Immune-Mediated Central Nervous System Disease-Current Knowledge and Recommendations

Use of neurofilament light chain to identify structural brain diseases in dogs

BACKGROUND

Neurofilament light chain (NfL) is released into the peripheral circulation by damaged axons.

OBJECTIVES

To evaluate the diagnostic value of serum NfL concentration in dogs with intracranial diseases.

ANIMALS

Study included 37 healthy dogs, 31 dogs with idiopathic epilepsy (IE), 45 dogs with meningoencephalitis of unknown etiology (MUE), 20 dogs with hydrocephalus, and 19 dogs with brain tumors.

METHODS

Cohort study. Serum NfL concentrations were measured in all dogs using single-molecule array technology.

RESULTS

Serum NfL concentration in dogs with each structural disease was significantly higher than in healthy dogs and dogs with IE (P = .01). The area under the receiver operating characteristic curve of NfL for differentiating between dogs with structural diseases and IE was 0.868. An optimal cutoff value of the NfL 27.10 pg/mL had a sensitivity of 86.67% and a specificity of 74.19% to differentiate the dogs with IE from those with structural brain diseases. There were significant correlations between NfL concentrations and lesion size: (1) MUE, P = .01, r = 0.429; (2) hydrocephalus, P = .01, r = 0.563.

CONCLUSIONS AND CLINICAL IMPORTANCE

Serum NfL could be a useful biomarker for distinguishing IE from structural diseases in dogs and predicting the lesion sizes of MUE and hydrocephalus.

A potential early clinical phenotype of necrotizing meningoencephalitis in genetically at-risk pug dogs

BACKGROUND

Necrotizing meningoencephalitis (NME) in the pug dogs is a fatal neuroinflammatory disease associated with rapid progression and poor response to conventional immunosuppressive therapy. Diagnosis is typically made after severe neurological abnormalities have manifested.

HYPOTHESIS/OBJECTIVE

Pug dogs at genetic risk for NME might manifest neurological abnormalities before developing pathognomonic clinical signs of NME.

ANIMALS

Thirty-six pug dogs less than 4 years of age asymptomatic for NME.

METHODS

Prospective observational cohort study with germline genome-wide genotyping. Neurological examinations were performed 4 weeks apart to document reproducible findings of central nervous system disease. Magnetic resonance imaging, cerebrospinal fluid analysis, and testing for infectious diseases were performed in all pugs with reproducible abnormalities detected on neurological examination.

RESULTS

The overall risk allele frequency in this cohort was 40%; 5 (14%) dogs were high risk, 19 (53%) dogs were medium risk, and 12 (33%) dogs were low genetic risk for NME. Reproducible abnormalities detected on neurological examination were identified in 8/24 (33%) genetically at-risk dogs and 0/12 (0%) low risk dogs. Clinical abnormalities included multifocal spinal pain in 8/8, reduced menace response in 5/8, and lateralizing postural reaction deficits in 5/8 pugs. There was a strong association between genotype risk and the presence of this clinical phenotype (P = .03).

CONCLUSIONS AND CLINICAL IMPORTANCE

Our findings suggest the presence of a novel early clinical phenotype of NME in apparently asymptomatic genetically at-risk pugs which might be used to plan early diagnostic and therapeutic clinical trials.

Meningeal B Cell Clusters Correlate with Submeningeal Pathology in a Natural Model of Multiple Sclerosis

