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

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