Language and speech correlates of anatomically verified lesions in thalamic surgery for parkinsonism

Neural substrates of subcortical aphasia in subacute stroke: Voxel-based lesion symptom mapping study

Subcortical aphasia develops as a result of damage to subcortical brain areas without loss of cortical functions. Although earlier voxel-based lesion-symptom mapping (VLSM) studies have shown possible neural correlates for aphasia, it remains to be clarified which brain regions are associated with subcortical aphasia. The aim of this study was to investigate the neural substrates associated with subcortical aphasia in patients with stroke using VLSM and atlas-based analyses to explore the involvement of white matter tracts and subcortical structures. Fifty patients with subacute subcortical stroke without cortical involvement were retrospectively enrolled: 24 with and 26 without aphasia. We performed VLSM and atlas-based analyses of the patients' fluid-attenuated inversion recovery images and found that the left perisylvian white matter, left fronto-occipital fasciculus, uncinate fasciculus, and forceps minor were significantly more greatly affected in the aphasia than in the non-aphasia group. The left anterior thalamic radiation, cingulum (cingulate gyrus), and superior longitudinal fasciculus also showed higher involvement in this group (marginal significance). Among the subcortical regions, the left caudate and putamen were more greatly involved in the aphasia group. Our findings confirm language processing as one of the integrated sensory-motor processes that occur in the region around the left sylvian fissure. Our atlas-based analysis approach can be used to complement VLSM analyses.

Transient Aphasia Following Resection of a Thalamic Cavernous Malformation

BACKGROUND

The thalamus has a demonstrated role in language, particularly through its connectivity to frontal language cortices.

CASE DESCRIPTION

A 59-year-old man with transient mixed aphasia following resection of a left-sided thalamic cavernous malformation is reported. No operative complications were encountered, and there was no surgical contact with cortical language areas. The patient recovered full language function within a week postoperatively.

CONCLUSIONS

The role of thalamic nuclei in language processes and other reports of transient thalamic aphasia are reviewed.

Focused ultrasound thalamotomy in Parkinson disease: Nonmotor outcomes and quality of life

OBJECTIVE

To examine nonmotor outcomes and correlates of quality of life (QoL) 3 and 12 months after unilateral focused ultrasound thalamotomy in tremor-dominant Parkinson disease (TDPD).

METHODS

Twenty-seven patients with TDPD in a double-blind, sham-controlled, randomized clinical trial underwent comprehensive neuropsychological evaluations. These included assessment of mood, behavior, and QoL at baseline, 3 months, 3 months post crossover in the sham group, and 12 months after active treatment. We used Mann-Whitney U tests to assess differences between the active (n = 20) and sham (n = 7) groups at 3 months and Friedman tests to assess within-group changes after active treatment. We assessed correlations between disease variables and postoperative QoL using Kendall tau-b tests.

RESULTS

There were no differences in cognition, mood, or behavior between the active and sham groups at 3-month blinded assessment. After active treatment, there were no differences in mood or behavior. Only declines in Stroop Color Naming and phonemic fluency were observed. Patients experienced postoperative improvements in QoL and activities of daily living (ADL). Mood and behavioral symptoms, aspects of cognitive functioning, ADL, and overall motor symptom severity, but not tremor severity specifically, were associated with QoL.

CONCLUSIONS

In TDPD, unilateral focused ultrasound thalamotomy appears safe from a cognitive, mood, and behavioral perspective. QoL and ADL significantly improved following surgery. Nonmotor symptoms and ADL were more closely associated with QoL than tremor severity.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that for patients with TDPD, unilateral focused ultrasound thalamotomy did not adversely change cognition, mood, or behavior at 3 months.

