Joubert syndrome

Last revised by Rohit Sharma on 20 May 2024

Joubert anomaly, also known as vermian aplasia or molar tooth midbrain-hindbrain malformation, is an autosomal recessive disorder where there is a variable degree of cerebellar vermal agenesis. 

When associated with anomalies of the kidneys, liver and/or eyes the term Joubert syndrome and related disorders (JSRD) is used. 

The prevalence of Joubert syndrome is approximately 1 in 100,000. There are numerous associations which are variably present 5:

Affected individuals usually present with ataxia and have dysmorphic facies, global developmental delay, hypotonia, rapid breathing and oculomotor apraxia. There is significant range in the degree of cognitive impairment with IQ ranging from 30 to 80, although the presence of speech and motor deficits makes assessment difficult 7

Typically, patients have nystagmus and inability of smooth pursuit of a moving object 5.

Joubert syndrome patients are a genetically heterogeneous population with some having a mutation of chromosome 9q34.3 however many do not 4. At least 10 genes relating to subcellular organelles (including the primary cilium and basal body) have been implicated; as such Joubert syndrome is one of a number of related disorders known as ciliopathies 7,8

Cross-sectional axial imaging demonstrates isolated abnormality of the cerebellum consisting of:

The posterior fossa typically shows a bat wing 4th ventricle and prominent thickened elongated superior cerebellar peduncles giving a characteristic molar tooth sign appearance 1,9.

In a minority of cases minor lateral ventriculomegaly (6-20% of cases) and corpus callosal dysgenesis (6-10% of cases) is also present 5,9.

There is limited data available on the long-term outcome of children with Joubert syndrome. Persistent neuromotor developmental delay is a feature of surviving individuals. Patients with associated retinal dysplasia appear to have a poorer prognosis 5.

Extreme care needs to be taken when administering any agent that causes respiratory depression, as individuals with Joubert syndrome are exquisitely sensitive to these effects 5.

Genetic counseling is required as the condition is autosomal recessive.

It is named after the French neurologist Marie Joubert who first described the condition in 1969.

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