Age-related and non-age-related changes in 100 surveyed horse brains.
Authors: Jahns H, Callanan J J, McElroy M C, Sammin D J, Bassett H F
Journal: Veterinary pathology
Summary
# Editorial Summary Jahns and colleagues conducted a comprehensive histopathological examination of 100 horse brains (aged 2–25 years) across 46 neuroanatomical sites to characterise the spectrum of age-related and incidental pathological changes present in animals with no clinical neurological signs. Their systematic survey identified a high prevalence of structural findings: vacuolation appeared in 73 cases (affecting neuropil, neuronal cytoplasm, and white matter), perivascular lymphoid infiltrates in 35 cases, and axonal spheroids in 91 cases, with 10 horses showing extensive spheroid populations in the cuneate and gracile nuclei. Clear age-dependent patterns emerged for lipofuscin deposition (97 cases with intraneuronal accumulation, 41 with glial involvement), perivascular hemosiderin (60 cases), and calcium deposits (24 cases), whilst less common but notable findings included Alzheimer type II cells (2 horses) and nonsuppurative meningoencephalitis (1 horse). These findings have significant implications for equine neurological practice: they establish baseline expectations for normal aging processes and incidental neuropathology, which is crucial for pathologists to distinguish genuine disease from age-appropriate or subclinical changes during diagnostic investigation, and they highlight that many histological abnormalities may carry minimal clinical relevance in asymptomatic animals.
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Practical Takeaways
- •Histopathological findings common in normal horse brains should not be automatically interpreted as pathological—normal aging changes can mimic disease and must be correlated with clinical signs
- •Veterinary pathologists need awareness that vacuolation, spheroids, and mineral deposition are frequent incidental findings in equine neurohistology and may not indicate active neurological disease
- •When submitting equine brain samples for diagnostic evaluation, provide detailed clinical history; many histological changes are age-related and non-specific without clinical context
Key Findings
- •Vacuolation in neuropil (73%), neurons (32%), and white matter (31%) occurs frequently in clinically normal horse brains independent of disease
- •Spheroids detected in 91% of brains surveyed, with 10 horses having >10 spheroids in cuneate/gracile nuclei
- •Lipofuscin deposition in neurons (97%) and glia/extracellular spaces (41%) shows statistically significant age-related increase
- •Hemosiderin deposition around blood vessels (60%), calcium deposition (24%), and occasional low-grade inflammation occur in subclinical disease