Single-day praziquantel therapy for neurocysticercosis

Clinical symptoms, diagnosis, and treatment of neurocysticercosis

The infection of the nervous system by the cystic larvae of Taenia solium (neurocysticercosis) is a frequent cause of seizure disorders. Neurocysticercosis is endemic or presumed to be endemic in many low-income countries. The lifecycle of the worm and the clinical manifestations of neurocysticercosis are well established, and CT and MRI have substantially improved knowledge of the disease course. Improvements in immunodiagnosis have further advanced comprehension of the pathophysiology of this disease. This knowledge has led to individualised treatment approaches that account for the involvement of parenchymal or extraparenchymal spaces, the number and form of parasites, and the extent of degeneration and associated inflammation. Clinical investigations are focused on development of effective treatments and reduction of side-effects induced by treatment, such as seizures, hydrocephalus, infarcts, and neuroinjury.

Neurocysticercosis

Cysticercosis, an infection caused by the cystic larvae of the pork tapeworm Taenia solium, is one of the most frequent parasitic infections of the human nervous system (neurocysticercosis). It is endemic in most of Latin America, the sub-Saharan Africa, and vast parts of Asia, including the Indian subcontinent. It has also been increasingly diagnosed in developed countries because of migration of people from endemic zones and exposure in travelers. The life cycle involves the development of the adult tapeworm in the human small intestine (after ingesting infected pork with cysts) and larval infection in pig tissues (after ingesting human stools containing the eggs of the tapeworm). Humans get infected by the fecal-oral route, most often from a direct contact with an asymptomatic Taenia carrier. Most common clinical presentations are seizures (particularly late-onset seizures), chronic headaches, and intracranial hypertension. However, cysticerci can locate anywhere in the human nervous system, thus potentially causing almost any neurological syndrome and making clinical diagnosis a difficult task. Neuroimaging is the main diagnostic tool, and specific serology confirms the diagnosis and helps to define the diagnosis when images are unclear. Factors such as location (extraparenchymal versus intraparenchymal), number, size and evolutive stage of the parasites determine the clinical manifestations, therapeutic approach, and prognosis. Management includes symptomatic drugs (analgesics, antiepileptic drugs, anti-inflammatory agents) and in many cases cysticidal drugs, either albendazole or praziquantel. In recent years, efforts have focused on transmission control and potential elimination in endemic regions.

Neurocysticercosis in sub-Saharan Africa: a review of prevalence, clinical characteristics, diagnosis, and management

Neurocysticercosis has been recognized as a major cause of secondary epilepsy worldwide. So far, most of the knowledge about the disease comes from Latin America and the Indian subcontinent. Unfortunately, in sub-Saharan Africa the condition was neglected for a long time, mainly owing to the lack of appropriate diagnostic tools. This review therefore focuses on the prevalence of neurocysticercosis in sub-Saharan Africa, the clinical picture with emphasis on epilepsy, as well as the diagnosis and treatment of neurocysticercosis and its related epilepsy/epileptic seizures in African resource-poor settings.

Cysticercosis of the central nervous system: how should it be managed?

PURPOSE OF REVIEW

Taenia solium neurocysticercosis (NCC) has been long recognized as an important cause of neurological morbidity in most of the world. Unwarranted generalization of diagnostic and treatment recommendations made it difficult to assess individual prognosis and responses for each type of NCC. Understanding of the main clinical presentations (dependent on number, location, size, and stage of parasites, as well as on the immune response of the host) allows a better view of treatment options and expected outcomes.

RECENT FINDINGS

Current treatment options are still limited and involve symptomatic agents, antiparasitic agents, or surgery. The importance of adequate symptomatic management, the potential for improved antiparasitic treatment regimes, in particular combination therapy, and the increasingly important role of minimally invasive neurosurgery are also reviewed in this article.

SUMMARY

Treatment decisions in NCC should be individualized in relation to the type of NCC. Initial measures should focus on the symptomatic management before considering antiparasitic therapy when appropriate. Appropriate patient categorization, new antiparasitic regimes, and minimally invasive surgery are improving the prognosis of patients with NCC.

