Pediatric Neurocysticercosis 

Updated: Mar 03, 2015
Author: Vinod K Dhawan, MD, FACP, FRCPC, FIDSA; Chief Editor: Russell W Steele, MD 

Overview

Background

Neurocysticercosis has been increasingly recognized as a major cause of neurologic disease worldwide and an important problem among immigrant populations in the United States. This recognition is largely due to the widespread availability of sensitive neuroimaging techniques. Neurocysticercosis is the most common parasitic infection of the CNS. Tissue-invading larval forms of the pork tapeworm Taenia solium cause the disease.

Historically, neurocysticercosis was endemic to only Latin America, Asia, and Africa, although it has become increasingly frequent in the United States since the 1980s. Because of this epidemiologic change, all general pediatricians should become familiar with this disease process. The disease has been the subject of several recent reviews.[1, 2, 3, 4, 5, 6]

See the images below.

Case 1: Coronal image MRI of a 6-year-old boy from Case 1: Coronal image MRI of a 6-year-old boy from Peru with single right frontal cyst.
Case 1: Axial image MRI of a 6-year-old boy from P Case 1: Axial image MRI of a 6-year-old boy from Peru with single right frontal cyst.

Pathophysiology

The larvae of T solium (Cysticercus cellulosae) cause neurocysticercosis. This pork tapeworm can vary in size but is notable for a scolex (head) with approximately 25 hooklets, 4 suckers, and a body with 700-1000 proglottids. The ova of the tapeworm are spread via the fecal-oral route and are approximately 40 microns in diameter with a radially striated shell. The intermediate host is the pig, which harbors the larvae after eating ova, and the definitive host is the human being.

If pig products infected with larvae are ingested, a tapeworm infection in the intestines ensues; however, if ova are ingested, neurocysticercosis may occur in this normally intermediate host. The ingested ova develop into larvae (cysticerci) and lodge in soft tissues, especially skin, muscle, and brain. Cysticerci are fluid-filled oval cysts, approximately 1-2 cm in diameter, with an internal scolex.

The eggs are found in human feces because humans are the only definitive hosts. Greatest risk for infection occurs in regions where plants in gardens or farms are fertilized with human feces and humans are exposed to contaminated soil.

In the CNS, T solium is deposited in the cerebral parenchyma, meninges, spinal cord, and eyes. Unless large numbers of cysts are present, the body's immune system does not act to destroy the organism, and cysts can live for many years undetected. A live cyst can go undetected for as long as 5 years before dying or causing symptoms in the host.

Neurologic symptoms arise when the encysted worm dies and the human mounts an associated inflammatory response. If the cyst lodges in the ventricular system (especially the fourth ventricle), hydrocephalus can occur.

Epidemiology

Frequency

United States

Neurocysticercosis is more common among immigrants from endemic areas or children in contact with these immigrants.[7, 8] Several studies report approximately 1000 cases annually in adults and children. One study reported neurocysticercosis as the cause of 2% of the neurologic and neurosurgical admissions in southern California.[9] With increasing immigration from Mexico and other endemic areas, incidence in the southern United States has been increasing. In a recent meta-analysis of the US medical literature, 1494 cases have been reported from 1980-2004.[10]

International

Neurocysticercosis is highly endemic in Latin America, Mexico, Eastern Europe, Asia, Africa, and Spain. The estimated serologic prevalence in Mexican adults is 3.6%, with positive confirmation by autopsy in 1.9%. Approximately 50 million people worldwide are infected. World Health Organization estimates that more than 50,000 individuals die each year from neurocysticercosis.[11]

Mortality/Morbidity

Neurocysticercosis is typically benign, and most lesions spontaneously resolve within 2-3 months; however, mortality is highly dependent on whether the disease process is simple or complicated.

Simple neurocysticercosis occurs in children with only a single exposure to cysts. These children tend to have solitary cysts and fewer complications. Often, children can be treated symptomatically and have a favorable prognosis. This type of neurocysticercosis tends to be observed in the United States and other nonendemic areas.

Complicated neurocysticercosis occurs in children in endemic areas who are repeatedly exposed to ova. Because of complications from increased intracranial pressure and difficulty controlling seizures, these children may have a less favorable prognosis. Complications can arise from uncontrolled seizures, hydrocephalus, papilledema, and occasionally, headaches and emesis, although all of these complications are rare.

Race

Neurocysticercosis tends to be diagnosed more frequently in Hispanics because of the prevalence of the organism in the countries of origin, rather than an innate property of the host child.

