Date of Award

January 2022

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Bhaskar Roy

Abstract

Background:Inclusion body myositis (IBM) is the most common inflammatory myopathy to affect individuals age greater than 50. IBM typically presents with quadriceps and finger flexor weakness, and about 40% of patients develop dysphagia. While the clinical features of IBM are fairly well established, the disease burden of dysphagia and falls has been largely ignored. A few functional scales are used to measure the disease burden and severity in IBM, but they can have subjective variations. There is also a lack of objective biomarkers. While imaging studies have shown promise as biomarkers of muscle damage in IBM, no comparison between these technologies has been performed.

Purpose:The aim of this work is to examine the disease burden of dysphagia and falls in IBM compared to other inflammatory myopathies. Our second aim was to examine different imaging technologies in IBM, including electrical impedance myography (EIM), muscle MRI, and neuromuscular ultrasound.

Methods:To examine the burden of dysphagia and fall, we examined the National Inpatient Sample (NIS) from 2012 to 2018. Diagnoses and procedural codes were used to identify patients with a primary diagnosis of IBM or idiopathic inflammatory myopathies (IIM) (defined in this study as having either polymyositis or dermatomyositis), and other codes for complicating events during the admission such as aspiration pneumonia and falls as well as interventions such as PEG tube placement. For our second aim, we compared electrical impedance myography (EIM) with ultrasound and MRI for cohort of 9 patients with IBM and 3 healthy control patients. We performed EIM (measuring resistance, reactance, and phase angle), and grayscale level analysis from neuromuscular ultrasound from ten muscles on both sides at predefined locations. Furthermore, we examined the muscle MRI of these patients, and compared between the parameters from these different imaging technologies, to better understand their capacity to capture muscle health. Descriptive statistics, chi-square analyses, and multivariate logistic regression models were performed to compare the complications between the different types of inflammatory myopathies. Results: From 2012 to 2018, there were 18,819 admissions for patients with either IBM, DM, or PM. The mean age for IBM was 72.9 +/- 10.7 years as compared to 59.3 +/- 18.4 years for patients in the IIM cohort. There was a statistically significant difference in gender distribution between IBM (65.0% men) patients and IIM (31.2% male) (p < 0.001). The proportion of Caucasians in IBM (82.5%) was also much higher than for IIM (58.4%) (p < 0.001). The frequency of aspiration pneumonia was 14.3% in IBM compared to 3.6% in IIM (p < 0.001). Percutaneous endoscopic gastrostomy (PEG) tube placement was placed at a much higher frequency in IBM (6.6%) cohort as compared to IIM (2.1%) (p < 0.001). A multivariate logistic regression model showed that being elderly, male, and having IBM contributed to aspiration events and PEG tube placement. Finally, there appeared to be a slight overall increase in the annual average rate of PEG tube placement between 2012 and 2018. Furthermore, we identified a much higher fall risk in IBM patients (10.7%) than patients with IIM (4.1%), ALS (4.7%), and hereditary progressive muscular dystrophy (HPMD) (4.8%) (p < 0.00001). EIM also demonstrates early promise for prognostication in comparison to quantitative ultrasound for select muscle groups. For our second aim in this study, we recruited 9 patients with IBM, and 3 healthy controls. The average age of the IBM cohort was 70.3 +/- 5.7 years and 77.8% were men. Both EIM and ultrasound showed significant differences between the IBM cohort and healthy controls. EIM phase value at 211 kHz was 4.4 +/- 2.4 for the IBM cohort versus 10.7 +/- 4.9 in the control group (p-value = 0.012). For the quantitative ultrasound, the averaged GSL value from the IBM group was higher when compared to the control group (68.2 +/- 15.5 versus 50.4 +/- 10.9, p-value = 0.03). There was a trend of mild-to-moderate correlation between the EIM and ultrasound GSL values from some of the individual muscles. Given limitations in MRI data available, little statistically significant relationship between EIM and MRI can be gleaned thus far. Conclusion: Dysphagia is a significant comorbidity amongst IBM patients. They are more prone to falls even when compared to amyotrophic lateral sclerosis and other hereditary myopathies. Both EIM and muscle ultrasound are able to differentiate between IBM and healthy controls. More data is needed to confidently determine the relationship between these imaging technoloSouravgies.

Comments

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