BACKGROUND: Epidemiological studies on predisposing conditions and outcomes of progressive multifocal leukoencephalopathy (PML) cases have been carried out exclusively in high-income countries. We aim to report and compare the main characteristics and outcomes of patients with PML and several underlying diseases in a referral center in a middle-income country.
METHODS: We performed a retrospective cohort study of PML cases admitted to a tertiary care hospital in São Paulo, Brazil during 2000-2022. Demographic and PML-specific variables were recorded. One-year case-fatality rate and factors associated with death were identified using a multivariate Cox proportional hazards regression model.
RESULTS: Ninety-nine patients with PML were included. HIV infection (84.8%) and malignancy (14.1%) were the most prevalent underlying conditions. Other predisposing diseases were autoimmune/inflammatory diseases (5.1%) and solid organ transplantation (1.0%). One (1.0%) patient had liver cirrhosis and another (1.0%) patient was previously healthy. Focal motor deficits (64.2%) and gait instability (55.1%) were the most common signs. The one-year case-fatality rate was 52.5% (95% CI 42.2-62.7). The one-year case-fatality rate (95% CI) in patients with or without malignancy (85.7%, 95% CI 57.2-98.2% and 47.1%, 95% CI 36.1-58.2%, respectively) were statistically different (P = 0.009). Crude and adjusted Cox regression models identified malignancy as independently associated with death (adjusted HR = 3.92, 95% CI 1.76-8.73, P = 0.001).
CONCLUSIONS: HIV/AIDS was the predisposing condition in 84.8% of PML cases. The one-year case-fatality rate was 52.5% and having a malignancy was independently associated with death. This study reports emerging data on the epidemiology and outcome of PML in a middle-income country.

OBJECTIVE: The use of natalizumab (NAT) in multiple sclerosis (MS) may be complicated by progressive multifocal leukoencephalopathy (PML), a rare and life-threatening opportunistic brain infection. We aimed to analyze the course of MS after PML recovery together with the long-term outcome of NAT-associated PML (NAT-PML) in Austria.
METHODS: Retrospective study based on identification of cases in the nationwide Austrian MS treatment registry (AMSTR) and MS centers with review of patient records. The expanded disability status scale (EDSS) was used to measure neurological disability and outcome.
RESULTS: As of December 2022, we identified 15 NAT-PML cases in Austria; only 20% occurred after 2016, when increased vigilance commenced. Two patients did not survive acute PML, and an additional patient died five years later, yielding a mortality rate of 20%. Seizures occurred exclusively in patients with pronounced EDSS increase. Gadolinium (Gd)-enhancement on brain magnetic resonance imaging (MRI) on PML suspicion was associated with minor changes of post-PML neurological disability. Long-term follow-up of up to 132 months (median 76 months) was available in 11/15. The overall median EDSS increased from 3.5 at pre-PML to 6.5 at the last assessment. Regarding inflammatory MS-related disease activity during the observation period, one single individual experienced an MS relapse and another patient had two Gd-enhancing brain lesions. Three patients converted to progressive MS within three years from PML and the EDSS further increased in 6/11.
CONCLUSIONS: The number of NAT-PML cases is decreasing over time. While many patients accumulated severe persistent neurological deficits compared to pre-PML, inflammatory MS-related disease activity after PML recovery was rare.

Our study aims to report on the demographic, incidence rate (IR), clinical, and microbiological characteristics of PML patients diagnosed in our tertiary-care hospital over the past 12 years. In this retrospective observational study, we reviewed all requests for JCPyV PCR in CSF from patients with suspected PML. We collected demographic, clinical, and microbiological data of patients diagnosed with PML. Since 2018, real-time quantitative PCR has been used, whereas prior to 2018, samples were sent to our National Reference Center for qualitative diagnosis. Thirteen patients were diagnosed with PML, with 10 of them having a definitive diagnosis and 3 classified as a possible diagnosis with negative PCR results. Eleven patients had advanced HIV, one had non-Hodgkin\'s lymphoma, and one had systemic lupus erythematosus. Most of the white matter lesions were located at the cerebral level, although the parenchyma and cerebellum were also affected. The most frequent symptoms were behavioral disorders and hemiparesis. The viral load of JCPyV in cerebrospinal fluid was < 1000 copies/mL in three patients. Six patients received compassionate treatment, and all six patients with definitive PML diagnosis died. Although advanced HIV patients were the most affected by PML in our study, it should also be considered in patients with other underlying diseases. While current PCR tests offer high sensitivity and specificity, false negatives can occur. The prognosis of the disease remains poor, and early multidisciplinary diagnosis-including clinical, microbiological, and neuroimaging assessments-remains crucial for improving neurological damage and prognosis.

