Anatomy of Trigeminal Neuromodulation Targets: From Periphery to the Brain.

The trigeminal nerve complex is a very important and somewhat unique component of the nervous system. It is responsible for the sensory signals that arise from the most part of the face, mouth, nose, meninges, and facial muscles, and also for the motor commands carried to the masticatory muscles. These signals travel through a very complex set of structures: dermal receptors, trigeminal branches, Gasserian ganglion, central nuclei, and thalamus, finally reaching the cerebral cortex. Other neural structures participate, directly or indirectly, in the transmission and modulation of the signals, especially the nociceptive ones; these include vagus nerve, sphenopalatine ganglion, occipital nerves, cervical spinal cord, periaqueductal gray matter, hypothalamus, and motor cortex. But not all stimuli transmitted through the trigeminal system are perceivable. There is a constant selection and modulation of the signals, with either suppression or potentiation of the impulses. As a result, either normal sensory perceptions are elicited or erratic painful sensations are created. Electrical neuromodulation refers to adjustable manipulation of the central or peripheral pain pathways using electrical current for the purpose of reversible modification of the function of the nociceptive system through the use of implantable devices. Here, we discuss not only the distal components, the nerve itself, but also the sensory receptors and the main central connections of the brain, paying attention to the possible neuromodulation targets.

Motor Cortex Stimulation for Facial Pain.

Motor cortex stimulation (MCS) has been used in the treatment of intractable neuropathic facial pain for nearly 30 years. While efficacy rates have been noted as high as 88% in some studies, considerable variability in treatment response remains. Additionally, MCS is often cited as providing diminishing relief over time, and there are few long-term studies on efficacy. Complications are generally mild and include infection, hardware complication, seizure, and transient neurological deficit. Despite relatively minimal use, MCS remains a viable treatment option for the appropriately selected facial pain patients that have proved refractory to conservative management.

High-Frequency Peripheral Nerve Stimulation for Craniofacial Pain.

Since the first successful use of high-frequency electrical stimulation of trigeminal branches for treatment of facial pain in 1962, neuromodulation techniques become well established but remain greatly underutilised. Most subsequent implantation techniques and commercial devices for peripheral nerve stimulation, available until the last decade, utilised frequencies in the range 1-100 Hz. With the commercial introduction of 10-kHz spinal cord stimulation, there has been renewed interest in peripheral applications of kHz frequency neuromodulation. High-frequency biphasic stimulation causes rapid onset, reversible conduction block in mammalian nerves which might be useful in human peripheral neuromodulation applications, but the conduction block induced at kilohertz frequencies may not be the only mechanism contributing to analgesia. We discuss likely mechanisms of action of high-frequency peripheral nerve stimulation and present several clinical examples of successful use of this modality in various facial pain conditions. A change to sub-threshold higher frequencies in the 10 kHz range adds a number of distinct advantages. The lack of paresthesias is welcomed by patients. The ability to place the stimulating electrode approximately 1 cm away from the targeted nerve has an anatomical and surgical advantage.

Peripheral Nerve Stimulation for Facial Pain Using Conventional Devices: Technique and Complication Avoidance.

The introduction of peripheral neuromodulation to treat headache and facial pain two decades ago opened up the field to non-neurosurgical practitioners, given the relatively low risk and technical ease of the procedure. These procedures, primarily occipital nerve stimulation (ONS) and trigeminal branch stimulation such as supra- and infraorbital nerve stimulation, are now established to be effective in a number of facial pain and headache syndromes, despite their lack of approval by regulatory agencies such as the US Food and Drug Administration (FDA). For that reason and others, dedicated hardware for these procedures has not yet been developed, thus relying on hardware designed for placement in the epidural space for spinal cord stimulation (SCS). This has led to a series of technical issues and device-related complications not traditionally seen with SCS. I will review the surgical technique of ONS and peripheral nerve stimulation of the head and face utilizing this equipment, and discuss methods learned by experienced practitioners over the years to minimize device-related complications.

Peripheral Nerve Stimulation for Facial Pain Using Conventional Devices: Indications and Results.

Trigeminal branch stimulation is a type of peripheral nerve stimulation (PNS) used to treat a variety of craniofacial pain disorders. Common indications include trigeminal neuralgia, trigeminal neuropathic pain, trigeminal deafferentation pain, trigeminal postherpetic neuralgia, supraorbital neuralgia, and migraine headaches. Supraorbital and infraorbital arrays are the most common electrode configurations, although preauricular, mandibular branch, and subcutaneous peripheral nerve field stimulation arrays have also been described. Trigeminal branch stimulation may be used as a stand-alone neuromodulation therapy or it may be combined with occipital nerve, sphenopalatine ganglion, or Gasserian ganglion stimulation to treat more complex pain patterns. Consistent with other forms of PNS, trigeminal branch stimulation is a minimally invasive, safe, and straightforward method of treating medically refractory neuropathic pain.

