Traumatic brain injury causes loss of smell and taste

The ability to taste and smell can be lost or impaired after a head injury, according to a new study by scientists from the Université de Montréal, the Lucie Bruneau Rehabilitation Centre, as well as the Center for Interdisciplinary Research in Rehabilitation of Greater Montreal. Published in the journal Brain Injury, the investigation established that mild to severe traumatic brain injury could cause olfactory loss.

"The study clearly demonstrates that olfactory deficits can occur in mild traumatic brain injury patients as well as in moderate and severe TBI patients," says study co-author and neuropsychologist Maurice Ptito, a professor at the Université de Montréal School of Optometry. "We also found that patients with a frontal lesion were more likely to show olfactory dysfunctions."

The research team recruited 49 people with TBI (73 percent male with a median age of 43) who completed a questionnaire and underwent two smell tests to measure their olfactory loss. The result: 55 percent of subjects had an impaired sense of smell, while 41 percent of participants were unaware of their olfactory deficit.

"Both tests indicated the same results: patients with frontal injury are more likely to suffer olfactory loss," says lead author Audrey Fortin, a professor at the Université de Montréal School of Optometry and researcher at the Lucie Bruneau Rehabilitation Centre.

Smell plays a vital role in our lives, says Dr Fortin, since olfaction influences what we eat, can help us detect gas leaks or fires. Smell also has a huge impact on interpersonal relationships, since olfactory disorders have been associated with poor quality of life, depression, mood swings, worries about personal hygiene, loss of appetite and cooking difficulties.

"Olfactory dysfunctions have a negative impact on daily life, health and safety," says Dr Fortin. "It is important to pay attention to this symptom once a patient's condition has been stabilised following a traumatic brain injury."

About TBI and anosmia

Traumatic brain injury (TBI) occurs when the head suddenly and violently hits an object or when an object pierces the skull and enters brain tissue. Symptoms of a TBI can be mild, moderate or severe and the condition is most common among adolescents, young adults and the elderly. Anosmia is the inability to smell. The olfactory nerve is the only commonly injured cranial nerve following mild traumatic brain injury, which can lead to diminished sense of smell or complete smell loss.

(Source: Université de Montréal: Brain Injury: March 2010)