ClinicSpeak: what type of pain are you suffering from?
Are you in pain? #ClinicSpeak #MSBlog #MSResearch
“As most of you with more advanced MS know pain is a big problem and is very poorly managed outside of specialist clinics. Why? Because most neurologists and pain experts don’t understand the mechanisms that underpin MS pain syndromes. In addition to this pain affects mood; pain reduces your affect and is strongly correlated with depression. People who are depressed handle pain poorly and this leads to a downward spiral. This is why the management of pain in MS is so important and needs an holistic approach.”
“The study below tries to differentiate two major types of pain using neurophysiological testing. Nociceptive pain means there is a peripheral painful stimulus that is causing pain. For example, urinary tract infection stimulates pain receptors in the bladder and you feel pain. Neuropathic pain is due to central mechanisms and usually occurs in MS due to lesions affecting the pain pathways with aberrant transmission of signals to the brain that is perceived as pain. The investigator’s found that using laser evoked potentials (LEPs) they are able to work out the cause of the pain. When a laser light is targeted to the skin it causes a painful/hot stimulus that is activates pain or nociceptive receptors. The signal from this travels to the brain and is persceived as pain. We can measure the transmission of these electrical signals to brain; we call these evoked potentials or LEPs. Abnormal LEPs were associated with neuropathic, or central pain. This is important as this type of pain responds to different centrally acting drugs for example, sodium channel (carbamazepine or oxcarbazepine) or calcium channel (gabapentin, pregabalin) blockers and drugs that modulate pain perception (tricyclic or atypical anti-depressants; amitriptyline, duloxetine, etc.).”
“Do we need to do these tests to decide on what pain you have? No not really. We tend to make a call on the type of pain based on the history and examination and then decide on a management plan. If you are in a lot of pain you need to see your neurologist. We are pretty good at managing pain in pwMS. You don’t need to suffer in silence, which a lot of pwMS tend to do; they accept pain as another MS burden to live with. Why?”
Background: Pain is a common finding in patients affected by Multiple Sclerosis (MS). Many different types of pain can afflict MS patients, including neuropathic, nociceptive, or mixed pain. TSA-II-Thermotest (QST) and Laser evoked potentials (LEPs) are psychophysical and neurophysiological tests commonly used to explore pain.
Aims: The study aims to determine psychophysical and neurophysiological correlates in MS patients.
Methods: 16 MS patients (5 men, 11 women, mean age 59years, mean EDSS 7) where clinically and neurophysiologically tested. 5 patients presented neuropathic central pain (according to NeuPSIG 2011 guidelines), 8 patients presented nociceptive or mixed pain, and 3 patients were pain-free. For QST, the dorsum of both hands and feet were examined; for LEPs, the dominant hand and both feet were tested.
Results: Results were collected and compared to age and sex matched controls. Pin-prick was altered in 37.5%, LEPs were abnormal in 57.8% and QST was pathological in 85.9% of examined sites. We detected a significant correlation between pain and clinical examination (0.022), pain and altered QST (0.042), while LEP abnormalities correlated well with the presence of neuropathic pain (0.012).
Conclusions: Our results suggest that LEPs are more specific than QST to differentiate neuropathic from nociceptive pain.