Managing migraine associated with sensitization

Hyperhomocysteinemia Increases Cortical Excitability and Aggravates Mechanical Hyperalgesia and Anxiety in a Nitroglycerine-Induced Migraine Model in Rats

Homocysteine is a sulfur-containing endogenous amino acid leading to neurotoxic effects at high concentrations. Population studies suggest an association between plasma homocysteine levels and the risk of migraine headaches. The aim of this study was to analyze the sensitivity of rats with prenatal hyperhomocysteinemia (hHCY) in respect of the development of behavioral correlates of headache and spreading cortical depolarization (CSD) in a migraine model induced by the administration of the nitric oxide (NO) donor nitroglycerin. Animals with hHCY were characterized by migraine-related symptoms such as mechanical hyperalgesia, high-level anxiety, photophobia, as well as an enhanced level of neuronal activity in the somatosensory cortex along with a lower threshold of CSD generation. Likewise, acute or chronic intermittent administration of nitroglycerin also induced the development of mechanical allodynia, photophobia and anxiety in control groups. However, these symptoms were more pronounced in rats with hHCY. Unlike hHCY, nitroglycerin administration did not affect the threshold of CSD generation, but like hHCY, increased the background neuronal activity in layers 2/3 and 4 of the cerebral cortex. The latter was more pronounced in animals with hHCY. Thus, the migraine profile associated with hHCY can be further exaggerated in conditions with enhanced levels of migraine triggering the gaseous transmitter NO. Our data are consistent with the view that high levels of plasma homocysteine can act as a risk factor for the development of migraine.

Sex differences in the expression of calcitonin gene-related peptide receptor components in the spinal trigeminal nucleus

BACKGROUND AND PURPOSE

Calcitonin gene-related peptide (CGRP) plays an important role in migraine pathophysiology. CGRP acts primarily by activating a receptor composed of 3 proteins: calcitonin receptor-like receptor (CLR), receptor activity-modifying protein 1 (RAMP1), and receptor component protein (RCP). We tested the hypothesis that sex differences exist in protein levels of two key components of this CGRP receptor: CLR and RCP.

METHODS

We used specific antibodies to assess baseline protein levels of CLR and RCP in the spinal trigeminal nucleus caudalis (SpVc) and upper cervical spinal cord of both male and female rats. We also tested if manipulations that knock-down the expression of RCP in SpVc, using locally-mediated gene transfer of short hairpin RNA (shRNA), ameliorate pain in an animal model of intracranial migraine-like pain induced by chemical noxious stimulation of the meninges. To assess pain, we used tests of ongoing pain (rat face grimace test and freezing behavior) and tests of facial mechanical hypersensitivity and allodynia.

RESULTS

There was no difference in CLR levels between male and female animals (p > 0.11) in SpVc and the upper cervical cord. However, female animals exhibited greater baseline levels of RCP (up to 3-fold higher) compared to males (p < 0.002). The knock-down of RCP expression in SpVc attenuated mechanical facial allodynia induced by chemical noxious stimulation of the meninges, but had little effect on ongoing pain behaviors in female and male animals.

CONCLUSIONS

RCP is an integral component of the CGRP receptor and may play a key role in mediating CGRP induced central sensitization after noxious stimulation of the meninges. RCP expression in the SpVc and upper cervical cord is sexually dimorphic, with higher levels of expression in females. This dimorphism may be related to the increased incidence of migraines in females-a hypothesis that should be tested in the future.

The role of calcitonin gene-related peptide in peripheral and central pain mechanisms including migraine

