Risk factors for unsuccessful testing during the intracarotid amobarbital procedure in preadolescent children

Identification of risk factors for unsuccessful testing during intracarotid amobarbital procedure (IAP) in preadolescent children.

A pediatric IAP protocol was attempted in 42 candidates for epilepsy surgery (5-12 years old; mean, 10 years) based on the ability to pass a practice test. Language dominance was defined by marked asymmetry until first verbal response and paraphasic errors. Intact hemispheric memory was defined by recall of >/=60% of test items. The odds ratios of baseline variables (age at IAP, Full-Scale IQ, side of disease, age at seizure onset, amobarbital dose) were calculated for various IAP outcomes.

IAPs were accomplished in 40 children. Language dominance was established in 25 (62.5%) of 40 patients: all 21 focal resection candidates were left language dominant; four hemispherectomy candidates had intact language after injection of the damaged hemisphere. In 12 (30%) of 40 patients, language testing failed because of agitation or obtundation. Compared with the 21 children with language dominance established by bilateral IAP, these 12 children had lower mean Full-Scale IQ (66.4 vs. 87.9; p = 0.014), and more frequently, the epileptogenic lesion in the left hemisphere (presumed dominant by right-handedness; 78 vs. 33%; p = 0.04). Excluding hemispherectomy candidates (intentionally only one injection), memory testing could not be completed in 13 (36%) of 36 children because of obtundation or agitation. These children were significantly younger than the 23 (64%) of 36 with successful bilateral memory testing (mean age, 107.6 vs. 128.7 months; p = 0. 006). The eight (25%) of 32 children with failing retention scores after ipsilateral injection had lower Full-Scale IQ than did the 24 (75%) patients who passed (mean, 59.6 vs. 81.7 months; p = 0.03).

The IAP successfully established hemispheric language dominance and memory representation for just under two thirds of the preselected preadolescent children. Risk factors for unsuccessful testing included low Full-Scale IQ (especially <80), young age (especially <10 years), and seizures arising from the left hemisphere presumed dominant by right-handedness.