welcome to the lecture on interpreting pain neurophysiology my name is dr. Brook Coombs and as a musculoskeletal physiotherapist and having researched in chronic pain for several years this area is both daunting and fascinating so I hope though we can present this in a simple way so that you can continue to grow with your knowledge our learning objectives for this mini lecture are to describe the basic pathology that underpins different types of pain presentations we may see in clinical practice I'd like you to be able to interpret findings from the patient interview as evidence for greater or lesser involvement of a particular pain mechanism and we'll be just fine the use of pain reported patient reported outcomes or pros in assessing pain now our neuro physiological pain mechanisms our understanding has changed of neuro physiological pain mechanisms we now know that pain is not directly related to the extent of bodily damage and that pain can occur in the absence of bodily damage we've now moved to more other models which are recognized that pain is complex and has many contributors including cognitive emotional behavioral social and cultural dimensions and that has fits with our model of the ICF framework and our bio psychosocial models so in today's lecture I'd like you to think of a patient who presents to you with calf pain okay and we're going to go through a few different presentations of that may exist so firstly why study pain this is going to help us to better understand the pain experience of our patient it'll also help us to direct the interview and our physical examination and to inform our intervention and will also help to educate the patient about pain and the role of movement in treatment of pain now we're going to focus on those latter aspects of how we can education and manage pain in later parts of the course now there's different classifications of pain but this is a classification that's recently been presented by within the national strategic action plan for pain management and it calcifies groups things into three basic pain mechanisms nociceptive pain is caused by damage to body tissue it's usually described as sharp aching throbbing pain and it causes pause by a range of different things such as surgery arthritis osteoporosis and other musculoskeletal conditions neuropathic pain is a type of pain that occurs for long damage to the nervous system itself and the sensations are associated with this type of pain can be burning or shooting pains or numbness tingling or extreme sensitivity now the third term that is being now being used is no see plastic pain and it is essentially pain that's related to increased nervous system sensitization rather than actual tissue or nerve injury or threatened injury but firstly nociceptive pain as I said know so septic pain is caused by damage or injury to body tissue and this is common with bruises strains strains or burns so the pain generally follows within the expected healing process so movement would be expected to improve as the pain reduces as healing occurs there's a generally an on-off pattern to the pain so that specific movements or postures or activities are likely to be aggravated aggravate the pain and it responds well to simple pain relief so the key factors to draw from that that nociceptive pain has a history of tissue damage or injury and a strong relationship between pain and movement now we know that there are no pain receptors in the body but receptors that respond to mechanical inflammatory or ischemic stimuli and so we may actually further subcategorized nociceptive pain into mechanical inflammatory or ischemic type pain I'm going to just present Britta's briefly and the differences between these so if we go back to our case our patient presents and we see that they have a bruise and they describe a mechanism that lets leads us to believe that they've sustained a calf tear early on we might consider there to be inflammation involved in those local tissues which could sensitize the peripheral nerves peripheral receptors on the body chart we would expect more constant but probably varying pain it may be irritable and severe in terms of aggravating and easing factors it's going to be made worse by movement but there may be more latent pain so that the activities that you do may build up the pain may build up later in the day it generally will respond to any inflammatory medication and at nighttime there may be pain or pain on waking now after this first inflammatory phase has is progressed we may see more of a mechanical type pain and this is where pain and I body sharp we would see more localized and intermittent pain the descriptors might be sharp or dull or stabbing or pulling sensations it can range from mild moderate to severe in severity and it has a predictable response so stretching the calf of compressing it by palpating it or general movement is going to aggravate those symptoms generally it will respond to simple pain medication also and in terms of 24-hour pattern it's unlikely to be painful when you first wake but when rising and putting actually the weight through the foot that mechanical load will cause pain now the third category we just mentioned is ischemic paint nociceptive pain and this may be where there is a blockage to the artery such as peripheral arterial disease or it may be through compressive and exertional compartment syndrome where it is reducing the blood flow to the region the symptoms in such a case would generally be described as inter minute and they still follow a predictable pattern so it's repetitive activities or sustained postures that are going to aggravate ischemia type pain it's going to be eased by changing position or by ceasing that activity moving on now to our second type of pain which we considered neuropathic pain however a lot to highlight that the terms neuropathic and Nurik neurogenic pain are often used interchangeably neurogenic pain is often used to refer to a more transitory pain state meaning a pain that doesn't last as long so what is Cerner Apothic pain your Pathak pain is pain that arises from damage or disease to the nervous system itself the symptoms may be quite varied they may be due to impaired conduction within the nervous system such as numberless or tingling or they may present with extreme sensitivity for example burning and shooting pains and they may have Nakano sensitivity where the nerve is sensitive to movement now there's a big spectrum of injuries that were damaged that may fall within your Pathak pain it may be as quick as compressing the nerve for example if you hit your funny bone you can't send a shooting pain into the forearm or tingling or numbness it may because a forceful traction for example a thrower may employ induce traction on the ulnar nerve through the motions of cocking and throw or it may occur during surgery where assists an extensive injury occurs through severing of that nerve so key points of neuropathic pain are a history of lesion or disease of the nervous system itself or and a relationship between pain and nerve movement which as a service to mechanosensitive tivity so in our patient with calf pain we may have a scenario where they have sustained injury to the sciatic nerve Asha the buttock or in