Myasthenia gravis: the effect of Tensilon on the caloric nystagmus response. Photoelectronystagmographic study.

The nystagmus response evoked by thermic vestibular stimulation on 25 patients with myasthenia gravis and on 10 control persons was investigated using the photoelectronystagmographic method before and after administration of Tensilon. On the basis of 19 nystagmograms (capable of being evaluated) it was found that the test is of diagnostic value when combined with abstinence from drugs, furthermore, it may indicate under- or overtreatment of patients taking drugs. Excluding the drug-resistant, "burned out" cases, a certain correlation may be observed between the magnitude of the reaction evoked by Tensilon and the severity of the clinical condition independent from the existence of ocular symptoms. The advantage of the test, apart from being numerically measurable, is that it can be repeated because of its non-invasive nature causing no physical burden to the patient. Its disadvantage is that it cannot be applied in cases with a pre-existent difference in vestibular tonus - 20% in the material tested.