Diagnosis and treatment of neurocysticercosis

Neurocysticercosis is a parasitic disease caused by the larval (cystic) form of the pork cestode tapeworm, Taenia solium, and is a major cause of acquired seizures and epilepsy worldwide. Development of sensitive and specific diagnostic methods, particularly CT and MRI, has revolutionized our knowledge of the burden of cysticercosis infection and disease, and has led to the development of effective antihelminthic treatments for neurocysticercosis. The importance of calcified granulomas with perilesional edema as foci of seizures and epilepsy in populations where neurocysticercosis is endemic is newly recognized, and indicates that treatment with anti-inflammatory agents could have a role in controlling or preventing epilepsy in these patients. Importantly, neurocysticercosis is one of the few diseases that could potentially be controlled or eliminated-an accomplishment that would prevent millions of cases of epilepsy. This Review examines the rationale for treatment of neurocysticercosis and highlights the essential role of inflammation in the pathogenesis of disease, the exacerbation of symptoms that occurs as a result of antihelminthic treatment, and the limitations of current antihelminthic and anti-inflammatory treatments.

Antiparasitic drugs in neurocysticercosis: albendazole or praziquantel?

This article evaluates the findings and conclusions of a recent meta-analysis of published data comparing the efficacy of the treatment of neurocysticercosis with albendazole and praziquantel in terms of both resolution of brain cysts and seizure control. From 103 related articles indexed in PubMed and the Cochrane Database of Controlled Trials, and quoted in reference lists, six prospective trials comparing albendazole with praziquantel (including patients infected with parasites in their cystic stage without perilesional inflammation and examining partial or total disappearance of cysts and/or control of seizures) were evaluated. The small number and heterogeneity of the included studies makes it difficult to assess the analyses provided. One of the studies was a pilot trial, at least three had grossly inadequate sample sizes and, owing to the way in which the data are presented in one of the studies, it is not possible to extract the proportion of parasites that resolved. None of the studies was designed to evaluate seizure control. The current published data does not provide enough basis to determine conclusively the superiority of either albendazole or praziquantel as first-line treatment of neurocysticercosis, and the choice of an antiparasitic drug is still guided by collateral factors, including drug availability and costs.

Albendazole versus praziquantel in the treatment of neurocysticercosis: a meta-analysis of comparative trials

Background

Neurocysticercosis, infection of the brain with larvae of Taenia solium (pork tapeworm), is one of several forms of human cysticercosis caused by this organism. We investigated the role of albendazole and praziquantel in the treatment of patients with parenchymal neurocysticercosis by performing a meta-analysis of comparative trials of their effectiveness and safety.

Methods and Principal Findings

We performed a search in the PubMed database, Cochrane Database of Controlled Trials, and in references of relevant articles. Six studies were included in the meta-analysis. Albendazole was associated with better control of seizures than praziquantel in the pooled data analysis, when the generic inverse variance method was used to combine the incidence of seizure control in the included trials (patients without seizures/[patients×years at risk]) (156 patients in 4 studies, point effect estimate [incidence rate ratio] = 4.94, 95% confidence interval 2.45–9.98). In addition, albendazole was associated with better effectiveness than praziquantel in the total disappearance of cysts (335 patients in 6 studies, random effects model, OR = 2.30, 95% CI 1.06–5.00). There was no difference between albendazole and praziquantel in reduction of cysts, proportion of patients with adverse events, and development of intracranial hypertension due to the administered therapy.

Conclusions

A critical review of the available data from comparative trials suggests that albendazole is more effective than praziquantel regarding clinically important outcomes in patients with neurocysticercosis. Nevertheless, given the relative scarcity of trials, more comparative interventional studies—especially randomized controlled trials—are required to draw a safe conclusion about the best regimen for the treatment of patients with parenchymal neurocysticercosis.

