Acute subcortical stroke and early serotonergic modification: a IDAP study.

The intensity dependence of the auditory-evoked potentials (IDAP) is inversely related to serotonergic tone. Depression is frequently observed after stroke, associated with cognitive impairment and increased mortality. Aim of this study was to investigate the serotonergic tone in acute stroke patients by IDAP. Consecutive patients with an acute stroke admitted in our stroke unit were evaluated using clinical and instrumental examinations and compared with healthy controls. The IDAP was calculated as the linear amplitude/stimulus intensity function (ASF) slope, by measuring the peak-to-peak amplitude of Nl-P2 on four blocks of different stimulus intensities. Twenty patients were enrolled; 11 had a right brain infarction; nine had depressive symptoms (DS). The ASF slope of the auditory-evoked potentials was markedly increased in stroke patients compared with controls (P = 0.021). Stroke patients with DS had a significant steeper ASF slope than controls (P = 0.017). There was no statistical difference in ASF slope between stroke patients without DS and controls. Post-stroke depression pathophysiology is still debated. Our study suggests that in acute stroke patients with DS, there is a direct involvement of the serotonergic system, regardless the degree of disability and the site of the lesion.

Comparison of visual and auditory evoked cortical potentials in migraine patients between attacks.

OBJECTIVE: As both habituation of pattern reversal visual evoked potentials (PR-VEP) (Schoenen J, Wang W, Albert A, Delwaide PJ. Potentiation instead of habituation characterizes visual evoked potentials in migraine patients between attacks. Eur J Neurol 1995;2:115-122) and intensity dependence of auditory evoked cortical potentials (IDAP) (Wang W, Timsit-Berthier M, Schoenen J. Intensity dependence of auditory evoked potentials in migraine: an indication of cortical potentiation and low serotonergic neurotransmission? Neurology 1996;46:1404-1409) were found abnormal in migraine between attacks, we have searched for intraindividual correlations between both tests in 59 migraine patients (22 with aura [MA], 37 without aura [MO]) and in 23 healthy volunteers (HV). METHODS: Amplitude change of the PR-VEP N1-P1 was measured between the 1st and 5th block of 50 sequential averagings during continuous stimulation at 3.1 Hz. IDAP was computed from N1-P2 amplitudes of 100 averagings during stimulations at 40, 50, 60 and 70 dB SL. Amplitude-stimulus intensity function (ASF) slopes and amplitude changes between 40 and 70 dB were calculated. MO and MA differed from HV in PR-VEP amplitude change (P=0.007) and IDAP slope (P = 0.0004). RESULTS: There was no significant correlation between VEP amplitude changes and IDAP slopes, nor between the latter two and attack frequency or disease duration. A negative correlation was found between the amplitude of the first block of averaged responses and potentiation of VEP in all subject groups (P = 0.03) as well as between the amplitude of the auditory evoked potential, at 40 dB, and the percentage of amplitude increase between 40 and 70 dB in MO (P = 0.004) and MA (P = 0.007). ASF slopes and 40 dB amplitudes were significantly correlated only in the MA group (P = 0.002). These results confirm the interictal deficit of habituation in cortical processing of repetitive visual and auditory information in migraine. Since there is no intraindividual correlation between the cortical responses to these sensory modalities they are complementary tools for the study of migraine and may help to identify subgroups of patients with distinct pathophysiological mechanisms. CONCLUSIONS: The strong negative correlation between the initial amplitude of evoked potentials and their amplitude increase during subsequent averaging confirms that the response potentiation in migraine is likely to be due to a reduced preactivation level of sensory cortices.