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Acute syphilitic optic neuritis.

Two patients experienced acute unilateral visual loss as a manifestation of early infectious (secondary) neurosyphilis. In both cases, optic disc swelling was preceded by the development of a characteristic rash accompanied by mild signs of meningeal inflammation. Other signs of ocular inflammation, such as uveitis or retinal vasculitis, were absent. Optic neuritis may occur as a manifestation of the meningeal inflammation that can accompany secondary syphilis. In such patients, it is important to confirm involvement of the CNS and to institute appropriate antibiotic therapy.

Acute Disease↗

Acute and chronic experimental optic neuritis. Alteration in the blood-optic nerve barrier.

Horseradish peroxidase (HRP) tracer studies in experimental allergic optic neuritis showed alterations in the blood-optic nerve barrier. Light and electron microscopic examination of the optic disc disclosed intense leakage of HRP at the lamina scleralis, with extracellular staining of both axonal and glial columns, despite the lack of inflammation at this region. The intraorbital optic nerve showed leakage of HRP at the sites of both acute and chronic demyelination. Ultrastructurally, leakage of HRP was confined to the perivascular and extracellular spaces. The mechanism of leakage seems to be by diffusion through the endothelial cell junctions or vesicular transport across the endothelial cells. The high predilection for involvement of the optic nerve in chronic demyelinating disorders may be due to the inherent weakness of the blood-brain barrier at the optic nerve head.

Animals↗

Differentiation between recently resolved optic neuritis and central serous retinopathy. Use of tests of visual function.

A test battery was performed on 13 patients with resolved central serous retinopathy and on 13 patients with resolved optic neuritis to see whether the tests would help to distinguish between the two conditions. We found that the most useful discriminators were the relative afferent pupillary defect, followed by the visual evoked potential latency and the critical flicker frequency. The total error score on the Farnsworth-Munsell 100-Hue Test and the nature of the color vision defect were not helpful in separating the two diseases.

Adult↗

Magnetic resonance imaging of the brain in isolated optic neuritis.

Magnetic resonance imaging of the brain was performed on ten patients who had isolated optic neuritis. Seven patients had abnormal images, with a distribution of lesions similar to that seen in multiple sclerosis, demonstrating subclinical dissemination in the central nervous system.

Adolescent↗

Various stages of optic neuritis assessed by subjective brightness of flicker.

In the Aulhorn flicker test, the subjective brightness of a steady field is matched to that of a flickering field at 50 to 0 Hz. The test gives pathologic values only for active optic neuritis (ON) and gives normal results for normal eyes and eyes with subsided ON and other diagnoses, with a specificity of 98% and a sensitivity of 85.5%. Characteristic variations of the curves of subjective brightness during the course of ON allow a subtle assessment of five different disease stages, and there is a clear distinction between various disease patterns, ie, acute, chronic, recurrent, diminishing, and subsided ON. This distinction is impossible on the basis of visual evoked potentials. The test can be done easily and quickly without major technical equipment, even in an ophthalmologist's office.

Flicker Fusion↗

Antioxidant enzymes reduce loss of blood-brain barrier integrity in experimental optic neuritis.

We studied the effect of antioxidant enzymes on the loss of integrity of the blood-brain barrier in the optic nerves of strain-13 guinea pigs with chronic experimental allergic encephalomyelitis, a demyelinating disorder with neurologic and histopathologic characteristics similar to multiple sclerosis. Animals with experimental allergic encephalomyelitis received daily intraperitoneal injections of either preservative-free saline (group 1), catalase (group 2), or glutathione peroxidase (group 3) for 2.2 months after the onset of appendicular paralysis. Following intravascular administration, extravascular leakage of horseradish peroxidase was histopathologically graded as mild, moderate, or severe within the optic nerve head and myelinated retrolaminar nerve. Severe extravasation of horseradish peroxidase was exclusive to group 1, in addition to moderate and mild leakage. In groups 2 and 3, leakage of horseradish peroxidase was infrequent, and when detected, it was graded as mild. Detoxification of hydrogen peroxide with catalase and glutathione peroxidase substantially reduced horseradish peroxidase leakage in experimental optic neuritis, suggesting a role for hydrogen peroxide and its reactive by-products in the pathogenesis of increased vascular permeability of the blood-brain barrier in experimental allergic encephalomyelitis.

