Central and Peripheral Neural Targets for Neurostimulation of Chronic Headaches

The Evolution of Neuromodulation in the Treatment of Chronic Pain: Forward-Looking Perspectives

Background

The field of neuromodulation is continually evolving, with the past decade showing significant advancement in the therapeutic efficacy of neuromodulation procedures. The continued evolution of neuromodulation technology brings with it the promise of addressing the needs of both patients and physicians, as current technology improves and clinical applications expand.

Design

This review highlights the current state of the art of neuromodulation for treating chronic pain, describes key areas of development including stimulation patterns and neural targets, expanding indications and applications, feedback-controlled systems, noninvasive approaches, and biomarkers for neuromodulation and technology miniaturization.

Results and Conclusions

The field of neuromodulation is undergoing a renaissance of technology development with potential for profoundly improving the care of chronic pain patients. New and emerging targets like the dorsal root ganglion, as well as high-frequency and patterned stimulation methodologies such as burst stimulation, are paving the way for better clinical outcomes. As we look forward to the future, neural sensing, novel target-specific stimulation patterns, and approaches combining neuromodulation therapies are likely to significantly impact how neuromodulation is used. Moreover, select biomarkers may influence and guide the use of neuromodulation and help objectively demonstrate efficacy and outcomes.

Repetitive Peripheral Magnetic Stimulation (rPMS) in Subjects With Migraine-Setup Presentation and Effects on Skeletal Musculature

Purpose: Repetitive peripheral magnetic stimulation (rPMS) has been successfully applied recently in migraineurs to alleviate migraine symptoms. Symptom relief has been achieved by stimulating myofascial trigger points (mTrPs) of the trapezius muscles, which are considered part of the trigemino-cervical complex (TCC). However, effects on musculature have not been assessed in detail, and the specificity of effects to muscles considered part of the TCC yet has to be elucidated. Against this background, this study presents the setup of rPMS in migraine and evaluates effects on skeletal musculature. Materials and Methods: Thirty-seven adults (mean age: 25.0 ± 4.1 years, 36 females) suffering from migraine and presenting mTrPs according to physical examination underwent rPMS either to mTrPs in the trapezius muscles (considered part of the TCC; n = 19) or deltoid muscles (considered not part of the TCC; n = 18) during six sessions over the course of 2 weeks. Standardized questionnaires were filled in to assess any adverse events and experience with rPMS as well as satisfaction and benefits from stimulation. Algometry was performed to evaluate changes in pressure pain thresholds (PPTs). Results: All stimulation sessions were successfully performed without adverse events, with 84.2% of subjects of the trapezius group and 94.4% of subjects of the deltoid group describing rPMS as comfortable (p = 0.736). Muscular pain or tension improved in 73.7% of subjects of the trapezius group and in 61.1% of subjects of the deltoid group (p = 0.077). PPTs of the trapezius muscles clearly increased from the first to the last stimulation sessions-regardless of the stimulated muscle (rPMS to the trapezius or deltoid muscles). However, depending on the examined muscles the increase of PPTs differed significantly (subjects with stimulation of trapezius muscles: p = 0.021; subjects with stimulation of deltoid muscles: p = 0.080). Conclusion: rPMS is a comfortable method in migraineurs that can improve local muscular pain or tension. Furthermore, it is able to increase directly and indirectly the PPTs of the trapezius muscles (considered part of the TCC) when applied over mTrPs, supporting the role of the TCC in migraineurs.

Radiological anatomy assessment of the fissura pterygomaxillaris for a surgical approach to ganglion pterygopalatinum

The ganglion pterygopalatinum has become a therapeutic target to treat various pain syndromes in recent years. It is located in the fossa pterygopalatina, and the fissura pterygomaxillaris is the main access to surgically approach this structure. Recently, the neuromodulation of the ganglion pterygopalatinum by microstimulator implantation has become the first therapeutic line in refractory cluster headache treatment. This invasive technique is performed transorally through the fissura pterygomaxillaris, and is limited by the size of the implantation device, which requires an opening of at least 2 mm. Therefore, extensive knowledge about the anatomy of the fissura pterygomaxillaris prior to surgery is necessary to predict the success of both the approach and intervention. Likewise, establishing a morphological typology of the different fissura pterygomaxillaris variations would be a valuable predictive tool in the clinical practice. In this work, an anatomical analysis was performed of the morphological characteristics of the 242 fissurae pterygomaxillares, which corresponded to 121 adult patients, 58 males and 63 females, aged between 18 and 87 years. For each subject, right and left fissures were studied with radiological computed tomography images. Aperture fissura pterygomaxillaris measurements were taken in an upper (Measure A), middle (Measure B) and lower craneo-caudal third (Measure C). Intra-subject differences were studied between the measurements taken of each patient's right and left fissures, and the inter-subject measures in which fissures were compared according to patients' age and gender. The obtained results showed no significant differences between each patient's right and left fissures in any three measurements taken. Intra-subject differences were not significant for gender or age. No statistically significant differences were found for the inter-subject measures between the measures of fissures according to patients' age. However, our data revealed that males' fissurae pterygomaxillares were significantly larger than those of females in all three measures. Having analysed fissures, a typological classification was made according to the morphological patterns found. A 2-mm limiting measure was considered, and Measures A, B and C of each fissure were classified depending on whether they had a value above or equal to 2 mm, or below 2 mm. With this classification criterion, four fissurae pterygomaxillares types were obtained. Type I and II fissure values (with a higher prevalence) were equal to or were greater than 2 mm in all three measures, or in two measures. Type III fissure values were only greater than or equal to 2 mm in Measure A, whereas all the Type IV fissure values were below 2 mm. Future studies are necessary to correlate the fissure types successfully proposed in the surgical ganglion pterygopalatinum approach.