In our next section, we will cover nociceptive pain, which we touched a little bit on in the last PowerPoint slide set. There are two main types of nociceptive pain. The first is somatic nociceptive pain, which is characterized as sharp, aching, or throbbing and is well localized to the area of injury. This can be musculoskeletal, for example, joint pain or myofascial pain. You can also have visceral nociceptive pain, which is characterized as dull, heavy, or aching. This can occur over a wide area, and usually this can stem from hollow organs or smooth muscle pain. In regards to somatic pain, patients can describe it differently depending on the depth of where the pain stimulation is coming from. For deep structures, they might describe it as dull or aching, and for superficial structures, they can say that it might be sharp. This again is localized and reproducible. Some of the causes of somatic pain can be tissue damage from skin, muscle, bone, or fascia and is mediated by the somatic nervous system. Some common somatic pain examples that a pain physician might encounter could be myofascial pain syndrome. There could be trigger points, neck and low back pain, which, as mentioned earlier, can be a mix with neuropathic pain. Patients can have arthritis, tendinitis, bursitis, muscle sprains, strains, or spasms. And also another common one that you'll see is bony metastasis or fractures. There are many more types of somatic pain examples, but these are the main ones that we will focus on and speak about today. A very common thing that pain physicians will see is called myofascial pain syndrome. This is soft tissue pain syndrome with local and referred pain arising from trigger points. Some people call it the great mimicker. With local soft tissue pain, that can include bursitis, tenosynovitis. With regional soft tissue pain, that can include myofascial pain syndrome, which we're talking about here, and complex regional pain syndromes, types 1 and 2. And then there's also a generalized soft tissue pain, which includes fibromyalgia, chronic fatigue syndrome, and hypermobility syndromes. Usually with myofascial pain syndrome, patients will have a normal ESR, and they'll have no histological, biochemical, or serological abnormalities. A lot of people will wonder, what is the difference between a trigger point and a tender point? Here you can see a trigger point is an area of muscle that is painful to palpation and is characterized by the presence of a taut band and usually has a referral pattern of pain. Tender points are areas of tenderness occurring in muscles, muscle tendon junctions, bursa, or fat pads. A taut band is a band of shortened muscle fibers in which trigger points lift. Usually excessive acetylcholine leakage creates a dysfunctional implant, which leads to taut muscle band formation. In turn, you'll see chronically shortened sarcomeres, where spontaneous electrical activity occurs more often in these trigger points. And then you'll have a twitch response when needled or palpated. There's a thought on how trigger points are created called the integrated trigger point hypothesis. For that, you start with an initial muscular overload, such as malpositioning or overuse. With that, you'll have neuromuscular implant dysfunction, which can lead to excessive acetylcholine release. With that, you'll have prolonged depolarization of the postjunctural membrane with consecutive release and inadequate reuptake of calcium. The same muscle contraction by increased depolarization of the postjunctional implant can cause local hypoxemia and energy crisis, leading to a neurotransmitter and vasoactive substance release. The sarcomere shortening occurs due to a loop. The calcium is released, which leads to an increased metabolism, which, again, leads to sarcomere shortening, causing local anemic hypoxia, which results in a failed sarcoplasmic reticulum calcium pump, and thus the cycle continues. These are some common trigger points that a patient can have throughout their body. As you can see, they can occur throughout the head and neck musculature, the trapezius, in most places throughout the upper and lower extremities, as well as the glutes, chest, and lower back. A differential diagnosis of trigger point and myofascial pain syndrome can be myopathy, polymyositis, chronic syphilis, hypothyroidism, a nerve entrapment syndrome, fibromyalgia, which we often see, rheumatoid arthritis, subacute bacterial endocarditis, lupus, and other arthritides. When trying to diagnose myofascial pain syndrome, listening to the patient's history is very important. Sometimes they can describe an overuse injury or maybe an extended period of time of a patient being in a malposition when they're using their computer. For physical exam, we do a careful neurological exam, and we assess a lot of the myofascial components, such as a range of motion exam. We assess the region of chief complaint. We search for trigger points on palpation and then assess for associated phenomena, which includes local tenderness, taut bands, a local twitch response, and a jump sign. Sometimes they can also have a specific referral pattern from their trigger points. Again, a lot of times a myofascial pain syndrome can come from different perpetuating factors. For neck, trapezius muscles, we see it all the time for poor posture, abnormal biomechanics, poor ergonomic design of equipment, especially with COVID and people working from home, and deconditioning of various muscle groups. To treat myofascial pain, we can try to control the pain, try to restore range of motion to the specific area that is causing pain, restore strength, biomechanical function, and also activity-specific functions. Here you can see trying to adjust the