Teaching Case

Vertigo, malaise, nausea and ataxia in a 53 year old female patient. MR examination of the brain shows a 4 cm lesion in the right cerebellar hemisphere which appears hyperintense in T2 weighted, hypointense in T1 weighted images. This mass was compressing the fourth ventricle, the cerebellar vermis and cerebellar peduncles. After i.v. gadolinium administration, a single area of enhancement was seen in the posterior margin of the lesion.

A 53-year-old woman presented with a 10 days history of vertigo, malaise and nausea. She had no pertinent history, apart from a similar episode 10 years earlier, which had resolved by itself, and no investigations had been perfomed at the time. The only relevant finding at physical examination was ataxia. Routine blood examinations were unremarkable.

The MR findings are consistent with pilocytic cerebella astrocytoma. The patient underwent surgery for this mass, and pathological examination confirmed the radiological diagnosis. Pilocytic cerebellar astrocytoma is the most common posterior fossa tumor in the child, but it is uncommon in the adults. We present the MR imaging in an adult patient with a large pilocytic astrocytoma of the right cerebellar hemisphere. A 53-year-old woman presented with a 10 days history of vertigo, malaise and nausea. She had no pertinent history, apart from a similar episode 10 years earlier, which had resolved by itself, and no investigations had been perfomed at the time. The only relevant finding at physical examination was ataxia. Routine blood examinations were unremarkable.the patient underwent MR imaging of the brain with i.v administration of gadolinium. MR showed in the right cerebellar hemisphere a 4 cm well-defined area of increased signal in T2 weighted images, ; patchy areas of increased signal were also noted around this mass, which was compressing the fourth ventricle, the cerebellar vermis and cerebellar peduncles. After contrast administration, a single area of enhancement was seen in the posterior margin of the lesion. The findings are consistent with a pilocytic astrocytoma of the right cerebellar hemisphere: this kind of tumor is mainly cystic and usually has one or more areas of solid component, which show contrast enhancement, along the borders of the cystic area. Between 70 and 80% 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 of 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 (34.8%: 12.5%). The rate of recurrence is much faster with tumors 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 60% of patients, but only greater than 60 months in 6.2% of cases. The length of history is not related to either to the prognosis or the chance of tumor recurrence.