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 admis- sion 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 (Wiconsin 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.