
Brain metastases are often irradiated with focused beams, as in the gamma knife or cyber knife or radiosurgery, and sometimes the whole brain is irradiated with a diffuse beam to prophylactically prevent further metastases from growing. 

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<b>Cerebral Radiation Necrosis</b>
<b>One of the toxic and late effects of brain irradiation is Cerebral Radiation Necrosis.</b> With radiation necrosis of the brain, MRI scans show the progressive deterioration of white matter.  Late delayed effects, occurring several months to many years later, are classified into diffuse white-matter injury, radiation-induced arteriopathy & stroke, with associated death of brain tissue. These reactions are due to death of brain tissue caused by radiation-damaged blood vessels. <b>Cerebral Radiation Necrosis generally occurs a few months to years after radiation therapy. Symptoms include decreased intellect, memory impairment, confusion, personality changes and alteration of the normal function of the area irradiated. </b> 

<b>Memory impairment, fine motor coordination, and other difficulties in thinking and functioning are not unusual after irradiation.  These symptoms were related to the total dose of the radiation delivered.</b> 


<b>Cerebral Radiation Necrosis  --  Annotated References</b> 

J Radiol 2002 Nov;83(11):1749-57 
<b>[CT and MRI aspects of 28 patients with cerebral radiation necrosis irradiated for ORL tumors: correlation with the radiation technique] [Article in French] </b>

...To describe and correlate with radiation therapy the occurrence of cerebral radiation necrosis in patients irradiated for nasopharyngeal or ethmoidal tumor. ... From 1986 to 1998, 1 201 patients... were treated by radiotherapy. Twenty-eight developed cerebral necrosis. ... The incidence of cerebral radionecrosis was 2.33%. The time interval between treatment and necrosis ranged from 2 months to 9 years. ... . Lesions were localized ... The doses related to the areas of necrosis ranged from 13 to 135Gy. In 2 cases necrosis was situated at the boundaries of the radiation field. Imaging follow-up showed complete (n=3) or incomplete remission (n=1), lesion progression (n=11), cerebral atrophy (n=5) and stability (n=7). ...New technologies may reduce the incidence of this complication. 
&&url PMID: 12469012 


Ann Dermatol Venereol 2002 Jan;129(1 Pt 1):41-5 
<b>[Delayed cerebral radionecrosis following radiation therapy of cutaneous squamous cell carcinomas of the head][Article in French] </b>

... Little is known of cerebral radionecrosis following radiotherapy. This may be related to their rare occurrence and/or to the difficulties in establishing diagnosis. The delay of occurrence after radiotherapy can vary between a few months and several years, and the lesions are directly correlated with the doses and the fractioning of the X-rays. Intracerebral localization of the tumour is the main differential diagnosis. Localized and cystic forms of cerebral radionecrosis can be treated by surgery. Treatment otherwise relies on systemic steroids. 
&&url PMID: 11937928 


Eur J Radiol 2001 Sep;39(3):133-8 
Late temporal lobe necrosis in patients with nasopharyngeal carcinoma: evaluation with combined multi-section diffusion weighted and perfusion weighted MR imaging. 

Late temporal lobe necrosis is a well-known and serious complication in patients with nasopharyngeal carcinoma (NPC) following radiotherapy. Owing to the close proximity to the skull base, the medial temporal lobes are inevitably included in the target volume of irradiation. ...Since late temporal lobe necrosis is probably caused by damage of the endothelium of vessels and ischemia, perfusion and diffusion mismatch might imply injured tissue but potentially salvageable brain tissue. ... 
&&url PMID: 11566238 


J Neurooncol 2001 Jan;51(2):143-50 
<b>Acute hemorrhage in late radiation necrosis of the temporal lobe: report of five cases and review of the literature.</b>
 
Hemorrhage in late cerebral radiation necrosis is a rare complication after radiotherapy ... In a review of the literature, the authors identified a total of 27 such cases. The interval period between the onset of hemorrhage and cranial irradiation is long (mean = 7.8 years). The most prominent histological feature was the proliferation of large, dilated and thin-walled new blood vessels in a background of gliosis and fibrinoid necrosis of vessels. Rupture of these thin-walled new blood vessels is the proposed mechanism of hemorrhage in this condition. 
&&url PMID: 11386411 


Int J Radiat Oncol Biol Phys 2000 Jan 1;46(1):51-5 
<b>Neurocognitive effects of therapeutic irradiation for base of skull tumors. </b>

... Nineteen patients who received paranasal sinus irradiation at least 20 months and up to 20 years before assessment were given a battery of neuropsychologic tests of cognitive function,,, . The median radiation dose was 60 Gy (range 50-68 Gy) in fractions of 1.8 to 2 Gy. 

... Memory impairment was found in 80% of the patients, and one-third manifested difficulty with visual-motor speed, frontal lobe executive functions, and fine motor coordination. Two of the patients had frank brain necrosis with resultant dementia and blindness, and three had evidence of brain atrophy. Three of the fourteen patients without documented cerebral atrophy or necrosis were disabled from their normal activities. Three patients also developed pituitary dysfunction. Neurocognitive symptoms were related to the total dose of radiation delivered but not to the volume of brain irradiated, side of radiation boost, or chemotherapy treatment. The pattern of test findings was consistent with radiation injury to subcortical white matter. 

... Radiation therapy for paranasal sinus cancer may cause delayed neurocognitive side effects. Currently, however, the development of severe adverse effects appears to be decreasing because of improvements in the techniques used to deliver radiation. Lowering the total dose and improving dose distributions should further decrease the incidence of delayed brain injury due to radiation. 
&&url PMID: 10656372 
