Evidence for reflex activation of experiential complex partial seizures.

Reflex activation of seizures by thoughts or mental images is suggested by patients but has not been objectively demonstrated. The authors present a report of a man with experiential complex partial seizures reliably activated by thinking about his family home. During monitoring, such seizures were repeatedly induced in this way. Seizures were refractory to antiepileptic drugs, but ceased after left temporal resection. Pathologic examination showed cortical dysplasia.

Reflex epilepsy and reflex seizures of the visual system: a clinical review.

Reflex epilepsy of the visual system is charecterised by seizures precipitated by visual stimuli. EEG responses to intermittent photic stimulation depend on the age and sex of the subject and on how stimulation is performed: abnormalities are commonest in children and adolescents, especially girls. Only generalised paroxysmal epileptiform discharges are clearly linked to epilepsy. Abnormal responses may occur in asymptomatic subjects, especially children. Photosensitivity has an important genetic component. Some patients are sensitive to patterns, suggesting an occipital trigger for these events. Myoclonus and generalised convulsive and nonconvulsive seizures may be triggered by visual stimuli. Partial seizures occur less often and can be confused with migraine. Although usually idiopathic, photosensitive epilepsy may occur in degenerative diseases and some patients with photosensitive partial seizures have brain lesions. Sunlight and video screens, including television, video games, and computer displays, are the commonest environmental triggers of photosensitive seizures. Outbreaks of triggered seizures have occurred when certain flashing or patterned images have been broadcast. There are regulations to prevent this in some countries only. Pure photosensitive epilepsy has a good prognosis. There is a role for treatment with and without antiepileptic drugs, but photosensitivity usually does not disappear spontaneously, and then typically in the third decade.

Oxidative phosphorylation defect in the brains of carriers of the tRNAleu(UUR) A3243G mutation in a MELAS pedigree.

MELAS is a mitochondrial encephalomyopathy characterized clinically by recurrent stroke-like episodes, seizures, sensorineural deafness, dementia, hypertrophic cardiomyopathy, and short stature. The majority of patients are heteroplasmic for a mutation (A3243G) in the tRNAleu(UUR) gene in mitochondrial DNA (mtDNA). In cells cultured in vitro, the mutation produces a severe mitochondrial translation defect only when the proportion of mutant mtDNAs exceeds 95% of total mtDNAs. However, most patients are symptomatic well below this threshold, a paradox that remains unexplained. We studied the relationship between the level of heteroplasmy for the mutant mtDNA and the clinical and biochemical abnormalities in a large pedigree that included 8 individuals carrying the A3243G mutation, 4 of whom were asymptomatic. Unexpectedly, we found that brain lactate, a sensitive indicator of oxidative phosphorylation dysfunction, was linearly related to the proportion of mutant mtDNAs in all individuals carrying the mutation, whether they were symptomatic or not. There was no evidence for threshold expression of the metabolic defect. These results suggest that marked tissue-specific differences may exist in the pathogenic expression of the A3243G mutation and explain why a neurological phenotype can be observed at relatively low levels of heteroplasmy.

Nonconvulsive status epilepticus of frontal origin.

OBJECTIVES: To determine the electroclinical characteristics and causative factors of nonconvulsive status epilepticus (NCSE) of frontal origin. METHODS: The authors conducted a 5-year prospective study. RESULTS: Ten patients were studied (seven men, three women; mean age, 56.4 years). Six patients did not have previous epilepsy. The mean diagnostic delay was 48 hours (range, 3 to 96 hours). Two types of frontal NCSE were identified. In type 1 (n = 7), mood disturbances with affective disinhibition or affective indifference were associated with subtle impairment of cognitive functions without overt confusion. EEG showed a unilateral frontal ictal pattern and normal background activity. In type 2 (n = 3), impaired consciousness was associated with bilateral, asymmetric frontal EEG discharges occurring on an abnormal background. Ictal and postictal 99mTc hexamethyl propylene amine oxime (HMPAO) SPECT was performed in five patients and showed unilateral or bilateral frontal HMPAO uptake that aided localization, especially in type 2 NCSE of frontal origin. Etiologies included a focal frontal lesion in six patients (three of which were tumors), neurosyphilis, and nonketotic hyperglycemia. Eight patients did not respond to initial IV benzodiazepine (BZ), but IV phenytoin controlled six patients successfully. The immediate outcome was favorable in all patients. There was no long-term recurrence of SE in seven patients. CONCLUSIONS: NCSE of frontal origin is a heterogeneous syndrome. Some cases are best described as simple partial NCSE, others as complex partial SE, and there are forms that overlap with absence SE. Emergency EEG and neuropsychological assessment are diagnostic, and SPECT may be useful. Many patients may not respond to IV BZ.

