Sensations and reaction times evoked by electrical sinusoidal stimulation.

OBJECTIVE: To determine whether 5 Hz and 2000 Hz sinusoidal electric currents evoke different sensations and to indirectly evaluate which peripheral nerve fibers are stimulated by these different frequencies. METHODS: One hundred and fifty subjects chose three among eight descriptors of sensations evoked by 5 Hz and 2000 Hz currents and the results were submitted to factor analysis. In 20 subjects, reaction times to 5, 250 and 2000 Hz currents were determined at 1.1 x ST and reaction times to 5 Hz currents were also determined at 2 x ST. RESULTS: Responses were grouped in four factors: Factor 1, which loaded mainly in descriptors related to tweezers stimulation, was higher than the other factors during 2000 Hz stimulation at 1.5 x ST. Factor 2, which loaded mainly in descriptors related to needle stimulation, was higher than the other factors during 5 Hz stimulation. Factor 1 increased and Factor 2 decreased with an increase in 5 Hz intensity from 1.5 to 4x ST. Reaction times measured from the fastest responses were significantly different: 0.57 s (0.16 to 1.60), 0.34 s (0.12 to 0.71) and 0.22s (0.08 to 0.35) for 5, 250 and 2000 Hz, respectively, and 0.22s (0.11 to 0.34) for 5 Hz at 2 x ST. CONCLUSIONS: Sinusoidal electrical stimulation of 5 Hz and 2000 Hz evoke different sensations. At juxta-threshold intensities, RT measurements suggest that 2000 Hz stimulates Abeta-fibers, 250 Hz Abeta- or A partial differential-fibers, 5 Hz Abeta-, A partial differential- or C-fibers. The fiber type, which was initially stimulated by the lower frequencies, depended on inter-individual differences.

Complete remission of epileptic psychosis after temporal lobectomy: case report.

We report a case of a female patient with refractory complex partial seizures since 15 years of age, recurrent postictal psychotic episodes since 35 which evolved to a chronic refractory interictal psychosis and MRI with right mesial temporal sclerosis (MTS). After a comprehensive investigation (video-EEG intensive monitoring, interictal and ictal SPECT, and a neuropsychological evaluation including WADA test) she was submitted to a right temporal lobectomy. Since then, she has been seizure-free with remission of psychosis, although with some persistence of personality traits (hiperreligiosity, viscosity) which had been present before surgery. This case supports the idea that temporal lobectomy can be a safe and effective therapeutic measure for patients with MTS, refractory epilepsy and recurrent postictal epileptic psychosis or interictal epileptic psychosis with postictal exacerbation.

Secondary bilateral synchrony due to fronto-mesial lesions. An invasive recording study.

Frontal lobe epilepsies may present difficulties in focus localization in the pre-operative work-up for epilepsy surgery. This is specially true in patients with normal MRIs. We report on a 16 years-old girl that started with seizures by the age of 8 years. They were brief nocturnal episodes with automatisms such as bicycling and boxing. Seizure frequency ranged from 4-10 per night. Scalp EEG showed few right frontal convexity spiking and intense secondary bilateral synchrony (SBS). High resolution MRI directed to the frontal lobes was normal. Ictal SPECT suggested a right fronto-lateral focus. Ictal video-EEG showed no focal onset. She was submitted to invasive recordings after subdural plates implantation. Electrodes covered all the frontal convexity and mesial surface bilaterally. Ictal recordings disclosed stereotyped seizures starting from the right mesial frontal. Using a high-resolution tool to measure intra and interhemispheric latencies, the timing and direction of seizure spread from the right fronto-mesial region were studied. Motor strip mapping was performed by means of electrical stimulation. She was submitted to a right frontal lobe resection, 1.5 cm ahead of the motor strip and has been seizure free since surgery (8 months). Pathological examination found a 4 mm area of cortical dysplasia. Invasive studies are needed to allow adequate localization in patients with non-localizatory non-invasive work-up and may lead to excellent results in relation to seizures after surgery.

Monoamines and their metabolites in cerebrospinal fluid and temporal cortex of epileptic patients.

The involvement of monoamines in the initiation or maintenance of epileptic phenomena has been extensively studied in cerebral tissues and in cerebrospinal fluid. The present work was undertaken to study monoamines and their metabolites in human spiking and non-spiking temporal cortex excised from patients with complex partial seizures unresponsive to available anticonvulsants. The same substances were also analyzed by HPLC-ED in cerebrospinal fluid obtained 24 h before the surgical procedure and compared with those from patients with chronic headache and normal neurological evaluation. The results show increased 5-HT, 5-HIAA and HVA levels in spiking compared with non-spiking cortex. Cerebrospinal fluid levels of 5-HIAA and HVA are concomitantly increased in epileptic compared with headache patients.