Animals↗

Hydrogen peroxide localization in experimental optic neuritis.

The association of reactive oxygen species to altered permeability of the blood-brain barrier in acute experimental encephalomyelitis was investigated by ultrastructural cytochemical localization of hydrogen peroxide (H2O2) to sites in the optic nerve previously identified by extravasation of intravascular horseradish peroxidase. Using a modified cerium method, we found electron-dense cerium-derived H2O2 reaction product was localized to the perivascular space at the lamina retinalis, lamina choroidalis, and lamina scleralis. In the optic nerve head, electron-dense reaction product was observed in the presence of intravascular leukocytes, although adjacent perivascular and interstitial inflammatory cells at this site were scant. In the myelinated retrobulbar optic nerve, cerium-derived H2O2 reaction product was seen in the intravascular space of blood vessels and surrounding perivascular and interstitial foci of inflammatory cells. Reaction product was also observed in the extracellular space adjacent to the plasmalemma of axons and glial cells in the optic nerve head and retrobulbar nerve. The perivascular and intravascular distribution of cerium-derived reaction product suggests that H2O2 may play a role in the pathogenesis of altered vascular permeability in experimental optic neuritis and supports our previous observations of suppression of blood-brain barrier permeability by detoxification of H2O2 with the exogenous administration of antioxidant enzymes.

Animals↗

Resistance and susceptibility to experimental autoimmune neuritis in Sprague-Dawley and Lewis rats correlate with different levels of autoreactive T and B cell responses to myelin antigens.

Experimental autoimmune neuritis (EAN) is a CD4+ T cell-mediated, inflammatory demyelinating disease of the peripheral nervous system (PNS) that serves as a model for Guillain-Barré syndrome (GBS) in humans. Various mouse and rat strains show different susceptibilities to EAN that can be induced by immunization with bovine PNS myelin (BPM) + Freund's complete adjuvant (FCA). We examined PNS-induced T and B cell responses and cytokine protein production as well as mRNA expression to study the mechanisms behind susceptibility to EAN in Lewis rats and resistance in Sprague-Dawley (SD) rats. Lewis rats with EAN have elevated PNS myelin-reactive interferon-gamma (IFN-gamma) production, TNF-alpha mRNA expression, and increased B cell responses to PNS myelin antigens, but low PNS myelin-reactive transforming growth factor-beta (TGF-beta) and interleukin (IL)-10 mRNA expression in lymph node mononuclear cells (MNC). In contrast, resistance to EAN in SD rats is associated with reduced BPM and P2 peptide-reactive IFN-gamma production, TNF-alpha mRNA expression, and suppressed B cell responses to PNS myelin antigens as well as up-regulation of TGF-beta and IL-10 mRNA expression. Resistance to EAN is also associated with low-grade inflammation or absence of histological evidence of EAN. These results suggest that differential autoreactive T and B cells responses to PNS myelin antigens are strain specific, and the susceptibility to EAN is related to quantitative rather than qualitative differences in distribution between proinflammatory and anti-inflammatory cytokines.

Animals↗

IFN-beta suppresses experimental autoimmune neuritis in Lewis rats by inhibiting the migration of inflammatory cells into peripheral nervous tissue.

