Nociceptive inputs transmission in Huntington's disease: a study by laser evoked potentials.

The aim of the present study was to evaluate pain perception and evoked responses by laser stimuli (LEPs) in mild not demented Huntington's Disease (HD) patients. Twenty-eight HD patients and 30 control subjects were selected. LEPs were obtained by four scalp electrodes, (Fz, Cz, referred to the nasion; T3, T4, referred to Fz), stimulating the dorsum of both hands. All patients were also evaluated by somatosensory evoked potentials (SEPs) by median nerve stimulation. Only 3 patients referred pain of arthralgic type. Laser pain perception was similar between HD patients and controls. An abnormal N2, P2 and N1 latency increase was evident in the majority of HD patients. LEPs features were similar between patients taking and not taking neuroleptics. The N2 and P2 latencies, showed a negative correlation with functional score and Mini Mental State Examination, and a positive correlation with the severity of hyperkinetic movements. A delay in nociceptive input processing emerged in HD, concurring with the main features of the disease, in absence of clinical evidence of abnormalities in pain perception. The dysfunction of pain signals transmission in HD may induce sub-clinical changes of sensory functions, which may probably interfere with sensory-motor integration and contribute to functional impairment.

Detection of subclinical brain electrical activity changes in Huntington's disease using artificial neural networks.

OBJECTIVE: The aim of this study was to analyze EEG background activity in Huntington's disease (HD) patients and relatives at risk, in relation to CAG repeat size and clinical state, in order to detect an electrophysiological marker of early disease. METHODS: We selected 13 patients and 7 subjects at risk. Thirteen normal subjects, sex- and age-matched, were also evaluated. Artifact-free epochs were selected and analyzed through Fast-Fourier Transform. EEG background activity was tested using both linear analysis and artificial neural network (ANN) classifier in order to evaluate whether EEG abnormalities were linked to functional changes preceding the onset of the disease. RESULTS: The most important EEG classification pattern was the absolute alpha power not correlated with cognitive decline. The ANN correctly classified 11/13 patients and 12/13 normals. Moreover, the neural scores for subjects at risk seemed to be correlated to the expected time before the onset of the disease. CONCLUSIONS: ANN is a very powerful method to discriminate between normals and patients. It could be used as an automatic diagnostic tool. EEG changes in positive gene-carriers for HD confirm an early functional impairment which should be taken into account in the genetic counseling and in the management of the early stages of the disease.

Interictal lack of habituation of mismatch negativity in migraine.

The aim was to study mismatch negativity features and habituation during the interictal phase of migraine. In migraine patients, a strong negative correlation has been found between the initial amplitude of long latency auditory-evoked potentials and their amplitude increase during subsequent averaging. We studied 12 outpatients with a diagnosis of migraine without aura recorded in a headache-free interval and 10 gender- and age-matched healthy volunteers not suffering from any recurrent headache. The experiment consisted of two sequential blocks of 2000 stimulations, during which 1800 (90%) recordings for standard tones and 200 (10%) for target tones were selected for averaging. The latency of the N1 component was significantly increased in migraine patients in respect of controls in both the first and second repetitions; the MMN latency was increased in the second repetition. In the control group the MMN amplitude decreased on average by 3.2 +/- 1.4 microV in the second trial, whereas in migraine patients it showed a slight increase of 0.21 +/- 0.11 microV in the second repetition. The MMN latency relieved in the second trial was significantly correlated with the duration of illness in the migraine patients (Spearman correlation coefficient: 0.69; P < 0.05). The increases in N1 latency and MMN latency and amplitude, the latter correlated with duration of illness, seemed to be due to a reduced anticipatory effect of stimulus repetition in migraine patients. This suggests that such hypo-activity of automatic cortical processes, subtending the discrimination of acoustic stimuli, may be a basic abnormality in migraine, developing in the course of the disease.

Features of the blink reflex in individuals at risk for Huntington's disease.

The aim of the study was to correlate the features of the blink reflex (BR) with the genetic abnormalities and the clinical findings in patients with Huntington's disease (HD) and asymptomatic gene carriers. Twenty patients with HD and 20 relatives were studied. Mutation analysis was performed for the CAG expansion within the HD gene using HD 333-HD 447 as oligonucleotide primers. The BR was elicited transcutaneously by electrical stimulation of the right supraorbital nerve. The recovery curve of the R2 and R3 responses after a conditioning stimulus was evaluated. R2 latency and duration and R3 duration were significantly increased in HD patients and in presymptomatic carriers in comparison with controls; reduced R2 recovery was also clear in both HD and gene-carrier relatives. In HD patients, the R2 latency increase correlated significantly with the severity of facial chorea. The R2 abnormalities are probably caused by impaired suprasegmental control by the basal ganglia over brainstem interneurons, which may precede the onset of involuntary movements, probably conditioning the severity of facial chorea during development of the disease.