Original Article
Higher prevalence of migraine in essential tremor: A case-control study
Cephalalgia 2014, Vol. 34(14) 1142–1149 ! International Headache Society 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0333102414531153 cep.sagepub.com
Yueqing Hu, Wenjing Tang, Ruozhuo Liu, Zhao Dong, Xiaoyan Chen, Meiyan Pan and Shengyuan Yu Abstract Background: The existence of an association between migraine and essential tremor has long been controversial. The prevalence of migraine in essential tremor patients was surveyed to explore the association between the two diseases. Methods: A case-control clinical study was conducted to investigate the prevalence of migraine in 150 consecutive essential tremor patients and in 150 matched controls without tremor. Detailed information about essential tremor and migraine was obtained using a structured questionnaire at a face-to-face interview. Moreover, a functional variant of the dopamine receptor D3 gene (Ser9Gly, rs6280) was studied in 46 essential tremor patients with and without migraine using direct sequencing analysis. Results: The prevalence of lifetime migraine in essential tremor patients was significantly higher than that in controls (22.0% vs. 12.7%; p ¼ 0.035; odds ratio ¼ 1.95; 95% confidence interval ¼ 1.05–3.60). No significant difference was found in the migraine features between the essential tremor and control groups and most tremor characteristics were no different in essential tremor patients with and without migraine. A higher male prevalence of essential tremor patients without migraine was observed. Moreover, 44 of 46 (95.7%) essential tremor patients had the dopamine receptor D3 Ser9Gly variant, but no significant difference was found in the frequencies of the variant between essential tremor patients with and without migraine (87.5% vs. 100.0%; p ¼ 0.22). Conclusion: Our data suggest that essential tremor patients have a higher risk of lifetime migraine than do controls and the dopamine receptor D3 Ser9Gly variant may be lower in essential tremor with migraine than the general essential tremor patients. Keywords Essential tremor, migraine, dopamine receptor D3 gene, risk factor Date received: 5 January 2014; accepted: 12 March 2014
Introduction Over past decades, there has been controversy about a possible relationship between essential tremor (ET) and migraine (1–3). One cross-sectional study revealed a bidirectional relationship between the two diseases, finding that 36.5% of ET patients had migraine and 17.2% of migraineurs suffered from ET (1). Another study found that 26.0% of ET patients experienced classic migraine, which was more commonly associated with hereditary ET than with other comorbidities (2). However, these two studies were based on data that did not compare patient characteristics with those of ageand gender-matched controls without tremor. Recently, a case-control study addressed this problem and found no association between ET and migraine when the headache features were compared in 28/110 (25.4%)
patients with migraine and ET and 24/110 (21.8%) controls (3). So, is there a relationship between the two diseases? ET and migraine may share a genetic background. The dopamine D3 receptor (DRD3) gene encodes the DRD3 receptor, expressed in the basal ganglia, cerebral cortex, cerebellum and brainstem nuclei (4,5), which have been implicated in the pathogenesis of ET (6,7)
Department of Neurology, Chinese PLA General Hospital, Beijing, PR China Corresponding author: Shengyuan Yu, Department of Neurology, Chinese PLA General Hospital, Fuxing Road 28, Haidian District, Beijing 100853, PR China. Email: [email protected]
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Hu et al. and migraine (8,9). The single nucleotide polymorphism (SNP) ‘rs6280’ in the DRD3 gene, which causes a Ser9Gly amino acid change in the ETM1 locus, was found to be associated with risk and age at onset of ET in a recent study (10). Additionally, dopamine has been thought to participate in the pathogenesis of migraine (11) and an increased density of lymphocytic DRD3 receptor has been reported in migraineurs (12). Furthermore, no other non-synonymous variant was found in the DRD3 coding sequence in ET patients by a genome-wide scan, apart from the SNP rs6280 variant (10). Thus, the DRD3 Ser9Gly variant can be defined as a functional variant of the DRD3 gene. Further analyses may suggest the possibility of a common mutation and a better understanding of the molecular mechanism(s) in the relationship between ET and migraine. However, to our knowledge, there is no reported study on the frequencies of the DRD3 Ser9Gly variant in ET patients with and without migraine. In this case-control study, we explored the prevalence of migraine in a large sample of consecutive outpatients with ET. A comparative analysis was also designed to find any association between migraine and ET and the proportions of DRD3 Ser9Gly polymorphism in ET patients with and without migraine.
