A new perspective on the role of the frontoparietal regions in Stroop-like conflicts.

Humans are goal-directed; however, goal-unrelated information still affects us, but how? The Stroop task is often used to answer this question, relying on conflict (incongruency) between attributes, one targeted by the task and another irrelevant to the task. The frontal regions of the brain are known to play a crucial role in processing such conflict, as they show increased activity when we encounter incongruent stimuli. Notably, the Stroop stimuli also consist of conceptual dimensions, such as semantic or emotional content, that are independent of the attributes that define the conflict. Since the non-targeted attribute usually refers to the same conceptual dimension as the targeted-attribute, it is relevant to the task at hand. For example, when naming the emotion of an emotional face superimposed by an emotional word, both the targeted-attribute and the non-targeted attribute refer to the conceptual dimension "emotion". We designed an fMRI paradigm to investigate how conflicts between different conceptual dimensions impact us. Even though the conflict was task-irrelevant, incongruent stimuli resulted in longer reaction times, indicating a behavioral congruency effect. When examining the neural mechanisms that underlie this effect, we found that the frontal regions exhibited repetition suppression, while the bilateral intraparietal sulcus (IPS) showed a congruency effect linked to the behavioral effect. Taken together, these findings suggest that individuals are unable to completely ignore task-irrelevant information, and that the IPS plays a crucial role in processing such information.

Epilepsy following herpes simplex encephalitis - A case series.

BACKGROUND: Herpes simplex encephalitis (HSE) is associated with severe mortality and morbidity. Its incidence is estimated at 1:250 000, and the typical symptomatology of acute disease including headaches, mental state disturbances, confusion, sleepiness, and seizures. The chronic phase of the disease is occasionally characterized by epilepsy and neurological deficits. STUDY RATIONALE: The present retrospective single-center study aims to identify risk factors for predicting the development of epilepsy (epileptogenesis) following HSE. METHODS: Medical records were screened for patients older than 18 years, hospitalized between January 2005 and September 2019 with a diagnosis of "encephalitis" and "herpes simplex virus, HSV" infection. HSE diagnosis was based on an analysis of the cerebrospinal fluid with positive HSV testing results. RESULTS: Twenty-three patients fit our inclusion criteria: fever and behavioral changes, followed by seizures, were reported in 58.3 % of patients. On follow-up (59.7 ± 38.8 months), eight patients (34.8 %) developed epilepsy. Pathological imaging and EEG were correlated with acute symptomatic seizures (ASS). ASS was associated with an 8-fold risk increase to develop post-encephalitis epilepsy (PE). PE was associated with younger age but not with CSF results, imaging, or EEG. CONCLUSION: Our retrospective single-center study on PE, following HSE, shows that younger age and ASS were associated with PE. Brain imaging, CSF analysis, and EEG were not associated with the development of epilepsy following HSE.

Elevated lumbar puncture opening pressure in aseptic meningitis.

OBJECTIVES: Elevated lumbar puncture opening pressure (ELPOP) is a reported but understudied phenomenon in aseptic meningitis. This study aimed to characterize the features of ELPOP in aseptic meningitis patients. METHODS: An observational, retrospective, single-center study was conducted. We included all adult patients diagnosed with aseptic meningitis or meningoencephalitis from October 2015 to May 2017, for whom lumbar puncture opening pressure (LP OP) was measured. OP > 25 cm H2O was documented as ELPOP. Patients' demographic characteristics, clinical data, laboratory and cerebrospinal fluid (CSF) results, as well as optic disc appearance were analyzed. RESULTS: Among 116 patients (61 males) included, 16 patients (14 %) had ELPOP (11 males). The average age of those patients was 32.4 years (SD = 9.8), and the mean OP was 31.7 cm H2O (SD = 6.02) as opposed to the mean normal LPOP (NLPOP) of16.13 cm H2O (SD = 4.15). Body mass index (BMI) was significantly higher in the ELPOP group (p = 0.0081). Funduscopic examination was documented in 15/16 patients in the ELPOP group and revealed swollen optic discs in 6 (40 %) patients. Fundus examination was performed in 62 patients in the NLPOP group, of whom 2 (3.2 %) had a swollen disc. There was no difference in CSF content between groups. CONCLUSIONS: This study fills the void of information lacking on the frequency of ELPOP in aseptic meningitis. Its association with increased BMI may be related to the pathogenesis. LP OP should be measured in all patients with aseptic meningitis. Additional research is needed to determine the threshold of tolerated intracranial pressure (ICP).

