Guy Bouvier

Target Detection Deficits in Frontal Lobectomy

We examined the hypothesis of dorsomedial frontal lobe involvement in target detection through the effects of distractor interference and multiple target interference on unilateral lobectomy patients. Seven patients who underwent a unilateral frontal lobectomy for epilepsy involving dorsomedial cortex and variable amounts of lateral cortex were compared to 10 patients with a unilateral temporal lobectomy and to 10 normal adults on a visual character cancellation task. The task involved detecting occurrences of target characters embedded in rows of characters under three conditions: detection of one target character in the absence of distractors, detection of one target character among distractors, and detection of three targets among distractors. Visual detection performance was compared to that in the Stroop reading interference task. Frontals were predictably slower than the other groups in the baseline conditions of the character cancellation task and the Stroop task. After partialing out baseline detection performance in the character cancellation task, frontals showed an almost normal detection in the presence of distractors but were distinctly slower and made more errors than the other groups in multiple target detection. Frontals were also slower on the Stroop even after partialing out baseline naming performance. Temporals were normal on all tasks. Results suggest that frontal damage can affect selectivity in target detection as well as the Stroop and that this deficit is independent of the general psychomotor slowing observed in these patients.

Incidences of Venous Air Embolism and Patent Foramen Ovale among Patients Undergoing Selective Peripheral Denervation in the Sitting Position

OBJECTIVEThe incidence and severity of venous air embolism (VAE), a potentially fatal complication, among patients undergoing selective peripheral denervation in the sitting position have never been clearly established. We designed this retrospective study to assess the incidence and severity of VAE, the incidence of paradoxical air embolism, and the occurrence of patent foramen ovale, as detected with transesophageal echocardiography, as well as the effects of its detection on patient treatment. METHODSAfter institutional review board approval, data were collected from the charts of all patients who underwent selective peripheral denervation at our institution between 1988 and 2001. The severity of VAE was assessed by using a 5-point scale. RESULTSData for 342 patients were available for analyses. Seven patients exhibited VAE, yielding an incidence of 2%. The severity of VAE was 2/5 for three patients, 3/5 for three patients, and 4/5 for one patient. Air could be aspirated from the central venous catheter for three patients. No deaths occurred. Among the 96 transesophageal echocardiographic examinations performed, 5 cases of patent foramen ovale were detected (5.2%). For those patients, surgery was performed in the prone or park-bench position. No paradoxical air embolism was detected. CONCLUSIONThis is the first large study to directly assess the incidence and severity of VAE among patients undergoing selective peripheral denervation in the sitting position. We recommend that the detection of a patent foramen ovale prompt a change in position for this surgical procedure.

Stimulation of human somatosensory cortex : tactile and body displacement perceptions in medial regions

We examined the somatosensory perceptions evoked by stimulation of rolandic and parietal brain regions in 40 epileptic patients undergoing a presurgical investigation with intracerebral electrodes. Bipolar stimulation trains were delivered in an incremental sequence at medial and/or lateral contact pairs of stereotaxically implanted, multi-contact electrodes, while monitoring stimulus afterdischarge propagation with electrodes in frontal and temporal lobes. Rolandic stimulation evoked contralateral sensations, whereas sensations from either side were evoked in the opercular region. Stimulation of lateral posterior parietal cortex evoked only few sensations and these were restricted to the supramarginal gyrus. Contralateral sensations were evoked in the posterior cingulate gyrus, whereas ipsilateral sensations were evoked in the vicinity of the cingulate sulcus. Complex proprioceptive sensations in the form of bilateral feelings of levitation were elicited in a medial parietal region around the subparietal sulcus and not at any other site. These perceptions were not accompanied by any movement, tactile, or vestibular sensations, suggesting that the human sub-parietal sulcus region is linked to the proprioceptive processing system.

Electrical stimulation of the human brain in epilepsy.

Summary: The concordance between the epileptogenic area as determined by intracranially recorded spontaneous seizure onset and that determined by electrically induced auras or seizures in 126 patients with medically intractable epilepsy was studied. Four to 11 multicontact depth electrodes were chronically implanted in patients as part of a preoperative investigation procedure. Local‐ ization of the epileptic area was obtained from the record‐ ing of three spontaneous seizures and from stimulation data including self‐reported auras, seizures, and intracra‐ nial EEG afterdischarges recorded during an incremental stimulation sequence at all cortical pairs of contacts. Positive responses to stimulation were obtained in 63% of patients. Concordance between spontaneous and induced auras or seizures was >90% with single unilateral foci and less with multiple foci. Stimulation data reliably predicted the resection area in unilateral and bilateral temporal foci but not in other locations. Afterdischarge thresholds were not reliable predictors of the spontaneous seizure focus. The intracranial stimulation procedure used appears to provide useful confirmatory and complementary localiz‐ ing information in relation to that obtained from sponta‐ neous seizures.

Intracerebral amplitude distributions of the auditory evoked potential

Intracerebral auditory evoked potentials were recorded from multi-contact electrodes chronically implanted in frontal, temporal, and parietal regions of the brains of 10 epileptic patients. Binaurally presented tones produced a large widely distributed biphasic potential with a close latency correspondence to the scalp vertex response. In each hemisphere, this intracerebral response inverted in polarity from posterior temporal to frontal sites. This response also showed large amplitude changes in the inferior parietal lobe. The distribution of this response is compatible with bilateral posterior temporal sources with a dorso-frontal orientation.

