Asymptomatic Giant Intraventricular Cysticercosis: A Case Report

Abstract

Neurocysticercosis is a growing health problem in the United States and worldwide. Diagnosis and treatment is challenging especially if the physician is not familiar with this condition. The World Health Organization (WHO) estimates that neurocysticercosis affects 50 million people worldwide, especially in developing countries and causes approximately 50,000 deaths annually.¹ Neurocysticercosis is of emerging importance in the United States especially in Hawai‘i because of immigration from disease-endemic regions.²

We present a case of a young Chinese immigrant male who presented with impressive imaging studies of a giant intraventricular neurocysticercosis. This case emphasizes the importance of recognizing neurocysticercosis, especially in the immigrant population.

Introduction

Humans are definitive and intermediate hosts in the life cycle of Taenia solium (pork tapeworm). Humans become carriers of Taenia solium by ingesting undercooked pork which contains cysticerci in the muscle tissue. The scolex evaginates and attaches in the human intestines. Proglottids arise from the scolex and mature over a period of 2–4 months. Each proglottid segment contains 50,000 – 100,000 eggs which are shed in the stool. This condition is called taeniasis.

Cysticercosis is caused by ingestion of Taenia solium eggs shed in the stools of human tapeworm carriers. Humans can become accidental intermediate hosts by either ingesting food contaminated with eggs of adult tapeworms or by reverse peristalsis of eggs into the stomach in patients harboring tapeworms in their small intestine.^3,4 The eggs hatch in the gastrointestinal tract and develop into the larval stage in 3–8 weeks. Thereafter, larvae disseminate to several body tissues with a strong tropism for the central nervous system, causing neurocysticercosis.⁵

Cysticercosis is endemic in many regions of Central and South America, sub-Saharan Africa, India, and Asia.⁶ The prevalence of cysticercosis is higher in rural areas with poor sanitation and where pigs are raised. In the United States, there is a high prevalence of cysticercosis among Latin American immigrants in locations such as Arizona, California, and Texas.⁷ Education about disease transmission and prevention should be emphasized especially in endemic areas to prevent fecal-oral transmission and to reduce Taenia solium carriers. Prevention strategies include improving sanitary conditions, encouraging good personal hygiene, and treating carriers.

Neurocysticercosis is characterized by its location. Parenchymal neurocysticercosis involves brain tissues while extraparenchymal neurocysticercosis involves other locations including the intraventricular space, subarachnoid space, and spinal cord.⁸ The intraventricular form of neurocysticercosis is seen in 7%–45% of cases.^9,10 The fourth ventricle is the most common site of infestation (54%–64%), followed by the third ventricle (23%–27%), the lateral ventricles (11%–14%) and the aqueduct of Sylvius (9%).^5,9,10

Manifestations of neurocysticercosis are varied, ranging from asymptomatic to severe neurological symptoms. Presentations of neurocysticercosis depend on multiple factors including the number of lesions, location, type of cysticercus, its stage of development and involution, and intensity of the host immune response.¹¹ Parenchymal neurocysticercosis is usually associated with seizures and headaches. Often times, patients with extraparenchymal neurocysticercosis present with signs and symptoms of increased intracranial pressure secondary to hydrocephalus caused by mechanical obstruction of the cerebrospinal fluid (CSF) pathway or associated ependymitis or basal arachnoiditis, with resulting failure of CSF absorption.¹²

Usually, cysticerci do not cause inflammation of the surrounding tissue. Cysticerci have the ability to produce a variety of substances that inhibit host inflammatory responses. However, cysts could become degraded over time and cause edema and inflammation. Ultimately, the parasites transform into calcified nodules, presenting as calcified granulomatous lesions without associated edema or enhancement in imaging studies.

Gadolinium-enhanced magnetic resonance imaging (MRI) is the preferred imaging method for diagnosis of neurocysticercosis due to its superior contrast resolution and direct multiplanar capability.^3,13–15 It is the most accurate technique to assess the degree of infection, location, and evolutionary stage of the parasite.¹

We present a case of asymptomatic large intraventricular neurocysticercosis treated with conservative management.

Case Presentation

A 37-year-old Chinese man who was previously healthy without significant past medical problems presented to our facility after sustaining a head injury from a car accident. He briefly lost consciousness during the incident and had a transient headache. He was admitted to the hospital for further investigation and close observation of neurological symptoms. Physical examination showed no significant neurological deficits. Non-contrast head computerized tomography (CT) was obtained to rule out intracranial abnormality. The results showed a large cystic lesion measuring 5x6x7 cm in diameter in the right lateral ventricle, with a partially calcified lesion (Figure 1). Gadolinium-enhanced MRI of the brain (Figure 2) was obtained and revealed a large solitary right lateral ventricular cystic lesion containing a partially calcified mural nodule. There is evidence of dysgenesis of the corpus callosum versus thinning of the posterior corpus callosum due to chronic mass effect. No surrounding edema or inflammation was observed. The findings were highly suggestive of intraventricular cysticercosis. A complete blood count (CBC) revealed no evidence of eosinophilia and a stool sample for parasite confirmation was not obtained in this patient.

