Neuromyelitis optica with high aquaporin-4 expression and positive serum aquaporin-4 autoantibodies

Neuromyelitis optica with high aquaporin-4 expression and positive serum aquaporin-4 autoantibodies. Disease-specific aquaporin-4 antibodies (NMO-IgG) are the main effector of lesions in neuromyelitis optica (NMO) patients. Brain MRI lesions are detected in 60% of them, with 8% (almost infants) at sites of high aquaporin-4 expression. Patient 1: A fifty-year-old male with loss of vision in the right eye. Empiric treatment with metilprednisolone 1g/d for 3 days was indicated. After 30 days he complained of generalized pain, and a right hemiparesis was evident. The patient received bolus of metilprednisolone 1g/d for 5 days plus IgG 400 mg/kg/d IV for 5 days. He recovered ambulation but persisted with pain and paroxysmal phenomena (Lhermitte). Visual Evoked Potentials (VEP): P100 left eye 123 ms, right eye without response. Brain MRI (FLAIR) showed hyperintensity in the right optic nerve, hypothalamus and anterior white commissure. Cervical MRI showed extensive spinal cord lesion to an extension of 5 vertebral bodies. Patient 2: A fifty-three-year-old female who referred decreased visual acuity in both eyes and paresthesia in lower limbs which subsided spontaneously. One month later the patient evolved with cuadriparesis and sphincter incontinence. No improvement was observed with bolus of metilprednisolone 1g/d for 5 day. VEP: P100 left eye 124 ms, right eye 128 ms. Brain MRI (FLAIR) disclosed hypothalamic and periaqueductal hyperintensity. Cervical MRI showed extensive spinal cord lesion to an extension of 7 vertebral bodies. NMO-IgG antibodies were positive in both patients (indirect immunofluorescence assay). NMO brain lesions at sites of high aquaporin-4 expression, once considered "atypical" for their topography and infrequency in adults, should be borne in mind when considering differential diagnosis.