**6. Effect of chemotherapy on cognition**

Cognitive impairment observed in children with medulloblastoma who had treated with RT. These deficits were prominent attention deficits correlated with impaired math and reading

Hoppe-Hirsch et al. [87] conducted a study comparing intellectual outcomes of children diagnosed with ependymomas or medulloblastomas, treated with whole-brain radiotherapy (WBRT), and found that only 10% of medulloblastoma patients had an IQ above 90 after 10 years compared to 60% of ependymoma patients, and this result attributed to cerebral

Posteroir fossa irradiation with 35 Gy was associated with lower cognitive scores than that irradiated with a dose 25 Gy, and IQ and verbal comprehension seems to be dose-dependent

Large-sample controlled clinical trial conducted by Klein et al. [75] assed mid-term and longterm neuropsychological function following the RT in LGG. In the study, 195 patients with LGG compared with 195 healthy controls and 100 patients with hematological malignancies with mean follow-up period of 6 years. The results revealed that patients with LGG had lower scores in all cognitive domains than the controls and hematological patients, and the main cause of cognitive deficits was the tumor, but cognitive deficits of memory domain was

Another study was conducted on those patients after 12-year follow-up and found that the attentional deficits deteriorated in patients who received RT. The progressive decline was

Decline in nonverbal memory was observed in patients with LGGs years post-RT, despite the long-term improvements which observed in verbal memory, attention, and executive function [84]. Postoperative RT in LGG was found to have a significant risk of long-term

The irradiated volume of brain tissue has great impact on cognition. A study conducted by Jalali et al. [91] reported that patients who treated with stereotactic conformal RT presented with unchanged overall mean full-scale IQ, while one third of patients showed a >10% decline

Chang et al. [92] found that cognitive deficits after the treatment with sterotactic radiosur‐ gery (SRS) had lower incidence than that in patients treated with whole-brain radiotherapy (WBRT). The cognitive deficit in learning and memory function was (24%) in patients treated

Intensity-modulated radiotherapy (IMRT) is a type RT technique in which more sparing of

Hippocampal sparing with IMRT reduced doses delivered to hippocampus by 87% (0.49 Gy)

Proton beam therapy results in greater sparing of healthy brain tissue and allows for a moretargeted delivery of radiation and smaller penetration of tissue beyond the tumor [94]. The

normal brain tissue can be achieved and precise contouring to the tumor tissue.

observed only in patients who received RT with dose per fraction more than 2 Gy.

found even in patients received <2 Gy dose per fraction [89].

with SRS and (52%) in patients treated with WBRT and SRS.

leukoencephalopathy and cognitive impairment [90].

in full-scale IQ as compared to baseline.

and 81% (0.73 Gy) [93].

performance [86].

250 Neurooncology - Newer Developments

hemisphere radiation.

in posterior fossa tumors [88].

Chemotherapy treatment in brain tumor seems to have a role in cognitive deficits. There is association between chemotherapy used in the treatment of brain tumor and an increased risk for cognitive dysfunction especially, if it is administered with RT.
