activity had little or no concomitant fall in the NADH level after the electrographic spike. Pathological examination of the excised sites of NADH recording showed, with one exception, fibrous astrocytic transformation of the central cortex layers.

A Qualitative and Quantitative Evaluation of Parkinsonians Three to Six Years Following Thalamotomy (Part 1 of 2)

Seventy-eight patients with parkinsonism have been assessed over a postoperative interval of 3–6 years from 3 major aspects: (1) history and physical examination, (2) specific psychological tests, and

An Assessment of Cognitive Function in Postthalamotomy Parkinson Patients

Cognitive evaluation of 47 Parkinson patients for a mean of 17 months following unilateral thalamotomy, using the Wechsler-Bellevue adult intelligence scale and the Wechsler memory scale, showed mild

A Multipurpose CT-Guided Stereotactic Instrument of Simple Design

The instrument is based upon a radiolucent ring fixed to the skull by four pins. This locks into a frame for CT scanning from which the x, y and z stereotactic coordinates are derived. The head ring may be locked into a compatible support on the operating table for biopsy. A similar support and localization system is used for rotational radiotherapy. With the current 14 MeV apparatus, fields as small as 2 cm in diameter are available with 90% dosage fall-off in the surrounding 1-cm shell.

A stereotaxic instrument for man.

Abstract A human stereotaxic instrument has been in use since 1960 which embodies the following features: (1) Localization is achieved by fractional pneumography by routine demonstration of both the anterior and posterior commissures without the use of radiopaque oils. (2) Permits use with standard X-ray equipment. (3) Permits full surgical draping. (4) Instrument may be aligned with the intracerebral axes. (5) Full three plan graduated movement. (6) Permits skull entry at any point (apart from the central area at the vertex which underlies the apparatus) without the use of phantom target points or recomputation. (7) Precise realignment for staged procedures.