A newly published case report follows the unique medical history of a woman born with an insensitivity to pain. Following labor and childbirth by Cesarean section, the woman began to suffer from continuous buzzing sensations and electric shocks in her legs along with a squeezed feeling in her pelvis. According to the team of University of Cambridge scientists, this unusual case history sheds light on neuropathic pain while potentially lighting the way to new drug therapies for pain sufferers.

The woman, 37 years old, had a rare case of Channelopathy-associated Insensitivity to Pain (CIP) syndrome and was first diagnosed (along with an older sister) at age 7. Her parents and other family members were not similarly affected. Eighteen years later, her diagnosis was confirmed when doctors tested her for a genetic mutation of SCN9A, the gene that codes for a protein considered necessary to the sensation of pain.

Such mutations “are associated with profoundly altered pain thresholds,” the authors wrote, and in some very rare cases result in CIP syndrome, “a complete absence of pain sensation, while all other sensory modalities apart from the sense of smell remain intact.”

During childhood, the woman had suffered a variety of injuries to the cornea and tongue, burns, and relatively minor fractures. Other than these — painless to her — injuries, her medical history contained no drama. Until, that is, she delivered her child.

After the birth, the woman developed symptoms that she “readily describes as pain, and which has neuropathic features,” the researchers noted. Importantly, during the C-section procedure, she sustained pelvic fractures and an epidural hematoma that impinged on a nerve in her back. Most likely due to her unusual physical condition, these injuries were not recognized for a full two months. By that point she was suffering weakness in both her legs and she also had no ankle reflexes, the researchers noted.

Unfortunately for the woman, her physical condition went from bad to worse. Two months after this exam (four months after giving birth), the woman reported a continuous buzzing and electric shocks in both her legs, and a vice-like squeezing in her pelvis when she walked.
These symptoms are consistent with neuropathic pain, a chronic pain, in which the nerve fibers themselves might be damaged, dysfunctional, or injured. Despite the diagnosis of neuropathic pain, her symptoms did not respond to the usual treatment: a drug, gabapentin. Sadly, the woman's symptoms have lasted for six years and continue to plague her today.

While this may be terrible for the once pain-free woman, the scientists believe her case history demonstrates that, contrary to popular belief, pain (or at least one form of it) can be initiated and maintained without Nav1.7 channels. This unexpected finding raises the possibility that pain-killers targeting this channel may only relieve certain aspects of neuropathic feeling. With more complete knowledge of pain provided by this study, the authors suggest, new, more effective treatments may be developed.

Source: Wheeler DW, Lee MCH, Harrison EK, Menon DK, Woods CG. Case Report: Neuropathic pain in a patient with congenital insensitivity to pain. F1000Research. 2015.