Originally published at CRANIO® The Journal of Craniomandibular & Sleep Practice
ISSN: 0886-9634 (Print) 2151-0903 (Online) Journal homepage: https://www.tandfonline.com/loi/ycra20
2019, VOL. 37, NO. 3, 201–206
Neuromuscular dentistry and the role of the autonomic nervous system: Sphenopalatine ganglion blocks and neuromodulation. An International College of Cranio Mandibular Orthopedics (ICCMO) position paper
Ira L. Shapira DDS, D, ABDSM, D, AAPM, FICCMO, MICCMO
Regent, Master & Fellow, International College of Cranio Mandibular Orthopedics (ICCMO), Private Practice, Delany Dental Care, Gurnee, IL and Think Better Life, Highland Park, IL, USA
Sphenopalatine Ganglion (SPG) Block; Sphenopalatine Ganglion (SPG) Neuromodulation; ULF-TENS; Trigeminal Autonomic Nervous system; Neuromuscular Dentistry
The sphenopalatine ganglion (SPG) holds a key position in the treatment of a wide variety of chronic head and neck pain. The SPG Block can be addressed directly with anesthetic blocks or indirectly with neuromodulation/ stimulation and by establishing a neuromuscular physiologic rest position.
Objective: To examine the role of the sphenopalatine ganglion in the diagnosis and neuromuscular treatment of temporomandibular disorders and other head and neck pain.
The following questions will be examined and addressed by a review of relevant literature:
- Why is neuromuscular dentistry so effective in treating TMJ disorders and related pain disorders?
- What is the role of ULF-TENS and what is the effect of its use on the sphenopalatine ganglion?
- Does neuromuscular dentistry address Axis 2 (H-P-A) as simultaneously with Axis 1 treatment compared to other mechanical approaches?
- TMJ disorders are often called “The Great Imposter” because they can mimic many wide and diverse disorders; is this related to the autonomic nerves associated with the sphenopalatine ganglion?
- Does the use of sphenopalatine ganglion blocks have an independent place in the armamentarium of neuromuscular dentists?
This paper will explore those questions, which will require a review of relevant neurological concepts. I will specifically concentrate on the autonomic nervous system and the sphenopalatine ganglion.
The sphenopalatine ganglion (SPG) is the largest parasympathetic ganglion of the head. The SPG should be considered an important part of the brain even though it is located within the pterygopalatine fossa (not the cranial vault) on the maxillary division of the trigeminal nerve. The maxillary artery is also located within the pterygopalatine fossa. The sphenopalatine ganglion is known by several names, including the nasal ganglion, Sluder’s ganglion, the pterygopalatine ganglion (due to location), and Meckel’s ganglion.
According to Ho, et al. , the sphenopalatine ganglion “is the largest and most superior ganglion of the sensory, sympathetic and parasympathetic nervous system. It has the largest collection of neurons in the calvarium outside of the brain. It is also the only ganglion having access to the outside environment through the nasal mucosa. SPG gives rise to greater and lesser palatine nerves, nasopalatine nerves, superior, inferior and posterior lateral nasal branches, as well as the pharyngeal branch of the maxillary nerve. There are also orbital branches reaching the lacrimal gland.” The excellent reference list from Ho’s article  is recommended for anyone wishing to better understand sphenopalatine ganglion treatment possibilities.
The access of the sphenopalatine ganglion to the outside environment via the nasal mucosa is critically important, as it led Dr. Greenfeld Sluder [2–4] to the early understanding of the importance of the SPG. His early work with remote dysfunction associated with the SPG was a leap in a new direction into understanding the autonomic foundations for pain and other dysfunctions. Sluder’s or sphenopalatine neuralgia was first described by Sluder in 1908. It is now believed he was describing either a TMJ disorder or cluster headache, the symptoms of which were relieved by a nasal cocaine (10% solution) block. Sluder  published the first medical textbook on Nasal Neurology while he was Chairman of Otolaryngology of Washington University School of Medicine in 1927.
