AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Cysticercosis is a systemic illness caused by dissemination of the larval form of the pork tapeworm, Taenia solium. Encystment of larvae can occur in almost any tissue. Involvement of the central nervous system (CNS), known as neurocysticercosis (NCC), is the most clinically important manifestation of the disease and may present with dramatic findings. Incidence of cysticercosis is increasing within developed countries.

Pathophysiology

Humans are the definitive T solium hosts and can carry an intestinal adult tapeworm (taeniasis), often without symptoms. Intermittent fecal shedding of egg-containing proglottids or free T solium eggs ensues, with the intention that the intermediate host (normally pigs) will ingest the excreted eggs in contaminated food or water. T solium embryos penetrate the GI mucosa of the pig and are hematogenously disseminated to peripheral tissues with resultant formation of larval cysts (cysticerci). When undercooked pork is consumed, an intestinal tapeworm will again be formed, completing the life cycle of the worm.

Human cysticercosis occurs when T solium eggs are ingested via fecal-oral transmission from a tapeworm host. The human then becomes an accidental intermediate host, with development of cysticerci within organs. Cysticerci may be found in almost any tissue. The most frequently reported locations are skin, skeletal muscle, heart, eye, and most importantly, the CNS (NCC).

Symptomatology of NCC is largely dependent on the presence of pericystic inflammation, the absence of which will usually manifest as asymptomatic disease. Host inflammatory response to cysticerci depends on the parasite's ability to evade host immunity; therefore, inflammation is restricted to currently degenerating cysts whose ability to evade host defenses is faltering. Lack of inflammation occurs with both healthy cysticerci and those that have involuted, termed active and inactive disease, respectively. Upon involution, cysts undergo granulomatous change and exhibit calcification. Cysts in various stages of viability can be seen simultaneously in one host.

In patients with advanced HIV disease and compromised cell-mediated immunity, NCC may is exist without significant host response and is likely to be asymptomatic. For this reason, in symptomatic patients with CD4 counts under 200 cells/mm³ alternative diagnoses should be considered more likely.

Clinical manifestations of NCC depend primarily on the number and location of CNS cysticerci and the host's immune response to infection. Serious pathologic findings of NCC can include seizures, obstructive hydrocephalus, meningoencephalitis, and vascular accidents.

Involvement of brain parenchyma is common and leads to the most frequent presentation of seizure or headache. Extraparenchymal ventricular and subarachnoid cysts also are found. These carry a worse prognosis and often lead to obstructing hydrocephalus requiring surgical intervention. Cysticerci within the basilar cisterns or Sylvian fissures may become quite large. Those within the cisterns may also cause serious vasculitis and stroke. Spinal NCC is rare.

Ocular cysts are mostly vitreous, but they may be found in subretinal locations. Visualization of cysts via funduscopy may be diagnostic of the disease. Subcutaneous nodules represent cysticerci in the skin. Skeletal muscle encystment usually is asymptomatic but may cause muscular pseudohypertrophy with a heavy parasite burden. Cardiac cysts may lead to conduction system abnormalities.

Frequency

United States

Incidence in the United States is increasing secondary to increased immigration from endemic areas, increased travel to endemic areas, and improved serologic testing and availability of diagnostic imaging. An estimated 1000 new cases are diagnosed per year in the United States. In southern California, with its large population of immigrants, NCC may account for at least 10% of seizures seen in some emergency departments and more than 2% of neurological or neurosurgical admissions. The diagnosis of NCC should be considered in any patient from an endemic area presenting with new-onset seizures.

International

Cysticercosis affects an estimated 50 million people worldwide. Endemic areas include Mexico and Latin America, sub-Saharan Africa, India, and East Asia. NCC is a leading cause of adult-onset seizures worldwide.

Mortality/Morbidity

Morbidity may result from seizures, strokes, or hydrocephalus and from difficult long-term treatment with anticonvulsants, steroids, or cerebrospinal fluid shunts.

Mortality from cysticercosis is minimal and generally limited to cases complicated by encephalitis, increased intracranial pressure (ICP) secondary to edema, and/or hydrocephalus and strokes.

Race

Hispanic and Asian populations are more commonly affected secondary to immigration patterns from endemic areas. The disease is prevalent in South Asia as well, where patients more commonly present with a single cyst.

