Artifical vision for the blind: electrical stimulation of visual cortex offers hope for a functional prosthesis.

Electrical stimulation of the occipital cortex resulted in discrete photic sensations or "phosphenes" in two volunteers who had been totally blind for 7 and 28 years, respectively. Stimulation of multiple electrodes allowed one patient to recognize simple patterns, including letters. Both patients made an uneventful recovery, and the success of these experiments reinforces the hope that a functional visual prosthesis can be developed, although many problems remain to be solved.

Rasmussen's chronic encephalitis in adults.

OBJECTIVE: Rasmussen's chronic encephalitis, a cause of intractable epilepsy in childhood, is described in three adults. SETTING: Inpatient epilepsy unit. PATIENTS: Of 11 patients with pathological confirmation of Rasmussen's encephalitis, three were adults with intractable seizures, progressive sensorimotor deficits, and cognitive decline beginning at the ages of 36, 24, and 16 years. RESULTS: Clinical, electroencephalographic, and magnetic resonance imaging findings indicated patchy, multifocal involvement of primarily one hemisphere, but the adults had more evidence of disease in the opposite hemisphere than occurs in children. The sensorimotor deficit that the adults developed was greater and the cognitive decline was less than in children. Seizure control following multilobe resection was proportionate to the amount of tissue removed. Cytomegalovirus genome was found in the resected cortical tissue of all three patients. CONCLUSIONS: Rasmussen's encephalitis is a cause of intractable epilepsy with progressive neurological deficit in adults as well as children. Cytomegalovirus may be involved in the pathogenesis of the disease.

A 'possible' optic nerve meningioma.

A 58-year-old woman had progressive visual failure in her left eye over a two-year period. Radiological investigation, including tomography and computerized tomographic (CT) scanning, did not result in a diagnosis. When no useful vision remained, surgical exploration disclosed an optic sheath meningioma. Complete recovery followed removal of the tumor.

Cardiovascular effects of human insular cortex stimulation.

Recent investigations indicate a site of cardiac representation within the left insular cortex of the rat. Moreover, the results of lesion studies suggest left-sided insular dominance for sympathetic cardiovascular effects. It is unclear whether similar representation exists within the human insular cortex. Five epileptic patients underwent intraoperative insular stimulation prior to temporal lobectomy for seizure control. On stimulation of the left insular cortex, bradycardia and depressor responses were more frequently produced than tachycardia and pressor effects (p less than 0.005). The converse applied for the right insular cortex. We believe this to be the first demonstration of cardiovascular changes elicitable during insular stimulation in humans, and of lateralization of such responses for a cortical site. In humans, unlike the rat, there appears to be right-sided dominance for sympathetic effects. These findings may be of relevance in predicting the autonomic effects of stroke in humans and in the explanation of sudden unexpected epileptic death.

Nerve and muscle biopsy: electrophysiology and morphology in polyneuropathy.

We correlated the results of biopsy of a muscle nerve, a sensory nerve, and tibialis anterior muscle with electrophysiologic studies in 13 patients with sensorimotor polyneuropathy and 6 patients with normal findings. There were significant correlations between teased fiber changes and conduction abnormalities in both muscle nerves and sensory nerves. The density of large myelinated fibers in the lateral fascicle of the deep peroneal (LFDP) nerve correlated significantly with both the motor unit estimate and compound action potential amplitude of the extensor digitorum brevis (EDB) muscle. Other characteristics of the EDB muscle compound action potential related poorly to teased fiber abnormalities. There was good correlation of needle electrode study of the EDB muscle with teased fiber analysis of the LFDP nerve and with the morphology of the tibialis anterior muscle in 75 percent of the cases, and only minor discrepancies in the remainder. These results emphasize the close relationship between certain structural and electrophysiologic changes in subacute and chronic polyneuropathy.

Temporal lobectomy for intractable epilepsy in patients over age 45 years.

Surgical management of uncontrolled focal epilepsy is most commonly carried out in young adults with good results, but there has been some doubt about the effectiveness of cortical resection in older individuals. We assessed the outcome of temporal lobectomy done after age 45 years in 20 patients with intractable epilepsy followed for more than 2 years after surgery. During a mean follow-up of 5 years, six patients (30%) were seizure-free following surgery and seven (35%) had greater than 90% reduction in seizure frequency. This compares with an outcome of 40% seizure-free and 44% with greater than 90% seizure reduction in 68 younger patients aged 17 to 45 years; the differences do not achieve statistical significance. The outcome was better for complex partial seizures than for secondarily generalized seizures. Complications were no greater than in the younger patients. The findings indicate that surgery is an effective treatment alternative for intractable temporal lobe epilepsy in older patients since two of three of these patients will obtain satisfactory seizure control.

