Imaging evaluation of the upper limbs in inclusion body myositis: an unmet need

Inclusion body myositis (IBM) is an acquired myopathy belonging to the spectrum of idiopathic inflammatory myopathies. It commonly presents in individuals aged above 50 years of age. Characteristic clinical features of IBM include weakness of the quadriceps and finger flexors. There are currently no effective drug treatments for IBM. However as more clinical drug trials are being conducted it is important that more precise outcome measures are developed to track disease progression and assess treatment effects. Imaging techniques such as magnetic resonance imaging (MRI) and ultrasound have been increasingly used to study intramuscular changes within the thigh and calf muscles. In particular quantitative MRI assessments of the lower limb have started to be employed as endpoints for clinical trials in IBM patients. However, in comparison to the lower limb, there is a relative lack in robust imaging biomarkers for the upper limb muscles. It is prudent that this paucity is addressed as the majority of IBM patients have forearm involvement and, in many individuals, upper limb weakness is their main source of disability. Imaging focussed studies thus far indicate preferential flexor digitorium profundus involvement. In this review, we discuss the imaging modalities that have been used to evaluate intramuscular changes and the possible techniques which could be developed further as upper limb biomarkers for IBM.