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.