Parasite tied to dementia, cognitive impairment

Untreated central nervous system infection with the parasite neurocysticercosis may present as cognitive impairment ranging from mild deficit to full-blown dementia.

Neurocysticercosis is the most common parasitic infection of the CNS. Even physicians — who are familiar with the fact that patients may present with seizures or headache in more advanced stages of infection — may be unaware of infection’s adverse effects on cognition.

Cognitive test findings from 40 patients with neurocysticercosis were compared with those of 49 normal controls from the same regional population, as well as with data on 28 patients with cryptogenic epilepsy experiencing similar rates of seizure frequency and antiepileptic drug use, according to a neurologist at the University of Sao Paulo (Brazil).

That five (12.5 percent) of the treatment-naïve patients diagnosed with neurocysticercosis met DSM IV criteria for dementia, significantly more than the normal control group (P less than .05). Major memory impairment was found in 23 (57. 5 percent).

On a battery of cognitive tests that evaluated memory, attention, praxis, and executive function, all those with neurocysticercosis demonstrated one or more cognitive deficits, a significantly higher rate than observed for the normal controls.

Interestingly, when compared with patients with cryptogenic epilepsy, neurocysticercosis patients continued to score lower on most cognitive tests.

“People having traveled to endemic areas and immigrants from these regions presenting with cognitive decline should be assessed for the presence of neurocysticercosis. Look for lesions on MRI or CT scans.”

“Blood tests and CSF [cerebrospinal fluid] screening are also available to make the diagnosis that sometimes is not straight-forward.”

The classical finding in active disease is a cystic lesion with a scolex (a small point in the center of the lesion), but other lesions can also be related to the disease, and these can be located anywhere in the brain.

Humans become infected with neurocysticercosis through consumption of food or water contaminated with the feces of a Taenia solium tapeworm carrier. The adult tapeworms are found only in the intestines of humans.

Once the tapeworm lays its eggs, the larvae may invade the tissue and through the bloodstream infect skeletal muscles, the eyes, brain, and spinal cord.

A person can be infested by T. solium and be a carrier, but not develop cysticercosis.

Clinicians to keep neurocysticercosis on their radar screens during work-ups and always ask whether a patient, especially one with seizures, has migrated from an endemic area or has traveled to one, or whether they have relatives or people residing with them who originate from an endemic area, such as regions of South American, Central America, or Asia.

In recent years, neurocysticercosis has also become an important public health problem in urban areas of New York, Los Angeles, Texas and Europe.

A patient who has been diagnosed with neurocysticercosis should undergo a cognitive evaluation.