Neurocysticercosis is a parasitic disease caused by the pork tapeworm, Taenia solium, when the larval form of the parasite lodges in the central nervous system. This disease is most commonly found among members of agricultural societies with poor sanitary conditions and economies based on breeding livestock (especially pigs) with low hygiene standards. It is a disease with long history in humans, and the usual therapeutic intervention was surgery until the development of antiparasitic cysticidal agents, the most common being praziquantel and albendazole. T. solium infection can take many different forms in humans, but we concentrated on parenchymal neurocysticercosis with viable cysts. A consensus statement by a panel of experts on the subject supports the use of antiparasitic treatment, but does not indicate either albendazole or praziquantel as the drug of choice for this type of neurocysticercosis, because data from single relevant clinical trials are not conclusive. We conducted a meta-analysis to further evaluate the comparative effectiveness and safety of albendazole and praziquantel for this particular type of neurocysticercosis. The outcomes of our meta-analysis suggest that albendazole is more effective than praziquantel in controlling seizures in affected patients and in leading to the total disappearance of cysts and subsequently cure of patients with neurocysticercosis.

Control of Taenia solium cysticercosis/taeniosis

Cysticercosis is emerging as a serious public health and agricultural problem in many poorer countries of Latin America, Africa, and Asia. Caused by the pork tapeworm, Taenia solium, this zoonotic disease forms larval cysts in humans and pigs that can lead to epilepsy and death in humans, reduces the market value of pigs and makes pork unsafe to eat. It occurs where pigs range freely, sanitation is poor, and meat inspection is absent or inadequate, and is thus strongly associated with poverty and smallholder farming. Although theoretically easy to control and declared eradicable cysticercosis remains neglected in most endemic countries due to lack of information and awareness about the extent of the problem, suitable diagnostic and management capacity, and appropriate prevention and control strategies. Human neurocysticercosis occurs when the larval cysts develop in the brain. It is considered to be the most common parasitic infection of the human nervous system and the most frequent preventable cause of epilepsy in the developing world. Thus far the infection has not been eliminated from any region by a specific program, and no national control programs are yet in place. We consider the tools available for combating cysticercosis and suggest simple packages of interventions, which can be conducted utilizing existing services and structures in the endemic countries to provide appropriate and sustainable control of the disease.

Neurocysticercosis: updated concepts about an old disease

Neurocysticercosis, the infection of the human brain by the larvae of Taenia solium, is a major cause of acquired epilepsy in most low-income countries. Cases of neurocysticercosis are becoming more common in high-income countries because of increased migration and travel. Diagnosis by neuroimaging and serological assessment has greatly improved over the past decade, and the natural progression of the disease and response to antiparasitic drugs is now much better understood. Neurocysticercosis is potentially eradicable, and control interventions are underway to eliminate this infection. Meanwhile, updated information on diagnosis and management of neurocysticercosis is required, especially for clinicians who are unfamiliar with its wide array of clinical presentations.

Taenia solium cysticercosis

The larval stage of the pork tapeworm (Taenia solium) infects the human nervous system, causing neurocysticercosis. This disease is one of the main causes of epileptic seizures in many less developed countries and is also increasingly seen in more developed countries because of immigration from endemic areas. Little information is available on the natural evolution of taeniasis or cysticercosis. Available therapeutic measures include steroids, treatments for symptoms, surgery, and, more controversially, antiparasitic drugs to kill brain parasites. Efforts to control and eliminate this disease are underway through antiparasitic treatment of endemic populations, development of pig vaccines, and other measures.

Management of neurocysticercosis

Neurocysticercosis is a common cause of neurological disease in developing countries and a major cause of epilepsy worldwide. A unique characteristic of human neurocysticercosis is that the living parasite is very well tolerated in human brain, so symptoms and clinical disease primarily result from death of the organism and accompanying inflammatory reaction in the human CNS. Among the diverse clinical manifestations of human neurocysticercosis, seizures are the most common, but other clinical problems occur, depending upon the localisation and viability of the parasite. Although both praziquantel and albendazole are effective agents, there is controversy about their role in several forms of the disease. Systematic reviews have pointed out the limited quality of available data on therapy. At a recent international conference convened to develop guidelines for treatment of this disease, areas of consensus and disagreement on the role of antiparasitic therapy were discussed. It was clear to all that cysticercosis cannot be regarded as a single disorder; treatment needs to be modified based on the location and number of cysticerci and the host response. There was a strong consensus that there is no role for antiparasitic drugs in patients with only calcified lesions. Studies suggest that patients with single enhancing lesions will do well regardless of antiparasitic therapy. Antiparasitic drugs are contraindicated in patients with cerebral oedema (cysticercal encephalitis). Most experts strongly recommend antiparasitic therapy in patients with multiple subarachnoid cysticerci or giant cysticerci. In patients with ventricular cysticerci, endoscopic removal is the preferred therapy. However, recent evidence suggests that placement of a ventricular shunt followed by antiparasitic therapy is an acceptable alternative. Standard treatment for localization-related epilepsy is effective for seizures caused by cysticercosis. In general, seizures are easily controlled in this illness. While many controversies regarding the treatment of patients with neurocysticercosis were not resolved at the international consensus conference, participants did conclude that controlled prospective studies are required to define optimal therapy for the infection and that treatment of infected individuals must be individualised.

