Thalamic correlated of language and speech

Subcortical anarthria: a case report

A 56-year-old right-handed male with a history of hypertension and diabetes presented two episodes of stroke: The first affected territory was the left anterior coroidal artery (capsular and paracapsular infarcts at the level of the genu and posterior arm of the internal capsule) and the second was the right thalamus, due to a hematoma. Following the first stroke, the patient developed severe dysarthria and after the second stroke remained anarthric. The pathophysiology of the disorder is discussed, and the role of the left and right thalamus as far as speech is concerned is reviewed.

Chronic electrical stimulation of the left ventrointermediate (Vim) thalamic nucleus for the treatment of pharmacotherapy-resistant Parkinson's disease: a differential impact on access to semantic and episodic memory?

Thalamotomy for medically refractory Parkinson's disease (PD) is considered to be efficacious and relatively safe. Because a minority of patients experience decrements in language and memory (often mild and transient) after thalamotomy, chronic thalamic deep brain stimulation (DBS) might be a safer treatment given its reversibility and the modifiability of stimulation parameters. Two preliminary studies support the relative cognitive safety of unilateral DBS of the ventral intermediate (Vim) thalamic nucleus, but it is unclear whether possibly subtle changes in language and memory represent effects of "microthalamotomy" or of stimulation per se. This report provides preliminary data concerning effects of left thalamic stimulation on information processing speed, semantic memory (verbal fluency and visual confrontation naming), and verbal episodic memory in a patient with PD. In addition to being evaluated before and 3 and 6 months after surgery, the patient was tested 18 months after surgery either on or off medications and with the stimulator turned either on or off (order counterbalanced across medication conditions). Test performance differences between the stimulation conditions were attenuated "off" as compared to "on" medication. Vim stimulation consistently, albeit subtly, improved semantic verbal fluency but interfered with immediate recall of word lists. Parallels to findings from acute, intraoperative thalamic stimulation studies are explored. The hypothesis is offered that left Vim stimulation might facilitate access to semantic memory, but interfere with episodic memory processes.

Subcortical aphasia

We critically review the literature on subcortical aphasia, suggest that a number of traditional concepts regarding mechanisms of aphasia are inconsistent with now abundant data, and propose several new hypotheses. The absence of aphasia in 17 reported cases of dominant hemisphere striatocapsular infarction and the finding of nearly every conceivable pattern of language impairment in 33 different reported cases of striatocapsular infarction provide strong evidence against a major direct role of the basal ganglia in language and against disconnection or diaschisis as mechanisms of nonthalamic subcortical aphasia. However, detailed consideration of the vascular events leading to striatocapsular infarction strongly suggests that associated linguistic deficits are predominantly related to sustained cortical hypoperfusion and infarction not visible on structural imaging studies. Thalamic disconnection, as may occur with striatocapsular infarcts with extension to the temporal stem and putamenal hemorrhages, may also contribute to the language deficits in some patients. Review of the literature on thalamic infarction, in conjunction with previously unreported anatomic details of four cases, suggests that what infarcts in the tuberothalamic artery territory and the occasional infarcts in the paramedian artery territory associated with aphasia have in common is damage to the frontal lobe-inferior thalamic peduncle-nucleus reticularis-center median system that may be involved in regulating the thalamic gate in attentional processes. Disruption of attentional gating in the pulvinar and lateral posterior nuclei resulting from such lesions may impair selection of specific neuronal networks in the projection field of these nuclei that serve as the substrate for lexical-semantic function, which is in effect a disruption of a type of working memory, as defined by Goldman-Rakic. We define this as a defect of selective engagement.

Focal dystonia and speech impairment responding to anticholinergic therapy

Focal dystonia of the right hand and speech impairment as a result of a circumscribed left-sided anterior thalamic lesion is reported in a 9-year-old girl with borderline normal psychomotor development. Both focal dystonia and speech impairment improved during anticholinergic treatment and worsened after drug withdrawal.

The effects of electrostimulation and of resective and stereotactic surgery on language and speech

A fairly comprehensive survey is offered of the effects which cortical and sub-cortical electrical stimulation have on language and speech. A survey is also given of the verbal consequences of resections or coagulations which generally follow electrical stimulation.

Language disturbances from mesencephalo-thalamic infarcts. Identification of thalamic nuclei by CT-reconstructions

The authors report the cases of two patients with CT-documented paramedian mesencephalo-thalamic infarcts, showing language disturbances. The first patient showed a non fluent, transcortical motor-like aphasia, the other had a fluent but severely paraphasic language disorder. The CT study disclosed that it was the dorso-median thalamic nucleus that was mostly involved in both cases. These findings agree with a few previous pathological studies suggesting that the paramedian thalamic nuclei, particularly the dorso-median nucleus may play some role in language disturbances. However the anatomical basis for thalamic aphasia remains speculative, taking into account the importance of cortical connections in the origin of subcortical neuropsychological disturbances.

[Analysis and quantitative study of language disorders in lesions of the left thalamus: thalamic aphasia]

We have studied 5 patients having a language disturbance associated with a left thalamic lesion documented by computerized tomography. These patients were submitted to a french adaptation of the Boston Diagnostic Aphasia Examination, originally designed by Goodglass and Kaplan. A quantitative analysis of these language disturbances has shown that they are characterized by reduction of fluency, resembling that of dynamic aphasia, with impaired volume, tone and articulation of speech. There is also a difficulty at finding word categories. Perseverations are frequent while paraphasias are scarce, being then mostly incoherences. Comprehension is impaired, but only at a complex level. Reading and writing are inconsistently affected. This symptom-complex is coherent enough from case to case to be considered as a recognizable type of aphasia, and specially since it is invariably associated with a left thalamic lesion.

Transcortical aphasia from ischaemic infarcts of the thalamus: a report of two cases

Thalamic injury from various natural causes, including tumours an haemorrhage, has been reported to lead abnormalities of language. The pathophysiology of these language disorders remains controversial because the naturally occurring thalamic lesions often are associated with mass effects. Two patients are described with hypodense left thalamic lesions, shown by computed tomography, probably representing infarction. Both patients had aphasia, but neither had evidence of appreciable brain swelling or distortion, nor were cortical language areas damaged.