Diagnostic accuracy of HIV-associated central nervous system toxoplasmosis

Epidemiology, Pathophysiology, Diagnosis, and Management of Cerebral Toxoplasmosis

Toxoplasma gondii is known to infect a considerable number of mammalian and avian species and a substantial proportion of the world's human population. The parasite has an impressive ability to disseminate within the host's body and employs various tactics to overcome the highly regulatory blood-brain barrier and reside in the brain. In healthy individuals, T. gondii infection is largely tolerated without any obvious ill effects. However, primary infection in immunosuppressed patients can result in acute cerebral or systemic disease, and reactivation of latent tissue cysts can lead to a deadly outcome. It is imperative that treatment of life-threatening toxoplasmic encephalitis is timely and effective. Several therapeutic and prophylactic regimens have been used in clinical practice. Current approaches can control infection caused by the invasive and highly proliferative tachyzoites but cannot eliminate the dormant tissue cysts. Adverse events and other limitations are associated with the standard pyrimethamine-based therapy, and effective vaccines are unavailable. In this review, the epidemiology, economic impact, pathophysiology, diagnosis, and management of cerebral toxoplasmosis are discussed, and critical areas for future research are highlighted.

HIV-associated opportunistic CNS infections: pathophysiology, diagnosis and treatment

Nearly 30 years after the advent of antiretroviral therapy (ART), CNS opportunistic infections remain a major cause of morbidity and mortality in HIV-positive individuals. Unknown HIV-positive disease status, antiretroviral drug resistance, poor drug compliance, and recreational drug abuse are factors that continue to influence the morbidity and mortality of infections. The clinical and radiographic pattern of CNS opportunistic infections is unique in the setting of HIV infection: opportunistic infections in HIV-positive patients often have characteristic clinical and radiological presentations that can differ from the presentation of opportunistic infections in immunocompetent patients and are often sufficient to establish the diagnosis. ART in the setting of these opportunistic infections can lead to a paradoxical worsening caused by an immune reconstitution inflammatory syndrome (IRIS). In this Review, we discuss several of the most common CNS opportunistic infections: cerebral toxoplasmosis, progressive multifocal leukoencephalopathy (PML), tuberculous meningitis, cryptococcal meningitis and cytomegalovirus infection, with an emphasis on clinical pearls, pathological findings, MRI findings and treatment. Moreover, we discuss the risk factors, pathophysiology and management of IRIS. We also summarize the challenges that remain in management of CNS opportunistic infections, which includes the lack of phase II and III clinical trials, absence of antimicrobials for infections such as PML, and controversy regarding the use of corticosteroids for treatment of IRIS.

Central nervous system infection with Toxoplasma gondii

Central nervous system infection by Toxoplasma gondii, or Toxoplasma encephalitis, is the most common cause of brain mass lesions in human immunodeficiency virus (HIV)-infected patients. It usually presents as one or more brain abscesses, but it can also cause a diffuse encephalitis or ventriculitis. Individuals who are Toxoplasma immunoglobulin G-seropositive, who have peripheral blood CD4+ T-cell concentrations below 200/μL, are not on antiretroviral therapy, and are not taking trimethoprim-sulfamethoxazole to prevent Pneumocystis pneumonia, are at particular risk for Toxoplasma encephalitis. Neuroimaging typically shows round, isodense or hyperdense lesions in the hemispheric gray-white junction, deep white matter, or basal ganglia that enhance with contrast in a ring, nodular, or homogeneous pattern. In appropriate patients, response to an empiric treatment trial can establish the diagnosis. Immune reconstitution inflammatory syndrome is uncommon in HIV-infected patients treated for Toxoplasma encephalitis and combination antiretroviral therapy is an integral part of toxoplasmosis treatment.