Olfactory and Gustatory Function After Bariatric Surgery.

BACKGROUND: Neither hormone levels nor malabsorption alone fully explains the distinct weight loss after bariatric surgery in morbidly obese patients. Postoperatively, patients regularly report a change in the sense of taste and the development of food aversions. Hedonic and sensory components like olfactory and gustatory stimuli significantly affect appetite and flavour. METHODS: We prospectively analysed the orthonasal olfactory and gustatory function with psychophysical testing in 44 patients undergoing laparoscopic Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG) or adjustable gastric banding (AGB) and in 23 healthy controls. RESULTS: About 22.7 % of morbidly obese patients were hyposmic, showing significantly lower threshold-discrimination-identification (TDI) scores (p = 0.009) with decreased discrimination and identification ability. In addition, 22.7 % of patients were tested to be limited in gustatory function, with significantly lower taste strip test (TST) scores (p = 0.003). Six months after surgery, olfactory and gustatory function was not different when compared to healthy controls. CONCLUSIONS: Due to obesity, patients frequently show impaired olfactory and gustatory function. Six months after laparoscopic bariatric surgery, both chemosensory functions improve. The TDI test is an appropriate tool to measure olfactory function in obese patients.

MRI study: objective olfactory function and CNS pathologies in patients with multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) is a chronic disease characterized by CNS lesions causing physical and cognitive impairment. Using psychophysical testing, an olfactory disorder is diagnosed in 15-38.5% of patients with MS. Olfactometry permits objective testing of the sensory nerve function. METHODS: The study looked at 20 patients with MS. Clinical, olfactory (chemosensory evoked potentials), and MRI data (volume of the bulbus olfactorius (BO), olfactory brain (OB), lesions in the CNS) were analyzed. RESULTS: 25 percent of patients were hyposmic, exhibiting higher OB lesion volumes and smaller bulb volumes. H2S and CO2 latencies and the BO volume (inversely) correlated with the volume and number of MS lesions of the olfactory brain in all patients. Patients with a smaller olfactory bulb volume exhibited longer H2S latencies (p = 0.025). CONCLUSION: A relationship between olfactory bulb volume, olfactory brain lesion load, and objective olfactory function testing in MS patients was investigated in all patients. Our data shows that brain damage characteristic of MS, including reduced bulb volume, causes an increase in chemosensory potential latencies and an olfactory function deficit.

Tract-based spatial statistics of the olfactory brain in patients with multiple sclerosis.

PURPOSE: To investigate diffusion tensor abnormalities, e.g. fractional anisotropy (FA), mean diffusivity (MD), and radial diffusivity (RD), in olfactory structures of multiple sclerosis (MS) patients using diffusion tensor imaging (DTI). METHODS: Institutional review board-approved prospective study on 30 MS patients and 12 healthy controls investigated with MRI including DTI. Central olfactory structures were labelled on each patient's and healthy contro''s DTI volume. The diffusion tensor was determined in the central olfactory structures in MS patients. Tract-based spatial statistics (TBSS) was used to quantify the streamlines outgoing from the olfactory structures and to quantify changes in FA, MD, and RD within olfactory structures. These brain changes were correlated with olfactory function measured as TDI (Threshold, Discrimination, Identification) scores in patients and compared to our own reference group of 30 healthy volunteers. RESULTS: Central olfactory structures in the MNI (Montreal Neurological Institute) data volume comprise 4808 voxels (4808 mm(3)). TFCE (Threshold-free cluster enhancement) and cluster analysis of patients identified a total of 127 voxels in one cluster with a significantly decreased FA (p<0.05) and none for MD and RD within olfactory structures compared to healthy controls. The correlation with the age-normalised Identification subscore of the TDI score increased the significant number of voxels with decreased FA to 208 voxels, with increased MD to 370 and with increased RD 364 voxels at the same region. CONCLUSION: The decrease in FA and increase of MD and RD correlate with the degree of identification impairment of olfactory function in MS patients and clusters of abnormalities were identified on a MNI data volume.