Results showed that the monthly SNAP reductions were most severe within the first 2 months of evolution, began to slow after 7 months, and stabilized after 10 months. Reductions in SNAP were highly correlated with progression of disability, as measured by modified Rankin score (P < .001).
Kaplan-Meier analysis revealed that the median time from onset to matching the electrophysiological criteria for SNN diagnosis was 8.5 months (95% CI, 3.2 – 13.8 months). SNN diagnostic criteria was more quickly achieved in older patients (odds ratio [OR] = 1.02; 95% CI, 1.01 – 1.04, P < .01), and those with paraneoplastic SNN (OR = 2.06; 95% CI, 1.05 – 4.00, P < .05).
After 8.5 months, 42% of the sensory nerves were still excitable, and 18% and 11% had a SNAP value above 30% and 50% LLN, respectively.
“Knowledge of the temporal profile of neuronal degeneration and of the time lapse until matching the diagnostic criteria is crucial for future therapeutic developments for SNN. Any future treatment must be applied before too many neurons are lost or before the ongoing process leading to neuronal degeneration cannot be reverted,” the authors point out.
“Being alert to the clinical distinction between neuropathies versus neuron/ganglionopathy will help limit exposing patients to potentially dangerous medications only in cases where the drugs could be helpful,” Dr Varadhachary added, noting that the study is limited by lack of individualized time-course data, physical exam findings, and pathologic information for the sensory nerves or ganglion.
Further research is needed to determine whether SNAP amplitudes can be used as markers of DRG degeneration, and whether timing treatment administration can improve outcomes in patients with an SNN.
This study was supported by a grant from the French Ministry of Health.
Antoine JC, Robert-Varvat F, Maisonobe T, et al. Identifying a therapeutic window in acute and subacute inflammatory sensory neuronopathies. J Neurol Sci. 2016 Feb 15;361:187-91. doi: 10.1016/j.jns.2015.12.044. Epub 2015 Dec 29.