Clinical features include choreoathetosis, dystonia, rigidity, spasticity, dysphagia, optic atrophy, intellectual deficit, developmental regression of motor and verbal skills
[rarediseases.info.nih.gov]
The clinical features of IBSN include developmental regression, choreoathetosis, dystonia, spasticity, dysphagia, failure to thrive, nystagmus, optic atrophy, and mental retardation
[genome.jp]
[…] progressing to spastic quadriparesis.
[rarediseases.info.nih.gov]