Multiple sclerosis (MS) is an idiopathic demyelinating disease in which meningeal inflammation correlates with accelerated disease progression. The study of meningeal inflammation in MS has been limited because of constrained access to MS brain/spinal cord specimens and the lack of experimental models recapitulating progressive MS. Unlike induced models, a spontaneously occurring model would offer a unique opportunity to understand MS immunopathogenesis and provide a compelling framework for translational research. We propose granulomatous meningoencephalomyelitis (GME) as a natural model to study neuropathological aspects of MS. GME is an idiopathic, progressive neuroinflammatory disease of young dogs with a female bias. In the GME cases examined in this study, the meninges displayed focal and disseminated leptomeningeal enhancement on magnetic resonance imaging, which correlated with heavy leptomeningeal lymphocytic infiltration. These leptomeningeal infiltrates resembled tertiary lymphoid organs containing large B cell clusters that included few proliferating Ki67+ cells, plasma cells, follicular dendritic/reticular cells, and germinal center B cell-like cells. These B cell collections were confined in a specialized network of collagen fibers associated with the expression of the lympho-organogenic chemokines CXCL13 and CCL21. Although neuroparenchymal perivascular infiltrates contained B cells, they lacked the immune signature of aggregates in the meningeal compartment. Finally, meningeal B cell accumulation correlated significantly with cortical demyelination reflecting neuropathological similarities to MS. Hence, during chronic neuroinflammation, the meningeal microenvironment sustains B cell accumulation that is accompanied by underlying neuroparenchymal injury, indicating GME as a novel, naturally occurring model to study compartmentalized neuroinflammation and the associated pathology thought to contribute to progressive MS.

Protective effect of dexmedetomidine on neuronal hypoxic injury through inhibition of miR-134

OBJECTIVE

To explore the mechanism of dexmedetomidine (DEX)-mediated miR-134 inhibition in hypoxia-induced damage in PC12 cells.

METHODS

Hydrogen peroxide (H₂O₂)-stimulated PC12 cells were divided into control, H₂O₂, DEX + H₂O₂, miR-NC/inhibitor + H₂O₂, and miR-NC/ mimic + DEX + H₂O₂ groups. Cell viability and apoptosis were assessed by the 3-(4,5-dimethylthiazol(-2-y1)-2,5-diphenytetrazolium bromide (MTT) assay and Annexin V-FITC/PI staining, while gene and protein expression levels were detected by qRT-PCR and western blotting. Reactive oxygen species (ROS) levels were tested by 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining, and malondialdehyde (MDA) content was determined with a detection kit.

RESULTS

DEX treatment decreased H₂O₂-elevated miR-134 expression. H₂O₂-induced PC12 cell damage was improved by DEX and miR-134 inhibitor; additionally, cell viability was increased, while cell apoptosis was reduced. In addition, both DEX and miR-134 inhibitor reduced the upregulated expression of cleaved caspase-3 and increased the downregulated expression of Bcl-2 in H₂O₂-induced PC12 cells. However, compared to that in the DEX + H₂O₂ group, cell viability in the mimic + DEX + H₂O₂ group was decreased, and the apoptotic rate was elevated with increased cleaved caspase-3 and decreased Bcl-2 expression. Inflammation and oxidative stress were increased in H₂O₂-induced PC12 cells but improved with DEX or miR-134 inhibitor treatment. However, this improvement of H₂O₂-induced inflammation and oxidative stress induced by DEX in PC12 cells could be reversed by the miR-134 mimic.

CONCLUSION

DEX exerts protective effects to promote viability and reduce cell apoptosis, inflammation, and oxidative stress in H₂O₂-induced PC12 cells by inhibiting the expression of miR-134.

Pharmacokinetics of a cytosine arabinoside subcutaneous protocol in dogs with meningoencephalomyelitis of unknown aetiology

