Neurological Disorders: Epidemiology, Pathophysiology, and Rehabilitation

INTRODUCTION

The wide variety of illnesses affecting any part of the nervous system is referred to as neurological disorders. Numerous factors, including trauma, infections, degeneration, structural flaws, tumors, disruptions in blood flow, autoimmune illnesses, and more, can lead to these disorders. Meningitis, Parkinson's disease, Alzheimer's disease, epilepsy, multiple sclerosis, stroke, and ALS are a few frequent neurological conditions. Neurological illnesses can present with a variety of symptoms, such as headaches, tremors, seizures, migraines, muscle weakness, vision abnormalities, memory loss, and coordination challenges. Neurologists, psychologists, psychiatrists, neurosurgeons, physical therapists, and occupational therapists are among the healthcare professionals who play critical roles in diagnosis, treatment, and rehabilitation when managing neurological illnesses (Organization, 2016). Globally, a considerable number of individuals suffer from neurological illnesses, which play a significant role in both death and disability (Carroll, 2019).

Global Prevalence and Disease Burden

According to contemporary estimates, billions of people are thought to be affected by neurological illnesses, which are frequently linked to diminished everyday functioning and have a detrimental effect on QoL, given their increasing impact on disability and death globally, particularly in low- and middle-income nations (Feigin et al., 2020). Most of the neurological patients report varying degrees of difficulty with motor, sensory, intellectual, and visual ability; as a result, they have substantial functional limits when it comes to engaging in daily activities, participating in society, and interacting with others (Padovani & Pilotto, 2020). Parkinson's disease, stroke and multiple sclerosis (MS)  account for almost 58% of central neurological illnesses that result in disability-adjusted life years (Organization, 2006). Worldwide health is heavily impacted by neurological illnesses. Current estimates indicate that 3% of global disease burden is attributed to neurological diseases comprised in the GBD Study. These disorders include migraine, Parkinson’s disease, medication-overuse headache, multiple sclerosis, epilepsy, and dementias related to Alzheimer's and other dementias. Even if the aggregate percentage may appear low, the top 50 causes of DALYs include stroke, migraine, epilepsy, and dementia (Murray et al., 2013). Over the next decade, it is anticipated that the neurological burden of disease will increase dramatically in LMICs (Ojaghihaghighi et al., 2017).

Numerous sources list multiple sclerosis, Parkinson's disease, epilepsy, strokes, Alzheimer's and other dementias, migraines, and seizures as some of the most prevalent neurological conditions. Millions of individuals worldwide are impacted by these problems, which can be brought on by a variety of variables, including age, lifestyle, infections, genetics, and traumatic brain injuries. In order to acquire the proper diagnosis and treatment for these conditions, it is critical to comprehend their symptoms. Progressive neurological diseases are conditions in which there will be a continuous decline in operational capabilities. This process may be incremental over decades, or even centuries, or shorter and quicker than weeks and months. These disorders are lifelong issues affecting the ADLs (Fieo et al., 2018). A person with progressive neurological disorders experiences a steady decline in their neurological function. The person will probably live with these conditions. The degradation could happen quickly over a few weeks or months, or it could happen gradually over many years. Progressive neurological disorders frequently manifest as MND, MS, PD, or AD. Progressive neurological diseases, including MS, PD, and Huntington’s disease, have a profound impact on the lives of patients, as well as those who are close to them (Aarsland et al., 1999). Neurodegenerative or demyelinating invalidity-causing diseases cause chronic progressive symptoms, sometimes in the young and working-age. This pattern may be the result of a pathological process with variable progressive combinations, which includes movement, cognitive and emotional elements as well as behavioural abnormalities (Hussain et al., 2013).

