HISTOLOGICAL SUPPORT FOR THE DIFFERENCE BETWEEN MALIGNANT HYPERTHERMIA SUSCEPTIBLE (MHS), EQUIVOCAL (MHE) AND NEGATIVE (MHN) MUSCLE BIOPSIES

The aim of this study was to find, using modern techniques, any histol ogical differences in muscle biopsies between malignant hyperthermia ( MH) susceptible (MHS), MH equivocal (MHE) and MH negative (MHN) patien ts. On the basis of the European MH contracture test carried out in 83 patients, 23 were shown to be MHS, nine MHE and 51 MHN. Four lesions were found with a significantly high frequency in MHS and MHE biopsies : muscle fibre hypertrophy and atrophy, internal nuclei and myofibrill ar necrosis. These four lesions were observed together in 35% of MHS b ut in none of the MHE or MHN biopsies, Three of these lesions occurred together in 57% of MHS, 33% of MHE and 4% of MHN biopsies. Our result s support a histological difference between MHE, MHS and MHN biopsies and attempt to contribute towards a better definition of MHE status.