Sarcopenia in patients with dementia: correlation of temporalis muscle thickness with appendicular muscle mass.

Cognitive decline is one of the most relevant signs of sarcopenia; however, it is challenging to perform tests for sarcopenia in patients with dementia. In a recent study, temporalis muscle thickness (TMT), an alternative to appendicular muscle mass (ASM), was found to be a valid index for screening sarcopenia. This study aimed to determine whether TMT correlates with ASM and evaluate the relationship between TMT and cognitive function in dementia patients. We recruited patients with a complaint of memory loss who visited the Memory Clinic of Konkuk University Medical Center between November 2014 and December 2020. Patients with probable Alzheimer's disease (AD) without weakness were included. TMT was measured on axial T1-weighted magnetic resonance (MR) images, perpendicular to the long axis of the temporal muscle, at the orbital roof level. ASM was measured using body dual-energy X-ray absorptiometry (DXA). It was calculated as the sum of lean soft tissue mass in the arms and legs, and the value by ASM divided by height squared was used. Inter-rater reliability and intra-rater reliability were good and excellent, respectively. We found a correlation between TMT and skeletal ASM, which was obtained from cranial MR images and DXA, respectively (r = 0.379, p = 0.001). TMT was negatively correlated with age (r =  - 0.296, p = 0.014) and positively correlated with body mass index (BMI) (r = 0.303, p = 0.012). Additionally, TMT was correlated with MMSE (r = 0.350, p = 0.003). After adjusting for educational years, there was still a correlation between TMT and MMSE (r = 0.256, p = 0.038). This study demonstrated that TMT correlates with ASM and cognitive function in patients with dementia. Measuring TMT using cranial MR images could help diagnose sarcopenia accessibly and assess cognitive function in patients with dementia.