Trypanosoma cruzi Central Nervous System Infection—Pathogenesis, Clinical Manifestations, Diagnosis, and Treatment

Abstract

Purpose of Review

Chagas disease (CD) is a neglected tropical disease from the American continent that commonly causes cardiovascular disease. Some patients develop neurological manifestations. We discuss and summarize the pathogenesis, clinical characteristics, diagnosis, and treatment of the central nervous system manifestations of CD.

Recent Findings

Cerebrospinal fluid quantitative polymerase chain reaction tests and next-generation sequencing in tissue samples have facilitated disease diagnosis and follow-up. Novel presentations, including retinitis, are now reported. A new MRI sign called “Bunch of açai berries appearance”—multiple hypointense nodular lesions—has been described recently. Treatment with benznidazole at higher doses and the role of therapeutic drug monitoring need to be further studied in this setting.

Summary

A high suspicion index is paramount to diagnosing Chagas’ central nervous system involvement. Standardized molecular diagnostics can aid in the initial workup. Future development of new therapeutic drugs is crucial because of the toxicity profile of the currently available medications.

Introduction

Approximately six million individuals are estimated to be affected by Chagas disease (CD) in the Americas. In the USA alone, 288,000 people were estimated to be infected as of 2022 [1]. The global average incidence of the disease is reported to be around 30,000 cases per year, resulting in approximately 12,000 deaths annually. CD is considered endemic in 21 countries across the Americas. Still, due to population mobility, the infection has also spread to regions outside the traditional endemic areas, including Europe, North America, Asia, and Oceania [2, 3]. Central nervous system (CNS) involvement reports are described in patients with acute disease, children, elderly persons, patients living with HIV (PWH), and other immunocompromised hosts [4]. Meningoencephalitis is the primary cerebral manifestation observed in acute CD [5]. Patients with reactivation disease can have cerebral tumor-like lesions called “CNS chago-mas.” During the chronic phase of the disease, ischemic stroke is the primary cerebral manifestation observed [6]; dementia, confusion, chronic encephalopathy, and sensory and motor deficits are less common [7]. We discuss and summarize the pathogenesis, clinical characteristics, diagnosis, and treatment of the central nervous system manifestations of CD.

Pathogenesis

Chagas disease is primarily transmitted through insect vector bites, considered the classic transmission mode. However, other routes exist, including via the placenta, transfusions, transplants, and oral [7]. CNS infection by T. cruzi is commonly observed during the acute phase when parasitemia is at its peak. In animal models, T. cruzi infection in newborn rats has shown the detection of parasites within glial cells, near neuronal somas, capillaries, and venules in the cerebral and cerebellar cortices, as well as the thalamic subcortical nucleus during the peak of parasitemia [8]. This localization suggests a potential invasion of the brain parenchyma through the blood-brain barrier vessels [9]. However, parasites and inflammatory changes are evident in the basal ganglia when parasitemia is no longer detectable [10]. Encephalitis typically occurs during the acute phase and coincides with the abundant presence of trypomastigotes in the cerebrospinal fluid (CSF) [11].

Experimental acute and chronic T. cruzi infections have revealed the presence of inflammatory infiltrates in various areas of the blood-cerebrospinal fluid barrier, such as the choroid plexus and hippocampus [12, 13]. Additionally, amastigote nests have been observed in the cerebellar neuropil region [13] and below the pia mater in the ependymal cells that form the glia limitans at the brain surfaces [14]. These suggest that T. cruzi can cross the endothelium of leptomeningeal venules in the subarachnoid space, traverse the pia mater, reach the glia limitans, and access the brain parenchyma. The infection of the glia limitans may explain the cerebellar T. cruzi infection, as there is a neural connection between the glia and the cerebellum [8, 10]. Other less frequently infected regions include the hippocampus and areas without a blood-brain barrier, such as the choroid plexus [15].