Sex

No sexual predilection has been noted.

Age

Reports of cysticercosis are unlikely in children younger than 2 years because of the prolonged incubation period of T solium. Most often, the disease is recognized in children older than 7 years because of this incubation period.

 

Presentation

History

Several recent publications have reviewed the clinical features of neurocysticercosis.[12, 13, 14, 15, 16] The most characteristic feature in children is the acute onset of focal seizures.

Approximately 65-80% of children diagnosed with neurocysticercosis present with seizures, most often focal in nature. Often, these children are brought to medical attention within 2 days of their initial seizure. In many countries where T solium is endemic, cysticercosis is the major cause of epilepsy.

Increased intracranial pressure (due to hydrocephalus, which can occur in 15-25% of cases) causes other common clinical symptoms, including headache, nausea, and vomiting.

Less common presentations include hemiparesis, visual changes, progressive obtundation, sciatica (from cauda equina involvement), and sensory disturbances.

In a 1996 study by Rosenfeld et al of 753 children in Chicago, none presented with fever.[17]

Risk factors include the following:

  • Children who present with neurocysticercosis frequently have emigrated from an endemic area or are children of emigrants from such an area. In the past, many children were exposed to infection through Hispanic food handlers, but this occurrence is less common now.

  • Neurocysticercosis is endemic in certain communities because of poor sanitation, use of sewage for fertilizer, and lack of controlled pens for pigs.

  • If neurocysticercosis is a possible diagnosis in a child without such risk factors, question the family as to household contacts who have traveled to an endemic area. Remember that infection can precede symptoms by as much as 5 years.

Physical

See the list below:

  • Most children with neurocysticercosis have normal findings on physical and neurologic examinations.

  • Some patients may present with hemiparesis due to either a cyst or Todd paralysis after a focal seizure.

  • Rarely, children may present with papilledema, hemiparesis, sensory disturbances, or palpable subdermal cysts.

Causes

See the list below:

  • Larvae (cysticercus) of the tapeworm T solium cause neurocysticercosis. Larvae are acquired by ingestion of T solium ova, found in the feces of humans infected with the pork tapeworm.

  • The disease is most common in the developing world, especially in environments where sanitation is poor. Such environments exist in rural areas of Latin America, Asia, Africa, Spain, and Eastern Europe.

  • Since the 1980s, this disease has been recognized more commonly in the United States, frequently in the states of California and Texas and in the city of Chicago, where Hispanics make up a large proportion of the community. The emergence of CT scanning and MRI studies as diagnostic tools also probably accounts for the increased detection since the 1980s.

 

DDx

 

Workup

Laboratory Studies

Laboratory diagnosis of neurocysticercosis is facilitated by serological and imaging studies.[18, 19]

Enzyme-linked immunotransfer blot assay

If neurocysticercosis is suspected on the basis of clinical and radiographic evidence, an enzyme-linked immunotransfer blot (EITB) assay of a patient's serum may confirm the diagnosis.

Specificity is 100% and sensitivity is 90% for children with more than 2 lesions. Sensitivity is only 50-70% in children with just one lesion (the majority); therefore, the usefulness of this test may be limited.

EITB can be ordered by sending serum to the state public health department laboratory in the area or to the Centers for Disease Control and Prevention (CDC). One private laboratory in the United States (Specialty Laboratories; Los Angeles, California) also performs the test. The CDC Web site provides further information.

HP10 antigen testing

Detection of the metacestode HP10 antigen in serum is a useful tool for diagnosis and follow-up of patients with severe forms of neurocysticercosis treated with cysticidal drugs.[20]

Polymerase chain reaction

More recently, T solium DNA has been observed in the cerebrospinal fluid (CSF) of patients. The polymerase chain reaction amplification of the parasite DNA in the CSF enabled the investigators in correct identification of 29 cases (96.7%).[21]

Stool samples

Examine stools from patients and their contacts for ova and parasites. Obtain 3 consecutive daily stool specimens.

The presence of ova may be the sole diagnostic confirmation in some children, but more importantly, detecting ova in children with neurocysticercosis is worthwhile as a public health measure to prevent further exposure to the tapeworm ova.

Stool test for T solium ova is rarely positive.

Enzyme-linked immunosorbent assay

Enzyme-linked immunosorbent assay (ELISA) can be used on serum and CSF. Detection of antigen in the CSF using a monoclonal antibody-based ELISA has been shown to increase the diagnostic sensitivity.[22]

ELISA can aid in diagnosis in cases with few lesions and relatively mild disease.

