Theodore Rasmussen

THE ROLE OF EARLY LEFT‐BRAIN INJURY IN DETERMINING LATERALIZATION OF CEREBRAL SPEECH FUNCTIONS

Preparatory to craniotomy for the relief of medically refractory focal epilepsy, the lateralization of cerebral speech functions was determined by the Wada intracarotid Amytal test in 134 patients with clinical and radiologic evidence of an early left-hemisphere lesion. Their results were compared with those for 262 patients (140 right-handed, 122 left-handed), who were tested in a similar way. One-third of the patients with early lesions were still right-handed, and 81% of these right-handers were left-hemisphere dominant for speech. In the non-right-handers, speech was represented in the left cerebral hemisphere in nearly a third of the group, in the right hemisphere in half the group, and bilaterally in the remainder. Bilateral speech representation was demonstrated in 15% of the non-right-handers without early left-brain injury and in 19% of those with evidence of such early injury, whereas it was extremely rare in the right-handed groups. In addition, nearly half the patients with bilateral speech representation exhibited a complete or partial dissociation between errors of naming and errors in the repetition of verbal sequences after Amytal injection into left or right hemispheres. This points to the possibility of a functionally asymmetric participation of the two hemispheres in the language processes of some normal left-handers. The results of the Amytal speech tests in this series of patients point to locus of lesion as one of the critical determinants in the lateralization of cerebral speech processes after early left-brain injury. It is argued that in such cases the continuing dominance of the left hemisphere for speech in largely contingent upon the integrity of the frontal and parietal speech zones.

Amino acid content of epileptogenic human brain: Focal versus surrounding regions

Abstract Amino acid analysis of tissue samples obtained from epileptogenic foci and surrounding cortical tissues in human brain indicated that the metabolism of certain amino acids is impaired throughout the cortex whereas for others the abnormality is more restricted to the site of maximal epileptogenic activity. The levels of GABA and aspartic acid were below normal in all regions sampled. In contrast, concentrations of glutamic acid and taurine lower than normal together with very high glycine levels were predominantly associated with the most hyperexcitable areas. The concentrations of alanine and serine were for the most part normal in both the focus and areas more distant to that site. A comparison of the amino acid levels in focal and surrounding tissue of the same patient demonstrated that the focal area most often contained the lowest concentrations of glutamic acid, aspartic acid and taurine in combination with the highest glycine content. The results are believed to indicate that in epileptogenic human cortex an uncoupling has occured between glucose oxidation and amino acid metabolism. In addition, or as a consequence of this abnormality, an impairment of protein metabolism may also be present.

Surgical Treatment of Complex Partial Seizures: Results, Lessons, and Problems

Summary: The underlying seizure tendency of complex partial seizures often involves the temporal region of the brain, but the frontal lobe can also produce similar complex partial seizures. By the end of 1980, 1,210 patients with medically refractory temporal lobe epilepsy had been operated on at the Montreal Neurological Institute. Nontumoral epileptogenic lesions were present in 1,034 patients, 169 had tumors, and 7 had major vascular malformations. Thirty‐seven percent of the 894 evaluable patients with nontumoral epileptogenic lesions have become and remained seizure‐free. Two hundred thirty‐six (26%) patients had a marked reduction of seizure tendency. Within the seizure‐free group, 63% had a complete or nearly complete reduction of their medically refractory tendency following temporal lobectomy. Of the patients with temporal lobe epilepsy due to tumoral lesions, 46% of the evaluable patients have become and remained seizure‐free, and 76% have had a complete or nearly complete reduction of seizure tendency.

Characteristics of a pure culture of frontal lobe epilepsy

Summary: Forty patients with nontumoral epileptogenic lesions who have undergone cortical excision of portions of the frontal lobe for the relief of medically refractory focal epilepsy at the Montreal Neurological Institute during the period 1930–1971 have become and remained seizure free for a minimum period of 5 years (median follow‐up 14 years). It seems logical to assume that, in these patients, the essential seizure‐producing mechanisms were contained in the excised portions of the frontal lobe and such patients thus represent a pure culture of frontal lobe epilepsy. The clinical, radiological, EEG, surgical, and pathological findings were analyzed. The variability in the clinical pictures and EEG data gives ample testimony of the complex and varied patterns of spread of epileptiform discharges through the brain in patients with epileptiform lesions of the frontal lobe. The data presented also bear on two secondary localizational aspects of frontal lobe epilepsy: (a) how much cortex must be recruited into epileptiform discharge to produce recurring seizures, and (b) how much of the total potentially epileptogenic cortex must be removed to produce a satisfactory reduction of the seizure tendency. These data also emphasize the importance of improving the accuracy of our methods of evaluating these secondary and tertiary localizational aspects of epileptic phenomena.

