Abnormal visual processing in migraine with aura: a study of steady-state visual evoked potentials

BACKGROUND: Although a number of studies reported different interictal findings between migraine with aura (MA) and migraine without aura (MO), the pathophysiology of the visual aura in migraine remains unclear. OBJECTIVE: To investigate the visual processing in patients who experience MA between attacks using steady-state visual evoked potentials (SSVEPs). METHODS: SSVEPs to high (98%) and low (29%) contrast black and white checkerboard gratings with two spatial frequencies (0.5 and 2.0 cpd) at 5 and 10 Hz (10 and 20 reversal/s) were recorded binocularly from 10 patients with MA, 10 patients with MO between attacks and 20 healthy controls (HC). The SSVEPs were Fourier analyzed to obtain the amplitude and phase of the second (2F) and fourth (4F) harmonic response. RESULTS: In the amplitude of 2F, at 0.5 cpd, there was significant increased amplitude in both MA and MO in comparison to HC at 5 Hz in high and low contrast. However, no significant differences were detected at 2.0 cpd in both 5 and 10 Hz in high and low contrast. In the amplitude of 4F, at 2.0 cpd, there was significant increased amplitude in MA in comparison to MO and HC at 10 Hz in high contrast. However, there were no significant differences at 0.5 cpd at both 5 and 10 Hz in high and low contrast. There were no significant phase differences between MA, MO, and HC. CONCLUSION: The high amplitude of the SSVEPs suggests that interictally migraine patients have abnormal excitability in the primary visual cortex, and this change in excitability may exist, at least partially, in the visual association cortex in MA.     

Comparison of visual and auditory evoked cortical potentials in migraine patients between attacks.

OBJECTIVE: As both habituation of pattern reversal visual evoked potentials (PR-VEP) (Schoenen J, Wang W, Albert A, Delwaide PJ. Potentiation instead of habituation characterizes visual evoked potentials in migraine patients between attacks. Eur J Neurol 1995;2:115-122) and intensity dependence of auditory evoked cortical potentials (IDAP) (Wang W, Timsit-Berthier M, Schoenen J. Intensity dependence of auditory evoked potentials in migraine: an indication of cortical potentiation and low serotonergic neurotransmission? Neurology 1996;46:1404-1409) were found abnormal in migraine between attacks, we have searched for intraindividual correlations between both tests in 59 migraine patients (22 with aura [MA], 37 without aura [MO]) and in 23 healthy volunteers (HV). METHODS: Amplitude change of the PR-VEP N1-P1 was measured between the 1st and 5th block of 50 sequential averagings during continuous stimulation at 3.1 Hz. IDAP was computed from N1-P2 amplitudes of 100 averagings during stimulations at 40, 50, 60 and 70 dB SL. Amplitude-stimulus intensity function (ASF) slopes and amplitude changes between 40 and 70 dB were calculated. MO and MA differed from HV in PR-VEP amplitude change (P=0.007) and IDAP slope (P = 0.0004). RESULTS: There was no significant correlation between VEP amplitude changes and IDAP slopes, nor between the latter two and attack frequency or disease duration. A negative correlation was found between the amplitude of the first block of averaged responses and potentiation of VEP in all subject groups (P = 0.03) as well as between the amplitude of the auditory evoked potential, at 40 dB, and the percentage of amplitude increase between 40 and 70 dB in MO (P = 0.004) and MA (P = 0.007). ASF slopes and 40 dB amplitudes were significantly correlated only in the MA group (P = 0.002). These results confirm the interictal deficit of habituation in cortical processing of repetitive visual and auditory information in migraine. Since there is no intraindividual correlation between the cortical responses to these sensory modalities they are complementary tools for the study of migraine and may help to identify subgroups of patients with distinct pathophysiological mechanisms. CONCLUSIONS: The strong negative correlation between the initial amplitude of evoked potentials and their amplitude increase during subsequent averaging confirms that the response potentiation in migraine is likely to be due to a reduced preactivation level of sensory cortices.     

