Positive response to galcanezumab following treatment failure to onabotulinumtoxinA in patients with migraine: post hoc analyses of three randomized double-blind studies

Background and purpose

Humanized monoclonal antibody galcanezumab, which binds to calcitonin‐gene‐related peptide, has shown efficacy for episodic and chronic migraine prevention. These analyses evaluated galcanezumab response for migraine headache prevention in patients who previously failed onabotulinumtoxinA (‘nonresponse’ or ‘inadequate response’ or safety reasons).

Methods

Post hoc analyses included data from three double‐blind, placebo‐controlled, phase 3 episodic or chronic migraine studies; 2886 patients randomly received 120 or 240 mg galcanezumab or placebo. During double‐blind periods the study drug was administered subcutaneously once a month for 6 months in EVOLVE‐1 and ‐2 and for 3 months in REGAIN. The 120 mg groups received a 240 mg loading dose at month 1. Pooled analyses included 129 patients who failed onabotulinumtoxinA. Using mixed effect model repeat measurements, the least squares mean change from baseline in the number of migraine headache days (MHDs) was calculated for the first 3 months of treatment.

Results

For pooled analyses, significant decreases from baseline in the number of MHDs were observed for 120 mg (−3.91) and 240 mg (−5.27) galcanezumab overall versus placebo (−0.88) across 3‐month time points for patients who failed onabotulinumtoxinA. Corresponding data for patients with chronic migraine showed significant decreases: 120 mg (−3.18) and 240 mg (−4.26) galcanezumab versus placebo (0.16). Significant reductions in the number of MHDs per month with acute medication use included 120 mg galcanezumab (−4.35) and 240 mg galcanezumab (−4.55) versus placebo (−0.83). Estimates of ≥50% response during months 1–3 were 9.4% for placebo, 41.3% for 120 mg galcanezumab and 47.5% for 240 mg galcanezumab.

Conclusion

Galcanezumab is an option for prevention of migraine in patients who have previously failed onabotulinumtoxinA preventive therapy.

Efficacy of galcanezumab in patients with episodic migraine and a history of preventive treatment failure: results from two global randomized clinical trials

BACKGROUND AND PURPOSE

The efficacy of galcanezumab, a monoclonal antibody for migraine prevention, has been demonstrated in two pivotal trials in patients with episodic migraine.

METHODS

EVOLVE-1 and EVOLVE-2 were identical phase 3, randomized, double-blind, placebo-controlled studies in patients with episodic migraine. Mean migraine headache days per month at baseline was 9. Patients were randomized 2:1:1 to monthly injections of placebo, galcanezumab 120 mg/240 mg during the 6-month double-blind treatment period. Key efficacy outcomes were assessed in subgroups amongst patients for whom, previously, for efficacy and/or safety/tolerability reasons (i) one or more (≥1) preventives failed, (ii) two or more (≥2) preventives failed and (iii) preventives were never used, or used but not failed (no prior failure).

RESULTS

In an integrated analysis of EVOLVE studies, galcanezumab 120 mg/240 mg versus placebo led to larger overall mean (SE) reductions in monthly migraine headache days across 6 months in patients with prior preventive failures (P < 0.001): ≥1 failure: 120 mg: -4.0 (0.4); 240 mg: -4.2 (0.5); placebo: -1.3 (0.4); ≥2 failures: 120 mg: -3.1 (0.7); 240 mg: -3.8 (0.8); placebo: -0.5 (0.6). Similar results were observed amongst patients with no prior failure, but the placebo response was larger: 120 mg: -4.7 (0.2); 240 mg: -4.5 (0.2); placebo: -3.0 (0.2) (P < 0.001 versus placebo). Significant improvements were observed with galcanezumab versus placebo for ≥50% and ≥75% reduction in monthly migraine headache days.

CONCLUSION

In patients with episodic migraine treated with galcanezumab, those with ≥1 or ≥2 prior preventive failures had significantly larger improvements, versus placebo, in efficacy outcomes. Similar results were observed in patients with no prior failure, with a larger placebo response.

OnabotulinumtoxinA for chronic migraine: efficacy, safety, and tolerability in patients who received all five treatment cycles in the PREEMPT clinical program

OBJECTIVE

Chronic migraine (CM) is a prevalent and disabling neurological disorder. Phase III REsearch Evaluating Migraine Prophylaxis Therapy (PREEMPT) clinical program assessed efficacy and safety of onabotulinumtoxinA (BOTOX(®)) for prophylaxis of headaches in adults with CM. This secondary analysis assessed patients who received all five treatment cycles and completed the study.

