Epidemiology on cerebral sparganosis in children
Usually human being is not infested by an adult spirometra mansoni. However when the adult spirometra mansoni infests human gastrointestinal tract, the mechanical and chemical stimulation from the worm can cause discomfort in middle and upper abdomen, dull pain, nausea and vomiting. Sparganum, the larval form of spirometra mansoni, can lead to the sparganosis in human being, and the harm well exceeds that caused by the adult worm. Degree of severity depends on its migration and infected area. Infected areas of the most commonly seen are eyes, subcutaneous tissue of the limbs, oral cavity, face and internal organs. Eosinophilic granulomas can be formed in these areas causing local swell and abscess. If a sparganum infects a brain, then the disease is known as cerebral sparganosis. For human being, there are two pathways of the infection: either by entering through skin of spargana and procercoids or by entering through the mucosa from ingestion of spargana and procercoids.
According to our data and literature
] there are three most common sources for the infection of the ingestion. The first is for patients to utilize frog meat as poultices to heal wounds or abscesses in the eyes, cheeks and genitals. If the frog meat contains spargana, they can enter through the wound or normal skin or mucosa into the patients’ bodies. Some patients ingested either living tadpoles to heal sores and pain or uncooked and or improperly cooked frog, crabs, snake, chicken and or pig meat. The ingested sparganum passed through the intestinal wall, entered the peritoneum and moved to other places including a brain. The third is for patients infected by untreated water. This provided an opportunity for cyclops to enter the patient bodies. Among our cases, six had experienced high risk factors, such as a history of eating uncooked frog meat or ingesting uncooked crabs or drinking contaminated water.
] and our study explored that incidence of a cerebral sparganosis in children and young age adults was higher than the one in middle and old age adult. The possible reasons are the followings: the children and young people usually had more chances to get skin injury and ate infected cyclops water; because the immune system of children and young people was not intact, the sparganum and procercoid invading into their bodies could be survived easier; the blood brain barrier of children and young people was immature, so the sparganum and procercoid invading their bodies were more accessible to their brains.
The clinical presentation of the patients was similar to the one of the patients with brain tumors. In our cases, nine patients presented with headache, eight with convulsions, five weakness in the limbs, two with dizziness, one with projectile vomiting, two with blurred vision, one with intermittent mouth twitching, two with the limb numbness, and one with paralysis. One also had liver sparganosis and presented with headache and right hypochondriac pain.
MR imaging presentations
Recent publications illustrated importance of imaging modalities in diagnosis of this rare disease
]. Both Song
] and Moon
] reported cerebral sparganosis with the following imaging characteristics: low density on CT images; slight hypointense in T1W images and hyperintense in T2W images; a ring or a beaded enhancement on enhanced MR images with a similar shape as sparganum; and without the signal from small punctuate calcification while with the signal from small signal voids in T1W images. Chen
] reported low and high density lesions on CT images and high density for calcification on CT images and a ring or a beaded or a tortuous enhancement representing the shapes of the parasite on enhanced CT or MR images.
