Role of mesial temporal lobe structures in sensory processing in humans: a prepulse modulation study in temporal lobe epilepsy.

Prepulse modulation (PPM) is an electrophysiological method which enables to assess sensory processing in vivo. Reflex responses may be facilitated or inhibited (prepulse inhibition, PPI) after a weak stimulus. Theoretically, in animal studies, the generator of PPI involves pedunculopontine nucleus which is modulated by various structures, including amygdala. We aimed to investigate whether or not there was a role of limbic structures in the generation of PPM in humans. For this purpose, we studied PPM of the blink reflex (BR) in 10 patients with mesial temporal lobe epilepsy (MTLE group) and in nine patients who had previously undergone amygdala resection for medically resistant MTLE (surgery group). A control group including 19 healthy volunteers was formed. Blink reflex, BR-PPM and BR excitability recovery were recorded in all participants. Two components of BR, first early ipsilateral component (R1) and second late bilateral components (R2 and R2c) were identified. All BR parameters after single stimulation were normal in all groups. Compared to healthy subjects, R2-PPI was more pronounced in the surgery group whereas there was a R2-PPI deficit in the MTLE group. R2-PPI deficit in the MTLE group was more prominent on the lesion side. Ipsilesional R1 facilitation was more evident at ISI of 100 ms in both MTLE and surgery groups compared to healthy subjects. BR excitability recovery was not different between groups. MTLE in humans leads to a PPI deficit. Interestingly, removal of amygdala in humans with MTLE probably provides more efficient functioning of PPI network. Amygdala and hippocampus play roles in the human R2-PPI circuit. Modulation of R1 facilitation is unilateral whereas the modulation of R2-PPI is bilateral, though asymmetric.

Long-term follow-up of two siblings with adult-onset neuronal ceroid lipofuscinosis, Kufs type A.

Reports on the clinical presentation of adult-onset neuronal ceroid lipofuscinoses (NCL) are scarce compared to infantile- and childhood-onset forms. Here, we aimed to present detailed temporal evolution of clinical and electrophysiological features of two siblings with adult-onset NCL and homozygous mutation in the CLN6 gene. We retrospectively analysed medical records and electrophysiological data in order to delineate evolution of clinical and electrophysiological findings. Electrophysiological studies included routine EEG and video-EEG, as well as polymyographic analysis of myoclonus and brainstem reflex studies. Both patients had seizures and cerebellar signs. Despite the slow progression of ataxia, they developed no mental deterioration, but had severe obsessive compulsive disorder and depression. EEG revealed frequent generalized spikes, polyspikes, and waves, prominent on awakening and during photic stimulation without significant change throughout the clinical course. Abnormalities concerning the blink reflex, auditory startle response, and startle response to somatosensory inputs manifested within four years. The patients underwent transient and mild improvement with valproate, whereas ataxia and seizures were dramatically ameliorated following high-dose piracetam. Patients with adult-onset NCL may present with slowly progressive ataxia, persistent photosensitivity, and seizures without dementia or extrapyramidal findings. Brainstem abnormalities become more evident with time, in line with ataxia. Piracetam is effective for both seizures and ataxia.