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Background The Dandy-Walker malformation (DWM) is one of the commonest congenital cerebellar defects, and can be associated with multiple congenital anomalies and chromosomal syndromes. The occurrence of overlapping 3q deletions including the ZIC1 and ZIC4 genes in few patients, along with data from mouse models, have implicated both genes in the pathogenesis of DWM. Methods and results Using a SNP-array approach, we recently identified three novel patients carrying heterozygous 3q deletions encompassing ZIC1 and ZIC4. Magnetic resonance imaging showed that only two had a typical DWM, while the third did not present any defect of the DWM spectrum. SNP-array analysis in further eleven children diagnosed with DWM failed to identify deletions of ZIC1-ZIC4. The clinical phenotype of the three 3q deleted patients included multiple congenital anomalies and peculiar facial appearance, related to the localization and extension of each deletion. In particular, phenotypes resulted from the variable combination of three recognizable patterns: DWM (with incomplete penetrance); blepharophimosis, ptosis, and epicanthus inversus syndrome; and Wisconsin syndrome (WS), recently mapped to 3q. Conclusions Our data indicate that the 3q deletion is a rare defect associated with DWM, and suggest that the hemizygosity of ZIC1-ZIC4 genes is neither necessary nor sufficient per se to cause this condition. Furthermore, based on a detailed comparison of clinical features and molecular data from 3q deleted patients, we propose clinical diagnostic criteria and refine the critical region for WS.

Pontine Tegmental Cap Dysplasia (PTCD) is a recently described, rare disorder characterized by a peculiar cerebellar and brainstem malformation. Nineteen patients have been reported to date, of which only one in the adolescent age, and data on the clinical, cognitive and behavioural outcome of this syndrome are scarce. Here we describe three adolescent patients with PTCD. All presented bilateral deafness and multiple cranial neuropathies, variably associated with skeletal, cardiac and gastro-intestinal malformations. Feeding and swallowing difficulties, that are often causative of recurrent aspiration pneumonias and death in the first years of life, completely resolved with age in all three patients. Neuropsychological assessment showed borderline to moderate cognitive impairment, with delay in adaptive functioning, visual-spatial and language deficits. Two of three patients also showed mild behavioural problems, although their overall socialization abilities were well preserved. Cochlear implantation in two patients significantly improved their relational and learning abilities. Fibre tractography confirmed the abnormal bundle of transversely oriented fibres forming the typical pontine "tegmental cap" and absence of decussation of the superior cerebellar peduncles, supporting the hypothesis that PTCD results from abnormal axonal guidance and/or migration. These data indicate that PTCD may have a favourable long-term outcome, with borderline cognitive deficit or even normal cognition and partially preserved speech.