Bilateral centrotemporal spikes triggered by blinking: an unusual form of sensory input with related cortical EEG activity.

OBJECTIVE

To investigate the morphology, scalp topography and temporal relationship with orbicularis oculi muscle contraction of bilateral blink related spikes (BRS) in a 7-year-old boy with chromosomopathy, mild mental retardation and left spontaneous centrotemporal spikes (SS).

METHODS

The patient underwent video-polygraphic recordings with off-line analysis of SS and BRS by means of spike-averaging and orbicularis oculi contraction-locked averaging techniques respectively. EEG activity related to reflex blinking (evoked by glabellar tapping) was also studied.

RESULTS

SS and BRS presented the same morphology, characterised by four peaks (P1, N1, P2, N2). SS were located over the left centroparietal regions, while BRS were placed over both left and right centrotemporoparietal regions and constantly followed the contraction of orbicularis oculi with overlapping peak latencies over C3 and C4 electrodes (P1 72 ms; N1 115 ms; P2 164 ms; N2 236 ms). Reflex blinking evoked a small waveform with the same features as BRS.

CONCLUSIONS

Our findings suggest that both involuntary and reflex blinking can act as a form of sensory stimulation probably engaging similar nervous pathways and cortical sources in generating EEG abnormalities: the trigeminal system.