Absence of thallium-201 brain uptake in progressive multifocal leukoencephalopathy in AIDS patients

PML diagnostic criteria: consensus statement from the AAN Neuroinfectious Disease Section

OBJECTIVE

To establish criteria for the diagnosis of progressive multifocal leukoencephalopathy (PML).

METHODS

We reviewed available literature to identify various diagnostic criteria employed. Several search strategies employing the terms "progressive multifocal leukoencephalopathy" with or without "JC virus" were performed with PubMed, SCOPUS, and EMBASE search engines. The articles were reviewed by a committee of individuals with expertise in the disorder in order to determine the most useful applicable criteria.

RESULTS

A consensus statement was developed employing clinical, imaging, pathologic, and virologic evidence in support of the diagnosis of PML. Two separate pathways, histopathologic and clinical, for PML diagnosis are proposed. Diagnostic classification includes certain, probable, possible, and not PML.

CONCLUSION

Definitive diagnosis of PML requires neuropathologic demonstration of the typical histopathologic triad (demyelination, bizarre astrocytes, and enlarged oligodendroglial nuclei) coupled with the techniques to show the presence of JC virus. The presence of clinical and imaging manifestations consistent with the diagnosis and not better explained by other disorders coupled with the demonstration of JC virus by PCR in CSF is also considered diagnostic. Algorithms for establishing the diagnosis have been recommended.

Progressive multifocal leukoencephalopathy: why gray and white matter

Since it was first described in 1958, progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the brain caused by the polyomavirus JC (JCV), has evolved tremendously. It was once considered a noninflammatory disease that affected exclusively oligodendrocytes and astrocytes in the white matter of immunosuppressed individuals and was almost always fatal. Today, we understand that PML can present during the course of an immune reconstitution inflammatory syndrome and that it affects a broader range of individuals, including patients with minimal immunosuppression and those who are treated with novel immunomodulatory medications. Furthermore, JCV-infected glial cells are frequently located at the gray matter-white matter junction or within the gray matter, causing demyelinating lesions within cortical areas. Finally, JCV variants can also infect neurons, leading to the recognition of two distinct clinical entities: JCV granule cell neuronopathy and JCV encephalopathy.

Atypical progressive multifocal leukoencephalopathy in HIV with a high CD4 count: the use of magnetic resonance imaging plus spectrometry studies

Progressive multifocal leukoencephalopathy (PML) is still a underinvestigated central nervous system infection, often linked to HIV-related immunodeficiency. We present an unusual case report characterized by motor involvement, which occurred as the first AIDS-defining event in the absence of appreciable immunodeficiency in a patient with previously undiagnosed HIV infection, who was also assessed by a functional-metabolic magnetic resonance imaging technique (MRI-spectrometry). A 45-year-old patient had HIV infection detected after the appearance of motor abnormalities, in the absence of other signs or symptoms. No significant immunodeficiency was found (initial CD4+ lymphocyte count of 566 cells/µL), and HIV viral load was 24,000 RNA copies/mL. Combination antiretroviral therapy was started with lamivudine, abacavir and lopinavir/ritonavir, with subsequent addition of efavirenz and enfuvirtide. Elevated cerebrospinal fluid levels of JC virus (JCV) (11,668 copies/µL) and consistent neuroradiological findings at contrast-enhanced computed tomography and MRI scans confirmed a diagnosis of PML. Despite the aggressive therapeutic approach, which achieved undetectable HIV viraemia, a CD4+ count above 700 cells/µL and disappearance of JCV after 20 days, the neurological motor involvement rapidly deteriorated, yet associated cognitive impairment never occurred. Clinical and neuroradiological deterioration occurred, and our patient died five months after the diagnosis due to respiratory failure. Combined MRI-spectrometry studies performed 10 days before death included proton ((1)H) spectrometry, and an MRI study-calculation of water diffusion and anisotropy: through this innovative technique combining morphological and metabolic findings, multiple abnormalities involving the subtentorial white matter were detected (with multiple encephalic trunk and ponto-bulbar lesions), which usually are not part of the PML course.

Intra-axial pseudotumors in the central nervous system: clinicopathological analysis

Intra-axial pseudotumors in the central nervous system often mimic malignant brain tumors and cause difficulty in diagnosis and treatment. The present study investigates their radiologic and histological features to elucidate diagnostic clues. Six cases were included in the study, one man and five women, ranging in age from 44 to 87 years (mean age, 61 years). Histologically, three cases had demyelination, and one case each had abscess, angiitis, and non-Langerhans cell histiocytosis. All cases were evaluated radiologically on MRI, most of them by thallim-201 single photon emission tomography ((201)Tl-SPECT). These cases were examined using H&E, special stains, and immunohistochemical studies with a variety of antibodies. MRI demonstrated perifocal edema and ring-like or solid enhancement, mimicking the malignant tumors. Diffusion-weighted MRI showed a hypo-iso-intensity with a hyperintensity on the apparent diffusion coefficient. A (201)Tl-SPECT study revealed no uptake. Although there were various kinds of pathology, inflammatory cells were observed, associated with vascular proliferation and reactive astrocytosis. In addition, some cases showed demyelinating or destructive changes. These results suggested that intra-axial pseudotumors in the central nervous system contain various kinds of pathology, and detailed clinicopathological analysis is important from the point of view of differential diagnosis.

