High-frequency electrical stimulation of the anterior thalamic nuclei increases vigilance in epilepsy patients during relaxed and drowsy wakefulness.

OBJECTIVE: High-frequency deep brain stimulation (DBS) of anterior thalamic nuclei (ANT) reduces the frequency and intensity of focal and focal to bilateral tonic-clonic epileptic seizures. We investigated the impact of high-frequency ANT-DBS on vigilance in epilepsy patients during relaxed and drowsy wakefulness, to better understand the effects and the mechanisms of action of this intervention in humans. METHODS: Four patients with different structural epileptic pathologies were included in this retrospective case-cohort study. Short- and long-term electroencephalography (EEG) was used to determine states of relaxed or drowsy wakefulness and the vigilance changes during stimulation-on and stimulation-off intervals. RESULTS: In relaxed, wakeful patients with eyes closed, the eyelid artifact rate increased acutely and reproducibly during stimulation-on intervals, suggesting an enhanced vigilance. This effect was accompanied by a slight acceleration of the alpha rhythm. In drowsy patients with eyes closed, stimulation generated acutely and reproducibly alpha rhythms, similar to the paradoxical alpha activation during eyes opening. The occurrence of the alpha rhythms reflected an increase in the vigilance of the drowsy subjects during ANT-DBS. SIGNIFICANCE: This is the first demonstration that ANT-DBS increases the vigilance of wakeful epilepsy patients. Our results deliver circumstantial evidence that high-frequency ANT-DBS activates thalamocortical connections that promote wakefulness.

Hypothalamic hamartoma: is the epileptogenic zone always hypothalamic? Arguments for independent (third stage) secondary epileptogenesis.

Gelastic seizures associated with hypothalamic hamartomas (HHs) are a clinicoradiologic syndrome presenting with a variety of symptoms, including pharmacoresistant epilepsy with multiple seizure types, electroencephalography (EEG) abnormalities, precocious puberty, behavioral disturbances, and progressive cognitive deterioration. Surgery in adults provides seizure freedom in only one third of patients. The poor results of epilepsy surgery could be explained by an extrahypothalamic epileptogenic zone. The existence of an independent, secondary epileptogenic area with persistent seizures after resection of the presumably primary lesion supports the concept of a "hypothalamic plus" epilepsy. "Hypothalamic plus" epilepsy could be related to either an extrahypothalamic structural lesion (visible on magnetic resonance imaging [MRI] or on neuropathology) or if the former is absent, to a functional alteration with enhanced epileptogenic properties due to a process termed secondary epileptogenesis. We report two patients with gelastic seizures with HH (gelastic seizures isolated or associated with dyscognitive seizures of temporal origin). Both patients underwent two-step surgery: first an endoscopic resection of the HH, followed at a later time by temporal lobectomy. Both patients became seizure-free only after the temporal lobectomy. In both cases, neuropathology failed to demonstrate a significant structural lesion in the temporal lobe. To our knowledge, for the first time, these two cases suggest the existence of independent secondary epileptogenesis in humans.

Clinical findings in sporadic Creutzfeldt-Jakob disease correlate with thalamic pathology.

The pathogenesis underlying the typical findings in Creutzfeldt-Jakob disease (CJD) such as periodic EEG changes or myoclonus is not fully understood. The thalamus possesses a high density of inhibitory neurones and serves as a crucial pacemaker of rhythmic EEG activity. As inhibitory neurones expressing parvalbumin (PV) are reduced in the cerebral cortex and hippocampus in sporadic CJD (sCJD), we studied the distribution and number of PV-immunoreactive neurones in sCJD thalami in order to determine whether damage to them could account for certain clinical findings. Immuno histochemical analysis was performed on the thalami from 21 sCJD patients and five controls. The number of PV+ neurones was counted in the thalamic nuclei and compared with clinical and molecular findings. In sCJD patients, PV+ neurones were significantly reduced in the ventrolateral posterior (VLp), ventrolateral anterior (VLa), anteroventral (AV), lateral dorsal (LD), mediodorsal (MD) and reticular (Re) thalamic nuclei (P < 0.05). The VLp was especially damaged in sCJD patients with homozygosity for methionine at codon 129 and scrapie prion protein (PrP(Sc)) type 1. Patients with typical EEG changes [periodic sharp wave complexes (PSWCs)] and myoclonus had a predominant loss of PV+ cells in the reticular thalamic nucleus. In conclusion, our data support the hypothesis that the damage to PV-immunoreactive neurones determines the generation of certain typical clinical features of CJD, i.e. PSWCs associated with myoclonus.