Peripheral Nerve Stimulation for Facial Pain Using Wireless Devices.

Since its original introduction several decades ago, peripheral nerve stimulation (PNS) of the craniofacial region has been traditionally performed using devices intended for spinal cord stimulation applications with inevitably high rate of technical challenges and procedural complications. The lower invasiveness of recently developed wireless neurostimulation systems makes them much better suited for craniofacial applications. Here, we discuss the preliminary clinical data from several published reports and the ongoing multicenter prospective study of wireless PNS in the craniofacial region. Advances in wireless transmission of electrical signals may make wireless neurostimulation even more attractive in the future. Since most of the evidence supporting PNS for facial pain comes from small subsets of the population, case series and case reports, there will need to be larger, randomized controlled trials with cost efficacy analyses in order to validate the role of wireless PNS as the standard of care.

Transcutaneous Electrical Nerve Stimulation for Facial Pain.

Transcutaneous electrical nerve stimulation (TENS) has been used for its analgesic effects for chronic pain, including facial pain. Here, we summarize how the electrical stimulation of branches of the trigeminal nerve via TENS has been utilized to reduce pain resulting from trigeminal neuralgia, temporomandibular joint disorder, migraine and other headache types, and ocular pain sensations. TENS has been used for both short-term (one session) and long-term (multiple sessions) pain control with little to no adverse effects reported by subjects. The results of the summarized studies suggest TENS is an effective non-invasive, non-pharmacologic means of pain control for patients with facial pain conditions.

Percutaneous Electrical Nerve Stimulation for Facial Pain.

Percutaneous electrical nerve stimulation (PENS) is a novel, minimally invasive and useful treatment modality. Its use in complex facial pain has been on the rise, and its utility will further increase with the advances in the technology and renewed interest in the field of peripheral neuromodulation. PENS therapy can be used both as diagnostic and therapeutic option. The precise mechanism of action is not known, although a combination of electrical neuromodulation and release of endogenous morphine-like substance in the central nervous system appears as plausible explanation. We analyse the various studies in the literature and discuss the Southampton data regarding facial pain treatment with PENS therapy. We believe that PENS therapy for facial pain and headache is currently underutilised. It is safe, economical and should certainly be part of the armamentarium in the treatment of complex facial pain and headache.

Gasserian Ganglion Stimulation for Facial Pain.

Non-neuralgic trigeminal neuropathic pain can be challenging in terms of treatment as pharmacological interventions often tend to be ineffective. Within the pain-transmitting pathway, the Gasserian ganglion (GG) is a rather unique anatomical and physiological structure where the sensory (including pain) information from the entire half of the face undergoes primary processing in a very compact and clearly defined entity. Moreover, GG is positioned in a completely immobile intradural location (the Meckel's cave) and is insulated from the brain by a layer of dura. As a confluence of all three trigeminal branches, GG allows one to achieve clinical effect on the entire half of the face with a relatively small surgical intervention while maintaining an ability to select exact facial regions based on known somatotopic organization of nerve fibers. Therefore, when it comes to electrical neuromodulation, the GG stimulation (GGS) may be a unique solution for treatment of medically refractory facial pain. GGS was introduced in 1970s and continues to be a recognized surgical modality with multiple published clinical series describing multi-year experience in hundreds of facial pain patients. GGS is particularly useful in treatment of patients with chronic trigeminal neuropathic pain and persistent idiopathic facial pain who tried and failed or were not considered good candidates for the conventional surgical interventions. With advances in lead technology, intraoperative visualization and stereotactic navigation, percutaneous GGS became a minimally invasive surgical intervention that is recommended for consideration in complex facial pain. Here, we review the clinical data and summarize the current state of GGS in facial pain treatment.

Burst or Conventional Peripheral Nerve Field Stimulation for Treatment of Neuropathic Facial Pain.

