Manifestations of Rheumatoid Arthritis: Epidural Pannus and Atlantoaxial Subluxation Resulting in Basilar Invagination

Atlantoaxial instability results from cartilaginous destruction, periarticular erosions, and ligament and tendon attenuation. Instability affects 19%-70% of patients, and basilar invagination from vertical odontoid subluxation through the foramen magnum occurs in 38% of patients. This phenomenon occurs twice as often in women than men, whose age at diagnosis typically ranges from 30-50 years. Along with bony compression, the pannus further decreases the space available for the cord by 3 mm or more in approximately 66% of patients (Figures 1-7). The earliest and most common symptom of cervical subluxation is pain radiating up into the occiput with associated headaches. Episodes of medullary dysfunction that represent severe but less common patterns of progressive myelopathic symptoms provide an even more grim prognosis. When cervical myelopathy is established, 50% of these patients die within 1 year. The incidence of sudden death from the combination of basilar impression and atlantoaxial instability is 10%. Preoperative neurological deficits provide a guarded prognosis, and basilar impression is associated with poorer recovery of function [1,2]. McRorie et al [3] researchedsurgicaloutcomesandfoundthatnoclearfactorsemergedtopredictthegreatest risk of operative mortality. Neurological compromise did not correlate with immediate perioperative death, and early surgery to correct symptomatic atlantoaxial subluxation may prevent the progression of instability.