Abstract Neurodegenerative diseases are characterized by progressive neuronal loss and represent a growing global health burden. Early diagnosis and accurate disease monitoring remain major clinical challenges, as pathological changes often precede overt symptoms by several years. Advanced neuroimaging techniques, particularly magnetic resonance imaging (MRI) and positron emission tomography (PET), have emerged as key sources of imaging biomarkers capable of capturing structural, functional, metabolic, and molecular alterations associated with neurodegeneration. A systematic literature search was conducted across PubMed/MEDLINE, Scopus, and Web of Science from inception to the final search date. Eligible studies included original human research evaluating MRI- and/or PET-based imaging biomarkers in neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, dementia with Lewy bodies, and amyotrophic lateral sclerosis. Data extraction focused on imaging modalities, biomarkers assessed, clinical applications, and outcomes related to diagnosis and disease progression. Methodological quality and risk of bias were assessed using QUADAS-2 for diagnostic accuracy studies and design-appropriate criteria for longitudinal and prognostic studies. A qualitative narrative synthesis was performed due to methodological heterogeneity. Across the included studies, MRI- and PET-based biomarkers demonstrated complementary roles along the neurodegenerative disease continuum. Structural MRI markers, such as regional brain atrophy and cortical thinning, were consistently associated with disease severity and longitudinal progression, while diffusion and functional MRI detected microstructural and network-level alterations at earlier stages. PET imaging revealed disease-specific metabolic and molecular patterns, with FDG-PET identifying characteristic hypometabolism and amyloid-β and tau PET enabling in vivo detection of pathological protein deposition before clinical symptom onset. Multimodal MRI–PET approaches improved diagnostic accuracy and prognostic stratification compared with single-modality analyses. However, substantial heterogeneity in imaging protocols, analytical methods, and study populations was observed. MRI and PET provide robust and complementary imaging biomarkers for early detection and disease monitoring in neurodegenerative diseases. While PET biomarkers are particularly sensitive to early molecular pathology, MRI markers are well-suited for longitudinal tracking of neurodegeneration. Integration of multimodal imaging within standardized frameworks may enhance clinical translation, improve patient stratification, and support precision medicine approaches in neurodegenerative disorders. Further large-scale, harmonized longitudinal studies are required to validate and standardize imaging biomarkers for routine clinical use.

Huntington's disease (HD), also known as Huntington's chorea, is a fatal neurodegenerative disease that is usually inherited. It typically presents as Huntington's disease (HD), also known as Huntington's chorea, is a fatal neurodegenerative disease that is usually inherited. It typically presents as a triad of progressive psychiatric, cognitive, and motor symptoms. The earliest symptoms are often subtle problems with mood or mental/psychiatric abilities, which precede the motor symptoms for many people. The definitive physical symptoms, includi A physical examination, sometimes combined with a psychological examination, can determine whether the onset of the disease has begun. Excessive unintentional movements of any part of the body are often the reason for seeking medical consultation. If these are abrupt and have random timing and distribution, they suggest a diagnosis of HD. Cognitive or behavioral symptoms are rarely the first symptoms diagnosed; they are usually only recognized in hindsight or when they develop further. How far the disease has progressed can be measured using the unified Huntington's disease rating scale, which provides an overall rating system based on motor, behavioral, cognitive, and functional assessments. Medical imaging, such as a CT scan or MRI scan, can show atrophy of the caudate nuclei early in the disease, as seen in the illustration to the right, but these changes are not, by themselves, diagnostic of HD. Cerebral atrophy can be seen in the advanced stages of the disease. Functional neuroimaging techniques, such as functional magnetic resonance imaging (fMRI) and positron…