Neuropathic Pain: Esthesia, Algesia, Pathia, and Dynia

00:01 In this talk, we'll review neuropathic pain.

00:03 We're going to talk about some common descriptions of neuropathic pain, how patients describe their symptoms, and then common conditions where neuropathic pain is a common feature.

00:15 Let's start with some descriptions of neuropathic pain.

00:18 What medical words do we use to describe patients' symptoms? Well, first is dysesthesia which just means any abnormal sensation.

00:27 This may be numbness, tingling, burning, electric shock type sensations.

00:31 Those are dysesthetic descriptions of pain.

00:35 Hypoesthesia means feeling something less.

00:40 Patients describe numbness to a tactile stimulus.

00:43 They don't feel it as much and we describe that as a hypoesthesia.

00:47 Hyperesthesia is feeling something more and we typically use the term hyperesthesia to describe a non-painful stimulus.

00:56 Patients may feel something more when brushed over the surface of the skin or when touching something, a non-painful stimulus invokes a higher than ordinary feeling. Hypoalgesia.

01:10 This means feeling a painful stimulus less, and we can see this description with a number of neuropathic pain syndromes.

01:18 Hyperalgesia means feeling a painful stimulus more.

01:23 There's reduced threshold and increased sensitivity of the nerves and patients will describe a painful stimulus that is more vigorous.

01:31 So a slightly warm water may feel quite painful or quite hot.

01:37 Hyperpathia has a similar description. Patients feel a painful stimulus worse and more.

01:44 There's a reduced threshold to firing of those pain neurons.

01:48 And then allodynia is a common word that we use to describe neuropathic pain.

01:53 And this is feeling a painful stimulus or a painful sensation to a non-painful stimulus.

01:59 So any of these words can be used to describe neuropathic pain and can be present in neuropathic pain syndromes.

02:06 So let's dive into each of these terms in a little greater detail.

02:10 First, allodynia. Here, we see nociceptors.

02:13 Those painful sensing nerves fire at a lower threshold.

02:17 The stimulus and response mode differ, so patients describe pain with a non-painful stimulus.

02:24 Hyperalgesia is a condition characterized by increased response of the nerves.

02:29 The stimulus and response mode are the same, so there's increased sensation to a tactile stimulus, but there's a more vigorous response. Hyperpathia.

02:39 We see the nociceptors fire with a raised threshold and increased response and here, the stimulus and response mode may be the same or differ.

02:48 And hypoalgesia where there's a raised threshold for firing.

02:53 The sensory nerves are deadened in some way, and they don't feel pain as well.

02:58 And here, typically, the stimulus and response modes are the same, so it's not feeling the sensation as much to a tactile stimulus.

03:08 When we think about pain descriptions, it's important to differentiate hyperalgesia from allodynia.

03:13 And there are a few signs, bedside tests, and concepts that we could take home to differentiate between these two.

03:20 Let's talk about the description of pain, the bedside test we use, the response in an affected area and unaffected area for each of these two types of neuropathic pain.

03:30 First, for hyperalgesia, the bedside test to look for this description would be the pin prick skin test with a safety pin.

03:38 Take a small safety pin and prick over the surface of the skin.

03:42 In patients that have a sensation of hyperalgesia, we'll hear descriptions of more intense pain and pain sensation than would be expected.

03:51 To an unaffected area that's not affected by that neuropathic pain, there may be a less painful sensation, and we're comparing the response that we get to that pinprick test.

04:01 For allodynia, pain may be induced just by stroking of the skin with a cotton tip applicator or just the hand.

04:09 And we see a painful response to a non-painful stimulus.

04:14 We'll see that painful response in an affected area, and we'll see a normal response in an unaffected area.

04:20 So understanding the descriptions between these two types of neuropathic pain is important as we evaluate patients.

04:26 When we think about pain in general, there's two types of pain, nociceptive pain and neuropathic pain.

04:35 Conditions can result in both nociceptive and neuropathic pains, but we hear different descriptions, we evaluate patients differently, and ultimately, different treatments for each of these.

04:46 So let's walk through some of the descriptions of nociceptive and neuropathic pain.

04:51 First, the patient's description of pain differs.

04:54 Nociceptive pain is described typically as an aching, it may be localized and non-radiating.

05:00 It may feel like that tooth ache pain that patients can describe.

05:06 In contrast, neuropathic pain is often a radiating, shooting, burning, electric shock-like pain that may start in one area and move to another area of the body.

05:17 In terms of movement impact, nociceptive pain is associated with movement.

05:22 Movement tends to make it worse and pain may be improved or resolved with rest.

05:27 In contrast, neuropathic pain is usually independent of movement.

05:30 In fact, many patients will describe worsening of their neuropathic pain at night when they're resting, when there's no external stimuli to distract the brain away from feeling that neuropathic pain, and neuropathic pain may be particularly problematic and bothersome for patients in the evening.

05:48 What about on physical examination? What are we looking for? Well, for neuropathic pain, we tend to see normal sensation with pain and pressure, and increased complaints with movement.

05:58 So moving a passive joint that is painful from nociceptive pain will cause it to hurt worse, but just touching the skin will not elicit a painful response.

06:08 In contrast with neuropathic pain, neurologic changes are often present.

06:12 Patients may have reduced sensation or lack of sensation, anesthesia over an area.

06:18 There may be allodynia where patients report significant pain just by touching or rubbing the surface of the skin or hyperpathia.

06:28 What are some examples of pain syndromes where we hear descriptions of nociceptive or neuropathic pain? Arthritic pain or early cancer pain may be described as nociceptive pain.

06:37 In contrast, shingles, radiculopathy, thalamic pain syndrome or postherpetic neuralgia may be conditions where we hear neuropathic pain.

06:47 In terms of effective treatments, opiates and NSAIDs have been historically used to treat nociceptive pain.

06:53 Increasingly, opioids are not used to treat long-term nociceptive pain and other complimentary or alternative interventions or even surgical interventions can be used for nociceptive pain.

07:05 In contrast, for neuropathic pain, we use neuropathic pain medications, tricyclic, antidepressants, SSRIs or SNRIs and anticonvulsants.