MATERIALS AND METHODS

PREEMPT (two phase III studies: 24-week double-blind, placebo-controlled [DBPC], parallel-group phase, followed by 32-week open-label [OL] phase) evaluated the efficacy and safety of onabotulinumtoxinA in CM (≥15 days/month with headache lasting ≥4 h a day). Patients were randomized (1:1) to onabotulinumtoxinA or placebo every 12 weeks for two cycles, followed by onabotulinumtoxinA for three cycles. Multiple headache symptom measures were evaluated. Results for the completer (five cycles) subgroup of patients are reported.

RESULTS

Of 1384 total PREEMPT patients, 1005 received all five treatment cycles (513 received onabotulinumtoxinA only [onabotulinumtoxinA/onabotulinumtoxinA (O/O)] and 492 received two cycles of placebo then three cycles of onabotulinumtoxinA [placebo/onabotulinumtoxinA (P/O)]). Demographics were similar between treatment groups. At Week 56, after all patients were treated with onabotulinumtoxinA, there continued to be significant between-group differences favoring the O/O vs P/O group for the following headache symptom measures: LS mean change from baseline in frequencies of headache days (-12.0 O/O, -11.1 P/O; P = 0.035), migraine days (-11.6 O/O, -10.7 P/O; P = 0.038), and moderate/severe headache days (-11.0 O/O, -10.1 P/O; P = 0.042). For other measures (cumulative hours of headache on headache days, frequency of headache episodes, and percentage with severe Headache Impact Test (HIT)-6 score, and total HIT-6 and Migraine-Specific Quality of Life Questionnaire scores), there were also large mean improvements from baseline. The percent of patients with a ≥50% reduction from baseline in frequency of headache days was significantly greater for the onabotulinumtoxinA-only group at Week 56 (69.6% O/O, 62.8% P/O; P = 0.023). The treatment-related adverse event rate was 28.5% for onabotulinumtoxinA vs 12.4% for placebo in the DBPC phase and 34.8% for patients treated with onabotulinumtoxinA for all five cycles throughout the 56-week trials.

CONCLUSIONS

This subgroup analysis demonstrated improvements with onabotulinumtoxinA treatment (five cycles) vs placebo (two cycles)/onabotulinumtoxinA (three cycles) for multiple headache symptom measures and suggests that at Week 56, patients treated earlier with onabotulinumtoxinA had better outcomes. These findings demonstrate the continued need and cumulative benefit over time with continued prophylaxis, an important and clinically pragmatic observation for clinicians and patients.

OnabotulinumtoxinA improves quality of life and reduces impact of chronic migraine

OBJECTIVE

To assess the effects of treatment with onabotulinumtoxinA (Botox, Allergan, Inc., Irvine, CA) on health-related quality of life (HRQoL) and headache impact in adults with chronic migraine (CM).

METHODS

The Phase III Research Evaluating Migraine Prophylaxis Therapy (PREEMPT) clinical program (PREEMPT 1 and 2) included a 24-week, double-blind phase (2 12-week cycles) followed by a 32-week, open-label phase (3 cycles). Thirty-one injections of 5U each (155 U of onabotulinumtoxinA or placebo) were administered to fixed sites. An additional 40 U could be administered "following the pain." Prespecified analysis of headache impact (Headache Impact Test [HIT]-6) and HRQoL (Migraine-Specific Quality of Life Questionnaire v2.1 [MSQ]) assessments were performed. Because the studies were similar in design and did not notably differ in outcome, pooled results are presented here.

RESULTS

A total of 1,384 subjects were included in the pooled analyses (onabotulinumtoxinA, n = 688; placebo, n = 696). Baseline mean total HIT-6 and MSQ v2.1 scores were comparable between groups; 93.1% were severely impacted based on HIT-6 scores ≥60. At 24 weeks, in comparison with placebo, onabotulinumtoxinA treatment significantly reduced HIT-6 scores and the proportion of patients with HIT-6 scores in the severe range at all timepoints including week 24 (p < 0.001). OnabotulinumtoxinA treatment significantly improved all domains of the MSQ v2.1 at 24 weeks (p < 0.001).

CONCLUSIONS

Treatment of CM with onabotulinumtoxinA is associated with significant and clinically meaningful reductions in headache impact and improvements in HRQoL.

CLASSIFICATION OF EVIDENCE

This study provides Class 1A evidence that onabotulinumtoxinA treatment reduces headache impact and improves HRQoL.

