The significance of post-traumatic amnesia as a risk factor in the development of olfactory dysfunction following head injury.

OBJECTIVE: To test the following hypothesis in the assessment of head injury PATIENTS: only patients with 5 min or more of post-traumatic amnesia (PTA) are at risk of acute olfactory dysfunction (OD). METHODS: This was a retrospective comparative study of olfactory status in head injury patients seen at a head injury clinic at Glasgow Royal Infirmary from 1985 to 2003. Of 828 clinic attenders, 101 had acute OD. These subjects were compared with a randomly selected control group of 102 patients with head injury but normal olfactory function. The main outcome measure was a significant likelihood of patients with PTA lasting for 5 or more minutes having acute OD compared with those with PTA of less than 5 min. RESULTS: The likelihood of patients with a PTA of 5 min or more having acute OD compared to those with PTA of less than 5 min is clinically significant with an odds ratio of 9.6 (p<0.01). CONCLUSION: Examination of patients with 5 min or more of PTA should include a simple test of sense of smell. Patients with impaired smell sensation should be aware of their condition prior to discharge from hospital. In addition, the need for a CT brain scan and appropriate follow up should be considered.