Hydrocephalus and secondary syndrome of inappropriate antidiuretic hormone due to rheumatoid vertical atlantoaxial subluxation.

We describe symptomatic hydrocephalus and secondary syndrome of inappropriate antidiuretic hormone as clinical manifestations of vertical atlantoaxial subluxation in a patient with severe rheumatoid arthritis. We found no reports of this association as a complication of rheumatoid cervical involvement. We discuss the difficulties of differential diagnosis and treatment in this patient.