ergonomic components of a maybe at-home computer setup for a person that's working from home would help them a lot with their myofascial pain. Specific treatments for myofascial pain can include oral medications, spray and stretch, which some people will use the cold spray and then stretch afterwards, trigger point injections or dry needling, which they can do with physical therapy, ischemic compression of that area, a myofascial release, exercise, aerobic conditioning, and also education on how to avoid future episodes of the myofascial pain. The theory of a trigger point injection is to physically break up the trigger point. It eliminates trigger points and top bands and can restore muscle length. By doing so, it can help restore normal biomechanics and try to decrease that cycle of re-injury that we were discussing earlier. Another very common area of nociceptive pain is neck pain and low back pain. For this talk, we'll cover mostly neck pain, but just know that a lot of the same components will deal with the low back. For non-musculoskeletal problems of the neck, you can see ENT issues, thyroid problems, vascular issues, oromaxifacial issues, and referred neck pain. For musculoskeletal problems, you can have degenerative disorders, myofascial-slash-muscular issues, which we kind of talked about previously, acute trauma, including sprain and strain, whiplash and related disorders, and repeated use or overuse syndromes. To quickly review the cervical spine anatomy, you have seven cervical vertebrae, eight cervical nerve roots. Z-joints are also facet joints, which consist of a superior and inferior articulate process. These are synovial joints, and they go from C2 down to T1 for the neck. Flexion and extension usually occur the greatest at C5-6 and C6-7 inner spaces. Lateral bending greatest at C3-4 and C4-5 levels. The Z-joints at C2-3 are innervated by the superficial medial branch and the C3 dorsal ramus, which is the third occipital nerve. The Z-joints are innervated by the medial branches at the level above and below the joint from C3-4 down to C7-T1. The unconvertebral joints, or UV joints, are between C3 through 6 levels. And then for that, you'll have OA changes that may narrow the intervertebral foramina. In the picture on the right, you can see the small circular areas called the intervertebral foramina. The largest one at the very top is C2-3, and they progressively decrease in size to C6-7, which decreases with extension. Radicular complex, that accounts for 20 to 35% of the cross-sectional areas of the intervertebral foramina. You also have your dorsal root ganglia, the DRG, which resides in the proximal or distal to the midpoint of the pedicle. And in between the vertebrae, you have your intervertebral discs between C2 and through 7. The discs are composed of an outer disc annulus fibrosus, and the inner disc has the nucleus pulposus inside. At each end of the vertebral body consists of the vertebral endplate. Each disc is covered superiorly and inferiorly by these strong bonds. In the endplates, you'll have no susceptive nerve endings. In the front or anterior side of the vertebral end, the disc component is the anterior longitudinal ligament, which is thicker over the disc. This blends with the annulus and limits C-spine extension. On the posterior aspect of that complex is the posterior longitudinal ligament, which prevents hyperflexion of the spine and posterior protrusion of the discs. When looking at causes of neck pain or musculoskeletal pain in the neck, there can be many components. Some pain generators are from the intervertebral discs, ligaments, muscles, nerve roots and branches of those nerves, the facet joints, and vertebral processes and structures. The physical exam is very important when trying to determine which one of these structures is the source of the pain. We look at neck range of motion with flexion, extension, side bending, and rotation. We palpate over the spinous processes and over the paraspinal musculature going down into the trapezius muscles. We do a few provocative tests to see if we can aggravate some of the pain and recreate it. We also look at neurological exams to determine strength, sensation, reflexes, et cetera. Diagnoses of the neck pain can be, and not all-inclusive, can be radiculopathy, degenerative joint disease slash degenerative disc disease, whiplash syndrome, myofascial pain syndrome, fracture or dislocation, sprain or strain. The other type of nociceptive pain that we were describing earlier is called visceral pain. Patients can describe this as crampy and dull. A lot of times they have difficulty with describing the location, and the pain can be referred. Causes of visceral pain can include internal structures such as organs, and it is mediated by autonomic nervous system. There can be many causes of visceral pain throughout the body, but some common ones that you might see are endometriosis, interstitial cystitis, chronic pancreatitis, chronic prostatitis, chronic pelvic ping, gastroparesis, IBS, as well as IBD. To treat some of these visceral pain syndromes, we can try some interventional procedures such as a sympathetic nerve block. These include celiac plexus nerve blocks as well as superior ganglion nerve blocks. We will describe these more in depth in the interventional lecture to follow. To treat a lot of our nociceptive pain, we can try different medications, which include NSAIDs or acetaminophen, antispasmodics, gabapentin or pregabalin, as well as some antidepressants including tricyclic antidepressants and SNRIs. We will talk more about these in our pharmacology lecture.

nociceptive pain

somatic nociceptive pain

visceral nociceptive pain

myofascial pain syndrome

diagnosis and treatment options