Teaching Video NeuroImage: Dissociation of Abdominal Reflexes in Rheumatoid Atlantoaxial Subluxation.

Abstract

A 59-year-old woman with rheumatoid arthritis presented with progressive gait difficulties and electric shock-like pain triggered by neck flexion (Lhermitte sign) for more than 6 months. On examination, she had hyperreflexia in the 4 limbs and brisk deep abdominal reflexes with absent superficial abdominal reflexes (reflex dissociation) (Video 1). MRI showed spinal cord compression resulting from anterior subluxation of the atlas and retrodental pannus (synovial tissue proliferation) (Figure). Superficial abdominal reflexes may be absent in 20% of normal individuals.1 However, the dissociation of abdominal reflexes suggests an upper motor neuron lesion above the T6 spinal segment.2