Impairment of Consciousness Induced by Bilateral Electrical Stimulation of the Frontal Convexity
PURPOSE Our aim was to evaluate the efficacy of ESCM (electrical stimulation of the centromedian thalamic nucleus) in treatment of generalized seizures of the Lennox-Gastaut syndrome (LGS) and improvement of patient disability. METHODS Thirteen patients with LGS were studied. They had severe generalized tonic-clonic seizures (GTC) and atypical absences (AA). All patients had at least a 6-month baseline before bilateral electrode implantation to the centromedian (CM) nuclei of the thalamus to undergo therapeutic ESCM. Once implanted, electrodes were temporally externalized through a retromastoid point for electrophysiologic confirmation of their placement. After target confirmation, stimulation parameters were set. Patients came for follow-up assessment of seizures and neurophysiologic tests every 3 months during an 18-month period of time; AED therapy was not modified. RESULTS The surgical procedure as well as electrical stimulation was well tolerated by all patients. No side effects occurred with the therapeutic stimulation parameters used, and patients were not aware of device activation. Two patients were explanted because of repeated and multiple skin erosions that could not be controlled by plastic surgery procedures. Overall seizure reduction was 80%. The three patients with poorest outcomes for seizure control did not improve their ability scale score. In contrast, the two patients rendered seizure free are living a normal life at present. The remaining eight patients experienced progressive improvement, from being totally disabled to becoming independent in five cases and partially dependent in two. Patients with adequate electrode placement had a seizure reduction >87%. To consider that an electrode is correctly placed, both stereotactic placement and neurophysiologic responses are taken into account. CONCLUSIONS ESCM provides a nonlesional, neuromodulatory method with improvement in seizure outcome and in the abilities of patients with severe LGS.