Heterozygous mutations in SIX3 and SHH are associated with schizencephaly and further expand the clinical spectrum of holoprosencephaly.

Schizencephaly (SCH) is a clinically and etiologically heterogeneous cerebral malformation presenting as unilateral or bilateral hemispheric cleft with direct connection between the inner and outer liquor spaces. The SCH cleft is usually lined by gray matter, which appears polymicrogyric implying an associated impairment of neuronal migration. The majority of SCH patients are sporadic, but familial SCH has been described.

Missense exchanges in the TTBK2 gene mutated in SCA11.

The spinocerebellar ataxias (SCAs) with autosomal dominant inheritance are a clinically and genetically heterogeneous group of neurological disorders with overlapping as well as highly variable phenotypes primarily affecting the cerebellum. To date, 28 different loci have been identified. Nine SCAs are caused by repeat expansions; for 14 only the chromosomal localisation is known.