The diagnosis of neurocysticercosis: a closed question?

In this issue, Arquivos de Neuro-Psiquiatria publishes three articles about the diagnostic aspects of neurocysticerco-sis (NC). I think it is very important to discuss some aspects of this disease. WHO considers that NC is the main disease of the central nervous system (CNS) caused by parasites 1. NC may be the consequence of two distinct morphological forms of the larval form of Taenia soli-um: Cysticercus cellulosae and Cysticercus racemosus 2. These two different morphological forms are responsible for two very distinct clinical presentations of NC, although they may coexist in some patients. Most publications about NC are concerned with the more frequent parenchy-matous form of NC caused by Cysticercus cellulosae. This form has a scolex detectable on computed tomography (CT) or magnetic resonance imaging (MRI). The evolutive phases of the cysts can be seen over 4 to 5 years on CT or MRI; epilepsy is the usual clinical manifestation of this condition, which has an estimated mortality rate of 0.5%. On the other hand, NC caused by Cysticercus racemosus is usually seen in skull base cisterns or in the Sylvian fissure. This manifestation seems to be more rare, although some authors report a frequency as high as 45%. Charateristically, these cysts have no scolex; they may persist in the CNS for 15 to 20 years; and intracranial hyper-tension is the most frequent clinical presentation. The management of the chronic inflammation and the complications caused by this meningitis are usually very difficult, and the mortality rate can be up to 33% 3. In 2001, Del Brutto et al. published a consensus about diagnostic criteria of NC 4. They adopted a quite rigid hierarchy of criteria, classified as absolute, major , minor and epidemiologic. In practice, only the absolute criterion is used to include patients in almost all studies of NC reported in the recent literature. By this consensus, the absolute criterion for the diagnosis and considered by them as pathognomonic of NC is the detection of a scolex inside a cyst by CT or MRI. However, C. racemosus doesn't have a scolex. So, patients with this form of the disease do not fulfill the absolute criterion and tend to be excluded, although this is a more severe form of NC. Even in the parenchymatous form of NC, the use of this absolute criterion may be hazardous. About 15% of patients with NC have a unique cysticercus in CNS. During the degeneration …