Prognostic value of neurofilament light in blood in patients with polyneuropathy: A systematic review.

Neurofilament light protein (NfL) is a part of the neuronal skeleton, primarily expressed in axons, and is released when nerves are damaged. NfL has been found to be a potential diagnostic biomarker in different types of polyneuropathies. However, whether NfL levels can be used as a predictor for the risk of disease progression is currently less understood. We searched MEDLINE (PubMed), Embase, Cochrane Library, and Web of Science Searches and included longitudinal studies with a baseline and follow-up examination of adult patients with polyneuropathy and NfL measured in blood. Twenty studies investigating NfL as a predictor of disease progression were identified, examining eight polyneuropathy subtypes. The results from studies in Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) patients were divergent, with two out of five studies finding a significant association between NfL levels and clinical outcomes. Meta-analysis of the three Guillian-Barré Syndrome (GBS) studies found higher odds for the inability to run after 1 year in patients with high levels of NfL (odds ratio 2.18, 95% confidence interval 1.04-4.56). Results from studies examining other subacute or chronic polyneuropathies like Charcot-Marie-Tooth (CMT) varied in study design and results. Our findings suggest NfL can be used as a predictor of disease progression, particularly in polyneuropathies such as CIDP and GBS. However, NfL may not serve as a reliable and cost-effective biomarker for slowly progressive polyneuropathies like CMT. Future standardized studies considering NfL as a prognostic blood biomarker in patients with different types of polyneuropathies are warranted.

Accumulation of lactate in the rat brain during hyperammonaemia is not associated with impaired mitochondrial respiratory capacity.

In acute liver failure (ALF) cerebral oedema and high intracranial pressure (ICP) are potentially deadly complications. Astrocytes cultured in ammonia have shown mitochondrial dysfunction and in rat models of liver failure, de novo lactate production in the brain has been observed and has led to a hypothesis of compromised brain metabolism during ALF. In contrast, normal lactate levels are found in cerebral microdialysate of ALF patients and the oxygen: glucose ratio of cerebral metabolic rates remains normal. To investigate this inconsistency we studied the mitochondrial function in brain tissue with respirometry in animal models of hyperammonaemia. Wistar rats with systemic inflammation induced by lipopolysaccharide or liver insufficiency induced by 90% hepatectomy were given ammonium or sodium acetate for 120 min. A cerebral cortex homogenate was studied with respirometry and substrates of the citric acid cycle, uncouplers and inhibitors of the mitochondrial complexes were successively added to investigate the mitochondrial function in detail. In a separate dose-response experiment cortex from healthy rats was incubated for 120 min in ammonium acetate in concentrations up to 80 mM prior to respirometry. Hyperammonaemia was associated with elevated ICP and increased tissue lactate concentration. No difference between groups was found in total respiratory capacity or the function of individual mitochondrial complexes. Ammonium in concentrations of 40 and 80 mM reduced the respiratory capacity in vitro. In conclusion, acute hyperammonaemia leads to elevated ICP and cerebral lactate accumulation. We found no indications of impaired oxidative metabolism in vivo but only in vitro at extreme concentrations of ammonium.

Vasculitic neuropathy.

Vasculitic neuropathy (VN) may affect the peripheral nervous system alone (non-systemic vasculitic neuropathy (NSVN)) or be part of a systemic vasculitis. Studies indicate that NSVN is ascommon as other inflammatory neuropathies but is underdiagnosed, probably becausethe clinical phenotype is very heterogenous and vary from sub-acute painful mononeuritis multiplex to progressive, symmetric polyneuropathy. Since the irreversible nerve damage can be reduced with immunosuppressants, early recognition of VN is important. More studies are needed to validate treatment and outcome measures.

Misinterpretation of non-systemic vasculitic neuropathy results in delayed treatment.

This case report presents two patients who were diagnosed with non-systemic vasculitic neuropathy (NSVN). The phenotypes were atypical: 1) slowly progressive neuropathy and 2) plexopathy in contrast to the classic NSVN phenotype: painful, asymmetric with subacute progression. Both patients had remarkable responses to the immunosuppressants prednisolone and rituximab, and the cases highlight the importance to consider NSVN as a differential diagnosis of patients with neuropathy of unknown aetiology, as treatment can be initiated to avoid irreversible nerve damage.

[First Danish case of tick-borne encephalitis virus vaccine failure].

Tick-borne encephalitis virus (TBEV) is spreading geographically, and new risk areas are expected throughout Denmark. In this case report, we describe the first Danish case of vaccine breakthrough tick-borne encephalitis (TBE) in a 76-year old female suffering from severe symptoms with need of intensive-care therapy. We want to draw attention to TBE as a differential diagnosis in all undiagnosed patients with symptoms of viral encephalitis, regardless of travel history and vaccine status. TBEV can cause severe disease, especially in the elderly. Patients with vaccine breakthrough infection may develop a more severe disease than non-vaccinated.