Post-traumatic anosmia in patients with mild traumatic brain injury (mTBI): A systematic and illustrated review

BACKGROUND: Olfactory dysfunction (OD) is a disorder associated with traumatic brain injury (TBI), which is prevalent in up to 20% of patients suffering from TBI. Nevertheless, most studies focusing on the relationship between OD and TBIs do not differentiate between the different types of TBI (mild, medium, and severe). In this paper, we conducted a comprehensive and systematic review of the existing literature for the association between mild TBI (mTBI) and OD in order to examine their relationship, focusing on its neurosurgical management and the radiographic characteristics. METHODS: The MEDLINE database was systematically reviewed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. We found 66 articles, of which 10 fulfilled our criteria. RESULTS: All except two studies reported a significant association between trauma severity and olfaction. Two studies found a negative correlation between TBI severity and olfactory bulb volume with one reporting an r value of -0.62). Three studies reported an association between the observation of radiographic intracranial hemorrhage or skull base fractures and the history of TBI. CONCLUSION: According to our search results, we conclude that OD is a prevalent but underdiagnosed problem in mTBI. Because OD is associated with a significant decrease in quality of life, we think that neurosurgical teams need to asses olfactory function in mTBI patients when they report to clinics. To illustrate this scenario, we include two distinct cases of patients with anosmia after mTBI in this review. Finally, we suggest a treatment algorithm for patients with mTBI so that a possible OD can be diagnosed and treated as early as possible.