Quantification and localization of EEG interictal spike activity in patients with surgically removed epileptogenic foci.

OBJECTIVE: To demonstrate if interictal spike activity was localized within the resected area in surgically treated epilepsy patients; and if there is correspondence between the degree of localization and improvement after surgery. METHODS: We analyzed long-term EEGs from 34 patients. Interictal spikes were grouped in clusters and averaged according to morphology and topography. The relative contribution of each cluster to the total number of spikes in each patient was estimated. Dipole and distributed EEG source localization of each cluster was made. The percentage of spike activity localized within the site of resection (SR) during the onset was estimated. The relationship between the percentage of activity within SR and the surgery outcome was assessed. RESULTS: Fourteen patients had 90-100% of spikes within SR, 9 had 50-89%. Most patients with more than 50% of activity localized within SR were seizure free, while the 5 patients who had all activity localized outside SR were not seizure free. CONCLUSIONS: Localization of clusters containing the largest quantity of interictal spikes during onset generally corresponded to the likely location of the epileptogenic cortex. SIGNIFICANCE: Computer-assisted EEG source localization with our methodology can be a useful adjunct for the evaluation of candidates for epilepsy surgery.

Suboccipital craniotomy for Chiari I results in evoked potential conduction changes.

BACKGROUND: Management of Chiari I is controversial, in part because there is no widely used quantitative measurement of decompression. It has been demonstrated that brainstem auditory evoked responses (BAER) and somatosensory evoked potentials (SSEP) have decreased conduction latencies after wide craniectomy. We analyzed these parameters in a suboccipital craniectomy/craniotomy procedure. METHODS: Thirteen consecutive patients underwent suboccipital decompression for treatment of symptomatic Chiari I. Craniectomy was restricted to the inferior aspect of the nuchal line, and in most cases the bone flap was replaced. Neuronal conduction was monitored continuously with median nerve somatosensory evoked potentials (M-SEP), posterior tibial nerve somatosensory evoked potentials (T-SEP), BAER, or a combination. The M-SEP N20, T-SEP P37, and BAER V latencies were recorded at four milestones - preoperatively, following craniotomy, following durotomy, and following closure. RESULTS: Five males and eight females, with average age of 9 years, were studied. Clinical improvement was noted in all 13 patients. M-SEP N20 latency decreased from a mean of 18.55 at baseline to 17.75 ms after craniotomy (P = 0.01); to 17.06 ms after durotomy (P = 0.01); and to 16.68 ms after closing (P = 0.02). T-SEP P37 latency did not change significantly. BAER V latency decreased from a mean of 6.25 ms at baseline to 6.14 ms after craniotomy (P = 0.04); to 5.98 ms after durotomy (P = 0.01); and to 5.95 ms after closing (P = 0.45). CONCLUSION: Significant improvements in conduction followed both craniectomy and durotomy. Bone replacement did not affect these results.

Papel de la corteza cerebral en la función motora / Brain cortex role in the motor function

Se presenta una revisión actualizada de las evidencias clínicas, anatómicas y experimentales del papel de distintas áreas de la corteza cerebral en la realización de la actividad motora voluntaria, haciéndose especial énfasis en los datos más recientes obtenidos en seres humanos sanos mediante el empleo de técnicas no invasivas como el flujo sanguíneo cerebral y el análisis de la actividad eléctrica cerebral. Se constata que el consenso actual en el ámbito internacional es que la participación de la corteza cerebral en la actividad motora es un proceso dinámico y multilocalizado en dependencia de las características específicas de la tarea a realizar, acorde a la teoría de los órganos funcionales de Anojin