Oculomotor phenomena in petit-mal

The yield of video-EEG telemetry evaluation for non-surgical candidate children

BACKGROUND

Video EEG (VEEG) is performed for most pediatric patients in order to evaluate unclear paroxysmal events and improve our understanding of difficult to control epileptic patients.

PURPOSE

To characterize the video EEG studies on children who are not candidates for surgery in order to identify the parameters that affect results in level of improving the rate of acquisition, as well as improving the ability to expect the likelihood of epilepsy and of gathering new information as a result of the VEEG.

METHODS

Retrospective chart analysis of all consecutive patients who underwent VEEG in two VEEG monitoring units.

RESULTS

323 children of a mean age of 7 years (STD 4.73, range 0-17 years) were monitored for a mean duration of 2 days (STD 1.65, range 1-10 days). The main reasons for monitoring were: evaluation of unclear events (n = 234), evaluation of previously diagnosed epilepsy (n = 36) and confirmation of Electrical Status Epilepticus in Sleep (ESES) (n = 34). The main event types for evaluation were: staring episodes (n = 67), myoclonic jerks (n = 35) and abnormal eye movement (n = 22). Suspected events were captured in 70% of the patients. There was a positive correlation between acquisition of suspected events and each of the following: duration of the monitoring, the frequency of investigated events per history, the type of investigated events. A prior interictal epileptic activity on routine EEG was a positive predictor of an event to be epileptic (p = 0.003). Amongst the group of known epileptic patients, VEEG had role in changing diagnosis in 53% of patients. Many of them had focal interictal epileptiform activity in their routine EEG.

CONCLUSIONS

Selecting patients with frequent events and longer monitoring periods increase the yield of VEEG. Looking carefully into clinical characteristics of the patient prior to VEEG can clarify diagnosis therefore render the VEEG test superfluous to subgroups of patients. Prior routine epileptic EEG, coexistence of other seizure types, behaviors accompanying the investigated habitual behavior and abnormalities in other investigations (MRI, cognitive function and EEG) are the parameters that can predict diagnosis of epilepsy. Precise diagnosis in known epileptic patients as a result of VEEG is more likely for those with focal interictal epileptiform discharges in routine EEG.

The zona incerta modulates spontaneous spike-wave discharges in the rat

The contribution of the zona incerta (ZI) of the thalamus on spike-wave discharges (SWDs) was investigated. Chronic recordings of bilateral cortices, bilateral vibrissa muscle, and unilateral ZI were performed in Long-Evans rats to examine the functional role of SWDs. Rhythmic ZI activity appeared at the beginning of SWD and was accompanied by higher-oscillation frequencies and larger spike magnitudes. Bilateral lidocaine injections into the mystacial pads led to a decreased oscillation frequency of SWDs, but the phenomenon of ZI-related spike magnitude enhancement was preserved. Moreover, 800-Hz ZI microstimulation terminates most of the SWDs and whisker twitching (WT; >80%). In contrast, 200-Hz ZI microstimulation selectively stops WTs but not SWDs. Stimulation of the thalamic ventroposteriomedial nucleus showed no obvious effect on terminating SWDs. A unilateral ZI lesion resulted in a significant reduction of 7- to 12-Hz power of both the ipsilateral cortical and contralateral vibrissae muscle activities during SWDs. Intraincertal microinfusion of muscimol showed a significant inhibition on SWDs. Our present data suggest that the ZI actively modulates the SWD magnitude and WT behavior.

Diagnostic yield of electroencephalograms in infants and young children with frequent paroxysmal eye movements

Paroxysmal eye movement events are common in children. Many infants and young children are referred for a routine or a video-electroencephalography study. When epileptic, these events form part of a seizure and rarely occur as an isolated ictal event. The yield of the electroencephalogram in determining the nature of isolated paroxysmal eye movement episodes has not been reported. We reviewed our experience with video-electroencephalography studies in patients referred for paroxysmal eye movements. Twenty-one cases were analyzed, of which almost half were cognitively normal. All video-electroencephalography studies captured events that were found to be nonepileptic, including 6 records with interictal epileptiform activity. The semiology of the events differed between cognitively impaired individuals, who had more lateral eye deviation episodes, and normal patients, who showed blinking as a major manifestation. In conclusion, video-electroencephalography studies are probably not indicated in infants and young children with paroxysmal eye movements as their sole complaint.