Spreading depression of Leão in rodent and human cortex.

Spreading depression (SD) has been implicated in the pathophysiology of a number of neurological conditions. The same methodology was used to elicit SD in anesthetized rats and in non-anesthetized patients undergoing cortical resections for intractable epilepsy. A slowly spreading DC potential shift (mean -9 mV) occurred in the cortex of 10 of 15 rats in association with attenuation of the electrocorticogram but this could not be reproduced in any of the human cortices (n = 23) where the mean potential shift was -0.56 mV (P < 0.0001). SD is more difficult to elicit in human than rodent cortex and may not occur in man.

Involvement of M1 and M2 muscarinic receptors of the basal forebrain in cholinergically mediated changes in the rat locomotion.

1. Wistar rats were implanted with cannulae into the medial preoptic and anterior hypothalamic areas for intracerebral injections. 2. Unilateral intracerebral injections of carbachol (1 microgram) into a limited area of the basal forebrain decreased significantly both the distance travelled by the animals and time spent walking. 3. In addition to the decrease in locomotion, it was demonstrated for the first time that injections of carbachol also slow animal movement by significantly decreasing speed of forward progression. 4. All locomotor effects of carbachol were reversed by local pretreatment with atropine (1 microgram) but not by pirenzepine (2 micrograms) suggesting that these effects were mediated by M2 muscarinic receptors with minimal or no M1 receptor involvement.

Consistency of seizure frequency estimates across time, methods, and observers.

Assessed the consistency of seizure frequency reports across observers, time, and methods. Thirty-two persons with intractable, partial seizures and 17 observers participated in a two-phase assessment procedure. During the first phase, subjects and observers provided retrospective seizure frequency estimates for two consecutive 30-day intervals. During the second phase, subjects and observers completed a daily seizure diary for 30 days. Patients' and observers' retrospective estimates were highly stable over a 2-month period. Substantial consistency was also found between two different recording methods (recall vs. diary) for subjects with epilepsy. In contrast, the observers' retrospective estimates were only moderately correlated with their prospective diary counts. Agreement between subjects' and observers' retrospective reports was also high. However, no significant association was found between their diary counts. Contrary to expectation, seizure frequency reports of patients with partial epilepsy showed moderately high consistency across time and between patient and observer pairs.

Rolandic arteriovenous malformations: improvement in limb function by IBC embolization.

Three patients with arteriovenous malformations in the rolandic region and significant limb deficit showed virtually complete functional recovery after awake operative embolization of most of the malformations using isobutyl-2 cyanoacrylate. Two of these patients, with functionally useless hands, had sustained the deficits months earlier as the result of a specific brain-damaging event: one as a result of surgery and the other as a result of a hemorrhage. Both of these showed significant return of function during the awake operative embolization procedure. The other patient had had progressive leg weakness over a 2 year period. The theory of steal phenomenon as an explanation for progressive neurologic deficits in association with large arteriovenous malformations must be extended to explain apparently stable deficits after some brain trauma (surgery or hemorrhage). These results suggest that some patients with arteriovenous malformations and without clinical deficits who are near a critical level of "near ischemia" may be thrown out of balance by an acute interceding event.

Progressive thrombosis of brain arteriovenous malformations after embolization with isobutyl 2-cyanoacrylate.

Embolization of brain arteriovenous malformations (AVMs) with isobutyl 2-cyanoacrylate (IBCA) is an alternative to surgical treatment when dealing with large AVMs with multiple arterial feeders. The deposition of IBCA in the nidus of the AVM may produce an active and progressive thrombosis that may lead to complete occlusion of the nidus and/or to progressive thrombosis of the draining veins. Four clinical examples of progressive thrombosis after IBCA embolization are demonstrated, including two cases in which late follow-up angiography showed complete obliteration of a partly embolized AVM.

Dominant-hemisphere arteriovenous malformations: therapeutic embolization with isobutyl-2-cyanoacrylate.

