Early onset chorea preceded by hypotonia is suggestive of BHC. Associated thyroid or respiratory disorders further support the diagnosis and call for genetic studies. Tetrabenazine may be an interesting option to treat disabling chorea.

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Severe neonatal episodic laryngospasm is a new phenotype caused by a sodium channelopathy, which can be alleviated by channel blockers.

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Cerebral creatine deficiency syndromes (CCDSs) are inborn errors of metabolism that include two autosomal recessive creatine biosynthesis defects (arginine-glycine amidinotransferase [AGAT;OMIM 602360] and guanidinoacetate methyl transferase [GAMT;OMIM 601240] deficiency) and an X-linked creatine transporter defect (OMIM 300036). 1 The clinical phenotype is variable, associating nonspecific mental retardation, epilepsy, extrapyramidal movement disorders, and autistic behavior. The frequency of CCDS is unknown and probably underestimated. We report a high frequency of CCDS in mentally retarded children, mostly boys with an X-linked creatine transporter deficiency.Methods. Over a period of18 months, children referred to the Department of Pediatric Neurology with unexplained mild to severe mental retardation, normal karyotype, and absence of fragile X syndrome were prospectively screened for CCDS. Children were from diverse ethnic backgrounds. Children with polymalformative syndromes were excluded. Creatinine metabolism was evaluated using creatine/creatinine and guanidinoacetate (GAA)/creatinine ratios on a spot urine. 2 Diagnosis was further confirmed using brain proton MR spectroscopy (H-MRS) and mutation screening by DNA sequence analysis in either the SLC6A8 (creatine transporter defect) or the GAMT genes.Results. One hundred eighty-eight children were eligible to participate: 114 boys (61%) and 74 girls (39%); 118 children (63%) were severely retarded and 70 (37%) had mild to moderate mental retardation. Family history revealed 151 (80%) sporadic cases and 37 (20%) familial cases (siblings or first-degree relatives). Four boys from four unrelated families had elevated creatine/creatinine ratio, suggesting a creatine transporter defect. In another boy, elevated urinary GAA/creatinine ratio suggested GAMT deficiency. H-MRS and molecular investigation confirmed the diagnosis, and five new mutations either in the SLC6A8 or GAMT gene were identified. All five patients presented with severe mental retardation. Brain MRI showed minor and nonspecific abnormalities. Extensive clinical, radiologic, and biologic characteristics are depicted in the table on page 1714.The prevalence of CCDS was 2.7% (5/188, CI: 0.36 to 4.96) in the whole population and 4.4% (5/114, CI: 0.63 to 8.15) in boys. None of the 74 girls had a CCDS. In the 151 sporadic cases, prevalence of CDDS was 1.9% (3/151, CI: 0 to 4.21). In the 37 familial cases, the prevalence was 5.4% (2/37, CI: 0 to 12.7).Discussion. These results show a high prevalence of CCDS