Elevated visual evoked potential amplitude and reduced brain Mg levels may predict migraine

A novel study published in Neurology India suggests that level of serum magnesium and visual evoked potentials (P100) can become good predictors of migraine patients.

Reduced intracellular magnesium (Mg) levels in serum, blood cells, saliva, as well as cerebrospinal fluid are associated with migraineurs compared to non-migraineurs that contributes the assumption that headache of migraine perhaps is an Mg-deficiency condition.

Various presumable mechanisms have been explained the association between level of Mg and migraine attacks. Interestingly, the correlation between Mg and calcium channels is well established. In migraineurs, deficiency of Mg in brain cortex triggers the calcium channels opening and consequently, raised level of intracellular calcium and extracellular potassium is found, which ultimately provokes cortical spreading depression.

Mg concentration has a dominant effect on the nitric oxide level in the cell, which is lacking in migraineurs, particularly in females. As well, reduced Mg can be related with decreased platelet aggregation, elevated level of serotonin and consequently, vasoconstriction which may be predominant inherent aetiology for the events of migraine attacks.

Visual evoked potentials (VEPs) abnormalities have been reported in migraineurs compared to non-migraineurs. VEPs alterations have an influential impact on latency and the amplitude of the leading positive wave (P100) in migraineurs. They have been elucidated as indicators of anatomical lesions of the optic pathway because of ischemia between the attacks. Migraineurs having no clinical or brain imaging manifestations of apparent neurological destruction have also been demonstrated milder VEPs abnormalities.

Till today, lack of reported study that correlate VEPs changes and serum Mg level. Shenoy et al aimed to evaluate serum Mg levels in migraineurs between attacks compared to non-migraineurs, and also wished to establish a correlation between Mg levels and VEPs.

After applying inclusion and exclusion criteria as per the study protocol, in total, 80 subjects were enrolled in the study. Of which 40 were migraineurs diagnosed as per the International Headache Society criteria for severe migraine headache. Rest of 40 was non migraineurs served as a control group of the study. All included patient was submitted to demographic profile, previous history of the disease and drug intake, thorough clinical investigation and baseline laboratory parameters. Apart from this, the measurement of visual evoked potentials changes (4th block) and magnesium levels were done as per standard operating procedures.

Their study showed an interictal low serum Mg level in migraineurs compared to healthy subjects with a significant difference.Correlating serum Mg levels with VEPs, they observed a lower P100 amplitude and latency associated with decreased Mg + 2 levels.

They hypothesised that inverse correlations between serum Mg level and amplitude mean that when serum Mg level decreases, amplitude increases and vice versa for increased values. That shows that lower magnesium level could promote transmission in the visual pathway through the hyperexcitability of neural cells. The contemporary recordings of the electroretinogram pattern may be of vast importance to identify the function of the retina.

“As we concluded, the neurophysiological expression of the hyperexcitability could be the shorter latency and the higher amplitude of P100. The neural hyperexcitability could explain a lower threshold for migraine attacks. After therapy, the VEP changes reverse, proposing a potential remedial role of Mg in the therapy of migraineurs in whom low Mg level was found”, said the authors.

They concluded that elevated visual evoked potential amplitude and reduced brain Mg level could both be a representation of neuronal hyperexcitability of the optic pathways associated with a reduced threshold for migraine attacks.

Reference

Can Serum Magnesium Level and Visual Evoked Potentials (P100) be a Predictive in Migraineurs?: Evidence Based Study Nisha N Shenoy, Gaurang K Gheewala, Rakshith Kedambadi, Shivanand Pai, K Misri Zulfikli, Ramesh Naidu, Rohit Pai, Feral Daruwala Neurology India, Vol. 71, No. 3, May-June 2023, pp. 463-466 DOI: 10.4103/0028-3886.378668