Human case management and treatment of cysticercosis

Disease manifestations due to neurocysticercosis vary markedly and depend upon the location, size and number of cysts as well as the viability or degeneration of cysts and presence, type and degree of host response. Accordingly, the clinical management for each patient should be individualized. Treatment modalities include: (1) larvicidal drugs such as albendazole or praziquantel in patients with viable cysts; (2) corticosteroids or other agents to suppress or prevent the host's immune response; (3) anti-seizure medication(s) to treat or prevent recurrent seizures; (4) surgical interventions; and (5) the use of supportive family, social or health agencies in impaired individuals. Although it is known that larvicidal treatment kills viable cysts that commonly resolve or calcify, the clinical benefit of this treatment in the most common presentations is unproven. However, medical treatment of giant subarachnoid cysts, large parenchymal cysts or orbital cysts causing mass effect has led to definite clinical improvement in uncontrolled trials. Whether there is faster radiological improvement and/or clinical benefit in the treatment of cysts showing signs of inflammation by magnetic resonance imaging (enhancement and/or edema) is like-wise controversial. There is no general understanding when or how to use corticosteroids to suppress natural or treatment-induced inflammation around cysts although their use when inflammation contributes or could be expected to cause undue morbidity or mortality is reasonable. Anti-seizure medication should usually be employed in patients with seizures or patients who may likely develop seizures. Surgical intervention is required to alleviate mass effect, remove some cysts causing obstruction of the ventricles, shunt placement for hydrocephalus, and sometimes for removal and/or decompression of large or critically located cysts before larvicidal treatment.

Current consensus guidelines for treatment of neurocysticercosis

Taenia solium neurocysticercosis is a common cause of epileptic seizures and other neurological morbidity in most developing countries. It is also an increasingly common diagnosis in industrialized countries because of immigration from areas where it is endemic. Its clinical manifestations are highly variable and depend on the number, stage, and size of the lesions and the host's immune response. In part due to this variability, major discrepancies exist in the treatment of neurocysticercosis. A panel of experts in taeniasis/cysticercosis discussed the evidence on treatment of neurocysticercosis for each clinical presentation, and we present the panel's consensus and areas of disagreement. Overall, four general recommendations were made: (i) individualize therapeutic decisions, including whether to use antiparasitic drugs, based on the number, location, and viability of the parasites within the nervous system; (ii) actively manage growing cysticerci either with antiparasitic drugs or surgical excision; (iii) prioritize the management of intracranial hypertension secondary to neurocysticercosis before considering any other form of therapy; and (iv) manage seizures as done for seizures due to other causes of secondary seizures (remote symptomatic seizures) because they are due to an organic focus that has been present for a long time.

Review of neurocysticercosis

In the neurosurgical services in many developing countries, treatment of neurocysticercosis (NCC) accounts for greater than 10% of brain surgical procedures and approximately 15% of neurological consultations. In these areas brain cysticercosis is the leading cause of hydrocephalus in adults and the first cause of late-onset epilepsy. During the last two decades, successful medical treatment has been established. Additionally, neuroimaging and immunological studies have clearly defined the topography, pathophysiological mechanisms, and biological status of these lesions. Thus, selection of cases for medical or surgical treatment has improved; in a significant number of cases, both interventions are required. New therapies with either albendazole or praziquantel have respectively reduced to 8 days and to 1 day the course of anticysticidal therapy, which now is fast, effective, inexpensive, atoxic, and convenient, particularly in endemic areas where most patients belong to the lower socioeconomic groups. Additionally, the rational use of steroid agents facilitates the treatment of inflammation, a conspicuous accompaniment in cases of NCC. A major effort, however, is still required to eradicate this disease.

