Obstructive hydrocephalus: when subarachnoid cysts alert to the challenging diagnosis of neurocysticercosis

Introduction

Neurocysticercosis (NCC) is an infectious ailment caused by the ingestion of encysted larval stages of the pork tapeworm Taenia solium (T. solium), typically acquired through contaminated food or direct transmission from a Taenia carrier via the fecal-oral route (1). This condition is the most common parasitic disease affecting the brain and nervous system, representing a significant challenge for public health (2). It impacts not only lower-income countries but also more developed nations, particularly those with significant immigration from regions where the disease is endemic (3). The importance of diagnostic imaging using techniques like computed tomography (CT) and magnetic resonance imaging (MRI) is well-documented in the medical field, as they are crucial for accurate diagnosis (4). These imaging modalities are crucial for detecting inflammatory changes, identifying mass lesions, assessing vasculitis, arachnoiditis, and evaluating the involvement of the ventricular system (5). However, advancements in radiology have introduced innovative diagnostic strategies for NCC, including the use of the three-dimensional constructive interference in steady state (3D CISS) sequence for subarachnoid lesions, which is highly relevant to the disease (6). Additionally, new tools enable the identification of associated findings, such as the vessel wall imaging (VWI) sequence for detecting vasculitis, with or without infarction, and the role of susceptibility-weighted imaging (SWI) in evaluating calcified lesions (7).

Case presentation

A 59-year-old female patient, from Varzelândia, in the state of Minas Gerais, where she continues to reside, presented with a history of dizziness and headaches, accompanied by gait disturbances, which progressively worsened over three years. She also reported memory loss and urinary incontinence, confirmed by her relatives. Upon neurological examination, she exhibited upward vertical gaze paresis, signs of cerebellar ataxia (dysmetria, intention tremor in both upper limbs, and movement decomposition), and typical peripheral nystagmus. CT (Figure 1) revealed hydrocephalus and hypodensities in the periventricular white matter, consistent with cerebrospinal fluid (CSF) transependymal edema. Cysts in the infratentorial subarachnoid spaces were also observed, indicating a potential diagnosis of NCC. Subsequent MRI confirmed the diagnosis of racemose NCC (Figures 2,3).

Figure 1 Axial non-contrast CT at the level of the body of the lateral ventricles (A), and mid-sagittal non-contrast CT (B). (A) Hydrocephalus with cerebrospinal fluid transudation is evident (arrow). (B) Hydrocephalus is demonstrated, along with a cyst visualized inside the cisterna magna (arrow). CT, computed tomography.

Figure 2 This figure demonstrates hydrocephalus and cystic lesions in the subarachnoid space. (A) Axial FLAIR-weighted image illustrating enlarged lateral ventricles (hydrocephalus) with hyperintensities in the surrounding white matter, suggestive of transependymal edema. (B) Sagittal and (C) axial three-dimensional CISS images reveal intraventricular cystic lesions (arrow) and cisternal cysts without scolex, resembling a “bunch of grapes” (arrowheads), consistent with racemose cysticercosis. CISS, constructive interference in steady state; FLAIR, fluid attenuated inversion recovery.

Figure 3 This figure demonstrates cisternal cysts and regression of hydrocephalus. (A) Axial three-dimensional CISS image demonstrating cisternal cysts (arrows). (B) Mid-sagittal FLAIR image demonstrating regression of hydrocephalus and cysts in the cisterna magna (arrow). CISS, constructive interference in steady state; FLAIR, fluid attenuated inversion recovery.

She was admitted to Hospital das Clínicas (Clinics Hospital), State University of Campinas (UNICAMP) under the care of the neurosurgery team and underwent ventriculoperitoneal shunt placement. Surgical removal of the intraventricular cysts was considered inappropriate due to the high risk of cranial nerve damage. As a result, dexamethasone was initiated, followed by antiparasitic drugs (albendazole 15 mg/kg/day for 15 days, one cycle) and symptomatic treatment for vertigo (betahistine 24 mg twice a day). The patient remains under outpatient follow-up, with significant improvement in headache, urinary incontinence, and cognitive impairment, though she still experiences significant vertigo. Hydrocephalus was resolved (Figure 4). The patient showed a favorable outcome, remaining clinically stable during outpatient follow-up, with continued treatment of only betahistine and successful corticosteroid withdrawal. She undergoes regular consultations in neuro infectology every 4–6 months and remains stable, with no evidence of cyst progression on neuroimaging.

