Biomedical subjects
D S Dinner
Publications and source records attributed to D S Dinner.
A negative motor response elicited by electrical stimulation of the human frontal cortex.
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Basal temporal language area.
Language interference was elicited by electrical stimulation of the dominant basal temporal region in 8 out of 22 cases and in none of 7 cases with subdural electrodes implanted over the nondominant temporal lobe. Language interference was elicited by stimulation of electrodes placed over the fusiform gyrus 3-7 cm from the tip of the temporal lobe. Electrical stimulation of the basal temporal language area produced a global receptive and expressive aphasia with speech arrest at high stimulus intensities. Other higher cortical function, for example copying complex designs or memory of nonverbal information was intact, in spite of the total inability to process verbal information. At lower stimulus intensities partial aphasias with a predominant receptive component occurred. Surgical resection of the basal temporal language area produces no lasting language deficit.
Versive eye movements elicited by cortical stimulation of the human brain.
We studied the eye movements (EM) elicited by electrical stimulation of the frontal lobe in 19 awake patients evaluated with subdural electrodes for epilepsy surgery. All patients had only contralateral conjugated EM. They were saccadic in 16 patients (84%). Head version, always following the eye deviation, occurred in 11 patients (58%). We also determined the eye field somatotopic distribution analyzing the responses obtained from the electrodes adjacent to the eye fields. All patients had motor cortex contiguous to the eye fields. In 17 patients (90%) the eye fields were located in front or at the level of the motor representation. There was no silent cortex between the motor strip and the eye fields.
Supplementary motor seizures mimicking pseudoseizures: some clinical differences.
Supplementary motor seizures (SMS) are among the group of frontal lobe seizures that may often be misdiagnosed as pseudoseizures (PS). We designed this study to determine the value of clinical phenomena in distinguishing between the two. In a series of patients with SMS, we identified those with symptoms mimicking PS and compared the clinical phenomena with those of clinically similar PS. We found that SMS are short in duration, stereotypic, tend to occur in sleep, and often present with a tonic contraction of the upper extremities in abduction. This sign was specific for SMS, particularly when occurring at the onset. Conversely, PS are long in duration, nonstereotypic, and occur in the awake state. We conclude that clinical phenomena may be useful in distinguishing PS from SMS, although the final diagnosis must be documented by neurophysiologic means.
Dystonic posturing in complex partial seizures of temporal lobe onset: a new lateralizing sign.
We observed unilateral dystonic posturing of an arm or leg in 41 complex partial seizures (CPS) from 18 patients. In all cases this was contralateral to the ictal discharge. Unilateral automatisms occurred in 39 of 41 seizures on the side opposite the dystonic limb. Version occurred in 11 of the 41 CPS to the same side as the dystonic posturing and always followed the posturing. Subdural recordings of seven seizures showed ictal onset from the mesial basal temporal lobe. At the onset of dystonic posturing, maximum ictal activity was in the basal temporal lobe with minimal involvement of the cerebral convexity. Unilateral dystonic posturing occurs frequently in CPS of temporal lobe onset and is a lateralizing sign with a high degree of specificity. It probably reflects spread of the ictal discharge to basal ganglia structures.
Sleep and pediatric epilepsy.
Characteristic of the intimate relationship between sleep and epilepsy are an increase in IEA in nonREM sleep and a decrease in REM sleep, in both generalized and partial epilepsies. The morphology of epileptiform discharges may also be affected by sleep, with a change or breakdown of the generalized pattern in generalized epilepsy, but a better definition of sharp waves in partial epilepsy, during nonREM sleep. One notes a predilection for certain types of epilepsy to occur in sleep, such as benign focal epilepsy of childhood, or to occur shortly after awakening (juvenile myoclonic epilepsy). Epilepsy may disrupt the sleep architecture with an increase in light sleep and a decrease in deep sleep, and an increase in awake time after sleep onset. Sleep is an important activator of IEA and is of value both in the routine EEG evaluation of epilepsy as well as in more prolonged studies used in epilepsy monitoring units.
EEG evaluation for epilepsy surgery in children.
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Subdural electrodes in the evaluation for epilepsy surgery in children and adults.