Auditory cognitive event-related potentials in migraine with and without aura in children and adolescents

BACKGROUND AND PURPOSE: Cognitive Event-Related Potentials (CERP) reflect sensory information processing: cognitive function and early memory. Studies of CERP in adult migraneurs yielded contradictory results. The aim of our study was to evaluate CERP in children and adolescents with migraine with and without aura during the interictal period. MATERIAL AND METHODS: The study was carried out on 111 children aged 7-18 years (mean 12.92 (2.78) with idiopathic attack headaches. In this group migraine with aura (MA) was diagnosed in 27 patients, migraine without aura (MO) in 36 children and episodic tension-type (TH) headaches in 48 patients. RESULTS: The latencies N2 and P3 were significantly longer (p < 0.05 and p < 0.01, respectively) in the group of all migraneurs (MA + MO, n = 63) as compared with the TH group. In the MO group not only N2 and P3 latency, but also P2 latency (p < 0.05) were longer, if particular types of migraine were compared with tension-type headaches. There were no statistically significant differences between mean latencies in MA and TH groups. Analyzing CERP amplitudes, the N1/P2 amplitude was significantly higher in MO patients than in the TH group only. We found longer P2, N2 and P3 latencies and higher N1/P2 amplitude in MO patients in comparison with MA patients. We found correlation between P3 latency and the age of patients with migraine. There were no statistically significant correlations for either headache type between CERP parameters and illness duration, sex of patients and unilateral localisation of headache. CONCLUSIONS: The CERP parameter changes in children with migraine point out the disturbances of cognitive functions also for auditory modalities. It suggests generalized dysfunction of cortical information processing in the interictal period of migraine.     

Visual evoked potential changes in migraine. Influence of migraine attack and aura

OBJECTIVE: To assess the visual evoked potential (VEP) changes in migraines with and without aura. STUDY DESIGN: A clinical study in which the VEP results of 45 migraineurs (study group) and 22 healthy volunteers (control group) were compared. Of 45 migraineurs, 29 had migraine with aura (MA) and 16 had migraine without aura (MOA), and they were examined both during and between the migraine attacks. METHODS: The patients and healthy controls underwent VEP assessment. On VEP recording, mono-ocular stimulation was performed by means of the pattern reversal check board. The latencies of N1, P1 and N2, and the N1--P1 amplitude were noted. The following comparisons were made between NI, P1 and N2 latencies and N1--P1 amplitudes of the migraine and control groups; during and between attack the VEP results of the patients with MA and MOA. RESULTS: The VEP results of the migraineurs and healthy controls were similar (P>0.05). The during attack results of MA, during and between attack results of MOA, and the results of the control group were also similar (P>0.05). N2 latency significantly elongated in patients with MA in the attack free period than it was during the attack (P=0.01), and was also longer than it was in the control group (P=0.01). CONCLUSIONS: There is involvement of the visual pathway in MA rather than MOA, and differentiation between these subtypes of the migraine disease may be performed on the basis of VEP findings manifesting by the prolongation of the N2 wave latency. This contention should be confirmed by further studies.     

Visual evoked potential latency, amplitude and habituation in migraine: a longitudinal study.

OBJECTIVE: It has not been previously studied with a paired longitudinal design if visual excitability changes occur in the preattack period across the migraine cycle, or how excitability and habituation relate to migraine-attack severity, clinical photophobia and serotonin metabolism. METHODS: Monocular 62' check reversals were applied in 33 adult migraine patients without aura (MwoA), 8 with aura (MA) and 31 controls. VEP was recorded in four blocks of 50 stimuli. P1 (P100) and N2 (N145) latency and N1P1 and P1N2 amplitude were measured. Serotonin was measured in plasma and platelets sampled before each session. Sessions were classified as preattack, attack, postattack or interictal. RESULTS: Migraine patients had significantly higher P1N2 amplitude before the attack compared to a paired interictal recording (n=13, p=0.03), but habituation difference was not found. MA patients had significantly higher P1N2 and N1P1 amplitude than controls and MwoA. P1 latency correlated positively with headache history duration. During attack, a positive correlation between P1N2 amplitude habituation and serotonin emerged in MA patients. CONCLUSIONS: Increased VEP P1N2 amplitude was observed within a few days before the attack. Visual cortex excitability seems to be generally increased in MA as compared to MwoA patients and controls. SIGNIFICANCE: Increased excitability of the visual cortex seems to be detectable in the preattack state, supporting the concept of a cyclic CNS dysfunction in migraine.     

