Visual-evoked potentials in long-term survivors of acute lymphoblastic leukemia in childhood. The German Late Effects Working Group

Clinical utility of complex assessment with evoked potentials in acute lymphoblastic leukemia survivors: comparison of various treatment protocols

BACKGROUND

One of the greatest success of pediatric hematology is a prominent improvement of survival in acute lymphoblastic leukemia (ALL). Therefore, special attention needs to be paid to long-term side effects of the treatment such as neurotoxicity. One of the few diagnostic methods that allow an objective assessment of sensory systems are evoked potentials (EP).

METHODS

The analyzed group consisted of 167 ALL long-term survivors, aged 4.9-28.4 years, without auditory, visual and sensory deviations. Patients were treated with New York (NY, n = 35), previous modified Berlin-Frankfurt-Münster (pBFM, n = 47) and BFM95 (n = 85) protocols. In order to assess the impact of radiotherapy on recorded EP, a joint analysis of NY and pBFM groups was performed. The control group consisted of 35 patients, aged 6-17 years. The analyzed patients underwent a complex assessment with visual EP (VEP), somatosensory EP (SEP) and brainstem auditory EP (BAEP) in accordance with current standards.

RESULTS

ALL treatment contributed to the shortening of wave I latency (1.59 vs 1.90, P = 0.003) and prolongation of I-III (2.23 vs 2.04, P = 0.004) and I-V (4.57 vs 4.24, P = 0.002) interwave latencies of BAEP. A significant effect was also noticed in P100 (106.32 vs 101.57, P < 0.001) and N135 (151.42 vs 138.22, P < 0.001) latencies of VEP and N18 amplitude (3.24 vs 4.70, P = 0.007) and P25 latency (21.32 vs 23.39, P < 0.001) of SEP. The distribution of abnormalities between protocols was similar in BAEP (NY - 68.6%, pBFM - 61.7%, BFM95-69.4%, P = 0.650), VEP (NY - 68.6%, pBFM - 42.5%, BFM95-58.3%, P = 0.053) and significantly different for SEP (NY - 62.9%, pBFM - 36.2%, BFM95-53.0%, P = 0.045). The harmful effect of radiotherapy was most clearly marked in numerous disturbances of SEP parameters.

CONCLUSIONS

The presented analysis indicates a high frequency of subclinical abnormalities in EP regardless of the analyzed protocol. To our knowledge current study is the largest and one of the most complex research examining the role of EP in ALL patients. The obtained results indicate the possibility of using a single, objective and non-invasive measurement of EP in ALL survivors in order to stratify the risk of developing sensory abnormalities in adulthood.

Analysis of Four Types of Leukemia Using Gene Ontology Term and Kyoto Encyclopedia of Genes and Genomes Pathway Enrichment Scores

AIM AND OBJECTIVE

Leukemia is the second common blood cancer after lymphoma, and its incidence rate has an increasing trend in recent years. Leukemia can be classified into four types: acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and chronic myelogenous leukemia (CML). More than forty drugs are applicable to different types of leukemia based on the discrepant pathogenesis. Therefore, the identification of specific drug-targeted biological processes and pathways is helpful to determinate the underlying pathogenesis among such four types of leukemia.

METHODS

In this study, the gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways that were highly related to drugs for leukemia were investigated for the first time. The enrichment scores for associated GO terms and KEGG pathways were calculated to evaluate the drugs and leukemia. The feature selection method, minimum redundancy maximum relevance (mRMR), was used to analyze and identify important GO terms and KEGG pathways.

RESULTS

Twenty Go terms and two KEGG pathways with high scores have all been confirmed to effectively distinguish four types of leukemia.

CONCLUSION

This analysis may provide a useful tool for the discrepant pathogenesis and drug design of different types of leukemia.

Visual evoked potentials after hematopoietic allogeneic stem cell transplantation in childhood

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VEP recordings were abnormal in 17% of the patients median 6 years post hematopoietic stem cell transplantation in childhood.

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Pathological VEPs were associated with decreased visual acuity.

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Pathological VEPs were not linked to irradiation, chemotherapy or malignant diagnosis.

Objective

To study visual pathway pathology detected by visual evoked potentials (VEPs) in patients treated with hematopoietic stem cell transplantation (HSCT) in childhood and to determine the impact of adverse ocular findings, somatic diseases, and conditioning regimens on the VEP results.

Methods

Ophthalmological assessments including pattern VEPs were performed in 47 of 79 patients at a median age of 15 years (range 3–21 years) in median 6 years (1–17 years) after HSCT. Somatic data were extracted from medical records.