Dr. Hiram Byrd  published his paper on remote dysfunction treatment and the sphenopalatine ganglion in the 1930 Annals of Internal Medicine, looking at 10,000 sphenopalatine ganglion blocks in 2000 patients. Byrd’s work explains why the sphenopalatine ganglions autonomics nerves could underlie the reason “TMJ Disorders are often called ‘The Great Imposter’ because they can mimic many wide and diverse disorders” and whether “this is related to the autonomic nerves associated with the sphenopalatine ganglion.” It is important to note that Dr. James Costen’s papers [6– 10] describing TMJ disorders were published after the Byrd article, so TMJ disorders were not referenced. Common symptoms he discussed were ear pain, tinnitus, and impaired hearing.
TMJ patients frequently experience pain in, around, and behind the eye, which are innervated by the ophthalmic branch of the trigeminal nerve, whose branches carry the sympathetic and parasympathetic autonomic fibers from the sphenopalatine ganglion [3–5]. Byrd  reported relief of pain with SPG block of iritis pain, keratitis pain, interstitial keratitis pain associated with syphilis, conjunctivitis pain, blepharospasm, conjunctivitis pain, photophobia, pain from traumatic ulcer of the cornea, optic neuritis pain, and excessive lacrimation. Sluder discussed eye pain in detail in his books [4,5].
Another common type of pain in TMD patients is ear pain and other ear dysfunctions. This can often be traced to internal TM joint derangements, capsulitis, retrodiscitis, and referred pain from myofascial trigger points [7,11], or the pain can originate in inner ear structures. Byrd  reported SPG block relief of the pain of otitis media (middle ear infection), chronic otorrhea, otalgia, mastoid pain, itching of the external auditory canal, and relief of tinnitus aureum, which more recent authors have attributed to increased tension in lateral pterygoid muscles , a common TMD issue . Other otologic symptoms cited by Byrd include progressive deafness, sense of fullness of the ear (both allergic and non-allergic), pain in the external auditory canal associated with fungal infection, pain of herpes zoster, confirmed in a newer study, which showed that a sphenopalatine ganglion blockade can be employed in the treatment and prevention of sinus (cardiac) arrest associated with postherpetic trigeminal neuralgia .
Byrd  reported relief of many ear, nose, throat, and sinus conditions in response to SPG blocks, including relief of sinus pain from ethmoid, maxillary, and frontal sinuses, which are innervated by the maxillary division of the trigeminal nerve where the sphenopalatine ganglion is located within the fossa. Other symptoms treated include rhinorrhea; acne; rosacea; toothache in maxillary teeth; dysgeusia (parageusia), i.e., a distortion of the sense of taste, such as metallic taste, burning and/or itching on the roof of the mouth; pain of Vincent’s angina, commonly known as “trench mouth”; acute necrotizing ulcerative gingivitis; and glossodynia, i.e., burning pain (unilateral) on the roof of the mouth; and many more.
It must be clearly understood that there is a great deal of commonality in both the symptoms and innervations of all of these problems. The trigeminal nerve is key. It is the dentist’s nerve, and without a doubt, dentists have more experience with the fifth cranial nerve than any other specialty of medicine.
Newer research into the sphenopalatine ganglion is not limited to doing anesthetic blocks but also looks at neuromodulation of the sphenopalatine ganglion to treat this same wide range of disorders that overlap dentistry, ophthalmology, otolaryngology, and neurology. An excellent paper by Ho et al.  gives an excellent review of sphenopalatine ganglion blocks, ablation, and neuromodulation.
Neuromodulation is an exciting “new” approach to dealing with many of the problems previously discussed. It is very important to stress that neuromodulation of the sphenopalatine ganglion is really not “new” but has been safely utilized for over 50 years in the field of neuromuscular dentistry. Dr. Bernard Jankelson created the Myomonitor (Myotronics, Seattle WA, USA), ultra-low frequency TENS (ULF-TENS) that stimulates the trigeminal nerves bilaterally and, simultaneously, also stimulates the sympathetic and parasympathetic nerves associated with the sphenopalatine ganglion, where it sits on the maxillary division of the trigeminal nerve within the pterygopalatine fossa. Heit et al.  answered question three, “Does Neuromuscular Dentistry address Axis 2 (H-P-A) as simultaneously with Axis 1 treatment compared to other mechanical approaches?” in her landmark paper published in CRANIO on cerebral blood flow. Heit’s paper further went to show that the neuromuscular physiologic rest position achieved by neuromuscular occlusion can maintain changes in cerebral blood flow on a long-term basis. Heit’s work gives a definitive rationale for considering long-term occlusal changes in the treatment of TMD patients to maintain a healthy physiologic rest position .
