Eyeworld

EW CORNEA 134 October 2016 by Vanessa Caceres EyeWorld Contributing Writer outside the comfort zone of corneal specialists," they said. There is just a small group of pa- tients who would benefit most from these types of treatment. The target patient must have intractable ocular dry eye-like symptoms, postherpetic and post-traumatic neuralgia, and chronic ocular/periorbital pain with or without photoallodynia. There must be minimal findings on an ocular exam and a lack of response to current treatments, including oral analgesics. Patients must also receive treatment for mental problems such as depression and anxiety before consideration for surgery. Doctors also will want to limit opioid dose escalation to curb the adverse effects of intrathecal opioid use. 1 Weighing in The collaborative procedure done by Drs. Sayegh, Hayek, and colleagues is something that Anat Galor, MD, associate professor of clinical ophthalmology, Bascom Palmer Eye Institute, University of Miami, Miami, and staff physician, Miami Veterans Affairs Medical Center, has not yet performed, but she thinks it will show others what can be done in patients with the most severe level of corneal pain. "Right now, there are many patients whose ocu- lar pain is not adequately managed. This is when approaches that have been used to treat non-ocular pain can be considered, starting with oral medications, non-invasive adjuvants Case study highlights collaboration among specialties T he causes of and treatment for corneal neuropathic pain are a hot topic right now in ophthalmology. One group of Ohio phy- sicians has taken a multispecialty approach in treating a handful of severe cases. Led by Rony Sayegh, MD, assistant professor of ophthalmolo- gy, Case Western Reserve University School of Medicine, Cleveland, and Salim Hayek, MD, program direc- tor, anesthesiology pain medicine, UH Case Medical Center, and profes- sor of anesthesiology, Case Western Reserve University School of Medi- cine, their case study was published earlier this year in pain medicine and ophthalmology journals. 1,2 The approach they use involved: (1) an electrode for electrical stim- ulation of the trigeminal ganglion, and (2) a high cervical intrathecal pain pump for fentanyl and bupiva- caine delivery, both with the goal of reducing corneal neuropathic pain. Published case details The patient described in both jour- nal reports was a 30-year-old woman referred for dry eye and photoal- lodynia after having LASIK 9 years before. The patient had tried topical lubrication, steroids, cyclosporine eye drops, scleral lenses, and various other medications, including non- steroidal anti-inflammatory drops and tramadol non-opioid analgesics. She had also seen various ophthal- mologists and pain specialists. When the patient presented to the clinic, she was using 20% autologous serum tears six to eight times a day, which provided some pain relief. She also used bupropion and clonazepam for anorexia nervosa. The slit lamp examination was unremarkable, but an exam with confocal microscopy showed a significant decrease in cornea nerve density. Physicians from ophthalmology, neurological surgery, and anes- thesiology at University Hospitals collaborated to implant a permanent electrode array into the trigeminal ganglion via the left foramen ovale after a successful trial. The 3387 Medtronic Deep Brain Stimulator electrode (Medtronic, Minneapolis) was inserted and directed toward the trigeminal ganglion's V1 branch. Physicians performed intraop- erative testing to confirm that the paresthesia was felt in the V1 distri- bution but that it did not produce corneal anesthesia. The patient had immediate pain relief in both eyes, even though the stimulation was only unilateral. After surgery, the patient was fitted with a rechargeable generator implanted in the left abdominal wall. The electrode provided pain re- lief up until 8 months; at that point, her left V1 paresthesia disappeared, and her ocular symptoms returned in both eyes. An X-ray showed that the electrode lead had migrated; although the lead was replaced with a longer electrode, the patient asked for the system to be explanted because it was no longer possible to control her symptoms. Two months later, the patient had a staged procedure with a trial of a high cervical intrathecal infu- sion of bupivacaine with low-dose fentanyl. "An intrathecal catheter was inserted at L2-L3 and advanced to the C1-C2 level, confirmed by fluoroscopy, and connected to a length of tunneled extension tub- ing," the authors wrote. 2 The patient experienced pain relief during the trial; after that a 20-mL Medtronic SynchroMed II intrathe- cal pain pump was implanted; the initial infusion was fentanyl 4.99 micrograms daily and bupivacaine 2.99 mg a day. Although physicians had to manage catheter migration and cerebrospinal fluid collection around the pump 2 weeks later, the patient's treatment course has since been uneventful. She has had continuous pain relief with the bu- pivacaine/fentanyl infusion for more than a year. In addition to the literature reports, Drs. Sayegh and Hayek said they have tried each of the two procedures in a handful of patients. A 55-year-old male has had the electrode for more than 6 months, which later had to be replaced with the pump, and that has controlled his symptoms for more than a year and has been working well. A 21-year-old female had the pump, but it was removed due to a cere- brospinal fluid leak. A 58-year-old female had a failed trial with the electrode, so no permanent implan- tation was performed. Idea behind the approaches These unique approaches to corneal neuropathic pain were borrowed from pain medicine colleagues. "Neuromodulation, both with electrical stimulation and chemicals with targeted drug delivery, has been successfully used for chronic pain, such as low back pain," Drs. Sayegh and Hayek said. Now that there are finer electrodes that can be placed percutaneously as well as better drug delivery systems, and a better understanding of cerebrospinal fluid dynamics and the effects of various drugs on the nervous system, these pain methods have become more popular, they explained. Specifically, it's been used for facial pain in some patients, with positive results. "As parallels between chronic dry eye and neuropathic pain were being drawn, applying the corresponding treatments seemed like the next logical step," they said. The physicians have received referrals from around the U.S. to treat severe cases of corneal neuro- pathic pain. They admit that this approach is not yet practical for all physicians to perform. "For the time being, these techniques can only be performed by seasoned pain specialists and neurosurgeons. The areas involved in the treatment fall New approaches to controlling corneal neuropathic pain Intraoperative lateral fluoroscopic view of the intrathecal pump

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