Imaging Markers Predict Neuropsychologic Outcome After Pediatric TBI

VANCOUVER—Early reductions in N-acetylaspartate (NAA) after pediatric traumatic brain injury (TBI) predict neuropsychologic outcomes one year later, according to a study presented at the 45th Annual Meeting of the Child Neurology Society.

Researchers at Loma Linda University in California conducted a prospective study that looked at NAA levels. In a separate but related study, they found that hemorrhagic MRI brain lesions after pediatric TBI are associated with neurologic and neuropsychologic outcomes at one year.

NAA Levels

Barbara Holshouser, PhD, Professor of Radiology at Loma Linda University, and colleagues used MR spectroscopic imaging (MRSI) to assess NAA levels in 69 children with TBI. Patients were ages 4 to 18, had a Glasgow Coma Scale (GCS) score of 13 to 15, and had hemorrhage or contusion on imaging. Initial scans to assess NAA levels were conducted an average of 11.5 days after injury. Follow-up scans were conducted at one year. The researchers obtained mean NAA/creatine, NAA/choline, and choline/creatine ratios for each brain region. They also scanned 75 controls with no history of head injury.

Barbara Holshouser, PhD

Patients in the TBI group (n = 69) had an average age of 11.8, and 19 patients were female. Seventeen patients were injured in motor vehicle accidents, 22 patients were hit by a motor vehicle, and one patient was injured in a fight. The other patients were injured in accidents that involved all-terrain vehicles (six patients), falls (16 patients), sports (six patients), and boating (one patient). Patients in the control group (n = 75) had an average age of 12.5, and 39 were female.

Patients with TBI had significant decreases of NAA/creatine and NAA/choline in all brain regions, compared with controls. Patients with TBI were dichotomized by those with a 12-month Pediatric Cerebral Performance Category Scale (PCPCS) score of 1 (ie, normal) and those with a PCPCS score 2 to 5 (ie, with disability).

A logistic regression analysis using total and regional NAA/creatine ratios predicted dichotomized PCPCS, full-scale IQ, general memory, and general attention scores at one year.

“A reduction of NAA in the subcortical region, consisting of the basal ganglia, corpus callosum, and thalamus, showed the strongest, most significant correlations” with tests of visual spatial processing, attention, general memory, and immediate and delayed visual memory. “At the subacute stage, a reduction of NAA caused by neuronal loss or dysfunction is a sensitive marker of injury that can be used to predict long-term (12-month) neurologic and neuropsychologic outcomes,” the researchers concluded.

Hemorrhagic Lesions

Stephen Ashwal, MD, Professor of Pediatric Neurology at Loma Linda University, and colleagues presented the results of a related study that found that, among children with moderate or severe TBI or complicated mild TBI, hemorrhagic MRI brain lesions are associated with neurologic and neuropsychologic outcomes at one year.

Susceptibility weighted imaging (SWI) has improved the ability of MRI to detect and quantify micro- and macro-hemorrhagic lesions after TBI. Studies in children, however, had not included repeated long-term MRI combined with neurologic and neuropsychologic measures. Dr. Ashwal and colleagues conducted a study to assess the relationship of acute lesions with one-year neurologic and neuropsychologic outcomes.

The researchers included 74 patients with moderate or severe TBI (ie, GCS score of less than 13) or complicated mild TBI (ie, with hemorrhagic intracranial injury on CT). Patients underwent MRI at six to 18 days after injury and at one year to determine the number and volume of hemorrhagic brain lesions.

Patients had an average age of 11.4, and 53 were male. Injury mechanisms were assault (one patient), sports (six patients), falls (20 patients), and vehicular (47 patients). Initial median GCS score was 9. Mean initial SWI lesion number was 84.3, and mean initial SWI lesion volume was 10,810.6 cm3.

Thirty-six patients had severe TBI (ie, GCS score of 3 to 8). Patients with severe TBI had higher mean SWI lesion numbers and volumes and lower scores on neuropsychologic tests at 12 months. SWI lesions correlated with general 12-month outcome scores on the PCPCS, King’s Outcome Scale for Childhood Head Injury, and Barthel Activities of Daily Living Index.

Initial SWI lesions correlated with measures of general memory (Children’s Memory Scale) and attention (Test of Everyday Attention for Children), but not IQ. In addition, SWI lesion volume in the occipital lobe correlated with visual immediate memory and visual delayed memory scores. Lesions in the temporal lobe also correlated with visual delayed memory scores.

Total lesion number and volume decreased by approximately 50% over 12 months regardless of initial GCS score, and improvement in lesions was associated with improved neurologic outcomes, Dr. Ashwal and colleagues said.

—Jake Remaly