Observations on stammering after localized cerebral injury.

Despite the advances made in the understanding of speech mechanisms in the past few decades (Nielsen, 1946; Penfield and Roberts, 1959), stammering remains as much of an enigma as ever and continues to be relegated to the province of non-organic disease for want of information clearly explaining its aetiology. It had been suggested in the past (Travis, 1931) that stammering might have a neurophysiological basis, perhaps in the form of bilateral cerebral representation for speech. The high percentage of left handedness and ambidexterity among stammerers (Bryngelson, 1932) lent further support to a theory suggesting an imperfect degree of cerebral dominance and/or bilateral cerebral activity as factors concerned in the mechanism of stammering, but the lack of techniques to test these hypotheses brought an end to this line of thought. It is quite clear that the majority of people use one cerebral hemisphere, nearly always the left, for speech (Penfield and Roberts, 1959). However, there have been some recent suggestions that certain individuals organize their speech mechanisms in both cerebral hemispheres (Branch, Milner, and Rasmussen, 1964). Such individuals are usually left handed or ambidextrous and often show evidence of 'mixed' cerebral dominance in other sensory modalities, i.e., eyedness, earedness, and footedness. Some of this recent information relating to cerebral speech dominance centres around Wada's intracarotid amytal test (Wada and Rasmussen, 1960) which is used to forecast neurological deficits following surgery for temporal lobe epilepsy, speech being the major parameter under consideration. It was felt that this technique would offer a method of further evaluating stammerers should the opportunity present itself. The present study is concerned with four patients who had intracranial lesions in the region of the presumed 'speech areas' and incidentally stammered. Their stammering was unquestionably severe, had been present since childhood, and was obviously unrelated to their intracranial pathology. These patients were studied preand postoperatively with particular reference to their speech laterality by means of Wada's intracarotid amytal test as well as by all other measurable manifestations of cerebral dominance such as eyedness, earedness, and footedness. Wada's intracarotid amytal test was used almost exactly as originally suggested by him in 1960 and is described below. An 18 gauge needle was inserted into the common carotid artery as for a carotid arteriogram. The right and left sides were injected on different days in order to have maximum alertness and cooperation from the patient: no premedication was given as a rule. Using a 5 ml. syringe, 10% sodium amytal in doses of 150 to 200 mg. was injected moderately quickly (1 to 2 sec.). The injection was made with the patient counting, with forearms up in the air and the fingers either moving constantly or gripping an examiner's hand. The knees were drawn up so that the feet were resting on the table close to the buttocks. As the injection was completed, the contralateral arm and leg would slump to the table and become flaccid. The ipsilateral arm and leg would remain up in the air and voluntary movements could be carried out on this side on command as soon as the initial few seconds of confusion were over. The patient would usually hesitate or stop counting near the end of the injection, but if the non-dominant hemisphere had been injected, would resume on request in five to 20 seconds and then would name objects accurately while the contralateral hemiplegia was still complete. When it was the dominant hemisphere that had been injected the patient was unable to continue counting while the contralateral hemiplegia was complete. On command the patient would carry out voluntary movements with the ipsilateral extremities, as soon as the initial brief period of confusion had passed, demonstrating that he was cooperating and that lack of speech was not caused by disturbances of consciousness or cooperation. As tone and power began to return in the contralateral arm and leg, the patient began to respond with 'yes' and 'no' and then was able to count. There was usually a period of one to three minutes during which typically dysphasic 192 P rocted by coright.