Analysis of Fascicular Structure and Connective Tissue Sheaths in Sural Nerve during Aging

Abstract

The aim of our study was to analyze the changes of connective tissue sheaths of epi-, peri-and endoneurium of sural nerve during aging.The study was conducted on sural nerve samples of 10 cases aged 9-80 years. The specimens were embedded in paraffin using standard procedures, after which 5-μm-thick crosssections of nerve trunks were made and stained using Masson's trichrome staining. After morphological analysis of fascicular structure and connective sheaths of the nerve, morphometric analysis was conducted using the software for digital image analysis "ImageJ". Each investigated case was analyzed for total neural, epineurial and fascicular cross-section area, mean values of perineurial index, volume density of myelinated axons and of endoneurial content. To test the difference in mean values for statistical significance we used the Student's T-test for small independent sample.The number of fascicles was 5-13, while the majority of the nerves had less than 10 fascicles. Fascicular structure, which included the number of fascicles and epifascicular/fascicular area ratio, did not show significant changes during aging. Perineurial thickness /fascicle size ratio statistically significantly increased in the older investigated group (p<0.05). Myelinated fibres were of smaller diameter, with more irregular form and markedly less frequent in older cases. Quantitative analysis showed statistically significant decrease in volume density of myelinated fibres in the older group.As results of applied investigation methods we found thickening of perineurial sheath of sural nerve during aging, as well as endoneurial fibrosis. Future investigations of age-related changes should focus on analysis of the components of extracellular matrix within perineurium and endoneurium.

Age protects from harmful effects produced by chronic intermittent hypoxia

“…A and B , right panel) and its increase with the time of digestion correlates very well with the description that the epineurium and perineurium thickness increase with age as well as with perineurial thickness/fascicle size ratio (Kundalic et al . ; Campbell et al . ).…”

Peer Review #3 of "Median nerve behavior at different wrist positions among older males (v0.1)"

“…The process of peripheral nerve degeneration is associated with the phenomenon of the loss of nerve fibers (Kerasnoudis et al, 2013). Furthermore, peripheral nerve morphological studies suggested that aging causes a reduction in the percentage of myelinated axons while increasing the epineural and fascicular areas, with a larger neural cross-sectional area observed in the elderly group (Kerasnoudis et al, 2013;Kundalić et al, 2014). The mean MNCSA value in young adults and the elderly group (>60 years old) were 8.75 mm² and 9.12 mm², respectively (Kerasnoudis et al, 2013).…”

“…Morphometric studies of the peripheral nerve have indicated the quantitative and qualitative changes that occur during the aging process, such as an increased CSA and thickening of the peripheral nerve sheath of a peripheral nerve (Kundalić et al, 2014;Topp & Boyd, 2006). The thicker epineurium in older adults, which may explain their larger MNCSA, may affect the biomechanical properties of a nerve owing to the stress imposed on the nerve during joint movement.…”

Características Morfométricas de las Raíces del Plexo Braquial en el Hombre

“…Durante el envejecimiento normal, no se produce la pérdida de las células nerviosas, la pérdida neuronal se limita a regiones restringidas del sistema nervioso y es probablemente no más del 10 % (Bonnel, 1984). Sin embargo, se ha reportado deterioro de características morfológicas y funcionales del sistema nervioso periférico asociados al envejecimiento (Kundalic et al, 2014), que se conocen como cambios degenerativos en la estructura del axón y el tejido conectivo que cubre el nervio (Bahcelioglu et al, 2008). Por otra parte, diversos tipos de déficits funcionales pueden ser la consecuencia de una pérdida de fibras nerviosas, anormalidades de la mielina y alteraciones en el tejido conectivo y en la vascularización (Ceballos et al, 1999).…”