Teaching Case

A 32-year-old male patient presented with chronic daily headache for more than 6 months. There was no fever, seizure, visual problem or focal motor deficit.

Contrast-enhanced CT of the brain showed enlargement of the subarachnoid space at the interhemispheric fissure. There was a lobulated cystic lesion without contrast-enhancement and with no mass effect on the anterior cerebral arteries, which pass through without being displaced. (Fig. 1)

MRI showed multiple lobulated, cystic lesions in the anterior pericallosal space, deforming the knee of the corpus callosum. (Fig. 2) The cyst content appears similar to CSF on the T1-and T2-weighted images. There is no surrounding oedema on the fluid-attenuated inversion recovery image or enhancement after the intravenous administration of contrast material. (Fig. 3) The round structure within the cyst with subtle contrast-enhancement represents the scolex. (Fig. 4).

Serological tests detected antibodies specific for T. solium antigens in the cerebrospinal fluid and the patient was successfully treated with albendazole and steroid drugs for 8 weeks. Follow-up MRI showed disappearance of lesions. (Fig. 5)

Neurocysticercosis (NCC) is the most common parasitic disease of the CNS and it represents one of the most prevalent causes of acquired epilepsy in developing countries. [1-3] NCC is a brain infection caused by the encysted larval stage (cysticercus) of the pork tapeworm Taenia solium.

There are two forms of NCC based on the location of the parasite: parenchymal and extraparenchymal.
The cysticerci in the brain parenchyma is the most common presentation manifesting as a focal lesion surrounded by oedema. There are four pathological stages that depict the natural evolution of neurocysticercosis: the vesicular stage, the colloidal stage, the granular nodular stage, and finally, the nodular calcified stage. [1, 4]
Extraparenchymal sites include subarachnoid spaces, basal cisterns, and within the ventricles and it is possible to have a combination of these types. [1] This form is also termed the racemose variant of NCC because the groups of cysts appear macroscopically as a cluster of grapes.
Racemose NCC is characterised by an excessive growth of cystic membranes following the degeneration of the scolex. [3] The degenerated vesicle wall produces an intense inflammatory reaction, fibrosis and progressive thickening of the leptomeninges. [1, 3, 4] It presents with hydrocephalus, mass effect and meningitis. Less commonly, this inflammation process may involve the arteries, which can result in infarcts, transient ischaemic attacks, and cerebral haemorrhage. [1, 2, 5]

The diagnosis is quite challenging and based in the neuroimaging. Racemose NCC can be missed in CT examination, but is easily visualised in MRI, and particularly in three-dimensional (3D), very heavily T2-weighted sequences, as multiple cystic lesions located within subarachnoid space. [1] The cysts are usually larger than in the parenchymal forms and have a multilocular appearance, tend to displace neighboring structures and behave as lesions with a mass effect. The intensity signal is similar to that of the cerebrospinal fluid and normally do not show significant contrast-enhancement. [4] Cysticerci usually do not contain scolices; however, when they are visible its appearance is practically pathognomonic. [1, 4]

Differential diagnosis of racemose NCC has to be made from arachnoid cysts, porencephaly, hydatid disease, cystic astrocytoma and colloid cyst of third ventricle. [3]

The treatment modalities include cysticidal agents, corticosteroids and anti-epileptic drugs. Praziquantel and albendazole are cysticidal drugs that are effective in the treatment of all forms of NCC. [1] Surgical management can be needed to remove the cyst or to insert a shunt to treat hydrocephalus. [1, 3]