Neuropsychological assessment in pediatric epilepsy surgery: A French procedure consensus.

Neuropsychological assessment is a mandatory part of the pre- and post-operative evaluation in pediatric epilepsy surgery. The neuropsychology task force of the ILAE - French Chapter aims to define a neuropsychological procedure consensus based on literature review and adapted for French practice. They performed a systematic review of the literature published between 1950 and 2023 on cognitive evaluation of individuals undergoing presurgical work-up and post-surgery follow-up and focused on the pediatric population aged 6-16. They classified publications listed in the PubMed database according to their level of scientific evidence. The systematic literature review revealed no study with high statistical power and only four studies using neuropsychological scales in their French version. Afterwards, the experts defined a neuropsychological consensus strategy in pediatric epilepsy surgery according to the psychometric determinants of cognitive tests, specificity of epilepsy, surgery context, French culture and literature reports. A common French neuropsychological procedure dedicated to pediatric epilepsy surgery is now available. This procedure could serve as a guide for the pre- and post-surgical work-up in French centers with pediatric epilepsy surgery programs. The main goal is to anticipate the functional risks of surgery, to support the postoperative outcome beyond the seizure-related one, while taking into consideration the plasticity and vulnerability of the immature brain and allowing the possibility of collaborative studies.

Basal temporal lobe epilepsy: SEEG electroclinical characteristics.

OBJECTIVE: Temporal lobe epilepsy is the most common type of focal drug-resistant epilepsy. Seizures with predominant involvement of basal temporal regions (BTR) are not well characterized. In this stereo electroencephalography (SEEG) study, we aimed at describing the ictal networks involving BTR and the associated clinical features. METHODS: We studied 24 patients explored with SEEG in our center with BTR sampling. We analyzed their seizures using a quantitative method: the "epileptogenicity index". Then we reported the features of the patients with maximal epileptogenicity within BTR, especially ictal network involved, ictal semiology and post-surgical outcome. RESULTS: We found that rhinal cortex, parahippocampal cortex and posterior fusiform gyrus were the most epileptogenic structures within the BTR (mean EI: 0.57, 0.55, 0.54 respectively). Three main groups of epileptogenic zone organization were found: anterior (23% of total seizures) posterior (30%) and global (47%, both anterior and posterior). Contralateral spread was found in 35% of left seizures and 20% of right seizures. Naming deficit was more prevalent in left BTR (71% vs 29% in right seizures; p = 0.01) whereas automatic speech production was preferentially represented in right seizures (11% vs 54%; p = 0.001). Surgery was proposed for 11 patients (45.8%), leading to seizure freedom in 72% (Engel Class I). One patient presented post-operative permanent functional deficit. CONCLUSION: Basal-temporal lobe epilepsy seems to be a specific entity among the temporal epilepsy spectrum with specific clinical characteristics. Resective surgery can be proposed with good outcomes in a significant proportion of patients and is safe provided that adequate language assessment has been preoperatively made.

French neuropsychological procedure consensus in epilepsy surgery.

INTRODUCTION: Neuropsychological assessment is an integral component of the surgical procedure in patients with epilepsy. As no French consensus for neuropsychological assessment was available, the main goal of this work was to define French neuropsychological procedure consensus in regard to literature review. METHOD: A panel of expert in neuropsychology was created within the framework of the French League Against Epilepsy. A systematic search of publications from 1950 to 2017 listed in PubMed database was conducted leading to a classification of articles according to their level of scientific evidence. French neuropsychological procedure consensus was then carried out with an expert panel of expert. RESULTS: Low scientific evidence of neuropsychological data was reported. A panel of expert proposed a comprehensive neuropsychological assessment procedure including the exploration of intellectual efficiency, long-term memory, short-term and working memory, attention, executive functions, processing speed and motor skills, language, visual processing, praxis, psychobehavioral, and social cognition. DISCUSSION: A common procedure for assessing cognitive and psychobehavioral function is now available in patients with epilepsy undergoing surgical evaluation have been established, they may help to improve the quality of care and the patient experience. This work highlights the need of furthers investigations and the necessity to develop specific tools with normative data.

Identification reaction times of voiced/voiceless continua: a right-ear advantage for VOT values near the phonetic boundary.

We explored the degree to which the duration of acoustic cues contributes to the respective involvement of the two hemispheres in the perception of speech. To this end, we recorded the reaction time needed to identify monaurally presented natural French plosives with varying VOT values. The results show that a right-ear advantage is significant only when the phonetic boundary is close to the release burst, i.e., when the identification of the two successive acoustical events (the onset of voicing and the release from closure) needed to perceive a phoneme as voiced or voiceless requires rapid information processing. These results are consistent with the recent hypothesis that the left hemisphere is superior in the processing of rapidly changing acoustical information.

Specialization of left auditory cortex for speech perception in man depends on temporal coding.