To evaluate the utility and safety of chronic extraoperative subdural EEG and functional localization studies in children compared to adults, we studied 61 patients each of whom had similar evaluations for epilepsy surgery, regardless of age. The 23 children and adolescents (3 to 18 years old) and the 38 adults (20 to 41 years old) each had several days and nights of extraoperative EEG from scalp and chronically-implanted subdural electrodes, and the same percentage of children and adults also had functional localization studies including cortical electrical stimulation. The methods and results of these studies and of the subsequent resections did not differ between the two groups, and they both had similar rate of complications and similar incidence of good outcome. The subdural technique was as effective and well-tolerated in children and adolescents as in adults. Other invasive EEG techniques have not yet been systematically compared between children and adults, but the subdural technique, at least, appears to be suitable for patients over a wide age range.
Localization of cortical function: new information from extraoperative monitoring of patients with epilepsy.
Intraoperative cortical stimulation for evaluation of cortical function has been used extensively to define the extent of cortical excisions for surgical treatment of epilepsy. With chronic implantation of subdural electrodes, extraoperative cortical stimulation becomes possible, and these favorable testing conditions permit more precise mapping of the cortex. This assists the surgeon in planning details of the surgical removal and also provides additional data about the function of the human cortex. Four aspects in which detailed extraoperative studies have provided information complementing the pioneer studies of Foerster, Penfield, and others will be discussed here: (1) Frontal eye field: In the human, this is always an integral part of the motor strip (most probably located in Brodman's area 4 and/or 6) and elicits only conjugate eye movements to the contralateral side with a variable upward component. (2) Negative motor area: Stimulation of the inferior frontal gyrus immediately in front of the face area and of the supplementary motor area of the dominant and nondominant hemisphere produces "inhibition" of voluntary fine movements. (3) The movement related potentials (bereitschaftpotential, negative slope, and motor potential) are strictly localized to the portion of the sensorimotor strip where the movement is represented. Lower amplitude bereitschaftpotentials can also be detected in the homotopic ipsilateral sensorimotor cortex and in the supplementary motor cortex. (4) Three language areas can be distinguished by electrical stimulation: Broca's, Wernicke's, and the basal temporal language area. Electrical stimulation in all these areas produces a similar deficit, but Broca's area tends to overlap with the inferior frontal negative motor area. This may explain the predominant motor deficit of Broca's aphasia.
Ictus emeticus: an electroclinical analysis.
We report 31 episodes of ictal vomiting in nine patients, documented by simultaneous video and EEG recordings. In four patients, chronically implanted subdural electrode arrays recorded the event. Only one patient showed "projectile" vomiting. Amnesia for the episode occurred in eight of the nine patients. Interictal epileptiform abnormalities were maximal in the right temporal region in seven patients and bitemporal in two. Ictal epileptiform abnormalities were lateralized to the right hemisphere and involved temporal lobe structures in all patients. Three of four patients recorded with subdural electrode arrays were seizure-free following right temporal lobectomy, and the fourth continues to have ictus emeticus at a reduced rate. The consistent right hemisphere lateralization of seizures in this series corroborates with earlier reports documenting right-sided lateralization in four of five previous cases. Two features that help delineate paroxysmal vomiting as an ictal event are (1) patient unawareness of vomiting and (2) its association with other ictal phenomena.
Supplementary motor seizures: clinical and electroencephalographic findings.
The clinical and EEG features of 11 patients with seizures arising in the supplementary motor area (SMA) were reviewed. All patients underwent prolonged EEG with simultaneous video recording. Three patients had recordings and electrical stimulation of the SMA using subdural electrode arrays. All patients had preservation of consciousness during the seizure unless it became secondarily generalized. Tonic posturing of the extremities was present in all patients, and in seven it was present bilaterally. Adversive movements were not seen unless the seizure became secondarily generalized. Interictal and/or ictal abnormalities were present at or adjacent to the midline in ten patients. Seizures arising from the supplementary motor region are clinically distinct, and the diagnosis can almost always be verified with prolonged EEG/video recording.
Electrophysiologic pathologic correlations in patients with complex partial seizures.