Repeated lumbar puncture in search of oligoclonal bands - What is the yield?

BACKGROUND: Cerebrospinal fluid (CSF) oligoclonal bands (OCBs) are immunoglobulins that represent intrathecal synthesis during central nervous system infection or inflammation. As repeated lumbar puncture (LP) is usually not performed unless clinically indicated, there is very limited data on the natural history and course of OCBs status in the CSF, its relation to disease activity, duration of persistence, and the rate of either CSF conversion of OCBs or disappearance. METHODS: We retrospectively collected data from adult patients with various neurological syndromes who had repeated CSF samplings. OCBs were analyzed by agarose gel electrophoresis or by isoelectric focusing. RESULTS: During the years 2010-2020, we identified 48 patients with at least two CSF OCBs results in Rabin Medical Center. These included 11 patients with Multiple Sclerosis, ADEM and NMOSD (one patient each), 7 patients with unspecified demyelinating disease, 4 with optic neuropathy, 15 patients with unknown diagnosis. Overall, 6/48 (12.5%) patients had change in OCBs status between first and second LP's. Four (8.33%) patients changed OCBs from positive to negative, and two patients (4.2%) from negative to positive. There was no significant difference in demographic, disease category, CSF constituents or time interval to second LP between patients who changed their OCBs status to those who did not. CONCLUSION: Repeated LP for OCBs analysis in our cohort did not yield a practical benefit. The conversion rate of OCBs status was low (12.5%) and in most cases did not lead to a change in the final diagnosis or patient's clinical management.

Early safety and tolerability profile of the BNT162b2 COVID-19 vaccine in myasthenia gravis.

Although the COVID-19 vaccines are currently recommended for people with myasthenia gravis (MG), there is no data regarding the safety of the vaccines in this population. In order to investigate the real-life safety data of the BNT162b2 COVID-19 vaccine in people with MG, an anonymous survey was distributed to 142 MG patients. Fifty-six MG patients completed the questionnaire. The median age was 53 years (range 23-83 years); 35 (62.5%) were males, and 25 (44.6%) had associated comorbidities. Thirty-seven participants (66.1%) were treated with immunotherapies. Fifty-five participants (98.2% of the responders) received the BNT162b2 COVID-19 vaccine. Of these, 32 (58.2%) were < 55 years old, and 23 (41.8%) were > 55 years old. Adverse events were more common in patients younger than 55 years old (46.9% Vs. 17.4%; p = 0.0428). Eight participants (14.5%) reported worsening neurological symptoms following the vaccination. Three of those who reported worsening of neurological symptoms (37.5%) required additional treatment. Most events occurred within the first few days after vaccination and resolved within a few weeks. This survey indicates an overall favorable safety and tolerability profile of the BNT162b2 vaccine in people with MG. Additional prospective, large-scale studies are warranted to confirm these findings.

Non-infectious mechanisms of neurological damage due to infection.

Infections of the nervous system is a growing aspect of clinical neurology. Accumulating knowledge in early diagnosis, course, therapy and prognosis is enlarging the clinical tools required for effective therapy. Of special importance is the ability to differentiate between proper infections, where anti-microbial agents, when available, should be introduced and used and post infectious conditions where therapy is mainly directed against the host immune system. The two conditions sometimes overlap, a situation that requires the ability to combine clinical skills with the use of laboratory tools such as polymerase chain reaction (PCR), serology, and antigenic detection. In the era of the SARS-CoV-2 pandemic, the need to make this distinction is emphasized as correct diagnosis of post infectious conditions and expedited therapy is important and sometimes lifesaving. We here attempt to present several infectious agents and their possible indirect damage to the nervous system causing in some cases significant neurological deficits. We try to limit our focus on those mechanisms which do not involve the direct tissue damage by the infectious agents but rather are connected to para- and post-infectious mechanisms. We attempt to delineate the features that will enable to tailor the correct diagnosis and following the effective therapy.

Herpes simplex encephalitis in patients receiving chemotherapy and whole-brain radiation therapy.