The putative prophylactic and therapeutic effect of interferon-beta (IFN-beta) on autoimmune inflammation of the peripheral nervous system was evaluated in experimental autoimmune neuritis (EAN), a well-known animal model of the human Guillain-Barré syndrome (GBS). We report that treatment of rats with 300,000 U of recombinant rat IFN-beta (rrIFN-beta) given every other day starting at the day of immunization prevented clinical signs of EAN. When treatment was started at the onset of disease development, the cytokine clearly ameliorated EAN. Both B- and T-cell responses towards peripheral myelin were suppressed by the IFN-beta, and immunohistochemical analyses revealed a strong decrease in the numbers of infiltrating CD4(+) T cells, macrophages, and other inflammatory cells as well as a significant reduction in MHC class II antigen expression and monocyte chemotactic protein-1 (MCP-1) production, which induces chemotaxis and chemokinesis of leukocytes from blood. It is concluded that the observed suppression of EAN by rrIFN-beta is associated with a decrease in the migration of inflammatory cells into peripheral nervous tissue.

Adjuvants, Immunologic↗

Disruption and reorganization of sodium channels in experimental allergic neuritis.

The axonal distribution of voltage-dependent Na+ channels was determined during inflammatory demyelinating disease of the peripheral nervous system. Experimental allergic neuritis was induced in Lewis rats by active immunization. In diseased spinal roots Na+ channel immunofluorescence at many nodes of Ranvier changed from a highly focal ring to a more diffuse pattern and, as the disease progressed, eventually became undetectable. The loss of nodal channels corresponded closely with the development of clinical signs. Electrophysiological measurements and computations showed that a lateral spread of nodal Na+ channels could contribute significantly to temperature sensitivity and conduction block. During recovery new clusters of Na+ channels were seen. In fibers with large-scale demyelination, the new aggregates formed at the edges of adhering Schwann cells and appeared to fuse to form new nodes. At nodes with demyelination limited to paranodal retraction, Na+ channels were often found divided into two symmetric highly focal clusters. These results suggest that reorganization of Na+ channels plays an important role in the pathogenesis of demyelinating neuropathies.

Animals↗

The action mechanism of cyclooxygenase-2 inhibitor for treatment of experimental allergic neuritis.

We previously reported the effect of a cyclooxygenase (COX)-2 inhibitor, nimesulide, on experimental allergic neuritis (EAN) in both the induction and effector phases, in contrast to the usual COX inhibitor, which was effective only when administered in the induction phase. To assess the mechanism of action of a COX-2 inhibitor, we studied the expression of COX-2 and assayed plasma levels of prostaglandins, and also compared the clinical effect of a COX-2 inhibitor with a 5-lipoxygenase (LO) inhibitor, which is responsible for another pathway of arachidonic acid metabolism. Nerves of EAN rats showed distinct expression of COX-2, which is derived mostly from endoneurial macrophages. Treatment with a COX-2 inhibitor had no effect on its expression. However, prostaglandin estradiol (E(2)) concentration of plasma was significantly lower compared with the control group. The LO inhibitor showed no clinical effect. These results suggest that a selective COX-2 inhibitor is effective in the effector phase by its influence on macrophages that are responsible for nerve degeneration.

Animals↗

Localization of endothelial-monocyte-activating polypeptide II (EMAP II), a novel proinflammatory cytokine, to lesions of experimental autoimmune encephalomyelitis, neuritis and uveitis: expression by monocytes and activated microglial cells.

