Human sparganosis is caused by the plerocercoid larvae (spargana) of several species of pseudophyllid cestodes belonging to the genera Spirometra [1]. Many cases of human infection are probably due to Spirometra mansoni. China is one of the most endemic counties for sparganosis in Asia. To date, a total of more than 1000 cases of human sparganosis have been reported in 25 provinces of mainland China [2,3].

The life cycle of Spirometra involves 3 hosts. The definitive hosts are carnivores such as cats and dogs. The first intermediate host is a copepod (Cyclops spp.) and the second intermediate hosts are generally frogs and snakes. Humans can act as the second intermediate or paratenic host and become infected with spargana by drinking water contaminated with procercoid-infected copepods, by ingesting undercooked frog or snake infected with spargana, or by local application of frog or snake flesh or skin as poultices to open wounds and other lesions or (especially) to sore eyes; the larvae migrate into the human tissue from the poultice. Spirometra can infect various parts of the human body such as the eyes, buccal and maxillofacial subcutaneous tissues, visceral organs and the central nervous system (CNS). Cerebral sparganosis, which occurs when spargana invade the brain, can result in severe tissue damage and even death. The predominant manifestations are fever, headache and vomiting, as well as neck stiffness and Kernig’s sign. Seizures are common in 16% - 87.8% of patients with cerebral sparganosis. Other symptoms include visual disturbances, motor weakness and sensory disturbance [1-3]. Here we describe the diagnosis of two cases of migrating cerebral sparganosis based on the characteristics of computed tomography (CT) and brain magnetic resonance imaging (MRI), complemented by epidemiological information and serology.

Both patients were diagnosed as having cerebral sparganosis and they were referred to other hospitals in Changsha (the capital city of Hunan province) with better facilities for brain surgery. To date, the parents of both patients are still considering whether to proceed with the physicians’ recommendations of surgical removal of the parasites complemented with anti-epileptic therapy.

Although rare, cerebral sparganosis is far more severe than other forms of sparganosis [2-6]. Praziquantel drug treatment has minimal effect on human sparganosis so surgical removal of the parasite is the treatment of choice. The definitive diagnosis of cerebral sparganosis is usually made by histology after removal of the parasite by surgery [6]. For the two cases described here, pre-surgical diagnosis was, however, made based on the following criteria: 1) Hunan and Jiangxi provinces in China are known to be endemic for Spirometra mansoni [2,3]; a previous case of cerebral sparganosis mansoni was confirmed after surgery in the same village inhabited by case 2. 2) The occurrence of seizures and continuous headaches in both cases. 3) Evidence of eating under/uncooked frogs/snakes or drinking unboiled water. 4) CSF and serum serologically antibody-positive to S. mansoni antigen in ELISA. 5) Tunnel signal, appearing as a string of bead-shape/ring-like lesions or a twisted thread plus adjacent widening of local sulci, in enhanced MRI. Movement of the lesions over time showed that the parasite was still alive after praziquantel treatment. 6) Scattered multiple pinpoint calcifications evident in CT, due to the plerocercoid larva itself or substances (such as calcareous corpuscles) released from the body of the tapeworm [7].

The ring-like lesions in brain MRI or calcification in brain CT can also be found in diseases caused by other parasites such as cerebral schistosomiasis, cerebral paragonimiasis, cerebral echinococcosis, cerebral cysticercosis, cerebral toxoplasmosis, or in other disease syndromes such as cerebral tuberculoma or brain tumor. However, a definitive diagnosis for differentiating sparganosis from the other diseases in the two cases presented here was based on the fact that both were serologically negative for 5 other parasitic diseases but positive for sparganosis and the brain neuroimaging features were consistent with an infection of S. mansoni. Other contributory factors pointing to both cases being due to migrating cerebral sparganosis were as follows:

1) Cerebral schistosomiasis—Although Hunan and Jiangxi provinces are endemic for Asian schistosomiasis [8], the areas where both cases were resident are not endemic. Furthermore, neither subject had travelled to any schistosomiasis-endemic area. The nodular (silt-like) lesion caused by cerebral schistosomiasis can be observed in enhanced MRI instead of in CT [9].