Results

Eight patients of 47 (17%) demonstrated pathological VEPs with prolonged latencies bilaterally (n = 3) or unilaterally (n = 5) at their latest VEP test at an age of 12–18 years. A subnormal visual acuity was present in 8/11 eyes with pathological VEPs: one eye had cataract, six eyes had cataract surgery where of two had developed secondary cataracts. One eye had residual retinopathy of prematurity. Pathological VEPs were associated with decreased visual acuity (p = 0.00019) but not linked to gender, malignant diagnosis or conditioning.

Conclusion

VEP recordings showed an association with decreased visual acuity but no relationship with irradiation or chemotherapy in the present study.

Significance

VEP recordings might be of clinical value for children with an unexplained subnormal visual acuity undergoing HSCT.

A comprehensive model of the development of mental handicap in children treated for acute lymphoblastic leukaemia: A synthesis of the literature

Most clinical studies addressing sequelae in children with leukaemia are not theory-driven. Nonetheless, the role of different mediating biological (e.g. cranial irradiation, chemotherapy) and psychosocial variables (e.g. family functioning) has been empirically acknowledged. In these studies, a cause-effect relationship between biological variables and cognitive deficits, sometimes complex due to multiple agents, has been hypothesised. As for the psychosocial consequences, adaptation to the cancer-related stress has been the main focus, at both the individual and family levels. In this paper, we advocate the use of a global model for the development of handicap, derived from the International Classification of Impairments, Disabilities and Handicaps (ICIDH) by the World Health Organisation. This revised model proposes that handicap is the result of complex interactions between the characteristics of a person’s impairment, disabilities, and the characteristics of the environment. At each of these levels, risk/resilience factors are defined. This means that depending on the environmental obstacles they face, persons with an impairment or a disability may or may not experience a situation creating a handicap which is no longer seen as a stable status resulting from a disease to which the individual must adapt. By reviewing animal and clinical studies, current knowledge pertaining to leukaemia sequelae are integrated into the different levels defined by the model: organic impairment, disabilities, environmental obstacles, and handicap situation. Practical implications for research, policies, and individual treatments, and comparisons with existing models, are also outlined.

Gamma deficits as a neural signature of cognitive impairment in children treated for brain tumors

Cognitive impairment is consistently reported in children treated for brain tumors, particularly in the categories of processing speed, memory, and attention. Although tumor site, hydrocephalus, chemotherapy, and cranial radiation therapy (CRT) are all associated with poorer function, CRT predicts the greatest deficits. There is a particularly high correlation between CRT and slowed information-processing speed. Cortical gamma-band oscillations have been associated with processing behaviorally relevant information; however, their role in the maintenance of cognition in individuals with processing deficits is unclear. We examined gamma oscillations using magnetoencephalography (MEG) in children undergoing CRT to test whether gamma characteristics can be a signature of cognitive impairment in this population. We collected resting-state data as well as data from baseline and active periods during two visual-motor reaction time tasks of varying cognitive loads from 18 healthy children and 20 patients. We found that only high-gamma oscillations (60-100 Hz), and not low-gamma oscillations (30-59 Hz), showed significant group differences in absolute power levels. Overall, compared with healthy children, patients showed the following: (1) lower total high-gamma (60-100 Hz) power during the resting state, as well as during task-related baseline and performance measures; (2) no change in gamma reactivity to increases in cognitive load; and (3) slower processing speeds both inside and outside MEG. Our findings show that high-gamma oscillations are disrupted in children after treatment for a brain tumor. The temporal dynamic of the high-gamma response during information processing may index cognitive impairment in humans with neurological injury.

Neural correlates of delayed visual-motor performance in children treated for brain tumours

Both structural and functional neural integrity is critical for healthy cognitive function and performance. Across studies, it is evident that children who are affected by neurological insult commonly demonstrate impaired cognitive abilities. Children treated with cranial radiation for brain tumours suffer substantial structural damage and exhibit a particularly high correlation between the degree of neural injury and cognitive deficits. However the pathophysiology underlying impaired cognitive performance in this population, and many other paediatric populations affected by neurological injury or disease, is unknown. We wished to investigate the characteristics of neuronal function during visual-motor task performance in a group of children who were treated with cranial radiation for brain tumours. We used Magnetoencephalography to investigate neural function during visual-motor reaction time (RT) task performance in 15 children treated with cranial radiation for Posterior Fossa malignant brain tumours and 17 healthy controls. We found that, relative to controls, the patient group showed: 1) delayed latencies for neural activation in both visual and motor cortices; 2) muted motor responses in the alpha (8-12Hz) and beta (13-29Hz) bandwidths, and 3) potentiated visual and motor responses in the gamma (30-100Hz) bandwidth. Collectively these observations indicate impaired neural processing during visual-motor RT performance in this population and that delays in the speed of visual and motor neuronal processing both contribute to the delays in the behavioural response. As increases in gamma activity are often observed with increases in attention and effort, increased gamma activities in the patient group may reflect compensatory neural activity during task performance. This is the first study to investigate neural function in real-time during cognitive performance in paediatric brain tumour patients.