Speech changes induced by deep brain stimulation of the subthalamic nucleus in Parkinson disease: involvement of the dentatorubrothalamic tract

OBJECTIVE Patients with Parkinson disease (PD) who undergo subthalamic nucleus (STN) deep brain stimulation (DBS) often develop a deterioration in speech performance, but there is no clear consensus on the specific effects seen or the mechanism involved and little description of the impact of DBS on conversational speech. Furthermore, there has been no fiber tract connectivity analysis to identify the structures potentially modulated by DBS to cause such deficits. The main objective of this study was to quantify spontaneous speech performance and identify potential involvement of the dentatorubrothalamic tract (DRTt) in patients who underwent STN DBS, because this tract has been implicated in speech deterioration. METHODS Spontaneous speech samples were obtained with STN DBS in both on and off modes in 35 patients with PD and assessed across multiple domains. Diffusion tensor imaging tractography seeded from the therapeutic DBS contacts was performed to identify the fiber tracts involved and, specifically, the DRTt. The position of active electrode contacts was assessed relative to that of the STN. RESULTS Fifteen patients with akinetic-rigid (AR) PD and 20 with tremor-dominant (TD) PD subtypes were identified. In the AR-PD subgroup of patients, in whom there was DRTt involvement, 71% demonstrated much better overall speech and largely improved or unchanged fluency in the DBS-off condition. In patients with TD PD with DRTt involvement, 50% demonstrated better overall speech in the off condition, and equivocal results regarding improved or worsened fluency were found. When there was minimal DRTt involvement, 75% of patients with AR PD had better overall speech in the DBS-on condition and better or minimal fluency changes. Similarly, 83% of patients with TD PD with minimal DRTt involvement had better or minimal overall speech and fluency changes in the on condition. More medially placed left electrode contacts were associated with more DRTt involvement in 77% of patients (10 of 13). CONCLUSIONS To the authors' knowledge, this is the first study to have investigated a specific fiber tract involved in STN DBS in different subtypes of PD relative to its impact on spontaneous speech. At optimal therapeutic programming of STN DBS, overall spontaneous speech and fluency were affected more negatively in patients with AR PD than in those with TD PD when there was DRTt involvement. After fiber tract analysis and modeling, it was found that medially positioned left electrode contacts more often involved fibers of the DRTt. If possible, avoidance of the DRTt by using active electrode contacts that are positioned less medially, specifically in patients with AR PD, might result in less speech deterioration.

A review of brain circuitries involved in stuttering

Stuttering has been the subject of much research, nevertheless its etiology remains incompletely understood. This article presents a critical review of the literature on stuttering, with particular reference to the role of the basal ganglia (BG). Neuroimaging and lesion studies of developmental and acquired stuttering, as well as pharmacological and genetic studies are discussed. Evidence of structural and functional changes in the BG in those who stutter indicates that this motor speech disorder is due, at least in part, to abnormal BG cues for the initiation and termination of articulatory movements. Studies discussed provide evidence of a dysfunctional hyperdopaminergic state of the thalamocortical pathways underlying speech motor control in stuttering. Evidence that stuttering can improve, worsen or recur following deep brain stimulation for other indications is presented in order to emphasize the role of BG in stuttering. Further research is needed to fully elucidate the pathophysiology of this speech disorder, which is associated with significant social isolation.

Connectivity of the subthalamic nucleus and globus pallidus pars interna to regions within the speech network: a meta-analytic connectivity study