The interaction between the parasite-derived trans-sialidase (TS) and tyrosine-protein kinase receptors (TrkA and TrkC), commonly upregulated during CNS injury and infections, may promote parasite replication and tissue damage [15, 16]. These interactions facilitate parasite adherence and efficient invasion of neuronal, epithelial, and phagocytic cells both in vitro and in vivo [17] while also activating mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase/Akt signaling pathways, as observed in infected PC12 cell lines, a well-established model of neuronal differentiation [7, 18]. Muscarinic cholinergic pathways have also been implicated in immune-mediated cell invasion in mouse models [19].

The invasion of T. cruzi promotes the release of pro-inflammatory cytokines systemically and within the CNS. Experimental evidence from in vitro and in vivo studies has shown that glial cells expressing interferon-γ (IFN-γ) and elevated levels of tumor necrosis factor-α (TNF-α) are associated with astrocyte invasion [20, 21], In murine models of acute T. cruzi infection, plasma TNF-α levels and CNS TNF messenger ribonucleic acid (mRNA) expression have been observed, along with higher parasitemia and mortality rates in orally infected mice [22]. Additionally, parasite infection induces astrocytes to adopt a pro-inflammatory profile characterized by enhanced production of interleukin 6 (IL-6) and TNF-α, as well as increased tumor necrosis factor receptor 1 (TNFR1) expression, thereby creating a self-sustaining inflammatory loop that promotes parasitic replication [21].

A parasite-derived enzyme, cruzipain, cleaves plasma kininogens into bradykinin, activating endothelial brad-ykinin-B2 receptors and the protein-G immune pathway [23]. Furthermore, in vitro studies suggest that T. cruzi may migrate through brain endothelial cells paracellularly without disrupting the cell monolayer, possibly mediated by bradykinin and the chemokine (C-C motif) ligand 2 (CCL2) gradient [24].

CNS Chagas disease can be attributed to direct parasite invasion or indirect effects of local and systemic inflammation in response to the infection [19]. Meningoencephalitis, a manifestation of CNS CD, is characterized by T. cruzi nests, which are inflammatory nodules primarily composed of parasites, mononuclear cells, and glial cells within the brain [20]. Amastigote nests can be observed in the neuropil of cerebellar gray matter nuclei even without detectable inflammatory processes [22], T. cruzi has been detected in the hypothalamus and pituitary gland following infection, and several alterations and injuries in the hypothalamic-pituitary-adrenal (HPA) axis have been reported [7, 13, 25].

Experimental studies have demonstrated that T. cruzi can infect microglia, macrophages, and astrocytes [24, 25]. Histological examinations and in vitro evidence have shown a high frequency of parasite nests without surrounding membranes in non-glial cells, as well as the presence of parasites in astrocyte processes among Purkinje cell bodies in the cerebellum [8, 21].

Histological examinations of T. cruzi–infected rodents have revealed damage in various regions of the CNS, characterized by neuronal loss, the formation of glial nodules due to astrocyte proliferation, edema, and enlargement of perivascular spaces. These alterations are accompanied by the presence of mononuclear cellular infiltrates both around blood vessels and within the parenchyma [25]. Astrocytes appear to have limited control over T. cruzi infection compared to microglial cells, as they secrete interleukin-1β (IL-1β), and nitric oxide (NO), which may render them more susceptible to parasite replication [26]. Furthermore, astrocytic processes surrounding CNS blood vessels may serve as a potential route for parasite invasion, particularly in the gray matter where capillary density is higher than in the white matter [27, 28].

In experimental models, mice acutely infected with T. cruzi exhibit elevated cerebral oxidative stress and micro-circulatory changes, including endothelial dysfunction, increased leukocyte rolling and adhesion, vascular obstruction, and reduced functional capillary density [27]. Ischemic strokes have been found to induce the production of reactive oxygen species (ROS), triggering the coagulation cascade and activating complement, platelets, and endothelial cells. Additionally, an increase in adhesion molecules, IFN-γ, TNF-α, and inducible nitric oxide synthase (iNOS) is observed, leading to vessel constriction and increased vulnerability to ischemia in the brain [28].