Herpes simplex encephalitis (HSE) is a very severe infection of the central nervous system (CNS) caused mainly by herpes simplex virus type 1 (HSV-1) and occasionally by herpes simplex virus type 2 (HSV-2). After relapse or drug-resistant to chemotherapy, whole-brain radiation therapy (WBRT) is a mainstay of treatment in patients with both identifiable brain metastases and CNS lymphoma. Although HSV-1 encephalitis predominantly affects immunocompetent host, HSV encephalitis may be more common in immune-suppressed patients than is currently recognized. Disease presentation may be atypical including lack of pleocytosis in cerebrospinal fluid (CSF). We report four patients diagnosed with HSE following chemotherapy and WBRT. The occurrence of HSE in patients with cancer seems not to be increased compared to the general population, but as our case series shows, a high level of suspicion is needed by the treating physician to diagnose HSE early in patients presenting with new neurological symptoms following WBRT.

Vocal cord paresis on CTA - A novel tool for the diagnosis of lateral medullary syndrome.

BACKGROUND: Diagnosis of lateral medullary syndrome (LMS) is often delayed due to elusive clinical presentations and frequently non-revealing neuroimaging tests. We aimed to investigate the use of ipsilateral vocal cord paresis (VCP) identified on neck computed tomography angiography (CTA) as an early diagnostic sign for LMS. METHODS: Medical records were queried for patients admitted with LMS between 1/2012 and 10/2020. A control group of patients undergoing CTA for transient or no neurological symptoms was matched for sex and age. Clinical data were collected by a stroke neurologist. Two neuroradiologists independently and blindly assessed CTA images for radiological signs of VCP. RESULTS: Fifteen LMS and 15 control patients were included in the analysis. Median time from arrival to LMS diagnosis was 29.4 h [IQR 7,47] and twice as long in patients who suffered aspiration pneumonia. Thrombolysis rate was 0% in LMS patients versus 14.5% in general stroke patients. Dysphonia was noted in the emergency department in three (20%) patients, whereas all 15 patients had radiological signs of VCP on CTA. Medialization of a true vocal cord was the most sensitive (100%) and specific (80-87%) sign for LMS, with good inter-rater agreement (kappa 0.66). Timely detection of VCP on CTA could have shortened median time to LMS diagnosis by 14 h and enabled thrombolytic therapy in 3 (20%) patients. CONCLUSIONS: VCP on CTA is a valuable sign for the diagnosis of LMS. If detected early, it may enable reperfusion therapy and prevent aspiration pneumonia, consequently saving life and diminishing disability.

Safety of the BNT162b2 COVID-19 vaccine in multiple sclerosis (MS): Early experience from a tertiary MS center in Israel.

BACKGROUND AND PURPOSE: Although the COVID-19 vaccines are currently recommended for people with multiple sclerosis (MS), the fact that they were not specifically tested in people with MS raises uncertainty regarding their safety in this population. The purpose of this study was to report real-life safety data of the BNT162b2 COVID-19 vaccine in a cohort of MS patients. METHODS: An anonymous survey was distributed to 425 MS patients. Participants were asked general demographic and disease-related questions and specific questions regarding the safety profile of the COVID-19 vaccine. RESULTS: Of the 425 MS patients, 262 completed the questionnaire. The median (range) participant age was 42 (22-79) years, 199 participants were women (75.9%), and 66 participants (25.2%) had associated comorbidities. A total of 198 participants (75.6%) were treated with disease-modifying therapies. In all, 239 participants (91.2% of the responders) had received the BNT162b2 COVID-19 vaccine. Of these, 182 (76.1%) were aged <55 years, and 57 (23.9%) were aged >55 years. Adverse events were reported by 136 participants (56.9%; 52.5% of those aged <55 years and 40.3% of those aged >55 years; p = 0.1517) and 36 participants (15.1%) reported new or worsening neurological symptoms following the vaccination, the most frequent being sensory disturbances (21 participants, 58.3%). Most symptoms occurred within the first 24 h after vaccination and resolved within 3 days. A total of 28 participants (77.8%) did not require any medication to treat their symptoms. CONCLUSIONS: This survey indicates an overall favorable safety profile of the BNT162b2 vaccine in people with MS. These data should be confirmed in further prospective, large-scale studies.

Chronic low-dose intravenous immunoglobulins as steroid-sparing therapy in myasthenia gravis.

