A previously well 14-year-old African American female presented with anorexia, recurrent vomiting, and weight loss for 2 weeks. She had lost 9 kg in the preceding 2 weeks and was assessed by a child psychiatrist who did not identify body dysmorphology or other features of anorexia nervosa. Other than daily vomiting three to four times per day of undigested food and associated weight loss, there were no other symptoms. Gastroscopy was negative. Neurological examination was normal, including fundoscopy, which was negative for papilledema.

Brain MRI showed T2 hyperintense patchy signal in the thalami and medulla, particularly periaqueductal gray and dorsal medulla in the area postrema ( Fig. 48.1 ).

Neuromyelitis optica spectrum disorder. Brain MRI, (A) coronal T2 shows patchy hyperintensity in the right greater than left thalami and medulla, including the periaqueductal gray and area postrema ( arrows ). Cervical spine MRI, (B) sagittal T2 shows patchy hyperintensity throughout the cord ( arrows ).

Cerebrospinal fluid examination showed mild CSF pleocytosis (35 white cells per mm ³ , including 12 polymorphonuclear cells), slightly elevated CSF protein (0.67 g/dl), and negative oligoclonal bands. Serum testing for aquaporin-4 antibodies (neuromyelitis optica immunoglobin G [NMO IgG]) was positive. The patient also had elevated antinuclear antibodies.

Unexplained vomiting and severe weight loss without gastrointestinal or eating disorder suggest a CNS condition, likely inflammatory based on CSF testing. Increased intracranial pressure or functional neurological disorders can present this way, but are usually accompanied by more global symptoms.