Chronic CD patients can experience depressive behavior, possibly associated with oxidative stress and heightened pro-inflammatory cytokines [29], Depressive behavior in murine models can be induced by pro-inflammatory cytokines and pathogen-associated molecular patterns, such as lipopolysac-charide (LPS) and polyinosinic:polycytidylic acid (poli:IC) [30]. During CNS infection by T. cruzi, TNF-α, IL-1β, and NO are released by macrophages, microglia, and astrocytes and are believed to contribute to the neurological alterations observed in CD [31, 32].

Furthermore, cognitive deficits can occur in chronically T. crazi–infected mice without neuroinflammation. These cognitive alterations have been associated with the persistence of T. cruzi and increased lipid peroxidation in the hippocampus and cortex of the CNS [33].

Another theory that needs to be further studied is molecular mimicry as a mechanism of pathogenesis of CNS CD. A human antibody against T. cruzi tubulin has been demonstrated to cross-react with a human neural protein of the central and peripheral nervous system [34].

Risk Factors

In countries endemic to CD, such as Argentina, Brazil, and Bolivia, the prevalence of T. cruzi coinfection PWH ranges from 1 to 32% [35–38]. Due to their compromised cellular immunity, untreated PWH have an increased risk of T. cruzi reactivation. Reactivation commonly manifests as CNS involvement [39–41] and, if left untreated, carries a high mortality rate (79–100%) [42, 43]. The reactivation in such cases is associated with brain tissue damage linked to increased IL-17 expression and low peripheral blood CD4 T cell counts [4, 44]. Also, reactivation of CD is associated with increases in HIV RNA load [45]. Recipients of solid organ transplants are also susceptible to T. cruzi reactivation [46]. CNS reactivation has been observed in renal transplantation [47, 48], heart transplantation [49–51], as well as in patients with leukemia [52] and after stem cell transplantation [53]. A rare case of CNS Chagas due to reactivation disease was reported in a patient without identifiable immunosuppression [54].

Clinical Manifestations

Chagas disease presents a wide array of clinical syndromes divided into two phases: acute and chronic. Chronic can be subdivided into an indeterminate and a determinate form. During the chronic phase, reactivation can occur [55, 56]. The development and severity of each phase and form largely depend on the interplay between the parasitic virulence, the transmission route, and the host’s immunity [57].

Primary Lesion

The primary lesion is an inflammatory-erythematous macule called inoculation “chagoma” [58]. It can be up to 10 cm in diameter and correlates with the entry site of the trypomastigote through the skin [58]. It occurs in less than half of patients bitten by a triatomine bug [59]. Alternatively, suppose the route of inoculation is through the conjunctiva. In that case, the primary lesion will present as a unilateral violaceous palpebral edema with painless conjunctivitis and cervical lymphadenopathy, known as Romana’s sign—which may last up to 2 months [60].

Acute Chagas

The acute phase follows the appearance of the primary lesion by about 14 days and lasts up to 30–60 days approximately [61]. When present, the clinical course consists of unexplained high and prolonged fever, myalgia, malaise, headache, lymphadenopathy, hepatosplenomegaly, or anasarca [57, 62]—yet the vast majority of cases (65–99%) present with few or no symptoms at all [62]. Facial edema, gingivitis, and dry cough have been reported due to the penetration of the parasite through the oral cavity, lips, or pharyngeal mucosa [63]. Rarely (fewer than 1% of cases) can it be associated with potentially fatal complications such as acute myocarditis, pericardial effusion, encephalitis, or meningoencephalitis [4, 64]. Because this phase is due to circulation and intense tissue parasitism, it can be vertically transmitted to the offspring in gravid patients [65, 66]. Those with CD acquired orally, through blood transfusion or organ transplantation, are at higher risk of complications during the acute phase [67].

