Abstracts

Brief episodes of loss of consciousness pose a diagnostic dilemma. Episodes of syncope or breath holding spells (BHS) are often misdiagnosed as epileptic events. The purpose of this study is to assess the usefulness of EEG with ocular compression (OC) to distinguish BHS/syncope from seizures. OC is routinely performed in our EEG laboratory if the clinical history is suggestive of either BHS or syncope. A retrospective analysis was performed on EEG records of all children on whom OC was performed from 2000-2003. Data from 116 (mean age 9.4 years [plusmn] 5.8 SD) patients with a clinical diagnosis consistent with syncope or BHS were compared with a control group of 46 patients (mean age 7.5 years [plusmn] 4.7 SD) who had EEGs requested for indications other than syncope or BHS. A physician performed 10 seconds of forceful OC during EEG and EKG recording for both groups of children.
Baseline RR (RR-B) interval was measured with the patient at rest and was compared to the maximum prolongation of RR interval during ocular compression (RR-OC). At baseline, the BHS/syncope group had a lower RR-B than controls (means [plusmn] SD = 0.73 [plusmn] 0.2 and 0.8 [plusmn] 0.22 respectively; p = 0.043 by unpaired t-test).
The RR-OC was significantly higher in BHS/syncope group than controls (means [plusmn] SD = 0.88 [plusmn] 0.32 and 1.73 [plusmn] 1.53 respectively; p [lt] 0.005 by Mann Whitney U).
Using the accepted standard of 2 seconds of asystole as the cut off, the sensitivity of OC was 26% with 100% specificity. Setting the threshold of RR-OC at 1.3 seconds increased the sensitivity to 45 % while maintaining a specificity of 93%.
The change in RR interval from RR-B to RR- OC also distinguished patients from controls. A 1.36 second increase in RR interval achieved a sensitivity of 25 % with a specificity of 100 %. Even a small increase of 0.2 seconds in RR interval demonstrated a sensitivity of 71% with a specificity of 89 %.
No complications were noted during, or subsequent to performance of OC. OC during EEG is useful in distinguishing patients with BHS/syncope from those with epileptic seizures. A requirement of a 2 second period of asystole with OC excludes many patients. Our data indicate that RR interval increase of 0.2 seconds over baseline identifies additional patients with increased vagal tone. Prompt and accurate diagnosis of the etiology of loss of consciousness may preclude the need for further extensive and expensive evaluation and reduce both patient and parental distress.