73 Trigeminal Neuropathic Pain

Case 73 Trigeminal Neuropathic Pain

Melanie Hood and Christopher J. Winfree

Clinical Presentation

A 45-year-old woman who, 2 years previously, was in a motor vehicle accident and sustained facial injuries, including a right-sided facial laceration and an orbital fracture.
Since the time of injury, she reports right-sided facial pain in a V1 and V2 distribution.
The pain is constant, burning in nature, and grades 7–8/10 in severity.
Given the persistence of pain, she was suspected of having trigeminal neuralgia. A microvascular decompression was performed at an outside institution, but this did not help.
On physical examination, she has mildly decreased sensation in her right V1 and V2 distributions.

Questions

What is this patient’s diagnosis?
What are her noninvasive treatment options?
What are her invasive treatment options?
The patient undergoes a variety of pharmacologic treatments, including nonsteroidal antiinflammatories, anticonvulsants, and antidepressants, none of which yielded acceptable pain relief. Multiple anesthetic and steroid injections along the supraorbital and infraorbital nerves likewise failed to help. Psychological evaluation reveals no psychological amplifiers of her pain syndrome, such as depression, unresolved conflicts, sleep disorders, etc. You are considering offering the patient a surgical therapy.
Describe the relative merits and drawbacks of each type of therapy.

Answers

What is this patient’s diagnosis?

This patient has trigeminal neuropathic pain (TNP), a neuropathic pain syndrome that occurs following injury to one or more branches of the trigeminal nerve. This injury generally results in partial sensory loss within the trigeminal system.1

Although the pathophysiology of TNP is currently not well understood, deafferentation of central trigeminal pathways likely results in pathologically amplified sensory barrages that are perceived by the patient as painful.²
What are her noninvasive treatment options?
- The anticonvulsant³ and antidepressant⁴ medications are the initial treatments of choice for neuropathic pain in general, although little data exist for their specific use in TNP.
- Opiate medication, transcutaneous electrical nerve stimulation, acupuncture, and other complementary and alternative therapies may certainly be used as well, but prospective clinical data regarding their use in TNP are lacking.
What are her invasive treatment options?
- If noninvasive measures are unhelpful, then local injections may be tried, but their efficacy in facial pain syndromes is unknown.
- Peripheral neurectomy, in which the trigeminal branch within the painful distribution is destroyed, actually increases the trigeminal system injury, potentially exacerbating the deafferentation phenomenon and worsening the patient’s pain.
- Neurostimulation, in which electrodes are used to administer electrical impulses to the trigeminal pain pathways, may be utilized.⁵
Describe the relative merits and drawbacks of each type of therapy.
- Although other forms of stimulation such as motor cortex stimulation could address this problem, trigeminal branch stimulation, a form of peripheral nerve stimulation, offers a less invasive and safer alternative.⁶
- In this technique, percutaneous electrodes are placed in the subcutaneous space under local anesthetic; these electrodes are placed overlying either the supraorbital (V1) or infraorbital (V2) nerves depending on the particular pain distribution; stimulation paresthesias, and subsequent pain relief, occur in the respective trigeminal distribution(s) (Fig. 73.1).
- After a 1-week percutaneous trial, if sufficient pain relief occurs, the patient may undergo placement of a permanent electrode system (Fig. 73.2).