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

Diagnosis

Divided into extraneural cysticercosis (outside CNS) and neurocysticercosis (which can be parenchymal, extraparenchymal or both)

  • 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, AMS, 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

Proposed Diagnostic Criteria for Cysticercosis

  1. 1 Definitive diagnosis requires 1 absolute criterion, or 2 major plus 1 minor and 1 epidemiologic criteria.
  2. 2 Probable diagnosis requires 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

Differential Diagnosis

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

Seizure

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

Management

  • Asymptomatic: observation
  • Subcutaneous or intramuscular: typically observation
    • If just one lesion or cosmetic issue, surgical excision
    • Otherwise: NSAIDs

Symptomatic NCC

  • 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 w/ 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)
    • Pts started on therapy get admitted to watch for any adverse events initially

Antiparasite Medications

  • Albendazole
  • 15mg/kg/day divided in 2 doses[4]
    • First line therapy
  • Praziquantel
    • Second line therapy
    • 50-100mg/kg/day divided in 3 doses [5]
      • Steroids: Prednisone 1mg/kg/day or Dexamethasone 0.1mg/kg/day
    • If hydrocephalus present, CSF diversion with ventriculostomy or VP shunt by Neurosurgery and/or surgical resection of cysts.

Ocular

  • Intra-ocular: surgery [6]
  • Extra-ocular muscle involvement: albendazole and steroids[7]
  • Spinal intramedullary: possibly surgery

Disposition

  • Home if asymptomatic or no complications w/ 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, AMS, increased ICP

See Also

Sources

  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. 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.
  5. Sotelo J. et al. Albendazole vs praziquantel for therapy for neurocysticercosis. A controlled trial. Arch Neurol. May 1988;45(5):532-4
  6. Sharma T. et al. Intraocular cysticercosis: clinical characteristics and visual outcome after vitreoretinal surgery. Ophthalmology. 2003;110(5):996-1004
  7. Sundaram PM, Jayakumar N, Noronha V. Extraocular muscle cysticercosis - a clinical challenge to the ophthalmologists. Orbit. Dec 2004;23(4):255-62