ICD-10 Code G23.3 – Hypomyelination with atrophy of the basal ganglia and cerebellum (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G23.3 – Hypomyelination with atrophy of the basal ganglia and cerebellum
What it is
This code identifies a rare inherited neurodegenerative disorder with impaired myelin formation and progressive atrophy of the basal ganglia and cerebellum. It causes abnormalities in brain structure and function, not a nonspecific movement disorder.
Clinical signs
Typical findings include developmental delay or regression, motor impairment, dystonia, spasticity, and cerebellar signs such as ataxia. Clinical features vary; refer to documentation and imaging showing hypomyelination with basal ganglia and cerebellar atrophy.
When to use this code
Use G23.3 when the provider documents this specific diagnosis, usually supported by neurologic evaluation and brain MRI. It is appropriate for confirmed cases, genetic workups, or specialist follow-up notes that name the disorder. Check documentation if the record only says leukodystrophy or movement disorder.
Do not use for
Do not use this code for nonspecific cerebellar ataxia, basal ganglia disease, or demyelinating disorders without this exact diagnosis. Do not assign it when the chart does not clearly document hypomyelination with atrophy of the basal ganglia and cerebellum.
Coding tip
Code only when the provider names the condition explicitly; if the note is vague, query for confirmation.