Almost normal cognitive function in patients during therapy for childhood acute lymphoblastic leukemia without cranial irradiation according to ALL-BFM 95 and COALL 06-97 protocols: results of an Austrian-German multicenter longitudinal study and implications for follow-up

In a multicenter study the authors prospectively investigated neurocognitive function in childhood ALL patients. Sixty-six patients (mean age at diagnosis 7.9 +/- 3.6 years, 34 female), treated with repeated intrathecal and systemical methotrexate administrations without cranial irradiation, underwent psychometric testing for intelligence, concentration, and visual-motor integration postdiagnosis and after reinduction therapy. Although there was a statistically significant decline of intellectual function after reinduction therapy for younger patients and girls (IQ scores still within normative data range), there were no differences in visual-motor performance and concentration over the time of induction therapy. Thus, neurocognitive examination should focus on younger ALL patients and girls.

Evaluation of the effects of radiotherapy to the chiasm and optic nerve by visual psychophysical and electrophysiologic tests in nasopharyngeal carcinoma

PURPOSE

To evaluate the effects of high-dose radiotherapy (RT) to the chiasm and optic nerves in locally advanced nasopharyngeal carcinoma patients by visual psychophysical and electrophysiologic tests.

METHODS AND MATERIALS

A series of visual tests, including visual evoked potentials (VEPs), contrast sensitivity, and visual field and visual acuity tests, were administered to 27 patients with locally advanced (T4) nasopharyngeal carcinoma who had undergone RT to high doses 6 to 74 months previously. As a control group, the same tests were administered to 40 unirradiated patients who had been referred to the ophthalmology department for any reason.

RESULTS

The median values of VEP latency, VEP amplitude, and contrast sensitivity and the rate of visual field defect were significantly worse in the RT group (p = 0.06, p <0.001, p <0.001, and p = 0.005, respectively). No dose-response relationship was found in any tests when 50 Gy was the cutoff value. However, a positive correlation between the interval after RT and VEP latency (r = 0.406, p = 0.003) and a negative correlation between the interval and contrast sensitivity (r = -0.499, p <0.001) was noted; no correlation could be established regarding VEP amplitude and the interval after RT.

CONCLUSION

Radiation-induced injury to the anterior visual pathways could result in an increase in VEP latency and a decrease in VEP amplitude and contrast sensitivity. This injury seems to be a continuous process developing with time.

CNS late-effects after ALL therapy in childhood. Part III: neuropsychological performance in long-term survivors of childhood ALL: impairments of concentration, attention, and memory

PURPOSE

To date, the event free survival (EFS) after treatment of childhood acute lymphoblastic leukemia (ALL) attains 80%. The survivor group is growing steadily. Therefore, the primary purpose of our study is to define the neuropsychological function and to describe which central nervous system (CNS) functions are impaired following the German ALL-BFM and COALL protocols for CNS-negative patients.

PATIENTS AND METHODS

In a cross-sectional multicenter study 121 subjects, long-term survivors of childhood ALL in first continuous complete remission were investigated. Seven years ago, the subjects were treated as standard or medium risk patients according to ALL-BFM 81, ALL-BFM 83, or COALL 82 protocols, receiving comparable treatments. According to different CNS-prophylaxes, two subgroups were compared in the study: the non-cranially irradiated MTX-group (methotrexate-group) (n = 38) and the cranially irradiated RT-group (radiotherapy-group) (with MTX i.th.) (n = 83). Intellectual and cognitive abilities of these groups were evaluated using standardized psychometric techniques. The Kaufman factors Verbal Comprehension, Perceptual Organisation and Freedom from Distractibility were calculated. Demographical and clinical data collected at the time of the diagnosis were compared between both groups. The different prognoses for patients within both groups were taken into account using a defined risk factor. Analysis of variance was conducted to relate intellectual performance to age, gender, and CNS-treatment.

