Abstract
A 7-year-old boy presented with cerebellar ataxia with reduced tonicity, deficits of the fine and gross motor coordination skills and vestibular stimulus processing, as well as significantly delayed language development. MR imaging showed the so-called “molar tooth sign”, which was highly pathognomonic for the Joubert-Syndrome—an inherited cerebellar ataxia with a variety of clinical symptoms—and related entities. It is caused by a complex malformation of the cerebellar vermis and the midbrain. The cerebellar vermis is hypoplastic or completely absent; at the same time, the superior cerebellar peduncles are thickened. There is a lack of normal decussation of the fiber tracts in mesencephalon, which follow an abnormal horizontal course, as well as a lack of the decussation of the corticospinal fiber tracts in the caudal medulla oblongata and deformity of the 4th ventricle. Clinically, the triad of cerebellar ataxia, developmental retardation, and abnormal eye movements is indicating a related syndrome of this spectrum. The appearance of the involved children is characterized by dysmorphic facial features with epicanthus, broad nose bridge, low set ears and typically triangularly shaped and opened mouth. The diagnosis is usually made by imaging and clinical findings. Recently, advantages were made in genetic research on the Joubert syndrome and interesting findings published about diffusion tensor imaging and tractography. However, standard MR imaging, applying an adequate imaging protocol including sequences with excellent T1 contrast and 3D imaging with isotropic spatial resolution allowing reconstructions in all orientations, remains an essential tool for making this diagnosis.
Highlights
The Joubert syndrome, an inherited cerebellar ataxia with a variety of clinical symptoms, is an autosomal recessive disease, which is characterized by a congenital midbrain-hindbrain malformation involving the cerebellum and brain stem resulting in a characteristical “molar tooth sign” and variable organ involvement
We report a 7-year-old boy, who was referred to the department of paediatric medicine just before school enrolment due to mental retardation
Magnetic Resonance (MR) examination of the cerebrum was performed, revealing aplasia of the cerebellar vermis (Figure 1), as well as showing the peculiar finding of a so called “molar tooth sign”, which is characteristic for the Joubert-Syndrome and related entities (Figure 2)
Summary
The Joubert syndrome, an inherited cerebellar ataxia with a variety of clinical symptoms, is an autosomal recessive disease, which is characterized by a congenital midbrain-hindbrain malformation involving the cerebellum and brain stem resulting in a characteristical “molar tooth sign” and variable organ involvement. It has been first described in 1969 by the Canadian neurologist Marie Joubert [1]. A lot of more malformations have been described, such as dysplasia of the retina with developing of colobomas, associated congenital heart failures, polydactylia and meningoencephalocele or hydrocephalus. The appearance of the involved children is characterized by dysmorphic facial features with epicanthus, broad nose bridge, low set ears and typically triangularly shaped and opened mouth
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