Failure of one-day praziquantel treatment in patients with multiple neurocysticercosis lesions

A recently described one-day regimen of praziquantel (PZQ) therapy for neurocysticercosis (NCC), three doses of 25 mg/k given at 2 h intervals, was applied in eight patients with viable NCC cysts without any evidence of inflammation. Resolution of lesions in computed tomography (CT) was observed in all five patients with a single cyst, whereas all cysts survived in three patients with multiple brain parasites. One-day praziquantel is a good regimen for patients with a single viable brain cysticercus but is poorly effective for multiple cysts.

Short regimen of praziquantel in the treatment of single brain enhancing lesions

Twenty-six patients with single enhancing brain lesion (SEL) were openly assigned to receive single-day praziquantel therapy (n=14), or not (n=12). From 14 treated patients, complete resolution was found in 11, partial resolution in two, and the remaining case was later diagnosed as an arteriovenous malformation. Side effects presented in only one patient and remitted in the same day with symptomatic treatment. Conversely, the lesions persisted unchanged in six of 12 patients in the non-treatment group. Untreated patients with persisting lesions were prescribed praziquantel treatment. After this, SELs disappeared in three cases, other diagnoses (brain tuberculoma and arteriovenous malformation) were made in two, and one was not evaluated. When analyzed in regard to the baseline serology, resolution of lesions on computed tomography was found in 13 (complete=12, partial=1) of 14 seropositive patients, whereas it only happened in six (complete=5, partial=1) of 12 seronegative patients. Serological screening defines a subset of SEL patients with good prognosis. If antiparasitic therapy is to be used in patients with SEL, and we cannot find a strong argument against it, single-day praziquantel is the regimen of choice based on duration, costs, and minimal side effects.

Taenia solium cysticercosis

Cysticercosis, the infection of the larval tissue stage of the pork tapeworm, Taenia solium, is endemic to most developing countries and increasingly is seen in industrialized countries because of immigration. Human infection is a major cause of acquired epilepsy, and porcine infection causes important economic losses to farm workers. Clinical manifestations vary because of the variable number, size, and location of the cysts and the immune response of the host. Diagnosis is based on imaging techniques (CT and MR imaging) and serology (immunoblot). Current research efforts are centered on control and eradication of the taeniasis cysticercosis complex in endemic areas.

Possible association between Taenia solium cysticercosis and cancer: increased frequency of DNA damage in peripheral lymphocytes from neurocysticercosis patients

Helminths, particularly some Schistosoma species, have been associated with cancer in humans. Neurocysticercosis, produced by cysticerci of the helminth Taenia solium, has been associated with the emergence of brain tumours and haematological malignancies. Local tumours, such as glioblastoma, could be explained by the induction of DNA damage in cells surrounding the cysticercus and chronically exposed to an inflammatory host response. However, systemic effects such as haematological malignancies are not easy to understand. The present work was conducted in Mexico to find out whether DNA damage arises in peripheral lymphocytes in patients with neurocysticercosis. We utilized a highly sensitive technique to analyse chromosomal aberrations, in-situ hybridization with probes against chromosomes 1, 2 and 4, and in addition the blocked-cytokinesis technique was used to determine the formation of micronuclei, a peculiar form of DNA damage. The study was made in lymphocytes from 8 patients before and after the administration of praziquantel, 1 of the 2 drugs used for neurocysticercosis treatment. The frequencies of chromosome aberrations and micronuclei in peripheral blood lymphocytes were higher in the infected patients as compared to those observed both in healthy donors and in the group of patients after praziquantel therapy. Our results suggest that chromosome aberrations induced in peripheral cells during neurocysticercosis could be associated with the development of haematological neoplasias.

