Choroid plexus carcinoma is a rare and highly aggressive malignant type of choroid plexus tumor (see this term) occurring almost exclusively in children, presenting with cerebrospinal fluid obstruction in the lateral ventricles (most common), the fourth and third ventricles or in multiple ventricles, leading to hydrocephalus and increased intracranial pressure, and manifesting with nausea, vomiting, abnormal eye movements, gait impairment, seizures and enlarged head circumference.

Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- oder overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).