Auditory brainstem nuclei in Alzheimer's disease

Area of Science:

• Neuropathology
• Neuroscience
• Auditory Neuroscience

Background:

• Alzheimer disease (AD) is a progressive neurodegenerative disorder.
• AD is characterized by the accumulation of amyloid plaques and neurofibrillary tangles.
• The distribution of AD neuropathology in the brainstem auditory pathways is not well-defined.

Purpose of the Study:

• To investigate the presence and distribution of Alzheimer disease neuropathological hallmarks in the brainstems of affected individuals.
• To identify specific auditory nuclei within the brainstem that are affected by plaque and tangle formation.

Main Methods:

• Examination of serial sections from 7 Alzheimer disease brainstems.
• Histopathological staining using Kongo red and silver stains to identify plaques.
• Counterstaining with Nissl dye for cytoarchitectural analysis.

Main Results:

• Significant plaque formation was observed in the central nucleus and dorsomedial nucleus of the inferior colliculus.
• Plaques were also present to a lesser extent in the deep layers of the dorsal cortex of the inferior colliculus.
• Neurofibrillary tangles were rarely found, primarily in the dorsal cochlear nucleus, periolivary region, ventral nucleus of the lateral lemniscus, and central nucleus of the inferior colliculus.

Conclusions:

• The inferior colliculus is a primary site for plaque deposition in the auditory brainstem of Alzheimer disease patients.
• Other auditory brainstem nuclei appear largely spared from neuritic plaque formation.
• The findings contribute to understanding the topographical spread of Alzheimer disease pathology within the central nervous system.