Chronic Chagas

Following the mostly asymptomatic or oligosymptomatic acute phase of CD—in which only a few are treated—the infection progresses to a chronic phase [68]. About 60–90% of cases will be diagnosed in the indeterminate form, in which patients are serologically positive but asymptomatic [68]. Nearly 2% of patients will develop cardiomyopathy after the initial asymptomatic chronic indeterminate form [68, 69], In the former, destruction of the cardiac conduction system and myocardium by tissue amastigotes may present as a clinical spectrum, including conduction abnormalities (e.g., right bundle branch block, left anterior hemiblock, atrioventricular block, or ventricular arrhythmias), apical aneurysms, thromboembolism, and dilated cardiomyopathy [67, 70]. In the chronic digestive form, the loss of ganglion cells in the myenteric plexus results in dysphagia, regurgitation, retrosternal chest pain, odynophagia, constipation, changes in bowel habits, rectal straining, and tenesmus that correlates with esophageal and colonic dilation, respectively [71].

Reactivation of Chagas

Reactivation of CD occurs when the immunity of a chronically infected host is suppressed and causes the reappearance of acute symptoms [72]. It is diagnosed by detecting T. cruzi in tissue or body fluids (e.g., blood, CSF, ascitic fluid, pericardial fluid) with or without clinical symptoms. Even though reactivation is rare, mortality is estimated to be above 70% [7, 71]. When present in PWH, it commonly affects the central nervous system (75–90%) as meningoencephalitis or CNS Chagoma [48, 68, 73]. Cardiac involvement in PWH is the second most common form of reactivation. It presents with rapid progression of chronic cardiomyopathy, new-onset arrhythmias, pericardial effusion, and acute myocarditis [51, 68]. Neurologic and cardiac complications occur concurrently in about 10% of cases [62, 71, 73]. Rarely, CD reactivates in the form of spontaneous peritonitis, ocular myositis, and erythema nodosum, among others [74].

Reactivation of CD is more commonly associated with AIDS (75–80%) and is considered an AIDS-defining illness in endemic areas [54, 68]. However, other causes of immunosuppression, such as hematologic malignancies, prolonged corticosteroid use, hematologic or solid organ transplant, chemotherapy recipients, or pregnancy, have also been described as causes of reactivation [72, 75–77].

Neurologic Complications of Chagas Disease

T. cruzi can affect the central, peripheral, and autonomic nervous system, and a clinical spectrum of neurologic complications has been described in all phases and forms of the disease that may range from asymptomatic infection to long-term disability and death. Clinical presentation and risk factors are displayed in Table 1.

Table 1.

Clinical presentation and risk factors for neurologic disease in American trypanosomiasis

Neurologic syndrome	Clinical features	Phase of disease	Risk factors and other considerations
Central nervous system
Chagasic meningoencephalitis	Asymptomatic, fever, headaches, vomiting, altered mental status, seizures, ataxia or another focal neurologic deficit, coma.	Acute phase	Infants <2 years of age, immunosuppression*, risk of transmission to offspring in pregnancy
		Reactivation phase	Immunosuppression*
CNS Chagoma	Asymptomatic, focal neurologic deficit, fever, headache, vomiting, seizures, altered mental status, ataxia, coma.	Reactivation	Immunosuppression*
Stroke	Asymptomatic (silent microemboli), focal neurologic deficit (more commonly MCA syndrome), altered mental status, seizures at stroke onset.	Chronic	Chagasic cardiomyopathy
Neurocognitive impairment and psychiatric disease	Possible neurocognitive decline, anxiety, and depression.	Chronic	Unknown
Retinitis	Blurry vision and eye pain	Reactivation	Immunosuppression*
Peripheral nervous system
Peripheral neuropathy	Sensory-motor peripheral neuropathy.	Chronic	Therapy with benznidazole or nifurtimox
Autonomic neuropathy and gastrointestinal dysfunction	Megaesophagus: dysphagia, regurgitation, retrosternal chest pain, and odynophagia. Megacolon: constipation, changes in bowel habits, rectal straining, and tenesmus	Chronic	Southern Cone in South America

