HYPOPLASIA OF THE CEREBELLAR VERMIS AND COGNITIVE DEFICITS IN SURVIVORS OF CHILDHOOD LEUKEMIA

Background: Neurodevelopmental evidence of the cerebellum's protracted course of postnatal development suggests that it is particularly sensitive to early toxic insult from cancer therapy. If this is the case, one would expect that there is a relationship between the pattern of neuropsychological and magnetic resonance imaging deficits and that both may indicate cerebellar abnormalities. Objective: To investigate the profiles of neuropsychological functions and the morphologic features of the cerebellum, using in vivo magnetic resonance imaging planimetry in survivors of acute lymphoblastic leukemia (ALL) treated with radiation and chemotherapy. Design: Thirteen survivors of childhood ALL with onset at age 2 to 5 years and a uniform protocol of treatment involving cranial radiation of 24 Gy and five doses of intrathecal methotrexate sodium participated in the study. Ten controls matched the patients in age and socioeconomic status. Each child was assessed with a comprehensive battery of neuropsychological tests and with magnetic resonance imaging of the brain. Measurements: The neuropsychological scores were transformed into z scores and clustered into right and left hemisphere measures. Planimetric measures of the cerebellar vermis and pens were collected in the midsagittal plane. Results: Consistently observed in survivors of ALL were the following: (1) significant cognitive deficits in visual-spatial-motor coordination and figural memory, functions commonly related to the right side of the brain; and (2) hypoplasia of the cerebellar vermis, lobuli I through V and particularly VI to VII. Lateralization of the neurobehavioral deficits was not reflected in structural brain abnormalities. Conclusions: Coexistence of the cerebellar hypoplasia and visual-motor coordination and memory deficits supports the neurodevelopmental approach to brain sequelae in survivors of ALL; it also suggests significance of the cerebellum for both motor and complex nonmotor cognitive processing.