Abstracts

Rationale: Infantile spasms (IS) is a severe epileptic syndrome which is typically associated with poor neurocognitive outcomes. Interictal electroencephalogram (EEG) is frequently characterized by hypsarrhythmia, and interictal PET shows hypometabolism over regions associated with EEG abnormalities (Ann Neurol 1990; 27: 406-13). In the current study, we used interictal frequency-domain near infrared spectroscopy (FD-NIRS), and EEG to better understand the pathophysiology of IS and the possible neurovascular effect of anticonvulsant treatment, with the goal of identifying markers predictive of outcome as well as developing tools to more closely follow infants with IS. Methods: FD-NIRS and EEG were carried out in 3 infants (14 to 29 weeks of age) with IS, before and after the first administration of anticonvulsant treatment. Two infants (#1 and #2) had tuberous sclerosis complex and IS were treated with vigabatrin, and one infant (#3) had extensive right (R) hemispheric encephalomalacia and has been treated with corticotropin (ACTH). Quantitative cerebral hemispheric hemoglobin concentration (HbT) and oxygen saturation (StO2) were measured with FD-NIRS over 11 cerebral areas during pre and post-treatment recordings, allowing estimation of cerebral blood volume (CBV), and relative changes in cerebral metabolic rate of oxygen (CMRO2) (for methods see Ped Res 2007; 61: 546-51). Pre and post-treatment interhemispheric FD-NIRS changes were measured for each patient and compared to EEG abnormality asymmetries. Results: On pretreatment EEG, infant #1 had left (L) hemispheric slowing whereas the other two infants (#2 and 3) had L > R sharp waves and spikes. All infants were seizure-free at the time of post-treatment measurements. In infant #1, StO2 showed a significant relative decrease (t=4.4203; df=18; p=0.0003) in the L hemisphere after treatment, consistent with faster frequencies seen on post-treatment EEG. Infants #2 and 3 showed a significant relative decrease in L hemisphere CMRO2 (#2: t=5.11; df=16; p=0.0001; #3: t=3.51; df=3; p=0.04), as well as a tendency of relative decrease in L HbT, and CBV after treatment consistent with decreased spikes and sharp wave abnormalities. Amplitude and spectral EEG analyses are underway to better compare EEG and FD-NIRS results. Conclusions: This preliminary study suggests that FD-NIRS may provide useful information on hemispheric metabolism in infants with infantile spasms and shows a hemispheric association between EEG changes and cerebral oxygenation variations pre and post-treatment. The combined use of FD-NIRS, and EEG provides a noninvasive, portable and sedation-free tool to investigate neurovascular processes underlying IS, and to monitor the effects of treatment in infants.