Endothelial-Monocyte-Activating Polypeptide II (EMAP II) is a proinflammatory cytokine and chemoattractant of macrophages. In order to investigate the role of EMAP II in autoimmune lesions of the rat nervous system, we have used a synthetic gene to express EMAP II in E. coli and have produced monoclonal antibodies against EMAP II. Monoclonal antibodies are suited to demonstrate EMAP II in ELISAs, Western blots, and paraffin-embedded tissue sections. EMAP II was localized to monocytes/macrophages with rather selective staining of a minor rat monocyte subpopulation of lymphoid tissues such as spleen, lymph nodes or follicles of the gut. In the normal brain, cells of the perivascular but not parenchymal microglia were stained. We then investigated expression of EMAP II during experimental autoimmune encephalomyelitis (EAE), neuritis (EAN), and uveitis (EAU). Within the local inflammatory lesions infiltrating macrophages are prominently stained. In the diseased brain, EMAP II-positive microglial cells are not only found in the direct vicinity of the inflammatory infiltrate, but widespread activation is seen in the parenchyma. This is the first demonstration that EMAP II is present in autoimmune lesions. Immunostaining of microglial cells is noteworthy, as these cells are strategically placed regulatory elements of CNS immunosurveillance. EMAP II might be a factor regulating monocyte chemoattraction, endothelial cell activation and a regulator of microglial cell reactivity in autoimmune inflammation of the central nervous system.

Amino Acid Sequence↗

Allograft-inflammatory factor-1 in rat experimental autoimmune encephalomyelitis, neuritis, and uveitis: expression by activated macrophages and microglial cells.

Allograft inflammatory factor-1 (AIF-1) is a Ca2+ binding peptide expressed predominantly by activated monocytes. In order to investigate the role of AIF-1 in autoimmune lesions of the rat nervous system, we have used a synthetic gene to express AIF-1 in E. coli and have produced monoclonal antibodies against AIF-1. AIF-1 was localized to monocytes/macrophages with rather selective staining of a minor rat monocyte subpopulation of lymphoid tissue. We then investigated expression of AIF-1 in experimental autoimmune encephalomyelitis (EAE), neuritis (EAN), and uveitis (EAU). Within the local inflammatory lesions, infiltrating macrophages are prominently stained. In the diseased brain, AIF-1-positive microglial cells are not only found in the direct vicinity of the infiltrate, but widespread activation is seen in the parenchyma. This is the first demonstration that AIF-1 is present in autoimmune lesions. Immunostaining of microglial cells is noteworthy, as these cells are strategically placed regulatory elements of CNS immunosurveillance. Thus, AIF-1 might be a valuable marker to dissect the local monocyte heterogeneity in autoimmune disease.

Amino Acid Sequence↗

Brachial plexus neuritis and fatal hemorrhage following Aspergillus infection of a Hickman catheter.

A patient with relapse of acute granulocytic leukemia developed an Aspergillus infection along the subcutaneous tract of a silicone rubber indwelling central venous catheter. The infection invaded the brachial plexus resulting in paralysis of the right upper extremity and subsequently invaded a major artery of the arm resulting in the demise of the patient. Both an infectious brachial plexus neuritis and fatal hemorrhage secondary to a Hickman catheter are apparently rare.

Antineoplastic Agents↗

Lipid-free versus lipid-bound P2 protein-induced experimental allergic neuritis: clinicopathological, neurophysiological, and immunological study.

The P2 protein of the peripheral nervous system myelin is a neuritogenic protein capable of inducing experimental allergic neuritis (EAN) in the Lewis rat. It has been suggested that the addition of some lipids to the protein isolated in the lipid-free form might enhance its immunogenicity. In this study, we compared lipid-free P2 (the EAN factor) and the corresponding lipid-bound form of the protein regarding their ability to induce EAN. Lipid-bound P2, copurified with all the myelin lipids, shows a conformation different from that of LF-P2. The timing of disease and the clinical scores of lipid-bound P2-induced EAN animals (n = 23) did not differ statistically from those injected with lipid-free P2 (n = 23), with only a tendency to higher clinical severity in the former group. Tail nerve conduction velocities did not differ in the two groups and in both were significantly lower in comparison to Freund adjuvant controls (n = 8). Inflammation and demyelination predominated in the spinal roots and were less evident in the sciatic nerve for both groups of animals. The ELISA determination of antibodies to lipid-free and lipid-bound P2 revealed the development of antibodies recognizing the lipid-free form of the protein in both groups of animals. Our results stand in contrast to results of previous studies performed after addition of exogenous lipids to the P2 purified in the lipid-free form and indicate that lipid-bound P2 is not significantly more immunogenic than lipid-depleted P2.