Cytosine arabinoside (CA) is a commonly used treatment for dogs with meningoencephalomyelitis of unknown aetiology (MUE) with various proposed protocols, many requiring 24 hours (h) of hospitalization or two visits within 24 h. This is a unidirectional study evaluating the pharmacokinetics of a CA subcutaneous (SC) protocol and a standard constant rate infusion (CRI) protocol in 8 dogs with MUE. Dogs received the CRI (200 mg/m² IV over 24 h), followed by a SC protocol (50 mg/m² every 2 h for 4 treatments) four weeks later. Plasma CA concentrations were measured by high-pressure liquid chromatography-tandem mass spectrometry (HPLC-MS). Median peak CA concentration for the SC protocol (3.40 µg/ml, range 1.60-9.70 µg/ml) was significantly higher than the CRI (1.09 µg/ml, range 0.77-1.67 µg/ml; p = .02). Median concentration at 1h and 8h following initiation of treatment was significantly higher for the SC protocol (CA₁ 2.28 µg/ml, range 0.97-2.67; CA₈ 1.83 µg/ml, range 0.77-2.84) compared to the CRI (CA1 0.01 µg/ml, range 0-0.45; CA₈ 0.74 µg/ml, range 0.67-1.11; p = .01). While the PK properties of CA when administered as a CRI has been previously investigated, this study demonstrated that CA when administered via repeated 50 mg/m² injections every 2 h over an 8-h period, provided sustained plasma levels above its therapeutic target and for a significantly longer duration of time than did a standard CRI protocol.

[Canine meningoencephalitis and meningitis: retrospective analysis of a veterinary hospital population]

OBJECTIVE

Characterization of the etiology of meningoencephalitis and meningitis in dogs through an analysis of a veterinary hospital population.

MATERIAL AND METHODS

Retrospective study (2011-2016) with evaluation of clinical and diagnostic data of dogs with cerebrospinal fluid (CSF) pleocytosis (> 5/µl). Only dogs with cytological evaluation of CSF or pathological examination of CNS were included. Results of CSF cytology and examination for infectious diseases were reviewed.

RESULTS

A total of 62 dogs met the inclusion criteria. 14.5 % (n = 9) were classified as reactive CSF pleocytosis due to other structural CNS disease, such as neoplasia or infarct. Meningoencephalitis or meningitis of unknown origin was diagnosed in 56.5 % (n = 35). In 29.0 % (n = 18), investigations for infectious diseases or presence of bacteria in CSF cytology (n = 5) indicated an infectious etiology. This infectious etiology appeared reliable in 6 dogs (9.7 %) based on the examination findings, in 9 dogs (14.5 %), there was only a suspicion of infectious meningoencephalitis or meningitis and in 3 dogs (4.8 %), the findings were of uncertain significance.

CONCLUSION

The most common cause of CSF pleocytosis was meningoencephalitis or meningitis of unknown origin. Nevertheless, there was evidence of a possible infectious etiology in 29 % of the dogs. For a reliable diagnosis, it is important to assess the CSF cytology and to conduct investigations for infectious diseases.

CLINICAL RELEVANCE

Meningoencephalitis or meningitis of unknown origin requires immunosuppressive therapy. Therefore, CSF cytology and investigations for infectious diseases are important for an exclusion of infectious meningoencephalitis or meningitis.

Survival time and relapse in dogs with meningoencephalomyelitis of unknown origin treated with prednisolone and ciclosporin: a retrospective study

OBJECTIVE

To analyse outcome in dogs with a presumptive diagnosis of meningoencephalomyelitis of unknown origin (MUO) treated with prednisolone and ciclosporin and to assess the effect of a number of patient variables on survival time and rate of relapse.

DESIGN

Retrospective case series.

METHODS

Medical records of 40 client-owned dogs with a diagnosis of MUO treated with prednisolone and ciclosporin at one institution between June 2010 and January 2018 were reviewed retrospectively to assess survival times and prognostic indicators for death and/or relapse. The minimum follow-up time was 11 months post-diagnosis.

RESULTS

Median survival was 1345 days (95% confidence interval: 487-∞). No associations with hazard of death or relapse were detected for the presence of multifocal magnetic resonance imaging (MRI) abnormalities, caudal fossa location of MRI abnormalities, value of cerebrospinal fluid total nucleated cell count or total protein at time of diagnosis, or suspected elevation in intracranial pressure at time of diagnosis.

CONCLUSION

Protracted survival time may be achieved with a treatment combination of prednisolone and ciclosporin. Suspected elevation in intracranial pressure at the time of diagnosis did not affect long-term outcome in this cohort.

