Influence of MTHFR genotype on contingent negative variation and MRI abnormalities in migraine.

Background: The MTHFR C677T genotype has been associated with increased risk of migraine, particularly of migraine with aura (MA) in selected clinical samples and with elevated homocysteine. The hyper-homocysteinemia may favor the vascular and neuronal mechanism underlying migraine, and the risk of stroke.

Objective: The first aim of the present study was to examine the Contingent Negative Variation (CNV) amplitude and habituation pattern in a migraine sample versus non-migraine subjects, at the light of the MTHFR genotype, according to an unrelated and clinical based case-control panel. The second aim was to compare the frequency of Magnetic Resonance Imaging (MRI) subclinical brain lesions across the different C677 genotypes in the same migraine sample, selected for the young age and the absence of any cardiovascular risk factor.

Methods: One hundred and five 18-45 year old out-patients, 90 affected by migraine without aura (MO) and 15 by MA, and 97 non-migraine healthy subjects, age and sex matched, were selected for the genetic analysis. All subjects had a common ethnic origin from Puglia. Sixty-four migraine subjects and 33 control subjects were submitted to the recording of the CNV. All migraine subjects underwent the MRI evaluation.

Results: The frequency of homozygosis was 14.33% in normal subjects, versus 25.7% in MA + MO group (chi2-test: 10.80 P= .001). The frequency of homozygosis in MO patients, was 25.5% (MA versus N: chi2-test: 9 P= .003), in MA group it was 26.6%. Considering the MTHFR genotype in migraine patients and controls, the C677TT subjects exhibited a reduced habituation index of the early CNV (iCNV), in respect with both C677TC and C677CC; in the migraine group, there was a significant decrease of CNV habituation in patients with homozygosis and a positive correlation between the habituation index values and the homocysteine levels. Nineteen migraine patients exhibited subclinical brain lesions (18.05%): patients with C677T homozygosis did not exhibit a higher risk for MRI abnormalities.

Conclusions: This unrelated and clinical based case-control study showed that genetically induced hyper-homocysteinemia may favor the neuronal factors predisposing to migraine, while it does not influence the presence of subclinical vascular brain lesions probably linked with increased risk of stroke.