Symptomatic noncompressive motoromyelopathy presents as early manifestation in ankylosing spondylitis

Ankylosing spondylitis (AS) is an autoimmune spondyloarthropathy involving principally the sacroiliac joint and axial skeleton. Spinal cord involvement is an infrequent and late complication. It mostly results from compressive myelopathy due to skeletal osteopathy and usually presents with radiculomyelopathic sensory and motor deficits. To report three patients who suffered a progressive paraparesis/tetraparesis compatible with motor myelopathy without typical skeletal symptom. Myelopathy of unknown origin was initially interpreted in these patients. Radiography did not show typical change at sacroiliac joint or vertebrate. Spinal magnetic resonance image revealed cord atrophy at cervical and thoracic segment. A positivity of B27 antigen was found afterward. Their spondyloarthropathic symptoms developed within six months later with radiographic sacroiliitis. Seropositive AS with noncompressive myelopathy was finally established. Patients showed a reverse of motor impairment when their pain was well undercontrolled. Motor myelopathy may be neglected or underestimated in AS, in especially when typical skeletal symptom is absent or minimal. It may progress surreptitiously to harm spinal function or superimpose to crippling disability in compressive spinal cord injury. Therefore, a careful evaluation and monitor of spinal cord function is important for AS patient despite spinal deformity is not observed.