Neurocysticercosis - Causes, Symptoms, and Treatment

Introduction:

Parasites are organisms that live on other organisms (hosts). Cysticercosis is a parasitic infection caused due to the intake of eggs that belongs to a particular type of tapeworm. Cysticercosis, which involves the central nervous system, is known as neurocysticercosis. Since this disease is caused due to pork tapeworm, it is considered an endemic (disease seen in the people belonging to a particular region) in most of the low and middle-income countries where pigs are grown. However, due to globalization (interaction among people of different cultures and economies which is brought about by cross-border trade in goods, technology, and investments), it is seen even in developed countries. It is thought to be a parasitic infection that is serious among those who are affected but is often neglected by healthcare providers. It is an infection involving the brain and is considered a leading cause of epilepsy in developing countries like Latin America, India, Africa, and China.

What Is Neurocysticercosis?

Neurocysticercosis is a parasitic infection (parasites are organisms that live on other organisms or hosts and invade the organs of the host, making them sick and resulting in parasitic infection) caused due to the accidental intake of the eggs of the pork tapeworm (Taenia solium). The larval cysts (enclosed sac consisting of the immature stage of the parasite) enters the human body and causes infection in various parts leading to a condition known as cysticercosis. When the larval cysts travel through the bloodstream and enter the brain, it leads to a severe form of infection known as neurocysticercosis. It can lead to serious complications like seizures. It is the most common parasitic infection affecting the central nervous system.

What Are the Causes of Neurocysticercosis?

When a person eats infected pork meat, the tapeworm enters the body of the person and causes infection in the intestine. The tapeworm eggs are passed out through the feces of the person. When the person does not wash his/her hands properly after using the toilet, the surfaces and food may get contaminated with feces consisting of tapeworm eggs. When a person consumes the infected food or comes in contact with the infected surface, tapeworm eggs enter the body of the individual. The eggs hatch and form larvae which enter the brain and cause neurocysticercosis. The reasons for the entry of tapeworms into the human body are listed below:

• Consumption of raw or undercooked pork meat

• Intake of contaminated water that has a tapeworm.

• Lack of hygiene.

• Living in the same house with a person having tapeworm infection.

• Eating food cooked by a person with tapeworm infection.

What Are the Symptoms of Neurocysticercosis?

• Seizures (sudden electrical disturbance in the brain, which is uncontrollable). It is the most common symptom of neurocysticercosis.

• Long-lasting headaches repeatedly occur for months.

• Decreased ability to think.

• Confused mental state.

• The patient may feel unable to give attention to people and surroundings.

• Difficulty in maintaining balance while doing daily activities.

• Dizziness.

• Hydrocephalus (fluid gets built up in the cavities inside the brain and causes increased pressure on the brain).

• Decreased response to pain and temperature sensations.

• Paralysis of the muscles which control the movement of the eyes.

• Stroke.

How to Diagnose Neurocysticercosis?

The different methods to diagnose neurocysticercosis are as follows:

Computed Tomography (CT):

• CT findings may differ depending on the stages of parasitic infection. It shows changes in the progress of the disease. During the initial stage of tapeworm infection, the embryo (the early stage of an animal when it is inside the egg) is usually not visible in the CT scan.

• During the early stage of development, the embryo is transformed into a larva (the active form of an organism before developing into an adult). CT initially shows areas of black color without any differentiation from the nearby areas, which later progresses into areas with specific boundaries separated from the nearby structures.

• Vesicular Stage: Within a few weeks, the larva develops into a cyst (a lump that is filled with fluid) containing the front portion of the tapeworm. Within a duration of 3 to 12 months, the cyst grows fully and contains clear fluid. The cysts become visible in the CT, measuring about five to twenty millimeters.

• Colloidal Vesicular Stage: In this stage, the larva gets destroyed and the response by the host (person affected with the infection) takes place. CT taken during this stage shows black rounded structures surrounded by clear or white rings.

• Granular Nodular Stage: This stage involves the formation of a lump or swelling. CT shows mild white areas surrounded by dark black areas completely.

• Nodular Calcified Stage: During this stage, the lump transforms into hard calcium compound deposition. CT scan shows multiple areas of black rounded structures.

Magnetic Resonance Imaging (MRI): This is mainly done to evaluate the cysts present in different parts of the brain during different stages. It gives a clearer picture of the infection than CT scans

Laboratory Tests:

• Cerebrospinal Fluid (CSF) Examination: Cerebrospinal fluid (the fluid which flows in and around the brain and spinal cord) is tested in patients who have developed seizures in recent times.

• In such patients, CT scans and MRIs do not show any major identification features of the infection. CSF diagnosis is not made in patients with a severe infection which may have displaced the brain structures. CSF findings may show the following changes:

• Low or normal levels of glucose.

• Increased level of protein.

• High levels of immunoglobulin G (a substance in the body that fights against infections).

• Stool Examination: Stool samples of 10 to 15 percent of the patients show taeniasis (infection caused by tapeworm).

• Brain Biopsy: The biopsy is a procedure in which a piece of tissue (group of cells) is removed from the body to conduct a test in a laboratory. It is done only in extreme cases.

What Are the Treatment Measures for Neurocysticercosis?

The treatment measures include the elimination of the infection-causing parasite and the management of symptoms.

• After examining the extent of the infection, the doctor may initiate antiparasitic medications (medications used in the management of infections caused by parasites) and anti-inflammatory therapy (medicines used to relieve pain, swelling, and fever).

• Anthelmintic therapy is carried out in patients with symptoms and multiple cysts. The doctor prescribes medicines that are used to let out the parasites from the body. However, this method is not useful in the last stage of infection.

• Drugs to control seizures are given.

• In severe cases with fluid buildup inside the brain, placement of a ventricular shunt and surgical removal of the cyst are done. The ventricular shunt helps in draining the excess fluid which flows in and around the brain and spinal cord when there is an obstruction in the normal outflow of fluid.

• Eradication of neurocysticercosis would be possible only by removing the parasite from both the pig and the human host. Hence, the vaccination of pigs, reforming the animal husbandry techniques, and meat inspection procedures should be followed to stop the disease cycle.

Conclusion:

Neurocysticercosis is the most common parasitic infection affecting the nervous system. It can cause serious complications when left untreated. Hence, anyone with symptoms should immediately visit a doctor, especially after traveling to an area in which infection is present. Community eradication of this disease should be facilitated by following simple steps like washing hands with soap and warm water after using the toilet and before handling food, drinking water that is boiled or bottled, and washing fruits and vegetables with water before consumption. The prevention of neurocysticercosis is very important to reduce the global burden caused by this disease. Hence, global strategies for the prevention of this disease should be employed with the help of international health organizations for the well-being of the people.