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The evolutionary hypothesis of benign paroxysmal positional vertigo
1Dr Han's Neurology Clinic, 1661, Dongseo-daero, Dong-gu, Daejeon 34552, Republic of Korea.
Medical Hypotheses
|November 1, 2019
Summary
Human otoliths, made of calcium carbonate, are vulnerable to low pH, leading to benign paroxysmal positional vertigo (BPPV). This inner ear condition is more common in the morning due to overnight respiratory acidosis.
Area of Science:
- Evolutionary Biology
- Otolithic Physiology
- Vestibular Disorders
Background:
- Human otoliths, unlike skeletal bones (calcium phosphate), are composed of calcium carbonate, reflecting an ancient evolutionary adaptation.
- Vertebrates evolved to use calcium phosphate for bone strength due to risks associated with calcium carbonate at low pH.
- Otoliths, despite their evolutionary history, retain calcium carbonate composition, making them susceptible to dissolution.
Purpose of the Study:
- To investigate the relationship between otolith composition, pH levels, and the occurrence of benign paroxysmal positional vertigo (BPPV).
- To explain the evolutionary persistence of calcium carbonate in otoliths despite its susceptibility to acidic conditions.
- To elucidate the physiological mechanisms linking respiratory acidosis and systemic pH changes to BPPV onset.
Main Methods:
- Comparative analysis of skeletal bone and otolith composition across vertebrate evolution.
- Physiological modeling of pH changes during sleep and their effect on calcium carbonate structures.
- Correlation study between conditions affecting blood pH (e.g., diabetes, gout) and BPPV incidence.
Main Results:
- Otoliths, composed of calcium carbonate, are prone to corrosion in low pH environments, unlike calcium phosphate-based bones.
- Mild respiratory acidosis during sleep leads to decreased blood pH, potentially corroding otoliths.
- Increased incidence of BPPV, particularly in the morning, is linked to overnight otolith dissolution.
- Systemic conditions like diabetes mellitus and gout, which lower blood pH, are associated with a higher occurrence of BPPV.
Conclusions:
- The evolutionary retention of calcium carbonate in otoliths creates a vulnerability to pH fluctuations.
- Nocturnal respiratory acidosis and conditions causing chronic low blood pH significantly increase the risk and morning onset of BPPV.
- Understanding otolith fragility at low pH provides insights into the pathophysiology of BPPV and potential management strategies.
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