BACKGROUND: Trigeminal Neuropathic Pain (TNP) is a chronic facial pain syndrome caused by a lesion or disease affecting one or more branches of the trigeminal nerve. It may, for example, result from accidental injury to a branch of the trigeminal nerve by trauma or during surgery; it may also be idiopathic. TNP is typically constant, in contrast to most cases of the commoner trigeminal neuralgia. In some cases, pain may be refractory to pharmacological treatment. Peripheral nerve field stimulation is recognized as an effective minimally invasive surgical treatment option for this debilitating condition. To date, stimulation has used conventional tonic waveforms, which generate paraesthesia in the stimulated area. This is the first report of the use of paraesthesia-free burst pattern stimulation for TNP. METHODS: Seven patients were treated at the John Radcliffe Hospital for TNP from 2016 to 2018. Mean duration of preoperative symptoms was five years. All patients had exhausted pharmacological measures to limited effect. The initial three patients had tonic stimulation with the subsequent four having burst stimulation. Outcome was assessed using the numeric pain rating scale preoperatively and postoperatively at three and six months and one year. Side-effects and complications were also assessed as well as reduction in analgesic medication use. RESULTS: All patients achieved pain reduction of at least 50% at 6 months (range 50-100%, mean 81%, p = 0.0082). Those in the burst stimulation group were paraesthesia free. One patient developed a postoperative infection for which the system had to be removed and is awaiting reimplantation. There were no other complications in either group. CONCLUSION: Burst stimulation conferred similar pain control to tonic stimulation in our small cohort, and there were similar reductions in pain medication use. An additional benefit of burst stimulation is freedom from paraesthesia. Larger scale studies are needed to further evaluate burst stimulation and compare its efficacy with that of tonic stimulation.

Comparative study of shockwave therapy and low-level laser therapy effects in patients with myofascial pain syndrome of the trapezius.

The objective of the study was to compare the effects of shockwave therapy and laser therapy on pain, neck functionality, and quality of life in patients with myofascial pain syndrome of the trapezius. 61 patients (> 18 years) were randomly allocated to two treatment groups: (1) 31 patients received soft laser therapy once daily in a 3-week period for a total of 15 sessions, (2) 30 patients received shockwave therapy once in a week for 3 weeks, totalling 3 treatments. Resting pain and pain tolerance were assessed by a 100 mm visual analogue scale; functional status and quality of life were measured by specific questionnaires (Neck Disability Index, SF-36) before and after the 3-week therapy and at the 15th week follow-up visit. All measured parameters improved significantly in both groups at week 3 and week 15. Comparing the two groups, patients receiving shockwave therapy demonstrated significantly better changes in pain tolerance (mean between-group differences at visit 1-0 = 14.911, 95% CI = 2.641-27.182, mean between-group differences at visit 2-0 = 17.190, 95% CI = 4.326-30.055 in the left trapezius), neck functionality (mean between-group differences at visit 1- 0 = 0.660, 95% CI = - 1.933 to 3.253, mean between-group differences at visit 2-0 = 1.072, 95% CI = - 2.110 to 4.254), and in all domains using SF-36 QoL questionnaire. The only parameter in which the laser group showed significantly higher benefits was at week 15 for resting pain (mean between-group differences at visit 2-0 = - 1.345, 95% CI = - 14.600 to 11.910). The results of our study point to a conclusion that both laser and shockwave therapy are effective in myofascial pain syndrome, though we found shockwave therapy to be somewhat more beneficial. Clinical trial registration number NCT03436459 ( https://clinicaltrials.gov/ct2/show/NCT03436459 ).

[Real Time Fuctional Magnetic Resonance Imaging Biofeedback: a New Generation of Neurotherapy].

The review summarizes the data related to the potential of the real time fMRI biofeedback (the rt-fMRI), a novel technology implementing instructing patients to modify the neural activity in the certain brain regions related to the disordered function. The recent positive results were gained for a treatment of the post-stroke impairments, the Parkinson disease, the pain syndrome, the tinnitus, the alcohol and nicotine abuse, the major depression, and phobias of contamination and spiders. The intervention Was found to be less promising for schizophrenia and nearly ineffective for the criminal antisocial personality disorder. The reliability of the results is mostly poor due to suboptimal study designs, lack of the control groups, and insufficient sample sizes. The article deals with biological basis of the technology, its current applications and perspectives; and also its method- ologicdl and methodical problems.

Evidence for the Use of Ischemic Compression and Dry Needling in the Management of Trigger Points of the Upper Trapezius in Patients with Neck Pain: A Systematic Review.

