Cerebral sparganosis: MR imaging versus CT features.

Abstract

Fourteen magnetic resonance (MR) images of 11 patients with cerebral sparganosis were reviewed retrospectively and compared with 13 computed tomographic (CT) scans of 10 of the patients. All patients underwent both nonenhanced and contrast material-enhanced MR imaging. All white matter degenerations, which were slightly hypointense on T1-weighted images and were hyperintense on T2-weighted images, were seen as areas of low attenuation on CT scans. Better contrast between normal and degenerated brain tissues was seen at MR, and two lesions were seen that were missed at CT. The parasitic granuloma was isointense to brain parenchyma on images obtained with all pulse sequences. On two follow-up MR images, location or shape of the enhancing lesions changed, suggesting migration of the worm. A new finding of hyperintensity on T1-weighted images and hypointensity on T2-weighted images in subcortical areas probably due to petechial hemorrhages was demonstrated in eight patients only at MR. Small calcific foci, which were important diagnostic clues of cerebral sparganosis, were detected in four patients only at MR, while they were seen in eight patients at CT.

CT and MR Characteristics of Cerebral Sparganosis

“…Compared with other studies reported in the literature, 4,5,12,19 the tunnel sign in our study was our first concern because it represented the migration of the worm. Although other imaging findings, such as the bead-shaped enhancement and white matter degeneration, were also reported, our study integrated imaging data, clinical history, and ELISA.…”

“…The larvae may migrate through the loose connective tissues of the foramina of the skull base around the nerves or vessels. 19 In our study, 12 patients (48%) had a history of eating raw or uncooked frog or snake that was infected with sparganum. They lived in rural areas where the raw flesh of frogs, snakes, or chickens were considered tonic.…”

“…The less common sites were the basal ganglia, insula, and cerebella. 19 The primary characteristic of cerebral sparganosis is that the live worm migrates with undulating motion. The migrating worm makes a tunnel along the track of motion.…”

“…19,20 In particular, metastatic brain tumors mimic cerebral sparganosis on CT and MR imaging, but metastatic tumors often have a mass effect to compress the ventricle, and sparganosis has adjacent ventricular dilation. On postcontrast MR images, sparganosis showed the tunnel sign, but metastatic tumors and other inflammatory granulomas did not.…”

“…19,23 The live worm was approximately 5 to 18 cm long, whitish, and thread shaped, with serpiginous peristalsis. The degenerated worm in the brain was usually surrounded by collagen fibers, inflammatory cells, and gliosis.…”