A brief summary of current research.
Fortin, A, Lefebvre , MB and Ptito, M (2010). Brain Injury, Vol. 24(1), pp 27-33.
This study compared two tests used to determine difficulty with the sense of smell after brain injury. The two smell tests found that patients with frontal lesion performed significantly worse than patients with other types of lesion. A high proportion — 40-44 percent — of patients with olfactory impairments were not aware of their difficulty, and the authors recommend that clinicians systematically assess olfactory functions.