Surgical Treatment of Children with Medically Intractable Frontal or Temporal Lobe Epilepsy: Results and Highlights of 40 Years' Experience

Summary: Etiologic, pathologic, and clinical features of possible prognostic significance were studied in 118 children who underwent frontal or temporal lobe epilepsy surgery at the Montreal Neurological Institute (MNI) between 1940 and 1980 (excluding tumor cases). Mean age of seizure onset was 5.1 years (range 0–12 years), mean age at operation was 11.7 years (range 0.6–15 years), and median duration of follow‐up was 15 years (range 2–31 years). Thirteen of 45 frontal surgery patients and 43 of 73 temporal surgery patients had an excellent outcome. In the frontal surgery group, this was restricted almost entirely to patients with an established etiology, particularly if this included a circumscribed resectable structural abnormality. In the temporal surgery group, a history of early, prolonged febrile seizures was usually associated with good outcome, unless there was additional evidence of extratemporal epilepsy. In the entire series, the presence of a nonresectable structural lesion or secondarily generalized seizures was associated with a poor outcome.

Further Observations on the Syndrome of Chronic Encephalitis and Epilepsy

This report is a sequel to our 1958, 1960 and 1968 reports on a series of patients operated upon for focal epilepsy whose surgical specimens unexpectedly showed histological lesions typical of active encephalitis. None of these patients, now 27 in number, exhibited the clinical picture ordinarily associated with encephalitis. With one exception, all showed a severe focal seizure tendency beginning in infancy or childhood, often associated with episodes of epilepsia partialis continua. In addition, all except 2 showed slowly progressive neurological deterioration, usually hemiparesis and mental retardation, which advanced over periods of months or years before the progression became arrested. No infectious agent has yet been identified by standard viral studies carried out in the most recent 14 patients or by investigation for slow viruses in 6 patients operated upon between 1966 and 1971. The clinical course of this condition is outlined and the role, the timing and the results of treatment by craniotomy and cortical excision are discussed.

Evaluation of Insular Ablation in Surgical Treatment of Temporal Lobe Epilepsy

The presence of insular epileptiform abnormality in the postexcision cortical electroencephalogram, taken from the exposed cortex after temporal lobectomy for focal cerebral seizures raises the question of whether or not additional removal of insular cortex should be carried out in an effort to eradicate this residual EEG abnormality. Such removal has been advocated and carried out on a more or less routine basis by some neurosurgeons on the general principle that the more complete the removal of the epileptogenic cortex the better the clinical results. While in the dominant temporal lobe the extent of removal of cortex from the convexity is limited by structures involved in speech, and in some patients concern for memory requires limitation of the excision in the hippocampal region, there exists no “absolute” contraindication for ablation of insular cortex. Other neurosurgeons have considered insulectomy unnecessary in such cases, asserting that no significant differences in clinical follow-up results can be detected between patient groups with and without insular removals. This attitude receives support from the consideration of the potential hazards of the manipulation of the middle cerebral vessels incident to the removal of the cortex of the insula. Even if the technical part of the insulectomy is carried out without consequent complications, the already time-consuming operative procedure is prolonged when an insular ablation is performed. Reports on insular ablation were given by Guillaume and Mazars (3, 4), Guillaume et al. (5) and Penfield and Flanigin (6). In their serics of 24 insulectomies, 17 of which were classified as complete ones (71%), Guillaume et al. (5) reported 16 (67O/,) successful follow-up results and a complication rate of 21%. Penfield and Flanigin (6), reported 4 cases of insular removal, two patients with successful follow-up results. Ajmone Marsan and Baldwin ( I , p. 388: data from Table XV) advocate not removing potentially epileptogenic insular tissue persisting after temporal lobectomy