应用M-模经颅多普勒超声技术评价头痛与卵圆孔未闭的关系

目的观察头痛、有先兆偏头痛(MA)、无先兆偏头痛(MO)患者卵圆孔未闭(PFO)的发生率,以及较大分流的发生率。方法头痛患者268例,其中MA组59例,MO组158例,其他类型头痛组51例,健康对照组75例。以肘前静脉注射激活的生理盐水作为造影剂,并结合Valsava动作,行M-模经颅多普勒超声(mpTCD)监测,诊断PFO并对分流量进行分级。安静状态时出现阳性结果则判断为永久型分流,Valsava动作后出现阳性结果则判断为功能型分流。注射生理盐水后20 s内微栓子信号超过30个判断为大量分流。结果全部头痛患者中PFO的发生率为44%,其中永久型分流53例,功能型分流43例。MA组存在分流的患者数显著多于对照组(P<0.001),也多于其他头痛组(P<0.01)。MO组存在分流的患者数高于对照组及其他头痛组,但未获得统计学差别(分别为P=0.054和P=0.3)。较大分流量在MA组、MO组、其他头痛组和对照组的发生率分别为37%、15%、8%、4%,MA组、MO组均显著高于对照组(分别为P<0.01和P<0.05)。结论有先兆偏头痛组患者存在较多PFO,而且偏头痛组较大分流量的患者较多。     

Chlordimeform produces contrast-dependent changes in visual evoked potentials of hooded rats

Previous experiments found that acute exposure to the insecticide/acaricide, chlordimeform (CDM), produced large increases in the amplitude of pattern reversal evoked potentials (PREPs) without changing the amplitude of flash evoked potentials (FEPs) in the same rats (W. K. Boyes and R. S. Dyer, Exp. Neurol. 86: 434-447, 1984). Current work investigated the influence of physical characteristics of the evoking stimuli on the action of CDM. Adult male Long-Evans rats with epidural visual cortex electrodes were used. In experiment 1, PREPs were elicited with alternating gratings having equal contrast (99%) and a square wave spatial luminance profile at several spatial frequencies. Rats treated 1 h previously with 40 mg/kg CDM had increased PREP amplitudes at 0.1, 0.2, and 0.4 cycles per degree (cpd), but not at 0.8 cpd. No changes were found after 5 mg/kg CDM. In experiment 2, PREPs were elicited with gratings oriented at 0 degrees (horizontal), 45 degrees, 90 degrees, or 135 degrees. Treatment with 40 mg/kg CDM increased PREP amplitudes and latencies regardless of orientation. In experiment 3, FEPs elicited with strobe flashes spanning four log units of intensity showed a small but significant CDM dose X intensity interaction on P2N2 peak-to-peak amplitude. In experiment 4, PREPs were elicited with alternating gratings having a sinusoidal spatial luminance profile, spatial frequency of 0.2 or 0.8 cpd, and contrast ranging from noise levels to 65%. Rats treated with 40 mg/kg CDM showed increased peak-to-peak amplitudes only at 0.2 cpd and only at contrast values above 10%. The failure of CDM to alter PREPs at 0.8 cpd was attributed to low contrast sensitivity at that spatial frequency. The results demonstrated that the action of CDM on visual evoked potentials was dependent on the amount of contrast in the stimulus pattern, and suggested that CDM alters the encoding of visual contrast.     