Embolization treatment of 16 patients with dominant-hemisphere arteriovenous malformations (AVMs) is described. This group was selected from 50 patients with brain AVMs embolized with isobutyl 2-cyanoacrylate (IBC-2) over a period of 3 years. All 16 AVMs were cortical in location; six involved the rolandic and speech areas, and four had a deep component. Ten AVMs were embolized through a transfemoral approach, an intraoperative approach was used for four cases, and a combined transfemoral/intraoperative approach was used in two cases. Complete obliteration of the AVM was obtained in one case. Partial obliteration and complete surgical resection was obtained in three cases. Obliteration of 70%-95% of the AVM was obtained in six cases and 45%-70% of the AVM was obliterated in six cases. IBC-2 embolization of the venous drainage was observed in three cases. After embolization, eight patients remained neurologically unchanged. Three patients had mild neurologic deficits that resolved completely within 48 hr; one had a deficit that cleared up 1 week later; and one had a deficit that disappeared within 6 months. In three patients a mild permanent neurologic deficit was evident 6 months after embolization.

MR in temporal lobe epilepsy: analysis with pathologic confirmation.

PURPOSE: We evaluated the MR findings in patients with temporal lobe epilepsy to determine the predictive value of MR imaging in assessing patient outcome. METHODS: MR studies from 186 of 274 consecutive patients who underwent temporal lobectomy for intractable epilepsy were reviewed retrospectively. Images were interpreted by an experienced neuroradiologist, who was blinded to the side of seizure activity and to pathologic findings. RESULTS: MR imaging exhibited 93% sensitivity and 83% specificity in detecting hippocampal/amygdalar abnormalities (n = 121), and 97% sensitivity and 97% specificity in detecting abnormalities in the rest of the temporal lobe (n = 60). Abnormal high signal of the hippocampus on T2-weighted images had a sensitivity of 93% and specificity of 74% in predicting mesial temporal sclerosis (n = 115). The presence of hippocampal atrophy on MR correlated with the duration of seizures. Sensitivity and specificity of MR imaging in detecting temporal lobe tumors (n = 42) were 83% and 97%, respectively, based on abnormal signal and mass effect. After surgery, 63% of patients were seizure free and 28% had a significant reduction of seizure frequency at an average of 24 months (range, 12 to 78 months) after surgery. Patients with a single lesion in the anterior temporal lobe or hippocampus/amygdala had a better outcome than patients with multiple lesions (n = 22). Interrater agreement varied from 0.4 to 0.93, with best agreement for tumors or abnormal hippocampal signal on T2-weighted images. CONCLUSION: MR imaging is highly sensitive in detecting and locating abnormalities in the temporal lobe and the hippocampus/amygdala in patients with temporal lobe epilepsy. Hippocampal atrophy appears to correspond to the duration of seizure disorder.

Response of neurons of the rat anterior hypothalamic-preoptic area to carbachol.

Behavioural effects of carbachol given into the hypothalamic/preoptic area have been demonstrated but there is a paucity of information about the response of single neurons to carbachol. The aim of the present study was to determine the response of spontaneously firing neurons in the rat hypothalamic/preoptic area to application of carbachol by iontophoresis or by pressure injection in a dose and volume comparable with that used in behavioural studies. Extracellular single unit recordings showed a significant decrease in mean firing rate in 82% of neurons responding to iontophoretic carbachol and in 75.5% of neurons responding to carbachol injected about 600 microns away. An increase in firing rate occurred in only 15 and 17.6% of neurons, respectively. Application of saline did not alter the mean firing rate while application of glutamate into the same areas or ejection into the vicinity of the same neurons caused an increase in mean firing rate in 94% of responding neurons. The results indicate that a decrease in mean firing rate is the predominant neuronal response to carbachol in the anteromedial hypothalamic/preoptic area of the rat and we suggest that this decrease may be associated with behavioural responses to carbachol.

Arctic and Antarctic exploration including the contributions of physicians and effects of disease in the polar regions.

A history of Arctic and Antarctic exploration, whether to find a Northwest Passage, North Pole, or South Pole, is a story of triumph and tribulation. The hardship experienced by polar explorers in the last 1000 years permeates the tales of achievement. Physicians and surgeons have played prominent roles in all major polar explorations. No significant Arctic voyage, particularly in the last 300 years, was made without a member of the party trained in the management of medical emergencies and in basic surgery. During times of health, surgeons functioned as the voyage naturalists with expertise in biology, botany, zoology, and the writing of scientific catalogs. Spurred by our interest and fascination with the history of polar exploration, we reviewed the roles of physicians and natural scientists in Arctic and Antarctic adventures.