OnabotulinumtoxinA for treatment of chronic migraine: results from the double-blind, randomized, placebo-controlled phase of the PREEMPT 1 trial

OBJECTIVES

This is the first of a pair of studies designed to assess efficacy, safety and tolerability of onabotulinumtoxinA (BOTOX) as headache prophylaxis in adults with chronic migraine.

METHODS

The Phase III REsearch Evaluating Migraine Prophylaxis Therapy 1 (PREEMPT 1) is a phase 3 study, with a 24-week, double-blind, parallel-group, placebo-controlled phase followed by a 32-week, open-label phase. Subjects were randomized (1:1) to injections every 12 weeks of onabotulinumtoxinA (155 U-195 U; n = 341) or placebo (n = 338) (two cycles). The primary endpoint was mean change from baseline in headache episode frequency at week 24.

RESULTS

No significant between-group difference for onabotulinumtoxinA versus placebo was observed for the primary endpoint, headache episodes (-5.2 vs. -5.3; p = 0.344). Large within-group decreases from baseline were observed for all efficacy variables. Significant between-group differences for onabotulinumtoxinA were observed for the secondary endpoints, headache days (p = .006) and migraine days (p = 0.002). OnabotulinumtoxinA was safe and well tolerated, with few treatment-related adverse events. Few subjects discontinued due to adverse events.

CONCLUSIONS

There was no between-group difference for the primary endpoint, headache episodes. However, significant reductions from baseline were observed for onabotulinumtoxinA for headache and migraine days, cumulative hours of headache on headache days and frequency of moderate/severe headache days, which in turn reduced the burden of illness in adults with disabling chronic migraine.

OnabotulinumtoxinA for treatment of chronic migraine: results from the double-blind, randomized, placebo-controlled phase of the PREEMPT 2 trial

OBJECTIVES

This is the second of a pair of studies designed to evaluate the efficacy and safety of onabotulinumtoxinA (BOTOX) for prophylaxis of headaches in adults with chronic migraine.

METHODS

PREEMPT 2 was a phase 3 study, with a 24-week, double-blind, placebo-controlled phase, followed by a 32-week, open-label phase. Subjects were randomized (1:1) to injections of onabotulinumtoxinA (155U-195U; n = 347) or placebo (n = 358) every 12 weeks for two cycles. The primary efficacy endpoint was mean change in headache days per 28 days from baseline to weeks 21-24 post-treatment.

RESULTS

OnabotulinumtoxinA was statistically significantly superior to placebo for the primary endpoint, frequency of headache days per 28 days relative to baseline (-9.0 onabotulinumtoxinA/-6.7 placebo, p < .001). OnabotulinumtoxinA was significantly favoured in all secondary endpoint comparisons. OnabotulinumtoxinA was safe and well tolerated, with few treatment-related adverse events. Few patients (3.5% onabotulinumtoxinA/1.4% placebo) discontinued due to adverse events.

CONCLUSIONS

The results of PREEMPT 2 demonstrate that onabotulinumtoxinA is effective for prophylaxis of headache in adults with chronic migraine. Repeated onabotulinumtoxinA treatments were safe and well tolerated.

Topiramate modulates excitability of the occipital cortex when measured by transcranial magnetic stimulation

Summary

The aim of this study was to measure differences in occipital cortex excitability in migraineurs before and after administration of topiramate. We have previously demonstrated occipital cortex hyperexcitability in migraine using an objective technique of magnetic suppression of perceptual accuracy (MSPA). We hypothesized that a neuromodulator such as topiramate would demonstrate differences in MSPA in migraine compared with baseline. Ten migraine patients were recruited. To assess inhibitory function MSPA was measured using the following protocol. Timed transcranial magnetic stimulation were delivered at interstimulus intervals (ISI) varying from 40 to 190 ms (eight stimulations at each ISI) at 60% stimulus intensity. Subjects were asked to report letters projected at a fixed luminance on the screen. Visual suppression was calculated based on the number of errors the subjects made using automated analysis. This procedure was repeated at a minimum of two different dosages of topiramate when it was titrated for optimal migraine control. The interim dose was that at which an improvement in headache frequency was first observed, and the optimal dose was that at which the patient had a ≥ 50% reduction in headache frequency, or had reached a 100-mg dose. The mean [standard error (s.e.)] level of letters reported correct at baseline at 100-ms ISI was 91.6 (3.4) compared with 48.5 (6.0) ( P = 0.001) at an optimal dose of topiramate. Dose ranged from 50 to 100 mg; the average dose was 75 mg. The interim dose for most patients was 50 mg; the mean (s.e.) percentage of letters reported correct at interim was 75.9 (6.2) compared with baseline ( P = 0.01). Mean number of headaches at baseline was 27 per month, compared with eight headaches per month at interim dose and four headaches per month at optimal dose. There was no significant correlation between mean change in frequency of headache and mean change in inhibition from baseline to optimal dose (0.04, P = 0.89). Topiramate modulates occipital cortex excitability in chronic migraine possibly via mechanisms of cortical inhibition. Since there was not a strong correlation between the degree of inhibition and reduction of migraine frequency, it would appear that topiramate did have an independent effect on cortical excitability that was not dependent on reduction in migraine frequency.

