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Assessment of Responsiveness to Everyday Non-Noxious Stimuli in Pain-Free Migraineurs with vs Without Aura

• Migraineurs demonstrate sensory over-responsiveness to everyday sensations• Sensory over-responsiveness is more common in migraineurs with aura (MWA)• Attack frequency correlates with sensory over-responsiveness and pain summation

Assessment of Responsiveness to Everyday Non-Noxious Stimuli in Pain-Free Migraineurs with vs Without Aura

Orginally Published At: Pain Journal

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Opposing Roles of Estradiol and Testosterone on Stress-Induced Visceral Hypersensitivity in Rats

Women disproportionately suffer from chronic pain conditions including irritable bowel syndrome (IBS), fibromyalgia, migraine, and temporomandibular joint pain, many of which are comorbid with anxiety or depression disorders.7,9,11,29,37,110 During the past decades, efforts have been made to explore the mechanisms underlying sex differences in stress-induced anxiety and depression (for review, see Bangasser and Valentino8 and McEwen et al72). However, less is known about mechanisms underlying sex differences in stress-induced chronic pain conditions.

Opposing Roles of Estradiol and Testosterone on Stress-Induced Visceral Hypersensitivity in Rats

Orginally Published At: Pain Journal

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Migraine and Multiple Sclerosis: What Is the Link?

Increasing evidence suggests a relationship between migraine and multiple sclerosis that is beyond comorbidity and may help clarify the pathophysiology of both disorders.

Migraine and Multiple Sclerosis: What Is the Link?


Orginally Published At: Neuropathic Pain

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Vagus nerve stimulation inhibits trigeminal nociception in a rodent model of episodic migraine

imageIntroduction:
Although neck muscle tension is considered a risk factor for migraine, pungent odors can act as a trigger to initiate an attack in sensitized individuals. Although noninvasive vagus nerve stimulation (nVNS) is now an approved treatment for chronic migraine, how it functions to inhibit trigeminal nociception in an episodic migraine model is not known.
Objectives:
The objectives of this study were to determine if nVNS could inhibit trigeminal nociception in a novel model of episodic migraine and investigate changes in the expression of proteins implicated in peripheral and central sensitization.
Methods:
Sprague-Dawley male rats were injected with an inflammatory agent in the trapezius muscle before exposure to pungent volatile compounds, which was used to initiate trigeminal nociceptor activation. The vagus nerve was stimulated transdermally by a 1-ms pulse of 5 kHz sine waves, repeated at 25 Hz for 2 minutes. Nocifensive head withdrawal response to von Frey filaments was determined and immunoreactive protein levels in the spinal cord and trigeminal ganglion (TG) were investigated.
Results:
Exposure to the pungent odor significantly increased the number of nocifensive withdrawals in response to mechanical stimulation of sensitized TG neurons mediated by neck muscle inflammation. Noninvasive vagus nerve stimulation inhibited nociception and repressed elevated levels of P-ERK in TG, Iba1 in microglia, and GFAP in astrocytes from sensitized animals exposed to the pungent odor.
Conclusion:
Our findings demonstrate that nVNS inhibits mechanical nociception and represses expression of proteins associated with peripheral and central sensitization of trigeminal neurons in a novel rodent model of episodic migraine.

Vagus nerve stimulation inhibits trigeminal nociception in a rodent model of episodic migraine


Orginally Published At: PAIN Reports

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Evidence that dry eye is a comorbid pain condition in a U.S. veteran population

imageIntroduction:
Recent evidence suggests that dry eye (DE) may be comorbid with other chronic pain conditions.
Objectives:
To evaluate DE as a comorbid condition in the U.S. veteran population.
Methods:
Retrospective review of veterans seen in the Veterans Administration Healthcare System (Veteran Affairs) between January 1, 2010, and December 31, 2014. Dry eye and nonocular pain disorders were ascertained by International Classification of Diseases, Ninth Revision (ICD-9) codes. Dry eye was further separated into ICD-9 codes representing tear film dysfunction or ocular pain. χ2 and logistic regression analyses were used to examine frequency and risk of DE, ocular pain, and tear film dysfunction by pain disorders.
Results:
Of 3,265,894 veterans, 959,881 had a DE diagnosis (29.4%). Dry eye frequency increased with the number of pain conditions reported (P < 0.0005). Ocular pain was most strongly associated with headache (odds ratio [OR] 2.98; 95% confidence interval [CI] 2.95–3.01), tension headache (OR 2.64; 95% CI 2.58–2.71), migraine (OR 2.58; 95% CI 2.54–2.61), temporomandibular joint dysfunction (OR 2.39; 95% CI 2.34–2.44), pelvic pain (OR 2.30; 95% CI 2.24–2.37), central pain syndrome (OR 2.24; 95% CI 1.94–2.60), and fibromyalgia/muscle pain (OR 2.23; 95% CI 2.20–2.26), all P < 0.0005. Tear film dysfunction was most closely associated with osteoarthritis (OR 1.97; 95% CI 1.96–1.98) and postherpetic neuralgia (OR 1.95; 95% CI 1.90–2.00), both P < 0.0005.
Conclusions:
Dry eye, including both ocular pain and tear film dysfunction, is comorbid with pain conditions in this nationwide population, implying common mechanisms.

Evidence that dry eye is a comorbid pain condition in a U.S. veteran population


Orginally Published At: PAIN Reports