Neurocysticercosis and acquired cerebral toxoplasmosis in children

Neurocysticercosis, prevalent wherever pigs are raised in the presence of poor sanitation, is the most common identifiable cause of new-onset epilepsy throughout the developing world. As immigration patterns have changed, children with neurocysticercosis are seen throughout the United States. Acute cysticercosis, the most common manifestation in children, reflects the host response to the dying parasite. Children typically present with seizures and have an excellent prognosis. Neuroimaging demonstrates a single ring or nodular enhancing lesion surrounded by edema. Short-term anticonvulsant therapy is indicated, but treatment with antiparasitic agents is not required. Other forms, such as active cysts (intact organism), intraventricular or subarachnoid racemous cysticercosis, and cysticercal meningoencephalitis, are less common manifestations of parasitic infection. Toxoplasmosis, caused by the parasite Toxoplasma gondii, can be acquired by ingestion of infected undercooked meat or from oocytes shed in cat feces. Acquired cerebral toxoplasmosis, due to primary or reactivated infections, rarely occurs in immunocompetent children. In children who are immunodeficient as the result of AIDS, chemotherapy, tissue transplantation, or congenital immunodeficiency, toxoplasmosis may be difficult to distinguish from cerebral lymphoma. A variety of techniques, including neuroimaging, Thallium-201 SPECT, polymerase chain reaction analysis of CSF, and special histological methods, may be used to diagnose acquired toxoplasmosis. Antiparasitic therapy, using pyrimethamine and sulfadiazine, and serial neuroimaging often enable clinicians to differentiate toxoplasmosis from other central nervous system lesions. Toxoplasmosis may respond to other antimicrobials, including macrolide antibiotics, dapsone, clinidamycin, and atovaquone. Suppressive treatment is generally required for life in immunodeficient patients. Immunodeficient children with acquired toxoplasmosis have high rates of mortality and neurological sequelae.

Recent Developments in the Epidemiology, Diagnosis, Treatment, and Prevention of Neurocysticercosis

Neuroimaging studies have revealed that neurocysticercosis is a major cause of neurologic disease in most developing countries and is an emerging disease in industrialized areas. Patients with neurocysticercosis present mainly with seizures (parenchymal form) or intracranial hypertension (ventricular/subarachnoid forms). Management should be based on a thorough understanding of the pathogenesis and natural history of infection. Symptoms of active parenchymal neurocysticercosis result from the host inflammatory response to the dying metacestode form. Careful use of anticonvulsants will result in an excellent clinical outcome. The anthelminthic drugs albendazole and praziquantel are effective in killing the cysts, but their long-term effect on prognosis is unproven. Patients with obstructive hydrocephalus from ventricular cysts should be managed surgically by cerebrospinal fluid diversion or cyst removal. Treatment with antiparasitic drugs (especially albendazole) and corticosteroids may decrease the incidence of shunt failure. Current efforts at control of the disease include mass human or porcine chemotherapy in endemic zones and vaccination.

Pharmacokinetic study of praziquantel administered alone and in combination with cimetidine in a single-day therapeutic regimen

A brief therapeutic regimen of praziquantel, reduced to a single day, has been effective for treatment of neurocysticercosis. To study its pharmacokinetic characteristics, levels of praziquantel in plasma were determined for eight healthy volunteers after the administration of three oral doses of 25 mg/kg of body weight given at 2-h intervals, alone and with the simultaneous administration of cimetidine. Each volunteer received both regimens in a randomized crossover design. Blood samples were taken during a period of 12 h, and praziquantel concentration was measured by high-performance liquid chromatography. Levels of praziquantel in plasma remained above 300 ng/ml during a period of 12 h; they increased 100% when cimetidine was jointly administered. Compared with other regimens, the high levels obtained and the longer duration of action seem to be advantageous in prolonging the exposure of the parasites to the drug and support previous clinical experience showing that the treatment of neurocysticercosis with praziquantel can be reduced from 2 weeks to 1 day with the drug still retaining its cysticidal properties. Moreover, simultaneous administration of praziquantel and cimetidine could improve further the efficacy of the single-day therapy for cysticercosis and other parasitic diseases, such as schistosomiasis.