Figure 4 Axial (A) and coronal (B) non-contrast CT images following ventricular shunt placement. The distal catheter is visible in the left lateral ventricle (arrow), with significant improvement in hydrocephalus. A small amount of blood is observed in the atrium of the left lateral ventricle (arrowhead), likely related to the surgical procedure. Transependymal edema is also noted (empty arrows). CT, computed tomography.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

NCC is a disease that results from consuming the immature forms of T. solium, a type of tapeworm found in pigs. This infection is usually acquired through eating contaminated food or by direct contact with a carrier through the fecal-oral route. NCC represents a major health concern, particularly in regions where the disease is prevalent, affecting both the brain and nervous system and presenting significant challenges to healthcare systems. It affects not only developing nations but also industrialized countries with high immigration rates from endemic regions (1). The patient in this case is originally from and resides in Minas Gerais, an endemic area for NCC in Brazil, where consumption of contaminated meat is common.

Extraparenchymal NCC can appear in the ventricles or subarachnoid spaces, sometimes presenting as a cluster of cysts known as the racemose form. This condition may lead to hydrocephalus, either through mechanical obstruction caused by cysts (as observed in this case) or through an inflammatory response such as ependymitis or arachnoiditis (8). In the diagnosis of NCC, neuroimaging plays a crucial role. CT is often used for initial evaluation, particularly for detecting hydrocephalus, as seen in this case. It also reveals calcifications, a common feature in parenchymal NCC. In addition, MRI protocols need to be optimized to effectively assess subarachnoid cysticercosis. Specifically, employing a heavily T2-weighted, high-resolution steady-state sequence, such as fast imaging employing steady-state acquisition (FIESTA) or 3D CISS, enhances the contrast between CSF and brain tissue, making cysts more visible (5). These cysts are significant for understanding the disease.

In this case, large cysts in the subarachnoid space often develop a multi-chambered shape due to the merging of vesicles and inflamed arachnoid membranes, resulting in an imaging pattern that resembles a “bunch of grapes”, which is strongly indicative of NCC (6). Cerebral hydatid disease is a rare parasitic infestation that presents as well-defined, circumscribed, spherical, non-enhancing intra-axial cystic lesions (9).

Neuroglial cysts typically have a single chamber, resembling CSF in their composition, with smooth and well-defined edges and little to no surrounding abnormalities in signal. Arachnoid cysts are clearly defined, contain only one chamber, and push nearby structures aside, with both CT scans and MRIs showing characteristics similar to CSF in density and signal (4).

Moreover, the high-resolution vessel wall imaging (HR-VWI) technique can detect vascular wall inflammation, which may coexist with leptomeningitis. The combined use of CT and MRI is essential for NCC diagnosis, capable of detecting inflammatory changes, identifying mass lesions, vasculitis, arachnoiditis, and assessing the involvement of the ventricular system (7). Cysts caused by T. solium are known to cause persistent infections that can last for decades in humans. The immune system’s response to T. solium infection is influenced by various factors such as the quantity, position, dimensions, and maturity level of the parasites, as well as host characteristics, which can affect the severity and progression of the disease. These factors dictate the immune response, leading to either pathological manifestations in symptomatic patients or regulation of inflammation in asymptomatic individuals (1).

Analyzing CSF is a crucial tool for evaluating and tracking patients with NCC. A clear link has been found between the presence of circulating parasite antigens and the occurrence of hydrocephalus, indicating that viable parasites or their membranes may be present in the ventricular spaces or subarachnoid areas (8). Studies have also shown a strong association between the total number of lesions detected by MRI and the levels of Taenia antigens in the CSF, as identified using enzyme-linked immunosorbent assay (ELISA) (10).

Cellular reactions in the CSF of individuals with subarachnoid involvement typically reveal mild lymphocytic pleocytosis. Eosinophils are infrequently found, and only a few patients show signs of eosinophilic meningitis. In this instance, the CSF test returned positive for NCC using antigen detection by ELISA, likely due to the presence of parasitic membranes in the basal cisterns (11).

