Relationships between olfactory discrimination and head injury severity

The goal of this study was to examine the relationship between brain injury severity and scores on both an olfactory identification test and on many widely used neuropsychological tests in 367 patients with head injuries of varying levels of severity. It was hypothesized that valid olfactory test scores would correlate highly with injury severity because both the olfactory nerves and the primary olfactory cortices are especially vulnerable to damage in closed head injury. After removing data of doubtful validity from cases failing effort tests, olfactory test scores were related to Glasgow Coma Scale scores (GCS), post-traumatic amnesia and radiological abnormalities more strongly than any of the neuropsychological test scores. Based on the assumption that post-traumatic amnesia is caused by a different mechanism than loss of core consciousness, it was also predicted that there would be no cases with a GCS less than 13 and with no post-traumatic amnesia. As predicted, there were no cases in this group. The results support previous studies showing greater olfactory impairment with increased severity of head injury.