Calcitonin gene-related peptide (CGRP) is a 37-amino acid peptide found primarily in the C and Aδ sensory fibers arising from the dorsal root and trigeminal ganglia, as well as the central nervous system. Calcitonin gene-related peptide was found to play important roles in cardiovascular, digestive, and sensory functions. Although the vasodilatory properties of CGRP are well documented, its somatosensory function regarding modulation of neuronal sensitization and of enhanced pain has received considerable attention recently. Growing evidence indicates that CGRP plays a key role in the development of peripheral sensitization and the associated enhanced pain. Calcitonin gene-related peptide is implicated in the development of neurogenic inflammation and it is upregulated in conditions of inflammatory and neuropathic pain. It is most likely that CGRP facilitates nociceptive transmission and contributes to the development and maintenance of a sensitized, hyperresponsive state not only of the primary afferent sensory neurons but also of the second-order pain transmission neurons within the central nervous system, thus contributing to central sensitization as well. The maintenance of a sensitized neuronal condition is believed to be an important factor underlying migraine. Recent successful clinical studies have shown that blocking the function of CGRP can alleviate migraine. However, the mechanisms through which CGRP may contribute to migraine are still not fully understood. We reviewed the role of CGRP in primary afferents, the dorsal root ganglion, and in the trigeminal system as well as its role in peripheral and central sensitization and its potential contribution to pain processing and to migraine.

Predicting prognostic factors in a randomized controlled trial of acupuncture versus topiramate treatment in patients with chronic migraine

BACKGROUND

This study aimed to identify predictive factors of outcome in patients with chronic migraine (CM) treated with acupuncture or topiramate in a randomized controlled trial.

METHODS

Sixty-six consecutive CM patients were treated with either acupuncture (n=33) or topiramate (n=33) in a 12-week period. Data on potential predictive factors were collected at baseline, and secondary data analysis was performed to identify factors associated with treatment response. Treatment prognosis was defined as the change in mean number of moderate/severe headache days per 4 weeks from the 4-week baseline periods.

RESULTS

The median change in mean number of moderate/severe headache days per 4 weeks for patients with higher baseline headache days (>20 d) was significantly greater than that for lower baseline headache days (≤ 20 d) (median ± interquartile range: -12 ± 2 vs. -10 ± 1 d, P=0.01) in acupuncture group. There was a greater change in mean number of moderate/severe headache days per 4 weeks for high moderate/severe headache days (>20 d) than in low days (≤ 20 d) (-12 ± 1 vs. -10 ± 2 d, P=0.015) in acupuncture group. patients with throbbing symptoms had better prognosis with acupuncture than those without throbbing (-12 ± 2 vs. -9.5 ± 2.5 d, P=0.004). Higher score (>5 points) in the general expectations for improvement predicted better response in both treatment groups (>5 vs. ≤ 5 points: -12 ± 2 vs. -9 ± 2 d for acupuncture group; -10 ± 3 vs. -7 ± 4 d for topiramate group; P<0.001).

CONCLUSIONS

Some variables can predict outcome in acupuncture or topiramate treatment of CM patients. Identifying predictors of prognosis of both treatments for CM may help improve outcomes in future work.

Prevalence and characteristics of migraine in medical students and its impact on their daily activities

BACKGROUND

Migraine is a common neurological disorder with significant impact on quality of life. The aim of this study was to investigate the prevalence and characteristics of migraine headaches in medical students, to measure its impact on their life, and to assess their knowledge about the ailment. Information about lifestyle variables was also collected.

MATERIALS AND METHODS

All medical students who confirmed of having headache for more than 1 year formed the study group. Students filled a detailed questionnaire focusing on demographics, pain characteristics, accompanying factors, triggers, and family history of migraine. Lifestyle variables were enquired and migraine associated disability was assessed by MIDAS (Migraine Disability Assessment). The diagnosis of migraine was made according to the International Headache Society criteria. Results are expressed in n = numbers and percentage.

RESULTS

Sixty-eight percent of medical students had headache. The prevalence of migraine in the whole cohort was 28%; however, of the headache group, migraine constituted 42%. There was a female preponderance. One-fourth of the students had weekly or daily attacks with 31% students reporting increase in their headache intensity and frequency. Forty-four percent of students had severe headaches. Dizziness, allodynia, and neck stiffness were reported as accompanying symptoms. Trigger factors were identified in 99% students, predominant of which were poor sleep hygiene, environmental changes, head movements, and mental stress. Only 4% of students did regular exercise. Twenty-seven percent of students reported self-medication use of analgesics. One-fourth of the students had migraine-associated disability but only 6% realized that they had migraine.

