Calcium to magnesium ratio predicts three-month Bell’s palsy recovery in prospective cohort

Adults with Bell’s palsy whose blood shows a higher ratio of calcium to magnesium before starting treatment are markedly more likely to still have visible facial weakness three months later, according to a prospective cohort study published in BMC Neurology. The single-centre study followed 149 adults with idiopathic Bell’s palsy and found that the albumin-corrected serum calcium to magnesium ratio, measured before corticosteroid therapy began, independently distinguished patients who recovered well from those whose recovery was delayed or incomplete.

Bell’s palsy is the most common cause of acute peripheral facial paralysis, and while most patients recover satisfactorily, roughly 30 percent experience delayed or incomplete recovery, with significant functional and psychosocial consequences. Magnesium has a neuroprotective effect and acts as a physiological antagonist of calcium, but the calcium-magnesium balance had not previously been investigated in Bell’s palsy.

In the study, serum calcium, magnesium and albumin levels were measured in all 149 participants before corticosteroid therapy was initiated. Corrected calcium was calculated from the measured total calcium, and the calcium to magnesium ratio was determined in both mass-based and molar units. Recovery was graded on the House-Brackmann scale, with delayed recovery defined as a score above grade II at the third month. At three months, 77 patients (51.7 percent) had achieved favourable recovery, meaning a House-Brackmann grade of II or better, while 72 patients (48.3 percent) had unfavourable recovery.

The corrected calcium to magnesium ratio was significantly higher in the unfavourable recovery group, with a median of 4.80 (interquartile range 4.53 to 5.09) compared with 4.31 (4.06 to 4.51) in those who recovered well; the difference was statistically significant at P < 0.001. In receiver operating characteristic analysis, the corrected ratio discriminated unfavourable recovery with an area under the curve of 0.846 (95 percent confidence interval, 0.784 to 0.902). It performed significantly better than corrected calcium alone (difference in area under the curve, 0.175; DeLong P < 0.001) and than magnesium alone (difference, 0.085; P = 0.003). At the Youden-optimal cutoff of 4.39, the ratio showed a sensitivity of 90.3 percent and a specificity of 66.2 percent for identifying patients destined for unfavourable recovery.

The ratio also held up in multivariable logistic regression. After adjustment, the corrected calcium to magnesium ratio remained independently associated with unfavourable recovery at three months, with an adjusted odds ratio of 8.84 per one standard deviation increase (95 percent confidence interval, 4.08 to 19.15; P < 0.001). In other words, each standard deviation rise in the pretreatment ratio was associated with nearly a ninefold increase in the odds of still having a House-Brackmann score above grade II at the third month, in this cohort.

The authors conclude that a higher pretreatment albumin-corrected serum calcium to magnesium ratio was independently associated with unfavourable recovery at three months in Bell’s palsy and demonstrated significantly better discrimination than corrected calcium or magnesium alone. They describe the ratio as a promising and readily available prognostic biomarker, while stressing that external validation is required before clinical adoption. The study was conducted at a single centre, and as an observational cohort it establishes an association rather than a causal effect of the electrolyte balance on nerve recovery; the reported sensitivity and specificity derive from the same dataset used to identify the optimal cutoff, which typically inflates apparent performance. The article is published open access, with the version shared early carrying a permanent DOI and remaining subject to further edits before the final Version of Record.

Subject of Research: Serum calcium to magnesium ratio as a prognostic biomarker for three-month recovery in Bell's palsy

Article Title: Serum calcium to magnesium ratio as a prognostic biomarker of three-month recovery in Bell’s palsy: a prospective cohort study

Article References: Ağırbaş, S., & Çetin, Y. S. (2026). Serum calcium to magnesium ratio as a prognostic biomarker of three-month recovery in Bell’s palsy: a prospective cohort study. BMC Neurology. https://doi.org/10.1186/s12883-026-05531-y

Image Credits: AI Generated

DOI: 10.1186/s12883-026-05531-y

Keywords: Bell's palsy, facial paralysis, calcium to magnesium ratio, prognostic biomarker, House-Brackmann scale, prospective cohort study, BMC Neurology, electrolytes, magnesium, corticosteroid therapy, ROC analysis, Serum