[Paraneoplastic cerebellar degeneration].

Paraneoplastic cerebellar degeneration (PCD) is a rare complication of systemic cancer. PCD may present as a "pure", severe pan-cerebellar syndrome of subacute progression or be only one clinical feature in the setting of extensive CNS disease. The most characteristic form of "pure" PCD is associated with the presence of an anti-Purkinje cell antibody (AB), called anti-Yo, in patients with breast or ovarian cancer. The primary tumor is very often unknown when the cerebellar signs occur, and extensive investigations, including laparotomy or prolonged follow-up may be required to demonstrate its presence. More rarely, others AB than anti-Yo are discovered during PCD. Almost 50% of patients with "pure" PCD do not have circulating anti-neuronal AB. In the cases, the primary cancer is more often known and the clinical course of the cerebellar syndrome may be slower. Cerebellar degeneration may also occur during paraneoplastic encephalomyelitis. In this setting, the cerebellar signs which may be isolated at the onset, become associated with other signs of neuraxis involvement (limbic encephalitis, brainstem encephalitis, myelitis and particularly, subacute sensory neuronopathy) during the course of the disease. When a paraneoplastic encephalomyelitis is associated with a small cell lung cancer, an antineuronal AB called anti-Hu is frequently found. Finally PCD may be associated with the opsoclonus-myoclonus syndrome with the Lambert-Eaton syndrome.