^*Acquired immunodeficiency syndrome (AIDS), hematologic malignancies, chemotherapy, prolonged/high-dose corticosteroids, hematologic or solid organ transplant recipients, or pregnancy

Central Nervous System Involvement

Chagasic Meningoencephalitis

It can present with encephalitis or meningoencephalitis [78]. Rarely does it occur during the acute phase (5–10% of cases) [62, 71, 78], yet when it does, it typically involves children under 2 years of age (including congenital disease), followed by immunocompromised and elderly individuals.

During the acute phase, chagasic encephalitis is invariably associated with myocarditis [62, 71, 79]. In contrast, reactivation of CD occurs almost universally under various forms of immunosuppression—particularly AIDS [79]—and can be the first opportunistic infection in AIDS [80]. It is relevant to mention that neurological manifestations are less common in transplant patients than in AIDS [81]. A series of chagasic patients with CNS disease CD4 counts ranged between 63 and 126 cells/m³, associated with exceptionally high mortality [79, 81]. During the reactivation of CD, myocarditis may or may not be present [79, 82]. Clinical presentation in both the acute phase and during reactivation is a clinical spectrum that ranges from asymptomatic parasitorraquia or mild alteration in mental status to headaches, lethargy, mood changes, focal neurologic deficit, seizures, stupor, coma, and death [82–84]. The main differential diagnosis here is toxoplasma encephalitis

Cerebral Tumor-like American Trypanosomiasis or CNS Chagoma

During the reactivation, another common presentation of CD is a space-occupying lesion in the CNS (brain, cerebellum, or spinal cord). It presents as ring-enhancing single or multiple lesions in the supratentorial white matter, yet masses have been reported everywhere in the CNS [83–85]. Like chagasic meningoencephalitis, CNS Chagoma disproportionately presents among those with suppressed immune systems, especially AIDS [39, 47, 50, 52, 86, 87]. It is clinically and radiologically indistinguishable from other opportunistic CNS masses due to infectious and non-infectious causes [71, 86]. As in chagasic meningoencephalitis, brain chagoma must be included in the differential of intracranial lesions in an immunocompromised patient when coming from an endemic area, particularly when lesions fail to respond to therapy against Toxoplasma spp. [71, 88]. Following the resolution of the infection, patients may have residual hemiparesis [62, 79]. Infrequently, CNS Chagoma can be an expression in the acute phase of the disease [5, 86]. The prognosis is generally poor [89–91], reaching nearly 100% mortality in untreated patients.

Ischemic Stroke

CD is an independent risk factor for ischemic stroke [28]. Chagas-related strokes are rare (1–3% of patients), yet they account for 10–52% of Chagas-related deaths [5, 92]. A recent US-based study found an annual rate of stroke risk of 0.8% [92], lower than those in endemic countries, 1.4% [93]. Annual stroke mortality in Chronic Chagas Cardiomyopathy reaches 0.4% [94]. The mechanism by which they occur in approximately half of the cases is through cardioembolism in individuals with underlying cardiomyopathy [5, 95].

The risk factors for cerebral infarcts include cardiac arrhythmias, apical aneurysms, parietal thrombosis, mural thrombosis, female gender, arterial hypertension, and left ventricular dysfunctions [5, 96]. However, stroke may affect patients with no cardiomyopathy [97].

Other secondary mechanisms related to microvascular changes (e.g., endothelial dysfunction, atherosclerosis, and autoimmunity) account for the remaining cases without heart disease [98, 99]. In Chagas-related stroke, the MCA territory is the most frequent site for embolism in 71–87% of cases, although patients can present with cerebral infarcts to virtually any structure [99, 100]. Recurrence is common, as 20% of chagasic patients with cerebral infarcts have a history of previous stroke [100].