Is Chronic Migraine One End of a Spectrum of Migraine or a Separate Entity?

Chronic migraine is associated with abnormalities in the periaqueductal grey that may be progressive. The condition is also associated with a greater degree of impairment in cortical processing of sensory stimuli than episodic migraine, perhaps due to more pervasive or persistent cortical hyperexcitability These findings fit with the model of migraine as a spectrum disorder, in which the clinical and pathophysiological features may progress over time. This progression may result from changes in nociceptive thresholds and ensuing central sensitization caused by recurrent migraine in susceptible individuals. This may lead to changes in baseline neurological function between headaches, evident not only in electrophysiological and functional imaging studies, but also as psychological and somatic complaints that occur after years of episodic migraine. From current research and migraine models, a conceptualization of chronic migraine is emerging in which relatively permanent and pervasive central changes have occurred that warrant novel and tolerable treatments.

A double-blind, randomized, placebo-controlled, single-dose study of the cyclooxygenase-2 inhibitor, GW406381, as a treatment for acute migraine

The objective of the present study was to explore the clinical efficacy and tolerability of GW406381, a cyclooxygenase-2 (COX-2) inhibitor with relatively high CNS penetration, in acute migraine. This was a double-blind, single-dose study of GW406381 compared with placebo and naproxen sodium compared with placebo (protocol number CXA20008). Three hundred and thirty-seven subjects were randomized 1:1:1 to GW406381 (70 mg), naproxen sodium (825 mg), or placebo for the treatment of one migraine headache of moderate or severe intensity in a potential 8-week period. The primary end-point was the proportion of subjects with headache relief [reduction in headache severity score from pre-dose 2 (moderate) or 3 (severe) to 0 (no pain) or 1 (mild)] at 2 h post-dose for GW406381 compared with placebo. Significantly higher proportions of subjects treated with GW406381 (50%, P = 0.032) or naproxen sodium (56%, P = 0.005) than with placebo (35%) reported headache relief at 2 h post-dose. Additional significant benefits were observed on many secondary outcomes, including proportions of subjects pain-free, for both GW406381 and naproxen sodium treatment compared with placebo. Both active treatments were well tolerated. Single-dose GW406381 (70 mg) and naproxen sodium (825 mg) were effective and well tolerated in the treatment of acute migraine.

The brain is hyperexcitable in migraine

Migraine is a very common disorder occurring in 20% of women and 6% of men. Central neuronal hyperexcitability is proposed to be the putative basis for the physiological disturbances in migraine. Since there are no consistent structural disturbances in migraine, physiological and psychophysical studies have provided insight into the underlying mechanisms. This is a review of the neurophysiological studies which have provided an insight to migraine pathogenesis supporting the theory of hyperexcitability.

History of childhood maltreatment is associated with comorbid depression in women with migraine

BACKGROUND

A bidirectional relationship between migraine and depression suggests a neurobiological link. Adverse experiences, particularly childhood maltreatment, may alter neurobiological systems, and predispose to a multiplicity of adult chronic disorders. Our objective is to determine, within a headache clinic population of women, if depression moderates the abuse-migraine relationship.

METHODS

At six headache specialty clinics, women with migraine were diagnosed using ICHD-II criteria, and frequency was recorded. A questionnaire regarding maltreatment history, headache characteristics, current depression, and somatic symptoms was completed.

RESULTS

A total of 949 women with migraine completed the survey: 40% had chronic headache (> or =15 headache days/month) and 72% had "very severe" headache-related disability. Major depression was recorded in 18%. Physical or sexual abuse was reported in 38%, and 12% reported both physical and sexual abuse in the past. Migraineurs with current major depression reported physical (p < 0.001) and sexual (p < 0.001) abuse in higher frequencies compared to those without depression. Women with major depression were more likely to report sexual abuse occurring before age 12 years (OR = 2.30, 95% CI: 1.14 to 4.77), and the relationship was stronger when abuse occurred both before and after age 12 years (OR = 5.08, 95% CI: 2.15 to 11.99). Women with major depression were also twice as likely to report multiple types of maltreatment (OR = 2.07, 95% CI: 1.27 to 3.35) compared to those without depression.

