Mild traumatic brain injury can lead to olfactory dysfunction

Neurophysiologists at Université de Montréal (Montreal, Canada) discover olfactory and affective problems could be caused by minor concussion.

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It is known that patients who suffer major concussion can lose their sense of smell and develop affective problems such as anxiety and depression. Recently, it has been found that this is also true for those with minor concussion, minor accidents can cause same kind of olfactory problems. 

A cross-sectional study conducted by neuropsychologists at Université de Montréal (Montreal, Canada) and published in Brain Injury aimed to evaluate olfaction after a mild traumatic brain injury (TBI). 

Fanny Lecuyer Giguère (Université de Montréal, Montreal, Canada) visited patients with mild concussion in the alpine ski resort hospital of Visp, Switzerland to test their capacity to identify smells. Most of the mild concussion patients had been in a skiing accident and were all seen 24 hours following their accident, as were patients with fractures but no concussion. Twenty patients with mild TBI were compared with 22 who had broken limbs but no concussion, who acted as controls. 

Using scented ‘Sniffin’ sticks (felt-tip pens), patients were asked to identify synthetic odors of roses, garlic, cloves, solvent and more. After 24 hours of their accident patients with mild TBI demonstrated significantly reduced olfactory function, compared with controls, with 55% of TBI patients presenting signs of hyposmia. 

A year later patients were followed up with a questionnaire and a set of scratch-and-sniff booklets, from this the researchers were able to determine that most patients who had lost their sense were able to regain their sense within 6 months of their accident. 

However, the TBI patients who previously presented symptoms of hyposmia displayed significantly higher levels of anxiety and more post-concussion symptoms when compared with TBI patients who did not present hyposmia symptoms, with approximately 65% of concussed patients reporting symptoms of anxiety.  

"A lot of people will suffer a mild concussion at some point in their life, so realizing they have trouble smelling is the first step to telling their doctor about it," commented Lecuyer Giguère. Physicians should also inform their patients to check if symptoms appear in the weeks following their accident: “The more people are told to watch for signs of olfactory loss and anxiety, the easier it will be for doctors to respond" she added.

Larger samples of patients should be used in future studies to investigate the link between olfaction and anxiety, concluded the authors.

Source: Lecuyer Giguère F, Frasnelli A, De Guise É, Frasnelli J. Olfactory, cognitive and affective dysfunction assessed 24 hours and one year after a mild traumatic brain injury (mTBI). Brain Inj. 33(9), 1184–1193 (2019); https://nouvelles.umontreal.ca/en/article/2019/07/23/hit-your-head-lose-your-sense-of-smell/

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