title: Case Report: Neuropathic pain in a patient with congenital insensitivity to pain.
abstract: We report a unique case of a woman with Channelopathy-associated Insensitivity to Pain (CIP) Syndrome, who developed features of neuropathic pain after sustaining pelvic fractures and an epidural hematoma that impinged on the right fifth lumbar (L5) nerve root. Her pelvic injuries were sustained during painless labor, which culminated in a Cesarean section. She had been diagnosed with CIP as child, which was later confirmed when she was found to have null mutations of the SCN9A gene that encodes the voltage-gated sodium channel Nav1.7. She now complains of troubling continuous buzzing in both legs and a vice-like squeezing in the pelvis on walking. Quantitative sensory testing showed that sensory thresholds to mechanical stimulation of the dorsum of both feet had increased more than 10-fold on both sides compared with tests performed before her pregnancy. These findings fulfill the diagnostic criteria for neuropathic pain. Notably, she mostly only experiences the negative symptoms (such as numbness and tingling, but also electric shocks), and she has not reported sharp or burning sensations, although the value of verbal descriptors is somewhat limited in a person who has never felt pain before. However, her case strongly suggests that at least some of the symptoms of neuropathic pain can persist despite the absence of the Nav1.7 channel. Pain is a subjective experience and this case sheds light on the transmission of neuropathic pain in humans that cannot be learned from knockout mice.
authors.affiliation: Division of Anaesthesia, University of Cambridge, Cambridge, CB2 0QQ, UK.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Wheeler
authors.affiliation: Division of Anaesthesia, University of Cambridge, Cambridge, CB2 0QQ, UK.
authors.forename: Michael C H
authors.initials: MC
authors.lastname: Lee
authors.affiliation: School of Clinical Medicine, University of Cambridge, Cambridge, CB2 0SP, UK.
authors.forename: E Katherine
authors.initials: EK
authors.lastname: Harrison
authors.affiliation: Division of Anaesthesia, University of Cambridge, Cambridge, CB2 0QQ, UK.
authors.forename: David K
authors.initials: DK
authors.lastname: Menon
authors.affiliation: Department of Medical Genetics, University of Cambridge, Cambridge, CB2 0QQ, UK.
authors.forename: C Geoffrey
authors.initials: CG
authors.lastname: Woods
keywords: Channelopathy; Congenital Insensitivity to Pain; Neuropathic Pain; Pain