Materials and methods Standard protocol approvals The study protocol was approved by the Ethical Committee of the Chinese PLA General Hospital and complied with the Declaration of Helsinki. Informed consents were obtained from all patients and controls before the study.
Clinical studies In total, 150 unrelated Han Chinese patients diagnosed with definite ET (74 males, 76 females, mean age 54.2 15.9 years) were recruited consecutively from the Department of Neurology, Chinese PLA General Hospital, from 1 March 2011 to 1 July 2013. All patients were diagnosed based on the Washington Heights-Inwood Genetic Study ET criteria (13), which was developed at movement disorder clinics. Tremor was rated on an ordinal scale ranging from 0 to þ3 (0 ¼ no visible tremor; þ1 ¼ barely perceptible tremor or intermittent tremor; þ2 ¼ obvious tremor, amplitude 2 cm). The detailed inclusion criteria were the following: (i) on examination, a þ 2 postural tremor in at least one arm (head tremor may also be present but was insufficient for a diagnosis); (ii) on examination, there must be
a þ 2 kinetic tremor during at least four tasks or a þ 2 kinetic tremor on one task and a þ 3 kinetic tremor on a second task. Tasks included pouring water between two cups, finger-to-nose movements, drinking water from a cup and drawing spirals. Exclusion criteria included: (i) tremor induced by alcohol withdrawal, hyperthyroidism, Parkinson’s disease, psychogenic disorders, anti-dopaminergic drug intake or lithium therapy; (ii) other diseases that affected the patient’s quality of sleep, including chronic obstructive pulmonary disease, coronary heart disease and chronic pain disorders other than migraine; (iii) tremor resulting from other known causes. Additionally, 150 control subjects (74 males, 76 females, mean age 53.8 15.5 years) were consecutively recruited from students, hospital staff and non-consanguineous relatives of inpatients who were available conveniently in our hospital. Inclusion criteria for the controls were: (i) without ET; (ii) match with ET patients by gender, age (2 years) and ethnicity. Exclusion criteria were the same as for the ET group. All ET patients and control subjects underwent a face-to-face interview and a complete physical and neurological examination by the same two neurologists, who were trained to diagnose ET at movement disorder clinics. In the interview, all participants were asked to fill out a structured questionnaire, including detailed information on ET (age at tremor onset, duration and onset site of tremor, whether it spread to other body parts, family history of tremor and any therapy for tremor). Migraine was diagnosed according to the International Classification of Headache Disorders 3rd edition (beta version; ‘ICHD-3-beta’) diagnostic criteria (14). A detailed history of migraine including lifetime/current, age at onset, duration of the headache, presence of aura, accompanying symptoms, frequency per month and location and severity of pain using a visual analogue scale (VAS) was also obtained in the interview. The duration interval of tremor or headache was calculated from the onset of tremor or migraine to the time of assessment. Subsequently, migraineurs were assessed by the same two independent headache specialists blinded for ET diagnosis. Only patients who were diagnosed by both specialists were eligible for migraine study enrolment. These patients were also asked to describe any change in the features of migraine after onset of ET or the beginning of therapy for tremor. Migraine improvement was defined as a reduction of 35–75% in the frequency of attacks or a decrease in the severity of pain or a shortened duration of the attack.
