Olfactory dysfunction after head injury.

OBJECTIVE

To determine the incidence of olfactory dysfunction after head trauma using clinical and radiologic findings, quantitative assessment, and electro-physiologic methods.

PARTICIPANTS

A total of 190 patients with head trauma of different severity (n = 32 with mild traumatic brain injury (TBI), n = 94 with signs of moderate TBI, and n = 64 with severe TBI) 6 to 32 months prior to the study.

DESIGN

Patients were selected retrospectively, surveyed by telephone (n = 190), and screened for olfactory function with Brief Smell Identification Test (n = 82). Those with olfactory dysfunction were assessed as outpatients using the Sniffin' Sticks (n = 19) and olfactory-evoked potential recording (n = 16).

RESULTS

Twenty-one participants (11%) reported a decreased sense of smell after trauma. The incidence of olfactory dysfunction after head injury was 12.8%. The results of the odor-evoked potentials were heterogeneous. A significant correlation was found between olfactory dysfunction and the appearance of skull base fractures and intracranial hemorrhage or hematoma.

CONCLUSION

The site of trauma may be more relevant to prognosis than a simple probability (of olfactory loss) based on incidence. Odor-evoked potentials indicate that functional anosmia can occur even when there is some evidence of intact olfactory nerve function.