To determine the incidence of olfactory dysfunction after head trauma
using clinical and radiologic findings, quantitative assessment, and electro-physiologic methods.
A total of 190 patients with head trauma
of different severity (n
= 32 with mild traumatic brain injury
= 94 with signs of moderate TBI, and n
= 64 with severe TBI) 6 to 32 months prior to the study.
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
= 19) and olfactory-evoked potential recording (n
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.
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.