The impact and prospect of traumatic brain injury on olfactory function: a cross-sectional and prospective study

Traumatic brain injury (TBI) can cause olfactory loss. The aim of this cross-sectional and prospective study was to determine the prevalence of olfactory loss among 110 patients with TBI within 3 months after the trauma. In 81 patients (cross-sectional-group), olfactory function could be measured using the validated Sniffin' Sticks test for odor threshold and odor identification. In addition, the prospective change of olfactory function was studied in 36 patients (follow-up-group) by means of a validated odor threshold, discrimination and identification test. Olfactory function was significantly better in patients with TBI IA degrees compared to individuals with TBI IIA degrees and IIIA degrees. Clinically significant improvement of olfactory function was found in 36 % of the patients, most frequently during the first 6 months after the injury, in a median follow-up interval of 21 months. TBI IA degrees has in general no major effect on olfaction. In contrast, patients with TBI IIA degrees and IIIA degrees exhibit smell loss in 57 %. Chances for olfactory recovery were highest within the first 6 months after the trauma.