PT - JOURNAL ARTICLE AU - M. J. Campbell AU - E. Simpson AU - A. L. Crombie AU - J. N. Walton TI - Ocular myasthenia: evaluation of Tensilon tonography and electronystagmography as diagnostic tests AID - 10.1136/jnnp.33.5.639 DP - 1970 Oct 01 TA - Journal of Neurology, Neurosurgery & Psychiatry PG - 639--646 VI - 33 IP - 5 4099 - http://jnnp.bmj.com/content/33/5/639.short 4100 - http://jnnp.bmj.com/content/33/5/639.full SO - J Neurol Neurosurg Psychiatry1970 Oct 01; 33 AB - The value of electronystagmography (ENG) and of tonography in monitoring the beneficial effect of edrophonium chloride (Tensilon) on the extraocular muscles in myasthenia gravis has been assessed. Studies were performed on 17 patients with myasthenia gravis and on 18 control subjects, of whom nine had extraocular muscle weakness due to myopathic or neurogenic lesions. Electronystagmography recorded the repetitive following movements of the eyes elicited during optokinetic nystagmus. Neuromuscular fatigue with the subsequent beneficial response to Tensilon was clearly seen in 50% of patients with myasthenia. False positive responses were not seen in control subjects but in many of these, as in the remaining myasthenic patients, the amplitude and rate of nystagmus seen in the ENG was very variable. These difficulties suggest that the ENG is of limited value as a diagnostic test in myasthenia gravis. Tonography, recording the intraocular pressure of the eye continuously over four minutes, was found to be of considerable value. We found that the intraocular pressure fell on average by 1·6 to 1·8 mm Hg over a one minute period in the control recordings but increased by a mean of 1·6 mm Hg in patients with myasthenia, with a peak effect 35 seconds after Tensilon. In only one patient was there a complete failure of response. This patient, and also another woman who showed a less striking response, had severe myasthenia with a fixed ocular weakness. It is suggested that an absence of any increase in tension with Tensilon may be seen in patients with permanent neostigmine-resistant myopathic change. A small false positive response was seen on one occasion only in a patient with a sympathetic nerve lesion. Tensilon tonography, as a simple painless procedure, would appear to be of considerable value in the diagnosis of ocular myasthenia and also as a diagnostic test in the exclusion of myasthenia as a cause of isolated extraocular neuromuscular weakness.