Median nerve somatosensory evoked potentials in migraine

In visual evoked potential studies, habituation during stimulus repetition with the same stimulus at a constant intensity has been found to be abnormal in migraineurs between attacks. The purpose of this study was to investigate habituation of somatosensory evoked potentials (SEPs) and the effects of migraine on them. Eighty-five subjects were included in the study: 30 healthy volunteers (HVs) and 55 migraineurs [30 with migraine without aura (MO), 25 with migraine with aura (MA)]. During continuous stimulation at 3 Hz, four blocks of 100 responses were sequentially averaged of Erb's point (N9), cervical (N13), and cortical (N20) median nerve SEPs. Mean amplitude changes in the second, third and fourth blocks are expressed as percentages of the first block. There was habituation to N13 and N20 in the second, third and fourth blocks in HVs. In the migraine groups, there was no habituation; on the contrary, potentiation was found. This potentiation was statistically significant only in the second blocks for N13 (MO P=0.007, MA P=0.01 versus HVs). However, in both migraineur groups, the rate of N20 potentiations was statistically significant versus that in HVs for all blocks (all P < 0.05). It is concluded that whilst physiological habituation occurs in HVs for cervical and cortical SEPs, in migraine patients there is an interictal deficit of habituation of this sensory modality.     

Potentiation instead of habituation characterizes visual evoked potentials in migraine patients between attacks

We have studied habituation of the pattern-reversal visual evoked potential (VEP) in healthy volunteers (n = 16) and in patients suffering from migraine without (n = 27) or with aura (n = 9). Five blocks of 50 responses at a stimulation rate of 3.1 Hz were sequentially averaged and analyzed separately for latencies, peak-to-peak amplitudes of N1-P1 and P1-N2, and the area under the N2 component Latencies of N1, P1, or N2 components were not significantly different between the sequential trial blocks, or between groups. Mean amplitudes of N1-P1 and P1-N2 in the first and subsequent blocks of SO responses were not statistically different among groups. In healthy subjects, there was a decrement of N1-P1 and P1-N2 amplitudes and N2 area on successive averagings. This habituation was maximal in the third and fourth blocks, but tended to disappear in the fifth block. In marked contrast to healthy subjects, migraine patients were characterized by a transient amplitude increment (i.e. potentiation) of VEP components which reached its maximum in the second to fourth blocks. Amplitude changes in sequential blocks were not dependent on attention and differed significantly between healthy subjects and migraineurs, but not between migraine with and without aura. Taken together with previous studies showing deficient habituation of contingent negative variation in migraine, these results indicate a dysfunction of central information processing which might have behavioral and pathogenic correlates.     

Investigation of an LDLR gene polymorphism (19p13.2) in susceptibility to migraine without aura

We performed a genetic association study with the LDL receptor gene (LDLR) on chromosome 19p13.2 in 360 migraine patients, 220 with migraine without aura (MO) and 140 with migraine with aura (MA), and 200 controls, by analysing two polymorphic markers, a G142A transition in exon 10 and a triallelic (TA)n repeat in exon 18. The allelic distribution of the (TA)n polymorphism was significantly different between migraine without aura (MO) and both controls and migraine with aura (MA). We suggest a possible predisposition to MO in the studied population through this polymorphism or another polymorphism in linkage disequilibrium with (TA)n.     

应用对比经颅多普勒技术评价偏头痛和卵圆孔未闭的关系

目的：观察门诊有先兆偏头痛（MA），无先兆偏头痛（M0）患者和无头痛人群中卵圆孔未闭（PFO）的发生率，以及产生中或大分流PFO的发生率。方法：经受试者同意后，随机抽取我院神经内科门诊从2006年3月至2007年3月就诊的MA患者38例（男14例，女24例），MO患者44例（男15例，女29例），无头痛对照24例（男10例，女14例）。以肘前静脉注射手振生理盐水作为造影剂，并结合Valsaval动作，行经颅多普勒（TCD）监测，诊断PFO并对分流量进行分级。结果：MA组与对照组比，具有PFO者占42％，高于对照组的20％；其中中分流或大分流者高于对照组，差异有统计学意义。MO组具有PFO者也高于对照组，但差异无统计学意义。结论：MA患者比无头痛人群存在较多的PFO，其巾出现中分流或大分流的显著增多。     

Visual evoked potential abnormalities in dyslexic children.

