Noninvasive Tests Help ID Seizure Site in Children with Focal Epilepsy

Marla Hamberger, PhD

Naming tasks, which have helped to localize and lateralize a seizure onset region for surgery of focal epilepsy in adults, could now be as useful in children, with the recently reported success of a novel, age-specific assessment.

Marla Hamberger, PhD, Director of Neuropsychology, Columbia Comprehensive Epilepsy Center, Columbia University Medical Center, and Professor of Neuropsychology, Department of Neurology, Columbia University, New York, and colleagues posited that neuropsychological assessment with naming tasks have been less reliable in lateralizing the epileptogenic region in children than adults because test designs were not age-appropriate, rather than for age-related differences in neurodevelopment or neuropathology.

"Interestingly, failure to find lateralized deficits in children with previous measures had been interpreted to reflect that language process in children were not yet lateralized or localized," Hamberger told MD Magazine®.

Hamberger and colleagues had previously improved the sensitivity of naming tasks in adults by posing auditory descriptions in addition to the visual depictions which had traditionally been used. They subsequently developed and validated the novel Children's Auditory Naming Test (ANT) and Children's Visual Naming Tests (VNT), and have now investigated whether these tests, designed specifically for use with children, could provide clinically relevant laterality results to facilitate surgery for their focal epilepsy.

"In adults, we found that adding auditory description naming, as well as a timing component (in contrast to untimed response) to the performance measures, increases the sensitivity of the naming assessment," Hamberger explained. "We then reasoned that perhaps it is not that tests cannot be used in children to assist with lateralization, but rather, age-appropriate, more sensitive measures are needed. And, this proved to be the case."

The investigators identified 78 children, aged 6 through 15 years of age with unilateral epilepsy (44 with left hemisphere lateralization), including a subgroup with the less prevalent temporal lobe epilepsy (TLE) (23 left TLE, 14 right TLE). Study participants were required to be left hemisphere language-dominant (confirmed with functional magnetic resonance imaging), native English speakers or fluent in English by age 5, and without history of head injury or neurologic disorders other than epilepsy.

The battery of neuropsychological and cognitive measures administered to the children included the ANT and VNT, as well as the Boston Naming Test (BNT)—a widely used measure of visual object naming that was developed for adults. Testing results were analyzed for significant correlations with groups and the individual children with left vs right hemisphere seizures, to ascertain measures that could consistently inform surgical intervention.

The investigators found that the left and right hemisphere epilepsy groups and individuals could be statistically significantly distinguished with the Children's ANT, but not the VNT. This finding remained in the analysis of the TLE subgroup, albeit with statistical power limited by the smaller sample. In addition, results in testing with a timed component demonstrated that response latency rather than untimed accuracy was critical for assessing capacity for word finding, and, therefore, for accurately identifying onset lateralization.

In an accompanying editorial, Bruce Herman, PhD, Department of Neurology, University of Wisconsin School of Medicine and Public Health, Madison, WI, and Benjamin Tolchin, MD, MS, Epilepsy Center of Excellence, VA Connecticut Healthcare System, West Haven, and Comprehensive Epilepsy Center, Yale University School of Medicine, New Haven, CT, characterized the intent of the investigation as "sound" and its methodologic quality as "high".

Herman and Tolchin also credited this report for countering previous assumptions and for demonstrating that auditory naming performance can lateralize seizure onset in children if the instrument is developmentally appropriate.

"This finding is an important step toward an expanded role of neuropsychological testing in the preoperative workup of candidates for pediatric epilepsy surgery," Herman and Tolchin declared.

The investigators plan to follow on their successful outcome, according to Hamberger.

"In our next study, we'll recruit a new, larger cohort of children with focal epilepsy, and hope to be able to examine subgroups such as TLE, frontal lobe epilepsy," Hamberger said. "We also plan to retest many of the children tested in this original study, some of whom will have had epilepsy surgery."

The study, “Noninvasive Identification of Seizure Lateralization in Children,” was published in Neurology.