Age

People of any age may be affected. Children may be more likely to develop an unusual encephalitis-type variant.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• NCC is frequently asymptomatic. Symptoms are generally similar to those found with other intracranial mass lesions, which may be consistent with elevation of ICP. Cysticercosis of other tissues is almost always asymptomatic. The following symptoms may occur years after infection begins:
• • Seizures (focal or generalized)
  • Chronic headache
  • Nausea and vomiting
  • Vision changes
  • Focal neurological complaints
  • Mental status changes

Physical

• Physical findings include the following:
• • Absence of fever
  • Usually nonfocal neurologic examination findings
  • Papilledema and decreased retinal venous pulsations
  • Meningismus
  • Hyperreflexia
  • Nystagmus or visual deficits
  • Visualization of intraocular larvae by funduscopy may be diagnostic
  • Subcutaneous nodules resembling sebaceous cysts
  • Muscular pseudohypertrophy

Causes

• Risk factors associated with the disease include the following:
• • Immigration from an endemic area (especially Mexico, Latin America)
  • Family history of parasitic infestation
  • History of travel to an endemic area
  • Household visitors from an endemic area

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Sarcoidosis

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Laboratory studies are inferior to imaging in diagnosis of cysticercosis but may play an adjunctive role.
• Complete blood count (CBC): Peripheral eosinophilia usually is not present, but eosinophils may be 10-15% of white blood cells (WBCs).
• Serology is the most useful of lab tests.
• • Sensitivity of serology is directly linked to number of parasitic lesions and the stage of lesions. Single lesions and calcification are more likely to be associated with a false-negative assay result. False-positive results may be caused by other parasitic infections.
  • Enzyme-linked immunosorbent assays (ELISAs) have reported 74% sensitivity and are highly specific for the appropriate antigens. Sensitivity may be increased in cases involving multiple cysts or if the assay is performed on cerebral spinal fluid (CSF) rather than serum.
  • The newer enzyme-linked immunoelectrotransfer blot (EITB) is preferred to ELISA. It carries a better than 95% sensitivity and nearly 100% specificity in patients carrying multiple cysts. However, its performance is poor in those with a single cyst or with only calcific lesions.
• Stool for ova and parasites
• • Many patients have simultaneous intestinal tapeworm infestation.
  • This test is insensitive, and many samples may be needed over several days.
  • The test is nonspecific for T solium species, as the eggs appear similar to those of the beef tapeworm.

Imaging Studies

• Soft tissue x-ray may show calcifications of inactive cysts. These may appear as oblong-shaped "cigar" lesions.
• Brain CT scan
• • CT scan is recommended as the first imaging study.
  • CT scan is more widely available, less expensive, and has a faster imaging time than MRI.
  • Obtain contrast and noncontrast studies.
  • Noncontrast study may show focal areas of edema in the acute phase of disease, cystic lesions, or calcifications of inactive disease, which is the most common disease form at presentation. Findings may indicate mass effect or hydrocephalus. Ventricular cysts may be isodense with CSF and manifest only as distortion of surrounding tissue. Percutaneous CSF contrast administration may be helpful to delineate these lesions. CT scan is also insensitive for lesions near bone or within the posterior fossa.
  • Intravenous contrast study may depict nonenhancing cystic lesions with or without edema or ring enhancement signifying inflammation surrounding an involuting living cysticercus.
• MRI of brain
• • MRI is recommended as an adjunctive diagnostic tool to CT scan. It may aid in cases where previous CT scan was nondiagnostic.
  • MRI may show a mural nodule within the cyst representing the larval scolex. This finding is pathognomonic for cysticercosis.
  • MRI may show cysticerci within the ventricular system, which are often missed by CT scan due to the similar appearance of cerebrospinal and cystic fluids.
• MRI is the preferred imaging modality to identify brainstem cysts or those over the cerebral convexities.

Other Tests

• Several authors have proposed tiered diagnostic criteria based on expert consensus. These utilize clinical, radiologic, histologic, and serologic features as well as epidemiologic factors and response to therapy to formulate diagnostic certainty. Detailed explanation of these scoring systems can be found in other references.

Procedures

• Lumbar puncture
• • It may be necessary to obtain an imaging study prior to lumbar puncture to exclude intracranial mass effect.
  • This test is not sensitive or specific for the diagnosis of cysticercosis.
  • CSF is normal in many cases. In the presence of significant inflammation, CSF may show lymphocytosis, increased protein, and/or decreased glucose levels. The finding of pleocytosis is more common in cases of subarachnoid NCC.
• Special Wright or Giemsa stains are needed to show CSF eosinophilia, a common but nonspecific finding.
• Biopsy of subcutaneous nodule: Demonstration of organisms within nodular tissue is diagnostic of cysticercosis.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Prehospital Care

Patients present with seizure activity, altered mental status, headache, or other neurologic complaints. Prehospital treatment involves standard supportive care including ensuring that adequate oxygenation, ventilation, and perfusion are maintained. Airway protection may be mandated. Administration of anticonvulsants may be necessary for prolonged or repeated seizure activity. Empiric naloxone may be given for coma. Hypoglycemia should be corrected.