Speech perception requires cortical mechanisms capable of analysing and encoding successive spectral (frequency) changes in the acoustic signal. To study temporal speech processing in the human auditory cortex, we recorded intracerebral evoked potentials to syllables in right and left human auditory cortices including Heschl's gyrus (HG), planum temporale (PT) and the posterior part of superior temporal gyrus (area 22). Natural voiced /ba/, /da/, /ga/) and voiceless (/pa/, /ta/, /ka/) syllables, spoken by a native French speaker, were used to study the processing of a specific temporally based acoustico-phonetic feature, the voice onset time (VOT). This acoustic feature is present in nearly all languages, and it is the VOT that provides the basis for the perceptual distinction between voiced and voiceless consonants. The present results show a lateralized processing of acoustic elements of syllables. First, processing of voiced and voiceless syllables is distinct in the left, but not in the right HG and PT. Second, only the evoked potentials in the left HG, and to a lesser extent in PT, reflect a sequential processing of the different components of the syllables. Third, we show that this acoustic temporal processing is not limited to speech sounds but applies also to non-verbal sounds mimicking the temporal structure of the syllable. Fourth, there was no difference between responses to voiced and voiceless syllables in either left or right areas 22. Our data suggest that a single mechanism in the auditory cortex, involved in general (not only speech-specific) temporal processing, may underlie the further processing of verbal (and non-verbal) stimuli. This coding, bilaterally localized in auditory cortex in animals, takes place specifically in the left HG in man. A defect of this mechanism could account for hearing discrimination impairments associated with language disorders.

Contribution of different cortical areas in the temporal lobes to music processing.

Music processing ability was studied in 65 right-handed patients who had undergone unilateral temporal cortectomy for the relief of intractable epilepsy, and 24 matched normal controls. The ability to recognize changes in note intervals and to distinguish between different rhythms and metres was tested by presentation of sequences of simple musical phrases with variations in either pitch or temporal dimensions. The responses (right or wrong) enabled us to determine in which component of the music processing mechanism the patients had deficits and hence, knowing the positions of the surgical lesions, to identify their separate cerebral locations. The results showed that a right temporal cortectomy impaired the use of both contour and interval information in the discrimination of melodies and a left temporal cortectomy impaired only the use of interval information. Moreover, they underlined the importance of the superior temporal gyrus in melody processing. The excision of a part of the auditory areas (posterior part of the superior temporal gyrus) was found to be most detrimental for pitch and temporal variation processing. In the temporal dimension, we observed a dissociation between metre and rhythm and the critical involvement of the anterior part of the superior temporal gyrus in metric processing. This study highlights the relevance of dissociating musical abilities into their most significant cognitive components in order to identify their separate cerebral locations.

Pitch perception: a difference between right- and left-handed listeners.

Various results indicate that the perception of a complex tone's "virtual" pitch is generally lateralized in the right cerebral hemisphere. The primary aim of this work was to test the hypothesis that this is not the case for the "spectral" pitch percepts induced by complex tones. Forty right-handed and 18 left-handed listeners were monaurally presented with pairs of successive tones made up of n consecutive equal-amplitude harmonics of a missing fundamental (F0). n varied from two to four across subjects. In "test" conditions, the paired tones differed in F0 but the spectral components of the tone with the lower F0 were higher in frequency than the corresponding components of the other tone (except for one component, which was identical). The subjects had to say if, from one tone to the other, pitch rose or fell. From such judgements, one could infer that the pitch dominantly perceived in each tone was a virtual pitch (corresponding to F0) or a spectral pitch (i.e., the pitch of a single spectral component, or a perceptual quality corresponding to the centroid of the power spectrum). For n = 2, the results indicated that virtual pitch was less salient than spectral pitch; the opposite occurred for n = 3 and n = 4. The ear (left or right) to which the stimuli were presented had some influence on the judgements, in the expected direction. However, this influence was not a robust one. Unexpectedly, a reliable effect of the listeners' handedness was observed: for each value of n, the judgements indicating virtual pitch perception were less frequent in the left-handers than in the right-handers. Discrimination performances measured in "control" conditions showed that the handedness factor was not confounded with a factor of frequency discrimination ability.

[Cortical mechanisms of auditive perception in man: contribution of cerebral potentials and evoked magnetic fields by auditive stimulations]. / Etude des mécanismes corticaux de la perception auditive chez l'homme: apport des potentiels intracérébraux et des champs magnétiques évoqués par les stimulations auditives.

The goal of this study is to determine and localize the generators of different components of middle latency auditory evoked potentials (MLAEPs) through intracerebral recordings in auditory cortex in Human (Heschl's gyrus and Planum Temporale). The intracerebral data show that the generators of components at 30, 50, 60 and 75 msec latency are distributed medio-laterally along the Heschl's gyrus. The 30 msec component is generated in the dorso-postero-medial part of the Heschl's gyrus (primary area) and the 50 msec component is generated laterally in the primary area. The generators of the later components (60-75 msec) are localized in the lateral part of the Heschl's gyrus that are the secondary areas. The comparison with the generators of the components of the magnetic auditory evoked field and the tonotopic organization of the auditory cortex are discussed.