Isolated cysticercal infestation of extraocular muscles: CT and MR findings.

PURPOSE

We sought to document the appearance of isolated cysticercal infestation of single extraocular muscles on MR and CT studies, and to compare these findings with results of histopathologic examination.

METHODS

Six MR and three CT examinations of the orbits of six patients were reviewed. Histopathologic confirmation of the diagnosis was available in three patients, and response to specific medical therapy was available in one. In all, the imaging findings were considered highly suggestive of cysticercal infestation.

RESULTS

Typically, the affected extraocular muscle showed fusiform enlargement of its belly and contained a well-defined, spherical cyst with a nodule attached to its wall. The mural nodule was identified in all six cases with varying degrees of visibility. It was best seen on the CT examinations and in all cases in which contrast material had been administered. The nodule and the enlarged muscle showed intense enhancement on the contrast-enhanced studies. Imaging studies of the brain showed no evidence of cerebral cysticerci in any of the patients.

CONCLUSION

The MR and CT appearance of isolated infestation of single extraocular muscles by the larva of the pork tapeworm Taenia solium is quite characteristic and often diagnostic of this condition.