Developmental reading disability (dyslexia) has traditionally been attributed to impaired linguistic skills. Recent psychophysical data suggest that dyslexia may be related to a visual perceptual deficit. A few visual evoked potential (VEP) studies have addressed this hypothesis, but their results are far from consistent. We submitted 9 dyslexic subjects and 9 age- and sex-matched normal controls to checkerboard pattern reversal VEPs. The main experimental variables were: large (0.5 cycles per degree; cpd) and small (2 cpd) checks and two reversal frequencies (2.1 Hz and 8 Hz); mean luminance and contrast (60 cd/m2 and 50%, respectively) were kept constant in all four conditions. Transient VEP (2.1 Hz) parameters did not differ between controls and dyslexics at 2 cpd. At 0.5 cpd, N70 amplitude was significantly smaller and N70 latency significantly shorter in dyslexics. Amplitudes for the fundamental frequency (8 Hz), as well as for the second and third harmonics of the steady-state VEPs were smaller in dyslexics for both stimulus sizes. A discriminant analysis correctly classified each subject. Our data confirm the hypothesis of a perceptual deficit in dyslexic subjects. The abnormalities are related to spatial and temporal stimulus frequencies: they appear when large stimuli are presented, or when the stimulation frequency is high. These data support the hypothesis of selective magnocellular dysfunction in dyslexia.     

Investigation of the low-density lipoprotein receptor gene and cholesterol as a risk factor for migraine

The Low-Density Lipoprotein Receptor (LDLR) gene is a cell surface receptor that plays an important role in cholesterol homeostasis. We investigated the (TA)n polymorphism in exon 18 of the LDLR gene on chromosome 19p13.2 performing an association analysis in 244 typical migraine-affected patients, 151 suffering from migraine with aura (MA), 96 with migraine without aura (MO) and 244 unaffected controls. The populations consisted of Caucasians only, and controls were age- and sex-matched. The results showed no significant difference between groups for allele frequency distributions of the (TA)n polymorphism even after separation of the migraine-affected individuals into subgroups of MA and MO affected patients. This is in contradiction to Mochi et al. who found a positive association of this variant with MO. Our study discusses possible differences between the two studies and extends this research by investigating circulating cholesterol levels in a migraine-affected population.     

Validation of the deCODE Migraine Questionnaire (DMQ3) for use in genetic studies

We assessed the reliability of the diagnosis of migraine with aura (MA) and migraine without aura (MO) based on the third edition of the deCODE Migraine Questionnaire (DMQ3) using a physician-conducted interview as an empirical index of validity. Amongst Danish migraine families recruited from specialist practice we selected 200 cases diagnosed according to the International Classification of Headache Disorders 2nd Edition in a validated physician-conducted telephone interview: 50 patients with exclusively MA, 50 with both MA and MO, 50 with exclusively MO and 50 controls. A written copy of the DMQ3 was mailed to the participant. The DMQ3-based diagnosis was compared with the interview-based diagnosis. Overall, the DMQ3 diagnosed migraine (MA, MO or both) with a sensitivity of 99% (109/110), a specificity of 86% (32/37) and a kappa statistic of 0.89. The most reliable subtype of migraine was MA (with or without co-occurring attacks of MO) which was diagnosed with a sensitivity of 92% (71/77), a specificity of 93% (65/70) and a kappa statistic of 0.85. Exclusively MO was diagnosed with a sensitivity of 91% (30/33), a specificity of 93% (106/114) and a kappa statistic of 0.80. Weakest was the diagnosis of both MO and MA which was diagnosed with a sensitivity of 63% (24/38), a specificity of 92% (100/109) and a kappa statistic of 0.57. In conclusion, the DMQ3 is a valid tool for diagnosing patients with migraine for genetic studies.     

