Dementia and central nervous system involvement in chronic lymphocytic leukaemia

2 patients with early-stage chronic lymphocytic leukaemia had involvement of the central nervous system causing dementia as the predominant clinical symptom. None of the patients had focal neurological abnormalities. One patient was successfully treated first with irradiation therapy to the central nervous system, and later with intrathecal administration of methotrexate. The other patient died with massive leukaemic infiltration of the central nervous system before effective treatment had been given. Although significant involvement of the central nervous system is rare in chronic lymphocytic leukaemia and usually does not occur until late in the disease, these cases show that clinically important infiltration may happen very early. The clinical picture of dementia has not been described in chronic lymphocytic leukaemia.