UNASSIGNED: Progressive multifocal leukoencephalopathy (PML) is a viral infection affecting the central nervous system (CNS) seen mostly in advanced human immunodeficiency virus (HIV) infection. There is limited data on the epidemiology and disease course of these patients from India. This study was aimed to determine the frequency of PML in patients with HIV/acquired immunodeficiency syndrome (AIDS) and the clinical presentation and prognosis of these patients.
UNASSIGNED: The study was conducted at a tertiary care HIV center in New Delhi. Data of 765 patients from our anti-retroviral therapy (ART) clinic during a span of 4 years were retrospectively analyzed and reviewed. The diagnosis was based on the clinical and radiological picture and exclusion of other differential diagnosis by cerebrospinal fluid and serological studies.
UNASSIGNED: Of 765 patients with HIV/AIDS, 12 (1.56%) were diagnosed with PML on the basis of consistent clinical and radiological features after ruling out other differential diagnosis. PML was the initial presentation of HIV infection in 8 (55.5%) patients. 11 (89%) patients had CD4 count <200/μl. Insidious onset focal limb weakness (50%) and dysarthria (50%) were common symptoms. Magnetic resonance imaging of the brain revealed characteristic white matter lesions in all the patients. The estimated median survival was 40 months (95% confidence interval, 23.88-53.19 months).
UNASSIGNED: Our results show that PML is associated with high morbidity despite the institution of highly active ART (HAART), but mortality has significantly declined if ART is started early. Key to good response is early diagnosis and HAART.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nerve system caused by the John Cunningham virus. On MRI, PML may sometimes appear similar to primary central nervous system lymphoma (PCNSL) and glioblastoma multiforme (GBM). The purpose of this pilot study was to evaluate the potential of amide proton transfer (APT) imaging for differentiating PML from PCNSL and GBM.
Patients with PML (n = 4; two men; mean age 52.3 ± 6.1 years), PCNSL (n = 7; four women; mean age 74.4 ± 5.8 years), or GBM (n = 11; 6 men; mean age 65.0 ± 15.2 years) who underwent APT-CEST MRI between January 2021 and September 2022 were retrospectively evaluated. Magnetization transfer ratio asymmetry (MTRasym) values were measured on APT imaging using a region of interest within the lesion. Receiver operating characteristics curve analysis was used to determine diagnostic cutoffs for MTRasym.
The mean MTRasym values were 0.005 ± 0.005 in the PML group, 0.025 ± 0.005 in the PCNSL group, and 0.025 ± 0.009 in the GBM group. There were significant differences in MTRasym between PML and PCNSL (P = 0.023), and between PML and GBM (P = 0.015). For differentiating PML from PCNSL, an MTRasym threshold of 0.0165 gave diagnostic sensitivity, specificity, positive predictive value, and negative predictive value of 100% (all). For differentiating PML from GBM, an MTRasym threshold of 0.015 gave diagnostic sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 90.9%, 80.0%, and 100%, respectively.
MTRasym values obtained from APT imaging allowed patients with PML to be clearly discriminated from patients with PCNSL or GBM.

The high efficacy of natalizumab in the treatment of relapsing-remitting multiple sclerosis (MS) is without controversy. Indeed, effective disease control was not only demonstrated in the pivotal trials but has been corroborated impressively in real-world observations. This monoclonal IgG4 antibody blocks the α4β1 integrin-mediated leukocyte-endothelial interaction and thereby inhibits the migration of immune cells to the brain parenchyma. However, treatment with natalizumab carries the risk of progressive multifocal leukoencephalopathy (PML). This potentially lethal side effect is a significant limitation for treatment initiation and long-term therapy. Natalizumab is given intravenously or subcutaneously in the standard dose of 300 mg every 4 weeks, allowing drug concentrations at levels that ensure continuous α4β1 integrin receptor saturation on the surface of immune cells. Extended-interval dosing (EID) is an emerging treatment approach that aims to mitigate the natalizumab-related PML risk by prolonging the standard infusion intervals to 6 weeks or even more. This treatment approach may abrogate the PML risk due to improved immune surveillance within the central nervous system while maintaining clinical efficacy. Moreover, even an individual interval dosing can be envisioned based on the availability of a biomarker that is capable of monitoring both safety and efficacy aspects. This review summarizes the early and encouraging evidence for EID from observational and randomized-controlled trials and discusses current limitations and upcoming challenges for introducing a tailored treatment approach.

