This ectopic firing could result from increased expression of some sodium channel subunits, such as NaV1.3 and NaV1.6, which are upregulated in biopsies from trigeminal neuralgia patients and in patients with complex regional pain syndrome and post‐herpetic neuralgia (Siqueira et al., 2009; Sittl et al., 2012; Tanaka et al., 2016; Zhao et al., 2008). The gene discussed is SCN8A; the disease is complex regional pain syndrome.