Computed tomography and magnetic resonance imaging findings in central nervous system listeriosis

PURPOSE

To describe the imaging findings and determine the incidence of a characteristic worm-like pattern along the white matter tracts in neurolisteriosis on CT/MRI.

METHODS

An IRB-approved retrospective study in 21 consecutive neurolisteriosis cases during January 2002-July 2020. At least one of the following is required: (1) Positive Listeria monocytogenes (LM) in blood with clinical signs of meningeal irritation and/or abnormal CSF profile, (2) positive LM in blood with signs of encephalitis, (3) positive LM in CSF, (4) positive LM from brain biopsy/aspiration. Six cases were excluded due to the lack of contrast-enhanced images, leaving a total of 15 cases for analysis (mean age 53.5 years ± 18.8 SD). The imaging studies were independently reviewed by two blinded readers. Demographic data, imaging findings, and incidence of the worm-like pattern were reported. The Cohen's kappa was used to calculate interrater reproducibility.

RESULTS

Of the 12 patients with relevant imaging findings, nine cases (75%) had parenchymal lesions (eight cases in supratentorial compartment and one case in infratentorial compartment), four cases (33.3%) had leptomeningeal enhancement and two cases (16.7%) had hydrocephalus. Brain abscesses were found in eight cases and nodules evocative of abscess in one case. Restricted diffusion in the central area and hemosiderin deposition were observed in all cases. The involvement of white matter tract in a worm-like pattern was demonstrated in eight of nine patients with parenchymal lesions (88.9%).

CONCLUSION

Abnormal findings in brain CT/MRI images are common in neurolisteriosis. The incidence of worm-like spread along the white matter tracts is high and may help diagnose suspicious patients.

Spike S2 Subunit: Possible Target for Detecting Novel SARS-CoV-2 Variants with Multiple Mutations

Novel SARS-CoV-2 variants have multiple mutations that may impact molecular diagnostics. The markedly conserved S2 subunit may be utilized to detect new variants. A comparison of 694 specimens (2019-2022) in Thailand using a commercial RT-PCR kit and the kit in combination with S2 primers and a probe was performed. Delayed amplification in ORF1ab was detected in one BA.4 omicron, whereas no amplification problem was encountered in the S2 target. There were no statistically significant differences in mean Ct value between the target genes (E, N, ORF1ab, and S2) and no significant differences in mean Ct value between the reagents. Furthermore, 230,821 nucleotide sequences submitted by 20 representative counties in each region (Jan-Oct 2022) have been checked for mutations in S2 primers and probe using PrimerChecker; there is a very low chance of encountering performance problems. The S2 primers and probe are still bound to the top five currently circulating variants in all countries and Thailand without mismatch recognition (Jun-Nov 2023). This study shows the possible benefits of detecting S2 in combination with simultaneously detecting three genes in a kit without affecting the Ct value of each target. The S2 subunit may be a promising target for the detection of SARS-CoV-2 variants with multiple mutations.

Serum proinsulin levels as peripheral blood biomarkers in patients with cognitive impairment

Insulin has long been associated with dementia. Insulin affecting the clearance of amyloid-β peptide and phosphorylation of tau in the CNS. Proinsulin is a precursor of insulin and its elevated serum levels are associated with peripheral insulin resistance that may reduce brain insulin levels. Our study aimed to assess differences in serum proinsulin levels between normal and cognitive impairment groups. Prospective recruitment of elderly participants was initiated from October 2019 to September 2023. Patients were divided into "cognitive impairment" and "normal cognition" group. All participants had blood drawn and serum proinsulin was measured at baseline and 12 months. Neurocognitive testing was performed every 6 months. A total of 121 participants were recruited. Seventy-seven were in the normal cognition group and 44 in the cognitive impairment group. The glycemic control and prevalence of diabetes type 2 was similar between groups. Baseline serum proinsulin levels were higher in the cognitively impaired group compared to the normal group at baseline (p = 0.019) and correlated with worse cognitive scores. We identified cognitive status, age, and BMI as potential factors associated with variations in baseline proinsulin levels. Given the complex interplay between insulin and dementia pathogenesis, serum biomarkers related to insulin metabolism may exhibit abnormalities in cognitive impaired patients. Here we present the proinsulin levels in individuals with normal cognitive function versus those with cognitive impairment and found a significant difference. This observation may help identifying non-diabetic patients suitable for treatment with novel AD drugs that related to insulin pathway.

