The cholesterol is a vital component of cell membranes and myelin sheaths, and a precursor for essential molecules such as steroid hormones. In humans, cholesterol is partially obtained through the diet, while the majority is synthesized in the body, primarily in the liver. However, the limited exchange between the central nervous system and peripheral circulation, due to the presence of the blood-brain barrier, necessitates cholesterol in the brain to be exclusively acquired from local de novo synthesis. This cholesterol is reutilized efficiently, rendering a much slower overall turnover of the compound in the brain as compared with the periphery. Furthermore, brain cholesterol is regulated independently from peripheral cholesterol. Numerous enzymes, proteins, and other factors are involved in cholesterol synthesis and metabolism in the brain. Understanding the unique mechanisms and pathways involved in the maintenance of cholesterol homeostasis in the brain is critical, considering perturbations to these processes are implicated in numerous neurodegenerative diseases. This review focuses on the developing understanding of cholesterol metabolism in the brain, discussing the sites and processes involved in its synthesis and regulation, as well as the mechanisms involved in its distribution throughout, and elimination from, the brain.

Phosphoinositides are membrane phospholipids involved in a variety of cellular processes like growth, development, metabolism, and transport. This review focuses on the maintenance of cellular homeostasis of phosphatidylinositol 4,5-bisphosphate (PIP₂), and phosphatidylinositol 3,4,5-trisphosphate (PIP₃). The critical balance of these PIPs is crucial for regulation of neuronal form and function. The activity of PIP₂ and PIP₃ can be regulated through kinases, phosphatases, phospholipases and cholesterol microdomains. PIP₂ and PIP₃ carry out their functions either indirectly through their effectors activating integral signaling pathways, or through direct regulation of membrane channels, transporters, and cytoskeletal proteins. Any perturbations to the balance between PIP₂ and PIP₃ signaling result in neurodevelopmental and neurodegenerative disorders. This review will discuss the upstream modulators and downstream effectors of the PIP₂ and PIP₃ signaling, in the context of neuronal health and disease.

Altered immunity may have destructive consequences for the integrated central nervous system. This immune response often affects progressive neurodegenerative diseases such as Parkinson’s disease and/or psychiatric disorders such as schizophrenia. In particular, schizophrenia pathogenesis may be mediated by multiple neuro-immune interaction pathways. Gut microbiota might affect the brain and/or immune function. Significant machineries of immunity are commonly affected by the commensal gut microbiota. Therefore, schizophrenia may be connected with the gut-immune system. In addition, the brain and immune systems cooperate on multiple levels. The brain could save several pieces of information about specific inflammation in a body. This immunological memory named “engrams”, also called memory traces, could restore the initial disease state, which may help to explain key features of schizophrenia. Based on this concept, therapeutic strategies for schizophrenia could be the modification of the gut microbiota. Probiotics and/or fecal microbiota transplantation are now emerging as the most promising treatments for the modification. More consideration of the roles of gut microbiota will conduct the further development of immune-based therapeutics for the prevention and/or treatments of psychiatric disorders.

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.

Early in the course of infection, human immunodeficiency virus (HIV) is able to enter the central nervous system where it stablishes a permanent reservoir. Current antiretroviral therapies do not efficiently cross the blood-brain barrier and therefore do not reach the HIV located in the central nervous system. Consequently, HIV infection can often be associated with neurocognitive impairment and HIV-associated dementia. The purpose of this review is to brief the reader into the world of neurological complications arising from HIV infection. Mechanisms by which HIV directly or indirectly impairs the central nervous system are discussed, as well as other factors influencing or contributing to the impairment, and the animal models currently used to perform research on the topic.

Since the identification and cloning of the cannabinoid receptor 2 (CB₂R), several studies focused on the characterization of its physiological and pathological role. Initially, CB₂R was considered as the peripheral cannabinoid receptor due to its detection in the rat spleen and leukocyte subpopulation in humans. Later, CB₂R was identified in different brain regions significantly modifying the landscape and pointing out its role in a wide variety of central physiological functions and pathological conditions. Additional research also detected the expression of CB₂R in neurons, microglia, and astroglia in different brain regions. Indeed, the findings collected to date support a significant function of CB₂R in anxiety, depression, schizophrenia, and additional neuropsychiatric disorders. This review gathers the most relevant literature regarding new advances about the role of CB₂R in a variety of neuropsychiatric conditions, with special emphasis on its potential as a new therapeutic target for the treatment of different psychiatric disorders.

Subarachnoid hemorrhage (SAH) has deleterious outcomes for patients, and during the hospital stay, patients are susceptible to vasospasm and delayed cerebral ischemia. Coronavirus disease 2019 (COVID-19) has been shown to worsen hypertension through angiotensin-converting enzyme 2 (ACE2) activity, therefore, predisposing to aneurysm rupture. The classic renin-angiotensin pathway activation also predisposes to vasospasm and subsequent delayed cerebral ischemia. Matrix metalloproteinase 9 upregulation can lead to an inflammatory surge, which worsens outcomes for patients. SAH patients with COVID-19 are more susceptible to ventilator-associated pneumonia, reversible cerebral vasoconstriction syndrome, and respiratory distress. Emerging treatments are warranted to target key components of the anti-inflammatory cascade. The aim of this review is to explore how the COVID-19 virus and the intensive care unit (ICU) treatment of severe COVID can contribute to SAH.

The autism spectrum disorder (ASD) comprises a series of neurological diseases that share serious alterations of the development of the central nervous system. The degree of disability may vary so that Asperger’s may have a relatively normal life and get positions of responsibility in corporations and even in Governments, whereas other ASD sufferers are fully dependent on caregivers and have serious cognitive deficits. Although the first cases of autism were detected by looking at failures in metabolism, e.g., phenylketonuria, to later identify the faulty gene, today the trend is the opposite, first obtaining the exome and minimizing the look for altered parameters in blood, urine, etc. Cholesterol is key for neural development as it is not able to cross the blood brain barrier. Therefore, any gene or environmental factor that affects cholesterol synthesis will impact early developmental stages eventually leading to a disease within the autism spectrum and/or schizophrenia. This review provides data of the relevance of cholesterol dyshomeostasis in autism spectrum disorders. Determining biochemical parameters in body fluids should help to provide new therapeutic approaches in some cases of autism.

Stroke causes acute neurological deficit which is an important cause of morbidity and mortality. Neurorehabilitation is an important dimension in the management of post-stroke deficits. Spasticity, pain, and neurological deficits are contributors to post-stroke disability. Dry needling (DN) is a technique commonly used in the management of myofascial pain. Recent evidence suggests its efficacy in the management of post-stroke disability. The descriptive review on the use of DN summarises the evidence for the management of post-stroke patients such as spasticity, balance, pain, functional outcome, tremor, and ultrasonographic evidence. The filiform needle is inserted into the target muscle until a local twitch response is obtained. The effects of DN are produced by the local stretch of the spastic muscle and afferent modulation of the reflex arc that decreases the excitability of the alpha motor neuron. The DN reduces muscle spasticity in post-stroke patients. The improved spasticity is translated to better functional outcomes and balance. The procedure is also shown to reduce pain including post-stroke shoulder pain. It is also shown to improve tremors in post-stroke patients. Ultrasonographic evidence of the beneficial effects of DN shows improved measures in the pennate angle and mean muscle thickness. Concurrent use of DN and electrical stimulation improve spasticity, the effect which may be seen for longer periods. DN is emerging as a useful and cost-effective technique in the management of post-stroke patients. The evidence for the use of DN in the management of post-stroke spasticity is high. However, more research is required to assess its efficacy in functional outcomes and other aspects of the stroke.