Genetic studies The DRD3 gene (Ser9Gly, rs6280) was evaluated in 46 ET patients (20 males, 26 females, mean age 50.5 15.3
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Cephalalgia 34(14)
years), a subset of the 150 ET patients above, randomly recruited from Department of Neurology, Chinese PLA General Hospital, between 1 July 2012, and 1 July 2013. The patients were separated into two groups: with and without migraine. A single-blind grouping method was used to compare the frequencies of the Ser9Gly variant in the two groups. The diagnostic criteria for ET and migraine were as described above. After patients signed a written informed consent, genomic DNA was extracted from peripheral blood plasma using a standard phenol-chloroform extraction method (15). Polymerase chain reaction (PCR) amplification of the target region of the DRD3 gene was performed using a Veriti thermal cycler system (ABI) and 3 mL of DNA and 1.2 mL primers in a 30-mL reaction volume for 35 cycles at 95 C for 40 s, 58 C for 1 min, 72 C for 1 min and a final extension step at 72 C for 5 min. PCR primers used were forward: 50 -TGTAAAACGACG GCCAGTTAACTAAGCAACCAAGC-30 and reverse: 50 -GGATGAGGGACAGGATGG-30 . PCR products were sequenced directionally using an ABI 3730XL automated sequencer (Applied Biosystems). Alignments and analyses were carried out using the DNAStar software (DNAStar, Inc.). The outcomes of the variant at the protein level were predicted according to cDNA sequences deposited in the National Center for Biotechnology Information RefSeq (the RefSeq accession number of the DRD3 gene is
NG_008842.1). DNA samples from 50 healthy unrelated individuals recruited from the physical examination centre in the outpatient department of our hospital were used as normal controls and were screened by sequencing.
Statistical analysis Data were analysed using non-parametric statistical methods, including logistic regression analysis with odds ratios (OR) and 95% confidence intervals (CI). To describe the demographic data and clinical features of ET and migraine, we used percentages, arithmetic mean values and simple SD. Student’s t-test or the Mann–Whitney U-test was used to compare quantitative variables. Proportions were compared by chisquared tests. SPSS software (ver. 13.0 for Windows) was used for statistical analyses. All calculated p-values were two-tailed and statistical significance was set at a p-value
Higher prevalence of migraine in essential tremor: A case-control study
Cephalalgia 2014, Vol. 34(14) 1142–1149 ! International Headache Society 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0333102414531153 cep.sagepub.com
Yueqing Hu, Wenjing Tang, Ruozhuo Liu, Zhao Dong, Xiaoyan Chen, Meiyan Pan and Shengyuan Yu Abstract Background: The existence of an association between migraine and essential tremor has long been controversial. The prevalence of migraine in essential tremor patients was surveyed to explore the association between the two diseases. Methods: A case-control clinical study was conducted to investigate the prevalence of migraine in 150 consecutive essential tremor patients and in 150 matched controls without tremor. Detailed information about essential tremor and migraine was obtained using a structured questionnaire at a face-to-face interview. Moreover, a functional variant of the dopamine receptor D3 gene (Ser9Gly, rs6280) was studied in 46 essential tremor patients with and without migraine using direct sequencing analysis. Results: The prevalence of lifetime migraine in essential tremor patients was significantly higher than that in controls (22.0% vs. 12.7%; p ¼ 0.035; odds ratio ¼ 1.95; 95% confidence interval ¼ 1.05–3.60). No significant difference was found in the migraine features between the essential tremor and control groups and most tremor characteristics were no different in essential tremor patients with and without migraine. A higher male prevalence of essential tremor patients without migraine was observed. Moreover, 44 of 46 (95.7%) essential tremor patients had the dopamine receptor D3 Ser9Gly variant, but no significant difference was found in the frequencies of the variant between essential tremor patients with and without migraine (87.5% vs. 100.0%; p ¼ 0.22). Conclusion: Our data suggest that essential tremor patients have a higher risk of lifetime migraine than do controls and the dopamine receptor D3 Ser9Gly variant may be lower in essential tremor with migraine than the general essential tremor patients. Keywords Essential tremor, migraine, dopamine receptor D3 gene, risk factor Date received: 5 January 2014; accepted: 12 March 2014