Artificial vision for the blind by electrical stimulation of the visual cortex.

Artificial vision for the blind may be feasible by interfacing a television camera with electronics stimulating the visual cortex. The status of a major collaborative effort involving the College of Physicians and Surgeons of Columbia University, the University of Utah, and the University of Western Ontario is reviewed. Results have been very encouraging, although much work remains to be done.

How old people tolerate intracranial surgery for aneurysm.

The purpose of this paper is to examine how well (or poorly) patients past the age of 60 tolerate intracranial surgery for aneurysms in all locations. The records of 93 consecutive good risk patients (Botterell Grades 1 and 2) have been reviewed. Co-existing chronic medical conditions, e.g., hypertension, were ignored in patient grading. The results indicate that, for treatment of aneurysms on the anterior circulation, older patients tolerate intracranial procedures as well as younger patients. This is not true for operations upon posterior circulation aneurysms. Some possible reasons for this discrepancy are suggested.

Effect on the Cushing response of different rates of expansion of a supratentorial mass.

The effects on the three components (respiration, blood pressure, and heart rate) of the Cushing response (CR) were studied in cats by the continuous expansion of a supratentorial balloon. The rate of expansion was varied over the range of 0.006 to 0.6 ml/min, during whic systemic arterial pressure, heart rate, respiratory rate, and blood gases were monitored. For the different rates the time the CR took to develop, and the balloon volume required for that development were measured. The final volume ("critical volume") for eliciting the CR was more or less constant over the full range of rates of infusion (balloon expansion), a fact that supports that Monro-Kellie doctrine. This constancy of critical volume (CCV) gives rise to a highly statistically significant relationship between the rate of infusion and the latency to the production of the CR, and it is described by a power curve. Thus the development of cerebral dysfunction under these experimental conditions is independent of the rate of expansion and only dependent upon this critical volume. Exceptions to this concept of a critical volume, at the extreme of rates of expansion of lesions in patients, are predicted.

Malignant transformation of a dysembryoplastic neuroepithelial tumor. Case report.

A 29-year-old man presented in 1984 with a recent onset of partial seizures marked by speech arrest. Electroencephalography identified a left frontotemporal dysrhythmia. Computerized tomography (CT) scanning revealed a superficial hypodense nonenhancing lesion in the midleft frontal convexity, with some remodeling of the overlying skull. The patient was transferred to the London Health Sciences Centre for subtotal resection of what was diagnosed as a "fibrillary astrocytoma (microcystic)." He received no chemotherapy or radiation therapy and remained well for 11 years. The patient presented again in late 1995 with progressive seizure activity. Both CT and magnetic resonance imaging demonstrated a recurrent enhancing partly cystic lesion. A Grade IV astrocytoma was resected, and within the malignant tumor was a superficial area reminiscent of a dysembryoplastic neuroepithelial tumor (DNT). Data on the lesion that had been resected in 1984 were reviewed, and in retrospect the lesion was identified as a DNT of the complex form. It was bordered by cortical dysplasia and contained glial nodules, in addition to the specific glioneuronal element. The glial nodules were significant for moderate pleomorphism and rare mitotic figures. The Ki67 labeling index averaged 0.3% in the glial nodules and up to 4% focally. Cells were rarely Ki67 positive within the glioneuronal component. This case is the first documented example of malignant transformation of a DNT. It serves as a warning of the potential for malignant transformation in this entity, which has been traditionally accepted as benign. This warning may be especially warranted when confronted with complex forms of DNT. The completeness of resection in the benign state is of paramount importance.

Current status of artificial vision by electrocortical stimulation.

The history of the provision of artificial vision by electrocortical stimulation has its origin in observations over 50 years ago. However, the realistic modern stimulation of human visual cortex is only 20-years-old. No useful device has been devised as yet and it therefore remains purely experimental. The primary objective of such a prosthetic device is that of independent mobility. This would require the appreciation of half-tone pictures, the detection of depth and discontinuities in outlines, and a significant quality of resolution. Some of the problems which threaten resolution in such a device and the factors which must be overcome in order to achieve a useful visual prosthesis are discussed.