The aim of this review was to describe the effects of ischemic compression and dry needling on trigger points in the upper trapezius muscle in patients with neck pain and compare these two interventions with other therapeutic interventions aiming to inactivate trigger points. Both PubMed and Web of Science were searched for randomized controlled trials using different key word combinations related to myofascial neck pain and therapeutic interventions. Four main outcome parameters were evaluated on short and medium term: pain, range of motion, functionality, and quality-of-life, including depression. Fifteen randomized controlled trials were included in this systematic review. There is moderate evidence for ischemic compression and strong evidence for dry needling to have a positive effect on pain intensity. This pain decrease is greater compared with active range of motion exercises (ischemic compression) and no or placebo intervention (ischemic compression and dry needling) but similar to other therapeutic approaches. There is moderate evidence that both ischemic compression and dry needling increase side-bending range of motion, with similar effects compared with lidocaine injection. There is weak evidence regarding its effects on functionality and quality-of-life. On the basis of this systematic review, ischemic compression and dry needling can both be recommended in the treatment of neck pain patients with trigger points in the upper trapezius muscle. Additional research with high-quality study designs are needed to develop more conclusive evidence.

Ultrasound imaging of embedded shrapnel facilitates diagnosis and management of myofascial pain syndrome.

Trigger points can result from a variety of inciting events including muscle overuse, trauma, mechanical overload, and psychological stress. When the myofascial trigger points occur in cervical musculature, they have been known to cause headaches. Ultrasound imaging is being increasingly used for the diagnosis and interventional management of various painful conditions. A veteran was referred to the pain clinic for management of his severe headache following a gunshot wound to the neck with shrapnel embedded in the neck muscles a few years prior to presentation. He had no other comorbid conditions. Physical examination revealed a taut band in the neck. An ultrasound imaging of the neck over the taut band revealed the deformed shrapnel located within the levator scapulae muscle along with an associated trigger point in the same muscle. Ultrasound guided trigger point injection, followed by physical therapy resolved his symptoms. This is a unique report of embedded shrapnel and coexisting myofascial pain syndrome revealed by ultrasound imaging. The association between shrapnel and myofascial pain syndrome requires further investigation.

Effects of different physiotherapy applications on pain and mobility of connective tissue in patients with myofascial pain syndrome.

OBJECTIVES: The purpose of this study was to investigate the effects of electrotherapy and exercise on pain intensity and mobility of connective tissue in patients with myofascial pain syndrome (MPS) in their cervical region. METHODS: 60 patients were divided into 3 groups using a random allocation programme method. A hotpack was applied, and ultrasound was carried out on the patients in the treatment group who were also given exercise training. Exercise training was only given to the exercise group while the control group was given two weeks rest. The demographic characteristics, autonomic symptoms, and other MPS-associated symptoms of patients were recorded. The Short-Form McGill Pain Questionnaire was used to evaluate the intensity and quality of pain, and a skin-roll test was used to evaluate connective tissue mobility. RESULTS: There was a statistically significant difference between treatment and control group on the sensory pain, total pain, and Visual Analog Scale measurements (p< 0.05). There was a decrease in connective tissue sensitivity measurements in the treatment and control groups. The connective tissue tension measurements were also decreased after treatment in the treatment and exercise groups. CONCLUSION: We concluded that combined treatment was more effective to decrease pain intensity, and increase connective tissue mobility.

[Observation on therapeutic effect of myofascial pain syndrome of the back in the military soldiers treated with moxibustion].

OBJECTIVE: To provide a set of the self-help and mutual-aid treatment with moxibustion to deal with myofasicial pain syndrome (MPS) of the back for the military soldiers. METHODS: Fifty-eight cases were randomly devided into a moxibustion group (30 cases) and a plaster application group (28 cases). In the moxibustion group, the suspended moxibustion was applied to Yanglingquan (GB 34) for 15 min. The moxibustion massage device was used to massage the pain area. Under the physician's guides, the self-help or mutual-aid treatment was adopted. In the plaster application group, Goupi Gao (a black plaster used in TCM) was used on the local pain area. The treatment was given once every day in either group, lasting for 5 days. The clinical symptom scale, clinical physical sign scale, functional disturbance scale, functional disturbance index, comprehensive economic benefit and the others were adopted to analyze and compare the clinical efficacies between the two groups. RESULTS: Both moxibustion and the plaster application achieved a certain efficacy on MPS of the back in the soldiers and either of them received the obvious improvements in the clinical symptoms, physical signs and functional disturbance (P < 0.01, P < 0.05). The results in the moxibustion group were superior to those in the plaster application group (P < 0.01, P < 0.05). In terms of the comprehensive economic benefit index, the result in the moxibustion group was better than that in the plaster application group. The total effective rate was 96.7% (29/30) in the moxibustion group and was 35.7% (10/28) in the plaster application group. The efficacy in the moxibustion group was superior to that in the plaster application group (P < 0.01). CONCLUSION: The self-help or mutual-aid treatment with moxibustion achieves the satisfactory clinical efficacy on MPS of the back in the military soldiers. It reduces the conventional medical cost and the military medical expenditure. This therapeutic approach is suitable to be promoted in the military.

