MR imaging of neurocysticercosis

Neurocysticercosis presenting to the emergency department as a pure motor hemiparesis

We report the case of a 23-year-old male who presented to the emergency department (ED) with an isolated right-sided pure motor hemiparesis (PMH). An unenhanced computed tomography (CT scan) revealed a hypodensity in the area of the left parasagittal motor strip. The patient then experienced a Jacksonian type of seizure involving his right leg and was treated with intravenous phenytoin and dexamethasone. A second CT scan performed with contrast was thought to be consistent with a cerebral abscess with surrounding white matter edema. Surgical findings were consistent with neurocysticercosis. The patient was treated with praziquantel with nearly full recovery. Worldwide, cysticercosis is the most common CNS parasite. Because of immigration from endemic areas, cysticercosis has become more common in the United States. Patients with neurocysticercosis may arrive in the ED with a wide variety of unusual presentations. In this case, the PMH syndrome was caused by a solitary lesion in the motor strip. This report describes a case of PMH due to neurocysticercosis secondary to local mass affect alone. The literature of neurocysticercosis and PMH is reviewed and the pathogenesis, clinical presentation, and therapy are discussed.

Lesions involving the fourth ventricle evaluated by CT and MR: a comparative study

A retrospective review of 21 patients with lesions involving the fourth ventricle was performed to determine the relative capability of computed tomography (CT) and MR for detection, characterization, localization, and diagnosis. Lesions involving the fourth ventricle included ependymoma (three), subependymoma (one), glioma (five), cysticercosis cyst (three), medulloblastoma (three), bleeding into the fourth ventricle (two), epidermoid cyst (two), "trapped" fourth ventricle (one), and lymphomatoid granuloma (one). Posterior fossa lesions that displaced but did not invade the fourth ventricle were excluded. Lesion detectability on CT was judged excellent in ten, good in 8, and fair or poor in 3. Detectability of lesions by MR was judged excellent in 16 and good in 5. There was complete agreement on lesion extension between CT and MR in 6 lesions, mild disagreement in 4, and moderate to significant disagreement in 11. Preoperatively, MR alone correctly diagnosed seven lesions, and CT alone correctly diagnosed three lesions. A review of the combined scans (after the correct diagnosis was given) showed both CT and MR were equal in the diagnosis of 14 lesions, MR better than CT in six, and CT better in one. There was complete agreement on both CT and MR with the surgical/pathologic findings in three lesions. Both studies proved disappointing in their ability to make the correct histologic diagnosis, probably because CT and MR characteristics may not always offer a definitive diagnosis and because of the wide spectrum of pathologic processes that may involve the fourth ventricle.

Unusual MR manifestations of neurocysticercosis

MR and CT features of neurocysticercosis are variable and depend fundametally on the stage in evolution of the infection, location, number and size of the worm. The authors retrospectively evaluated MR images obtained on a 2.0T superconducting unit in 22 neurocysticercosis patients and observed various MR features including some new findings. A variety of MR findings are presented with special reference to six case reports. The features include: (1) a large simple cyst containing both internal septations and a scolex; (2) suprasellar racemose cysts mimicking other cysts, (3) a fourth ventricular cyst readily depicted by aid of CSF flow-void in the sagittal plane; (4) degenerating cysts showing "white target" appearance; (5) granulomatous lesions having a "black target" appearance; and (6) a meningitic form showing Gd-DTPA enhancement of basal cisterns and of a subacute infarct.