Impaired Circadian Rhythmicity of Nociceptive Reflex Threshold in Cluster Headache

Abstract

Our findings suggest that in cluster headache there may be impairment of the pain control system that is associated with periodic failure of the mechanisms involved in the organization of biological rhythms.

Defensive reflexes in people with pain – a biomarker of the need to protect? A meta-analytical systematic review

“…Of the 11 studies that did report results, seven were consistent with the broader results of this review, two studies were opposing, and the remaining two were similar but with important albeit subtle differences (see Table 2 for details). The most prominent inconsistencies were those related to reflex thresholds: one study reported no difference in NFR thresholds between people with chronic low back pain or acute postoperative pain and pain-free controls (Peters et al, 1992), and the other reported no difference in NFR threshold between patients with chronic cluster headache and healthy controls (Nappi et al, 2002). The latter study (Nappi et al, 2002) had a medium risk of bias, which decreases our confidence in the results, but the former (Peters et al, 1992) had only a low risk of bias.…”

“…The most prominent inconsistencies were those related to reflex thresholds: one study reported no difference in NFR thresholds between people with chronic low back pain or acute postoperative pain and pain-free controls (Peters et al, 1992), and the other reported no difference in NFR threshold between patients with chronic cluster headache and healthy controls (Nappi et al, 2002). The latter study (Nappi et al, 2002) had a medium risk of bias, which decreases our confidence in the results, but the former (Peters et al, 1992) had only a low risk of bias. Other studies reporting findings inconsistent with the meta-analysis include AlAzzawi et al (2008), who reported delayed blink reflex latencies in people with rheumatoid arthritis than in healthy controls and Neziri et al (2010), who reported a higher reflex amplitude in people with chronic endometriosis than healthy controls.…”

“…There were 19 studies that met the inclusion criteria for the review but could not be included in the meta-analyses because raw data could not be extracted (Peters et al, 1992;Leroux et al, 1995;Knost et al, 1997;de Tommaso et al, 2000;Nappi et al, 2002;Desmeules et al, 2003;Katsarava et al, 2003;Banic et al, 2004;Lang et al, 2005;Ayzenberg et al, 2006;Carleton et al, 2006;Sandrini et al, 2006;Al-Azzawi et al, 2008;Filatova et al, 2008;Mendak et al, 2010;Neziri et al, 2010;Biurrun Manresa et al, 2013a,b;Desmeules et al, 2014). We were unable to obtain a meaningful outcome relevant to our research question for eight studies (see Table 2 for details).…”

“…For example, for five studies, the authors were unable to access their data (Peters et al, 1992;Knost et al, 1997;Nappi et al, 2002;Katsarava et al, 2003;Sandrini et al, 2006), two considered that it was inappropriate to use their data and declined to share their results (Carleton et al, 2006;Biurrun Manresa et al, 2013a,b), and the authors of nine studies did not respond to several enquiries about their data (Leroux et al, 1995;de Tommaso et al, 2000;Desmeules et al, 2003Desmeules et al, , 2014Banic et al, 2004;Lang et al, 2005;Ayzenberg et al, 2006;Al-Azzawi et al, 2008;Mendak et al, 2010). As noted in the peer review process of the current review, this does reflect a kind of bias -towards papers the authors of which are willing and able to share their data for the purposes of the meta-analysis.…”

What has functional neuroimaging done for primary headache … and for the clinical neurologist?

“…83,84 Impaired pain perception with decreased pain thresholds due to a dysfunction of pain control systems might also have a role in cluster headache. 85 Preliminary data from a functional imaging report of a patient suffering a spontaneous cluster headache attack provided some evidence for periaqueductal grey matter activation during attacks, 25 a brain area crucial for endogenous pain control. Moreover, a decreased metabolism in frontal brain circuits, which might be important in top-down modulation of pain processing, was recently demonstrated.…”