Neurophysiological investigation in optic nerve disease: combined assessment of the visual evoked response and electroretinogram.

Abstract

Patients classified into the above 3 groups were then correlated with clinical findings. The first group of patients (category 1), showed either a number of neurological symptoms to suggest multiple sclerosis without any visual deficit or a sudden transient loss of vision accompanied by pain in the affected eye. They were finally diagnosed as multiple sclerosis with optic neuritis. The second group of patients (category 2), had similar case histories to those of category 1 but showed a more severe, permanent loss of vision, commonly with temporal pallor and pupillary defects. The final diagnoses of these patients were either multiple sclerosis or compressive or ischaemic optic neuropathies. The third group of patients all showed bilateral, gradual, painless loss of vision but were subdivided into 2 distinct clinical diagnostic categories: (a) toxic amblyopia (category 3), and (b) bilateral optic atrophy of unknown cause (category 4).

Electrophysiology in Acute Anterior Ischaemic Optic Neuropathy

“…The ERG were normal in all cases, except for 1 (patient 4), which does not confirm the data of Ikeda et al [1978], The difference between our results and those of Ikeda et al [1978] is not due to the short duration of the ischaemia of our group, for which we also found a normal ERG in 5 patients who had an ischaemic attack a long time ago (ta- [1962] suggested that an abnormal ERG points to a disturbance of the retina, but in the fundus of our patient with the abnormal ERG no cause could be found. Much more interesting are the results of the EOG.…”

“…In the chronic atrophic stage we suppose that there is neither oe dema nor an insufficiency of the choroidal circulation, but only an axonal degenera tion. According to Ikeda et al [1978], it is our experience from chronic circulatory dis turbances and hereditary optic atrophies that in these instances more often amplitude reduction is seen than strong delays which is in reverse to the findings in demyelinating diseases [Halliday et al, 1973] or compres sive lesions [Halliday et al, 1976;van Lith and Henkes, 1978]. An axonal degeneration by a circulatory insufficiency of the small vessels of the optic nerve was also our expla nation for the reduced-pattern response am plitudes with normal latencies found by us in a series of patients with drusen of the optic disc, even when clear field defects and re duced visual acuities were present [BrndelWickel et al, 1981], The present findings of delayed responses in the atrophic stage of AION cannot so easily be explained with these conjectures.…”

“…Ikeda et al [1978], however, describes a significant loss of ERG functions and attributed this to a retrograde neuronal degeneration. Ikeda et al [1978] also investigated pattern-evoked cortical potentials which were reduced in amplitude and delayed, whereas Hennerici et al [1977] only described a delay. Wilson [1978] and Holder [1981] reversely stressed the marked reduction in amplitude with only in some cases a slight delay.…”

Retinal origin of VECP delays as revealed by simultaneously recorded ERG to patterned stimuli

“…While a delayed PVECP peak-time in optic neuropathy is commonly understood in terms of a reduced conduction velocity due to disturbances of the myelin sheaths [27], it is unlikely in cases of retinal diseases that the retinal ganglion cells themselves may be responsible for a delayed PERG peak-time. This thinking follows from results of PERG studies in cases of ocular hypertension or definite glaucoma, in which Papst and associates [28,29] observed reduced p-q amplitudes without a peak-time delay.…”

Axonal electrovisiogram as an electrophysiological test to evaluate optic nerve and inner retina electrical potentials: findings in normal subjects

“…There is also evidence that some potentials as early as 30 milliseconds (ms), known as subcorticals, may have a post-chiasmatic origin, bearing no relation to the ones originated from the retina (6) . Electrophysiological evaluation can also be made with the electroretinogram (ERG) (7) but sometimes, the topographical definition of certain lesions can be inconclusive, especially in cases that involve the optic nerve (7) . The possibility to record the electrical potential of the optic nerve was conceived by Sabadel et al, in 1983, using the axonal electrovisiogram (AxEvg) technique (8) .…”