Introduction Over past decades, there has been controversy about a possible relationship between essential tremor (ET) and migraine (1–3). One cross-sectional study revealed a bidirectional relationship between the two diseases, finding that 36.5% of ET patients had migraine and 17.2% of migraineurs suffered from ET (1). Another study found that 26.0% of ET patients experienced classic migraine, which was more commonly associated with hereditary ET than with other comorbidities (2). However, these two studies were based on data that did not compare patient characteristics with those of ageand gender-matched controls without tremor. Recently, a case-control study addressed this problem and found no association between ET and migraine when the headache features were compared in 28/110 (25.4%)
patients with migraine and ET and 24/110 (21.8%) controls (3). So, is there a relationship between the two diseases? ET and migraine may share a genetic background. The dopamine D3 receptor (DRD3) gene encodes the DRD3 receptor, expressed in the basal ganglia, cerebral cortex, cerebellum and brainstem nuclei (4,5), which have been implicated in the pathogenesis of ET (6,7)
Department of Neurology, Chinese PLA General Hospital, Beijing, PR China Corresponding author: Shengyuan Yu, Department of Neurology, Chinese PLA General Hospital, Fuxing Road 28, Haidian District, Beijing 100853, PR China. Email: [email protected]
1143
Hu et al. and migraine (8,9). The single nucleotide polymorphism (SNP) ‘rs6280’ in the DRD3 gene, which causes a Ser9Gly amino acid change in the ETM1 locus, was found to be associated with risk and age at onset of ET in a recent study (10). Additionally, dopamine has been thought to participate in the pathogenesis of migraine (11) and an increased density of lymphocytic DRD3 receptor has been reported in migraineurs (12). Furthermore, no other non-synonymous variant was found in the DRD3 coding sequence in ET patients by a genome-wide scan, apart from the SNP rs6280 variant (10). Thus, the DRD3 Ser9Gly variant can be defined as a functional variant of the DRD3 gene. Further analyses may suggest the possibility of a common mutation and a better understanding of the molecular mechanism(s) in the relationship between ET and migraine. However, to our knowledge, there is no reported study on the frequencies of the DRD3 Ser9Gly variant in ET patients with and without migraine. In this case-control study, we explored the prevalence of migraine in a large sample of consecutive outpatients with ET. A comparative analysis was also designed to find any association between migraine and ET and the proportions of DRD3 Ser9Gly polymorphism in ET patients with and without migraine.
Materials and methods Standard protocol approvals The study protocol was approved by the Ethical Committee of the Chinese PLA General Hospital and complied with the Declaration of Helsinki. Informed consents were obtained from all patients and controls before the study.
Clinical studies In total, 150 unrelated Han Chinese patients diagnosed with definite ET (74 males, 76 females, mean age 54.2 15.9 years) were recruited consecutively from the Department of Neurology, Chinese PLA General Hospital, from 1 March 2011 to 1 July 2013. All patients were diagnosed based on the Washington Heights-Inwood Genetic Study ET criteria (13), which was developed at movement disorder clinics. Tremor was rated on an ordinal scale ranging from 0 to þ3 (0 ¼ no visible tremor; þ1 ¼ barely perceptible tremor or intermittent tremor; þ2 ¼ obvious tremor, amplitude 2 cm). The detailed inclusion criteria were the following: (i) on examination, a þ 2 postural tremor in at least one arm (head tremor may also be present but was insufficient for a diagnosis); (ii) on examination, there must be