Surgical treatment of refractory epilepsy associated with space occupying lesions. Experience and review.

Surgery for space occupying lesions of the brain associated with intractable epilepsy represents a special problem because relief of the epilepsy in as much an operative goal as excision of the space occupying lesion itself. This study concerns 32 patients with space occupying lesions and intractable epilepsy who underwent excision of the lesion with acute intraoperative electrocorticography guided resection of the epileptogenic focus. Of the 32 patients, 16 formed a subgroup of gangliogliomas alone. The remaining were mixed lesions, predominantly benign. The duration of seizures in these patients ranged from 2 to 30 years, and the seizure frequency varied from 1 to 300 convulsions per month. The operative procedures included temporal corticectomy, amygdalo-hippocampectomy, and extratemporal corticectomies. Twenty nine patients were in Engel class I postoperatively, and three patients were in Engel class II. The findings with gangliogliomas were also considered in a separate group. This study strongly suggests that the operative procedure under electrocorticography guidance improves seizure outcome in space occupying lesions related intractable epilepsy.

Surgical approaches to tumors and epileptogenic zones close to Wernicke's area.

Surgical procedures near to language related brain regions may cause severe morbidity in relation to speech. Operations performed under local anesthesia and intraoperative cortical mapping may minimize these risks. Six patients with tumors near the Wernicke's area were treated (2 low-grade astrocytomas, 1 ganglioglioma, 1 xanthoastrocytoma, 1 metastasis, 1 glioblastoma). Their clinical presentation consisted of epilepsy (n = 4) and dysphasia (n = 2). The skin and periosteum were infiltrated with local anesthetic and an ample craniotomy was performed. Cortical stimulation with an unipolar electrode was then carried out with concomitant speech testing (mainly comprehension and sequential speech). After mapping, the best surgical approach aiming to avoid the mapped area was elected. In 5 cases the resection was total and in 1, partial (glioblastoma). There was a transitory (10 days) worsening of the pre-operative deficit in 1 case (glioblastoma). In 3 patients, the speech areas were displaced: posteriorly (n = 2) or anteriorly (n = 1). Surgical procedures under local anesthesia are safe and may avoid post-operative language disturbances in patients with tumors near to Wernicke's area.

Results from the intracarotid amytal procedure in patients with uni or bitemporal lobe epilepsy and mesial sclerosis.

This study discusses the results from the IAP and its lateralizing and prognostic value in patients with temporal lobe epilepsy (TLE) and mesial temporal sclerosis (MTS). Eighteen patients were submitted to the IAP. Fifteen had bitemporal and 3 unitemporal lobe epilepsies. All patients had MTS on MRI and in one there was an unrelated lesion in the contralateral hippocampus. Nine bitemporal patients passed after the injection ipsilateral to the MTS and 4 failed bilaterally. One bitemporal passed bilaterally. Seven of these bitemporal patients passed an injection ipsilateral to MTS and failed on contralateral injection. Two of the unitemporal lobe patients passed the ipsilateral injection and failed the contralateral one. One of the unitemporal lobe patients failed bilaterally the IAP. Overall, 56% of the group disclosed the pass ipsi-/fail contralateral pattern in the IAP. Eight patients were operated, are seizure free and had no additional memory deficit. Many patients with TLE were found to have the pass ipsi-/fail contralateral pattern in the IAP. This might prove to be of lateralizing and prognostic value in such cases.

Recomendaçöes referentes ao registro clínico digital do EEG / Recommendations of Digital Clinical Recording (EEG)

Até recentemente o registro do EEG convencional era feito quase exclusivamente em papel, com a análise sendo executada visualmente. Considerando apenas a gravaçäo (aquisiçä) do EEG, pode-se atualmente dividi-la de forma arbitrária em: 1) sistemas convencionais de registro de EEG em papel; 2) sistemas híbridos com registro em papel e a presença de processadores, porém sem registro digital; os processadores podem permitir, por exemplo, a alteraçäo de programas; 3) sistemas do tipo "paperless" näo digital, com registro através de sistema de modulaçäo em "tape"; 4) sistemas de registro digital do EEG (DEEG). A análise do EEG continua sendo feita da forma visual clássica, porém o registro digital permite também executar diferentes tipos de processamento do sinal do DEEG. Estas recomendaçöes, envolvendo apenas aspectos referentes ao registro clínico digital do EEG, representam o trabalho de uma comissäo organizada pelo departamento de mapeamento topográfico da SBNC e visam näo somente delinear requisitos mínimos como também comentá-los do ponto de vista didático

[Related observations for the use of mounting between neck posterior and scalp in evoked potentials by median nerve stimulation]. / Observações relacionadas à utilização de montagens entre a face posterior do pescoço e o couro cabeludo no potencial evocado por estimulação do nervo mediano.

