Hepatic cytochrome P450-mediated oxidation function in migraine

Headache and liver disease: is their relationship more apparent than real?

Headache is regarded by patients as a disturbing (or unpleasant) symptom. It can be produced by either organic diseases or functional head abnormalities. Twenty-five years ago headache was supposed to be a psychosomatic angiospastic algia. Certain unusual forms were thought to be caused by triggers like anger, cough, exertion, and sexual activity. Experimental research explored the role of circulating serotonin, prostaglandin, estrogen levels, and platelet abnormalities. As computed tomography, helical computed tomography, and scanning or magnetic resonance imaging evolved, new data became available. None of the newer reports have demonstrated liver involvement as a cause of headache. This minireview intends to cover the spectrum of brain alteration in liver disease. It describes some of the pathophysiological characteristics of hepatic encephalopathy and, also, the relationship among migraine, constipation, and liver disease.

Transient visual disturbances during migraine without aura attacks

OBJECTIVE

To evaluate the prevalence and clinical features of transient visual disturbances (TVDs) during migraine without aura (MO) attacks and to point out any similarities with the disturbances listed among the diagnostic criteria of the International Headache Society (IHS) classification for migraine with aura (MA).

METHODS

We studied a sample of 191 patients (145 women and 46 men) with MO and no other associated forms of primary headache who had been referred to the University of Parma Headache Centre between December 1, 1999 and December 1, 2000.

RESULTS

A total of 165 patients reported that they had never experienced TVDs during their MO attacks. In the remaining 26 patients (19 women and 7 men), MO attacks were at times accompanied by TVDs, which were present in over 30% of MO attacks in 65.4% of patients. In about 60% of cases, TVDs lasted less than half a minute. TVDs consisted of phosphenes in most patients, general blurring of vision in about one-fourth, and scintillating scotomas in 15%. In 73% of cases, TVDs occurred during the headache phase, whereas in the remainder they preceded it. Strict application of the IHS diagnostic criteria would have led to a diagnosis of MA in 12 cases, corresponding to 46% of our MO patients with TVDs and to 6.3% of all patients with an established clinical diagnosis of MO.

CONCLUSION

The results of our study suggest that current IHS diagnostic criteria for MA may lead to an overestimation of MA cases.

A prospective study of the headache phase in 32 migraine with aura patients

For an accurate description of the clinical features of the headache phase in migraine with aura (MA) attacks, we thought it useful to conduct a prospective study of consecutively referred MA patients seeking treatment at the Headache Centre of the University of Parma Institute of Neurology. The case series included 32 patients (22 women and 10 men). At the time of the first visit, each patient was given a questionnaire to be filled in at the next MA attack. Six patients (four women and two men) had attacks of migraine aura without headache. Among the remaining 26 patients (18 women and eight men), the duration of the headache phase was <24 h in 23 (88.5%); pain location was bilateral in 14 (53.8%) and unilateral in 12, but occurring on the opposite side to aura only in one patient; pain intensity was mild or moderate in 13 (50.0%). The headache phase of MA appeared to have clinical features that differed widely from patient to patient and was consistent with the International Headache Society diagnostic criteria for migraine without aura in 26.9% of patients and for tension-type headache (TTH) in 23.1%.

Cytochrome P450 2D6 and glutathione S-transferase M1 genotypes and migraine

BACKGROUND

Migraine is thought to be a disease of the brain and trigeminovascular system. Migraine patients often claim that stress, food, and beverages trigger their attacks. Chemical substances in these foodstuffs with the property of triggering migraine attacks have not yet been characterised. Cytochrome P450 2D6 (CYP2D6) and glutathione S-transferase M1 (GSTM1) are thought to be present in the brain. They metabolise numerous environmental compounds. The genes exhibit genetic polymorphism that is associated with altered enzyme activity. The aim of this study was to determine if the genotypes of these two enzymes are associated with migraine.

MATERIALS AND METHODS

The study included 100 female patients and 245 female controls from the general population. Genomic DNA was isolated from whole blood. Allele specific PCR methods were used to identify the normal CYP2D6*1 allele and the mutated CYP2D6*3 and CYP2D6*4 alleles. Initially all samples were genotyped only for GSTM1 plus (+) and GSTM1 null (-) variants. All samples positive for GSTM1 were further analysed for the presence of allelic variants GSTM1*A and GSTM1*B.

RESULTS

None of the CYP2D6 and GSTM1 genotypes was associated with migraine. We observed an odds ratio (OR) for the poor metaboliser genotype of CYP2D6 of 1.4 (95% CI = 0.5-3.6) and for the GSTM1 null genotype of 1.0 (95% CI = 0.6-1.5).

CONCLUSION

The results of this study indicate that deficient metabolism because of mutated CYP2D6 alleles or GSTM1 allele variants is not important in the aetiology of migraine.

Cytochrome P-450-dependent hydroxylation in migraine

The hypothesis was tested that an acute oxidation deficiency related to potential dietary trigger factors plays a role in the migraine attack. Migraine sufferers (14F and 4M), fulfilling the criteria for migraine with and without aura according to the classification of the International Headache Society, were coadministered oral mephenytoin (100 mg) and debrisoquine (10 mg) during the initial phase of a typical migraine attack. This was repeated during a period without migraine. The hydroxylation of mephenytoin and debrisoquine hydroxylation did not differ during and without the migraine attack. We conclude that hydroxylation, via cytochrome P-450 (2D6, 2C8 and 9), is not reduced during the migraine attack. The results do not support the hypothesis that oxidation deficiency is involved in the pathophysiology of migraine.

Cytochrome-P450-dependent hydroxylation in cluster headache

Two isozymes of the cytochrome-P450-dependent drug oxidizing system exhibit polymorphism. Five to 10% of a Caucasian population are deficient in debrisoquine-hydroxylase activity and about 3% in mephenytoin-hydroxylase activity (poor metabolizers). We tested the hypothesis of a possible over-representation of poor metabolizers among patients with cluster headache. The individual metabolic capacity was determined in 30 cluster headache patients after administration of a test dose of 10 mg of debrisoquine and 100 mg of mephenytoin. Two patients (6.7%) were poor metabolizers of debrisoquine and one (3.3%) a poor metabolizer of mephenytoin. This was no different from the rate of poor metabolizers, 7.1% and 3.3% respectively, in a reference panel of healthy Swedish volunteers.