Cortico-basal ganglia connections are involved in a range of behaviors within motor, cognitive, and emotional domains; however, the whole-brain functional connections of individual nuclei are poorly understood in humans. The first aim of this study was to characterize and compare the connectivity of the subthalamic nucleus (STN) and globus pallidus pars interna (GPi) using meta-analytic connectivity modeling. Structure-based activation likelihood estimation meta-analyses were performed for STN and GPi seeds using archived functional imaging coordinates from the BrainMap database. Both regions coactivated with caudate, putamen, thalamus, STN, GPi, and GPe, SMA, IFG, and insula. Contrast analyses also revealed coactivation differences within SMA, IFG, insula, and premotor cortex. The second aim of this study was to examine the degree of overlap between the connectivity maps derived for STN and GPi and a functional activation map representing the speech network. To do this, we examined the intersection of coactivation maps and their respective contrasts (STN > GPi and GPi > STN) with a coordinate-based meta-analysis of speech function. In conjunction with the speech map, both STN and GPi coactivation maps revealed overlap in the anterior insula with GPi map additionally showing overlap in the supplementary motor area (SMA). Among cortical regions activated by speech tasks, STN was found to have stronger connectivity than GPi with regions involved in cognitive linguistic processes (pre-SMA, dorsal anterior insula, and inferior frontal gyrus), while GPi demonstrated stronger connectivity to regions involved in motor speech processes (middle insula, SMA, and premotor cortex).

Effects of deep brain stimulation in the caudal zona incerta on verbal fluency

BACKGROUND

Deep brain stimulation (DBS) of the caudal zona incerta (cZi) is a relatively unexplored and promising treatment in patients with severe essential tremor (ET). Preliminary data further indicate that the ability to produce language may be slightly affected by the treatment.

OBJECTIVE

To evaluate the effects on verbal fluency following cZi DBS in patients with ET.

METHOD

Seventeen consecutive patients who had undergone DBS of the cZi for ET were tested regarding verbal fluency before surgery, 3 days after surgery and after 1 year. Ten patients were also evaluated by comparing performance on versus off stimulation after 1 year.

RESULTS

The total verbal fluency score decreased slightly, but significantly, from 22.7 (SD = 10.9) before surgery to 18.1 (SD = 7.5) 3 days after surgery (p = 0.036). After 1 year the score was nonsignificantly decreased to 20.1 (SD = 9.7, p = 0.2678). There was no detectable difference between stimulation on and off after 1 year.

CONCLUSION

There was a tendency of an immediate and mostly transient postoperative decline in verbal fluency following cZi DBS for ET. In some of the patients this reduction was, however, more pronounced and also sustained over time.

Surgical approaches to treatment of Parkinson's disease: Implications for speech function

Although neurosurgical procedures have been reported to be successful in relieving many of the motor symptoms of Parkinson's disease (PD) (e.g., tremor, rigidity, bradykinesia) in the limb musculature, their effect on speech is much less consistent. This paper will review and evaluate reports in the literature on the effects of various surgical interventions for PD, including thalamotomy, pallidotomy, and DBS, on speech. In particular the paper will focus on the implications of these findings for one's understanding of the neurological control of the speech mechanism. As a foundation, contemporary models of the neuropathophysiology of PD and hypokinetic dysarthria will be outlined and explained. The various neurosurgical treatments for PD will be described and their theoretical underpinning discussed with regard to their proposed effects on subcortical and cortical motor control systems. Evidence suggestive of the need to reconsider contemporary thinking in relation to the neurology of speech and the need to differentiate it from limb neurology will be highlighted.

Progression of dysprosody in Parkinson's disease over time--a longitudinal study

Parkinsonian speech or hypokinetic dysarthria results from a multidimensional impairment of phonation, articulation, and prosody. Although the dysprosody in Parkinson's disease (PD) is well described (alterations in speech rate and pause time, speech intensity and pitch variation), little is known about alterations of these single prosodic parameters over a longer time course. The objective of this study is to analyze changes of speech rate and pitch variation in patients with PD over time and to compare these findings with healthy controls. Patients with PD (N = 50; 27 male and 23 female) and n = 50 age-matched healthy controls (25 male, 25 female) were tested and retested after at least 7 months (mean: 25.02; median: 21; SD: 17.44; range: 7-79 months). In the PD group, motor impairment according to UPDRS motor score was similar at first and second visit. The participants had to accomplish a standardized four sentence reading task. The acoustical analysis was performed using a standard head-worn microphone for voice recordings and commercial audio software (WaveLab). For the determination of intonation based upon fundamental frequency (F(0)) variation, we used a computer analysis program (Praat). Articulatory velocity was determined by measurement of syllable rate and pause ratios. In the PD group, total speech rate (syllables per second related to total speech time/TSR) and net speech rate declined from first to second examination, especially in the male patients, but showed no significant differences to the control group. The course of pitch variation revealed some gender particularities. Whereas female patients' pitch variability declined over time, male patients' intonation variability remained relatively stable. F(0) variation in male and female patients with PD were significantly reduced compared with the control group in the first examination and the follow up as well. Progression of prosodic impairment over time showed no correlation to disease duration or UPDRS motor score. Some aspects of dysprosody in PD show characteristic changes over time, but show no clear correlation with general motor impairment as assessed by UPDRS motor score. Therefore, we suspect that the underlying mechanism could be independent from dopaminergic deficits.

