Olfactory dysfunction, gambling task performance and intracranial lesions after traumatic brain injury.

OBJECTIVE: To estimate the incidence of olfactory dysfunction across traumatic brain injury (TBI) severity and decision-making deficits with regard to intracranial lesions' location and laterality.

METHOD: A 1-year prospective study including 115 participants (16-55 years) with mild, moderate, and severe TBI. The Brief Smell Identification Test was used 3 months postinjury with a follow-up testing of olfactory dysfunction at 1 year. The Iowa Gambling Task (IGT) and 3 tasks of the Delis-Kaplan Executive Function System were administered 3-months postinjury. MRI was performed 1-year postinjury and TBI severity groups were then divided with respect to frontal, fronto-temporal, diffuse, and no lesions.

RESULTS: The incidence of olfactory dysfunction was estimated to be 22.3% at 3 months and 13.5% at 1 year. No significant differences were found on olfactory dysfunction across TBI severity at either check. Anosmia was identified in 10% with severe TBI and 3% with mild TBI. Olfactory dysfunction was associated with verbal fluency tasks. Repeated-measures analysis of variance revealed no significant effect over blocks on IGT, and no main group or interaction effects regarding TBI severity, lesions' location, or laterality. IGT performance at 3-months postinjury was deficient in 83% of persons with intracranial lesions and 71% of those without lesions.

CONCLUSIONS: Olfactory dysfunction is independent of TBI severity, showing improvements in one third of cases from 3- to 12-months postinjury. However, anosmia was related to TBI severity. There is evidence for marked decision-making deficits after TBI, all subgroups performed similarly and failed to develop an advantageous strategy over time.