SIR: Isolation of the speech area, or mixed transcortical aphasia, is a rare language disorder with unusual manifestations.1 Patients with this condition have sparse, nonfluent verbal output and are unable to comprehend spoken language. In contrast, these patients retain the ability to repeat. Occasionally their repetition is prominent, marked by significant echoing or repetition of comments by others. The differential diagnosis of prominent echolalia includes psychosis and vocal tic disorders. We present a patient who developed acute echolalia without other definite neurological changes.
A 58-year-old man became suddenly verbally unresponsive. He was unable to communicate and did not otherwise indicate any discomfort or impairment. His past medical history was significant for hypertension, diabetes mellitus, and smoking, but not for known psychiatric disease. On examination, he was alert and attentive but had little spontaneous verbal output. He attempted to reply to questions but uttered only brief hypophonic and poorly intelligible phrases. The patient was unable to comprehend simple commands and could not name on confrontational naming tasks. Despite this, he frequently repeated back what was spoken to him in an automatic fashion. The rest of his neurological examination was remarkable only for a slight right upper extremity pronation and an equivocal Babinski sign on the right.
Magnetic resonance imaging revealed a left middle cerebral artery stroke that spared the left perisylvian region. Wernicke's area and the pars triangularis and opercularis of the inferior frontal gyrus were spared. Further evaluation revealed a 95% to 98% occlusion of the left internal carotid, and he underwent carotid endarterectomy.
The patient underwent further speech assessment one month after his surgery. He remained near-mute with little spontaneous verbal output, but he retained the ability to repeat phrases and sentences fluently. At unpredictable moments he would lapse into an echolalic mode, parroting the comments of the examiner. He was given portions of several aphasia tests and was able to repeat and perform automatic speech, but he remained impaired in spontaneous fluency and comprehension.
Isolation of the speech area is an unusual stroke syndrome that is of particular interest because of the preservation of repetition despite impaired language fluency and comprehension. This condition has particular neuropsychiatric significance because prominent echolalia must be differentiated from the language of psychosis, tic disorders including Tourette's syndrome, and some frontal disorders such as frontotemporal dementia.
The acute onset in this patient, without other symptoms, suggests a stroke syndrome. As probably occurred in our patient, a common cause for this syndrome is left internal carotid artery occlusion with simultaneous anterior pial territory infarction (precentral-central sulcus) and posterior watershed infarction.1 Other stroke causes include watershed infarctions involving both anterior and posterior cerebral border zones, left thalamomesencephalic infarctions affecting frontal-subcortical circuits, vasospasm, and functional isolation of the speech area evident on functional neuroimaging.2—4 Other evidence indicates a possible role of the intact right hemisphere in spared repetition.5 This unusual patient illustrates the need to perform careful language examinations and stroke evaluations in patients presenting with echolalia.