Speech and language disturbances due to subcortical lesions

Over the last few decades, the number of studies concerning the role of subcortical structures in cognition has increased due to advances in neuroimaging. We describe the language and speech disturbances found in 16 patients with subcortical lesions (9 in basal ganglia and 7 in thalamus), evaluated by CT scan, MRI, and SPECT. Language assessment included the Boston Diagnostic Aphasia Examination, Boston Naming Test, and Token Test. Motor-articulatory alterations predominated in the non-thalamic group; in the thalamic group, there was a higher frequency of language alterations, especially in naming and auditory comprehension; verbal memory and attentional impairments may have contributed to this. We also found hypoperfusion in cortical language areas, and therefore participation of cortical dysfunction cannot be ruled out.

Thalamus and language: interface with attention, memory and executive functions

Subcortical structures are in a strategic functional position within the cognitive networks. Their lesion can interfere with a great number of functions. We studied six patients with thalamic vascular lesions (three left sided, two right sided and one bilateral), to characterize their repercussion in the communicative abilities and the interface between language alterations and other cognitive abilities, as attention, memory and frontal executive. All patients were evaluated through a functional interview (discourse analysis), and the following batteries: Boston Diagnostic Aphasia Examination, Boston Naming Test, Token Test, Benton Visual Retention Test, Trail Making, Wisconsin Card Sorting and frontal scripts. All patients performed MRI and five underwent SPECT. Results show that these patients present impairment in several cognitive domains, especially attention and executive functions (working memory, planning and self-monitoring); those with right lesions have an additional visuospatial impairment. Such alterations interfere with language abilities, and this fact must be considered in the rehabilitation efforts.

Neural pathways underlying vocal control

Vocalization is a complex behaviour pattern, consisting of essentially three components: laryngeal activity, respiratory movements and supralaryngeal (articulatory) activity. The motoneurones controlling this behaviour are located in various nuclei in the pons (trigeminal motor nucleus), medulla (facial nucleus, nucl. ambiguus, hypoglossal nucleus) and ventral horn of the spinal cord (cervical, thoracic and lumbar region). Coordination of the different motoneurone pools is carried out by an extensive network comprising the ventrolateral parabrachial area, lateral pontine reticular formation, anterolateral and caudal medullary reticular formation, and the nucl. retroambiguus. This network has a direct access to the phonatory motoneurone pools and receives proprioceptive input from laryngeal, pulmonary and oral mechanoreceptors via the solitary tract nucleus and principal as well as spinal trigeminal nuclei. The motor-coordinating network needs a facilitatory input from the periaqueductal grey of the midbrain and laterally bordering tegmentum in order to be able to produce vocalizations. Voluntary control of vocalization, in contrast to completely innate vocal reactions, such as pain shrieking, needs the intactness of the forebrain. Voluntary control over the initiation and suppression of vocal utterances is carried out by the mediofrontal cortex (including anterior cingulate gyrus and supplementary as well as pre-supplementary motor area). Voluntary control over the acoustic structure of vocalizations is carried out by the motor cortex via pyramidal/corticobulbar as well as extrapyramidal pathways. The most important extrapyramidal pathway seems to be the connection motor cortex-putamen-substantia nigra-parvocellular reticular formation-phonatory motoneurones. The motor cortex depends upon a number of inputs for fulfilling its task. It needs a cerebellar input via the ventrolateral thalamus for allowing a smooth transition between consecutive vocal elements. It needs a proprioceptive input from the phonatory organs via nucl. ventralis posterior medialis thalami, somatosensory cortex and inferior parietal cortex. It needs an input from the ventral premotor and prefrontal cortex, including Broca's area, for motor planning of longer purposeful utterances. And it needs an input from the supplementary and pre-supplementary motor area which give rise to the motor commands executed by the motor cortex.