Case Report: Meningoencephalomyelitis of Unknown Etiology Manifesting as a Bilateral Cranial Polyneuropathy in 3 Dogs

A bilateral cranial polyneuropathy was the primary magnetic resonance imaging (MRI) finding in three medium to large breed dogs diagnosed with meningoencephalomyelitis of unknown etiology. All three dogs presented with a progressive history of vestibular ataxia with either central vestibular or multifocal central nervous system (CNS) neuroanatomical localization. Brain MRI revealed variable degree of bilateral enlargement and/or increased contrast enhancement of the optic, oculomotor, trigeminal, facial, and vestibulocochlear nerves, as well as enhancement of the orbital fissure (oculomotor, trochlear, ophthalmic branch of trigeminal, and abducens nerves). There was evidence of intracranial and cranial cervical meningeal contrast enhancement in all three dogs and of cervical spinal cord lesions in 2. In all cases, more cranial nerves were affected than indicated by neurological examination. Cerebrospinal fluid (CSF) analysis was consistent with a mononuclear pleocytosis in 2 cases and a mixed cell (predominantly lymphocytic) pleocytosis in 1 case. All dogs were treated with immune suppressing medications and showed clinical improvement, although some cranial nerve deficits were persistent at follow up 2 months later. These are the first known cases of MUE diagnosed ante-mortem in a canine population documenting bilaterally symmetrical lesions affecting multiple cranial nerves. While MUE is a common cause of non-infectious inflammatory disease in dogs, it likely encompasses more classifications than have previously been reported, and should remain a differential for dogs of all ages and sizes presenting with cranial nerve deficits.

Measurement of Neutrophil Gelatinase-Associated Lipocalin Concentration in Canine Cerebrospinal Fluid and Serum and Its Involvement in Neuroinflammation

Neutrophil gelatinase-associated Lipocalin (NGAL) is a glycoprotein involved in inflammation acting as an acute phase protein and chemokine as well as a regulator of iron homeostasis. NGAL has been shown to be upregulated in experimental autoimmune encephalomyelitis (EAE) in mice. Increased NGAL concentration in cerebrospinal fluid (CSF) and expression in central nervous system (CNS) has been described in human neuroinflammatory disease such as multiple sclerosis and neuropsychiatric lupus as well as in bacterial meningitis. We aimed to investigate involvement of NGAL in spontaneous canine neuroinflammation as a potential large animal model for immune- mediated neurological disorders. A commercially available Enzyme-linked Immunosorbent Assay (ELISA) for detection of canine NGAL was validated for use in canine CSF. Concentration in CSF and serum of canine patients suffering from steroid- responsive meningitis- arteriitis (SRMA), Meningoencephalitis of unknown origin (MUO), different non- inflammatory CNS disease and control dogs were compared. Relationship between NGAL concentration in CSF and serum and inflammatory parameters in CSF and blood (IgA concentration, total nucleated cell count (TNCC), protein content) as well as association with erythrocytes in CSF, duration of illness, plasma creatinine and urinary leucocytes were evaluated. In dogs with SRMA and MUO, CSF concentration of NGAL was significantly higher than in dogs with idiopathic epilepsy, compressive myelopathy, intracranial neoplasia and SRMA in remission (p < 0.0001). Patients with acute SRMA had significantly higher levels of NGAL in CSF than neurologically normal controls (p < 0.0001). Serum NGAL concentrations were significantly higher in dogs with SRMA than in patients with myelopathy and intracranial neoplasia (p < 0.0001). NGAL levels in CSF were strongly positively associated with IgA concentration (rSpear= 0.60116, p < 0.0001), TNCC (rSpear= 0.65746, p < 0.0001) and protein content (rSpear= 0.73353, p < 0.0001) in CSF. It can be measured in CSF of healthy and diseased dogs. Higher concentrations in canine patients with SRMA as well as positive association with TNCC in CSF suggest an involvement in pro-inflammatory pathways and chemotaxis in SRMA. High serum levels of NGAL in serum of SRMA patients in different stages of disease might reflect the systemic character of the disease.