NEUROSPECT FINDINGS IN PATIENTS WITH POSTTRAUMATIC ANOSMIA - A QUANTITATIVE-ANALYSIS

Objective: To investigate quantitative neuroSPECT findings, particular ly from orbital frontal cortex, in patients rendered totally anosmic f rom head injury. Setting: Veterans Administration (VA) Medical Center. Subjects: Eighteen patients with head injury resulting in severe anos mia and five normal controls. Al 18 patients had sustained their head injuries at least 5 years prior to involvement in the study. Measures: Quantitative neuroSPECT (count density) from sagittal regions of inte rest (ROIs) ranging circumferentially from orbital frontal cortex to o ccipital pole. Results: Quantitative evaluation of neuroSPECT findings for anosmic patients as a group showed substantial orbital frontal hy poperfusion compared with controls, with 67% of individual anosmic pat ients showing orbital frontal hypoperfusion at a level two or more sta ndard deviations below that of the worst control subject. By contrast, there were no between-group differences for five other ROIs (inferior frontal pole, superior frontal pole, posterior superior frontal lobe, the parasagittal region, and occipital pole), and individual abnormal ities were infrequent in these areas. In addition, orbital frontal cou nt was significantly correlated with ratings of outcome, the only ROI to have such a relationship Conclusions: Findings strongly suggest tha t posttraumatic anosmia and the neuropsychological deficits typically associated with posttraumatic anosmia are closely and specifically ass ociated with hypoperfusion in orbital frontal cortex. The results also underscore the importance of posttraumatic anosmia as a clinical sign of orbital frontal damage, which is particularly important in patient s with mild head injury who have normal computed tomography and magnet ic resonance imaging scans.