OVERVIEW OF NON-PROGRESSIVE NEUROLOGICAL DISORDERS

Stroke / Cerebrovascular Disease

A stroke is a disorder caused by a disturbance in the blood flow to a region of the cerebral cortex, either by an ischemic stroke or a hemorrhagic stroke. A stroke is sometimes referred to as a brain attack or cerebrovascular accident. The disruption of the blood supply causes the brain's vascular region to lose nutrients and oxygen, which damages the brain's cells. A TIA is a reversible neurological disability that can occasionally result from a momentary blockage of a blood vessel. Although stroke is diagnosed clinically, brain imaging is necessary to differentiate between hemorrhagic and ischemic stroke. In cases where imaging is not available, patients with intracerebral hemorrhage may be identified using clinical scoring (Ojaghihaghighi et al., 2017).

About 70% of strokes worldwide are caused by ischemia, 27% by bleeding, and 3% have an unknown etiology. Cardioembolic causes account for about 25% of all ischemic strokes; this percentage is higher in younger people. Hemorrhagic strokes make up a higher percentage of all strokes in various regions of the world, such as China and Japan. In these two countries, the percentage ranges from 17.1 to 39.4 percent. Not all regions in the world have comparable data. Due to the difficulty in identifying the cause of death, mortality statistics are also likely to be underestimated. The stroke prevalence in India is 203 per 100,000 people over the age of 20. The men to women ration were one to seven. In China estimated incidence of stroke adjusted for age is 117/100,000 people. According to the risk factors for CVD and stroke, they are comparable in general. Furthermore, if risk factors are not controlled following the initial attack, there is a comparable likelihood of a recurrent stroke. Stroke mortality rates are greater in women, even though stroke is more common in men. Additional risk factors include diabetes and poor glucose tolerance, smoking, ambient tobacco smoke exposure, dyslipidemia, atrial fibrillation, sedentary lifestyle, excessive alcohol intake, elevated homocysteine levels, hemostatic factors, drug abuse, and pre-existing CVD. Rheumatic heart disease is a key contributing factor to embolic stroke in underdeveloped nations. As rheumatic fever is controlled, the significance of this risk factor is decreasing. Among remote places where home deliveries are common, dehydration among postpartum women can result in strokes. The cerebrovascular disease sequelae, cerebral infarction, subarachnoid hemorrhage, and intracerebral hemorrhage are all included in the BOD estimations for stroke. According to Mathers, there are 72,024,000 DALYs associated with cerebrovascular illness, with roughly equal burdens for men (35,482,000) and women (36,542,000). Due to aged populations and greater exposure to significant risk factors, health professionals predict that the number of stroke incidents will rise, especially in emerging nations (Feigin et al., 2016).

OVERVIEW OF PROGRESSIVE NEUROLOGICAL DISORDERS

Multiple Sclerosis

Multiple sclerosis is the most common non-traumatic illness that disables young people. Both the economic effects of MS and its prevalence are increasing globally. Even though the exact cause of MS and the mechanisms causing its rise are still unknown, complex gene-environment interactions certainly play a major role. The epidemiology of MS indicates that the following risk factors may contribute to the illness's development: smoking, low blood vitamin D levels, overweight or obese children, and Epstein-Barr virus infection. The common belief that MS has no recognized cause is entirely accurate. In addition to an individual's genetic background, EBV, sunlight (UVB), smoking, and vitamin D all have a significant impact on the causative pathway leading to the development of MS (Ramagopalan et al., 2010).

According to traditional views, the disease progresses in two stages: Secondary and main progressive MS, or non-relapsing progression, is caused by delayed neurodegeneration and early inflammation causes relapsing-remitting MS (Coles et al., 2006). We still don't know the underlying cause. MS is a complex disease; apart from several proven environmental factors, such as smoking, obesity, Epstein-Barr virus (EBV) infection, vitamin D or UVB exposure, and vitamin B12, several genes marginally increase the risk of acquiring the condition (Ascherio, 2013). It was once thought that T cells, which are specialized to particular organs, mediated the autoimmune disease known as multiple sclerosis. But the effectiveness of B-cell targeted treatments calls into question long-held beliefs about T-cell autoimmune illness (Greenfield and Hauser, 2018). Although the frequency of MS rises with latitude, the trend is declining in the two investigated nations, Norway and the USA (Koch-Henriksen and Sørensen, 2010). Sunlight-induced cutaneous vitamin D (vit D) synthesis is substantially linked with the MS prevalence latitudinal gradient. Low levels of vit D, a decrease in vit D consumption, a decrease in outdoor exercise, and an increase in MS susceptibility linked to genetic variants that result in low levels of vit D have all linked to the causative pathway of MS (Sintzel et al., 2018).