Imaging Studies

CT scanning

CT scanning shows the cyst and granuloma stages of neurocysticercosis.[23] These cysts can be solitary or multiple and are usually 5-20 mm in diameter.

Perform CT scanning on all children considered for the diagnosis. Most likely, CT scanning is performed upon presentation of a child with new-onset focal seizures. CT scanning can be performed without contrast.

Approximately 75% of children who are affected with neurocysticercosis have a solitary lesion. Lesions are located most often in the cortex or at the gray-white junction. Approximately one half of lesions have a punctate high density within the ring (scolex). Between 10-20% of children have no abnormality (also observed in MRI studies).

CT scanning is superior to MRI study in detecting calcification, which can be useful in differentiating the punctate cyst of neurocysticercosis in the granuloma wall from other causes of granulomas; however, calcification is observed less frequently in children than in adults. See the images below.

Case 2: MRI of a 40-year-old patient with a single Case 2: MRI of a 40-year-old patient with a single parietal calcified cyst.
Case 2: CT scan of a 40-year-old patient with a si Case 2: CT scan of a 40-year-old patient with a single parietal calcified cyst.

CT scanning can also detect edema around the cyst, which is associated with the death of the organism.

CT scanning can be performed quickly, which is important when caring for young children.

MRI

MRI is the best imaging test overall for the diagnosis. Perform MRI in all patients for whom the clinical history and CT scan findings suggest neurocysticercosis. Use gadolinium contrast.

MRI is useful for lesions of the spinal cord, posterior fossa, brainstem, subarachnoid, and ventricles.

Use of contrast also shows larval death, visible as enhancement of the cyst wall, which indicates that the cyst has changed into a granuloma. In addition, MRI (as well as CT scanning) shows any vasogenic edema around the cyst, indicative of the body's inflammatory response to organism death.

MRI can be used as follow-up imaging to document improvement based on both a decrease in the granuloma diameter and a resolution of vasogenic edema.

A 2000 study of 108 patients by Pradhan et al indicated the prognostic usefulness of gliosis as observed in a T1-weighted magnetization transfer spin-echo MRI. This gliosis was associated with seizure recurrence after at least 2 years of antiepileptic medications were tapered and then discontinued.

See the images below.

MRI of multiple cysts. Image courtesy of the Cente MRI of multiple cysts. Image courtesy of the Centers for Disease Control and Prevention.
Case 3: MRI of a 47-year-old man with 2 right pari Case 3: MRI of a 47-year-old man with 2 right parietal cysts, one with edema.
Case 3: MRI of a 47-year-old man with 2 right pari Case 3: MRI of a 47-year-old man with 2 right parietal cysts, one with edema, after the larger cyst had involuted.

Radiography

Soft tissue radiography can be performed to look for extraneural cysts.[24]

Radiography is rarely helpful. Perform radiography only when all other tests have failed to provide a diagnosis.

For unknown reasons, children in the United States with neurocysticercosis rarely have cysts in subcutaneous or intramuscular tissue.

Skull radiography can be performed, although they are rarely helpful with the advent of the MRI. Occasionally, separation of the cranial sutures can be observed, which indicates increased intracranial pressure.

Other Tests

Electroencephalography

Perform electroencephalography (EEG) in children with recalcitrant seizures.

Occasionally, evidence of periodic lateralized epileptiform discharges (PLEDs) is present.

Procedures

Lumbar puncture

In approximately 50% of cases, a lumbar puncture can reveal pleocytosis (often lymphocytic, but occasionally eosinophilic), decreased glucose, increased protein, and elevated opening pressure. A lumbar puncture can help exclude other infectious or malignant diagnoses.

Serum EITB is more sensitive than the CSF EITB assay, so CSF testing is not usually indicated.

Brain biopsy

Brain biopsy can be performed in cases where the diagnosis remains questionable and the lesion has not resolved. The procedure may be indicated in areas of low prevalence.