INTRODUCTION: Intravenous immunoglobulin (IVIg) has been proven beneficial in myasthenic crisis, but their role as maintenance therapy is unclear. The aim of this study was to determine if maintenance therapy with low-dose IVIg improves clinical outcome and may be used as a steroid-sparing agent in myasthenia gravis (MG). METHODS: We retrospectively reviewed charts of all MG patients treated with IVIg from January 2006 to December 2019. Long-term treatment response to IVIg was assessed by improvement in the Myasthenia Gravis Foundation of America (MGFA) clinical classification scale as primary end point, as well as the ability to reduce the time-weighted average required dose of prednisone as secondary end-point, in a follow-up period of 36 months. RESULTS: 109 patients were treated with IVIg. The mean follow-up time was 34.03 ± 5.5 months. Sixty-seven patients (61.4%) responded to therapy with at least one-point improvement of the MGFA scale. There was no statistical difference in demographic and clinical characteristics between IVIg responders and non-responders. The mean prednisone dose decreased significantly from 33.1 ± 14.5 mg at baseline to 7.2 ± 7.8 mg after 36 months of IVIg treatment (P < 0.0001), with the greatest effect after 6 months (33.1 ± 14.5 mg Vs. 17.9 ± 11.7 mg; P < 0.0001). In the follow-up period of 36 months, most patients (92.5%) remained clinically and pharmacologically stable under chronic IVIg treatment. CONCLUSION: This retrospective study demonstrates that chronic low-dose IVIg treatment in patients with MG improves clinical outcomes and has a prolonged and significant steroid-sparing effect over a period of 3 years.

Exacerbation of myasthenia gravis following corticosteroid treatment: what is the evidence? A systematic review.

Corticosteroids (CS) are among the most widely- used immunosuppressive agents for immune-mediated conditions, including myasthenia gravis (MG). While their effectiveness in MG is documented and supported in the clinical practice over several decades, one of the main drawbacks of treatment results from the notion that MG patients may experience symptom worsening following CS treatment initiation. This may lead to the administration of lower than necessary doses of CS for the disorder, or even avoiding them altogether. As a consequence, some patients may not receive the optimal treatment to control their disease. In the present review, we analyzed 27 relevant publications and determined the prevalence of clinical exacerbation following CS treatment, its' severity and relation to the type and dose of CS. The rate of MG exacerbation is highest with the administration of cortisone, intermediate with prednisone, and lowest with methylprednisolone. High dose daily or alternate-day prednisone is associated with exacerbation more frequently than low-dose treatment, but most exacerbations are of mild to moderate severity. Other factors related to increased risk of an initial exacerbation include older age, generalized MG, bulbar symptoms, disease severity, presence of thymoma, and thymectomy. However, the current information is based mostly on heterogeneous studies of low quality, and prospective clinical trials designed to compare between the various agents and doses and assess the rate and severity of the exacerbation by a unified scale are warranted.

Saliva immunoglobulin free light chain analysis for monitoring disease activity and response to treatment in multiple sclerosis.

BACKGROUND: Immunoglobulin free light chains (FLC) have recently gained considerable interest as new promising intrathecal biomarkers of multiple sclerosis (MS). However, lumbar puncture is invasive and not practical for monitoring disease course. This study aimed to assess the utility of saliva FLC as a biomarker of disease activity and response to treatment in MS METHODS: Western blotting was used to study saliva FLC monomers and dimers. The intensity of immunoreactive FLC bands was quantified by electrophoresis analysis, and the obtained values were used as FLC indices to account for kappa and lambda FLC monomer and dimer levels. Firth's logistic regression analysis suitable to study small cohorts was applied to compare FLC levels between M.S. patients in relapse, MS patients in remission, and healthy controls. Association between FLC levels and clinical and radiological parameters was analyzed. RESULTS: 55 MS patients and 40 healthy controls were evaluated. Saliva FLC levels were significantly higher in relapse compared to remission. Logistic regression analysis employing a combination of FLC indices confirmed the significant difference between these two groups. The FLC levels were significantly reduced by treatment with corticosteroids. During remission, patients treated with disease-modifying therapies had lower levels of FLC compared to untreated patients. The increased FLC levels were associated with the presence of gadolinium-enhancing lesions, but not with MRI T2 lesion load and EDSS scores. During individual patient follow-up, the changes of the saliva FLC levels were in concordance with the disease activity status. CONCLUSIONS: Saliva FLC levels may be a useful biomarker for discriminating between stable remission and active disease. The developed test may serve as a new, non-invasive, and inexpensive tool for monitoring disease activity and response to treatment in MS.

Incidence of AChR Ab-positive myasthenia gravis in Israel: A population-based study.