Historically, women have been more likely than men to get MS. Almost equal sex ratios were found in case series of the early 1900s. In the majority of affluent nations today, the sex ratio has been rising gradually since then and is almost at 3:1 (F: M) (Orton et al., 2006). It is possible to account for up to 40% increased incidence of MS in women aged 20 by smoking, which raises the risk of MS by about 50%. Women did not smoke in large numbers before the WW2, but after the war, this changed quickly, reflecting the rising MS incidence among women in their 20s (Palacios et al., 2011). It has been hypothesized that organic solvents (Napier et al., 2016) smoked tobacco (Handel et al., 2011), but not the oral tobacco or snuff, are linked to MS. This may be because these agents present antigens in the lungs, which leads to post-transplantation alterations. MS risk modification most likely starts in utero at 10 and continues throughout life (Hedström et al., 2009). It is unclear if shared environmental factors, epigenetic mechanisms, or both are responsible. Eight out of ten people have a family history of MS, suggesting that MS susceptibility is inherited (Kobelt et al., 2017). MS is becoming more widespread in both developed and developing countries. The prevalence of multiple sclerosis is rising worldwide (Browne et al., 2014).

Parkinson's Disease

Bradykinesia, cogwheel rigidity, resting tremor, impairment of postural reflex and favorable response to dopaminergic medication are the characteristics of Parkinson's disease. Other rare hereditary types and less common neurodegenerations involving several systems or large striatal lesions (e.g., PSP or MS atrophy) are examples of other unique kinds of Parkinsonism. Secondary Parkinsonism is the term used to describe Parkinsonism that results from exogenous causes, such as carbon monoxide or manganese toxicity, although these cases are now uncommon. These illnesses will not be segregated here since the patient burden from them is comparable to or higher than that from PD and because there is no evidence to support the inclusion of these conditions separately. PD has an enigmatic cause. There isn't a single known environmental risk factor. Less than 10% to 15% of instances are pure genetic types. Global risk factors include growing older and being male. There have been reports linking PD risk to exposure to chemicals, head trauma, recurrent infections, high-animal-fat diets, and midlife obesity; however, none of these associations are sustained. The most reliable correlation shows an inverse relationship between coffee intake and cigarette smoking, suggesting a preventative impact (Singhal & Khadilkar, 2014).

Alzheimer's Disease

A decline in cognitive abilities, including intellectual function, which is severe enough to affect social or vocational functioning, is known as Alzheimer's disease. While differentiating AD from other dementia causes is crucial, especially when treating with cholinergic terase inhibitors, the burden associated with all dementia causes is the same. Over 100 studies on the prevalence of AD and other dementias have been published worldwide. It has been observed that the prevalence of dementia often doubles every five years as people age. Research carried out in nations that practice dementia has revealed a prevalence that ranges from 084 to 350 percent. Family AD with an early beginning is associated with three distinct genes (APP, PSI, and PS2). For non-familial, late-onset instances, the gene (APO E4) is a risk factor (Henderson and Jorm 2000). Large-scale research has suggested the existence of other genes, but has not proven it (Singhal & Khadilkar, 2014).

