P.87 - Muscle magnetic resonance imaging in inclusion body myositis: presentation of 16 cases

Abstract

Magnetic Resonance Imaging (MRI) has been emerged as a complementary tool in diagnosis and follow up of patients with myopathy. Inclusion Body Myositis (IBM) is the most common acquired myopathy in patients older than 50 years old. It presents with a characteristic pattern of muscle affectation. Despite this, in some patients the diagnosis is not always easy or straightforward. To describe muscle MRI characteristics or a particular pattern in patients with diagnosis of IBM. Patients with diagnosis of IBM according the European Group criteria were included. Muscle MRI included axial y sagittal slices in T1-T2 and STIR sequences of lower limbs (pelvis, thigh and leg). Severity was assessed by Mercuri et al. scale. 16 patients with IBM were included. The median age at diagnosis was 70,07 years-old (range 63–81). 7 were men and 9 women. Delay between first symptom and diagnosis was 40,5 months (range 9–120). MRI showed: Pelvis: Mild affectation of the gluteus. Thigh: Severe compromise of Lateral and internal vastus and moderate of the anterior rectus. Posterior compartment: Semimembranosus and semitendinosus muscle were affected more frequently than the other muscles, although all of them are affected. Sartorius and gracillis are commonly preserved in the majority of the patients. Leg: Anterior compartment: Mild but frequent affectation of the anterior tibialis. Posterior compartment: medial gastrocnemius has severe affectation in all patients, soleus and lateral gastrocnemius in variable form. MRI pattern in IBM in this study is characterized by higher affectation of lateral and internal vastus, semimembranosus, semitendinosus and medial gastrocnemius. Preservation of Sartorius and gracillis muscles is also remarkable, as mild or no affectation of pelvic muscles. Although this pattern was described in other series it should be validated in further studies.