[Magnesium balance in patients with spasmophilia. Relation to results of electromyography]

The pathophysiological basis of spasmophilia is frequently magnesium deficiency and the therapeutic administration of magnesium salts has usually a favourable effect. However the parameters of magnesium balance are not always consistent with the results of electromyography. The objective of the present work was to test and interpret the relationship of results of these two basic diagnostic procedures indicated when spasmophilia is suspected.

Thirty-three subjects (9 men and 24 women) with suspected spasmophilia were examined by non-invasive electromyography, using the technique of surface electrodes. All subjects had concurrently biochemical examinations: serum calcium and ionized calcium, serum magnesium (S-mg), magnesium in erythrocytes (ery-Mg) and magnesium in the blood haemolysate (H-Mg). In 29 patients and oral magnesium loading test was made with evaluation of the urinary Mg excretion after a constant Mg load (U-Mg). Statistical evaluation of the investigated parameters of the magnesium balance revealed a highly significant relationship between ery-Mg and U-Mg and H-Mg and ery-Mg (p < 0.005). A less close relationship was found between H-Mg and S-Mg (p < 0.05). Total and ionized calcium was in all examined subjects within the range of the arbitrary normal range. The EMG finding was positive (the finding of two and more multiplets in the ischaemic and hyperventilation test resp.) in 30 instances, i.e. in 91% of the examined subjects. In 72% there was agreement of the positivity of the EMG and magnesium deficiency (i.e. reduced values of ery-Mg and U-Mg), positivity of EMG combined with normal parameters of the Mg balance was recorded in 18%. In 6.1% of the examined subjects magnesium deficiency was confirmed combined with a normal EMG finding.

Concurrent positivity of EMG and magnesium deficiency in 72% justifies the therapeutic administration of magnesium. In patients with a normal magnesium deficiency and positive EMG another cause of spasmophilia must be taken into consideration, incl. technical errors of interpretation of EMG results. A negative EMG associated with magnesium deficiency can suggest the central form of tetany, where magnesium treatment is also unequivocally indicated.