Rasmussen's encephalitis and the new hat

Neurology 1996;46:9-11 The prototype case of the syndrome now designated as Rasmussens encephalitis was identified in 1941 in a 7-year-old boy who developed right-sided seizures and subsequently slight right arm weakness; a left cortical biopsy revealed encephalitis. [1] By 1945 he had progressed to moderate right hemiparesis. A larger cortical resection again indicated inflammation. Seizures continued and right hemiplegia and hemianopia evolved. A left hemispherectomy was performed in 1956; sparse perivascular inflammation and glial nodules were found. Dr. Wilder Penfield, consulting in this case, raised the issues which continue to be debated to the present day. Is the encephalitic process the primary abnormality or a secondary response to the recurrent seizures? Why should an encephalitic process be unilateral? Can recurrent seizures lead to tissue destruction? Dr. Penfield, skeptical of the postulate that the syndrome was a primary inflammatory disorder, offered a new hat to anyone who proved him wrong. The clinicopathologic syndrome of childhood-adolescent onset of unilateral seizure disorder with progressive hemiplegia consequent to focal cortical inflammation and tissue destruction has now been recognized and described worldwide. The complete spectrum of the syndrome in terms of age of onset, rate of evolution, topographic distribution of pathology, natural course, and response to therapy continues to be debated. In the series of 48 cases from the Montreal Neurological Hospital reviewed by Oguni et al, [2] the mean age of disease onset was 7 years (range, 1-15 yr), one patient was aged 30 years. The series included cases that stabilized spontaneously and at least one case that improved; these observations create a dilemma in evaluating open-label therapy claims. Neuroimaging done serially on patients demonstrates progressive tissue destruction, but to date this measure has not been included in therapeutic outcome assessments. Pathologic studies of cases with serial samples collected from repeated surgery and …

Reevaluation of surgical failures and the role of reoperation in 39 patients with frontal lobe epilepsy.

Summary: Between 1929 and 1980, 284 patients with refractory nontumoral frontal lobe epilepsy (FLE) underwent operation at the Montreal Neurological Institute (MNI). We studied 39 patients (14%) who required reoperation. Mean age at the time of first operation was 18 years and at reoperation was 22 years. Clinical manifestations were similar to those of patients with “a pure culture of frontal lobe epilepsy” as reported by Rasmussen in 1983. At the time of first operation, large epileptogenic zones were noted in most patients. Resection was confined to the frontal lobe. Continuing seizure activity was due to residual areas of epileptogenesis, and reoperation with more extensive resection of cortex increased the number of seizure‐free patients. Twenty‐six patients underwent further frontal resection, and in 13 surgical removal was extended to the temporal lobe. Residual electrocorticographic (ECoG) spiking was documented in 15 of 23 (65%) of the reoperated patients. Thirty‐five patients were followed for periods ranging from 4 to 46 years. One fifth became seizure‐free, and 31% had significant seizure reduction. Thus, half of these patients had a good result. Patients with residual postexcision ECoG spiking had poor outcomes and evidence of large epileptogenic zones. None of the patients who underwent frontotemporal resections became seizure‐free. Reoperation should be considered if initial resection does not lead to a satisfactory result and may convert an initial failure into a good surgical result.

Seizures with Onset in the Sensorimotor Face Area: Clinical Patterns and Results of Surgical Treatment in 20 Patients

Summary: It is not generally appreciated that intractable seizures involving the face area are amenable to surgical treatment. Twenty patients with onset of sensorimotor seizures in the face area of the pre‐ and postcentral gyri have been studied and surgically treated since 1948. Seizures started in the face, tongue, or throat, followed by diverse patterns depending on spread of seizure activity. Two patients had epilepsia partialis continua; 6 had either tonic or atonic drop attacks. All patients had pre‐ and postcentral face area resections, 12 in the dominant hemisphere. In addition, 3 had more extensive postcentral removal, 7 had temporal lobe, and 4 had small separate or contiguous frontal or parietal resection. Because the seizures were not sufficiently reduced by the first operation, 6 required reoperation; 4 of these patients had residual epileptiform activity on electrocorticogram (ECoG) after the first resection. Three patients had new neurologic signs that did not return to the preoperative level, but in 2 of them the deficit related mainly to higher resection in the central area. All but 2 of these 20 patients had at least moderate seizure reduction. Corticectomy can be performed for treatment of seizures arising in the lower central area and usually does not lead to significant permanent neurologic deficit.