Adjuvants, Immunologic↗

P0 protein peptide 180-199 together with pertussis toxin induces experimental autoimmune neuritis in resistant C57BL/6 mice.

The C57BL/6 mice strain is known to be reputedly resistant to induction of experimental autoimmune neuritis (EAN), an animal model of Guillain-Barré syndrome in human by bovine peripheral myelin (BPM), and P2 protein or the P2 protein peptide 57-81. The P0 peptide 180-199 is a stronger neuritogenic antigen than the P2 peptide 57-81. We found that this synthetic peptide induced both clinical and pathological characteristics of an acute monophasic EAN in C57BL/6 mice. Only male mice were more sensitive to EAN induction with the P0 peptide 180-199. Intravenously administrated pertussis toxin (PT) had an adjuvant effect that increased the incidence of P0 peptide 180-199-induced EAN as well as the inflammation and demyelination in the peripheral nerves. Spontaneous and P0 peptide 180-199 stimulated proliferation of peripheral T-cells were enhanced by PT-treatment as well. The enhancing effect was lower before onset of the disease (Day 6 post immunization) (p.i.) as compared to the early phase of the disease (Day 22 p.i.). Thus, P0 peptides together with PT are able to break tolerance to myelin in C57BL/6 mice.

Adjuvants, Immunologic↗

B-lymphocyte and plasma cell clonal expansion in monosymptomatic optic neuritis cerebrospinal fluid.

The CD19+ B-lymphocyte and CD138+ plasma cell repertoires in cerebrospinal fluid from four patients with monosymptomatic optic neuritis (ON) were analyzed by single-cell reverse transcriptase polymerase chain reaction. Amplified heavy (H)- and light (L)-chain antibody segments were sequenced and used to identify the rearranged germline and J segment of closest homology. Both the B-cell and plasma cell repertoires from ON cerebrospinal fluid demonstrated significant clonal expansion. Up to 75% of the amplified H- and L-chain sequences were contained in overrepresented populations and were somatically mutated, consistent with an antigen-targeted response. The relationship between clonal populations within the CD19+ B lymphocyte and CD138+ plasma cell populations suggests ongoing mutational pressure to refine antigen binding. Our observations demonstrate that an antigen-driven clonal B-lymphocyte and plasma cell response is prominent in the initial stages of central nervous system demyelination and suggest that detection of the disease-relevant antigens in ON may bear on the inciting antigens in chronic inflammatory disorders such as multiple sclerosis.

Amino Acid Sequence↗

Quantifying axonal loss after optic neuritis with optical coherence tomography.

OBJECTIVE: To determine to what degree changes in retinal nerve fiber layer (RNFL) thickness after optic neuritis (ON) correlate with either visual recovery or impairment. METHODS: ON can cause visible defects within the RNFL, which can be quantified using optical coherence tomography (OCT). It may be possible to predict visual recovery by measuring RNFL loss after ON. Fifty-four patients underwent repeated evaluations with optical coherence tomography and standardized ophthalmic testing after ON. Regression analyses were used to determine the relationship between RNFL thickness and visual function. RESULTS: Thinning of the RNFL was seen in the majority of patients (74%), and it tended to occur within 3 to 6 months of ON. The average RNFL value was thinner (p<0.0001) in the affected (78 microm) compared with the unaffected eye (100 microm). Patients with incomplete visual recovery demonstrated greater RNFL loss after ON. Regression analyses demonstrated a threshold of RNFL thickness (75 microm), below which RNFL measurements predicted persistent visual dysfunction. INTERPRETATION: Determination of RNFL thickness may predict visual recovery after ON, and lower RNFL values correlate with impaired visual function. Optical coherence tomography may have a potential role as a surrogate marker for axonal integrity within the optic nerve among patients with ON.

Adolescent↗