BACKGROUND: Natalizumab (NTZ) is increasingly being used in Indian multiple sclerosis (MS) patients. There are no reports on its safety and efficacy, especially with respect to the occurrence of progressive multifocal leukoencephalopathy (PML).
OBJECTIVE: To describe the patient characteristics, treatment outcomes, and adverse events, especially the occurrence of PML in NTZ-treated patients.
METHODS: A multicentre ambispective study was conducted across 18 centres, from Jan 2012 to Dec 2021. Patients at and above the age of 18 years treated with NTZ were included. Descriptive and comparative statistics were applied to analyze data.
RESULTS: During the study period of 9 years, 116 patients were treated with NTZ. Mean age of the cohort was 35.6 ± 9.7 years; 83/116 (71.6%) were females. Relapse rate for the entire cohort in the year before NTZ was 3.1 ± 1.51 while one year after was 0.20±0.57 (p = 0.001; CI 2.45 -3.35). EDSS of the entire cohort in the year before NTZ was 4.5 ± 1.94 and one year after was 3.8 ± 2.7 (p = 0.013; CI 0.16-1.36). At last follow up (38.3 ± 22.78 months) there were no cases of PML identified.
CONCLUSIONS: Natalizumab is highly effective and safe in Indian MS patients, with no cases of PML identified at last follow up.

Patients with progressive multifocal leukoencephalopathy (PML) in the context of human immunodeficiency virus-acquired immunodeficiency syndrome (HIV-AIDS) show a partial improvement following rehabilitation; however, this improvement is rapidly lost if the patient is not provided with intensive rehabilitation. A 42-year-old patient affected by HIV-AIDS had a clinical worsening within a few months following PML onset, despite being treated with antiretroviral drugs and conventional rehabilitation. He developed severe paraparesis and significant dependency in the activities of daily life. A first cycle of intensive rehabilitation provided the patient with some significant functional outcomes, although he experienced a worsening of the clinical condition after two months of rest, before admission to our rehabilitation unit. We thus sought to evaluate the effects of intensive robot-aided gait training (RAGT) coupled with transcranial direct current stimulation (tDCS). The patient significantly improved when provided with intensive RAGT coupled with tDCS (as per 10-meter Walk Test [10MWT] and 6-minute Walk Test [6MWT]), and the improvement was maintained at three-month follow-up. As this advanced approach was feasible, safe, and potentially effective, this case suggests that patients with PML-HIV require prolonged multidisciplinary rehabilitation treatment. We can speculate that individuals with PML should also be treated with innovative technology to improve their functional outcomes and therefore quality of life.

BACKGROUND: Natalizumab (NTZ) is a highly effective disease modifying treatment for relapsing multiple sclerosis (RMS), but it increases risk of progressive multifocal leukoencephalopathy (PML) in patients with serum anti- John Cunningham virus (JCV) antibodies.
OBJECTIVE: To assess the safety and efficacy of rapid transition, from NTZ to teriflunomide (TFM) in RMS patients.
METHODS: Clinically stable NTZ-treated, anti-JCV antibody positive RMS patients were switched to TFM 28 ± 7 days after their last dose of NTZ. The primary endpoint was proportion of relapse free patients at 24 months.
RESULTS: Median [IQR] age of the 55 enrolled patients was 47 [40.7, 56.3] years, 76% were female. The median [IQR] number of prior NTZ treatments was 34 [18, 64]. annualized relapse rate (ARR) was 0.07 and 77% of the patients were relapse free at 24 months. Mean time to first GAD + lesion was 19.6 months, and to new/enlarging T2 lesion was 19.2 months. Mean time to 3 month sustained disability worsening (SDW) was 22 months and proportion free of 3-month SDW was 0.87. There were no cases of PML.
CONCLUSIONS: The washout-free transition of NTZ to TFM was an efficacious and safe strategy for patients at risk of developing PML.ClinicalTrials.gov Identifier: NCT01970410.

Progressive multifocal leukoencephalopathy (PML) is an opportunistic infection of the central nervous system caused by the JC virus, which infects white and grey matter cells and leads to irreversible demyelination and neuroaxonal damage. Brain magnetic resonance imaging (MRI), in addition to the clinical presentation and demonstration of JC virus DNA either in the CSF or by histopathology, is an important tool in the detection of PML. In clinical practice, standard MRI pulse sequences are utilized for screening, diagnosis, and monitoring of PML, but validated imaging-based outcome measures for use in prospective, interventional clinical trials for PML have yet to be established. We review the existing literature regarding the use of MRI and positron emission tomography imaging in PML and discuss the implications of PML histopathology for neuroradiology. MRI not only demonstrates the localization and extent of PML lesions, but also mirrors the tissue destruction, ongoing viral spread, and resulting inflammation. Finally, we explore the potential for imaging measures to serve as an outcome in PML clinical trials and provide recommendations for current and future imaging outcome measure development in this area.