a þ 2 kinetic tremor during at least four tasks or a þ 2 kinetic tremor on one task and a þ 3 kinetic tremor on a second task. Tasks included pouring water between two cups, finger-to-nose movements, drinking water from a cup and drawing spirals. Exclusion criteria included: (i) tremor induced by alcohol withdrawal, hyperthyroidism, Parkinson’s disease, psychogenic disorders, anti-dopaminergic drug intake or lithium therapy; (ii) other diseases that affected the patient’s quality of sleep, including chronic obstructive pulmonary disease, coronary heart disease and chronic pain disorders other than migraine; (iii) tremor resulting from other known causes. Additionally, 150 control subjects (74 males, 76 females, mean age 53.8 15.5 years) were consecutively recruited from students, hospital staff and non-consanguineous relatives of inpatients who were available conveniently in our hospital. Inclusion criteria for the controls were: (i) without ET; (ii) match with ET patients by gender, age (2 years) and ethnicity. Exclusion criteria were the same as for the ET group. All ET patients and control subjects underwent a face-to-face interview and a complete physical and neurological examination by the same two neurologists, who were trained to diagnose ET at movement disorder clinics. In the interview, all participants were asked to fill out a structured questionnaire, including detailed information on ET (age at tremor onset, duration and onset site of tremor, whether it spread to other body parts, family history of tremor and any therapy for tremor). Migraine was diagnosed according to the International Classification of Headache Disorders 3rd edition (beta version; ‘ICHD-3-beta’) diagnostic criteria (14). A detailed history of migraine including lifetime/current, age at onset, duration of the headache, presence of aura, accompanying symptoms, frequency per month and location and severity of pain using a visual analogue scale (VAS) was also obtained in the interview. The duration interval of tremor or headache was calculated from the onset of tremor or migraine to the time of assessment. Subsequently, migraineurs were assessed by the same two independent headache specialists blinded for ET diagnosis. Only patients who were diagnosed by both specialists were eligible for migraine study enrolment. These patients were also asked to describe any change in the features of migraine after onset of ET or the beginning of therapy for tremor. Migraine improvement was defined as a reduction of 35–75% in the frequency of attacks or a decrease in the severity of pain or a shortened duration of the attack.
Genetic studies The DRD3 gene (Ser9Gly, rs6280) was evaluated in 46 ET patients (20 males, 26 females, mean age 50.5 15.3
1144
Cephalalgia 34(14)
years), a subset of the 150 ET patients above, randomly recruited from Department of Neurology, Chinese PLA General Hospital, between 1 July 2012, and 1 July 2013. The patients were separated into two groups: with and without migraine. A single-blind grouping method was used to compare the frequencies of the Ser9Gly variant in the two groups. The diagnostic criteria for ET and migraine were as described above. After patients signed a written informed consent, genomic DNA was extracted from peripheral blood plasma using a standard phenol-chloroform extraction method (15). Polymerase chain reaction (PCR) amplification of the target region of the DRD3 gene was performed using a Veriti thermal cycler system (ABI) and 3 mL of DNA and 1.2 mL primers in a 30-mL reaction volume for 35 cycles at 95 C for 40 s, 58 C for 1 min, 72 C for 1 min and a final extension step at 72 C for 5 min. PCR primers used were forward: 50 -TGTAAAACGACG GCCAGTTAACTAAGCAACCAAGC-30 and reverse: 50 -GGATGAGGGACAGGATGG-30 . PCR products were sequenced directionally using an ABI 3730XL automated sequencer (Applied Biosystems). Alignments and analyses were carried out using the DNAStar software (DNAStar, Inc.). The outcomes of the variant at the protein level were predicted according to cDNA sequences deposited in the National Center for Biotechnology Information RefSeq (the RefSeq accession number of the DRD3 gene is
NG_008842.1). DNA samples from 50 healthy unrelated individuals recruited from the physical examination centre in the outpatient department of our hospital were used as normal controls and were screened by sequencing.
Statistical analysis Data were analysed using non-parametric statistical methods, including logistic regression analysis with odds ratios (OR) and 95% confidence intervals (CI). To describe the demographic data and clinical features of ET and migraine, we used percentages, arithmetic mean values and simple SD. Student’s t-test or the Mann–Whitney U-test was used to compare quantitative variables. Proportions were compared by chisquared tests. SPSS software (ver. 13.0 for Windows) was used for statistical analyses. All calculated p-values were two-tailed and statistical significance was set at a p-value
