A child with delayed milestones and interesting findings on MR.

DESCRIPTION A 13-month-oldmale child born of a second degree consanguineous marriage presented with delayed milestones; notably, he was not able to pull to sit or stand and he was swaying from side to side when pulled to sit. He had bilateral post-axial polydactyly (figure 1). He never experienced any respiratory difficulty and there was no history of apnoeic episodes. The central nervous system examinationwas remarkable for generalised hypotonia and gross developmental delay. The child was not able to pull to sit or stand. On attempted sitting he showed truncal ataxia and on approaching an object showed premature grasp and tremulousness. There was no nystagmus. He had started speaking non-specific ‘ma’ and ‘pa’. Ocular fundi were normal. Sonography of the abdomen did not show any renal cyst. MRI of the brain showed features commonly associated with Joubert syndrome and Joubert syndrome related disorders (figure 2), for example: dilatation of the fourth ventricle with bat-wing shaped appearanceelongation and stretching of the superior cerebellar peduncles—the molar tooth appearanceabsence of the cerebellar vermis. The distinctive radiological feature of Joubert syndrome in MRI is molar tooth sign, which has been reported in about 85% patients. This results from dysplastic and thick superior cerebellar peduncles, and deep and wide interpeduncular cisterns. The bat-wing appearance emanates from the dilated fourth ventricle and an anteriorly convex floor. The other sign described, is a buttock sign, because the hypoplasia of vermis causes the cerebellar hemisphere to come closer. Hypoplasia of corpus callosum is also described.