Brain Radiation-Related Black Dots on Susceptibility-Weighted Imaging

Abstract

SUMMARY -Small blood vessel injury is a feature of post irradiation brain. Susceptibility weighted imaging (SWI) is a technique that exploits the magnetic properties of tissues

Susceptibility-weighted imaging in stroke-like migraine attacks after radiation therapy syndrome

“…In such instances, based solely on the presence of gyriform enhancement on postcontrast T1WI, the differential diagnosis also includes meningoencephalitis, recurrent tumor, subacute stage of infarction, limbic encephalitis (if involving the temporal lobe), or even vasculitis [3,14]. Thus, SWI could be an ancillary technique to demonstrate the numerous punctate susceptibility hypointensities (presumably RICHs) that are visualized many years after cranial irradiation, as seen in each of the patients described herein; this finding of multiple susceptibility hypointensities (presumably RICHs) points to the correct diagnosis [15][16][17][18][19]. In such patients, reaching the appropriate diagnosis can prevent unnecessary therapy such as medication (if meningitis is suspected), further irradiation (if recurrent tumor is suspected), or surgical biopsy.…”

“…SWI is more sensitive than most other MRI techniques, including gradient echo T2*WI, in detecting frank hemorrhage or microhemorrhage [10,15,17,18,20]. Several studies have described the appearance of variably sized hemorrhagic foci on MRI following cranial irradiation; these lesions have been referred to as RICHs, most often appearing as punctate, 1-5-mm sized hypointense foci on SWI, lacking edema or enhancement after gadolinium administration [12,15,21]. Histologically, specimens have shown clusters of dilated small caliber vessels with thickened, hyalinized walls surrounded by hemosiderin, attributed to radiation-induced Btelangiectasias^that have also been equated with cavernomas on histology [9,15,19].…”

“…Several studies have described the appearance of variably sized hemorrhagic foci on MRI following cranial irradiation; these lesions have been referred to as RICHs, most often appearing as punctate, 1-5-mm sized hypointense foci on SWI, lacking edema or enhancement after gadolinium administration [12,15,21]. Histologically, specimens have shown clusters of dilated small caliber vessels with thickened, hyalinized walls surrounded by hemosiderin, attributed to radiation-induced Btelangiectasias^that have also been equated with cavernomas on histology [9,15,19]. Such foci typically do not enlarge over time, raising another possibility that these are simple microhemorrhages rather than vascular malformations [15].…”

“…Histologically, specimens have shown clusters of dilated small caliber vessels with thickened, hyalinized walls surrounded by hemosiderin, attributed to radiation-induced Btelangiectasias^that have also been equated with cavernomas on histology [9,15,19]. Such foci typically do not enlarge over time, raising another possibility that these are simple microhemorrhages rather than vascular malformations [15]. One scenario may cause consternation in cancer patients who received brain irradiation; the finding of new susceptibility hypointensities on SWI may raise the possibility of metastases, but their lack of enhancement on postcontrast T1WI suggests RICHs [15].…”

“…Such foci typically do not enlarge over time, raising another possibility that these are simple microhemorrhages rather than vascular malformations [15]. One scenario may cause consternation in cancer patients who received brain irradiation; the finding of new susceptibility hypointensities on SWI may raise the possibility of metastases, but their lack of enhancement on postcontrast T1WI suggests RICHs [15]. Previously, it was believed that SMART syndrome is entirely reversible; however, Black et al have reported that it may result in permanent neurologic or imaging sequelae [1][2][3][4][5].…”