Neurocognitive abnormalities have been reported in other groups of cancer survivors besides patients with CNS tumors and ALL. In a study of adult survivors of childhood non-CNS cancers (including ALL, n = 5,937), 13% to 21% of survivors had impairment in task efficiency, organization, memory, or emotional regulation. This rate of impairment was approximately 50% higher than that in the sibling comparison. Factors such as diagnosis before age 6 years, female gender, cranial radiation therapy, and hearing impediment were associated with impairment.
Stem cell transplantation
Cognitive and academic consequences of stem cell transplantation in children have also been evaluated. In a report from the St. Jude Children's Research Hospital in which 268 patients were treated with stem cell transplant, minimal risk of late cognitive and academic sequelae was seen. Subgroups of patients were at relatively higher risk, including those undergoing unrelated donor transplantation, receiving total-body irradiation, and developing graft-versus-host disease (GVHD). However, these differences were small relative to differences in premorbid functioning, particularly those associated with socioeconomic status.
Neurocognitive function of pediatric patients with hematologic malignancies who had undergone hematopoietic stem cell transplantation (HSCT) was evaluated prior to HSCT and then at 1, 3, and 5 years post-HSCT. In this series of 38 patients who had all received intrathecal chemotherapy as part of their treatment, significant declines in visual motor skills and memory test scores were noted within the first year posttransplant. By 3 years posttransplant, there was an improvement in the visual motor development scores and memory scores, but there were new deficits seen in long-term memory scores. By 5 years posttransplant, there were progressive declines in verbal skills, performance skills, and new deficits seen in long-term verbal memory scores. The greatest decline in neurocognitive function occurred in patients who received cranial irradiation either as part of their initial therapy or as part of their HSCT conditioning.
Most neurocognitive late effects are thought to be related to white matter damage in the brain. This was investigated in children with leukemia who were treated with HSCT. In a series of 36 patients, performance on neurocognitive measures associated with white matter was compared with performance on measures associated with gray matter. Composite white matter scores were significantly lower than composite gray matter scores.
Neurologic complications may be predisposed by tumor location, neurosurgery, radiation therapy, or specific neurotoxic chemotherapeutic agents. In children with CNS tumors, mass effect, tumor infiltration, and increased intracranial pressure may result in motor or sensory deficits, cerebellar dysfunction, and such secondary effects as seizures and cerebrovascular complications.
Clinical or radiographic leukoencephalopathy has been reported after cranial irradiation and high-dose systemic methotrexate administration. Younger patients and those given radiation doses greater than 24 Gy are more vulnerable to this complication. White matter changes may be accompanied by such neuroimaging abnormalities as dystrophic calcifications, cerebral lacunae, and cerebral atrophy.