The effect of cetylated fatty esters and physical therapy on myofascial pain syndrome of the neck.

Participants with Myofascial Pain Syndrome (MPS) of the neck were randomly assigned into 2 groups of the double-blinded study: topical cetylated fatty ester complex (CFEC) cream application plus physical therapy (CF-PT; n=37), and placebo cream application plus physical therapy (PL-PT; n=35). There were 3 visits during 4 weeks of treatment. Physical Therapy (PT), given twice/week, included Ischaemic Compression, Deep Pressure Trigger Point Massage and Myofascial Releases. Topical cream [CFEC cream (5.6%) and 1.5% menthol] or placebo cream [1.5% menthol, in a cream base] was applied twice/day. CF-PT provided the fastest and most effective study treatment modality. The addition of CFEC cream to PT resulted in statistically significant improvements, compared to PL-PT, for reduction of pain, neck disability and life quality indicators. Our results indicate that cetylated derivatives of fatty acids can effectively reduce pain and symptoms associated with neck MPS, when combined with physical therapy.

Sphenopalatine ganglion interventions: technical aspects and application.

Recent research has highlighted the important role of the sphenopalatine ganglion (SPG) in cerebrovascular autonomic physiology and in the pathophysiology of cluster and migraine headaches as well as conditions of stroke and cerebral vasospasm. The relatively accessible location of the SPG within the pterygopalatine fossa and the development of options for minimally invasive approaches to the SPG make it an attractive target for neuromodulation approaches. The obvious advantage of SPG stimulation compared to ablative procedures on the SPG such as radiofrequency destruction and stereotactic radiosurgery is its reversibility and adjustable features. The on-going design of strategies for transient and continuous SPG stimulation on as needed basis using implantable SPG stimulators is an exciting new development which is expected to expand the clinical versatility of this technique.

Electrical stimulation of sphenopalatine ganglion for acute treatment of cluster headaches.

INTRODUCTION: Cluster headaches (CH) are primary headaches marked by repeated short-lasting attacks of severe, unilateral head pain and associated autonomic symptoms. Despite aggressive management with medications, oxygen therapy, nerve blocks, as well as various lesioning and neurostimulation therapies, a number of patients are incapacitated and suffering. The sphenopalatine ganglion (SPG) has been implicated in the pathophysiology of CH and has been a target for blocks, lesioning, and other surgical approaches. For this reason, it was selected as a target for an acute neurostimulation study. METHODS: Six patients with refractory chronic CH were treated with short-term (up to 1 hour) electrical stimulation of the SPG during an acute CH. Headaches were spontaneously present at the time of stimulation or were triggered with agents known to trigger clusters headache in each patient. A standard percutaneous infrazygomatic approach was used to place a needle at the ipsilateral SPG in the pterygopalatine fossa under fluoroscopic guidance. Electrical stimulation was performed using a temporary stimulating electrode. Stimulation was performed at various settings during maximal headache intensity. RESULTS: Five patients had CH during the initial evaluation. Three returned 3 months later for a second evaluation. There were 18 acute and distinct CH attacks with clinically maximal visual analog scale (VAS) intensity of 8 (out of 10) and above. SPG stimulation resulted in complete resolution of the headache in 11 attacks, partial resolution (>50% VAS reduction) in 3, and minimal to no relief in 4 attacks. Associated autonomic features of CH were resolved in each responder. Pain relief was noted within several minutes of stimulation. CONCLUSION: Sphenopalatine ganglion stimulation can be effective in relieving acute severe CH pain and associated autonomic features. Chronic long-term outcome studies are needed to determine the utility of SPG stimulation for management and prevention of CH.

[Functional somatic syndrome in dental practice].

Functional somatic syndromes (FSSs) are common in dental as well as medical practice. Many patients with unexplained symptoms in oro-maxillo-facial areas visit dentists, but they are not diagnosed and treated properly. Temporomandibular disorder, atypical facial pain, and glossodynia (burning mouth syndrome) are included in dental FSSs. These diseases overlap with each other and with FSSs in other organs, such as myofacial pain syndrome, tension-type headache, fibromyalgia, and chronic fatigue syndrome. They coexist with mental disorders, such as anxiety disorder, mood disorder, and somatoform disorder. Multidisciplinary and holistic approaches should be applied to dental FSSs; pharmacological therapy (antidepressants), physical therapy, and cognitive-behavioral therapy. Clinicians have to support a patient in"enjoying his/her life with symptoms". Dental specialists in "oral medicine" with psychosomatic viewpoints are now required.