Treating postherpetic itch with dorsal root ganglion stimulation: a case report

Background & Aims
Chronic itch is common; it affects nearly 17% of the world’s population. A subset of patients suffers from severe neuropathic itch which has limited
treatment options and significantly impacts quality of life. The physiology of itch shows surprisingly overlap with the physiology of pain. Moreover, the
fundamental difference between pain and itch is still debated.
Neurostimulation, especially invasive neurostimulation, is a proven effective treatment option for chronic neuropathic pain. There are therefore strong
indications that neurostimulation could also be used to target chronic neuropathic itch [1]. Yet, invasive neurostimulation has not been used in these
patients.
Here we present an 80 years old patient with maddening postherpetic itch in the left sixth thoracic dermatome after being treated successfully for
postherpetic pain. Pain and itch are common symptoms of postherpetic neuralgia, one of the four most prevalent neuropathic pain syndromes. It occurs
after a herpes zoster infection causing a neuritis in peripheral nerves within one or more dermatomes [2,3].
Methods
Baseline measurements consisted of quantitative sensory testing (QST) according to the DFNS protocol, numeric rating scale (NRS) scores on itch intensity,
and questionnaires.
There was a two-week trial phase with electrode-leads (Abbott, USA) placed on the left dorsal root ganglions (DRG) of Th6 and Th7. The leads were
connected to an external pulse generator, and a different stimulation setting was programmed every three days. Effects of the stimulation paradigms were
monitored with QST and a patient diary.
The trial was considered successful and the patient received an implanted pulse generator (Proclaim DRG®, Abbott, USA). Follow up measurements were
conducted at 3, 6 and 12 months.
Results
Baseline
QST showed hypesthesia for cold and warm temperature detection on the affected and contralateral side and allodynia in the affected dermatome
suggesting predominant C and A-delta fiber dysfunction. A-beta fiber function showed normal QST values suggesting neurostimulation could be effective.
NRS score for continuous itch was 8/10.
Trial
Two electrode-lead at the DRGs could cover the entire itching bodypart. Stimulation with 4, 20 and 80 Hz caused different sensations, but all reduced the
itch sensation from NRS 8/10 to NRS 3/10. The patient received an implanted pulse generator with two programs and could vary between the programs.
Follow-Up
During the day, the patient perceived fluctuations in itch sensation. When itch intensity increased, an increase in stimulation amplitude or switch between
programs could suppress the itch again. The patient used both programs, 80Hz mainly at night, 4Hz during the day.
At follow-up visits, the NRS for itch was on average 3/10, and QST showed decreased allodynia in the affected dermatome and normalization of all QST
parameters on the contralateral side. The QST normalization on the contralateral side may be explained by reduced distraction by itch sensations
Conclusions
Our case shows that dorsal root ganglion stimulation can effectively modulate otherwise intractable postherpetic chronic itch.
References
1. M Badwy ea, Experimental Dermatology. 2022;31:280–289.
2. AJM van Wijck ea, Pain Practice, 2017;17:738–746.
3. O van Hecke ea, Pain 2014;155:654–662.