In a recent article, Akbas et al.  showed that “pulsed radiofrequency treatment” of the sphenopalatine ganglion was effective in treating chronic head and facial pain.
Sphenopalatine ganglion stimulation to treat cluster headaches, an autonomic trigeminal cephalalgia, was evaluated by Schoenen et al. , who reached the conclusion that “patient-controlled electrical stimulation of the SPG is an effective treatment option for cluster headache sufferers with an acceptable safety profile.” Neuromuscular dentists have been utilizing trigeminal/sphenopalatine ganglion stimulation with the Myomonitor and the BNS 40 personal TENS unit. The Myomonitor addresses the myofascial component of pain not affected by SPG blocks [17,18]. Schoenen et al.  also concluded that “The efficacy data indicate that acute electrical stimulation of the SPG provides significant attack pain relief, and in many cases, pain freedom compared to sham stimulation.”
It is interesting to note that published literature of the effects of SPG blocks on fibromyalgia and myofascial pain and dysfunction have shown minimal response [17,18]. This is quite different from the effects the author has observed in treating patients, but a different mode and frequency of delivery of the SPG blocks is utilized.
These studies were done with an ATI implanted device. The authors concluded that, “Electrical stimulation of the SPG was also observed to be associated with a significant and clinically meaningful reduction in Cluster Headache attack frequency in some patients. The preventive effect is important in Chronic Cluster Headache and warrants further investigation. Overall, SPG stimulation significantly improves quality of life in these very disabled patients.” This is exactly one of the treatments that neuromuscular dentists provide as part of the neuromuscular approach.
Treatment of TMJ disorders requires accurate diagnosis of both structural and physiological balance or homeostasis. This is considered as the Axis 1 of the Research Diagnostic Criteria for TMD (RDC/TMD) ; Axis 2 is pain-related disability. This is often assumed to be identical to psychosocial predictors of high pain-related disability. Axis 2 is usually related to high-stress response issues. Pain is a high-stress emotional issue. Axis 2 is an implied diagnosis of a psychiatric nature being an underlying cause of the pain disorder; this is often called the biopsychosocial model of TMD disorders.
Axis 2 is often referred to as the H-P-A axis or the hypothalamus-pituitary-adrenal axis. This is where the autonomic system, and in particular, the sympathetic and parasympathetic fibers that pass through sphenopalatine ganglion play their role. These SPG-related nerves are the main highway into the limbic system of the brain.
This is very important in the field of pain management because pain is an emotional response, i.e., pain is an emotion perceived in the limbic system. The reticular activating system (RAS) amplifies input from the trigeminal nervous system, especially those connected to noxious input and sympathetic stress. This RAS amplified input feeds into the hypothalamus, which releases corticotropin-releasing factor (CRF). CRF causes the anterior pituitary to release adrenocorticotropic hormone (ACTH). This ACTH hits adrenal receptors and results in the release of cortisol, the stress hormone. This is one part of the process of turning on central sensitization. The increasing levels of cortisol should provide negative feedback through the pituitary to shut off cortisol production. High cortisol levels have been linked with chronic fatigue syndrome and sleep–wake disturbances common in patients with TMJ disorders. Disturbances in sleep patterns can disrupt normal hypothalamic function, leading to increased stress responses, another factor in central sensitization. This system fails when there are high levels of continual chronic stress [20,21]. During high periods of stress, the adrenal medulla will also release the catecholamines, epinephrine, and norepinephrine as part of the “fight or flight” reflex. These powerful neurotransmitters have wide effects on both peripheral and central nervous system tissues.
