Transcranial Direct Current Stimulation (tDCS) Relieved Itching in a Patient With Chronic Neuropathic Pain

Itching is often called the second modality of nociception besides pain, and affects many chronic pain patients. Objectives: This case report presents a first note on beneficial effects of transcranial direct current stimulation (tDCS) on itching associated with chronic neuropathic pain in a patient diagnosed with syringomyelia. Methods: tDCS is a novel noninvasive neuromodulatory method with promising therapeutic potential in pain and symptom management. The primary mechanism of tDCS is subthreshold modulation of the neuronal resting membrane potential that induces a polarity-dependent modification of N-Methyl-D-aspartate receptor function that plays a role in neuroplasticity. The patient, a 46-year-old white male diagnosed with syringomyelia 2 decades ago, continuously reported weakness in the arms and dyesthesias including pain and itch that fluctuated in severity. Pharmacological treatment with baclofen, duloxetine, and bupropion was partially helpful; however, did not prevent flares of pain and other dysesthesias, including itch. The patient underwent 3 tDCS treatment courses consisting of 20 minutes of tDCS on 5 consecutive days at each course over 13 months. Results: Although there was no change in pain intensity or quality during or after tDCS, the treatment resulted in a reduction in itch to a mild, tolerable intensity that persisted for 3 to 4 months after each course, before returning to the pretreatment level. The patient has agreed to a plan of care that will incorporate neurostimulation every 4 to 6 months, as long as its effectiveness continues. Discussion: This case provides a rationale for future studies of neuromodulatory treatments for itch, and indicates a potential clinical use of neuromodulation in patients with unrelieved itching.