ABBREVIATIONS:
anesthesia dolorosa
peripheral nerve stimulation.
Anesthesia dolorosa (AD) is a rare type of deafferentation pain, with incidence 0.3% to 2%, and represents one feared complication of trigeminal rhizotomy. 1 It can be caused by surgical injury to the trigeminal nerve after removal of tumors or by penetrating cranial injury. 1 Surgical management of medically refractory trigeminal neuralgia (TN) typically involves lesioning, aiming for partial deafferentation, yet 5%-15% of patients develop constant dysesthesias. 2 , 3 The pathophysiology of AD remains incompletely understood, and hypotheses include changes in sodium and calcium channels, deficient inhibitory pathways, and increased sympathetic stimulation. 4 Accordingly, AD can present with a spectrum of symptoms ranging from total loss to mostly preserved sensation. Similar to neuropathic pain, some have theorized that changes in membrane excitability leads to expression of new genes that may influence responsiveness to cutaneous stimulation. 3 Although response to pharmacotherapy has been poor, relief with gabapentin has been reported, and the mechanism of action may relate to its ability to enhance neuronal inhibition and to suppress central deafferentation hypersensitivity. 5 Neuromodulation has the same aim and can be accomplished by central stimulation by deep brain stimulation 6 or cortical 7 , 8 and peripheral stimulation. The level of invasiveness and risk profile differ between these approaches, namely bleeding, infection, and need for revision. Peripheral stimulation has less risk with the primary challenge being securing an electrode in the mobile soft tissue present around the jaw and face.
CLINICAL PRESENTATION
We present a case of a 71-year-old female patient with bilateral TN secondary to multiple sclerosis for which she underwent multiple rhizotomies with temporarily improved pain but with development of AD. After her most recent balloon rhizotomy, she reported that the electrical type pain on the left face improved but resulted in increased burning sensation similar in intensity and timing to her previous TN symptoms. Her episodes consisted of burning pain in her left upper and lower jaw associated with 75% numbness (tactile and pinprick) compared with the right, lasting 1 week, and impairing her ability to talk, eat solids, and brush her teeth. She had a very low tolerance for carbamazepine and gabapentin and therefore took baclofen and pregabalin. Owing to some preserved sensation, an off-label, left percutaneous trigeminal ganglion stimulator externalized trial was offered.
First, local anesthesia was injected into the left cheek 2 cm lateral to the corner of the mouth. A 16 gauge needle was used to pierce the skin, and an 11 gauge Jamshidi needle was advanced under fluoroscopy to the foramen ovale. Then, the inner cannula was removed, and dura was perforated with a Shepherd's crook. The electrode was then advanced through the Jamshidi needle under fluoroscopy approximately 2-3 contacts into the skull base. We then removed the needle and secured the electrode on the left cheek with suture at the entrance site, cheek, and auricular area. We then connected the externalized generator and placed it in its externalized pouch on the left chest wall after confirming good impedances. Stimulation parameters detailed in Table were tested in the operating room and did not require adjustment.
TABLE.
Table Demonstrating Pulse Generator Programs With Stimulation Parameters
| Program | Contacts | Frequency (Hz) | Pulse width (µs) | Max amplitude (mA) |
| 1 | 2, 4 | 30 | 120 | 2.50 |
| 2 | 1, 2 | 90 | 120 | 0.60 |
| 3 | 2, 3 | 60 | 90 | 1.60 |
| 4 | 1, 2, 3 | 40 | 1000 | 0.50 |
The trial lasted approximately 2 weeks without turning the stimulator off, and patient's pain score improved from 9/10 to a 0-1/10 during episodes immediately after surgery. The patient's relief was sustained at initial settings until a permanent stimulator was placed 2 months later. Placement of permanent St. Jude Octrode neurostimulator lead was conducted in the same way as the trial with the lead advanced 2 mm deep to the clival line under direct fluoroscopy (Figure A and B). The electrode was anchored at the left cheek and postauricular area with butterfly anchors and 3-0 Ethibond suture. The wire was tunneled subcutaneously to left chest wall by a skip incision in the postauricular area, where it was connected to the generator.

At follow-up, patient described an ability to perform baseline activities including eating and brushing teeth without any burning pain (0-1/10). Her relief in upper and lower teeth remained stable over 3 years with only minimal stimulator setting adjustments and a stable regimen of baclofen and pregabalin. Informed consent was obtained from the patient for publication of this single case report, and Institutional Review Board approval was not required under our institutional policy.