Migraine with aura and brain magnetic resonance imaging abnormalities in patients with CADASIL

BACKGROUND: Migraine with aura (MA) is one of the clinical hallmarks of CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy), a small vessel disease of the brain caused by mutations in the NOTCH3 gene, but its exact mechanisms are unknown. OBJECTIVES: To describe the patterns of MA in CADASIL and to compare brain magnetic resonance signal abnormalities between CADASIL patients with and without MA. DESIGN: Comparison of brain magnetic resonance signal abnormalities between cases and controls. SETTING: Patients with CADASIL seen at Lariboisière Hospital. PATIENTS: Forty-one CADASIL patients with MA and 31 age-matched CADASIL controls without MA. RESULTS: The mean age at onset of MA was significantly younger in women compared with men and occurred a mean of 15 years prior to stroke onset. A majority of patients (56%) reported at least 1 migraine attack with atypical aura. All CADASIL patients either with or without MA had white matter signal abnormalities on T2-weighted imaging. There was no difference in the frequency and distribution of brain signal abnormalities between CADASIL patients with and without MA. CONCLUSIONS: In CADASIL, MA is characterized by an unusually high frequency of attacks of migraine with atypical aura. The distribution and extent of magnetic resonance signal abnormalities did not differ according to migraine phenotype.     

The prevalence of patent foramen ovale in patients with migraine

BACKGROUND AND PURPOSE: Migraine is a common neurologic disorder whose etiology remains unknown. Migraine has been reported as a possible risk factor for ischemic stroke, especially in young women. The relationship between migraine and stroke is stronger in patients suffering from migraine with aura compared to those with common migraine. Coexistence of migraine and patent foramen ovale (PFO) should be also considered. The aim of our study was to evaluate the frequency of PFO in patients with migraine with aura (MA) and compare it with the prevalence of PFO in migraine patients without aura (M) and in a healthy age-matched control group. MATERIAL AND METHODS: We assessed 62 patients (48 females) suffering from migraine with aura, 60 without aura (53 females) and 65 normal controls (51 females). In order to detect PFO the contrast transcranial Doppler was performed during Valsalva maneuver. RESULTS: The presence of PFO was found in 33/62 (53%) patients with MA compared to 15/60 (25%) without aura, and in 16/65 (25%) control subjects. The difference in PFO prevalence between MA patients and M patients and the difference between MA patients and the control group was statistically significant (p<0.05). CONCLUSIONS: Our findings suggest that at least some attacks of migraine with aura may be associated with paradoxical embolism.     

Increased risk of migraine with typical aura in probands with familial hemiplegic migraine and their relatives

We investigated the occurrence of migraine without aura (MO) and migraine with typical aura (MA) amongst probands with familial hemiplegic migraine (FHM) and their first degree relatives in order to evaluate the relations between these syndromes. A total of 44 FHM probands and 240 first degree relatives were identified in the Danish population. The pattern of familial aggregation was assessed by population relative risk (PRR) calculations. Amongst FHM probands the PRR of MO was 1.5 (95% CI: 0.8-2.2), whereas the PRR of MA was 7.1 (95% CI: 5.0-9.2). Thus, compared with the general population, FHM probands had no increased risk of MO but a significantly increased risk of MA. A similar pattern was seen amongst their first degree relatives, who had no increased risk of MO, whereas the risk of MA was significantly increased; 7.6 times in FHM-affected first degree relatives and 2.4-times in non-FHM-affected first degree relatives. These results are contrary to a sharing of genetic mechanisms between FHM and MO. Furthermore, they suggest that the genetic abnormality causing FHM may also cause attacks with the symptomatology of MA.     