Real-time quaking-induced conversion assay using a small-scale substrate production workflow for the diagnosis of Creutzfeldt-Jakob disease

The lack of a dedicated surveillance program for prion disease, particularly in low- and middle-income countries (LMICs), has hindered the global effort to address this public health threat. Although cerebrospinal fluid (CSF) Real-time quaking-induced conversion (RT-QuIC) is considered the most reliable test for sporadic Creutzfeldt-Jakob disease (sCJD), its availability in LMICs is limited due to its cost and technical difficulty in generating the recombinant prion protein substrate (recPrP). This study aimed to evaluate the performance of RT-QuIC with recPrP produced in-house through a small-scale method - i.e. the application of reusable pre-packed chromatography columns and subsequent dialysis. Here, CSF specimens from patients suspected of having prion disease were consecutively collected and stored between October 2015 and January 2023. Electronic medical record data were reviewed to clinically classified participants as probable sCJD or non-sCJD. CSF RT-QuIC was performed using in-house recPrP. Its specificity and sensitivity for diagnosing probable sCJD were reported, along with details of other clinical data and investigations. We found that among 39 eligible participants, with a median (interquartile range) age of 64 (56-70) years and 16 (41%) female, 13 had probable sCJD and the remaining 26 unequivocally suffered from non-prion disorders. Magnetic resonance imaging and electroencephalogram were suggestive of sCJD in 100% (13/13) and 46.2% (6/13) of sCJD participants, respectively. RT-QuIC was positive in 12/13 sCJD participants (sensitivity 0.92, 95% confidence interval (CI) 0.67-0.99) and negative in all non-sCJD participants (specificity 1.00, 95%CI 0.87-1.00). CSF tau/p-tau ratio showed sensitivity and specificity of 0.62-1.0 and 0.85-1.0, respectively. In summary, RT-QuIC using recPrP generated through a small-scale workflow demonstrated great performance in detecting sCJD. Given its performance results along with its low cost, this technique could feasibly be implemented in LMICs and potentially be the first step towards establishing local prion disease surveillance programs.

Two decades of one health surveillance of Nipah virus in Thailand

BACKGROUND

Nipah virus (NiV) infection causes encephalitis and has > 75% mortality rate, making it a WHO priority pathogen due to its pandemic potential. There have been NiV outbreak(s) in Malaysia, India, Bangladesh, and southern Philippines. NiV naturally circulates among fruit bats of the genus Pteropus and has been detected widely across Southeast and South Asia. Both Malaysian and Bangladeshi NiV strains have been found in fruit bats in Thailand. This study summarizes 20 years of pre-emptive One Health surveillance of NiV in Thailand, including triangulated surveillance of bats, and humans and pigs in the vicinity of roosts inhabited by NiV-infected bats.

METHODS

Samples were collected periodically and tested for NiV from bats, pigs and healthy human volunteers from Wat Luang village, Chonburi province, home to the biggest P. lylei roosts in Thailand, and other provinces since 2001. Archived cerebrospinal fluid specimens from encephalitis patients between 2001 and 2012 were also tested for NiV. NiV RNA was detected using nested reverse transcription polymerase chain reaction (RT-PCR). NiV antibodies were detected using enzyme-linked immunosorbent assay or multiplex microsphere immunoassay.

RESULTS

NiV RNA (mainly Bangladesh strain) was detected every year in fruit bats by RT-PCR from 2002 to 2020. The whole genome sequence of NiV directly sequenced from bat urine in 2017 shared 99.17% identity to NiV from a Bangladeshi patient in 2004. No NiV-specific IgG antibodies or RNA have been found in healthy volunteers, encephalitis patients, or pigs to date. During the sample collection trips, 100 community members were trained on how to live safely with bats.

CONCLUSIONS

High identity shared between the NiV genome from Thai bats and the Bangladeshi patient highlights the outbreak potential of NiV in Thailand. Results from NiV cross-sectoral surveillance were conveyed to national authorities and villagers which led to preventive control measures, increased surveillance of pigs and humans in vicinity of known NiV-infected roosts, and increased vigilance and reduced risk behaviors at the community level. This proactive One Health approach to NiV surveillance is a success story; that increased collaboration between the human, animal, and wildlife sectors is imperative to staying ahead of a zoonotic disease outbreak.

Detection of influenza virus in rectal swabs of patients admitted in hospital for febrile illnesses in Thailand

Introduction

Influenza virus favours the respiratory tract as its primary site of host entry and replication, and it is transmitted mainly via respiratory secretions. Nasopharyngeal swab is the gold standard specimen type for influenza detection, but several studies have also suggested that the virus replicates in the human gastrointestinal tract.

Methods

A retrospective study was conducted on all patients positive for influenza virus and initially recruited as part of the PREDICT project from 2017 to 2018. The objectives of the study were to investigate whether rectal swab could aid in improving influenza detection, and if there was any correlation between gastrointestinal disturbances and severity of infection, using length of hospital stay as an indicator of severity.

Results

Of the 51 influenza-positive patients, 12 had detectable influenza virus in their rectal swab. Among these 12 rectal swab positive patients, influenza virus was not detected in the nasopharyngeal swab of three of them. Gastrointestinal symptoms were observed for 28.2% patients with a negative rectal swab negative and 25.0% patients with a positive rectal swab. Average length of hospital stay was 4.2 days for rectal swab positive group and 3.7 days for rectal swab negative group. This difference was not statistically significant (p = 0.288).

Conclusions

There is no correlation between influenza virus detection in rectal swab and gastrointestinal disturbances or disease severity, and there is currently insufficient evidence to support replicative ability in the gastrointestinal tract.