Somatosensory evoked potentials after stimulation of the median nerve were obtained in a group of normal individuals. The components obtained between 12 and 22 ms were analysed with cephalic and non-cephalic references. It is shown that the P13-14 complex is the major contributor for the amplitude of the N13 component recorded with electrodes between the posterior neck and the scalp. It has not been possible to detect differences in amplitude or latencies for the components N18 and P22 recorded between FZ-non cephalic and C6-FZ. Implications of these findings to clinical interpretations of the responses are discussed.

Observaçöes relacionadas à utilizaçäo de montagens entre a face posterior do pescoço e o couro cabeludo no potencial evocado por estimulaçäo do nervo mediano / Related observations for the use of mounting between neck posterior and scalp in evoked potentials by median nerve stimulation

Foram realizados potenciais evocados por estimulaçäo do nervo mediano no punho, em grupo de voluntários normais. Foram avaliados os componentes que ocorreram entre 12 e 22 ms. Os registros foram feitos com referências cefálicas e näo cefálicas. Foi evidenciada maior contribuiçäo do complexo P13-14 na amplitude do componente N13 registrado entre C6 e Fz. Näo foram detectadas diferenças significativas na amplitude e latência dos componentes N18 e P22 quando avaliados nas montagens FZ-näo cefálico e C6-FZ. Säo discutidas as implicaçöes desses achados para a interpretaçäo clínica dessas respostas

Eating epilepsy.

Eating epilepsy is a rare type of reflex epilepsy. A 24 years-old male with eating reflex complex partial seizures was submitted to clinical, neurological, neuroradiological and EEG studies. Neurologic and CT examinations were normal. EEG recordings including video-EEG monitoring during meals disclosed focal abnormalities related to both temporal lobes prevailing at the left side and secondary bilateral synchrony mainly in more anterior regions. Ictal findings were similar to the interictal secondary bilateral synchrony except for its longer duration. PB, VPA and DPH monotherapies were ineffective. High dose CBZ monotherapy yielded good but incomplete seizure control. Since a big number of precipitants could be involved, no specific physiopathological basis could be established.

Secondary bilateral synchrony associated to a parasagittal tumor. Case report.

A 32 years old woman who had postural limbic and primarily generalized tonic-clonic seizures since the age of 11 presented to us with a CT image strongly suggestive of a mesial meningioma near the right cingulum. Her ictal EEG pattern was characterized by regular 1.5-2.0 Hz sharp and slow wave complexes. A right craniotomy was performed under general anesthesia and intraoperative electroencephalographic and electrocorticographic recordings were obtained by means of scalp steel electrodes and modified cerebellar stimulation electrodes, respectively. These recordings demonstrated that surface spikes were often independent from the electrocorticographically recorded ones. Before tumor excision, electrical stimulation of the peritumoral mesial cortex resulted in an increase in the epileptic activity. The stimulation of the cavity left after tumor excision led to a prolonged electrographic seizure and neurophysiological procedures were stopped. Post-operatively, the patient has remained seizure free for 6 months and her EEG was normal. The pre-, intra- and postoperative findings in this case suggest that the gliotic peritumoral mesial cortex was at least involved in the epileptogenic process.

Eating epilepsy

A epilepsia reflexa ao comer é uma rara de epilepsia reflexa. Um paciente de 24 anos com crises parciais complexas reflexas ao comer foi submetido a avaliaçöes clínica, neurológica neurorradiológica e eletrencefalográfica. O exame neurológico e a tomografia de crânio foram normais. Registros de EEG, incluindo menitorizaçäo vídeo-EEG durante a refeiçäo, mostraram presença de anormalidades focais relacionadas a ambos os lobos temporais, predominando à esquerda, e sincronia bilateral secundária, predominando em regiöes anteriores. Os achados ictais säo semelhantes à sincronia bilateral secundária interictal exceto por sua maior duraçäo. Monoterapias com PB, DPH e VPA näo surtiram efeito. Monoterapia com altas doses de CBZ trouxe bons resultados porém com controle incompleto das crises. Como grande número de fatores precipitantes estava potencialmente envolvido, näo foi possível determinar com precisäo a base fisiopatológica das crises reflexas neste caso

