Corpus callosal signal changes in patients with obstructive hydrocephalus after ventriculoperitoneal shunting

BACKGROUND AND PURPOSE: Few reports have documented signal abnormalities wi thin the corpus callosum on MR studies obtained after ventricular decompres sion in patients with hydrocephalus. Our purpose was to establish the frequ ency of this finding in shunted patients and attempt to elucidate its cause and clinical significance. METHODS: All patients with hydrocephalus shunted between 1989 and 1999 with postoperative MR studies available for review were included in the study g roup. Imaging analysis consisted of documenting hypointense signal on T1-we ighted sagittal images and hyperintense signal on double-echo T2-weighted a xial images within the corpus callosum. RESULTS: Characteristic signal abnormalities in the corpus callosum were no ted in nine of 161 patients with shunted hydrocephalus studied with MR imag ing, All nine patients were asymptomatic in regard to these MR findings. Co mparison with preoperative scans and surgical records revealed that all pat ients with signal changes on postshunt scans had chronic obstructive hydroc ephalus at presentation. Preshunt MR images were notable for marked elevati on of the corpus callosum, which subsequently descended after ventricular d ecompression, suggesting that the cause of the signal changes was related t o compression of the corpus callosum against the rigid fair. CONCLUSION: Signal abnormalities within the corpus callosum after ventricul ar shunting for obstructive hydrocephalus are not uncommon and are probably produced by compression of the corpus callosum against the fair before ven tricular decompression, This distinctive appearance should not be mistaken for significant disease. Recognition of this pattern of signal abnormality will help avoid unnecessary intervention.