Between 70 and 80010 of cerebellar astrocytomas are found in children. Few patients are less than 1 year of age or older than 40 at the time of diagnosis. There appear to be no age peaks. Prognosis is poorest at the extremes of life, children less than 5 years old tending to suffer an early recurrence and patients in the oldest age groups having not only a very rapid recurrence but also a very low overall survival rate.

In the present study, there was a slight predominance of males although basically, when all studies are considered, the incidence appears to be equal amongst the sexes. Around puberty there appears to be an abrupt drop in the number of tumours in females and a concomitant rise in the number in males. There appears to be no relationship between sex and the length of survival.

It would appear that cerebellar astrocytomas can begin either within the vermis or one hemisphere. There appears to be no laterality, the right and left sides of the cerebellum being affected equally. In the present study, the hemispheres were affected three times more frequently than the vermis (34.807o: 12.5010). The rate of recurrence is much faster with tumours of the vermis, whilst the length of survival to death is much longer with tumours of one hemisphere at least up to 10 years after surgery. The most rapid recurrences take place in tumours which involve both hemispheres and the vermis whilst the poorest survival is associated with tumours infiltrating the brain stem. The average length of history is 18.7 months, being under forty-eight months in approximately 60010 of patients, but only greater than 60 months in 6.201o of cases. The length of history was not related to either patient age or survival time.

Most patients present with obstructive hydracephalus with or without localising symptoms. The presentation is usually chronic and intermittent but may also be acute. Symptoms generally appear only after much cerebellar tissue has been destroyed. Clinical features can be divided into four groups: those referrable to raised intracranial pressure; altered cerebellar function; visual disturbance; or cranial nerve dysfunction. Headache was found to be the most common symptom due to raised pressure and it was noted more commonly in the older patients. The rate of recurrence was slower in patients with headache, although their survival to death was not altered. Patients with raised pressure were also commonly noted to be drowsy. Drowsiness was more frequent in children than in adults but not associated with survival. Papillodoema was the most common sign referrable to raised pressure. Although it could not be related to survival, it is essential to relieve raised pressure rapidly in order to preserve vision. A substantial number of patients with large heads were noted in the present study. Ataxia was the most common sign referrable to altered cerebellar function, and found in up to 95°70 of all patients. It was more common in patients with tumours of the vermis than in those of the hemispheres, but was not related to survival. Visual disturbances, including nystagmus, diplopia, and reduced visual acuity, were more common in adults. They could not be related to survival. Cranial nerve palsies were not specifically assessed in the present study. Seventh nerve cranial palsies have been said, however, by others, to be the most reliable, localising sign in patients with cerebellar astrocytomas.