Syndrome of inappropriate antidiuretic hormone secretion associated with seronegative neuromyelitis optica spectrum disorder

Abstract

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a potential cause of hyponatremia of the central nervous system (CNS). Although SIADH has been reported to be associated with many other central nervous disorders, its association with neuromyelitis optica (NMO) or NMO spectrum disorders are rare. NMO is a demyelinating disorder characterized by optic neuritis and transverse myelitis. Aquaporin-4 (AQP4), which is the target antigen for a NMO autoantibody, is the predominant CNS water channel. However, some NMO patients show seronegative AQP4 antibody results. The spectrum of NMO has been changed, and new findings about the disease have been reported. Here, we report a case of seronegative NMO spectrum disorder associated with SIADH.

Keywords: Aquaporin-4; Neuromyelitis optica; Syndrome of inappropriate antidiuretic hormone secretion.

Figure 1. Brain magnetic resonance imaging of the patient

(A) T2 FLAIR image revealing focal high signal intensity at the lower medulla oblongata (arrow). (B, C) T2 high signal lesion involving the hypothalamus and suspicious left optic chiasm (arrows). (D) A sagittal T2-weighted image showing multifocal T2 high signal lesion (arrows) at the upper cervical spinal cord.

Figure 2. The pattern of changing levels of serum sodium during hospitalization

Normal saline was administrated for first two days and replaced with hypertonic saline. Her neurological symptoms and serum sodium level was recovered after treatment with high-dose methylprednisolone. HD, hospital day; IV, intravenous; MPD, methylprednisolone.