Emergency Department Care

• Administer supportive care for those presenting with seizure activity.
• Administer oxygen, monitor, and properly correct metabolic abnormalities.
• Anticonvulsants are reliably effective in controlling seizures secondary to cysticercosis. Most patients will respond to first-line agents.
• Steroids, osmotic agents, and/or diuretics are indicated with evidence of increased ICP.
• Analgesics may be administered for pain control.
• Initiate proper diagnostic procedures, including blood work and imaging.
• Consult appropriate specialists.

Consultations

• Consultations may include neurosurgery, neurology, infectious diseases, and ophthalmology. Neurosurgical procedures are frequently required to relieve intracranial pressure. Biopsy or surgical removal of lesions may be necessary.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Antihelminthic agents are the mainstay of definitive treatment. Controversy exists as to whether antiparasitic treatment of cysticercosis is necessary in most cases. Some authors claim that patients do well without antiparasitic therapy since symptomatology is produced by pericystic inflammation, which is indicative of imminent involution of the parasite. A recent randomized controlled trial demonstrated benefit of antihelminthic therapy in patients harboring a limited number of viable cysts within brain parenchyma. After an initial expected increase in seizure activity, patients treated with albendazole and steroids had significantly better long-term control of generalized seizures than those receiving placebos.

Use caution in those with significant pretreatment encephalitis, hydrocephalus, or vasculitis. Treatment may cause increasing inflammation as cysts involute, leading to worsening clinical states. Concomitant administration of corticosteroids is often recommended to avert inflammatory response. CSF shunting may be indicated before medical treatment begins since intracranial hypertension may worsen upon administration of antiparasitics.

Drug Category: Anthelmintics

Parasite biochemical pathways are sufficiently different from the human host to allow selective interference by chemotherapeutic agents in relatively small doses.

The more effective agent, albendazole, has upstaged praziquantel as the traditional therapeutic agent.

Drug Name	Albendazole (Albenza)
Description	Broad-spectrum anthelmintic that decreases ATP production by the worm causing energy depletion, immobilization, and finally, death.
Adult Dose	15 mg/kg/d PO divided bid/tid for 2 wk
Pediatric Dose	10 mg/kg PO qid
Contraindications	Documented hypersensitivity; ocular cysticercosis
Interactions	Coadministration with carbamazepine may decrease efficacy; dexamethasone, cimetidine, and praziquantel may increase toxicity
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Discontinue use if LFTs increase significantly (resume when levels decrease to pretest values)

Drug Category: Corticosteroids

A temporary increase in pericystic inflammation often is observed during treatment of NCC, as the dying parasite no longer can escape host defenses. For this reason, it is often recommended that corticosteroids be administered in combination with, or instead of, antihelminthics. This practice is controversial and should be tailored to the individual patient according to the number and location of cysticerci. Steroids are more likely indicated in cases involving extraparenchymal cysts.

Drug Name	Dexamethasone (Decadron, Dexone)
Description	For various allergic and inflammatory diseases. Decreases inflammation by suppressing migration of polymorphonuclear leukocytes and reducing capillary permeability.
Adult Dose	4-6 mg IV q4-6h
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; active bacterial or fungal infection
Interactions	Effects decrease with coadministration of barbiturates, phenytoin and rifampin; dexamethasone decreases effect of salicylates and vaccines used for immunization
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Increases risk of multiple complications, including severe infections; monitor adrenal insufficiency when tapering drug; abrupt discontinuation of glucocorticoids may cause adrenal crisis; hyperglycemia, edema, osteonecrosis, myopathy, peptic ulcer disease, hypokalemia, osteoporosis, euphoria, psychosis, myasthenia gravis, growth suppression, and infections are possible complications of glucocorticoid use

Drug Category: Anticonvulsants

Anticonvulsant therapy should proceed as in other epileptiform states. Benzodiazepines are first-line agents for active prolonged or repeated seizures. They should generally be followed by a more definitive anticonvulsant such as phenytoin. Barbiturates may be needed in more refractory cases.