 

Treatment

Medical Care

Drug therapy for parenchymal neurocysticercosis with praziquantel or albendazole has been somewhat controversial due to the conflicting results of several small studies. However, more recent randomized controlled trials have documented some benefit of antihelminthic therapy.[25, 26, 27] Patients in the treatment arm showed faster resolution of the active (viable) cysts. Treatment of calcified cysts is, however, not beneficial.[28, 29]

A double-blind randomized controlled trial aimed to establish whether combination of praziquantel and albendazole would increase cysticidal efficacy and whether complete cyst resolution results in fewer seizures. The study concluded that combination of albendazole plus praziquantel increases the parasiticidal effect in patients with multiple brain cysticercosis cysts without increased side-effects. The authors further concluded that a more efficacious parasiticidal regime without increased treatment-associated side-effects should improve the treatment and long term prognosis of patients with neurocysticercosis.[30]

Drug therapy for intraventricular cysts may prove efficacious and is currently recommended by most experts. A meta-analysis of cysticidal drug therapy with albendazole and praziquantel concluded that drug therapy results in better resolution of colloidal and vesicular cysticerci, lower risk for recurrence of seizures in patients with colloidal cysticerci, and a reduction in the rate of generalized seizures in patients with vesicular cysticerci.[31]

In a recent trial, combination therapy with albendazole and praziquantel was statistically comparable with sole therapy with albendazole alone in eradicating lesions and preventing seizures.[32]

Anthelmintic therapy may exacerbate obstruction of CSF flow, precipitating hydrocephalus. Inflammatory response associated with drug therapy may impair vision in ocular disease and may increase the risk of paralysis with spinal cord lesions. Concomitant use of corticosteroids mitigates this inflammatory response. Corticosteroid therapy lowers serum praziquantel levels but variably increases the serum levels of albendazole and its active metabolites in some patients. For this reason, many experts prefer albendazole over praziquentel for treatment of neurocysticercosis.[33]

Surgical Care

Neurosurgery has limited role in the management of neurocysticercosis.[34] Resolution of lesions with medical management alone is superior and should be attempted first. Neurosurgical intervention may be indicated for cases of cysts that have failed to resolve with antihelminthic treatment and are causing severe neurologic sequelae.

In general, indications of surgery include cysts that compress the brain and cranial nerves locally, intracranial hypertension or edema refractory to medical treatment, intraventricular cysts, spinal cysts with cord or root compression, and ocular cysts.

Recently, endoscopic approaches for ventricular cysts have been developed and are now the treatment of choice for ventricular cysts with hydrocephalus.

Shunting may be indicated if cysts have led to hydrocephalus.

Consultations

See the list below:

  • Consult a neurologist for management of seizures, increased intracranial pressure, and any other neurologic sequelae of this disease.

  • Consult an infectious disease specialist for help with a questionable diagnosis, eradication of the organism, and public health issues.

  • Consult an ophthalmologist to examine the child for any signs of subretinal cysts.

  • Consult a neurosurgeon if a biopsy or resection is called for or if the child requires shunting because of hydrocephalus.

Diet

See the list below:

  • Avoid reinfection and reingestion of ova from the original source.

  • No other specific diet is necessary.

Activity

See the list below:

  • No activity restrictions are necessary.

 

Medication

Medication Summary

Anticonvulsants are of universal benefit in stopping seizures and are successful in most cases.

Many children with solitary cysts are found to have calcified or edematous lesions (ie, indicative of cyst death) on imaging studies and have had excellent resolution of their lesions without antihelminthic agents.

Most experts treat children with viable cysts (ie, those that have not calcified or shown signs of edema on imaging studies) and/or multiple cysts. Current options for drug therapy of neurocysticercosis include use of albendazole or praziquantel. No evidence suggests that treatment affects the long-term seizure outcome.

Treating children with severe edema with antihelminthic medications is not recommended because of risk of causing further swelling. Destruction of cysts by antihelminthic agents can cause inflammation that results in neurologic symptoms (eg, headache, vomiting, seizures), which usually occur within 24-48 hours of initiation of therapy. Prophylactic treatment with dexamethasone is beneficial in decreasing the severity of such acute symptoms.

A single dose of praziquantel (5-10 mg/kg) can be administered to individuals found to have T solium tapeworms in their stool.

Antihelminthics

Class Summary

These agents are used in children with viable or multiple cysts. They are used in patients with T solium tapeworms in their stool. Avoid use of antihelminthics in patients with severe edema. Parasite biochemical pathways are different from the human host; thus, toxicity is directed to the parasite, egg, or larvae. The mechanism of action varies within the drug class. Antiparasitic actions may include the following:

1. Inhibition of microtubules causing irreversible block of glucose uptake

2. Tubulin polymerization inhibition

3. Depolarizing neuromuscular blockade

4. Cholinesterase inhibition

5. Increased cell membrane permeability, resulting in intracellular calcium loss

6. Vacuolization of the schistosome tegument

7. Increased cell membrane permeability to chloride ions via chloride channels alteration

Albendazole (Albenza)

Is produced by Glaxo Smith Kline and was made available in the United States in June 1996. Mechanism of action is via its inhibitory effect on tubulin polymerization, which results in the loss of cytoplasmic microtubules. Albendazole is available in 200-mg tabs. To avoid inflammatory response in the CNS, the patient must also be started on anticonvulsants and high-dose glucocorticoids.

