Pseudoselectivity of the neuromuscular block in ocular myasthenia: a SFEMG study

The patients with pure ocular myasthenia presenting no signs of neuromuscular transmission defect on classical supramaximal repetitive stimulation were studied using SFMG method. Only those patients were selected to the study in whom the diagnosis of the ocular myasthenia was confirmed by the clinical criteria arranged so as to exclude ophthalmoplegia of the other nature. The series comprises 20 patients in whom the results of the supramaximal repetitive stimulation with the recording from the proximal muscles and with the evaluation of posttetanic phenomena were normal. SFEMG examination was performed in the clinically intact EDC muscle and in 17 patients an elongated jitter, sometimes with blocking was found. Among those three patients with normal results two were in full clinical remission, so there was only one patient presenting the symptoms of ocular myasthenia in whom the neuromuscular transmission defect was absent in the EDC. The results justify an admission that the neuromuscular block in ocular myasthenia is only apparently selective; in fact it concerns all the muscles with a different severity and may be detected if properly sensitive diagnostic methods are applied.