Differences and diversity of autoimmune encephalitis in 77 cases from a single tertiary care center

Background

The incidence of autoimmune encephalitis has risen globally. There are two general categories of disease-associated antibodies that can be tested for: neuronal surface and intracellular. However, testing both groups of autoantibodies are costly. This study aims to identify differences between groups by comparing clinical presentations, radiological findings and CSF profile of patients, and determine if any parameters are indicative of one group of autoantibodies over another. Additionally, we aim to report the local incidence of less common groups of disease-associated antibodies as well.

Methods

Seventy-seven records of autoimmune encephalitis/encephalomyelitis patients admitted to King Chulalongkorn Memorial Hospital, Bangkok, Thailand, between October 2010 and February 2017 were reviewed. Patients with infections or those with classic central nervous system demyelinating features were excluded.

Results

Of 77 patients, 40% presented with neuronal surface antibodies and 33% had intracellular antibodies. The most common autoantibody detected in each group was anti-NMDAr antibody (25/31, 81%) and anti-Ri antibody (7/25, 28%) respectively. In the neuronal surface antibody group, behavioral change was the most common complaint (45%), followed by seizures (39%) and abnormal movements (29%). In the latter group, seizure was the most common presenting symptom (32%), followed by motor weakness (20%), behavioural change (16%) and abnormal movements (16%). Patients with neuronal surface antibodies were younger (35 vs 48 years old, p = 0.04) and more likely to present with behavioral change (45% vs 16%, p = 0.02). Mortality rate was higher in the intracellular group (16% vs 3.2%, p = 0.09). No differences were detected in magnetic resonance imaging (MRI) and CSF profile.

Conclusions

In the early stages of the disease, both groups have comparable clinical outcomes. Although there were significant differences in age and percentage of patients with behavioral change, both groups of autoimmune encephalitis still shared many clinical features and could not be distinguished based on MRI and CSF profiles. Therefore, we recommend that patients with features of autoimmune encephalitis should be screened for both the neuronal surface and intracellular antibodies regardless of clinical presentation.

Predictive values and specificity of electroencephalographic findings in autoimmune encephalitis diagnosis

OBJECTIVE

Early diagnosis of autoimmune encephalitis (AE) to not delay treatment is challenging but needed in practice. Most previous evidences of electroencephalographic (EEG) findings in AE were derived from descriptive studies. Given paucity of evidence of specific EEG findings to help with early diagnosis of AE, this study aimed to ascertain specific EEG findings and assess their predictive values in diagnosis of AE.

METHODS

We included all cases with AE in our institution from January 2013 to June 2017. Cases were matched with controls by age and level of consciousness (1:2 ratio). Potential confounders for EEG findings collected as baseline characteristics were compared. Two epileptologists independently reviewed EEGs. Standardized terminology, definitions, and scoring system of EEG findings were employed. Logistic regression analysis was performed, and diagnostic performance of significant EEG features was assessed.

RESULTS

Twenty cases and 40 controls were included in this study. Poorly sustained posterior dominant rhythm (PDR) was significantly associated with AE (p = 0.007) and even more predictive in anti-N-methyl-d-aspartate (NMDA) encephalitis. Inter-rater agreement (kappa) was 0.714. None of the cases had normal EEG nor Grand Total EEG (GTE) score < 4 (negative predictive value (NPV) of 100%). Specificity of well sustained PDR to exclude the diagnosis of anti-NMDA encephalitis was high (91.67%).

CONCLUSIONS

Simple EEG assessment can be used to help exclude AE. When AE is suspected, careful assessment of the sustainment of the PDR is warranted. The NPV of GTE score < 4 and specificity of well sustained PDR can be simply used to differentiate many conditions from AE.

Normocellular CSF in herpes simplex encephalitis

Background

Herpes simplex virus (HSV) is the most common cause of sporadic encephalitis worldwide. The high mortality rate (70–80 %) of herpes simplex encephalitis (HSE) can be reduced to 20–30 % by antiviral therapy. However, normocellular CSF can lure physicians to look for non-infectious causes, resulting in delayed treatment. This study aimed to investigate, characterize and differentiate HSE patients, with normocellular and pleocytosis CSF, according to neuroimaging patterns, underlying disease, CSF viral load and clinical outcome. Patients with proven (by PCR positive CSF) or presumed viral infections of the CNS admitted to King Chulalongkorn Memorial Hospital between January 2002 and 2011 were analyzed.

Results

HSV was detected in the CSF of 43 patients but only 23 patients had encephalitis. Among these 23 patients, 6 cases (26.1 %) had normal CSF WBC (<5 cells/mm³). One patient in this normocellular CSF group had HIV infection. Although this patient had low CD4 counts (<200 cells/mm³), the peripheral WBC counts showed only mild leukopenia. The CSF HSV viral load in the pleocytosis group was higher than the normocellular group, with an average of 12,200 vs 3027 copies/ml respectively. There was no correlation between the viral load and the clinical outcome. With respect to neuroimaging, 4 (66.7 %) patients in the normocellular group had unremarkable/non-specific results.

Conclusions

Normocellular CSF in HSE is not rare, and can be seen in normal as well as immunocompromised hosts. Clinicians should not exclude CNS infection, especially HSE, merely based on the absence of CSF pleocytosis and/or unremarkable neuroimaging study.