Praziquantel (Biltricide)

More expensive than albendazole and probably less effective. Available in 600-mg tabs. Increases cell membrane permeability in susceptible worms, resulting in a loss of intracellular calcium, massive contractions, and paralysis of their musculature. In addition, produces vacuolization and disintegration of schistosome tegument. This is followed by attachment of phagocytes to parasite and death.

Tabs should be swallowed whole with some liquid during meals. Keeping tabs in mouth is not advised because of bitter taste, which can produce nausea or vomiting.

Corticosteroids

Class Summary

These agents are useful in patients with increased intracranial pressure as a result of anthelmintic-induced cyst death and resultant inflammation.

Dexamethasone (Decadron)

Begin therapy in children on the second or third day of antihelminthic therapy if symptoms arise.

Anticonvulsants

Class Summary

These agents are used to control seizures that result from cysts. Most experts taper doses for children after 1-2 years without further seizures. Others suggest that anticonvulsants can be tapered even sooner (6 mo).

Carbamazepine (Tegretol)

Appears to act by reducing polysynaptic responses and blocking posttetanic potentiation.

Phenytoin (Dilantin)

Primary site of action of hydantoins, such as phenytoin, appears to be the motor cortex, where it may inhibit the spread of seizure activity. May reduce the maximal activity of brainstem centers responsible for the tonic phase of grand mal seizures.

 

Follow-up

Further Outpatient Care

See the list below:

  • Children who have single nonviable lesions and do not require antihelminthic treatment can be managed safely on an outpatient basis. Most children can be managed as outpatients, especially in the United States where cases are often simple neurocysticercosis.

  • Arrange neurologic follow-up care to manage seizures and any sequelae.

  • Perform a follow-up MRI in 3-6 months or sooner if symptoms worsen or recur.

  • If a child who was admitted for antihelminthic treatment is doing well after 72 hours and follow-up care is assured, the child can be discharged to finish therapy at home.

Further Inpatient Care

See the list below:

  • Indications for admission in patients with neurocysticercosis include the following:

    • Children who need antihelminthic therapy for active or multiple cysts (hospitalize for first 72 h of therapy)

    • Signs of increased intracranial pressure or apparent need for corticosteroid treatment

    • Recalcitrant seizures

    • Hydrocephalus, possibly requiring an intraventricular shunt

Inpatient & Outpatient Medications

See the list below:

  • Anticonvulsants, with carbamazepine and phenytoin as first-choice treatments

  • Antihelminthics

    • Antihelminthic medication is controversial. Reserve such treatment for certain cases.

    • When antihelminthics are used, albendazole is preferable to praziquantel.

Transfer

See the list below:

  • Arrange transfer if the facility is unable to provide neurologic or neurosurgical care deemed necessary.

Deterrence/Prevention

See the list below:

  • Prevention of exposure to infected ova in the home and community is the most effective preventative measure.

  • Examine stools from contacts using 3 consecutive daily specimens. If positive, contacts should receive single doses of praziquantel (10 mg/kg) or albendazole (400 mg).

Complications

See the list below:

  • Seizures[35]

  • Death

  • Hydrocephalus

  • Recalcitrant seizure disorder[36]

  • Cerebrovascular accidents

  • Motor and speech delay

  • Blindness

  • Dementia

Prognosis

See the list below:

  • In cases with single lesions, prognosis is excellent. In those with multiple lesions, especially extraparenchymal, prognosis can be poor.

  • Treatment with antihelminthics results in complete resolution or significant regression in 80-90% of patients. Most children with calcified single lesions that do not require antihelminthic treatment have spontaneous resolution in 2-9 months, usually within 3 months.

  • Usually, seizures are easy to control, and most children can be weaned from their anticonvulsants within 1-2 years. Most children remain free of seizures.

Patient Education

See the list below:

  • Educate patients and their families regarding prevention.

  • Emphasize improvement in sanitation, separation of pigs from humans, and food preparation hygiene in endemic areas.

  • For excellent patient education resources, please see eMedicineHealth's Infections Center.