Leukaemia

Indirect manifestations are represented by haemorrhage secondary to thrombocytopenia and infection secondary to low white blood cell counts. With a markedly elevated white blood cell count (greater than 150.000/mm3) leukostasis may plug the cerebral vessels and cause infarctions. Indirect CNS manifestations of leukaemia are observed in all types of leukaemias.

Direct manifestations of leukaemia depend on the specific form.

Acute myelogenous leukaemia may affect the CNS in the form of granulocytic sarcoma or chloroma, a tumour that originates in subperiosteal bone both in craniofacial and spinal epidural sites. Chloroma derives its name from the fact that it fades from an initial green colour when it is exposed to light and may precede the overt manifestions of leukaemia by up to one year.

Leptomeningeal invasion occurs as a frequent complication of all types of acute leukaemias. The infiltrate spreads along the arachnoid into the Virchow Robin spaces, secondarily affecting the adventitia of arterioles. Cranial nerve signs, seizures, cognitive deficit or hydrocephalus along with diabetes insipidus or obesity due to hypothalamic involvement are common clinical manifestations, but leptomeningeal involvement may sometimes only be revealed by CSF cytology. The prognosis for acute leukaemia was poor before therapy directed at the eradication of leptomeningeal metastases was introduced in the early 1960s, owing to the fact that antileukaemic drugs do not achieve therapeutic levels in the CSF. With combined craniospinal radiation and intrathecal chemotherapy the incidence of CNS relapse has declined dramatically.

Chronic leukaemias rarely affect the CNS. Chronic myelogenous leukaemia may produce leptomeningeal metastases when it enters into blast crisis.

GS