Neurocognitive and Psychiatric Disease

There is limited data on cognitive function in CD, and data is conflicting. A study in 1994 by Mangone et al. reported that individuals with T. cruzi infection score lower Mini Mental Status Examination (MMSE) compared to those without it, perhaps mediated by the development of cardiomyopathy, treatment regimen, chronic inflammation, or trypanosome-induced immune dysregulation—yet a definitive causal relationship has not been established [101, 102]. Additionally, these findings have not been reproducible, as even patients with white matter lesions with CD have shown no cognitive dysfunction in retrospective analyses [5, 62, 64, 103]. Alteration in behavior and the sleep-wake cycle has been reported among rodents infected with T. cruzi but not in humans [104]. Psychiatric illness has been suggested following CD, but there is no formal causal relationship [29, 101]. Electroencephalogram changes are unspecific in chronic CD [105].

Other

Retinitis was reported in a patient with autologous hematopoietic stem cell transplantation, with sudden onset blurred vision and pain in his left eye. The diagnosis was made through pan-organism PCR (16S, ITS, and 28S) of riboso-mal DNA in the vitreous biopsy [106••]. His serology and blood PCR were positive for T. cruzi. In animal models, the cornea has been suggested as a parasite reservoir [107].

Peripheral and Autonomic Nervous System Involvement

Autonomic Neuropathy and Gastrointestinal Involvement

Destruction of the esophageal and colonic myenteric plexus is responsible for the digestive disorders associated with CD [108]. The mechanism is due to the denervation of ganglion cells and autonomic dysregulation, probably from amastigote invasion and trypanosome-induced immune imbalance, that results in reduced peristalsis and sphincter dysfunction [109], and thus the organs suffer severe dilation [110]. In patients with cardiomyopathy, parasympathetic dysregulation has been proposed as a mechanism for developing cardiac arrhythmias, yet these findings have not been reproducible [83, 109]. Gastrointestinal involvement is less common than heart disease and is seen mainly in patients from the Southern Cone of South America [111]. Lower urinary tract dysfunction can also be seen in patients with CD [112].

Peripheral Neuropathy

Chagas-related polyneuropathy is rare (up to 10% of cases), and the mechanism is not well-understood. It can be due to the disease itself (chronic phase sensory-motor neuritis) or due may occur as a side effect from antiprotozoal therapy (benznidazole or nifurtimox) at any point of the disease treatment [4, 5, 68, 113].

Diagnostic Methods

A high index of suspicion is critical for diagnosing CNS CD in patients with risk factors (e.g., country of origin, country of residence, travel history, immunosuppression, mother’s country of origin).

The diagnosis of central nervous system CD can be made through the direct detection of the parasite in the CSF [84, 114], the presence of amastigotes in histopathology [83, 114], CSF parasitic culture (Novy-MacNeal-Nicolle Parasitic Medium, can take 2 to 4 weeks) [115, 116], molecular techniques in CSF, tissue, and preservation fluid [117–119]. In addition, serum serologic studies with the appropriate clinical picture [85, 120], circulating trypomastigotes in peripheral blood through the Strouth method in patients with neurological manifestations [118], or rising parasite numbers by quantitative PCR in peripheral blood in patients with CNS signs and symptoms should raise the possibility of CNS CD. The CSF profile may be normal or associated with lymphocyte pleocytosis, hyper-proteinorraquia, and low glucose [113].

Direct Visualization

The CSF sample should be evaluated for the presence of trypomastigotes with the use of Giemsa stain; centrifugation enhances the sensitivity of the test (10 min, 3000 rpm) (Fig. 1) [121, 122]. In a case series that included 15 people coinfected with HIV and T. cruzi with clinical meningoencephalitis, trypomastigotes were visualized in the CSF in 85% of cases [123, 124].

Fig. 1.

