Supplementary Material for: The feasibility and validity of sarcopenia assessment using standard of care stroke imaging.

Introduction
Sarcopenia, an age-related syndrome defined by low muscularity, loss of muscle strength and performance, is increasingly recognised as a potential contributor to disability following acute stroke. It is challenging to assess functionally in the acute post-stroke setting. Radiological assessment of skeletal musculature using standard of care CT neck imaging has recently been described. We sought to determine its feasibility and explore associations between CT-defined sarcopenia, validated frailty and functional indices and outcome at 18 months.

Methods
Imaging and clinical data from a prospective cohort study was used. Frailty and functional indices were collected, including the NIH Stroke Scale, Barthel Index for Activities of Daily Living, Fried frailty phenotype, Lawton Instrumental Activities of Daily Living (IADL) Scale, the Frail Non-Disabled (FiND) Questionnaire and pre-stroke modified Rankin Scale. Single transverse slices of neck CT angiograms obtained at the time of acute stroke diagnosis were assessed for skeletal muscle area using ImageJ software; a skeletal muscle index (SMI) was calculated. The relationship between sarcopenia, frailty and functional indices and death or disability at 18 months was assessed using binary logistic regression.

Results
Of 86 potentially eligible patients, 73 were included. It was possible to perform skeletal muscle analysis on the CT scans of all included patients. SMI and functional or frailty indices were not closely correlated. SMI alone was independently related to death or disability at 18 months. The addition of SMI to the abbreviated FiND score appeared to strengthen its associations and prognostic value.

Conclusion
This study demonstrates initial feasibility of CT-based skeletal muscle assessment in patients with acute stroke. The relationships with functional and frailty measures as well as short term outcomes including the ability to execute activities of daily living are required to be explored and validated in a larger, external cohort.