a large posterior fossa hypointense lesion
with cerebellar hypoplasia
anterior extent of the lesion and a positive
“molar tooth sign”
a positive “molar tooth sign”
Diagnosis:
Joubert syndrome.
DISCUSSION
Joubert syndrome is a genetic disorder characterized by the absence or underdevelopment of the
cerebellar vermis and malformation of the brain stem. Because of the lack of normal decussation of
the superior cerebellar fiber tracts, the mid-brain gives the characteristic “molar tooth sign”.
Patients usually present with ataxia, hypotonia, nystagmus, dysmorphic facies, and developmental
delay.