RESULTS

The RT-group exhibited a lower Full Scale IQ than the MTX-group (101.2 +/- 15.9 vs. 109.9 +/- 14.9, P = 0.031). Particularly for the Kaufman factor Freedom from Distractibility the RT-group showed the lower scores (96.9 +/- 14.1 vs. 105.5 +/- 12.6, P = 0.037). Significant interactions between gender and CNS prophylactic treatment were observed for Full Scale IQ (P = 0.008), Verbal IQ (P = 0.012), Performance IQ (P = 0.024), Verbal Comprehension (P = 0.004), and Perceptual Organisation (P = 0.032).

CONCLUSIONS

Cranial irradiation in combination with MTX therapy was associated with deficits in attention, concentration, and the ability of sequencing and processing, measured by the Kaufman factor Freedom from Distractibility. Our results support the strategy of avoiding prophylactic CNS irradiation in low risk patients.

Motor nervous pathway function is impaired after treatment of childhood acute lymphoblastic leukemia: a study with motor evoked potentials

BACKGROUND

The objective was to evaluate whether motor nervous pathways are affected when patients are treated for childhood acute lymphoblastic leukemia (ALL).

PROCEDURE

Thirty-two children with ALL were studied at the end of treatment by means of motor evoked potentials (MEPs) elicited by magnetic stimulation (MS) transcranially and peripherally and underwent a detailed neurological examination. Thirty-two healthy children matched with them for age, sex, and height served as a control group.

RESULTS

The latencies of the MEPs were significantly prolonged along the entire motor nervous pathway in the patients with ALL compared with the healthy controls, indicating demyelination in the thick motor fibres. The MEP amplitudes of the distal extremities elicited by stimulation at the brachial plexus and LV spinal level were significantly lowered in the patients treated for ALL, also indicating anatomical or functional loss of descending motor fibres and/or muscle fibres. The MEP amplitudes elicited by cortical MS showed wider variation and no clear abnormalities were found. Neurological signs and symptoms were common after treatment: 41% of the patients had depressed deep tendon reflexes, 31% had fine motor difficulties and 63% gross motor difficulties, and 34% had dysdiadochokinesia. The conduction delay within the peripheral nerve was related to the post-therapeutic interval after administration of vincristine and the lesions within the CNS to the number of injections of intrathecal methotrexate.

CONCLUSIONS

The present results show adverse effects of the ALL treatment on the entire motor nervous pathways. In our experience, the measurement of MEPs by MS provides an objective, painless, and practical tool for assessing the treatment-related neurotoxicity in both the CNS and the peripheral nerves. These disturbances in the motor nervous pathways at the end of treatment raise the question of the long-term effects of ALL treatment on the motor nerve tracts, and have led us to employ MEPs to study these effects in long-term survivors of ALL.

CNS late effects after ALL therapy in childhood. Part I: Neuroradiological findings in long-term survivors of childhood ALL--an evaluation of the interferences between morphology and neuropsychological performance. The German Late Effects Working Group

The effect of cranial irradiation on possible therapy-induced morphological central nervous system (CNS) side effects of children cured from acute lymphoblastic leukemia (ALL) is controversially discussed. In a retrospective multicenter study, 118 former ALL patients in first continuous remission were investigated using cranial computerised tomography (CCT) or magnetic resonance imaging (MRI) scans to evaluate CNS related impairments. Corresponding to the different kinds of CNS prophylaxis, the patient sample was divided: group A (n = 39) receiving intrathecal methotrexate (ITMTX) and systemical medium-high-dose methotrexate (SMHDMTX), group B (n = 41) cranial irradiated (in mean 16.8 Gy) and administering ITMTX and SMHDMTX, group C (n = 38) irradiated (in mean 17.1 Gy) and getting ITMTX. Pathologic scans showed atrophy, leukoencephalopathy, calcifications or grey matter changes. These findings were compared with the neuropsychological test results. Abnormal MRI or CCI scans were found in 61/118 patients (51.7%). Fifteen belonged to group A (38.5%), 23 to B (56.1%) and 23 to C (60.5%). Patients with definite CNS changes show reduced neuropsychological test results. The prevalence of brain alterations seems to appear twice increased after lengthening the posttherapeutic interval in irradiated patients as in nonirradiated patients. Irradiated patients as an age younger than 2 years at diagnosis may show a lower prevalence for developing CNS alterations. CNS alterations are not sex-related. Children treated with cranial irradiation in combination with SMHDMTX and/or ITMTX were at greater risk of developing morphological brain alterations than patients with chemotherapy alone. These alterations are partly correlated with reduced neuropsychological performances and seem to stay with a longer posttherapeutic interval.