The patient underwent two CSF collections during her treatment: the first before surgery in 2021 and the second for monitoring in 2024. Both collections showed normal glucose, protein, and cellularity levels. Unfortunately, our hospital does not have the capability to collect serology for NCC.

A set of diagnostic guidelines has been established, relying on clinical, imaging, immunological, and epidemiological information, to assist in the diagnosis of individuals suspected of having NCC. These guidelines are divided into four categories: (I) essential criteria (which include histological confirmation of the parasite from a biopsy of brain or spinal cord lesions, detection of cystic lesions showing the scolex in neuroimaging, and direct observation of subretinal parasites through a fundoscopic exam); (II) key criteria (including the presence of lesions strongly indicative of NCC on imaging, a positive serum immunoblot for anticysticercal antibodies, the resolution of intracranial cysts after treatment with albendazole or praziquantel, and spontaneous regression of small, enhancing lesions); (III) supportive criteria (which consist of imaging evidence suggesting NCC, clinical signs consistent with NCC, a positive CSF ELISA for anticysticercal antibodies or cysticercal antigens, and signs of cysticercosis outside the central nervous system); and (IV) epidemiological criteria (including individuals from or living in areas where cysticercosis is prevalent, frequent travel to endemic regions, and evidence of close contact with T. solium infection in the household) (12).

Evaluating these criteria results in two diagnostic classifications: certain and likely, depending on the probability that NCC is present in the patient (11). NCC is a chronic condition with recurrent acute episodes, and the antibodies predominantly belong to the immunoglobulin G (IgG) class. However, modifications can also occur in antibodies of the immunoglobulin M (IgM) class, immunoglobulin A (IgA) class, and immunoglobulin E (IgE) class (13).

Based on clinical symptoms, patients with NCC can be classified as mild, moderate, or severe. Mild symptoms include only headaches, while moderate symptoms involve focal deficits and/or seizures. Severe cases present with intracranial hypertension, characterized by intense headaches, nausea, vomiting, and papilledema. Patients with mild or moderate forms of the disease, such as the patient in this case, typically have specific antibodies against cysticercosis in their serum, along with an increased proliferative response of lymphoid cells when exposed to cysticercosis antigens in laboratory tests. On the other hand, severe NCC is associated with a decreased proliferative response, both specific and nonspecific, in the CSF, along with an increase in the presence of eosinophils and in the concentrations of the proinflammatory cytokines interleukin-6 (IL-6), interleukin-10 (IL-10), and transforming growth factor beta (TGF-β) (14).

Therefore, these parameters facilitate the delineation of distinct risk groups among patients infected with NCC, enabling a more targeted approach to managing disease recurrence. The patient was treated with antiparasitic drugs; however, many controversies about these treatments occur in the literature. There is general agreement that these particular antiparasitic medications are less effective in treating the racemose type (15).

Nevertheless, Mitarnun described a case of racemose NCC in a 68-year-old female patient, who showed clear clinical and imaging improvement following three months of antiparasitic therapy and one month of corticosteroid treatment. To prevent relapse, the antiparasitic treatment was subsequently prolonged for an additional three months (15).

Multiple hypotheses exist regarding this treatment failure, taking into account factors related to both the host and the parasite. It is believed that the effectiveness of cysticidal medications may vary depending on the developmental stage of the parasite. Furthermore, albendazole and praziquantel have limited ability to penetrate the subarachnoid space, in contrast to their action within the brain tissue. As a result, the infection often becomes chronic, with episodes of acute recurrence (15).

Corticosteroids are commonly administered to manage inflammation alongside antiparasitic therapy in cases of parenchymal, ventricular, and subarachnoid involvement. In some cases, corticosteroid use is immediately and dramatically effective (9). In our case, due to hydrocephalus, the placement of a ventricular shunt was indicated, but surgical removal of the cyst was considered not feasible, as it is generally recommended for NCC with racemose cysts, due to the potential cranial nerve and brainstem damage.

Despite its challenges and limitations in removing cysts from the fourth ventricle, basal cisterns, or those firmly attached to neurovascular structures, the minimally invasive technique of neuroendoscopy has proven to be an effective and valuable approach for excising cysts in the lateral and third ventricles (16).

Acknowledgments

None.

Footnote

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-1822/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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