1505 - Complete paraspinal atrophy causing chronic axial back pain: a case of Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy type 4 (EDMD4)

Case Description:

A 67-year-old male construction worker with paroxysmal atrial fibrillation presented with progression of chronic exertional low back pain without radicular symptoms. This started at age 19 without injury following normal childhood development. He reported exertional back and gluteal burning, improved with rest and lumbar support belt, and calf cramping when walking uphill. He reported a daughter with similar symptoms.

Exam revealed symmetric paraspinal atrophy from the thoracic to lumbar spine and decreased scapulothoracic muscle bulk, with otherwise normal limb strength, sensation, and reflexes.

Lumbar spine MRI demonstrated severe paraspinal atrophy sparing the iliopsoas in the setting of minimal central or foraminal stenoses. Electrodiagnostic studies showed decreased insertional activity and normal amplitude polyphasic motor-unit action potentials in the paraspinals, with otherwise normal limb EMG and normal NCS.

Broad laboratory studies were unremarkable except mild c-reactive protein and creatine kinase elevations, with whole-exome sequencing identifying a SYNE1 gene variant associated with EDMD4.

Discussions:

This case of chronic axial low back pain was clarified when paraspinal atrophy on MRI raised suspicion for a genetic process. Prior to this, he had undergone decades of unhelpful interventions for low back pain including medications, injections and multiple rounds of therapy. Paraspinal atrophy was visualized but never reported on multiple prior radiologic studies. Paraspinal atrophy has been previously described in McArdle's disease and facioscapulohumeral muscular dystrophy (FMD), and initial genetic workup was ordered to assess for these, given exertional pain and cramping. EDMD has multiple subtypes causing muscular dystrophy with proximal weakness, contractures, and cardiac conduction abnormalities, with rare reports of paraspinal atrophy accompanied by significant extra-axial muscular involvement.

Conclusions:

Although focal paraspinal atrophy can reflect chronic denervation in a myotomal distribution due to radiculopathy, paraspinal atrophy spanning all spinal levels should trigger evaluation for systemic causes including EDMD, FMD, and McArdle’s disease.