2) Cerebral paragonimiasis—The migratory ring-like enhancing lesions in cerebral paragonimiasis are similar to those found in sparganosis [4,5,10] but those in the former usually vary in size and are larger (sparganosis, less than 5 mm), and their appearance is more grape-like.

The calcifications in cerebral paragonimiasis usually have a soap-bubble appearance and are clustered together [4,10]. No evidence of pulmonary symptoms or signs [10]

also ruled out this infection.

3) Cerebral echinococcosis—Ring-like lesions in cerebral echinococcosis are usually large, unilocular andthin-walled, with no calcification or surrounding oedema. They contain fluid with a similar density to CSF on CT and MRI. MRI may show particulate matter within the cyst due the presence of daughter protoscoleces and hydatid sand. Most patients present with symptoms and signs of raised intracranial pressure including headache, nausea, vomiting and papilloedema [5,11]. Furthermore, echinococcosis is non-endemic to Hunan and Jiangxi provinces [3] and neither subject had travelled to north west China where the disease is common.

4) Cerebral cysticercosis—The images of cerebral cysticercotic lesions vary depending on the morphology of the larvae and the examination technique employed [4,5]. The individual ring-like enhancement of a lesion in MRI of cerebral cysticercosis is a characteristic “hole-withdot”, with the tapeworm scolex visible as a bright nodule within the cyst; round calcifications are larger and more even in size [12].

5) Cerebral toxoplasmosis—The protozoan parasite Toxoplasma gondii is the most common organism affecting the brain in AIDS patients. The lesions are slightly hypointense or isointense relative to the brain parenchyma on TlWI, and hyperintense or isointense on T2WI. Ring lesions commonly demonstrate non-enhancing central areas corresponding to coagulation necrosis. The rings are usually thin, smooth and may be nodular in shape, particularly in small lesions [13].

6) Cerebral tuberculoma—Cheesy narcosis is often revealed in the center of cerebral tuberculoma by MRI. Round, thick-walled, ring-like or nodular lesions can also be observed on MRI [14]. Hypointense lesions can be observed in T2WI and no migrating string of beads is observed in the cerebral parenchyma by imaging.

7) Brain tumor—Brain lesions caused by primary or metastatic tumors in CT/MRI can vary in shape and location but rarely migrate, nor do they appear as a string of beads [15].

MRI is the diagnostic modality of choice in the evaluation of most parasitic infections involving the CNS. It is superior to CT in detecting parasitic lesions, in characterizing the lesions, and in delineating the extent of parenchymal changes. Gadolinium-enhanced MRI is indispensable for both specific diagnosis of the disease and assessment of inflammatory activity, whereas CT is superior in identifying small calcifications [5]. In the two cases presented here, sparganosis was diagnosed based on neuroimaging characteristics but complementary epidemiological information and serology were also helpful.

Compared with other parasitic infections such as malaria [16] and schistosomiasis [8], human sparganosis is relatively rare, and is one of the most neglected parasitic diseases in China where the facilities for correct diagnosis are generally poor. In Hunan province, for example, there is only one medical facility (in Changsha) able to undertake serology for sparganosis. Furthermore, clinicians in general hospitals are not familiar with the CT and MRI features of sparganosis. Meanwhile, health education is needed to improve people’s awareness of preventing infection by not drinking contaminated water and to make sure to cook food thoroughly. Although there have been a number of human sparganosis cases reported in the Chinese literature, epidemiological investigations are few [2]. Further surveillance of S. mansoni in mammalian hosts including cats, dogs and humans, and in reptiles and amphibians should be undertaken in Hunan province and other rural parts of China to determine the true extent of the problem of sparganosis.

Written informed consents were obtained from both patients’ mother as next to kin for publication of these cases reports and any accompanying images.

We thank the patients’ participation and their families’ understanding to publish their information!