The Amygdala is another important part of the limbic system that processes memory, especially memories associated with emotional responses, such as fear, pain, and anxiety . Pain is essentially an emotional response intimately tied to the amygdala functions. Negative input associated with bad memories and/or pain can serve to supercharge the H-P-A response, leading to central nervous system changes .
Electrical stimulation studies [23,24] of the right amygdala induce negative emotions, such as fear and sadness. Left side amygdala stimulation induces either pleasant (happiness) or unpleasant (fear, anxiety, sadness) emotions. The effect of blocking the SPG or stimulation to the sphenopalatine ganglion is primarily to the left side amygdala. In the author’s practice, high anxiety and stress reactions are reduced with SPG blocks, in addition to reductions in pain and producing a general feeling of well- being and even happiness. Some studies have shown children with anxiety disorders tend to have a smaller left amygdala . The Myomonitor’s effects will travel to higher levels of the brain via neural synapses.
The paired trigeminal nervous system is the largest input of all of the 12 cranial nerves. The trigeminal nerve has a sensory root that has cell bodies in the Gasserian or semilunar ganglion and a smaller motor root.
The sensory trigeminal nucleus extends through the whole of the midbrain, pons, medulla, and upper cervical spinal cord and is the largest trigeminal nuclei. The sensory trigeminal nucleus is divided into the mesencephalic nucleus [25–27], the chief sensory nucleus (primary nucleus, main sensory nucleus), and the spinal trigeminal nucleus. There is also a distinct motor nucleus .
The mesencephalic nucleus is home to proprioception of the trigeminal nervous system, including input from the periodontal ligament (including sympathetic fibers), input from muscle spindles, and muscles of mastication .
Neuromuscular dentistry is the ultimate tool for dentists trying to control proprioceptive input into the mesencephalic nucleus [25–29].
It utilizes ULF-TENS to stimulate a monosynaptic reflex [26–34] and create a simultaneous bilateral muscle pulse. This creates contraction and relaxation of the muscle fibers. Neuromuscular occlusion is based on bilaterally balanced occlusion achieved with the use of ULF-TENS. Occlusion includes head position, physiologic input from muscles, including muscle spindles, Golgi tendon organs, and the periodontal ligament. Rest position of the mandible can be considered one of the most important factors of occlusion [26,28,29,31–34].
The Myomonitor pulse will also pass along the maxillary nerve and to the nerves of the sphenopalatine ganglion and serve as a neuromodulation device to the sphenopalatine ganglion’s sympathetic and parasympathetic fibers as well as to its somatosensory fibers [1,25–27,34,35]. This pulse may also have effects on the sympathetic innervation of the periodontal ligament’s unmyelinated fibers that arise in the superior cervical sympathetic chain and pass thru the SPG.
Treatment of multiple disorders with SPG blocks points to the effectiveness of this treatment on stress-
related disorders or H-P-A (or Axis 2). One excellent example is the use of SPG blocks to treat “essential hypertension.” As reported in the International Journal of Cardiology in 2016 and 2018 [35,36], the blocks effectively treat approximately one-third of essential hypertension to eliminate the issue. This shows the effectiveness of SPG blocks for H-P-A issues.
There are numerous studies of both neuromodulation and blockage of the SPG in the treatment of cluster headaches and other trigeminal autonomic cephalalgias, including a 2016 article in Cephalalgia , which concluded that “The reported studies have demonstrated that SPG stimulation is a safe and effective treatment for chronic cluster headache.”
Another case report, in Headache, concluded “SPG block using a local anesthetic may be an effective treatment for patients with Hemicrania Continua, specifically for those who cannot tolerate indomethacin” . A 2009 paper in Headache concluded, “Radiofrequency ablation of the SPG is an effective modality of treatment for patients with intractable chronic cluster headaches” . An article by Mojica et al.  concluded: “SPG blockade is a safe and effective treatment for chronic headaches such as cluster headaches, migraines, and other trigeminal autonomic cephalalgias.” An article in CRANIO, in 1995, specifically referenced use of SPG blocks for treating TMJ disorders . A 2018 article discusses SSPG or suprazygomatic sphenopalatine ganglion block approach to treat status migrainosus by direct injection into the pterygopalatine fossa .