BACKGROUND: The incidence of myasthenia gravis (MG) has traditionally been low, ranging between 2-6/106 . Several recent epidemiological studies have reported a higher incidence. We, therefore, aimed to assess and characterize the incidence of MG in Israel. METHODS: We retrospectively reviewed the records of all four laboratories that performed the acetylcholine receptor antibody (AChR Ab) test in Israel between 1994 and 2013 and documented the number of newly diagnosed seropositive MG patients each year. To assure that data indeed reflect only newly diagnosed patients, patient's names and ID numbers were screened at the Hadassah medical center database since 1978, the year when the test was first performed in Israel. In order to calculate the annual incidence of the disease, the population at risk was derived from the annual publication of the Israeli Central Bureau of Statistics. RESULTS: The annual incidence of MG for this time period was 13.1/106 inhabitants. The mean incidence of MG between 1994 and 2003 was 7.695/106 /y, while the mean incidence between 2004 and 2013 was 18.49/106 (P < .0001). Mean age of diagnosis between 1994 and 2003 was 56.65 ± 0.9351, while between 2004 and 2013, it was 59.89 ± 0.5336 (P = .0012). Male to female (M:F) incidence ratio in the years 1994-2003 and 2004-2013 was 2:3.2 and 3:1.8, respectively, reflecting increased incidence among males (P < .0001). CONCLUSIONS: The incidence of MG in Israel has increased significantly during the last decade, especially among males of older age. These findings may reflect an etiological role of an environmental factor, increased awareness, and increased longevity in general.

Meningitis without meningeal irritation signs: What are the alerting clinical markers?

OBJECTIVE: To identify parameters that may increase the likelihood of meningitis, and suggest a need for lumbar puncture (LP), in patients without meningeal irritation signs (MIS). METHODS: We included consecutive adult patients who underwent LP in the emergency department (ED) of Rabin Medical Center between October 2015 and May 2017. Those hospitalized during this period, who did not undergo LP in the ED, but subsequently underwent LP during their hospitalization to rule out central nervous system infection, were also included. Each patient was evaluated prior to LP by a neurologist according to predefined parameters concerning the current disease history and the neurological examination. Patients' medical records were reviewed to obtain additional data. Patients evaluated while in coma or under sedation were excluded. RESULTS: Three hundred and thirty eight patients were included in the final analysis: 96 (28.4%) with meningitis without MIS, 149 (44.1%) without MIS or meningitis, 57 (16.9%) with meningitis and MIS, and 36 (10.6%) with MIS without meningitis. In the absence of MIS, younger age (p = .005), headache (p < .001), nausea (p < .001), vomiting (p = .001), painful eye movements (p < .001) and phonophobia (p = .04) increased the likelihood of meningitis, while fever, laboratory results (leukocytosis; lymphopenia; CRP) and immunosuppression were of no value in this prediction. Photophobia and lymphopenia were more common in meningitis with MIS. Headache was suggestive of meningitis when MIS were present. CONCLUSION: Our study identified several parameters that increase the likelihood of meningitis in patients without MIS. These should be taken into evaluation when LP is considered.

Generation of neuroinflammation in human African trypanosomiasis.

Human African trypanosomiasis (HAT) is caused by infection due to protozoan parasites of the Trypanosoma genus and is a major fatal disease throughout sub-Saharan Africa. After an early hemolymphatic stage in which the peripheral tissues are infected, the parasites enter the CNS causing a constellation of neurologic features. Although the CNS stage of HAT has been recognized for over a century, the mechanisms generating the neuroinflammatory response are complex and not well understood. Therefore a better understanding of the mechanisms utilized by the parasites to gain access to the CNS compartment is critical to explaining the generation of neuroinflammation. Contrast-enhanced MRI in a murine model of HAT has shown an early and progressive deterioration of blood-CNS barrier function after trypanosome infection that can be reversed following curative treatment. However, further studies are required to clarify the molecules involved in this process. Another important determinant of brain inflammation is the delicate balance of proinflammatory and counterinflammatory mediators. In mouse models of HAT, proinflammatory mediators such as tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and CXCL10 have been shown to be crucial to parasite CNS invasion while administration of interleukin (IL)-10, a counter inflammatory molecule, reduces the CNS parasite burden as well as the severity of the neuroinflammatory response and the clinical symptoms associated with the infection. This review focuses on information, gained from both infected human samples and animal models of HAT, with an emphasis on parasite CNS invasion and the development of neuroinflammation.

Effect of Repeated Intravenous Amantadine Infusions in Patients with Parkinson's Disease: An Open-Label Pilot Study.