CONCLUSIONS

Childhood maltreatment was more common in women with migraine and concomitant major depression than in those with migraine alone. The association of childhood sexual abuse with migraine and depression is amplified if abuse also occurs at a later age.

High prevalence of somatic symptoms and depression in women with disabling chronic headache

OBJECTIVE

To better define, in women with headache, the relationship of depression and somatic symptoms to headache, characterized by diagnoses, frequency, and disability.

METHODS

At six headache specialty clinics, women with headache were classified using ICHD-II criteria, and frequency was recorded. A questionnaire addressing demographics, age at onset of headache, headache-related disability, somatic symptom, and depression severity was completed. Logistic regression was performed to measure the associations of headache frequency and headache-related disability with somatic symptom and depression severity.

RESULTS

A total of 1,032 women with headache completed the survey, 593 with episodic (96% with migraine) and 439 with chronic headache (87% with migraine). Low education and household income was more common in chronic headache sufferers and in persons with severe headache disability. Somatic symptom prevalence and severity was greater in persons with chronic headache and with severe headache-related disability. Significant correlation was observed between PHQ-9 and PHQ-15 scores (r = 0.62). Chronic headache, severe disability, and high somatic symptom severity were associated with major depressive disorder (OR = 25.1, 95% CI: 10.9 to 57.9), and this relationship was stronger in the subgroup with a diagnosis of migraine (OR = 31.8, 95% CI: 12.9 to 78.5).

CONCLUSIONS

High somatic symptom severity is prevalent in women with chronic and severely disabling headaches. Synergistic relationship to major depression exists for high somatic symptom severity, chronic headache, and disabling headache, suggesting a psychobiological underpinning of these associations.

The threshold for phosphenes is lower in migraine

We have reported a preliminary study confirming hyperexicitability of occipital cortex in migraine with aura (MwA) using transcranial magnetic stimulation (TMS). We have now completed a blinded study to investigate the occipital cortex in MwA and without aura (MwoA) compared with normal controls (NC) using TMS. TMS was performed using the Caldwell MES-10 stimulator. A circular coil 9.5 cm diameter was applied to the occipital scalp (7 cm above the inion). Stimulator intensity was increased in 10% increments until subjects reported visual phenomena or 100% intensity was reached. Stimulation intensity was then fine tuned to determine the threshold at which phosphenes were seen. Fisher's exact t-test and logrank test were used for statistical comparisons. Ten subjects with MwA and MwoA were compared to 10 NC. The difference in the proportion of subjects with phosphene generation was statistically significant (MwA 100%, MwoA 60% and NC 30%) [P = 0.003]. The difference in threshold levels for phosphenes was also significant for MwA 42.8%, and controls 57.3% [P = 0.0001]. There is a difference in threshold for excitability of occipital cortex in MwA and MwoA compared to NC. This is a direct neurophysiological correlate for clinical observations, which have inferred hyperexicitability of the occipital cortex in migraineurs.

Intranasal sumatriptan in cluster headache: randomized placebo-controlled double-blind study

BACKGROUND

Current evidence-based acute treatments of cluster headache are limited to oxygen inhalation and subcutaneous sumatriptan. Intranasal sumatriptan is a new formulation with better tolerability than the subcutaneous route. Two open-label studies suggested efficacy of intranasal sumatriptan in cluster headache.

METHODS

In a double-blind placebo-controlled randomized trial, patients with episodic or chronic cluster headache whose attacks lasted at least 45 minutes each treated one attack with 20 mg sumatriptan nasal spray and another one, at least 24 hours later, with matching placebo. They scored their headache on a five-point scale (very severe, severe, moderate, mild, or none) at 5, 10, 15, 20, and 30 minutes. The primary outcome measure was headache response (a decrease in pain from very severe, severe, or moderate to mild or none) at 30 minutes. Secondary outcome measures included pain-free rates, relief of associated symptoms, and rates of adverse events. Multilevel multivariate analysis was used for statistical analysis.

RESULTS

Five study centers enrolled 118 patients in whom 154 attacks were treated: 77 with sumatriptan and 77 with placebo. The responder rates at 30 minutes were 57% for sumatriptan and 26% for placebo (p = 0.002). Pain-free rates at 30 minutes were 47% for sumatriptan and 18% for placebo (p = 0.003). Sumatriptan was also superior to placebo considering initial response, meaningful relief, and relief of associated symptoms. There were no serious adverse events.