Published evidence of the effectiveness of blockade and neuromodulation of the sphenopalatine ganglion on multiple disorders has been given in the current paper to answer the question, “Why is Neuromuscular Dentistry so effective in treating TMJ disorders and related pain disorders?” While the primary use of ULF- TENS Myomonitor treatment is to address the somatosensory system of the facial and trigeminal nerves, the position of the sphenopalatine ganglion on the maxillary division of the trigeminal nerve leaves little doubt that it also acts as a neuromodulator of the SPG. Monaco et al.
- showed its effect on the autonomic nervous system in their landmark paper on the effects of ULF-TENS. It seems that part of the effectiveness of the treatment is due to the autonomic effects of the ULF-TENS.
As for the question, “Does neuromuscular dentistry address Axis 2 (H-P-A) as simultaneously with Axis 1 treatment compared to other mechanical approaches,” according to the aforementioned literature, there is a definite case for the use of ULF-TENS to affect the H-P-A axis and the associated biopsychosocial aspects of TMD disorders [16,43,44]. Neuromodulation of the SPG will affect the physiological aspects of chronic stress.
The question “TMJ Disorders are often called ‘The Great Imposter’ because they can mimic many wide and diverse disorders; is this related to the autonomic nerves associated with the sphenopalatine ganglion?” is answered by the work of Byrd , Sluder [2–4], and many others over the years. The articles by Byrd  and Ho  document a wide variety of remote dysfunctions of “The Great Imposter,” as possibly autonomic in nature (in whole or part), in addition to somatosensory issues.
Does the SPG Block belong in the practice of neuromuscular dentistry? Because dentists are the guardians of the trigeminal nervous system and the use of block and infiltration anesthesia is quite common in dentistry, the answer would appear to be a definitive “yes.”
Dental students have been taught to use palatal anesthetic routinely in their dental education, including the greater palatine foramen injection. In retrospect, SPG blocks were done “accidentally” with palatal anesthesia through the greater palatine foramen, which would give relief to sinus pain and sinus headaches. These blocks are part of “forgotten medicine.” Many very successful techniques fall to medical disuse as new techniques and procedures come along. Often excellent procedures are set aside as we search for the “magic pills” to cure disease. The immense amount of information on effectiveness did not prevent the sphenopalatine ganglion block from almost being lost.
This author’s results differ with published reports of effects of SPG blocks on myofascial pain [14,15]. I believe this has to do with the protocol for delivering the blocks. Many approaches call for a block in the physician’s office every two weeks. In contrast, this author teaches patients to self-administer the blocks on a daily basis (or more), initially. The other systems utilize blocks delivered by commercial devices like the TX 360® (Tian Medical LLC, Libertyville, IL, USA), the Sphenocath® (Dolor Technologies LLC, Salt Lake City, UT, USA), and the Allevio® (Jet Medical Inc., Schwenksville, PA, USA). These devices are basically squirting guns that deliver a single liquid dose of anesthetic. This author routinely teaches patients to self–administer with cotton-tipped catheters that offer a continual capillary feed of anesthetic as well as home use of the Sphenocath device in select patients. The technique allows the patient to continue with daily activities while the blocks are in place. The blocks are available on demand without trips to emergency rooms or doctors’ offices and, after initial appointments, are extremely affordable, approximately $1.00 per bilateral application.
Treatment of the autonomic nervous system through various approaches to the sphenopalatine ganglion can treat both Axis 1 and Axis 2 symptoms of temporomandibular disorders. Neuromuscular dentistry addresses both Axis 1 and Axis 2 of temporomandibular disorders.
Future study suggestions
- Experimental studies to examine the specific contribution of sphenopalatine modulation achieved during use of ULF-TENS as a contributory effect to neuromuscular occlusal treatment.
- Population studies to examine the effectiveness of sphenopalatine ganglion treatments on Axis 2 of temporomandibular disorders.
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Very interesting review indeed!
This is a crucial reference to support my Ophthalmic research.
How may I reach out to the author?