Giemsa stain (100×) of CSF fluid displaying a T. cruzi try-pomastigote (arrow)

Molecular Methods

Quantitative PCR (qPCR) against T cruzi satellite DNA can be used in the CSF and peripheral blood to diagnose CD. These techniques present high sensitivity for DNA parasite detection during reactivation and chronic-phase patients; in addition to that, their use can be applied to monitor response to therapy [118]. Quantitative PCR can simultaneously be applied to tissue samples and the preservation fluid (PF) of the samples [117, 123]. Paraffin-embedded samples can be deparaffinized for PCR testing [119, 125]. It is relevant to mention that a negative PCR in the tissue does not rule out CD [125]. Another technique that can be used in brain tissue samples is next-generation sequencing of 28S rRNA gene. The advantage of this technique is the ability to identify one of many potential pathogens with a single test, which is ideal when evaluating immunocompromised individuals that could have multiple pathogens [119, 126]. Cell-free DNA (cfDNA) detection in blood has been used to diagnose Chagas reactivation and acute disease, although no cases of CNS Chagas have been described using this technology [127, 128].

Histopathology

Amastigotes can be seen in the samples of brain biopsies with the presence of amastigotes in histopathologic studies with H&E and electron microscopy. Trypomastigotes can be seen in the leptomeninges. T. cruzi amastigotes in electron microscopy are characterized by a pseudo-flagellum and a prominent kinetoplast (0.5 μm).

T. cruzi trypomastigotes are characterized by an S-shape, a prominent terminal kinetoplast at the pointed posterior end, and a free flagellum at the anterior end [122]. In the acute form, encephalitis is characterized macroscopically with edema, congestion, and petechial hemorrhages or without major changes. Microscopically is multifocal encephalitis with nodules consisting of microglia, macrophages, astrocytes with amastigotes nests or amastigotes in the center of the nodules, and perivascular lymphocytic infiltrate. This is accompanied by lymphomonocytic meningitis [123••]. In some patients, these changes can regress.

In reactivation, the nodular lesions can be seen with a necrotized center surrounded by a white halo, congested leptomeninges, and purulent exudate [124]. In the microscope, areas of well-circumscribed necrosis with perilesional inflammatory component and multiple areas of gliomesen-chymal cell clusters containing T.cruzi in macrophages and glial cells, and neurons with acute degeneration, are seen in the white matter and the cortex. Perivascular lymphocytic infiltrates with hemorrhages, mixed glial proliferation, and white matter macrophage infiltration are noted [125]. It is important to mention that amastigotes are not seen within nerve cells [126]

Serology

Serologic studies based on enzyme-linked immunoabsorbent assay (ELISA) and immunofluorescent antibody detection (IFA) for whole parasite lysate and recombinant antigens are the diagnostic method of choice for chronic CD. However, it is not specific for CNS Chagas disease, and individual assays lack sensitivity and specificity. Therefore, two serologic studies based on different techniques or antigens are necessary for the diagnosis [129]. Another limitation is the variability of these assays based on geographical location [130, 131]. Similar to other neurological infections with a reactivation, positive serology is suggestive. Still, its absence cannot rule out infection as patients may not mount a sufficient humoral response to seroconvert [129].

Imaging

Computer tomography (CT) and magnetic resonance (MR) can characterize CD CNS involvement.

In MR, chagomas can present as single or multiple, ring-enhancing or non-enhancing, with or without mass-effect lesions involving numerous areas of the brain (usually supratentorial), cerebellum, and spinal cord which can be seen, similar to the ones noted in patients with toxoplasmosis and CNS lymphoma [85, 114, 132]. These lesions on T1-WI are usually hypointense. On T2-WI and FLAIR, the lesions have variable signal intensity [132]. MR of chagasic encephalitis may show scattered T2-hypertense lesions, predominantly in the supratentorial white matter [133]. Another finding seen is diffuse brain atrophy [133]. In a recent case series of four patients, focal cerebral lesions with hypointensity on T2-WI were described as “bunch of açai berries appearance.” In the post-gadolinium T1-WI, punctate enhancement is seen. Açai is a fruit involved in the oral transmission of T. cruzi [134••].