CONCLUSION

Sumatriptan nasal spray is effective and well tolerated in the acute treatment of cluster headache attacks of at least 45 minutes' duration.

Functional MRI-BOLD of brainstem structures during visually triggered migraine

BACKGROUND

Previously, hyperoxia and blood volume increase were reported in the red nucleus and substantia nigra during spontaneous migraine with aura.

OBJECTIVE

To further understand the pathophysiologic role of these centers, activation of brainstem structures was investigated in patients with visually triggered migraine.

METHODS

Twenty-six patients with migraine (23 with aura and 3 without aura), and 10 normal control subjects were studied with blood oxygen level-dependent (BOLD) fMRI during repeated checkerboard visual stimulation. Three axial image sections, which covered the occipital cortex and brainstem, were acquired 224 times with a temporal resolution of 3.5 seconds.

RESULTS

Repetitive visual stimulation triggered symptoms in 12 patients; four who had migraine with aura developed both visual symptoms and headaches, and six who had migraine with aura and two who had migraine without aura had headaches only. Four patients who had migraine with aura experienced the onset of their usual aura or onset of their typical headache either during the experiment or immediately after. In the remaining 10 patients with migraine, and all control subjects, visual stimulation failed to trigger symptoms at any time. In 75% of the patients who developed symptoms during stimulation, baseline T2*-weighted MR signal intensities increased in the red nucleus and substantia nigra before occipital cortex signal elevation or the onset of visually triggered symptoms.

CONCLUSION

Activation (hyperoxia and blood volume increase) of the red nucleus and substantia nigra in association with visually triggered symptoms of migraine suggest that these brainstem structures are a part of a neuronal network activated during an attack.

Periaqueductal gray matter dysfunction in migraine: cause or the burden of illness?

OBJECTIVE

The periaqueductal gray matter (PAG) is at the center of a powerful descending antinociceptive neuronal network. We studied iron homeostasis in the PAG as an indicator of function in patients with episodic migraine (EM) between attacks and patients with chronic daily headache (CDH) during headache. High-resolution magnetic resonance techniques were used to map the transverse relaxation rates R2, R2*, and R2' in the PAG, red nucleus (RN), and substantia nigra (SN). R2' is a measure of non-heme iron in tissues.

METHODS

Seventeen patients diagnosed with EM with and without aura, 17 patients diagnosed with CDH and medication overuse, and 17 normal adults (N) were imaged with a 3.0-tesla magnetic resonance imaging system. For each subject, mean values of the relaxation rates, R2 (1/T2), R2* (1/T2*), and R2' (R2* - R2) were obtained for the PAG, RN, and SN. R2, R2*, and R2' values of the EM, CDH, and N groups were compared using analysis of variance, Student t test, and correlation analysis.

RESULTS

In the PAG, there was a significant increase in mean R2' and R2* values in both the EM and CDH groups (P<.05) compared with the N group, but no significant difference in these values was demonstrated between the EM and CDH groups, or between those with migraine with or without aura in the EM group. Positive correlations were found for duration of illness with R2' in the EM and CDH groups. A decrease in mean R2' and R2* values also was observed in the RN and SN of the CDH group compared with the N and EM groups (P<.05), explained best by flow activation due to head pain.

CONCLUSIONS

Iron homeostasis in the PAG was selectively, persistently, and progressively impaired in the EM and CDH groups, possibly caused by repeated migraine attacks. These results support and emphasize the role of the PAG as a possible "generator" of migraine attacks, potentially by dysfunctional control of the trigeminovascular nociceptive system.

Pathophysiology of migraine headache

The underlying mechanism of migraine and pain has been unraveled recently with the advent of neuroimaging. In this article mechanism of migraine aura and the pain of migraine are discussed. In addition, interictal studies demonstrating hyperexcitability in migraine are reviewed.

Self-reported photophobic symptoms in migraineurs and controls are reliable and predict diagnostic category accurately

OBJECTIVES

To assess the reliability of self-reported photophobia across different patient populations and to examine how visual stress thresholds and photophobic symptoms may be predictive of diagnosis.

BACKGROUND

Relatively little is known about interictal photophobia in migraine. In particular, the variability of photophobia across different patient groups has not previously been studied, and a pathophysiological hypothesis to account for the symptoms is not agreed upon.