The hippocampus, amygdala, and entorhinal cortex are the three areas of the medial temporal lobe that are commonly affected by atrophy in AD. These areas are responsible for episodic memory and learning impairment that affects day-to-day functioning. The authors examined several studies to support this theory and discovered notable variability in the areas of brain damage in the preclinical AD. AD is typically diagnosed clinically because a definitive diagnosis cannot be made until after an autopsy. The most trustworthy indicators are typically behavioral and cognitive symptoms of the diseases; it is not advised to overuse or interpret laboratory results, especially those from CT and MRI scans, too much. According to the Alzheimer's Association (2006), there is variation in the estimates of AD; however, research consistently indicates that AD is the most prevalent kind of dementia. The biggest risk factor for Alzheimer's is getting older. Research indicates that 2% of people are affected by the illness at age 65, and that prevalence doubles every five years as people become older, reaching 33% or higher in 85-year-olds. People who are 85 years of age or older will be diagnosed with AD, particularly if a first-degree relative has had the disease in the family. In Sweden, 55% of women and 37% of men over the age of 95 were diagnosed with dementia, according to a recent study on the condition's prevalence (Braun, 2008).

Motor Neuron Disease (MND)

During the 1800s, Scientists studying neurology discovered that muscle loss could arise from fundamental muscle disorders or secondarily from loss of neurological and muscular integrity, which occurs when motor neurons deteriorate or when peripheral nerves are severed. Moreover, it was found that certain types of motor neuron degeneration target only the lower or higher motor neurons. Charcot & Joffroy (1869) termed the condition that results from both upper and UMN & LMN dysfunction ALS. The etiology of MND, often known as ALS, is uncertain. Few patients with familial ALS have clear genetic inheritance, but understanding the biochemical underpinnings of genetic subgroups is also yielding valuable knowledge that could help develop treatments for the disease's sporadic forms. When no treatment can cure the condition or modify it, the management strategy must be multidisciplinary and supportive. Future treatments for MND may combine molecular-based therapies with stem cell grafts to restore cellular integrity, if it becomes apparent that complex genetic and environmental variables contribute to the onset of the illness (Talbot, 2002).

When it shows signs of both spinal and cerebral involvement in its normal form, the diagnosis is mostly evident. A combination of asymmetrical limb weakness and wasting with clinical indicators of corticospinal tract injury (extensor plantars, elevated tone, and brisk reflexes) accounts for around 85% of all cases of MND. These symptoms usually appear gradually over months. A quick jaw jerk, dysphagia, dysarthria, tongue wasting, and foot drop are common initial symptoms of the condition. It can also present as a variety of bulbar and corticobulbar symptoms. The latter ailment has a bad prognosis and is more common in women post the age of fifty. When a neurologist examines the patients, the majority of them show indications of more diffuse motor involvement despite this apparent localized onset. When there is a clinically discernible sensory involvement, one should be suspicious of a different diagnosis, like an inflammatory neuropathy. When diffuse fasciculation is present alone, as it frequently is in a nervous patient with rapid reflexes, it increases the possibility of ALS, but in most cases, benign fasciculations are the cause. In normal ALS, the sphincter and extraocular muscles are spared. Approximately 3% to 5% of ALS patients exhibit clinical signs of dementia, with an affinity for executive function impairments (Hosler et al., 2000; Kuzuhara et al., 2001).

In pure LMN syndromes, 10% or fewer of patients do not have involvement of the upper motor neurons at presentation. When higher motor neuron symptoms like brisk reflexes or extendor planters become noticeable, it can be more challenging to make the diagnosis of ALS in the absence of usual symptoms. A definitive diagnosis can usually be obtained when the disease progresses over months at the same pace as ALS. In general, progressive muscular atrophy, the name for MND appearing as a pure lower motor neuron disease, progresses more slowly than ALS. There are regional variations that only affect the upper or lower limbs, respectively. Sometimes, myasthenia gravis is mistakenly identified as ALS when the patient has major bulbar weakness (Hu et al., 1998). In pure UMN syndromes, the main characteristics of primary lateral sclerosis are as follows: a 3:1 ratio M: F; symmetrical progression of spastic tetraparesis and pseudo-bulbar palsy (patients sounded like they have a hot potato in their mouths); notable emotional instability that typically doesn't impede cognitive function (Le Forestier et al., 2001, Pringle et al., 1992).

