Pain due to Ehlers-Danlos Syndrome Is Associated with Deficit of the Endogenous Pain Inhibitory Control.

OBJECTIVES: Although pain is a common complication of the hypermobile type of Ehlers-Danlos syndrome, its underlying mechanisms are still an issue of controversy. In this psychophysical study, we aimed at testing small-fiber function and the endogenous pain inhibitory control in patients with pain due to Ehlers-Danlos syndrome. METHODS: In 22 patients with pain due to Ehlers-Danlos syndrome and 22 healthy participants, matched for age and sex, we tested small-fiber function using quantitative sensory testing and the endogenous pain inhibitory control using the conditioned pain modulation (CPM) protocol. As quantitative sensory testing methods, we included thermal pain and mechanical pain thresholds and the wind-up ratio. The CPM protocol consisted of two heat painful stimuli, that is, a test stimulus and a conditioning stimulus. RESULTS: All patients complained of widespread pain. Quantitative sensory testing revealed no small-fiber deficit; in the area of maximum pain, we found an increased wind-up ratio. Whereas in the healthy participants the CPM protocol showed that the test stimulus rating was significantly reduced during conditioning, in patients with pain due to hEDS, the test stimulus rating increased during conditioning. CONCLUSIONS: Our psychophysical study showing that patients with pain due to hEDS have an increased wind-up ratio in the area of maximum pain and abnormal CPM protocol suggests that in this condition, pain is associated with central sensitization, possibly due to deficit of the endogenous pain inhibitory control. These data might be relevant to pharmacological treatment.

Syncope at SARS-CoV-2 onset.

We describe clinical and laboratory findings in 35 patients tested positive for SARS-CoV-2 by reverse transcriptase-polymerase chain reaction on nasopharyngeal swab experiencing one or multiple syncope at disease onset. Clinical neurologic and cardiologic examination, and electrocardiographic findings were normal. Chest computed tomography showed findings consistent with interstitial pneumonia. Arterial blood gas analysis showed low pO2, pCO2, and ratio of arterial oxygen partial pressure to fractional inspired oxygen (PaO2/FiO2) indicating hypocapnic hypoxemia. Patients who presented with syncope showed significantly lower heart rate as compared to 68 SARS-CoV-2 positive that did not. Such poorer than expected compensatory heart rate increase may have led to syncope based on individual susceptibility. We speculate that SARS-CoV-2 could have caused angiotensin-converting enzyme-2 (ACE2) receptor internalization in the nucleus of the solitary tract and other midbrain nuclei, impairing baroreflex and chemoreceptor response, and inhibiting the compensatory tachycardia during acute hypocapnic hypoxemia.