METHODS AND RESULTS

Study 1 compared 99 self-selected Dutch patients and 101 headache-free controls using survey methods. Patients both with and without aura were significantly more likely to report symptoms, such as the wearing of sunglasses in normal daylight, consistent with interictal photophobia. Study 2 replicated these findings in a series of consecutive referrals to a headache clinic in the United States. Study 3 used a specially designed laboratory test to examine the threshold for visual stress in those patients who had participated in study 2. Visual stress thresholds were significantly lower in patients than in controls. A discriminant function analysis of data from both studies 2 and 3 showed that diagnostic category (migraine; control) could be predicted from photophobic symptoms and visual stress thresholds at a level significantly better than chance.

CONCLUSIONS

We suggest that interictal photophobia is common in migraine and similar across different patient populations. One pathophysiological hypothesis is that interictal photophobia is associated with cortical hypersensitivity to stimulation. The predictive validity of interictal photophobic symptoms suggests that clinical diagnosis may be aided by questioning the patient about light sensitivity in the period between attacks.

Migraine: imaging the aura

We currently conceive of a migraine attack as originating in the brain. Triggers of an attack initiate a depolarizing neuroelectric and metabolic event likened to the spreading depression of Leao. This event activates the headache and associated features of the attack by mechanisms that remain to be determined, but appear to involve either peripheral trigeminovascular or brainstem pathways, or both. The excitability of cell membranes, perhaps partly genetically determined, is the brain's susceptibility to attacks. Factors that increase or decrease neuronal excitability constitute the threshold for triggering attacks. Using a model of visual stress-induced migraine or by studying spontaneous attacks and applying advanced imaging and neurophysiological methods, results have been obtained that support spreading neuronal inhibition as the basis of aura. This neuroelectric event is accompanied by hyperoxia of the brain, possibly associated with vasodilation. Evidence has also been obtained that the spreading cortical event can activate the subcortical centers possibly involved in nociception and associated symptoms of the migraine attack. Susceptibility to migraine attacks appears to be related to brain hyperexcitability. These newer techniques of functional neuroimaging have confirmed the primary neural basis of the migraine attack with secondary vascular changes, reconciling previous theories into a neurovascular mechanism.

The cortical silent period is shortened in migraine with aura

OBJECTIVES

Central neuronal hyperexcitability may be the physiological disturbance that predisposes subjects to migraine attacks. To test this hypothesis, we studied the cortical stimulation silent period (CSSP) elicited by transcranial magnetic stimulation (TMS), which is in part a measure of central inhibition of motor pathways in migraine with aura (MwA) patients and normal controls.

METHODS

In nine MwA patients (mean age 35.9 +/- 7) and 9 controls (mean age 37.6 +/- 7), we carried out transcranial stimulation using a 95 mm circular coil and Caldwell MES 10 stimulator to determine resting motor threshold (MT) for bilateral FDI muscles. All subjects performed isometric voluntary contraction of bilateral FDI maintained at 20% of maximal effort, during which we measured bilateral CSSP at (i) the stimulus intensity (SI) determined for the MT and (ii) an SI of 1.5 x MT.

RESULTS

Although the mean MT was higher in MwA compared with controls (63.1 +/- 14.4 vs 58.1 +/- 8.9), the difference was not significant. At an SI of 1.5 x MT the mean CSSP did not differ between the groups (MwA 141.7 +/- 31.9 vs controls 162.4 +/- 36.6). At the SI of the MT, however, the CSSP was shorter in MwA patients than in controls (62.9 +/- 27.3 vs 106.3 +/- 19.6, p = 0.001). There was an inverse correlation between the duration of CSSP and an increased frequency of headache (p = 0.02).

CONCLUSIONS

The shortened CSSP that we measured in MWA patients compared to normal with low intensity magnetic stimulation suggests reduced central inhibition resulting in increased excitability of cortical neurons in migraine subjects. The association of CSSP reduction with increased frequency of migraine is further suggestive that brain excitability is the basis of susceptibility to migraine attacks.

The occipital cortex is hyperexcitable in migraine: experimental evidence

OBJECTIVES

Threshold for generation of magnetophosphenes has been reported to be lower in migraine. We compared the threshold for eliciting phosphenes by transcranial magnetic stimulation and the ability to visually trigger headache in a select group of individuals with migraine with and without aura to normal controls.

METHODS

Transcranial magnetic stimulation was performed using the Cadwell MES-10 stimulator. A circular coil, 9.5 cm in diameter, was applied to the occipital scalp (7 cm above the inion). Stimulator intensity was increased in 10% increments until subjects reported visual phenomena or 100% intensity was reached. Stimulator intensity was then fine-tuned to determine the threshold at which phosphenes were seen. In the same subjects, visual stimulation was given in 3.0 T MRI and if a headache occurred the response was recorded.

