The asynchronous progression of stria vascularis (SV) atrophy and spiral ganglion neuron (SGN) loss is the central puzzle in presbycusis. Current models treat these as parallel degenerations sharing root causes (oxidative stress, inflammation), but fail to explain why SGN loss often accelerates after significant SV decline. Here I propose a causal priming mechanism: early, localized aldosterone deficiency in the cochlear lateral wall directly reduces NKCC1 expression and endocochlear potential (EP), creating a chronic, mild metabolic stress in the SGN somata housed in Rosenthal's canal. This stress doesn't kill neurons but primes them by chronically upregulating activity of T-type CaV3.2 calcium channels as a compensatory attempt to maintain excitability. The neuron's calcium handling system is thus pushed toward a higher baseline, leaving it hypersensitive to any secondary insult—glutamate excitotoxicity, age-related increases in ambient glutamate, or stochastic inflammatory signals. This two-hit model explains the temporal disconnect: SV decline (Hit 1) establishes a vulnerable metabolic niche, while later-life triggers (Hit 2) rapidly deplete the compromised SGN population.

Novel mechanistic reasoning beyond the literature: The aldosterone-SGN survival link [https://www.aging-us.com/article/101045/text] is currently framed as a direct neuroprotective effect. I propose its primary role is indirect, via SV-mediated metabolic priming. The preserved SGNs seen with CaV3.2 blockade [https://pubmed.ncbi.nlm.nih.gov/21640179/] support this—the drug isn't just blocking a death pathway but counteracting a pre-existing, systemically elevated calcium influx state. The known SV ion transport pathology (NKCC1/Na-K-ATPase downregulation) would subtly lower the cochlear potential gradient, reducing the driving force for potassium recycling and forcing SGNs to work harder for depolarization. This increased workload could homeostatically increase CaV3.2 expression, a channel linked to neuronal excitability and, in high flux, to apoptotic signaling.

Testable predictions:

1. Temporal Causality: In longitudinal studies of aging mice (e.g., C57BL/6), early SV aldosterone/NKCC1 decline (measured via spatial transcriptomics) will correlate with subsequent increases in CaV3.2 channel protein in adjacent SGNs, prior to significant neuronal loss.
2. Metabolic Niche Signature: Spatially-resolved metabolomics of Rosenthal's canal will show a specific signature (e.g., altered ATP/ADP ratios, pH shifts) in aged cochleae with intact SGNs but atrophic SVs, absent in models where SGNs are lost directly (e.g., ototoxins).
3. Intervention Window: Early administration of a mineralocorticoid receptor agonist (e.g., fludrocortisone) to maintain NKCC1 expression in the SV should prevent the later CaV3.2 upregulation in SGNs, even if systemic oxidative stress continues. Conversely, late-stage intervention after CaV3.2 priming would be ineffective, requiring direct channel blockade.

This hypothesis shifts the focus from parallel pathologies to a sequential, causally-linked cascade. It predicts that preserving SV function in midlife isn't just about maintaining EP for hair cells, but about preventing a slow, silent rewiring of SGN calcium homeostasis that makes them ticking time bombs. The unified intervention target is thus early aldosterone signaling, not just late-stage calcium or apoptosis blockers.