Abstract
2799
Introduction: Background: Patients with metabolic syndrome components were frequently noted to have increased nasal and parotid activity on clinically referred scintigraphic whole-body blood pool scans which was not present in patients with normal body mass indices (BMI). Nasal turbinate and parotid gland blood volumes are under autonomic control with increased parasympathetic activity causing turbinate vasodilation and increased sympathetic activity causing turbinate vasoconstriction. Increased nasal blood pool activity in patients with metabolic syndrome components could potentially contribute to the development of (1) sleep apnea, (2) the risk of nasal infections, and (3) impaired nasal lymphatic drainage of brain waste proteins.
Purpose: The purpose of the current study was to further evaluate this clinical observation by performing a retrospective study 200 patients to determine if nasal and/or parotid blood pool activity was significantly correlated with metabolic syndrome components.
Methods: A retrospective study was performed in 200 patients having whole body blood pool scans performed from 1-10 minutes after administration of 99mTc-MDP who were referred from the rheumatology clinic over a 3 year period. The whole body blood pool scans were obtained to assess for soft tissue inflammation as part of a standard delayed phase bone scan. Regions of interest were drawn over the nose, parotid, heart and thigh regions on the whole body blood pool scans. Max pixel and whole region counts were evaluated for an association between ((nose and parotid region of interest (ROI) max pixel)) / (heart ROI max pixel) ratios for correlations with clinical conditions including obesity, diabetes, hypertension, and sleep apnea using the Wilcoxon rank sum test. Continuous variables like BMI, HbA1C, blood glucose, blood lipids were also correlated with these ratios using Pearson correlation. All testing was two-sided with a significance level of 0.05.
Results: A direct association of nose to heart max pixel count ratio (NHMR) with clinical conditions of diabetes, sleep apnea and hypertension was found with increase in ratio of +.10 (p=.002), +.13 (p=.0002), +.08 (p=0.0123) respectively. Correlation of NHMR with continuous variables had moderate correlation with BMI (r=.36, p<0.0001), glucose (r=.27, p=0.0001), HbA1c (r=.25, p=0.0008) and less association with the number of diabetes (r=.22, p=0.0021) medications. Similar associations were found for parotid to heart max (PHMR) ratios, but they were weaker than the NHMR. Similar significant associations were also noted for total region nasal and parotid counts to heart region counts however the max pixel assessment was considered to be less variable. No significant associations were found for thigh ratios.
Conclusions: Patients with metabolic syndrome components have significantly increased nasal and parotid/heart activity ratios on whole body blood pool scan likely related to increased nasal turbinate blood volumes. Significant associations were noted between nasal and parotid/heart blood pool activity to BMI, sleep apnea, diabetes and hypertension as well as glucose and HbA1C. These significant associations have potential implications regarding the mechanisms and treatment of sleep apnea, nasal infections and dementia. These findings provide support for future prospective studies comparing normal metabolic subjects to patients with metabolic syndrome using 99mTc-tagged red blood cell upper body imaging or other anatomic-based imaging methods such as CT or MRI imaging of the nasal turbinates and parotids. If further studies support these findings, nasal turbinate vasodilation and/or the autonomic system controlling nasal turbinate vasodilation in metabolic syndrome patients could become new therapeutic targets.
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