THE NEUROLOGICAL COMPLICATIONS OF THE RADIOTHERAPY: ASPECTS IN IMAGING F.AKID, Y.GUERMAZI, W.TURKI, I.AMMAR, S.CHAABOUNI, A.MAALEJ, S.HADDAR, KH. BEN MAHFOUDH, J MNIF Radiology department, Habib Bourguiba,Sfax, Tunisia NEURORADIOLOGY : NR 23

Introduction: Neurological complications of radiotherapy are serious and irreversible They are sources of major handicap The clinical context and imaging, mainly MRI, are the cornerstone of diagnosis of these complications The purpose of this work is to illustrate some aspects in imaging of the neurological complications of the radiotherapy

Materials and methods: Retrospective Study concerning 8 patients treated by radiotherapy for diverse causes in particular for an ENT cancer The average age varied between 14 and 41 years All our patients were treated by radiotherapy They underwent a brain MRI (n=7) and a medullary MRI (n=1).

Materials and methods: The motive was: A post therapeutic monitoring of a posterior fossa medulloblastoma (n=1 ) Routine supervision of a UCNT ( n=3 ) Right hemiparesis and aphasia following treatment of a cushing’s disease ( n=1 ) Left hemiplegia following radiotherapy for fibrillary astrocytoma ( n=1 ) Bilateral hearing loss after radiotherapy for nasopharyngeal cancer ( n=1 ) Behavior disorders with aphasia in a nasopharynx cancer ( n=1 )

Results: The MRI showed : A radio-induced cavernoma in 3 cases Acerebral radionecrosis in 4 cases A medullary radionecrosis in one case

Results:

Case 1: a b c d Axial T1 (a), T2 (b), gadolinium enhanced T1 (c) and ADC map (d) MR images obtained, 2 years after radiation therapy for nasopharyngeal carcinoma, in a 65 year old man with behavior disorders and aphasia. Oval lesion in T1 hypointensity and T2 hyperintensity in the left temporal lobe . Gadolinium-enhanced T1 image (c) shows an irregular ring-enhancing lesion with mass effect and edema . “Cerebral radionecrosis”

Case 2: a b c d MR images obtained in a 47-year-old woman with left hemiplegia following radiotherapy for glioblastoma (a) Axial T1-weighted, (b) axial T2 and (c) FLAIR showing a right fronto- temporal lesion associated to a vasogenic edema with mass effect (d)Gadolinium-enhanced T1WI image shows a ring-enhancing lesion

Case 2: e f g (e) DWI image obtained at the same patient, shows a marked hypointensity, which is typical for radiation necrosis. (f) ADC map, which corresponds to (e), shows a markedly high ADC value. (g) Spectroscopy shows a peak of lipid (arrow)

Case 3: a b c d Sagittal T1 (a), T2 (b), gadolinium enhanced T1 (c) and axial gadolinium enhanced T1 (d) MR images obtained, 3 years after radiation therapy for nasopharyngeal carcinoma, in a 46 year old man with hemiparesis. Cervical medullary lesion in T1 hypointensity (a) and T2 hyperintensity (b) extent of bulbo medullary junction to the lower edge of C7. Gadolinium-enhanced T1WI image shows an irregular ring-enhancing lesion. “medullary radionecrosis”

Case 4: a b c MR images obtained, 7 years after radiation therapy for nasopharyngeal carcinoma, in a 52 year old man (supervision) Axial FLAIR (a), axial T2*(b) and gadolinium enhanced T1 (c) MR images showing a small nodular lesion in the left frontal lobe with an heterogeneous low signal on T2* and unenhanced after injection of gadolinium. “Radio-induced cavernoma”

Discussion: Radiation therapy is considered effective in nasopharyngeal carcinoma (NPC) and other head and neck malignancies. However, it is not without morbidity, and complications can develop as a result of damage to neighboring structures. Many of the deleterious effects of radiation on the CNS are well known. These include early effects that can occur within a few weeks of the radiation therapy, such as vasogenic edema due to increased capillary permeability and vasodilation.

Discussion: Delayed effects can occur months to years after the irradiation. These include cerebral atrophy, white matter necrosis, demyelination, gliosis, and induction of neoplasm. Delayed radiation injury can also manifest as vasculopathy with hyalinization and fibrinoid necrosis of vascular walls, resulting in occlusion and infarction as well as vascular proliferative lesions such as capillary telangiectasia and cavernoma .

Discussion: Delayed radiation effects are directly proportional to dose and inversely related to fractional number The mean interval between irradiation and presentation is approximately 1 year for patients who receive a total dose of 50 Gy; however, cases of radiation necrosis have been reported as early as 3 months and as late as 19 years after radiation therapy

Discussion: The typical MRI findings of radiation necrosis are areas of cystic or fingerlike lesions of increased signal intensity in white matter on T2WI images, which frequently extend beyond the radiation portals. Recent studies using DWI have shown that the apparent diffusion coefficient (ADC) ratios in the contrast-enhancing lesion are lower in recurrent tumor than in radiation-induced injury.

Discussion: Nodular or rim enhancement may be seen, because diffuse damage to the blood-brain barrier is present, although the degree of enhancement can vary with time. Larger lesions may appear as islands of enhancement surrounded by areas nonenhancing necrosis.

Discussion: Minimal local mass effect for the size of the lesion is typical. However, reactive vasogenic edema, which often accompanies this condition, can be extensive and can produce substantial regional mass effect on adjacent structures. These findings are often nonspecific and may not permit differentiation from tumor recurrence.

Discussion: Most radio-induced cavernomas have a distinctive appearance of their nidus with little or no surrounding edema MR imaging usually shows a reticulated core of heterogeneous signal intensity with a dark peripheral rim of hemosiderin, giving a typical “popcorn” appearance in T2*-weighted gradient- echo (T2*GE)

Discussion: Specific spectroscopic changes that occur in radiation necrosis have been reported and include slight depression of NAA and variable changes in Cho and Cr. In addition, radiation necrosis may show a broad peak between 0 and 2 ppm, probably reflecting cellular debris containing fatty acids, lactate (Lac), and amino acids.

Discussion: MR spectroscopy and diffusion-weighted imaging (DWI), are not the only method used to differentiate radiation injury from recurrent tumor. Other methods that recently have been used for this purpose such as positron-emission tomography (PET), MR perfusion and CT perfusion. These techniques seem to be very promising

Conclusion: Late neurological complications of radiotherapy are rare but serious The MRI and the functional neuro-imaging are the highlight of the diagnostic The treatment remains primarily preventive