Muscle Biopsy Correlated with Electromyography

S U M M A R Y — T o f ind w h a t the cor re la t ion is and ver i fy if is poss ib le to avo id ex tens ive e l ec t romyograph i c examinat ion , s t udy ing o n l y one muscle, 100 patients w i th neuromuscu la r d i sorders (58 p r imary myopa th ie s , 32 neu rogen ic d i sorders and 10 m y o t o n i c dys t roph ies ) w e r e submi ted to quant i f ied e l e c t r o m y o g r a p h y ( E M G ) and musc le b i o p s y ( M B ) wi th fresh-¬ -frozen sec t ion plus h i s tochemis t ry in the same musc le , but on the oppos i t e s ide. T h e E M G was abnormal in 98% and M B in 93% of the cases. E M G and M B had a c o n c o r d a n c e of 84.3% in the neu rogen ic d i so rde r s and 84.77% in the p r imary myopa th ies . A cor re la t ion of 80% was obta ined be tween all M B and E M G ( inc lud ing the cases o f m y o t o n i c d y s t r o p h i e s ) , r ega rd ing the o r ig in of the pa thogen ic p rocess ( p < 0 . 0 1 ) . T h e E M G had 5% incons is tences and the M B 11%, wi th respect to the pa thogen ic p rocess . W h e n the m y o t o n i c d y s t r o p h y was separated f rom the p r i m a r y myopa th ies and f rom the denervat ion d i sorders , a comple t e conco rdance w a s found in all M B and had o n l y 3.4% incons is tences in the denerva t ion d i sorders and 3.1% in the p r i m a r y myopa th ies .