Trigeminal Nerve Peripheral Nerve Stimulation

Introduction

Trigeminal neuropathic pain (TNP) is a commonly encountered condition that involves patients of all demographic backgrounds and presents a major burden to patients, their families, treating physicians, and society as a whole. Arising from dysfunction of trigeminal sensory system, TNP differs from trigeminal neuralgia (TN) in both causation and clinical presentation. Whereas TN is frequently caused by vascular compression of the trigeminal nerve root by nearby arterial or venous structures, TNP is a result of surgical, traumatic, infectious, or any other injury or damage of the trigeminal nerve and its branches. Most prevailing classifications differentiate nonneuralgic neuropathic pain in the trigeminal nerve distribution based on its cause and pattern of symptoms; among its types, the term trigeminal deafferentation pain (TDP) is used for those instances where pain develops after interventions/surgeries on the trigeminal nerve itself, usually for treatment of TN, whereas the actual term TNP is reserved for pain that follows facial trauma or surgery on facial structures, including the oral contents, soft tissues of the face, sinuses, etc., and the neuropathic pain following herpetic (herpes zoster, shingles) eruption is assigned a separate term of postherpetic neuralgia (PHN).

With the trigeminal nerve being the largest cranial nerve, providing over two thirds of craniofacial sensory innervation, its associated pain syndromes result in significant morbidity, anxiety, sleep disturbance, and depression. Although the epidemiology of TN has been extensively sought in previous reviews, yielding a mean prevalence of 0.03% to 0.3% with a 60: 40 bias towards women and an average onset of 53 to 57 years of age, the same information about TNP is generally lacking. Independent of the pain type, the primary treatment strategy begins with pharmacologic therapy, including antiepileptic and antidepressant drugs, followed by more invasive interventions if the medical treatment fails. One such intervention, covered in detail below, is peripheral nerve stimulation (PNS), which was developed in the 1960s and popularized during the first decade of this millennium. Although it is of no value in the management of TN, PNS has been remarkably successful in the management of patients with TNP.

We aim to provide insight on the use of trigeminal PNS as a part of a treatment spectrum that is considered once pharmacologic therapy has been attempted. We outline the most common presentation complaints, differential diagnosis, indications, and contraindications for PNS, focusing on anatomy in relation to the trigeminal structures, and construct a visual scaffold to guide the operative approach. Common complications previously described in the literature are presented here in an effort to minimize their occurrence in clinical practice.

Clinical Presentation and Diagnosis

Trigeminal nerve pain, whether neuralgic or neuropathic, commonly presents with patients experiencing a significant detriment to their quality of life or activities of daily living. A detailed history of present illness commonly demonstrates rather constant pain and discomfort that are described as burning, tightness, pressure, gnawing, and shooting sensations occurring either continuously or in response to stress, sometimes fluctuating with the time of day, which is quite different from TN pain, where the pain tends to occur following innocuous stimuli such as speaking, tooth brushing, wind, touch, and chewing. Figures 9.1 and 9.2 demonstrate the various differential diagnoses within trigeminal nerve pain and autonomic cephalalgias.

A physical and neurologic examination is required to rule out other neurological issues and specifically to test for preservation or impairment of sensation in the region of pain, as this will be important in determining a patient’s appropriateness for PNS candidacy, because complete absence of sensation may make a patient ineligible for conventional stimulation.