Evolution of neuroimaging features in children with acute flaccid myelitis compared to other forms of childhood myelitis

BACKGROUND: Acute flaccid myelitis (AFM) is characterized by acute onset of flaccid limb weakness, MRI abnormalities in the spinal cord grey matter and CSF pleocytosis often associated with enterovirus infections. MOG-associated diseases (MOGAD) can manifest with similar neuroradilogical features.

OBJECTIVE: To analyze MRI findings in patients with AFM at baseline and follow-up in comparison to other forms of childhood transverse myelitis such as MOGAD.

PATIENTS AND METHODS: Children from 11 European centers who fulfilled the clinical criteria of AFM were included. Brain and spinal MRI was performed at various stages of the disease course. MRI scans were evaluated using a previously established scoring table and compared with MRI scans of a recently published cohort of children with different forms of transverse myelitis including MOGAD.

RESULTS: We included 15 patients (8 females, 7 males, age range: 9 months-9,11 years). In 10/15 patients enterovirus was detected in respiratory/rectal specimens. At first presentation 13/15 patients presented with a longitudinal extensive transverse myelitis like involvement. Cervical grey matter was involved in almost all children. Axial involvement either manifested as grey matter alone or a mixture of white matter and grey matter hyperintensity in T2. Nerve root enhancement was found in 2/15 and leptomeningeal enhancement in 1/15 patients. 5/15 children had brainstem lesions. Follow-up MRI revealed residual T2 hyperintensities in 7/11 patients. Compared to patients with MOGAD AFM patients showed equally good resolution of MRI lesions overtime.

CONCLUSION: Longitudinal spinal cord lesions mainly affecting the grey matter are characteristic of AFM whereas supratentorial lesions are less common. There is no significant difference between AFM and MOGAD concerning the resolution of lesions overtime.