Cerebellar agenesis and diabetes insipidus.

We report on a 7-year-old female, born after a normal pregnancy at term, previously referred because of delayed psychomotor development. MRI revealed isolated cerebellar agenesis (CA) with only minute tissue remnants of the anterior vermis/paravermian anterior quadrangular lobes and pontine hypoplasia. The patient demonstrated truncal ataxia, saccadic ocular pursuit and mild gaze evoked nystagmus. At the age of 2.5 years, the girl achieved independent walking, though with a markedly ataxic gait; at the same age diabetes insipidus was recognized and appropriately treated. This association has not been reported before. At the ages of 3.5 and 6.5 years, her developmental quotient (DQ) was 65 and 60, respectively, with a very poor vocabulary and cerebellar dysarthria. The term "agenesis" is problematic as several reports describe considerable cerebellar tissue remnants and may include pontocerebellar hypoplasia. A literature review disclosed only a few patients with CA (defined in a strict sense) diagnosed in vivo by MRI. It is questionable whether asymptomatic CA occurs.