Secondary bilateral synchrony associated to a parasagittal tumor: case report

Uma paciente, com 32 anos de idade, com crises posturais e tônicoclônicas primariamente generalizadas, realizou TC de crânio que sugeria fortemente um meningioma mesial, sobre o cíngulo direito. Seu padräo eletrográfico ictal era caracterizado por complexos de onda aguda e onda lenta associadas na frequência de 1,5-2,0Hz, difusamente distribuídos. Craniotomia frontal direita associadas na frequência de 1,5-2,0 Hz, difusamente distribuídos. Craniotomia frontal direita foi realizada sob anestesia geral e registros electrencefalográficos e eletrocorticográficos foram obtidos por eletrodos de aço subgaleais e eletrodos de estimulaçäo cerebelar modificados, respectivametne. Estes registros demonstraram que as espículas registradas na convexidade eram frequentemente independentes daquelas registradas na profundidade. Antes da exérese tumoral, a estimulaçäo elétrica do córtex mesial peritumoral resultou em aumento da atividade espiléptica. A estimulaçäo da cavidade deixada pela retirada do tumor originou crise electrográfica prolongada e os procedimentos neurofisiológicos foram interrompidos. Nos primeiros meses pósoperatórios a paciente manteve-se sem crises. A seguir, apresentou episódio psicótico associado a surto de crises, voltando depois ao controle clínico inicial. Os achados pré-intra- e pós-operatórios neste caso sugerem que o córtex mesial estava envolvido no processo epileptogênico de sincronia bilateral secundária

Selective electroencephalograph-guided microsurgical callosotomy for refractory generalized epilepsy.

Between 1978 and 1985, 35 patients with medically refractory multiform seizures were submitted for sections of variable portions of the corpus callosum. Guided by intraoperative electroencephalographic and electrocorticographic monitoring, the section was carried out only in the portion of callosum that was involved in the maintenance of the bilaterally synchronous slow spike and wave discharge (as documented by intraoperative electrocorticography). In our patients, only part of the frontal corpus callosum needed to be sectioned to interrupt the bilateral synchrony of epileptic discharge. Of the 35 patients, operated on, 28 have had an adequate long-term follow up and are presented herein. All had significant improvement in seizure frequency and psychosocial functioning.

Acute reversal of flunitrazepam effects by Ro 15-1788 and Ro 15-3505: inverse agonism, tolerance, and rebound.

A phase 1 double blind crossover comparison of a new benzodiazepine antagonist (Ro 15-3505) with Ro 15-1788 and placebo, in the reversal of sedative and psychophysiological effects of single IV doses of flunitrazepam (2 mg), was carried out in 12 normal volunteers. The antagonists were equally effective, leading to full reversal of all effects with a potency ratio of approximately 2.5 mg Ro 15-1788 for 1 mg Ro 15-3505. Inverse agonism, in the form of unpleasant feelings and symptoms, was reported by all subjects following Ro 15-3505 but none after Ro 15-1788. Adaptational phenomena such as acute tolerance and rebound of sedative effects of flunitrazepam were also detected and their potential implications are discussed.

Corpus callosum stimulation and stereotactic callosotomy in the management of refractory generalized epilepsy. Preliminary communication.

Corpus callosum stimulation produced by chronically implanted electrodes, placed either by craniotomy or stereotactically, failed to control refractory generalized epilepsy in humans and also in experimentally produced penicillin epilepsy in cats. However, the patients that suffered craniotomy, frontal lobe retraction or pneumoencephalograms, without callosal section, showed remarkable improvement of their seizure condition due to these unspecific manipulation effects. Stereotactic anterior callosotomy emerged as a sequel of these functional neurosurgical findings, and as an alternative procedure to preclude undesirable neuropsychological and neurological side effects of split brain syndrome and of brain retraction, associated to conventional callosotomy. Ten patients with various disabling convulsive disorders have undergone this new operation, which showed to be less traumatic and better tolerated than open callosotomy.

Functional microsurgical partial callosotomy in patients with secondary generalized epilepsies. II. Mesial surface electrocorticography.

Eight patients with secondary generalized epilepsy not alleviated by medical treatment underwent partial callosotomy. During the surgical procedure, they had mesial surface ECoG recordings taken from both frontal and parietal lobes, using large flat multilead platinum electrodes, and simultaneously recordings from a number of scalp positions, using needle electrodes. In all cases studied, this approach demonstrated one or, more commonly, several focal areas of epileptiform activity discharging independently over the mesial aspects of one or both hemispheres. The findings were correlated with the pre- and postoperative EEG patterns, in the light of current concepts of generalized epilepsies.