Fast Progression of Cerebellar Atrophy in PLA2G6-Associated Infantile Neuronal Axonal Dystrophy

Infantile neuronal axonal dystrophy (INAD) is characterized by progressive cerebellar atrophy. MRI has been recommended as a marker of disease progression in cerebellar diseases. We performed a longitudinal brain volumetry study in a couple of bicorial twins with PLA2G6-positive INAD. Brain volumetry was calculated with FreeSurfer software on 3T T1-weighted images acquired at age 28 (t ₀) and 36 months (t ₁) in patient 1 and at age 22 (t ₀) and 31 months (t ₁) in patient 2. Data at t ₀ were compared to those obtained in 18 control children aged 14-44 months with normal MRI. At t ₀, both patients showed markedly lower cerebellar volume compared to controls. At t ₁, both patients exhibited a remarkable decrease of cerebellar volume (-25.8% in patient 1; -16.5% in patient 2) and of frontal (-6.8% in patient 1 and -3.3% in patient 2) and occipital (-9.8% in patient 1 and -9.1% in patient 2) cortical GM volume. Our MRI morphometry study indicates that INAD is characterized by a remarkably fast progression of cerebellar atrophy and mild atrophy of the frontal and occipital cortex presumably secondary to deafferentation in the cortical-pons-cerebellum-rubro-thalamus-cortical circuit and visual pathways.