The cerebellar atrophy detected by brain MRI in both cases of the current study is similar to the atrophy previously reported in typical patients with AHC and the c.2401G>A (p.Asp801Asn) variant or c.2423C>T (p.Pro808Leu) variant in ATP1A3. 14Therefore, pure mild cerebellar cortical atrophy may be a trait that can help to identify progressive cerebellar ataxia cases of ATP1A3‐related neurological disorders. Here, ATP1A3 is linked to alternating hemiplegia of childhood.