Rationale: Prevalence of psychogenic non-epileptic seizures (PNES) has been increasingly recognized but clinicians lack tools to investigate and understand behavior symptoms beyond experience-based skills to elicit relevant narrative history. Video-EEG evaluation is relatively reliable, only when major clinical target events are captured. Startle reflexes represent loss of affect control, and share symptoms with PNES. Recent psychophysiological investigations have suggested precognitive affect modulation of microreflexes mediated by cranial nerves (CNMR). Early investigations of cerebral evoked potentials (EP) recognized CNMR with short latencies, but were limited in scope, failing to resolve uncertainties concerning EP generation. Clinical investigations of startle reflexes have largely been limited to acoustic stimuli, but CNMR can involve multiple sensory modalities. This preliminary study examined blink reflexes elicited by strobe flash stimuli, optic-trigeminal-facial MR (MRotf), in standard EEG setting. Methods: Standard scalp EEG electrode placements have included zygomatic-infraorbital pairs (ZY1 and ZY2) in addition to 10-20 System placements. Intermittent photic stimulation (IPS), presented as 1, 3, 6, 9, 12, 15, 18 and 21/s trains, was administered, unless contraindicated. Digital EEG were reviewed for MRotf, detected at periorbital electrodes placed over orbicularis oculi muscles (FP1, FP2, ZY1 and/or ZY2). MRotf consist of surface EMG entrainment with latency of 40-50 ms following photic stimuli (FIG) and are at times associated with eyelid flutter. Exaggerated MRotf consist of IPS-dependent EMG recruitment registered at multiple electrodes and/or clinical myoclonus (photomyogenous reflexes). Results: Of 275 standard EEG performed from January through March 2011, 123 included IPS. MRotf were seen in 80 (65 %) and not in 43 (35 %). MRotf involved one or combination of 4 periorbital electrodes, and were often bilaterally symmetrical. EMG transients were indistinct in 5, reflecting distance from EMG generators. Exaggerated MRotf were seen in 9. Generalized spike-wave discharges were seen independently of IPS in 6.Conclusions: MRotf were detected often during standard EEG with sparse surface coverage of orbicularis oculi muscles. CNMR can be graded, and latency variation is wide. Association of photomyogenous responses with alcohol withdrawal is well known. Stimulus configuration other than strobe flashes can be made more relevant to affect control and may facilitate psychophysiological investigations of provoked seizures.
FIG Legend:Left hemisphere EEG channels display non-habituating Mrotf, registered at ZYI and occipital entrainment with latency of 44 and 131 ms, respectively, measured following strobe flash stimulus. Patient was resting supine with eyes closed.