CONCLUSION

Our study found a high prevalence of headache with migraine in medical students. The students' awareness of the disease was very low with one-fourth of the students resorting to self-medication. Our study identified previously less-recognized triggers like head movement and accompanying symptoms like neck stiffness. Migraine-attributed burden was high in medical students.

Cutaneous allodynia in patients with episodic migraine

Cutaneous allodynia may be observed in patients with migraine and this reflects the central sensitization of the trigeminal neurons. We aimed to investigate the frequency of cutaneous allodynia in patients with episodic migraine and to compare clinical characteristics of migraine patients with and without allodynia. One hundred and eighty-six consecutive patients with episodic migraine attacks were prospectively included in the study. The cutaneous allodynia symptoms that occurred during headache attacks were documented using a questionnaire for assessing cephalic and extracephalic cutaneous allodynia. One hundred and fourteen patients (61.3 %) were observed to develop allodynia during migraine attacks and the ratio of the female gender was found higher among the patients with allodynia (p < 0.001). Migraine disease duration was longer (p = 0.004) and accompanying nausea and phonophobia were more common (p = 0.003 and p = 0.005, respectively) in the patients with allodynia. Menstrually related migraine was found to be associated with both allodynia (p = 0.049) and its severity (p = 0.003). The results of present study revealed that cutaneous allodynia was rather frequent in episodic migraine, particularly in patients having longer disease duration. Higher frequency of allodynia in women and its association with menstrually related migraine may be related to the effects of hormonal factors on cutaneous pain thresholds and central sensitization. Association of nausea and phonophobia with allodynia may be interpreted as the common pathways are shared in the development of these symptoms.

The analysis of allodynia in patients with idiopathic intracranial hypertension

OBJECTIVES

Allodynia is frequently associated with migraine and other primary headaches. Our aim was to investigate the presence of allodynia and related features in idiopathic intracranial hypertension (IIH), which is a disabling secondary headache disorder.

METHODS

We included 46 IIH patients and analyzed their clinical and laboratory findings retrospectively. Allodynia was assessed using the validated 12-item allodynia symptom checklist (ASC-12), in addition to examining pressure (with von Frey filaments) and brush allodynia.

RESULTS

Allodynia was detected in 23 (50%) of IIH patients with ASC-12 and/or instrumental testing. The most commonly reported location was unilateral V1 distribution. The allodynic symptom profile was similar but milder when compared to 143 migraineurs with ASC-12. Only the aggravation of headache with physical activity emerged as a significant variable associated with allodynia in IIH. Among allodynic patients, only eight had previous migraine diagnosis. After onset of IIH, 20 patients reported migraine-like headache, while only three reported non-migrainous headache. In contrast, 13 of 23 non-allodynic IIH patients had non-migrainous headache features (p = 0.0045).

CONCLUSION

Half of the IIH patients reported allodynia, and these allodynic patients had mostly migraine-like headache profiles. Our study suggested that IIH may trigger some common mechanisms with migraine in pain pathways causing allodynia.

Trigeminal satellite cells modulate neuronal responses to triptans: relevance for migraine therapy

In the present paper, we have further developed an in vitro model to study neuronal–glial interaction at trigeminal level by characterizing the effects of conditioned medium (CM) collected from activated primary cultures of satellite glial cells (SGCs) on calcitonin gene-related peptide (CGRP) release from rat trigeminal neurons. Moreover, we investigated whether such release is inhibited by a clinically relevant anti-migraine drug, sumatriptan. CM effects were tested on trigeminal neuronal cultures in different conditions of activation and at different time points. Long-term exposures of trigeminal neurons to CM increased directly neuronal CGRP release, which was further enhanced by the exposure to capsaicin. In this framework, the anti-migraine drug sumatriptan was able to inhibit the evoked CGRP release from naïve trigeminal neuron cultures, as well as from trigeminal cultures pre-exposed for 30 min to CM. On the contrary, sumatriptan failed to inhibit evoked CGRP release from trigeminal neurons after prolonged (4 and 8 h) pre-exposures to CM. These findings were confirmed in co-culture experiments (neurons and SGCs), where activation of SGCs or a bradykinin priming were used. Our data demonstrate that SGCs activation could influence neuronal excitability, and that this event affects the neuronal responses to triptans.