Introduction

Several mechanisms are involved in the neurologic insults seen in cancer patients. The most common lesions are due to primary or metastatic tumors. A second group of disorders is caused either by specifically antineoplastic treatments such as surgery, radiation or chemotherapy (Hildebrand, 1990) or by supportive therapies frequently used in cancer patients. The incidence of central nervous system (CNS) infections and of vascular lesions is also increased in patients with malignant diseases. In addition, infectious agents (Armstrong, 1976, 1977) and the causes of stroke (Graus et al., 1985) differ from those found in a general population. Finally, when all these etiologies are ruled out, one has to consider the possibility of paraneoplastic disorders resulting from a remote effect of cancer on the nervous system (Posner, 1995). In fact, all these pathogenic mechanisms are represented in the cerebellar disorders occurring in cancer patients.

The incidence of cerebellar lesions in a cancer population is not easy to assess from the literature. Gait ataxia is probably the most conspicuous sign of cerebellar dysfunction, but not all cancer patients described as ataxic have a cerebellar lesion. For example, it is unclear whether ataxia observed in patients treated with procarbazine or hexamethylmelamine is caused by a cerebellar or a peripheral nerve lesion.

In all the diseases considered in this chapter, the cerebellar insult has been clearly established.

Clinical presentation

Cerebellar symptoms and signs are due either to intrinsic lesions of the cerebellum, which are considered elsewhere in this volume, or to mass effect. The latter is mainly associated with tumors or cerebellar hematomas creating displacement of posterior fossa structures (herniations), obstructive hydrocephalus, and intracranial hypertension.