The lower limb flexion reflex in humans.
The lower limb flexion reflex in humans.
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The lower limb flexion reflex in humans.
Prog Neurobiol. 2005 Dec;77(6):353-95
Authors: Sandrini G, Serrao M, Rossi P, Romaniello A, Cruccu G, Willer JC
The flexion or flexor reflex (FR) recorded in the lower limbs in humans (LLFR) is a widely investigated neurophysiological tool. It is a polysynaptic and multisegmental spinal response that produces a withdrawal of the stimulated limb and resembles (having several features in common) the hind-paw FR in animals. The FR, in both animals and humans, is mediated by a complex circuitry modulated at spinal and supraspinal level. At rest, the LLFR (usually obtained by stimulating the sural/tibial nerve and by recording from the biceps femoris/tibial anterior muscle) appears as a double burst composed of an early, inconstantly present component, called the RII reflex, and a late, larger and stable component, called the RIII reflex. Numerous studies have shown that the afferents mediating the RII reflex are conveyed by large-diameter, low-threshold, non-nociceptive A-beta fibers, and those mediating the RIII reflex by small-diameter, high-threshold nociceptive A-delta fibers. However, several afferents, including nociceptive and non-nociceptive fibers from skin and muscles, have been found to contribute to LLFR activation. Since the threshold of the RIII reflex has been shown to correspond to the pain threshold and the size of the reflex to be related to the level of pain perception, it has been suggested that the RIII reflex might constitute a useful tool to investigate pain processing at spinal and supraspinal level, pharmacological modulation and pathological pain conditions. As stated in EFNS guidelines, the RIII reflex is the most widely used of all the nociceptive reflexes, and appears to be the most reliable in the assessment of treatment efficacy. However, the RIII reflex use in the clinical evaluation of neuropathic pain is still limited. In addition to its nocifensive function, the LLFR seems to be linked to posture and locomotion. This may be explained by the fact that its neuronal circuitry, made up of a complex pool of interneurons, is interposed in motor control and, during movements, receives both peripheral afferents (flexion reflex afferents, FRAs) and descending commands, forming a multisensorial feedback mechanism and projecting the output to motoneurons. LLFR excitability, mediated by this complex circuitry, is finely modulated in a state- and phase-dependent manner, rather as we observe in the FR in animal models. Several studies have demonstrated that LLFR excitability may be influenced by numerous physiological conditions (menstrual cycle, stress, attention, sleep and so on) and pathological states (spinal lesions, spasticity, Wallenberg's syndrome, fibromyalgia, headaches and so on). Finally, the LLFR is modulated by several drugs and neurotransmitters. In summary, study of the LLFR in humans has proved to be an interesting functional window onto the spinal and supraspinal mechanisms of pain processing and onto the spinal neural control mechanisms operating during posture and locomotion.
PMID: 16386347 [PubMed - indexed for MEDLINE]
Prevalence of fibromyalgia syndrome in migraine patients.
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Prevalence of fibromyalgia syndrome in migraine patients.
Cephalalgia. 2006 Apr;26(4):451-6
Authors: Ifergane G, Buskila D, Simiseshvely N, Zeev K, Cohen H
Fibromyalgia syndrome (FMS) is a chronic pain syndrome of unknown aetiology characterized by diffuse pain over more than 3 months and tenderness in specific sites named tender points. The aim of this study was to assess the prevalence and severity of FMS among patients suffering from episodic migraine. Ninety-two consecutive patients (20 male, 72 female) fulfilling the International Headache Society criteria for migraine with and without aura from a tertiary headache clinic were evaluated. A headache and generalized pain history was recorded, tender points were evaluated by thumb palpation. The diagnosis of FMS was made based on the 1990 American College of Rheumatology classification criteria for FMS. Sixteen (22.2%) of the female patients and none of the male patients were diagnosed as suffering from FMS. Migraine severity and characteristics were similar to other female migraine patients. Patients suffering from migraine-FMS had lower quality of life scores and higher levels of mental distress. A high incidence of FMS was found among female migraine patients but not in males. The coexistence of FMS should be considered when choosing a prophylactic migraine therapy.
PMID: 16556247 [PubMed - in process]
Harmful impact of EU clinical trials directive: trial of alerting drug in fibromyalgia has had to be abandoned...
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Harmful impact of EU clinical trials directive: trial of alerting drug in fibromyalgia has had to be abandoned...
BMJ. 2006 Mar 18;332(7542):666
Authors: Hanning CD, Rentowl P
PMID: 16543347 [PubMed - indexed for MEDLINE]