Neurocysticercosis: Causes, Symptoms, Treatment, Complications, Pathophysiology
Cysticercosis is the common parasitic infection caused by tapeworm Taenia solium (T.solium). When it infects the brain and the spinal cord it is called Neurocysticercosis. The common symptom of Neurocysticercosis is seizure or epilepsy. Initially it was prevalent only in developing countries. However, today due to worldwide migration, Neurocysticercosis is found in most of the developed countries as well including United States (US).
Neurocysticercosis: An Overview
Taenia solium, a tapeworm, is commonly found in the muscles of pig. When the uncooked pork is ingested by human, the eggs of this tapeworm enter the body. During the process of digestion, these are converted into larvae. Once into the gastrointestinal system, they can pass this boundary and reach the muscles, eyes and cause a condition called cysticercosis. When cysts infect brain they give rise to a clinical condition called Neurocysticercosis, which is a characterized by frequent seizures. It is fatal since it causes significant illness and accounts for 10% of emergency hospital visits for seizures.
Neurocysticercosis is a neglected parasitic disease and is poorly understood. It is also called as hidden epidemic. It is important to be aware of Neurocysticercosis since it is a leading cause of adult onset of epilepsy and its worldwide incidence is increasing.
Symptoms of Neurocysticercosis
The main symptom of Neurocysticercosis observed in 70% cases is Epilepsy. The other symptoms include:
- Headache and dizziness
- The active form the parasite causes arachnoiditis and cerebral stroke
- Inactive form leads to parenchymatous calcifications.
Epidemiology of Neurocysticercosis
Neurocysticercosis is common in poor places which lack good public health systems. Higher number of cases has been reported from developing countries such as Latin America, India, China and Africa. This parasitic infection of brain is on rise globally including the developed countries such as United States, United Kingdom and Canada. This is due to the large number of immigrants coming from endemic parts. World Health Organization (WHO) has estimated globally >2.5 million people are infected with T.solium and there is an occurrence of 50 thousand deaths annually due to neurocysticercosis.
Prognosis of Neurocysticercosis
The mild cases of neurocysticercosis are treatable. The first line of medication is the Anti-Epileptic drugs. The cysts are treated with anticysticercal drugs. Duration of treatment is variable and depends on the case.
The prognosis is poor in case of racemose type of neurocysticocercosis. It is often associated with increased rates of mortality. In addition, patients presented with complications may also not respond very well to the treatment.
Causes and Risk Factors of Neurocysticercosis
One can get neurocysticercosis in the following ways:
- The person harbors tapeworm infection due to ingestion of uncooked pork harboring tapeworm eggs.
- Getting infected from a person staying in neighborhood.
- An infected cook is kept for cooking from whom the infection spreads.
Pathophysiology of Neurocysticercosis
Tapeworm, Taenia solium is commonly found in the muscles of a pig. It can infect a person through two ways:
- By ingestion of pork meat which is undercooked
- By ingestion of food and water contaminated with feces of pig or feces of a carrier person.
The cysts or eggs of this worm enter our body. These contain the undeveloped larvae in them. When they enter our body, during digestion in stomach, the acidic conditions removes the cyst covering and larvae (cysticerci) are released which reach the small intestine. Due to favorable conditions, these larvae grow in size by attaching to the intestinal walls. The larvae, then, cross the intestinal walls, enter the blood stream and reach muscles, eyes and brain.
Once inside the brain, the larvae remain here for several years as viable cysts. They usually infect the cerebral cortex followed by the cerebellum. The involvement of pituitary gland is rare. The cysts may combine to form a tree-like pattern which is known as racemose neurocysticercosis.
Complications of Neurocysticercosis
In untreated or late diagnosed cases of Neurocysticercosis, the following complications are seen:
- Large cysts
- Multiple lesions in the brain along with edema
- Chronic meningitis
- Complications also include paralysis, partial blindness, lost ability to speak and some go into coma.
Most of these complications of Neurocysticercosis do not respond very well to the treatment and may lead to poor prognosis.
Diagnosis of Neurocysticercosis
The doctor will perform the two tests of the brain
- Magnetic Resonance Imaging (MRI) Scan to Diagnose Neurocysticercosis: MRI scan of brain shows whitish bobs on brain image which indicate the cysts of tapeworms.
- Computed Tomography (CT) Scan: CT scan is used for detection of calcifications.
When just MRI and CT scan results are not sufficient additional tests are required as:
- ELISA of Cerebrospinal fluid (CSF) is done
- Cerebrospinal fluid or CSF analysis for the number of mononuclear cells and eosinophils, glucose levels, protein levels, and IgG antibody levels are done.
- Stool examination
- Brain biopsy is done in extreme cases.
Treatment of Neurocysticercosis
The treatment of neurocysticercosis depends on the life stage of the cyst and its complications. It goes as follows:
- If the parasite is dead, then the treatment for Neurocysticercosis is directed against the symptoms.
- Anticonvulsants are used to treat the seizures and the duration of this treatment varies.
- If the parasite is alive and active then,
- Immunosuppressants are administered followed by anticysticercal drugs or anticystocisal drugs such as praziquantel and albendazole.
- Antiparasitic drug treatment with albendazole is useful in racemose type of cysticercosis.
- Similarly for giant subarachnoid cysts, multiple anticysticeral drug treatment is required.
- If the patient has encephalitis then steroids are given before use of anticysticeral drugs.
- Surgical treatment for Neurocysticercosis is given when -
- Hydrocephalus is present due to ventricular cysts. The excess fluid accumulation exerts pressure and requires shunt for its removal.
- Multiple cysts in racemose form present in the subarachnoidal space
- Obstruction is noticed due to arachnoiditis.
Since Neurocysticercosis is a complex disease, hence there is no single treatment pattern for all patients. Overall, the patient status, number and location of parasites determine the type of treatment to be given.
Prevention of Neurocysticercosis
Neurocysticercosis is a preventable disease. These steps to be followed to prevent it are:
- One has to maintain a good hygiene both, in the house and in the neighboring surroundings.
- One should maintain a personal hygiene (always wash hands thoroughly after defecation and urination).
- The pork meat should be thoroughly cooked.
- Pigs to be given anti-parasitic medications and vaccinated against T.solium. It must be noted that these vaccines are not for humans.
Human neurocysticercosis is a complex disease. The epileptic seizures are the acquired form of late adult onset. The mild form of neurocysticercosis is treatable; however, the complicated ones may be difficult to treat and often have poor prognosis. Appropriate diagnosis with CT scan is necessary. However this facility needs to be implemented in the rural areas as well which is still lacking. Treatment of neurocysticercosis is long and costly; hence, it is good to adopt preventive measures. Overall, the combined efforts of sectors such as healthcare, veterinary sciences and education of the people can help to control T.solium infections.