Evaluation of Olfactory Activation Patterns in Anosmic Patients with Peripheral and Central Injuries as Compared to Healthy Subjects with fMRI

Functional study of brain using fMRI as a method for evaluating important regions of brain and determining the exact locations of activities and their response to the different disorders is not only helpful in medical diagnosis of neurological diseases but also is substantial in studying the functions of different brain areas.Method This is a clinical study on unaffected volunteers as well as patients who have a damaged olfaction after a head trauma. First, we performed fMRI on 20 healthy volunteers after olfactory stimulus using an Olfactometer device. Of total 60 patients, 28 had confirmed anosemia using standard diagnosis tests. Finally in individual-level analysis, we did statistical hypothesis testing and multiple comparisons error correction to identify active brain regions during olfaction. In the last stage, the images and located regions were compared to functional and anatomic atlas provided by other researchers and we also compared brain activity patterns in normal subjects to patients with Anosmia due to head trauma to recognize possible differences.Results Comparing the brain activity level in two groups revealed meaningful differences. The following images show regions controlling olfactory cognition in normal subjects which include piriform cortex, enthorhinal cortex and amygdalae. There were also several secondary regions that olfactory projections seem to enter them over time. These secondary regions include orbitofrontal cortex, hypothalamus, thalamus, hippocampus and insular cortex. In patient’s group, no activity noted on above-mentioned olfactory controlling regions of brain.Conclusions This study shows brain’s function in sensing smells is also different in patients with anosmia after head injury and healthy subjects. We also found that primary and secondary olfactory controlling regions are easily recognizable in normal healthy subjects.