Figure 1.

A computed tomography of the brain without contrast shows a 7.4 × 5.7 × 6.2 cm right occipital intraventricular cystic lesion with a small partially calcified mural nodule and dilatation of the right lateral ventricle.

Figure 2.

Magnetic resonance imaging of the brain with/without contrast (Panels A and B respectively) show a large solitary right ventricular cyst with partially calcified mural nodule. There is evidence of dysgenesis of the corpus callosum versus thinning of the posterior corpus callosum due to chronic mass effect.

Further history revealed that he was born and raised in China, moved to Mexico, and then to Hawai‘i three years prior to admission. He denied previous history of chronic headache, weakness, seizures, or visual impairment. He denied history of tapeworm infection or household contact. The MRI result prompted neurosurgical evaluation. As the patient was asymptomatic and had no hydrocephalus, close outpatient follow-up without surgical intervention or treatment with medications was planned. After 6 months of follow up, the patient remained asymptomatic. Further MRI follow up revealed no change in the size of the cystic lesion or degree of surrounding inflammation.

Discussion

Neurocysticercosis is mostly diagnosed based on clinical presentation and imaging studies.^16,17 Peripheral eosinophilia is usually absent. Stool examination for parasite is insensitive since most neurocysticercosis patients do not have a viable intestinal tapeworm at the time of diagnosis. Serology tests can be helpful but are not always necessary for diagnosis. Enzyme-linked immunoelectrotransfer blot assay (EITB) of either serum or CSF can be negative if the cyst is calcified. Moreover, a positive test can persist for years even after death of parasites. Thus, a positive test does not necessarily indicate active disease. The presence of scolex through imaging is a pathognomonic feature for diagnosis of neurocysticercosis.¹⁷

This patient fits the definition of a “probable case” due to the absence of scolex in imaging studies. MRI of the brain revealed a calcified granuloma without surrounding edema. No viable parasite presented. Serologic tests were not performed in this case. The major differential diagnosis is an echinococcosis hydatid cyst which is mostly seen as a single cystic brain lesion. Cerebral hydatid cysts are extremely rare, comprising about 2% of all intracranial masses.^18,19 Hydatid cysts are mostly located in intraparenchymal areas especially parietal areas or the middle cerebral artery (MCA) distribution.^18,20 They are less likely in cases where the cyst is located intraventricularly.

Various modalities including cysticidal therapy, steroids, antiepileptic medications, neurosurgical removal and ventriculo-peritoneal shunt have been used to treat neurocysticercosis with the ultimate goal of eradicating the parasites, minimizing the inflammatory response, and releasing the obstruction or mass effect.^1,14 Despite its high global health burden, the optimal treatment for intraventricular neurocysticercosis is still controversial.

The utility and safety of cysticidal therapy in conjunction with steroids in intraventricular neurocysticercosis is still unclear, as larvae are more recalcitrant to the treatment than in the parenchymal form and the treatment itself can trigger inflammation, causing ependymitis and arachnoiditis.^1,21 Surgery, especially endoscopic, has shown encouraging results and is usually recommended for intraventricular cyst causing significant mass effect, hydrocephalus, or when the diagnosis is uncertain.^4,14

While surgery promises to be a fast and definitive method of cyst removal and eliminating risk of mechanical obstruction, chronic hydrocephalus related to inflammatory damage can still occur.^3,22,23 Other potential life-threatening complications such as cerebral infarction and intraventricular bleeding have also been reported.^1,23

Treatment for neurocysticercosis should be tailored individually. This patient did not have signs of increased intracranial pressure, nor obstructive hydrocephalus that prompted an immediate intervention. If the cyst had been located in the fourth ventricle which is vulnerable to obstruction, surgical intervention would have been considered.²⁴ The patient's brain MRI showed a non-obstructing intraventricular cystic lesion in a calcified stage without surrounding edema or inflammation. As a result, medical management with cysticidal therapy and steroid was of limited value in this circumstance. In this patient, deciding whether or not to perform endoscopic neurosurgery was challenging. As previously discussed, endoscopic surgery is an invasive procedure with multiple possible complications. In the end, surgery was not pursued because of concerns that removal of the large cyst might increase the risk of secondary hydrocephalus due to inflammatory damage.

Moreover, the patient was asymptomatic and the cystic lesion appeared to be in the calcific stage without evidence of inflammation or obstruction, providing further justification against surgical intervention. However, since this cyst was relatively large, the patient will be closely monitored by clinical symptoms and MRI study which may prompt neurosurgical intervention in the future.

Summary

We present a case of an asymptomatic patient, with an atypically large intraventricular cysticercosis, who was managed by close observation. The conservative approach in a seemingly uncomplicated patient emphasizes the importance of tailoring the management of neurocysticercosis on an individual basis.

Conflict of Interest

None of the authors identify a conflict of interest.