Association of MTHFR gene polymorphisms with migraine in North Indian population

Polymorphisms in MTHFR gene are mostly associated with increased levels of homocysteine in the absence of dietary folate and are a risk factor for complex neurovascular diseases like migraine. The aim of present case-control study was to determine the association between MTHFR gene polymorphisms (C667T; rs 1801133, A1298C; rs 1801131) with migraine susceptibility. In total, 100 patients with migraine (23with MA and 77 with MO) and age-sex matched 100 healthy controls were included in this study from OPD of ESIC Medical College & Hospital, Faridabad. Genotyping was done by PCR-RFLP method. Genotypic and allelic frequencies were compared by SPSS 24 version. Genotypic results indicated a non-significant increase in frequencies of CT and TT in C667T SNP in migraine patients with control (52 and 10% vs. 42 and 7%: p?>?0.05), but CC genotype in A1298C was found to be a risk factor in migraine patients than controls (30 vs. 17% respectively: p?<?0.05). On comparing migraine subclasses, migraine with aura (MA) and without aura (MO) with control groups, the present study suggests that in MTHFR polymorphisms, the prevalence of 677CT genotype and T allele in C667T SNP influences susceptibility to MA (p?<?0.05) but not to MO. Meanwhile, CC genotype in A1298C SNP could be a risk factor for migraine patients without aura (p?<?0.05).     

Central effects of drugs used in migraine prophylaxis evaluated by visual evoked potentials

The present study used recordings of visual potentials evoked by pattern reversal (VEPs) to investigate the central effects of three drugs used in migraine prophylaxis: the calcium channel blocker nifedipine, the beta-1-selective blocker metoprolol, and the nonselective beta adrenoreceptor blocker propranolol. The study involved 58 patients with common or classical migraine who were treated in a double-blind randomized study over a period of 7 months, while the effectiveness of prophylactic treatment was recorded in headache diaries that were subjected to time series analysis. VEPs were recorded at the beginning of a 2-month baseline period without treatment, after 4 months of treatment, and at the end of a 3-month washout period. At baseline, migraine patients had significantly higher VEP amplitudes and longer latencies than did a group of 87 healthy control subjects. Patients were separated by statistical analysis into responders and nonresponders to each prophylactic treatment. Nifedipine had no effects on the frequency, intensity, and duration of migraine attacks, nor on amplitude and latency of the VEPs. In contrast, the use of beta blockers resulted in a significant decrease in VEP amplitude, both in responders and nonresponders, whereas VEP latency remained unchanged. VEP amplitudes returned to the initial values at follow-up in the nonresponders, but stayed at lower levels in responders. Beta blockers thus appear to have a significant effect on the increased excitability of the visual system in patients with migraine, although their action is not directly related to their reduction of migraine frequency.     

Circannual periodicity of migraine?

Seasonal rhythm of migraine attacks may support a role of the suprachiasmatic nucleus of the hypothalamus in the pathophysiology of migraine. The objective of this study was to provide evidence for seasonal variation in migraine. Eighty-nine female migraineurs volunteered to record every migraine attack in detail for 12 consecutive months. Attacks associated with sleep complaints were defined as insomnia-related. By using Edwards' model for recognition and estimation of cyclic trends, time-series analysis was made. Fifty-eight patients, of which 26 had migraine without aura (MO) and 32 had migraine with aura (MA), completed the study. A total of 1840 attacks were recorded. The mean age ± SD was 36.9 ± 6.0. Patients with a lifetime history of MA showed marked seasonal fluctuation with more attacks in the light season compared to the dark. Time of peak was May 21. Peak/low ratio was 1.30 (95% CI: 1.08–1.55). When insomnia-related attacks ( n  = 312) were removed the seasonal variation became insignificant. There is a seasonal trend with more migraine attacks in the light season compared to the dark season in females with MA, but not MO, living in an arctic area. This is caused by the seasonal variation of insomnia-related attacks in patients with MA.