Degeneration and dysfunction of neurons in the brain are hallmarks of neurodegenerative diseases. Over the past decades, significant efforts have been devoted to the development and validation of biomarkers for neurodegenerative diseases. The range and diversity of biomarkers for central nervous system (CNS) diseases has continued to expand, encompassing biofluid-based sources such as blood or cerebrospinal fluid (CSF), nucleic acids, tissues, and imaging. While imaging and tissue biopsy-based markers are continually being identified and their applications expanding, they do have limitations compared with RNA and protein biomarkers. This review comprehensively summarizes various biomarkers, including microRNA (miRNA), long noncoding RNA (lncRNA), circulating miRNA (cimiRNA), and proteins, in the context of CNS disorders. In addition, the review emphasizes the existing limitations and challenges associated with the use of biomarkers in both clinical practice and research on neurodegenerative diseases. In conclusion, this review provides an insightful overview of the identified biomarkers for neurodegenerative diseases, underscoring the crucial role of biomarker research in combating these debilitating conditions. The article also highlights future challenges related to the implementation of novel biomarkers in clinical practice and trials, thereby contributing to the ongoing efforts to advance the understanding and management of neurodegenerative diseases.

Over the last two decades, immunoglobulin G (IgG) antibodies against myelin oligodendrocyte glycoprotein (MOG), previously thought to be a biomarker of multiple sclerosis (MS), have been shown to cause a distinct disease called MOG antibody-associated disease (MOGAD). MOGAD accounts for approximately one-third of all demyelinating syndromes in children and is the second most common central nervous system (CNS) demyelinating disease after MS. The diagnosis is made by detecting anti-MOG IgG antibodies against the natural MOG antigen, in the presence of compatible clinical and neuroradiological features. However, due to controversies in the methodologies for detecting anti-MOG antibodies and their diagnostic cutoff values, as well as the expanding clinical spectrum, accurate diagnosis may be challenging, at least in a subset of patients. Clinical presentations of MOGAD vary by age; the highest rates are seen in acute disseminated encephalomyelitis in younger children and optic neuritis, myelitis, or brainstem symptoms in older children. Although it was previously thought to be a milder demyelinating disorder and to have a monophasic course in the majority of patients, recent studies have shown that relapses occur in about half of the patients and sequelae develop in a significant proportion of them, especially in those with persistently high antibody titers, leukodystrophy-like magnetic resonance imaging (MRI) lesions, and spinal cord involvement. However, due to the monophasic course in about half of the patients, long-term treatment is not recommended after the first clinical episode but is recommended for patients who experience relapse. Accurate and early diagnosis of MOGAD is essential for proper management and better outcome. This review covers the challenges in the diagnosis of MOGAD in children.

Acute ischemic stroke (AIS) is the leading cause of disability and one of the top causes of mortality worldwide. The current standard of care is reperfusion therapy including intravenous thrombolysis (IVT) and thrombectomy. However, these treatments have limitations as they have a limited therapeutic window. Hence, there is a vital need to develop neuroprotective agents to prevent brain injury, extend the reperfusion window, improve mortality, and reduce disability in AIS patients. Neuroprotective agents work by counteracting the detrimental biochemical and molecular events that result in irreversible ischemic damage. Numerous preclinical studies and clinical trials have been done on different agents. Thus far, all have been definitively unsuccessful in large trials. Currently, there are several challenges in translation from animal studies to human trials. It is important to understand the current evidence as well as past challenges in the development of neuroprotective strategies in AIS in order for a more strategic selection of agents to be studied, improve study designs and thus contribute to the development of effective neuroprotective agents. Newer agents have shown promise in neuroprotection, and human trials are ongoing. In this review, the mechanisms of action of different families of neuroprotective agents were discussed. The evidence for the efficacy of different drugs in each family of neuroprotective agents was also evaluated and the current research landscape in neuroprotection for AIS was summarized. The past challenges and limitations in clinical trials and proposed possible ways to address these issues were highlighted.

Small fiber neuropathy (SFN) is a relatively common, but largely understudied neurological syndrome which has affected the lives of many globally. The common symptoms of SFN include pain, dysesthesia, and autonomic dysfunction, which are caused by damage to small nerve fibers. Due to its heterogeneous nature, SFN causes a multitude of symptoms which makes the disease and its subtypes difficult to diagnose. Furthermore, as the pathophysiology of SFN remains largely enigmatic, no cause is found in around 50% of the cases and these are classified as idiopathic SFN (iSFN). The difficult task of diagnosing SFN, and the even more elusive feat of hunting for the underlying etiology, demands accurate, precise, preferably noninvasive, and affordable tools, or a combination of them. Accordingly, appropriate biomarkers for SFN are needed to stratify patients and develop cause-centered treatments in addition to symptomatic treatments. As peripheral axons grow and repair, identifying underlying causes of SFN and intervening early may spur axonal regeneration in young patients, which can greatly improve their symptoms and improve quality of life. This narrative review aims to objectively highlight functional, histological, and molecular biomarkers to aid clinicians in discerning the diagnostic tests they should use to diagnose, confirm and determine the etiology of SFN. The strengths and limitations of each potential biomarker will be discussed. Clearer diagnostic criteria, guidelines, and work-up for SFN are required for clinicians to better identify the disease in patients presenting with non-specific symptoms.

Myasthenia gravis (MG) is a rare auto-immune neuromuscular junction (NMJ) disorder which is caused by formation of autoantibodies and destruction of NMJ components. The MG diagnosis is based on the symptoms, autoantibodies detection and paraclinical tests. Given that MG patients have so many differential diagnosis and various medication responses, choosing an accurate diagnosis and the therapy plan in MG is challenging. According to the studies, there are the immunologic, genetic, microRNAs, gut microbiome, and other established or newly proposed biomarkers for diagnosis and prognosis of MG. More studies are needed to provide better collection of biomarkers in MG patients and evaluate their role in MG pathology.