Myeliinitys

Myeliinitys is a term used to describe the overall integrity of myelin sheaths along axons in the nervous system. It encompasses the thickness, compactness, continuity, and organization of myelin, as well as the integrity of nodes of Ranvier and internodal segments. While not an established diagnostic category, myeliinitys is used in some scientific discussions to summarize myelin health across neural circuits.

Biological basis: Myelin is produced by oligodendrocytes in the central nervous system and by Schwann cells in the peripheral nervous system. Its integrity depends on proper lipid and protein composition, stable adhesion of lamellae, and maintenance of saltatory conduction. Loss or disruption reduces conduction velocity and fidelity and can lead to conduction failures or signal distortion along affected axons.

Measurement and indicators: In vivo imaging uses myelin-related metrics such as myelin water fraction, magnetization transfer ratio, and quantitative T1/T2 that correlate with myelin content. The g-ratio, a ratio between inner axon diameter and total fiber diameter, is used to assess optimal myelination. Histological methods provide direct assessment in animal or human tissue and are used to validate imaging measures.

Clinical relevance: Decreased myeliinitys is a hallmark of demyelinating diseases like multiple sclerosis and various leukodystrophies, and it correlates with motor and cognitive deficits. Age-related decline in myelin integrity has been reported, contributing to slower processing and reduced neural plasticity. Remyelination capacity varies among individuals and brain regions, influencing disease progression and recovery potential.

Notes: Because myeliinitys is not a standard term, usage varies and it is often replaced by myelin integrity or myelin health in formal work. The concept remains useful as a shorthand for the functional consequences of myelin integrity on neural conduction and timing.