By Dr. Ira L. Shapira, DDS, D,ABDSM, D,AAPM, FICCMO
Dr. Ira L. Shapira's work in neuromuscular dentistry focuses on the complex relationship between the trigeminal nervous system, the autonomic nervous system, and their influence on conditions like TMJ disorders, headaches, and sleep health. His interest in the Sphenopalatine Ganglion (SPG) Block began after a patient introduced him to "Miracles on Park Avenue." This led to Dr. Shapira exploring this area and becoming an advocate for self-administration.
The SPG Block is a technique that targets the Sphenopalatine Ganglion with a local anesthetic. The results are often significant. Dr. Shapira often tells patients and writes that "The SPG Block turns off the sympathetic overload fight or flight response and lets the parasympathetic system dominate causing relaxation and sense of well being".
The SPG: A Crossroads of Autonomic Influence
The SPG, the largest parasympathetic ganglion in the head, is a key intersection of the autonomic nervous system's sympathetic and parasympathetic divisions. According to Dr. Shapira's paper, "Sympathetic innervation from the superior sympathetic chain passes thru the SPG to the trigeminal and facial nerves." This anatomical fact is essential for understanding the effects of the SPG Block.
Differentiating GVA, Sympathetic, and Parasympathetic Afferents
The autonomic nervous system uses General Visceral Afferent (GVA) fibers to send sensory information from the body's internal environment to the central nervous system. These GVA fibers are part of the visceral nervous system, traveling with both sympathetic and parasympathetic nerves.
- Sympathetic GVA Fibers: These fibers travel with sympathetic nerves from the thoracolumbar spinal cord segments. They primarily detect pain, pressure, and chemical changes related to "fight-or-flight" responses. They do not synapse in the sympathetic ganglia but pass through to the spinal cord.
- Parasympathetic GVA Fibers: These afferents travel with cranial nerves, especially the vagus nerve (CN X), and sacral spinal nerves. They relay information about "rest-and-digest" functions like organ distension and chemical changes during periods of calm. The vagus nerve (CN X) accounts for a large part of this parasympathetic afferent input.
- Central Convergence: Both sympathetic and parasympathetic GVA fibers converge and synapse at the Nucleus of the Solitary Tract (NST) in the brainstem. This nucleus integrates the incoming visceral information before relaying it to the hypothalamus, amygdala, and insular cortex.
The Vagus Nerve and the Trigemino-Cardiac Reflex (TCR)
The vagus nerve influences the autonomic balance, including pathways related to the SPG, despite not directly innervating it. The vagus nerve is a major part of the parasympathetic nervous system, and its afferent fibers project to the NST, affecting many of the same brain centers as the SPG. Thus, modulating the SPG can significantly impact the autonomic balance. This is crucial for managing conditions such as anxiety and depression, where the autonomic nervous system is often dysregulated.
The trigeminal nerve can trigger the Trigemino-Cardiac Reflex (TCR). The TCR, is defined as "the sudden onset of parasympathetic dysrhythmias, sympathetic hypotension, apnea, or gastric hypermotility during central or peripheral stimulation of any of the sensory branches of the trigeminal nerve." The trigeminal nerve is the afferent pathway of the TCR, and the vagus nerve is the efferent pathway. Dr. Shapira emphasizes the interconnectedness of these systems, stating that, "Severe Bruxism/ Neuromuscular Dentistry/ Dental Sleep Medicine/ TrigeminoCardiac Reflex and SPG Blocks are all connected and part of the same system."
Neuromodulation for Healing
Dr. Shapira's approach in neuromuscular dentistry directly addresses these connections. He uses Ultra-Low Frequency Transcutaneous Electrical Nerve Stimulation (ULF-TENS) (specifically the Myomonitor) to relax musculature and provide neuromodulation. According to Dr. Shapira, "The effects of ULF-TENS on the autonomic nervous system act on the Limbic System and Hypothalamus (H-P-A) to address Axis II issues during neuromuscular dental procedures." The positioning of the SPG on the maxillary division of the trigeminal nerve means that ULF-TENS also directly neuromodulates the SPG. This approach combines restoring a physiologic bite with neuromodulation via ULF-TENS and SPG Blocks, which can lead to healing and improve the quality of life for patients. Dr. Shapira says, "I am always delighted when I see patients blossom in unexpected ways after eliminating sleep and pain issues." This approach can help the body heal and restore autonomic balance, a "Miracle Block" for those with chronic pain and autonomic dysregulation.
