Our objective was to review clinical features and etiologies of axial myopathies and to examine the diagnostic yield of newly available myositis-associated antibodies and targeted next generation sequencing panels. 

Axial myopathy is a rare neuromuscular disorder characterised by selective or preferential involvement of the paraspinal muscles with camptocormia, rigid spine (RS), and/or head drop (HD) as prominent clinical features. Axial weakness as the presenting manifestation of myopathy has been described in case reports and small series of patients with highly variable etiology reported. Advancements in genetic testing and refinement in classification using myositis antibodies allow for increased diagnostic precision.

We performed a retrospective review of patients presenting with axial myopathy at the Montreal Neurological Hospital between 2011 and 2018. Data collection included clinical presentation and disease course, electromyography, associated comorbidities, histopathological findings on muscle biopsy, imaging, laboratory and genetic testing. 

Twenty-six patients were identified. Initial manifestation of axial weakness was HD (16), camptocormia (8), and RS (2). At initial evaluation, 8 had isolated axial weakness while the remaining 18 had additional limb and/or facial weakness. Autoimmune myositis was diagnosed in 9 patients, seropositive in 7 out of 7 tested for antibodies associated with myositis. Genetic testing was consistent with oculopharyngeal muscular dystrophy in one patient and RYR-1 related core myopathy in another. Variants of unknown significance were identified in 9 patients. Local radiotherapy or spine surgery preceded the onset of axial weakness in 1 and 6 patients, respectively. Muscle biopsies were available in 18 patients and revealed myopathic changes in 16, inflammatory changes in 5, and myopathy with vacuoles in 3.

Characterization of myopathy in patients presenting with axial weakness remains challenging. Recent advancements in genetic and antibody testing, combined with muscle biopsy of paraspinal muscles, allow for more precise classification and identification of potentially treatable axial myopathies.