JC virus infection of the brain

Since its initial description, there have been significant changes in the epidemiology, pathogenesis, and clinical and imaging manifestations of JCV infection of brain. The most common clinical manifestation is PML. Other recently described CNS manifestations are JCE, JCVGCN, and JCM. Although AIDS is the most common predisposing factor for JCV reactivation, there is increasing incidence of brain manifestations of JCV reactivation in non-HIV settings, including different rheumatologic, hematologic, and oncologic conditions; monoclonal antibody therapy; transplant recipients; primary immunodeficiency syndromes; and even in patients without any recognizable immune deficiency. IRIS may develop secondary to restoration of immunity in HIV-positive patients with PML receiving antiretroviral therapy. This is of profound clinical significance and needs to be diagnosed promptly. Imaging plays a crucial role in the diagnosis of the disease, monitoring of treatment response, identifying disease progression, and predicting prognosis. In this article, current understanding of the epidemiology, pathogenesis, clinical presentations, and all aspects of imaging of JCV infection of the brain have been comprehensively reviewed.

Imaging manifestations of progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease caused by reactivation of JC virus in immunosuppressed patients. The diagnosis is usually suggested on imaging and confirmed by cerebrospinal fluid polymerase chain reaction (PCR) for JC virus DNA. In this article, we review the imaging manifestations of PML on computed tomography (CT), magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), MR spectroscopy, single photon-emission computed tomography (SPECT) and positron-emission tomography (PET), and outline the role of imaging in follow-up and prognostication.

Reduced value of thallium-201 single-photon emission computed tomography in the management of HIV-related focal brain lesions in the era of highly active antiretroviral therapy

To evaluate the diagnostic value of thallium-201 single-photon emission computed tomography (201Tl SPECT) in the management of focal brain disorders in the era of highly active antiretroviral therapy (HAART), a validation study of diagnostic procedure was performed in a tertiary clinical care center in Italy. Thirty-eight consecutive HIV-infected patients with neurological impairment and focal brain lesions (FBL) were enrolled in a prospective evaluation and underwent diagnostic procedures according to a standardized protocol based on modified previously released guidelines. Six out of seven PCNSL presented high uptake at 201Tl SPECT [sensitivity 86% (95% CI 42-99); specificity 77% (95% CI 58-90); positive predictive value (PPV) 46% (95% CI 20-74); negative predictive value (NPV) 96% (95% CI 78-100)]. Among toxoplasmic encephalitis (TE) cases 14 showed no uptake and 5 showed an increased uptake [sensitivity 74% (95% CI 49-90); specificity 42% (95% CI 21-66); PPV 56% (95% CI 35-75); NPV 61% (95% CI 32-85)]. Patients taking HAART were more likely to display an increased uptake of 201Tl in the cerebral lesions than patients without HAART (OR 5.07; 95% CI 1.19-21.5). Considering only the patients with diagnosis of TE, 60% of patients who showed high radionuclide uptake were taking HAART, while 79% of patients without relevant uptake were not taking HAART. As a result of the impact of HAART, the diagnostic value of 201Tl SPECT in the management of HIV-associated FBL could be substantially reduced. This observation suggests that in HAART-treated patients, this diagnostic tool be used only when combined with other more specific diagnostic markers.

Focal neurological disease in patients with acquired immunodeficiency syndrome

Focal neurological disease in patients with acquired immunodeficiency syndrome may be caused by various opportunistic pathogens and malignancies, including Toxoplasma gondii, progressive multifocal leukoencephalopathy (PML), cytomegalovirus (CMV), and Epstein-Barr virus-related primary central nervous system (CNS) lymphoma. Diagnosis may be difficult, because the findings of lumbar puncture, computed tomography (CT), and magnetic resonance imaging are relatively nonspecific. Newer techniques have led to improved diagnostic accuracy of these conditions. Polymerase chain reaction (PCR) of cerebrospinal fluid specimens is useful for diagnosis of PML, CNS lymphoma, and CMV encephalitis. Recent studies have indicated the diagnostic utility of new neuroimaging techniques, such as single-photon emission CT and positron emission tomography. The combination of PCR and neuroimaging techniques may obviate the need for brain biopsy in selected cases. However, stereotactic brain biopsy, which is associated with relatively low morbidity rates, remains the reference standard for diagnosis. Highly active antiretroviral therapy has improved the prognosis of several focal CNS processes, most notably toxoplasmosis, PML, and CMV encephalitis.