RESULTS

Fifteen subjects with migraine were compared to 8 controls. A significant proportion of the migraineurs (86.7%) developed phosphenes compared to the controls (25%) (P = .006). The probability of triggering a headache was also higher in the migraineurs (53%); no headache was triggered in the controls (P = .019). A significant correlation was found between the threshold for phosphenes on transcranial magnetic stimulation and visually triggered headache (P = .002). When only migraine was considered, there was again a significant trend (P = .084).

CONCLUSIONS

There is a difference in threshold for excitability of occipital cortex in migraineurs and controls. The hyperexcitable visual cortex in migraine is predisposed to visually triggered headache.

Silent period abnormalities in carpal tunnel syndrome

Cutaneous silent period (CSP) was measured on stimulating digits 2 and 5 in 19 patients with carpal tunnel syndrome (CTS) and compared with 20 healthy volunteers. In 2 patients with severe CTS, CSP was absent on digit 2 but present on digit 5. In mild/moderate CTS digit 2 CSP mean duration was 50.9+/-13.9 ms, significantly longer than control subjects (36.9+/-8.7 ms) (P = 0.005). CSP was found to be abnormal in CTS, being absent in severe and prolonged in mild/moderate cases.

Brain excitability in migraine: evidence from transcranial magnetic stimulation studies

Central neuronal hyperexcitability is proposed to be the putative basis for the physiologic disturbances in migraine. Because there are no structural disturbances in migraine, only physiologic studies can provide insight into the underlying mechanisms. Recently, transcranial magnetic stimulation has been developed as a valuable research tool and can be used to study brain function noninvasively. This article is a review of the studies done in migraine using transcranial magnetic stimulation.

Transcranial magnetic stimulation confirms hyperexcitability of occipital cortex in migraine

OBJECTIVES

We hypothesized that the hyperexcitability of occipital cortex neurons may predispose migraine subjects to develop spreading depression, the putative basis of migraine with aura (MwA). To date there is no direct physiologic correlate confirming this in patients. Accordingly, we evaluated the differences in the threshold of occipital cortex excitation between MwA patients and normal controls (C) using transcranial magnetic stimulation (TMS).

METHODS

TMS was performed using the Cadwell MES 10 stimulator. A circular coil 9.5 cm in diameter was applied to the occipital scalp (7 cm above the inion). Stimulator intensity was increased in 10% increments until subjects reported visual phenomena or 100% intensity was reached. Stimulation intensity was then fine-tuned to determine the threshold at which phosphenes were just visualized.

RESULTS

Eleven MwA patients, mean age 37 +/- 7 years, were compared with 11 C, mean age 37.7 +/- 7 years. The difference in the proportion of subjects with phosphene generation between MwA patients and C was significant (MwA patients 100% versus C 27.3%, p = 0.001). The mean threshold level for MwA patients was 44.2 +/- 8.6 versus 68.7 +/- 3.1 for C (p = 0.0001). All threshold levels for MwA patients were lower than the lowest threshold for C; the MwA patient with the lowest threshold had an aura after stimulation.

CONCLUSIONS

The threshold for excitability of occipital cortex is lower in MwA patients compared with C. This is a direct neurophysiologic correlate for clinical observations that have indicated hyperexcitability of the occipital cortex in migraineurs.

Effects of aspirin on platelet aggregation in smokers and nonsmokers

OBJECTIVE

To assess the relative antiaggregatory ability of aspirin on platelets of smoking and nonsmoking healthy volunteers.

DESIGN

Prospective, randomized, crossover study.

SETTING

Tertiary-care teaching institution.

SUBJECTS

Eighteen healthy smoking and nonsmoking male volunteers.

INTERVENTIONS

Each subject received aspirin 325 mg or ticlopidine 250 mg bid as an active control for 7 days in a crossover manner separated by a 1-month washout period. Whole blood platelet aggregation was measured on four occasions, twice at baseline and once after each drug treatment.

OUTCOME MEASUREMENT

Whole blood ex vivo platelet aggregation in terms of impedance (omega) and adenosine triphosphate (ATP) release (nmol), as assessed using Lumi-aggregometry.

RESULTS

Aspirin was associated with significantly less ATP release in both smokers (p = 0.01) and nonsmokers (p = 0.003). No significant differences in platelet aggregation were found between smokers and nonsmokers at baseline or with any treatment phases. Sixty-seven percent and 17% of volunteers receiving ticlopidine and aspirin, respectively, reported adverse effects.

CONCLUSIONS

Twice-daily administration of aspirin for 7 days to healthy volunteers was well tolerated and also reduced platelet aggregation significantly regardless of smoking status.