Exploring the potential of natural history studies for rare neurological diseases

Abstract

Natural history studies provide information on disease progression, pathogenic mechanisms, biomarkers, patient subpopulations, and clinical endpoints that advance our understanding of rare neurological diseases, guide clinical trial design, facilitate patient recruitment, and ultimately improve the diagnosis and management of these conditions1. Natural history studies also enhance patient care by improving diagnostic accuracy, guiding treatment decisions, and facilitating early intervention strategies. Additionally, they provide valuable information for healthcare providers, patients, and caregivers regarding disease prognosis, symptom management, and resources for support and counseling beyond drug development. The rarity and complexity of neurological diseases pose significant challenges to understanding their underlying mechanisms and developing effective treatments. Neurological diseases include a wide range of conditions affecting the central and peripheral nervous systems, including the brain, spinal cord, and peripheral nerves. Many of these diseases are considered rare, and their complexity often makes diagnosis and treatment difficult, further exacerbating the challenges associated with managing these conditions. One of the primary obstacles in addressing rare neurological diseases is the lack of comprehensive data. Due to their rarity, there is often limited information about the natural history, disease progression, and treatment outcomes for many of these conditions. This scarcity of data hinders researchers’ ability to fully understand the underlying mechanisms driving these diseases and to identify effective treatment strategies. The challenges presented by the lack of comprehensive data are complicated. First and foremost, without a clear understanding of the natural history and disease progression, it is challenging to accurately diagnose and predict the course of these conditions in individual patients. This can lead to delays in diagnosis and treatment initiation, resulting in poorer outcomes for patients. Also, the rarity and complexity of these diseases hinder the recruitment of participants for clinical trials, making it difficult to conduct rigorous evaluations of potential treatments. Clinical trial designs must often be adapted to accommodate small patient populations, which can compromise statistical power and limit the generalizability of study findings. The lack of comprehensive data also has broader implications for healthcare policy and resource allocation. Without a clear understanding of the prevalence and impact of rare neurological diseases, policymakers have not prioritized funding for research and treatment initiatives targeting these conditions. This results in disparities in access to care and limited investment in developing new therapies for affected patients. Natural history studies significantly address these challenges through their potential to determine disease progression, characterize patient outcomes, and define genetic relationships2. Since its approval by the Food and Drug Administration (FDA) in 2016, natural history studies have been used to determine treatment strategies for rare neurological diseases such as spinal muscular atrophy, X-linked dystonia-parkinsonism, and Huntington’s disease3,4. It is currently used for drug development, clinical outcome assessment, and biomarker development, all of which are crucial for managing neurological diseases2. An observational cohort study conducted by Nickel et al.5 in 2018 examined 140 patients with late-infantile neuronal ceroid lipofuscinosis type 2 (CLN2) disease. The study indicated variations in the first symptom of the disease, motor-language summary scores, and the median time between the onset of the first disease symptom and death5. The study’s natural history data served as a control for evaluating the use of intracerebroventricular replacement therapy with Intraventricular Cerliponase Alfa for CLN2 Disease, as conducted by Schulz et al.6. The successful findings from this study led to the approval of the use of cerliponase alpha for intracerebroventricular replacement therapy by both the EMA and FDA in 20177. Natural history studies are fundamental in clinical research, particularly in rare neurological diseases. Such studies include the involvement of systemic observations and documentation of the progression of a patient’s disease in the absence of treatment8. These reports serve as a reference to understand the natural course of a disease, therefore providing perceptiveness into its distinct characteristics, heterogeneity, and ultimately trajectory. An advantage of conducting natural history studies is their ability to understand the natural progression of rare neurological diseases, some of which lack comprehensive understanding due to their limited prevalence and scarcity of data9. This attentive monitorization of a patient’s disease from the early stages through its evolution, allows researchers to determine patterns of symptom onset, progression, and severity9. These efforts provide invaluable information for clinicians, researchers, and drug developers as they help in defining prognostic indicators, consequently contributing to the development of more accurate diagnostic criteria. For instance, a study by Bregman et al. demonstrated the potential of using a natural history study to comprehend the pathophysiological processes that occur at the onset of Creutzfeldt-Jakob Disease (CJD) and potential risk factors. This understanding facilitates early diagnosis and the development of safe and efficient methods for managing the disease10. Diseases themselves have enduring value as sustainable models, the most evident is in making a diagnosis4. Natural history studies facilitate the identification of factors that influence disease progression and patient outcomes through the analysis of various demographic, genetic, environmental, and clinical variables. Researchers can utilize these parameters to determine factors that exacerbate or mitigate disease severity, identify appropriate subpopulations with distinct disease trajectories, and tailor treatment strategies appropriately9. This personalized approach is particularly crucial in rare neurological diseases, where heterogeneity among patients is the norm rather than the exception. Despite their profound impact, natural history studies often encounter challenges in securing funding and support. Increased investment in this research is essential to sustain medical progress, refine treatment guidelines, and enhance patient outcomes. Through resource allocation to support these studies, we can deepen our understanding of disease trajectories, pinpoint effective interventions, and personalize treatment approaches, ultimately yielding long-term benefits of saving lives and curbing healthcare costs. Support for natural history studies is imperative in driving medical research forward and improving patient outcomes. Advocating for heightened funding and awareness is key to ensuring these studies receive the necessary resources to make meaningful contributions to healthcare. Tangible actions such as donating to organizations dedicated to medical research funding, participating in clinical trials, and volunteering time and expertise offer avenues for individuals to bolster this cause. Additionally, staying abreast of the significance of natural history research and fostering collaboration with researchers and organizations can further amplify efforts to advance understanding and treatment of various medical conditions. Participating in natural history studies not only yields valuable data but also grants individuals a direct opportunity to contribute to medical research, thereby playing a pivotal role in shaping the future of healthcare and fostering improved treatment options and outcomes for patients worldwide. Overall, the use of Natural History Studies for Rare Neurological Diseases can open up a field of study that could help us understand the neurological processes behind the rare diseases of the central and peripheral nervous system. From these studies, a collection of comprehensive data could provide valuable insights about rare diseases and promote the development of the diagnosis of disease by understanding groups at risk, the creation of medicine/treatment as researchers uncover the neurological structures/functions that are compromised and the support for people that are diagnosed with rare diseases who feel like they have no hope. Natural history studies provide hope for neurologists, neurosurgeons, and patients based on the principle of the natural cause of the disease and understanding the neuroepidemiology of said diseases. Ethical approval Not applicable. Consent Not applicable. Source of funding Not applicable. Author contribution Conceptualization: A.O.M.; writing—original draft: A.O.M.; A.G., A.O.S., S.M., M.T.A., A.T., A.S., P.P.K.; writing—review and editing: A.O.M. Conflicts of interest disclosure The authors declare no conflict of interest. Research registration unique identifying number (UIN) Not applicable. Guarantor Muili Abdulbasit Opeyemi. Availability of data and materials Not applicable. Provenance and peer review Not commissioned, externally peer-reviewed.