Treatment

Benznidazole and nifurtimox are the current treatment for CD. Due to the side effect profile, benznidazole is preferred. Both drugs are US Food and Drug Administration (FDA)–approved only for children. Treatment of CNS Chagas reactivation in PWH and transplant recipients involves benznidazole at a dosage of 5 mg per kilogram daily, divided into two doses, for a duration of 60 days, which can be extended to 90 days in some instances. An alternative treatment option is nifurtimox, administered at 10 mg per kilogram daily, divided into three doses, for 90 days [40, 81, 113]. In the case of transplant recipients, multiple treatments may be necessary for more than one episode of Chagas reactivation [135]. If benznidazole cannot be tolerated, the patients are changed to nifurtimox [136].

A study measuring the concentrations of benznidazole in the CSF of 6 PWH with meningoencephalitis due to CD noted that only 3 patients had detectable drug levels in the CSF, all under 1 μg/ml suggesting that the usual benznidazole doses may be suboptimal in HIV-positive patients with T. cruzi meningoencephalitis and highlighting the potential for therapeutic drug monitoring (TDM) in CD with CNS manifestations [136]. A good example is a case report of a renal transplant with CNS Chagas, where the dose was increased from 5 mg/kg/day for 60 days to 15mg/kg/day for 90 days with periodic TDM in blood and CSF, with positive results. Regarding secondary prophylaxis, there is a case report that used benznidazole 5mg/kg three times per week in a PWH for 2 years until immune reconstitution [113], although there is no standardized prophylaxis duration. Nifurtimox has also been proven to penetrate the CNS [136, 137]. In PWH, antiretroviral therapy must be initiated promptly, although no ideal time has been described or recommended [132]. The potential emergence of immune reconstitution inflammatory syndrome (IRIS) poses a significant concern, particularly among PWH with CNS lesions receiving antiretroviral therapy (ART). However, the documentation of IRIS cases specifically associated with CNS Chagas disease after initiating ART remains limited and controversial [43, 87]. In one reported case, a patient developed erythema nodosum following the initiation of ART [138]. In a study involving 235 HIV patients in Buenos Aires, one individual developed a chagoma after starting ART, which was attributed to IRIS [139]. Coinfection is not considered a contraindication for initiating ART [43].

There is no standard for primary prophylaxis for CD in HIV patients. Some experts recommend treating with benznidazole or nifurtimox in PWH with two T. cruzi positive serologic testing and without Chagas cardiomyopathy [121, 140]. In the case of transplant patients, the Brazilian government recommends prophylactic treatment of liver transplant patients with donors positive for T. cruzi [141]. In the USA, qPCR in peripheral blood and blood smears are done in recipients positive for T. cruzi and recipients of organ donors positive for T. cruzi to determine preemptive anti-trypanosomal therapy [81]. The acute phase treatment of ischemic stroke in chagasic patients does not differ from other stroke etiologies. Successful thrombolytic therapy has been reported in these patients [5, 142], but long-term sequelae may persist depending on the extent of structural damage.

For the follow-up of these patients, the clinical evolution, together with periodic qPCR of the CSF and peripheral blood combined with imaging, is useful [40, 113, 116, 122]. However, other approaches are being developed, like loop-mediated isothermal amplification of Trypanosoma cruzi DNA for point-of-care follow-up in blood and CSF samples [143].

Conclusions

We should try to elucidate the immunologic effector mechanisms responsible for reactivation in cases of HIV–T. cruzi coinfection or immunosuppressed transplant patients. There is a need to standardize molecular methods to diagnose this condition. Further investigation of NGS as a diagnostic tool may prove helpful in the clinical management of this disease. CNS benznidazole pharmacokinetics studies could contribute to the consensus for an ideal dose schedule in CNS Chagas. Globalization, migration, and global warming will continue to change the epidemiology of this disease. Early recognition, prevention efforts, and screening [144] are pivotal to preventing Chagas-related neurological complications.

Data Availability

All articles used for this study are publicly available in PubMed.