In our cases, MR presentations of cerebral sparganosis in children included solitary or multiple asymmetrical lesions, but a single lesion is a main presentation. Lesions mainly occur in the frontal or parietal lobe, with fewer lesions in temporal, occipital, basal ganglia, cerebellum and brainstem. Lesions mostly affect white matter, with fewer lesions in gray-white matter junction and gray matter. The shapes of lesions include irregular patchy, serpiginous tubular and tortuous linear pathways. Irregular large patchy areas of edema can be appreciated in the cerebral parenchyma surrounding the lesions. They are slight hypointense on T1WI but moderately hyperintense on T2WI with irregular large patchy areas of edema signal. In enhancement images, most lesions show a ring, a beaded, and a serpiginous tubular enhancements. Nodular, tortuous linear and comma-shaped enhancements can also be appreciated in few cases. The MR presentations in our study are similar to those in previous studies
]. However serpiginous tubular and comma-shaped enhancements of lesions have not been previously reported. The major possible reasons for existing different shapes on the lesion images are the followings: a ring, a serpiginous tubular, a tortuous linear, and a comma shaped enhancements are caused by different configuration of worm bodies; tortuous linear and comma shaped enhancements are due to compacting twist of the worm bodies; serpiginous tubular enhancement is due to losing twist of a worm body; and beaded enhancement is formed by eosinophilic granuloma yielded by worm stimulating brain tissue and tunnel produced by the worm body. The followings are a summary of the MR presentations on cerebral sparganosis in children from this study. First, there were a serpiginous tubular, a beaded and a tortuous linear enhancements of the lesions in the images. Second, a ring-enhanced lesion was relatively small with a diameter less than 2
cm, which may be due to sparganum stimulating brain tissue leading to eosinophilic granuloma shown in images. Third, there were changes in the location and shape of the lesions on follow-up enhanced images, suggesting that a migration happened and that the sparganum was alive
A sparganum cannot reproduce in brain tissue and develop into an adult. However, it can survive for a long time and has a good mobility. This causes local inflammation and forming single or multiple eosinophilic granulomas. Often, there is a cavity formed in the granuloma, this may contain one or two sparganums. During dying, the sparganum releases toxins stimulating brain tissues, and generates edemas. The last, in follow-up images, no obvious increase in size was noted in these lesions, but there was an increase in number of enhancement areas. This may be due to movement of a sparganum to other places producing new granulomas.
If the above characteristics exist in the MR images, then the disease: cerebral sparganosis should be considered. We need to use the method of ELISA
] to further test cerebrospinal fluid and blood serum for sparganum antibodies (i.e., with positive results) for a final diagnosis. Hence, the above-summarized information obtained from the baseline MR scans and follow-up scans are important for diagnosing cerebral sparganosis in children.
Finally, we need to address two other diseases with similar presentations as the ones of cerebral sparganosis in children. The first is parasitic granulomatous cerebrates, such as paragonimiasis, toxoplasmic encephalitis. The MR images of parasitic granulomatous cerebrates also show: hypointense in T1WI but hyperintense in T2WI with perilesional irregular large patchy areas of edema; a ring and or a nodular enhancements; either single or multiple lesion(s) with mass effect; in addition, migratory of the lesions in some cases. Hence, cerebral sparganosis in children can be easily confused with paragonimiasis, toxoplasmic encephalitis and other parasitic granulomatous cerebrates if diagnosis is only made through MRI. However, cerebral sparganosis of MR images also demonstrates specific charateristics: a serpiginous tubular, or a beaded, or a tortuous linear enhancement. A final diagnosis for cerebral sparganosis should be made in combination with using parasite specific immunological assays, such as ELISA, to test related antibodies
]. The second is gliomas or metastatic tumors. In our series, four of these 18 patients were misdiagnosed as a gliomas or a metastatic tumor. The differences in diagnosis of cerebral sparganosis and a brain tumor should be the followings: a cerebral sparganosis can appear as a serpiginous tubular, or a beaded, or a tortuous linear enhancements while the images of brain tumors do not possess such enhancement patterns; changes in location and shape of the enhancements in follow-up MRI are only noted for cerebral sparganosis; a size of ring enhancement for cerebral sparganosis is relatively small (less than 2
cm diameters), and it is almost a constant in the follow-up images while the size of a brain tumor usually is relatively large, and becomes bigger in the follow-up images; and magnetic resonance spectroscopy (MRS) can also be applied to differentiate a cerebral sparganosis from a brain tumor patient
]. The main treatment of cerebral sparganosis in children is a surgical resection. For the surgery, care should be taken to totally remove the worm for avoiding recurrence. Recently the authors in
] concluded that priority should be given to image-guided stereotactic aspiration since it causes the smallest wounds. Praziquantel and albendazole used for deworming are not very effective for the disease. Prevention should rely on education. Children and parents should not use frog meat as poultices and avoid ingestion from eating uncooked meat and drinking untreated water.