Neuropsychological significance of anosmia following traumatic brain injury.

OBJECTIVES: To investigate the incidence of anosmia following traumatic brain injury (TBI) using a standardized instrument and to test hypotheses that post-TBI anosmics perform significantly more poorly than do post-TBI normosmics on measures of executive skills and functional outcome.
DESIGN: Prospective quasi-experimental between-groups design. PARTICIPANTS: Sixty-eight adults diagnosed with TBI.
SETTING: Brain injury rehabilitation program based at a Midwestern medical center. MAIN OUTCOME MEASURES: University of Pennsylvania Smell Identification Test (UPSIT), selected neuropsychological measures of executive skills, the Disability Rating Scale (DRS), and the Community Integration Questionnaire (CIQ).
RESULTS: Forty-four subjects (65%) demonstrated impaired olfaction; only 13 (30%) acknowledged smell dysfunction. Anosmic and normosmic groups did not differ in demographics, IQ, chronicity, or admission Glasgow Coma Scale (GCS). Anosmics had longer coma (P =. 01), more severe deficits in complex attention (Trailmaking Test, Part B, P =.01), new learning/memory (California Verbal Learning Test Trial V [CVLT-V], P =.001), and problem solving (Wisconsin Card Sorting Test [WCST], P =.001), leading to greater functional impairment (Disability Rating Scale [DRS], P =.003). No differences emerged on the CIQ.
CONCLUSIONS: Anosmia is a common sequela of TBI, although only a minority of patients are aware of this deficit. Further, anosmics demonstrated greater impairment in a variety of frontal-lobe mediated executive functions, as well as greater functional disability.