Dysfunctional Brain Areas May Fuel Inattention in Absence Epilepsy
Major Finding: Functional magnetic resonance imaging correlated with EEG in children with absence epilepsy and matched healthy controls.
Data Source: Results from Continuous Performance Task test done by 34 children (aged 7 to 8 years) and 21 healthy controls
Disclosures: The study was supported by a National Institutes of Health, the Betsy and Jonathan Blattmachr family, and a Howard Hughes Medical Institute fellowship. The authors reported no conflicts of interest.
BOSTON — Interictal attention problems in children with absence epilepsy may be linked to functional aberrations in specific areas of the brain.
Matthew Vestal, a medical student and research fellow, and Dr. Hal Blumenfeld of Yale University, New Haven, Conn., and their colleagues found that, between seizures, the function of the medial and bilateral frontal cortices of patients with childhood absence epilepsy (CAE) was impaired during the performance of attention tasks.
This finding suggests that dysfunction in specific brain networks may play a role in the attention deficits in this population. If confirmed, the findings could lead to the development of innovative regional therapies targeted at improving impaired attention in CAE, which in turn could improve patients’ quality of life by minimizing school performance deficits, injury potential, and the social stigma associated with attentional problems, Dr. Blumenfeld said in an interview.
Absence seizures are characterized by 3- to 4-Hz spike-wave discharges on electroencephalogram (EEG) that cause impaired consciousness. In school-aged children, the disease is associated with attention problems and social dysfunction, he explained.
In 34 patients with CAE aged between 7 and 8 years and 21 age-, gender-, IQ-, and socioeconomically matched healthy controls, the investigators performed functional magnetic resonance imaging correlated with electroencephalography while the participants completed the Continuous Performance Task (CPT) test of attentional vigilance, Mr. Vestal reported at the annual meeting of the American Epilepsy Society.
The CPT test involves showing subjects a string of letters on a computer and instructing them to press a button whenever they see a particular stimulus letter. Behavioral performance during the CPT is measured by reviewing omission and commission errors and reaction time.
The investigators monitored all of the CAE subjects for seizure episodes with EEG during the CPT testing and adjusted for all seizure-related fMRI signal changes during CPT.
Subjects in the CAE group made more omission errors than did the control subjects, although there was no difference between the groups in commission errors or reaction time. “Our hypothesis is that brain areas such as the frontal lobes and anterior insula, which are important for normal attention, are not functioning properly in these children,” Dr. Blumenfeld said.
In both the CAE and control subjects, CPT-associated increases in fMRI blood-oxygen-level dependent (BOLD) signal were observed in the medial frontal cortex and the medial and anterior insula, whereas CPT-associated decreases in fMRI BOLD signal occurred in the bilateral medial and lateral parietal cortices.
“By knowing which brain areas are not working in [these] children, we hope treatments can be developed to improve the function of these areas and attention in these children,” Dr. Blumenfeld stated.
Absence seizures overlapped with areas of increased (red) and decreased (green) brain activity in a 12-year-old girl during fMRI imaging of attention tasks.
Source Courtesy Hal Blumenfeld, M.D., Ph.D. and Rachel Berman