NeuroSPECT findings in patients with posttraumatic anosmia: a quantitative analysis.

OBJECTIVE

To investigate quantitative neuroSPECT findings, particularly from orbital frontal cortex, in patients rendered totally anosmic from head injury.

SETTING

Veterans Administration (VA) Medical Center.

SUBJECTS: Eighteen patients with head injury resulting in severe anosmia and five normal controls. All 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 interest (ROIs) ranging circumferentially from orbital frontal cortex to occipital pole.

RESULTS

Quantitative evaluation of neuroSPECT findings for anosmic patients as a group showed substantial orbital frontal hypoperfusion compared with controls, with 67% of individual anosmic patients showing orbital frontal hypoperfusion at a level two or more standard 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 abnormalities were infrequent in these areas. In addition, orbital frontal count was significantly correlated with ratings of outcome, the only ROI to have such a relationship.

CONCLUSIONS

Findings strongly suggest that posttraumatic anosmia and the neuropsychological deficits typically associated with posttraumatic anosmia are closely and specifically associated 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 patients with mild head injury who have normal computed tomography and magnetic resonance imaging scans.