the hamstring or anywhere in the course of the site up nerve and it may present with referred pain to the calf as you can see in that patient there they're standing with their knee flexed and what we'll learn in later weeks is that if a nerve is mechanosensitive then anything that wants to stretch that nerve will put tension on that nerve may be hypersensitive an alternative is that patients with diabetic neuropathy may present with pain in the calf area we would probably expect that they would have also started with pain in the distal regions and that it has a bilateral symmetrical fashion which is known as the glove and stocking distribution so in this case the nerve insult is due to hyperglycemia affecting damaging the nerves peripheral nerves so if we think about the the nature of neuropathic pain on the body chart it may present as a burning shooting electric prick Payne they may have Percy's ear or anesthesia or dysesthesia okay symptoms that are more unusual and these are common in cases of patients with peripheral neuropathy now the symptoms are neuro anatomically logical for example if we have an injury to the spinal nerve roots the only we would expect a ridiculous tribution to that pain for example s one could refer to the calf if we had a peripheral nerve for example the sural nerve then it would follow a peripheral nerve distribution in the case of diabetes we see that glove and stocking distribution affecting the peripheral nerves severity may be more severe and resting pain may be also quite severe in terms of aggravating and easing factors there is stimuli still a stimulus response relate related nature to the problem in that it's aggravated by nerves stretch or compression or palpation eases it often doesn't ease as well with simple pain or anti-inflammatory medications and we may see that patients are actually on different types of analgesic medications for this reason Knight pain is common in patients with neuropathic pain now moving on to our third type of pain which is terms of no see plastic pain and within that the most common pathology or path pathophysiology that we're talking about is central sensitization now central sensitization is to find as an amplification of neural signaling within the central nervous system that elicits pain hypersensitivity now this hypersensitivity and central sensitization occur in different places within the central nervous system so it may occur in the dorsal Horn in the spinal cord Thermal thalamus or in the cortex and we're going to actually then in a moment actually talk about how it can be related to our cognitive some thoughts and feelings about pain so if we sum up know see plastic pain there is no clear evidence of tissue damage or injury all pain is disre portion --it - the amount of tissue damage or injury and there is a weak relationship between pain and mechanical stresses if we look at the features that we might find on our patient who presented with calf pain they will probably not describe pain as that shushing burning prickling feeling that we described when there was damage to the nerve but more often as a vague or a dull pain that is often quite diffuse in distribution so the location and if they have other sense treat symptoms is or is not neuron is neuro anatomically illogical okay so it doesn't follow that radicular or distribution or that peripheral nerve distribution that we saw when there was actually a nerve insult central sensitization causes patients to become actually show generalized hypersensitivity so it's sensitive to other stimuli such as hot and cold there's widespread head sensitivity particularly to touch so patients if they palpate might be sore in lots of different regions half hand strings feet areas patients with central sensitization are often going to be mechanosensitive on our neuro dynamic test so they have a heightened response to those tests these tests will actually be learning next week and patients with sensitization will often have nighttime now LinkedIn with central central sensitization is often these effective or cortical mechanisms cognitive mechanisms and these involve we're paying the pain response is related to a person's thoughts and emotions about the injury or about the the damage to the tissues and this may induce maladaptive responses to movement they may fear movement or re injury which is termed kinesio phobia or they may avoid activities leading to a for fear avoidance spiral of problems so in our patient with our calf injury their thoughts may be that I cannot do any walking I cannot do these things because my calf is torn it's going to rupture they may be believing that the damage is more than what it actually is now it's also very important for us to recognize that information from our history and about the nature of pain may also give us information about red flags so indicate systemic problems or losses in incident disorders so we're looking for patients who describe wakening at night so not just rolling onto an area and that we're mechanically that's inducing the pain but where the pain actually likes them if they have deep aching or throbbing we may be concerned if they have constant pain or waves of pain progressive or cyclic or similar symptoms and of course if they look unwell if they have fatigue weight loss weakness associated with their symptoms so going back to our calf pain our patient we may see that they look unwell and have had recent weight loss and refer on to find that they have a tibial osteosarcoma it may be in our observation that we see that the calf is very swollen and red or blanched and these may indicate complex regional pain syndrome or some other sympathetically maintained pains it's finally we're just going to move on to how we might actually assess pain neurophysiology and in research this is what we are commonly do and in some clinical practices it's also common practice we can use sensory testing to understand how the pain is what what sensory modalities are impaired either a loss of sensation or hypersensitive and so we might use an algal mat or to apply pressure and look at pain sensitivity to to pressure we may use vondre filaments to actually look for loss of sensation for example in patient with a diabetic neuropathy we can look at two-point discrimination we can look at firm or hyperalgesia so if they are sensitive to cold we may actually induce that by placing an ice cube over reproducing it by placing an ice cube over the area however we might also actually ask the patient to actually describe their pain and use validated questionnaires to give some insight to common ones are the pain detect which is for use for investigation of neuropathic like symptoms or central sensitization and resources tells us that there is a relationship between the level of sense of sensitization with those quantitative sensory tests and scores on a painter TechEd we can also give them a scale for kinesio phobia and this assesses their level of fear of movement or re-injury and there are classic Asians or cut points to consider higher or lower levels of fear in terms of recommended readings this is a nice chapter that actually pictures things in a slightly different way and I would thoroughly recommend reading this thank you for your attention