Amantadine is an antiviral drug available in oral and intravenous forms. Oral amantadine is used to treat the motor symptoms of early Parkinson's disease (PD) and to ameliorate dyskinesia in late-stage disease. However, the long-term influence of intravenous amantadine on motor symptoms and dyskinesias in PD has not been investigated. The aim of the present study was to examine the long-term effect of repeated boosts of intravenous amantadine in patients with PD with and without response fluctuations and dyskinesias. Twelve patients diagnosed with PD, six with levodopa intolerance or insufficient response to antiparkinson medications, and six with response fluctuations and dyskinesias, were treated with intravenous amantadine for 6 months: three sequential infusions over 3 days in the first month followed by five once-monthly infusions. Changes in motor function and involuntary movements were evaluated with the Unified Parkinson Disease Rating Scale (UPDRS) and Abnormal Involuntary Movement Scale (AIMS; dyskinesia group). A significant immediate improvement in motor scores was documented in both groups after amantadine infusion. However, the difference in mean UPDRS motor score from before the first infusion to after 6 months of treatment was not statistically significant. In patients with dyskinesias, there was a significant improvement in AIMS scores between the first and the last visits (6.3 ± 2.7 vs. 1.6 ± 1.3; P = 0.014). In conclusion, continuous treatment with intravenous amantadine can be useful in patients with PD for immediate relief of motor symptoms and in patients with dyskinesias for progressive reduction of involuntary movements.

Does CSF pleocytosis have a predictive value for disease course in MS?

Objective: MS is a demyelinating CNS disorder with a spectrum of clinical patterns regarding course and prognosis. Although several prognostic factors are considered in the initial evaluation of patients, biological markers defining the disease course and guiding treatments are currently lacking. It is unknown whether patients with CSF pleocytosis differ in regard to symptoms, disease course, and prognosis from those without. The aim of this study was to evaluate whether CSF pleocytosis during the initial presentation has an impact on the clinical course and progression of MS. Methods: We retrospectively evaluated patients attending the MS Clinic at Rabin Medical Center between January 1999 and January 2016 who underwent lumbar puncture (LP) at disease presentation, considering CSF cell count, clinical diagnosis (clinically isolated syndrome [CIS] and relapsing-remitting MS [RRMS]), annualized relapse rate (ARR), paraclinical findings (imaging, CSF oligoclonal bands, and evoked potentials), and disease progression, expressed by the Expanded Disability Status Scale (EDSS). Results: One hundred fourteen patients (72 females) underwent LP at disease presentation (RRMS: n = 100, CIS: n = 14). Age at diagnosis was 32.4 ± 12.2 years, and the follow-up time was 9.4 ± 3.8 years. Forty-six patients showed a pleocytic CSF (≥5 cells per µL). Compared with patients with <4 cells per µL, patients with pleocytosis had a higher ARR (0.60 ± 0.09 vs 0.48 ± 0.04; p = 0.0267) and a steeper increase (slope) in the EDSS score throughout the follow-up period (correlation coefficient: r2 = 0.04; p = 0.0251). Conclusions: CSF pleocytosis may be considered a biological unfavorable predictive factor regarding disease course and progression in MS.

Hepatitis B and C virus infection as a risk factor for Parkinson's disease in Israel-A nationwide cohort study.

OBJECTIVE: To study the association between hepatitis C and B viruses and Parkinson's disease (PD) in Israel. METHODS: A retrospective cohort study was performed by analyzing the computerized database of Clalit Healthcare Service in Israel. Cohorts of people with hepatitis C virus (HCV) infection, hepatitis B virus (HBV) infection and nonalcoholic steatohepatitis (NASH) were constructed and compared to a reference cohort for prevalence of PD. RESULTS: The prevalence of PD in Israel was found to be 0.5% in the general population. The M-H (Mantel-Haenszel) odds ratio (OR) of PD for HBV-positive patients was 1.08 (95% CI: 1.00-1.16). The M-H OR of PD for HCV-positive patients was 1.18 (95% CI: 1.04-1.35). The M-H OR of PD for patients infected with both hepatitis C and B was 1.13 (95% CI: 0.87-1.47). The M-H OR of PD for patients diagnosed with nonalcoholic steatohepatitis (NASH) was 1.13 (95% CI: 1.08-1.19). CONCLUSIONS: We report evidence supporting a minor increased risk for PD in patients with HCV. Co infection of HCV and HBV was not associated with an increased risk for PD. The increased risk for PD in the group of patients with NASH, raises the possibility that liver disease per se is a risk factor for PD rather than viral infection. In addition, it cannot be ruled out that the association is, at least in part, the result of the occurrence of cirrhosis induced parkinsonism that was misclassified as PD.