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.

Localization of a pontine vocalization-controlling area

To find out whether there exist additional regions in the pontine brainstem, apart from the phonatory motoneuron pools involved in vocal motor control, the effects of a localized blockade of excitatory neurotransmission in the pons were studied on squirrel monkey vocalization. Vocalization was elicited by electrical stimulation of the periaqueductal gray of the midbrain. Blockade was carried out by stereotaxic injections of kynurenic acid, a nonspecific glutamate antagonist. It was found that injections made into the ventrolateral pons around the ventral nucleus of the lateral lemniscus and superior olive could block periaqueductally elicited vocalization. Injections were only effective ipsilaterally, not contralaterally to the stimulation site. The blockade was limited to one particular class of calls, all of which had in common a characteristic stereotyped frequency modulation over several kHz. It is concluded that critical processing steps of vocal motor control take place in the periolivary region.

Cognitive functioning after subthalamic nucleotomy for refractory Parkinson's disease

OBJECTIVE

To evaluate whether subthalamic nucleotomy produces adverse cognitive effects in patients with Parkinson's disease.

METHOD

Twelve patients with Parkinson's disease underwent stereotactic surgery to the subthalamic nucleus. Presurgical and postsurgical neuropsychological assessment of attention, memory, executive function, language, and verbal intellect were undertaken with a battery of tests designed to minimise potential contamination of cognitive effects by motor symptoms.

RESULTS

There was no statistically significant difference in the cognitive tests results after operation for the group as a whole. Reliable change indexes were generated for the cognitive tests. Reliable change postoperatively was found on specific tests of verbal memory, attention, and planning. Left sided operations were associated with greater incidence of deterioration postsurgery.

CONCLUSIONS

Preliminary data on the first reported cognitive changes after subthalamic nucleotomy suggested few adverse cognitive effects of the surgery although discrete neuropsychological changes were seen in some patients. These effects were consistent with current theories on the cognitive functions of the basal ganglia.

Effect of stimulation of the subthalamic nucleus on oral control of patients with parkinsonism

OBJECTIVES

To assess the oral system of parkinsonian patients treated with chronic stimulation of the bilateral subthalamic nucleus (STN) to evaluate precisely the effectiveness of this procedure on the articulatory organs.

METHODS

Load sensitive cantilevers were used to sample ramp and hold force contractions generated by the upper lip, lower lip, and tongue. The subject was given the instruction to produce forces as rapidly and as accurately as possible in response to the target signal (ranging from 0.25 to 2 N), which appeared on a screen. Maximal force of each effector organ was also measured. Fourteen healthy control subjects and 10 patients participated in this study. After an overnight fast the patients were evaluated in the morning under two conditions: during bilateral stimulation and 1 hour after stopping STN stimulation.

RESULTS

During STN stimulation, dynamic and static control of the articulatory organs were improved: the maximal strength of the articulatory organs, their accuracy to reach the target, and the precision of the hold phase increased. In addition, the reaction time and the rise time of the ramp phase decreased. Patients' speech as assessed by the item 18 of the unified Parkinson's disease rating scale (UPDRS) was greatly improved by electrical stimulation of the STN CONCLUSIONS: Improvement of oral control of the stimulated patients suggests that STN stimulation modulates neuronal structures involved in speech. However, more patients have to be evaluated for a fuller understanding of the effect of this surgical procedure on speech.

