Objective: To describe a patient who presented with subacute and reversible post-radiotherapy parkinsonism (<2 months), allowing treatments to be weaned; and then delayed post-radiotherapy parkinsonism  (>3years) requiring resumption of L-DOPA-therapy ¹.

Background: With the rising incidence rates for brain tumors and the resutlng increased exposure to cranial radiotherapy, clinicians might become more exposed to post-radiotherapy parkinsonism. It can occur within a wide latency range, from between a few weeks and 39 years post-radiotherapy, and to date, only a few cases have been reported ^2,3.

Method: The patient was diagnosed at the age of 16 years with a thalamic and midbrain dysgerminoma. After partial tumor resection, the patient received chemotherapy followed by radiotherapy. Less than two months after the initiation of the radiotherapy, without any evidence of tumor progression on imaging, the patient developed severe parkinsonism and encephalopathy requiring intensive care unit admission. With supporting measures and high doses of L-DOPA-therapy, ten months later, without any significant modification of his medication, the patient’s parkinsonism started to improve. Over the following 8 months, the improvement was so dramatic that medications could be stopped. At the adult age of 19, the patient again developed akinetic-rigid parkinsonism and cervical dystonia. DAT Scan showing clear decreased putaminal dopamine uptake, worse on the left. The parkinsonism remained levodopa responsive. The patient reached the stage of motor fluctuations 5 years later, with subsequent use of a Duodopa pump therapy. Cervical dystonia remained refractory, with no response to the various therapies tried.

Results: Whereas immediate and subacute parkinsonism induced by radiotherapy may be reversible, delayed parkinsonism (>6 months) is considered permanent. This could be explained by a different underlying pathophysiology ⁴. In the case of subacute post-radiotherapy parkinsonism, the suggested mechanism is vasogenic edema, whereas hypoxia-induced vasculopathy is suggested for delayed postradiotherapy parkinsonism. Levodopa treatment is generally unsatisfactory; however, it may rarely respond to levodopa.

Conclusion: This case illustrates the need for long-term follow-up of cranial radiotherapy patients, and that initial regression of post-radiotherapy parkinsonism does not guarantee long-term outcome.

References: 1. Bernard G, Chouinard S. A unique pediatric case of radiation-induced parkinsonism. J Pediatr Neurol. 2011;9(1):123-126. doi:10.3233/JPN-2010-0448
2. Surisetti BK, Prasad S, Holla VV, Kamble N, Yadav R, Pal PK. Movement Disorders Associated With Radiotherapy and Surgical Procedures. J Mov Disord. 2023;16(1):42-51. doi:10.14802/jmd.22092
3. Mehanna R, Jimenez-Shahed J, Itin I. Three Cases of Levodopa-Resistant Parkinsonism After Radiation Therapy. Am J Case Rep. 2016;17:916-920. doi:10.12659/ajcr.900537
4. Nolan CP, DeAngelis LM. Neurologic complications of chemotherapy and radiation therapy. Contin Minneap Minn. 2015;21(2 Neuro-oncology):429-451. doi:10.1212/01.CON.0000464179.81957.51

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