Progressive Supranuclear Palsy

One tau protein aggregation disorder is progressive supranuclear palsy. A third of patients have a phenotype similar to Parkinson's disease, indicating that its clinical spectrum is greater than previously thought. PSP patients have the characteristic bradykinesia, which includes other incapacitating brainstem abnormalities, erect posture with nuchal stiffness, disproportionate postural instability, and frontal behavioral and cognitive alterations. Prevalence for active PSP cases is roughly 5.6 cases per 100,000 (Schrag et al., 1999). Merely 1.5 out of every 100,000 have an appropriate diagnosis at this point (Bower et al., 1997). The wide range of anatomical and neurochemical regions of the CNS that are damaged by progressive supranuclear palsy is noteworthy. The most common and severe neurotransmitter-related problems in PSP are impairments to the cholinergic system in different sites and impairment of the dopaminergic nigrostriatal pathway (Ruberg et al., 1985). The latter affects the cerebral cortex, especially the premotor and primary motor regions (Hauw et al., 1990). Moderate impairment of striatal, globus pallidus interna, and globus pallidus externa GABAergic function contributes to the pathophysiology of motor parkinsonism in PSP (Levy et al., 1995). Not like in PD, but normal in the basal ganglia, serotonergic receptor sites are diminished in the cortex. Severe injury to the locus ceruleus results in a generalized loss of adrenoceptors (Pascual et al., 1993). Unlike with PD, mesolimbic and mesocortical dopaminergic systems, as well as peptidergic systems, remain intact.

OVERVIEW OF NEURO-REHABILITATION

The growing body of research indicates that rehabilitation is the most efficient means of minimizing impairment and a crucial component of managing neurological diseases (Miyamoto et al., 2022). The aim of neurological rehabilitation can be to enhance QoL and postural stability (Nielsen et al., 2015). Rehabilitation programs can lessen the effects of disabilities brought on by neurological disorders in addition to promoting, preventing, and treating them (Marge, 1988). It is well acknowledged that the key to preventing long-term dependency and disability is through rehabilitation (Winstein et al., 2016). Rehabilitation medicine has grown significantly as a component of contemporary medicine across the globe thanks to the combined advancement of national policy, funding, and technology (Scrutinio et al., 2019). People with such challenges may be eligible for a variety of rehabilitation programs designed to enhance their capacity for everyday tasks and boost their social engagement (Tieri et al., 2018). The goal of research on neurorehabilitation is to find interventions that enhance the level of health for the patient. Therefore, it is necessary to accurately characterize the active elements that are responsible for the observed improvement. It also helps the community to compare the results of various studies when the fundamental concepts of rehabilitation are clearly defined. In case neuroscientific research aims to figure out neurological alterations in the brain following a stroke from behavioral alterations, this is very crucial. Our goal in compiling the neuroscientific material on learning in humans and animals that may be useful for rehabilitation therapy and the healing process is to bring it together in this chapter. As a combination of the ideas that might make up a successful neurorehabilitation strategy, it can help researchers and clinicians. Following a computerized search, 15 learning principles were found based on previously published research. These consist of: multimodal stimulation, rhythmic cueing, modulating effector selection, reaction observation/embodied practice, and social interaction. Discuss trials that effectively applied these guidelines, provided data from both clinical and experimental research. As a result, the ideas presented here should direct the creation of novel technology-based rehabilitation techniques in addition to being applicable to real-world treatments (Maier et al., 2019).

CONCLUSION

Neurological disorders represent a growing global health challenge with profound individual and societal consequences. Understanding their epidemiology and pathophysiology is essential for effective management. Neurorehabilitation plays a pivotal role in reducing disability, enhancing functional independence, and improving quality of life. Therefore, technology may accompany patients during various phases, assisting in the establishment of a formal pathway. Patients living in rural and isolated locations would benefit most from this strategy. Continued research and investment in rehabilitation science are crucial to meeting the evolving needs of individuals living with neurological disorders.