Raymond Levy

The somatosensory evoked response in patients with hysterical anaesthesia.

Abstract The cortical somatosensory averaged evoked response (A.E.R.) was studied in nine patients with hysterical anaesthesia (eight with hemianaesthesia, one with “stocking” anaesthesia). Stimuli were applied either to a peripheral nerve or to skin receptors and the stimulus intensity defined with reference to the threshold of the nerve action potential recorded further up the limb involved. The results were as follows: 1. 1. A.E.R.s should be recorded in all patients even when they reported no subjective sensation. 2. 2. When the stimuli were applied to skin receptors the amplitude of the A.E.R. from the anaesthetic area was always smaller than that from non-anaesthetic area. 3. 3. When stimuli were applied to a peripheral nerve, the anaesthetic area produced a smaller A.E.R. with near-threshold stimuli but when the stimulus intensity was increased the two areas evoked A.E.R.s of comparable amplitudes. 4. 4. In three patients tested after recovery these differences disappeared. It is suggested that at least two separate physiological mechanisms may be involved in the mediation of hysterical anaesthesia, and that the technique may be useful both diagnostically and as a research tool.

Neurophysiological studies on patients with hysterical disturbances of vision.

Abstract The visual fields of patients thought to be suffering from hysteria were the object of a good deal of attention during the 19th and early 20th century. For Charcot [1] the characteristic concentric diminution in the fields of vision constituted one of the classical ‘stigmatas’ of hysteria and even Janet [2] whose thinking was a good deal closer to our own laid great stress on the phenomenon which he considered as being due to an underlying disturbance of attention. The notion of a disturbance of attention or of the ‘field of consciousness’ as Janet preferred to call it, was later elaborated into a general theory of personality development and neurosis [3]. The significance of the phenomenon came under attack by Babinski [4] who felt that it was produced by suggestion during unskilled examination. Great controversy centered round this problem which became something of a ‘cause celebre’. The question gradually fell into oblivion as the conflicting arguments were seen to be increasingly arid. Few psychiatrists would now concern themselves with testing the visual fields of patients who do not complain of visual symptoms but when it comes to psychogenic disorders specifically affecting vision there is little doubt that concentric diminution in the field, tubular fields and ‘spiralling’ of the field are widely accepted as being very frequent [5]. Specific abnormalities of dark adaptation manifesting themselves as ‘night blindness’ were of course very common under war-time conditions [6] but this has now become quite rare. However, there is now a large and growing literature on ‘hysterical amblyopia’ [7–10]. In this condition patients complain of failing vision and are found to have a characteristic alteration in the field of vision often associated with gross abnormalities of dark adaption. The recent development of a technique for recording the dark adapted visual evoked response over the occipital region [11] provides us with a new physiological method of studying visual function in the supposedly blind part of the visual field of such patients and of comparing ‘objective’ dark adaptation with ‘subjective’ dark adaptation as reported by the patient.

Cortical evoked responses in hysterical hemianaesthesia

Abstract Somatosensory cortical evoked potentials (AERs) were recorded from a patient with hysterical anaesthesia of the right arm. Stimuli of different intensities were applied at the wrist to the ulnar nerve and to the skin. The right and left sides were both stimulated in this way and the AER was recorded contralateral to the stimulus. When stimuli were applied to the nerve on the affected side the AER was found to be reduced at low intensities, but at higher intensities the AERs from the two sides were equal. On stimulating skin the AERs from the affected side were smaller in amplitude regardless of the level of stimulation.