The benign occipital epilepsies of childhood: an overview of the idiopathic syndromes and of the relationship to migraine.

Benign occipital epilepsy of childhood is an idiopathic partial epilepsy syndrome with elementary visual symptomatology, frequently associated with other ictal phenomena. Seizures are usually followed by postictal headache and are often associated with interictal occipital rhythmic paroxysmal EEG activity that appears only after eye closure. In some children the ictal visual symptoms or the interictal EEG abnormalities may not be demonstrated. The clinical and/or EEG manifestations of other forms of idiopathic partial or generalized epilepsy may be found in association. Occipital spikes in non-epileptic children with defective vision, occipital slow spike-and-wave found in some patients with the Lennox-Gastaut syndrome, focal epilepsy due to occipital lesions, seizures originating in the temporal lobe secondary to an occipital abnormality, and complicated or basilar migraine must be considered in the differential diagnosis. Early-onset benign occipital epilepsy or seizure susceptibility syndrome deserves to be considered separately. It has been defined by Panayiotopoulos as consisting of brief, infrequent attacks or prolonged status epilepticus and characterized by ictal deviation of the eyes and/or head and vomiting, occurring in children usually between the ages of 3 and 7 years. Advances in molecular genetics will help decide whether these two disorders are indeed distinct. Benign occipital and benign rolandic epilepsy are commonly associated with migraine. The selective involvement of the occipital lobe in migraine has not been fully explained. The association between benign occipital epilepsy and migraine is likely related to this underlying mechanism as well. The "fixation off" phenomenon or blocking of occipital epileptic discharges by eye opening is not specific to benign occipital epilepsy of childhood and may be found in symptomatic epilepsies as well. Migraine and epilepsy are distinct disorders, both as far as their pathophysiologic mechanisms and clinical symptomatology are concerned. There is however an overlap in some patients and a causal relationship may exist in some, leading to clinically distinct migraine epilepsy syndromes. Here too, clarification of the molecular basis of migraine and of epilepsy will throw light on the nature of the relationship between the two conditions.

George A. Savoy, visionary benefactor of Canadians with epilepsy, and the history of the Savoy Foundation for Epilepsy.

George A. Savoy was born in Cohoes, New York, in 1873. He left the U.S.A. in 1921 to manage the Canadian branch of a large manufacturer of ledgers and looseleaf registers. This company was asked to supply Professor Jasper's laboratory with rolls of plain unlined paper and it was George Savoy who later developed fanfolded and lined EEG paper, which was first used at the Montreal Neurological Institute. He also had personal contacts with Wilder Penfield concerning their mutual interest in the needs of patients with epilepsy. He was a successful industrialist involved with several charitable organizations funding programmes for people with epilepsy. He was opposed to the sectarianism then prevalent in Quebec, which was unfamiliar to him, and in reaction built his own institution, Dieppe House, a home for people with epilepsy, later renamed <>. It was to operate without regard to race, language or religion. In 1971, his son Harold and other generous donors decided to create a foundation to support research in epilepsy. The Foyer Savoy was sold in 1988 and the proceeds used to increase the endowment of the foundation. His grandson George M. Savoy is the current president. The fourth generation is also represented by Caroline Savoy, daughter of the president, who joined the board of directors in 1992. The foundation will distribute from $300,000 to $400,000 yearly to researchers from many different countries working in the field of epilepsy in universities and hospitals throughout Canada.

Phenytoin toxicity due to interaction with clobazam.

The benzodiazepine antiepileptic drug clobazam can be added to existing AED treatment, usually without clinical toxicity. We report 3 patients in whom the addition of clobazam led within several weeks to clinically obvious phenytoin (PHT) intoxication in patients who had been taking maximum tolerable PHT doses. Symptoms and high PHT levels resolved with lowering the PHT dose. Clobazam and norclobazam levels were not elevated. This interaction is probably related to interference with hepatic degradation of PHT. Clinicians should be aware of possible PHT intoxication in patients starting clobazam.

