Objective: To report 3 adult cases of delayed radiation induced parkinsonism, with latency ranging from 1 to 40 years. .

Background: Unequivocal radiation induced parkinsonism has been so far reported only in 2 pediatric patients. We here report 3 adult patients, with recent and remote history of cranial radiation therapy, presenting with parkinsonism.

Methods: Case series.

Results: We report 3 patients, 2 men and 1 woman, who were treated for intraparenchymal tumor with resection, chemotherapy and whole brain radiation. One patient developed leucoencephalopathy and parkinsonism within one year of treatment, while the other developed it 7 years after completion and the 3rd one developed dementia, parkinsonism and cerebral infracts 40 years after whole brain radiation. Brain MRI showed diffuse confluent hyperintensity in the deep white matter compatible with microvascular ischemic or post therapeutic change in all 3 patients, with additional calcifications in the left temporal lobe and a small subacute infarct in the right occipital lobe in one of them. DAT scan was obtained in one patient and showed slight decrease in dopamin uptake in the right putamen, not consistent with the severity of parkinsonism observed on examination. All patients failed a trial of carbidopa/levodopa. The chemotherapy they had been exposed to was either not reported to cause parkinsonism or leucoencephalopathy, or given 7 to 40 years before onset of symptoms, and was thus unlikely to have contributed to the symptoms. Indeed, neurological complications of chemotherapy typically develop within a few months of the completion of the course. On the other hand, radiation therapy induced atrophy, calcification, leukoencephalopathy and necrosis are known to occur years later. We felt that the brain radiation exposure was responsible for levodopa resistant parkinsonism, cognitive decline and diffuse leukoencephalopathy, most likely through a delayed radiation-induced vasculopathy.

Conclusions: Although rare, radiation therapy induced parkinsonism should be suspected in a patient with a history of cranial radiation therapy and presenting with parkinsonism and leucoencephalopathy, and the latency form radiation exposure to clinical manifestation may vary from 1 to 40 years.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/1-to-40-years-later-delayed-effects-of-brain-radiation-presenting-as-parkinsonism/