Cerebal Coenurosis
- Background:
- Cerebral coenurosis is a rare cestodal helminthic infection caused by metacestodes of Taenia multiceps or T. serialis. A metacestode is a polycephalic cyst that varies from a few millimetres to centimeters. Multilocular coenuri are more often encountered in brain infections by T. multiceps. Unlike cysticercus, the cysts contain jelly-like fluid and 50 to several hundred protoscolices. Dogs and sheep are the common hosts, and humans become intermediate hosts by ingesting eggs.
- Key Diagnostic Features:
- Imaging shows spheroid cystic lesions that usually suppress on FLAIR imaging with rim-like enhancement.
- From a pattern recognition perspective, characteristic multiplicity of the eccentric nodules (resembling the cluster of grapes in a few instances), a pattern on T2-weighted MR sequences, is seen. This is the imaging equivalent to the profusion of protoscolices. This morphology has a distinguishing value from neurocysticercosis, where scolex is usually solitary, seen as an isolated eccentric nodule on imaging, the finding being correlated even on histopathology.
- While wall enhancement, variable calcification in the wall, mass-like lesions, and perilesional edema have been described in cases of cerebral coenurosis, they lack specificity.
- MR spectra obtained from cestodal lesions are known to have a more prominent succinate peak compared with acetate while the converse holds in an anaerobic bacterial abscess. A succinate resonance, although the signature of a parasite, does not distinguish coenurosis from the more common neurocysticercosis or hydatidosis.
- The variability of wall enhancement and the perilesional edema is evident in various case report descriptions in literature, presumably due to the different stages in the evolution and the natural course of the disease, with inflammation ensuing only in the later stages of degeneration. Parallels may be drawn to the evolution of neurocysticercosis in the colloidal-vesicular stage, wherein the cyst fluid becomes turbid (and thus only partially suppressed on FLAIR), and ensuing inflammation renders the perilesional edema and wall enhancement distinctive.
- Differential Diagnosis:
- Neurocysticercosis caused by T. solium is an important parasitic disease that requires differential diagnosis from CNS coenurosis. Coenurosis with multiple scolices in the cyst differs morphologically from cysticercosis with a single scolex in the cyst; the species are often histologically indistinguishable
- CNS tumors such as glioblastoma, metastatic brain tumors, and primary CNS lymphomas are distinguishable by their solid components and characteristic imaging features.
- Treatment:
- Surgery is the most effective treatment for coenurosis, and allows complete recovery or long-term control of the disease. Extra care should be taken to extract the inner cyst as a whole, as the cyst contains the parasite’s protoscolices. Antiparasitic therapy with albendazole and praziquantel is the treatment of choice.