We studied interictal activity and site of ictal onset in 26 patients with complex partial seizures of temporal lobe origin. All patients had prolonged electrocorticographic recordings from subdural electrode arrays placed both over the convexity and beneath the temporal lobe. We found a significant correlation between the epileptogenic focus and the type of pathologic lesion found at time of surgery. Macroscopic lesions strongly tended to have an epileptogenic focus on the lateral surface of the temporal lobe; patients with only microscopic abnormalities tended to have an epileptogenic focus in the mesial/basal region of the temporal lobe.
HLA-DR2 and narcolepsy.
Tissue typing was performed on 14 narcoleptics as defined by both strict sleep laboratory and clinical criteria. Six of these patients were blacks from North America, a race underrepresented in previous studies. All patients were HLA-DR2-antigen positive and had the same HLA-DR2 subtype. Clinical severity of disease was not correlated with HLA-DR2 heterozygosity or (putative) homozygosity. This study confirms that the extremely high association between HLA-DR2 and narcolepsy holds across comparisons of the three races studied to date when both clinical and sleep laboratory data are used. The presence or absence of HLA-DR2 in patients presenting with hypersomnolence may help support or exclude, respectively, a diagnosis of idiopathic narcolepsy.
Extraoperative cortical functional localization in patients with epilepsy.
Functional localization prior to cortical resections for intractable seizures has usually been performed in the operating room in awake patients. Chronically placed subdural electrodes offer the possibility of performing such testing outside of the operating room and without the unavoidable stresses and time limitations of the surgical setting. The use of the technique is reviewed.
Clinical outcome after complete or partial cortical resection for intractable epilepsy.
This is the first epilepsy surgery series to analyze the definition of "completeness" of resection, based solely on results of chronic scalp and subdural EEG recording. When patients had complete removal of all cortical areas with ictal and interictal epileptiform discharges, the clinical outcome was usually good. When areas with epileptiform discharges were left behind, good outcome was significantly less frequent. This correlation between complete resection and good outcome was independent of the presence or absence of CT-detected structural lesions or sharp waves on post-resection electrocorticography. These results support completeness of resection, defined by prolonged extraoperative EEG, as an important factor in seizure surgery.
Cortical generators of somatosensory evoked potentials to median nerve stimulation.
In 12 patients with intractable partial seizures, chronically implanted subdural electrodes were used to define the relationship of the epileptogenic focus to cortical functional areas. Cortical somatosensory evoked potentials (SEPs) to median nerve stimulation were recorded from these electrodes. The initial cortical positivity, postrolandic primary cortical potential (PCP), was recorded in all 12 patients with a mean latency of 22.3 +/- 1.6 msec. A potential of opposite polarity, prerolandic PCP, was defined in nine patients with a mean latency of 24.1 +/- 2.7 msec. The latency of the postrolandic PCP was 1.61 +/- 1.59 msec shorter than the prerolandic PCP (p less than 0.01, paired t test). The maximum amplitude postrolandic PCP was 2.1 times larger than the maximum prerolandic PCP (p less than 0.02, paired t test). The phase reversal of the SEPs was compared with the position of the rolandic fissure (RF) defined by electrical stimulation. This study shows that the latency and amplitude characteristics of post- and prerolandic PCPs are significantly different and give support to the concept that they are produced by different generators; and cortical SEPs are helpful in locating the RF.
Magnetic resonance imaging (1.5 tesla) in patients with intractable focal seizures.
Magnetic resonance (MR) (1.5 tesla) studies were performed in ten patients with temporal lobe epilepsy and two with temporofrontal epilepsy. Two patients with temporal lobe epilepsy and one with temporofrontal epilepsy exhibited areas of increased signal intensity on T2-weighted images in the mesiobasal portion of the temporal lobe shown by electroencephalography to be the epileptogenic focus; no analogous abnormalities had been found in these patients on computed tomographic scans. Pathologic studies have not revealed a specific ultrastructural correlate for the MR findings in this group of patients. We found MR to be a useful, noninvasive diagnostic adjunct in the presurgical assessment of some patients with temporal lobe epilepsy. Where abnormalities were found, they corresponded with the epileptogenic focus as defined by electroencephalography.