Subcutaneous Botulinum Toxin Injections for the Treatment of Chronically Painful Post-Craniotomy Scars: A Case Report of Two Patients Treated Successfully for More Than Eight Years

Recently, the use of botulinum toxin type A(BoNT-A) has been reported to help with neuropathicpain reduction in numerous conditions,including painful chronic scar formation. Themechanism by which BoNT-A inhibits pain isunclear, but it appears to involve a reduction ofperipheral pain sensitization, which indirectlyreduces central pain sensitization. Two patientswho underwent surgery for brain tumor resectiondeveloped chronic painful neuropathic postcraniotomyscars. Their scar pain was not relievedwith oral pain medications or trigger point injectionswith steroids but was helped significantlywith BoNT-A injections. In the first patient, overthe past 8 years, we have gradually increasedher scar BoNT-A dose to 150 units diluted 2:1with normal saline (NS) and injected the dose at20 sites around her scar. She now reports herscar pain is 80%-90% resolved with the effectlasting 10 to 11 weeks. She denies side effectsat this dose. In the second patient, over 9 years,we gradually increased the BoNT-A dose to 175units diluted 2:1 with NS at 30 sites around herscar and in the left occipital area. She now notesher scar pain is 70%-75% improved from baselinewith the effect lasting 8 to 10 weeks followed by agradual reduction in benefit. She reports no sideeffects with this dose. The results of this 2-patientcase study suggests BoNT-A (specifically onabotulinumtoxinA)may be helpful for patients withchronic postcraniotomy scar pain. Further studieson the dose, injection sites and timing follow-upinjections are needed to determine treatment effectivenessfor this patient population.Key words: Scar pain, Botulinum toxin, chronicpain, subcutaneous, injections, post-craniotomy