Ultrastructural changes with age in the human superior laryngeal nerve

Area of Science:

• Neuroscience
• Gerontology
• Anatomy

Background:

• The superior laryngeal nerve controls laryngeal function, crucial for swallowing and voice production.
• Age-related changes in nerve structure can lead to sensorimotor dysfunction in the upper aerodigestive tract.
• Understanding these changes is vital for addressing geriatric health issues.

Purpose of the Study:

• To investigate age-related structural alterations in postmortem human superior laryngeal nerves.
• To quantify the loss of myelinated nerve fibers and their axonal diameters in relation to age.
• To correlate observed nerve changes with known age-related functional deficits.

Main Methods:

• Electron-microscopic morphometric analysis of human superior laryngeal nerves from young adult (20-30 years) and old (60+ years) individuals.
• Statistical comparison of myelinated nerve fiber counts and axonal diameters between age groups.
• Selective analysis of small myelinated fibers (1-2 microns) and small axonal diameters (0-0.5 microns).

Main Results:

• A statistically significant 31% decrease in myelinated nerve fibers was observed in older adults compared to young adults.
• A substantial 67% loss of small myelinated fibers (1-2 microns) was detected in the elderly group.
• A significant 67% reduction in small axonal diameters (0-0.5 microns) was found in older individuals.

Conclusions:

• Significant age-related loss of myelinated nerve fibers occurs in the human superior laryngeal nerve.
• The loss is particularly pronounced in small myelinated fibers and those with small axonal diameters.
• These histomorphologic changes likely contribute to age-related sensorimotor dysfunction of the upper aerodigestive tract.