Neurocysticercosis (NCC)

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Neurocysticercosis

Neurocysticercosis (NCC) is the most common cause of infectious epilepsy and a major cause of acquired epilepsy globally.

It is endemic throughout the developing world although incidence has increased in the United States and Europe in the past 30 years due to immigration.

Almost 90% of patients diagnosed with NCC in the United States are immigrants from Mexico or South America.

What are the stages of NCC?

There are four stages of NCC including their appearance on neuroimaging

Vesicular stage

Taenia solium eggs are ingested, cross the intestinal wall, and enter the CNS via the bloodstream where they evolve into larvae (cysticerci) with a transparent membrane, clear vesicular fluid, and an invaginated scolex.

Imaging shows small, rounded cystic lesions that are well demarcated due to lack of edema.

Lesions have no surrounding enhancement because of the parasite’s ability to secrete factors that make it undetectable to the human immune system.

The scolex may be visualized as an interior hyperdense nodule on CT with a “hole-with-dot” appearance.

Colloidal stage

Years after initial infection, the parasite begins to degenerate as it dies, resulting in host immunologic attack.

As the cysticerci begin to involute, the vesicular wall thickens, vesicular fluid becomes turbid, and the scolex begins to undergo hyaline degeneration.

The surrounding tissue develops mononuclear inflammation.

Lesions become more ill-defined on imaging due to development of edema and begin to show rim enhancement on contrast studies.

Granular stage

Once the scolex is completely mineralized and nonviable, it is referred to as the granular stage .

CT at this stage begins to show discrete, hyperdense nodular-enhancing lesions with variable levels of edema. On MRI, both T1- and T2-weighted images show areas of signal void with surrounding hyperintense rims due to gliosis.

Calcified stage

This stage represents full calcification of the cyst with resolution of surrounding edema. In surrounding tissue, epithelioid cells coalesce to form multinucleated giant cells.

CT shows small, hyperdense lesions without edema or enhancement. MRI has poor sensitivity for detection of calcified lesions.

52. What is racemose neurocysticercosis? Lesions located within either the Sylvian fissures or basal cisterns achieve a large size and multilobulated structure referred to as the racemose form .

These may behave as mass lesions that displace other structures and interfere with CSF flow and cause hydrocephalus. They may also result in an arteritis resulting in infarction.

What are the diagnostic criteria for NCC?

Diagnostic CriteriaDegrees of Certainty
Absolute1. Histologic demonstration of parasite in the CNS2. Direct visualization of parasite by fundoscopy3. Evidence of cystic lesions showing scolex on CT or MRIDefinitive1. One absolute criterion2. Two major, one minor, and one epidemiologic criteria
Major1. Imaging with cystic lesions without scolex, enhancing lesions, or typical parenchymal calcifications2. Positive EITB for the detection of anticysticercal antibodies3. Resolution of intracranial cystic lesions after treatment4. Spontaneous resolution of small single enhancing lesionsProbable1. One major and two minor criteria2. One major, one minor, and one epidemiologic criteria3. Three minor and one epidemiologic criteria
Minor1. Imaging with hydrocephalus or abnormal enhancement of the leptomeninges and myelograms showing multiple filling defects2. Clinical manifestations suggestive of neurocysticercosis3. Positive CSF ELISA for anticysticercal antibodies or cysticercal antigens4. Cysticercosis outside the CNS
Epidemiologic1. Evidence of household contact with Taenia solium2. Prior residence in endemic area3. History of frequent travel to endemic area

CNS, Central nervous system; CT, computed tomography; MRI, magnetic resonance imaging; EITB, enzyme-linked immunoelectrotransfer blot; ELISA, enzyme-linked immunoassay.

From Del Brutto OH, Rajshekhar V, White AC Jr, et al.: Proposed diagnostic criteria for neurocysticercosis. Neurology 57(2):177-183, 2001.

How is Neurocysticercosis treated?

Treatment of Neurocysticercosis

Parenchymal Neurocysticercosis
Vesicular Cysts
Single cyst: use albendazole 15 mg/kg/day for 3 days or praziquantel 30 mg/kg in three divided doses every 2 hours. Corticosteroids are rarely needed. Use antiepileptic drugs (AEDs) for seizures.
Mild to moderate infections: use albendazole 15 mg/kg/day for 1 week or praziquantel 50 mg/kg/day for 15 days. Corticosteroids may be used when necessary. Use AEDs for seizures.
Heavy infections: use albendazole 15 mg/kg/day for 1 week (repeated cycles of albendazole may be needed). Corticosteroids are mandatory before, during, and after therapy. Use AEDs for seizures.
Colloidal Cysts
Single cyst: use albendazole 15 mg/kg/day for 3 days or praziquantel 30 mg/kg in three divided doses every 2 hours. Corticosteroids may be used when necessary. Use AEDs for seizures.
Mild to moderate infections: use albendazole 15 mg/kg/day for 1 week. Corticosteroids are usually needed before and during therapy. Use AEDs for seizures.
Cysticercotic encephalitis: cysticidal drugs are contraindicated. Use corticosteroids and osmotic diuretics to reduce brain swelling. Use AEDs for seizures. Perform decompressive craniotomies in refractory cases.
Granular and Calcified Cysticerci
Single or multiple: cysticidal drug therapy is unnecessary. Use AEDs for seizures. Use corticosteroids in patients with recurrent seizures and perilesional edema surrounding calcifications.
Extraparenchymal Neurocysticercosis
Small Cysts over Convexity of Cerebral Hemispheres
Single or multiple: use albendazole 15 mg/kg/day for 1 week. Corticosteroids may be used when necessary. Use AEDs for seizures.
Large Cysts in Sylvian Fissures or Basal CSF Cisterns
Racemose cysticercus: use albendazole 15 mg/kg/day to 30 mg/kg/day for 15-30 days (repeated cycles of albendazole may be needed). Corticosteroids are mandatory before, during, and after therapy.
Other Forms of Extraparenchymal Neurocysticercosis
Hydrocephalus: cysticidal drug therapy is unnecessary. Insert a ventricular shunt. Continual corticosteroid administration (50 mg three times a week for up to 2 years) may be needed to reduce the rate of shunt dysfunction.
Ventricular cysts: perform endoscopic resection of cysts. Albendazole may be used only in small lesions located in lateral ventricles. Ventricular shunt only needed in patients with associated ependymitis.
Angiitis, chronic arachnoiditis: cysticidal drug therapy is unnecessary. Corticosteroids are mandatory.
Cysticercosis of the spine: perform surgical resection of lesions. Anecdotal use of albendazole with good results has been reported.

From Del Brutto OH: Neurocysticercosis. Continuum (Minneapolis, Minn.) 18(6 Infectious Disease):1392-1416, 2012.

In addition to seizures, what are the other important clinical manifestations and complications of NCC? 

Patients may develop headache, cognitive impairment, compressive myelopathy as well as lacunar infarcts as a result of occlusion of small vessels by surrounding inflammation or large vessel infarcts or focal neurologic signs due to local mass effects.

Cysticercotic arachnoiditis may lead to entrapment and dysfunction of cranial nerves.

Hydrocephalus may result from impaired CSF resorption or occlusion of the foramina of Luschka, Magendie, or Monro.

Sources

Aksamit AJ: Progressive multifocal leukoencephalopathy. Continuum 18(6):1374-1391, 2012.

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