Drug Name	Phenytoin (Dilantin)
Description	May act in motor cortex, where it may inhibit spread of seizure activity. Activity of brain stem centers responsible for tonic phase of grand mal seizures may also be inhibited. Dose to be administered should be individualized. Administer larger dose before retiring if dose cannot be divided equally.
Adult Dose	18 mg/kg IV loading dose followed by 100-150 mg/dose at 30-min intervals; not to exceed 1500 mg/24h
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; sinoatrial block, second- and third-degree AV block, sinus bradycardia, or Adams-Stokes syndrome
Interactions	Amiodarone, benzodiazepines, chloramphenicol, cimetidine, fluconazole, isoniazid, metronidazole, miconazole, phenylbutazone, succinimides, sulfonamides, omeprazole, phenacemide, disulfiram, ethanol (acute ingestion), trimethoprim, and valproic acid may increase phenytoin toxicity; phenytoin effects may decrease when taken concurrently with barbiturates, diazoxide, ethanol (chronic ingestion), rifampin, antacids, charcoal, carbamazepine, theophylline, and sucralfate; phenytoin may decrease effects of acetaminophen, corticosteroids, dicumarol, disopyramide, doxycycline, estrogens, haloperidol, amiodarone, carbamazepine, cardiac glycosides, quinidine, theophylline, methadone, metyrapone, mexiletine, oral contraceptives, valproic acid
Pregnancy	D - Unsafe in pregnancy
Precautions	Perform blood counts and urinalyses when therapy is begun and at monthly intervals for several months thereafter to monitor for blood dyscrasias; discontinue use if a skin rash appears and do not resume use if rash is exfoliative, bullous, or purpuric; rapid IV infusion may result in death from cardiac arrest, marked by QRS widening; caution in acute intermittent porphyria and diabetes (may elevate blood sugars; discontinue use if hepatic dysfunction occurs

Drug Name	Phenobarbital (Solfoton, Luminal, Barbita)
Description	Elevates seizure threshold, limits the spread of seizure activity, sedative.
Adult Dose	10-30 mg/kg IV loading dose followed by 5 mg/kg/dose q15-30min; not to exceed 40 mg/kg
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; severe respiratory disease, marked impairment of liver function, nephritic patients
Interactions	May decrease effects of chloramphenicol, digitoxin, corticosteroids, carbamazepine, theophylline, verapamil, metronidazole, and anticoagulants (patients stabilized on anticoagulants may require dosage adjustments if added to or withdrawn from their regimen); coadministration with alcohol may produce additive CNS effects and death; chloramphenicol, valproic acid, and MAOIs may increase phenobarbital toxicity; rifampin may decrease phenobarbital effects; induction of microsomal enzymes may result in decreased effects of oral contraceptives in women (must use additional contraceptive methods to prevent unwanted pregnancy; menstrual irregularities may also occur)
Pregnancy	D - Unsafe in pregnancy
Precautions	In prolonged therapy, evaluate hematopoietic, renal, hepatic, and other organ systems; caution in fever, hyperthyroidism, diabetes mellitus, and severe anemia since adverse reactions can occur; caution in myasthenia gravis and myxedema

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• Inpatient treatment is recommended for those receiving antiparasitic therapy since transient worsening of condition may ensue.
• Neurosurgical intervention often is required in cases of obstructive hydrocephalus, ventricular cysticerci, and in cases refractory to medical treatment.
• Ophthalmologic surgery is recommended in all cases of ocular cysticercosis since the inflammatory reaction associated with medical therapy may threaten vision.
• Only standard isolation is required for patients who are hospitalized.

Further Outpatient Care

• Prescribe a follow-up CT scan or MRI to assess response to treatment.
• Long-term anticonvulsant therapy is usually necessary in patients with persistent CNS calcifications. Selected patients who demonstrate radiographic cure and display no seizures over prolonged periods may discontinue anticonvulsant medication.

Transfer

• Transfer to a facility with neurosurgical capability is indicated in cases of extraparenchymal disease and in those involving increased ICP, hydrocephalus, mass effect, or herniation.
• Status epilepticus may require neurological intensive care.

Deterrence/Prevention

• Screen family members for parasitic disease. Prophylaxis may be indicated.
• Educate patients regarding personal hygiene and handling of food.
• Those traveling to endemic areas should be educated in preventative habits such as proper cooking of meat and avoidance of fecal-oral transmission routes.

Complications

• Intracranial herniation
• Stroke
• Status epilepticus
• Long-term anticonvulsant use
• Intraventricular shunt complications

Prognosis

• Prognosis is excellent in almost all cases.

Patient Education

• Patients and their families should be familiar with basic first aid for seizures.
• Education should be provided on use of prescribed medications and the expected course of disease.
• Provide instruction on indications to seek medical care, including signs of increasing ICP or focal neurologic complaints.
• Patients prone to seizures should not drive or perform other dangerous activities.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to note signs of increased ICP.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

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• Salinas R, Counsell C, Prasad K. Treating neurocysticercosis medically: a systematic review of randomized, controlled trials. Trop Med Int Health. Nov 1999;4(11):713-8. [Medline].
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Article Last Updated: Jul 13, 2006