Cysticercosis

Background

Pic cyst.png
  • Parasitic infection caused by larval stage of Taenia solium (pork tapeworm)[1]
  • Occurs when humans (definitive host) ingest poorly cooked pig (intermediate host) that is infected with larvae (cysticerci)
  • Estimated 50-100 million people infected worldwide
    • 1,000 new cases in US per year, mostly in immigrants from Latin America but also seen in those from Asia or Africa
  • More than 80% of those affected are asymptomatic
  • Cysts can reside anywhere in body
  • Divided into extraneural cysticercosis (outside CNS) and neurocysticercosis (which can be parenchymal, extraparenchymal or both)

Clinical Features

Extraneural cysticercosis

  • Subcutaneous tissue: nodules that are not cosmetically pleasing, but usually asymptomatic
  • Muscle: asymptomatic or sometimes painful due to surrounding inflammation
  • Cardiac cysts are rare: arrhythmias/conduction abnormalities

Neurocysticercosis (NCC)[2]

  • Parenchymal NCC
    • Most common presentation of NCC
    • Most cases are asymptomatic and discovered incidentally after resolution of infection (see image below)
    • Those with symptoms usually present with seizures (focal or generalized)
    • Focal neurologic deficit
  • Extraparenchymal NCC: more often present with headaches, vomiting, hydrocephalus
    • Intraventricular cysts: can get lodged in ventricular outflow tracts and cause obstructive hydrocephalus and increased ICP causing nausea, vomiting, altered mental status, papilledema
    • Subarachnoid cysts: can cause inflammatory response leading to arachnoiditis which may result in hydrocephalus, meningitis, stroke, and vasculitis
    • Ocular (1-3% of cases): diplopia if EOM involvement, vision loss or pain if intra-ocular
    • Spinal (1% of cases): radicular pain, paresthesias, cauda equina symptoms

Differential Diagnosis

  • Brain abscess
  • Vasculitis
  • Tuberculomas or Mycotic granulomas
  • Primary brain tumors or metastases

Seizure

Evaluation

Workup

  • Imaging is usually best
    • CT head (calcifications/edema); MRI (cysts +/- scolex, edema)[3]
    • X-rays or CT for extraneural cysticercosis
  • EITB assay for anticysticercal antibody
    • Serum (more sensitive) or CSF studies (less common)
  • Labs
    • Usually not helpful
    • Eosinophilia not seen unless cyst is leaking/ruptured
  • Depending on presentation, involvement of the following services may be needed:
    • Neurology: for seizures refractory to meds
    • Neurosurgery: hydrocephalus, mass effect, herniation
    • Infectious disease: if starting antiparasitic therapy
    • Ophthalmology: if suspect ocular involvement or if starting antibiotics and need to confirm no ocular involvement

Evaluation

  • Definitive: 1 absolute criterion, or 2 major plus 1 minor and 1 epidemiologic criteria.
  • Probable: 1 major plus 2 minor criteria, or 1 major plus 1 minor plus 1 epidemiologic criteria, or 3 minor plus 1 epidemiologic criteria.

Absolute

  • Demonstration of parasite from biopsy
  • Cystic lesion with scolex on neuroimaging
  • Direct visualization of parasites on fundoscopic exam

Major

  • Lesions highly suggestive of neurocysticercosis on imaging
  • Positive ELISA for anticysticercal antibodies
  • Resolution of intracranial lesions after antihelminthic therapy
  • Spontaneous resolution of single enhancing lesions

Minor

  • Lesions compatible with neurocysticercosis on imaging
  • Clinical symptoms suggestive of neurocysticercosis
  • Positive ELISA for antibodies in CSF
  • Cysticercosis outside of the nervous system

Epidemiologic

  • Recent travel to endemic area
  • Residence in endemic area
  • Household contact with Taenia solium infection

Management

Asymptomatic

  • Observation

Subcutaneous or intramuscular

  • Typically observation
    • If just one lesion or cosmetic issue, surgical excision
    • Otherwise: NSAIDs

Symptomatic Neurocysticercosis

  • Anticonvulsants (keppra, dilantin, newer agents)
  • Antihelminthic therapy and steroids
    • Treat if edema, mass effect, or vasculitis
    • Don’t treat if old calcifications on CT without edema
    • Before starting these meds, need to check for:
      • positive PPD
      • co-infection with strongyloides (steroids can cause to disseminate)
      • ocular involvement (inflammation associated with dying organisms can result in vision loss by causing chorioretinitis, retinal detachment, or vasculitis)
    • Patients started on therapy get admitted to watch for any adverse events initially

Ocular

  • Intra-ocular: surgery [4]
  • Extra-ocular muscle involvement: albendazole and steroids[5]
  • Spinal intramedullary: possibly surgery

Pregnant

  • Consult OBGYN
  • Avoid any antiparasitics (associated with early worsening in seizure activity). In most cases, therapy should be deferred until after delivery

Antiparasitic Treatment

If hydrocephalus is present, CSF diversion with ventriculostomy or VP shunt by Neurosurgery and/or surgical resection of cysts is recommended rather than antiparastic treatment

Albendazole

  • 15mg/kg/day divided in 2 doses[6]
    • First line therapy

Praziquantel

  • Second line therapy
  • 50-100mg/kg/day divided in 3 doses [7]

Steroids

Disposition

  • Home if asymptomatic or no complications with good pain control
  • Admit if starting antihelminthic therapy for further testing as listed above and to monitor initial side effects of drug therapy
  • ICU for uncontrolled seizures, altered mental status, increased ICP

See Also

References

  1. CDC Cysticercosis http://www.cdc.gov/parasites/cysticercosis/
  2. Wallin MT. et al. Neurocysticercosis in the United States: review of an important emerging infection. Neurology. Nov 9 2004;63(9):1559-64
  3. García HH, Del Brutto OH. Imaging findings in neurocysticercosis. Acta Trop. 2003;87(1):71-8
  4. Sharma T. et al. Intraocular cysticercosis: clinical characteristics and visual outcome after vitreoretinal surgery. Ophthalmology. 2003;110(5):996-1004
  5. Sundaram PM, Jayakumar N, Noronha V. Extraocular muscle cysticercosis - a clinical challenge to the ophthalmologists. Orbit. Dec 2004;23(4):255-62
  6. Garcia HH, Pretell EJ, Gilman RH, et al. A trial of antiparasitic treatment to reduce the rate of seizures due to cerebral cysticercosis. N Engl J Med. 2004;350(3):249-58.
  7. Sotelo J. et al. Albendazole vs praziquantel for therapy for neurocysticercosis. A controlled trial. Arch Neurol. May 1988;45(5):532-4

Authors:

Ross Donaldson