Asymptomatic MRI lesions in pediatric-onset AQP4-IgG positive NMOSD

Around 5% of all Neuromyelitis Optica Spectrum Disorders (NMOSD) cases start before 18 years of age. Clinical and radiological manifestations of AQP4-IgG positive NMOSD were revised in 2015, and the importance of neuroimaging in the diagnosis is well recognized. Neuroimaging findings in pediatric-onset NMOSD were scarcely described, and longitudinal evaluation of NMOSD lesions was only accessed in a few adult-onset cohorts.

This study evaluated brain, spinal cord, and optic nerve MRI of sixteen pediatric-onset AQP4-IgG positive NMOSD through a qualitative evaluation of lesion evolution. Lesions were classified as symptomatic or asymptomatic in acute or chronic phase (> 30 days from last attack) MRI.

Seventy MRI scans and 54 subsequent exams were evaluated. Most NMOSD lesions (74.5%) reduced, remained stable, or developed atrophy/cavitation. New brain lesions or enlargement of existing brain lesions were found in two patients (12.5%) without any clinical symptom and in five patients (31.2%) in the course of an attack from other topography (optic neuritis or acute myelitis). One patient (6.3%) presented an asymptomatic spinal cord lesion irrespective of clinical manifestation. No asymptomatic lesion was described in optic nerve MRI. In acute phase exams, longitudinally extensive transverse myelitis (13/19 vs 8/24; p = 0.033), cervical myelitis (15/19 vs 10/24, p = 0.028), lumbar myelitis (5/19 vs 0/24; p = 0.012), and a higher number of segments [median 8 (range 4-17) vs 3.5 (range 1-14); p = 0.003] were affected.

Asymptomatic brain and spinal cord lesions can occur in pediatric-onset NMOSD, especially in the course of acute optic neuritis or myelitis. More longitudinal studies are necessary to guide recommendations on neuroimaging frequency in pediatric patients with AQP4-IgG NMOSD.