DISCUSSION
Emerging modalities in neuromodulation have been effective in treating chronic pain, but application to treating AD has not been well explored. The idea of neuromodulating the sensory ganglion to produce potent effects has been championed for chronic back pain through dorsal root ganglion stimulation. 9 Although the anatomy and physiology of the trigeminal ganglion differs from a spinal dorsal root ganglion, ganglion stimulation may be a more effective option than peripheral or field stimulation. Several nonrandomized studies have reported trigeminal nerve field stimulation in the trigeminal dermatomes for intractable chronic and neuropathic pain of different origins. 10 In a study of 10 patients treated with supraorbital peripheral nerve stimulation (PNS) for intractable supraorbital neuralgia, Amin et al 11 reported a decrease in headache scores and halving opioid consumption for a duration of 30 months. Johnson and Burchiel 12 reported in a study of 10 patients that PNS provided at least 50% pain relief in 70% of patients with trigeminal neuropathic pain after facial trauma or herpes zoster infection. Ni et al 13 conducted a systematic review demonstrating that trigeminal PNS, including the trigeminal ganglion, was overall efficacious in treating trigeminal neuropathic pain. Percutaneous trigeminal ganglion stimulation (TGS) has been reported as a potential treatment option for refractory pain associated with persistent idiopathic facial pain where McMahon et al demonstrated that TGS is efficacious and can significantly decrease morphine equivalent use. 14 Our technique is similar to that described by McMahon et al; however, our follow-up was over 3 years, whereas, the longest follow-up described by McMahon was approximately 2 years.
TGS was first described in 1999 as the first percutaneous technique of electrode placement as a means to treat neuropathic pain. 15 There is no consensus on the definition of a positive test trial, but a reduction in pain of 50% or more on the visual analog scale, reduction in oral pain medication, or subjective increase in the quality of life are considered to be outcomes that favor implantation of a permanent system. 10 Although it is not a strict contraindication, some degree of sensory preservation may predict better response to TGS. It is reasonable to offer a stimulation trial, given patients may often have a difficult time discerning degree of numbness. One case report for a patient with refractory chronic TN who received supraorbital, supratrochlear, and infraorbital nerve stimulation reported 50% decrease in pain post stimulation that lasted 6 months, whereas another case of refractory chronic TN reported well controlled pain 3 weeks after implanting supra- and infraorbital electrodes. 16 Our patient reported almost full resolution of pain after the test trial and during permanent stimulation over 3 years, allowing her to return back to baseline function.
Overall, rhizotomy for AD holds significant risk of sensory disturbances, 17 and importantly, the numbness experienced by patients suffering from AD secondary to multiple sclerosis is not always described as a complete numbness. Our approach with stimulation relies on the hypothesis that restoring some tonic signaling to the trigeminal nucleus may help restore the normal excitatory/inhibitory balance and signal the thalamus to alleviate pain. This is supported by long standing work in the spinal cord injury field, where improved motor control with dorsal column spinal cord stimulation is thought to be a result of enhancing dormant motor circuits with residual connections. 18 , 19 The primary challenge of TGS remains identifying the appropriate hardware to allow robust anchoring to the face due to the financial barriers to device development for a rare condition. It should be noted that this problem has been addressed for sphenopalatine ganglion stimulation where similar challenges have been overcome. 20
CONCLUSION
We presented a case of a patient with a history of treatment refractory AD who experienced significant and durable pain reduction during 3 years after trigeminal ganglion stimulator placement. Research is needed to refine the clinical indications for TGS and improve hardware fixation.
Acknowledgments
Author contributions: SK and CMP contributed equally as co-first authors, including drafting the initial manuscript, creating figures/tables, case interpretation, and critical review/revision of manuscript. AWG provided neurosurgical expertise and reviewed the manuscript. DRN provided orofacial pain expertise. DRN and DPD contributed to case selection, critical manuscript revision, and supervision of project. All authors approved the final version and agreed to be accountable for all aspects of the work. We acknowledge the neurosurgery pain patients that willingly undergo trials to further advance treatment modalities.
Sarah Kawtharani and Crina M. Peterson contributed equally to this work.
Funding
This study did not receive any funding or financial support.
Disclosures
David P. Darrow receives financial support from Abbott. The other authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
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