The risk of automobile accidents with seizures occurring while driving: relation to seizure type.

Automobile accidents occurred with 55% of seizures in epileptic drivers with both well-described seizures at the wheel and a well-classified epilepsy diagnosis. A further 38% of seizures would have led to accidents in less fortunate settings. Complex partial seizures occurred in 81% of patients and were responsible for 88% of accidents. Immediate alterations of consciousness were significantly more likely to lead to accidents than were seizures beginning with an aura. Motor activity during simple partial seizures was also responsible for some accidents. Differences in seizure frequency may account for different crude accident rates among studies of epileptic drivers. We suggest guidelines for licensing restrictions that seem safe and reasonable.

Compulsive respiratory stereotypies in children with autistic features: polygraphic recording and treatment with fenfluramine.

Syncopes due to compulsive respiratory stereotypies were studied in eight patients with autistic features. Most had been referred for episodes thought to be intractable epileptic seizures. Polygraphic recording showed two types of syncope, one induced by prolonged apnea and the other by a prolonged Valsalva maneuver. Fenfluramine, 1.5-3 mg/kg per day, was given in an open trial. In four of five cases with frequent Valsalva maneuvers, respiratory stereotypies and syncopes were suppressed for 2-18 months. Patients with periodic apneas were more severely retarded and had less clear benefit. Side effects consisted of dose-dependent sedation and mild weight loss which stabilized without interrupting treatment. We suggest that these syncopes are volitional and may be associated with pleasant sensations. A double-blind placebo-controlled trial of fenfluramine seems warranted in such patients.

Lissencephaly (agyria-pachygyria): clinical findings and serial EEG studies.

Fifteen cases of lissencephaly were studied and the literature reviewed. The authors conclude that the clinical findings of lissencephaly in infancy are non-specific, consisting of developmental delay and hypotonia. While the CT scan establishes the diagnosis, it may also be strongly suggested by an EEG showing 'major fast dysrhythmia', characterized by abnormally rapid, very high-voltage activity, predominantly in the alpha and beta frequency bands. Some possible mechanisms for this highly suggestive EEG pattern are proposed.

The long-term course of primary generalized epilepsy with persisting absences.

The long-term course of primary generalized epilepsy with absences persisting after the age of 30 to 61 years was studied in 26 patients, each followed clinically and by EEG for 20 to 37 years. Whether treated or not, absences became less frequent, but only rarely ceased, and 92% of patients with persisting absences eventually developed generalized convulsions. EEG background activity did not deteriorate, and the classic spike and wave complexes remained typical in 84% of patients. In 36% of cases, almost all of them women, psychomotor slowing was observed, which did not affect job performance. It was not related solely to duration or severity of epilepsy, or to antiepileptic drugs, and some hormonal mechanism may be partly responsible.

Classification of the epilepsies.

We review the development of the classification of the epilepsies. Primary epilepsies are relatively benign, usually age-limited syndromes without clinical or radiologic evidence of brain lesions, and are related to a heritable constitutional predisposition to epilepsy. They usually respond well to antiepileptic drugs. The biochemical correlates of primary generalized epilepsy have been demonstrated in animals and man and have been related to diffuse cortical hyperexcitability, which has been linked to this disorder. The pathophysiology of the primary partial or focal epilepsies is poorly understood but does not appear to depend on focal brain lesions. We suggest that these are due to relatively localized areas of cortical hyperexcitability confined to isolated corticothalamic sectors and depend on interrelations between a constitutional cortical hyperexcitability and normal cortical maturation. The secondary epilepsies are associated with clinical and radiologic evidence of brain lesions and are often resistant to anticonvulsants. Secondary generalized epilepsies, with an associated diffuse encephalopathy, are typified by the Lennox-Gastaut syndrome. The presentation of the secondary partial epilepsies depends on the site of the lesion. The pathogenesis of epilepsy is multifactorial, and a preexisting constitutional predisposition can interact with an acquired diffuse or focal encephalopathy, facilitating the clinical expression of one or the other.