Multiple subpial transection: report of 7 cases

7 cases of pure multiple subpial transection (MST) without associated cortical resection, for treatment of pharmaco-resistant partial epilepsy localized in highly functional cortical area, are reported. The transections were performed following the technique described by Morrell. The follow-up period ranged from 1 to 4 years. MST induced no significant neurological handicap: only 2 patients experiencing a transitory sensory-motor deficit and with total recovery within 1 month. With respect to seizures, 5 patients were improved with a decrease in seizure frequency of 100, 95, 75, 60 and 40%, respectively. Complex partial seizures changed postoperatively into simple partial seizures in 1 case. In conclusion, this procedure seems to be adequate, although no statistically significant results are available at this time. In our series, we believe failures could be attributed to either a very restricted area of transection or to an incorrect delimitation of the epileptic focus.

Anterior Callosotomy in Frontal Lobe Epilepsies

The investigation of frontal lobe epilepsies for the determination of surgical treatment gives rise to particular difficulties. Even depth electrode studies of spontaneous seizures, complemented by electrical stimulation, sometimes do not succeed in lateralizing the epileptogenic focus. In the stereotactic EEG (SEEG) laboratory of Hopital Notre-Dame (Saint-Hilaire et al., 1976; Bouvier et al., 1976) we have studied 17 patients with frontal lobe epilepsy. In ten patients we could demonstrate from spontaneous seizures which frontal lobe was involved first by the epileptogenic discharge. In four patients the spontaneous seizures started simultaneously in both frontal lobes. Only electrical stimulation, by reproducing the spontaneous seizure, could lateralize and localize the epileptic focus to one frontal lobe. Finally, in the three remaining patients neither the spontaneous seizures nor electrical stimulation could direct us to one particular frontal lobe. We concluded tentatively that these seizures were either bifrontal at the onset or unifrontal epilepsies with very rapid diffusion to the contralateral frontal lobe.

A difficult airway is not more prevalent in patients suffering from spasmodic torticollis: a case series.

PurposeWe designed this retrospective study to assess the frequency of difficult airway and difficult intubation in patients with spasmodic torticollis and compare it to that of the general population.MethodsAfter Institutional Review Board approval, data were collected from the charts of all the patients with spasmodic torticollis who underwent selective peripheral denervation at our institution between 1988 and 2001. The intubation grade was determined using the Cormack and Lehane laryngoscopic classification. The best laryngeal view was recorded.ResultsData from 342 patients were available for analysis. Fourteen patients had a difficult airway. In two patients, intubation was difficult with three attempts at laryngoscopy in one patient and use of fibreoptic bronchoscopy in the other. Twelve (3.5%) patients presented with laryngoscopic grades of III or IV The combined prevalence of laryngoscopic view grade III and IV and difficult intubation was 4.4%.ConclusionsThis study assesses the frequency of difficult intubation in patients suffering from spasmodic torticollis. When compared to the general population, these patients do not appear to have a higher frequency of difficult airway or difficult intubation.RésuméObjectifNotre étude rétrospective a été conçue pour évaluer la fréquence des problèmes des voles respiratoires et des difficultés d’intubation chez des patients qui présentent un torticolis spasmodique et les comparer à celle de la population générale.MéthodeAprès avoir reçu l’accord du Comité d’examen, nous avons recueilli les données des dossiers de tous les patients souffrant d’un torticolis spasmodique qui avaient subi une dénervation périphérique sélective à notre hôpital entre 1988 et 2001. La qualité de l’intubation a été déterminée par la classification laryngoscopique de Cormack et Lehane. La meilleure vision laryngée a été notée.RésultatsLes données de 342 patients étaient disponibles pour analyse. De ce nombre, 14 présentaient des problèmes des voies aériennes. Chez deux patients, l’intubation a été difficile et a nécessité trois essais pour la laryngoscope chez un patient et l’usage d’un fibroscope bronchique chez l’autre. Douze (3,5%) patients ont présenté un grade laryngoscopique III ou IV. La prévalence combinée d’une vision laryngoscopique de grade III et IV et d’une intubation difficile a été de 4,4 %.ConclusionNotre étude évalue la fréquence de difficulté d’intubation chez les patients qui souffrent de torticolis spasmodique. Comparés à la population générale, ces patients n’ont pas plus de problèmes des voies aériennes ou de difficultés d’intubation.

Relative localizing value of common tests used in the preoperative investigation of epileptic patients

We have compared the relative localizing value of common tests in the presurgical evaluation of epilepsy in 73 patients with depth electrode (SEEG) confirmed epileptogenic foci and excellent surgical outcome. We found the tests of abnormality (CT, amytal, neuropsychology) to be frequently non-informative and often discordant with SEEG. The EEG was concordant with the SEEG in 38% of cases and provided lateralization in 78%. EEG was less localizing than ictal behavior in frontals but not in temporals. The need for SEEG is rather evident in these results but could become attenuated by the development of the localizing power of scalp EEG.

Surgical Treatment of Spasmodic Torticollis by Peripheral Denervation

Spasmodic torticollis, also known as cervical dystonia, is similar to other forms of dyskinesia in that it was once considered a manifestation of a psychological disturbance rather than an organic disease. Brissaud (1) spoke of torticollis mentalis. At one time, patients suffering from spasmodic torticollis sometimes received psychiatric treatment based on the opinion of some psychoanalysts that patients were turning their head away because of unresolved psychological conflict.