18q-deletion syndrome is a rare chromosomal anomaly where there is a deletion of part of the long arm of chromosome 18. Associated symptoms and findings vary widely, as do their severity. Characteristic clinical features include short stature, mental retardation, hypotonia, facial and distal skeletal abnormalities.
The presence of the syndrome is usually evident at or soon after birth. Although there is significant phenotypic variation, some features are relatively constant and include 1:
- decreased growth
- craniofacial dysmorphism
- genital hypoplasia
- limb abnormalities
- neurological abnormalities
- developmental delay and mental retardation
- ocular movement disorders
Chromosome 18q syndrome appears to result from a spontaneous, sporadic chromosomal error during very early embryonic development.
The appearance of the brain on MRI is dominated by hypomyelination and abnormal white matter, particularly posteriorly and in the periventricular region. It is characterized by bilateral symmetric deep white matter hyperintensity on T2-weighted images, with associated involvement of the subcortical white matter also frequently encountered 1,2. The brainstem and cerebellum are usually spared.
MRS demonstrates elevated white matter choline and alpha-glutamate concentrations (resonates at 3.75 ppm) 3.
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- 2. Lancaster JL, Cody JD, Andrews T et-al. Myelination in children with partial deletions of chromosome 18q. AJNR Am J Neuroradiol. 2005;26 (3): 447-54. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 3. Häusler M, Anhuf D, Schüler H et-al. White-matter disease in 18q deletion (18q-) syndrome: magnetic resonance spectroscopy indicates demyelination or increased myelin turnover rather than dysmyelination. Neuroradiology. 2005;47 (1): 83-6. doi:10.1007/s00234-004-1309-9 - Pubmed citation
- 4. Linnankivi TT, Autti TH, Pihko SH et-al. 18q-syndrome: brain MRI shows poor differentiation of gray and white matter on T2-weighted images. J Magn Reson Imaging. 2003;18 (4): 414-9. doi:10.1002/jmri.10383 - Pubmed citation
- 5. Kumada T, Ito M, Miyajima T et-al. Intractable epilepsy (apneic seizure) in an infant with 18q deletion syndrome. No To Hattatsu. 2004;35 (6): 521-6. Pubmed citation