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.

Neuropsychological functioning before and after unilateral thalamic stimulating electrode implantation in Parkinson's disease

One theoretical advantage of chronic thalamic stimulation compared with thalamotomy for the treatment of refractory Parkinson's disease (PD) entails the avoidance and reversibility of potential cognitive morbidity. Support for the cognitive safety of thalamic stimulation remains largely anecdotal; empirical data are limited to the neuropsychological findings published for one small series of patients. The purpose of this study was to supplement those published findings that pertain to the mean changes in neuropsychological test scores and to extend previous findings by evaluating cognitive changes in individual cases from preoperative baseline to 4 months after electrode implantation. Nine patients with tremor-dominant, refractory PD underwent unilateral implantation of a deep brain stimulating electrode in the ventralis intermedius thalamic nucleus (five patients on their left and four patients on their right sides). A neuropsychological test battery was administered to each patient to evaluate attention, language, memory, and visuoperceptual and executive functions during their best “on” state before surgery, while on a medication regimen, and with the stimulator turned on after surgery. As a group, the patients attained significantly higher scores on word list recognition (discriminability) and delayed recall of prose passages after surgery than before surgery. In addition, there was a trend toward higher scores on a visual confrontation naming test after surgery. Examination of individual patient data indicated gains and losses in test scores exceeding two standard deviations to be very rare. Changes of one standard deviation were also relatively rare, but gains were more likely to occur than losses. These observations provide preliminary support for the cognitive safety of thalamic stimulation for PD.

Cognitive function in patients with Parkinson's disease undergoing stereotaxic thalamotomy

OBJECTIVE

To determine whether thalamotomy leads to cognitive disturbances in patients with Parkinson's disease.

METHODS

A total of 53 patients with Parkinson's disease undergoing stereotaxic ventrolateral thalamotomy for tremor and rigidity were tested for cognitive functions before and after surgery. The cognitive functions investigated involved visuospatial perception and memory. verbal memory, attention shift, and executive functions including set maintenance and shift. A neuropsychological test battery was used that contained the Wisconsin card sorting test, Street completion test, Stroop test, a dichotic memory listening test, and a facial recognition test.

RESULTS

Clinically, a good or moderately good effect on parkinsonian symptoms was obtained in 50 patients. The neuropsychological investigations showed that the patients were impaired compared with healthy age matched control subjects on most tests, showing slight improvement postoperatively on verbal memory and visuospatial perception. No major differences were found between tests before and after operation, and there were no significant differences between patients undergoing surgery in the right or in the left thalamus.

CONCLUSION

The study indicates that ventrolateral thalamotomy does not reduce the cognitive capacity in this group of patients.

Dysarthria in bilateral thalamic infarction. A case study

A patient suffering from bilateral thalamic infarction in the region supplied by the paramedian arteries sparing the internal capsules underwent acoustic analysis of sentence utterances. The results were compared with the findings obtained in parkinsonian subjects, in patients with upper motor neuron lesions, and in normal subjects. Acoustic measurements revealed increased pitch, monotonous speech, rough voice quality, and normal speech tempo concomitant with articulatory impreciseness in terms of incomplete closure productions. This constellation resembled parkinsonian dysarthria. Damage to the thalamic projection area of the pallidal efferents, therefore, seems to be the most probable cause of the patient's speech disorders. In parkinsonian subjects stereotactical lesions of this structure ameliorate rigor, but not akinesia. Thus, our patient's speech deficits, and by analogy the corresponding parkinsonian dysarthric disturbances, may be considered akinetic signs.

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.

Subcortical aphasia from a thalamic abscess

A patient is reported who was treated successfully for a left thalamic abscess that resulted in subcortical aphasia. A SPECT scan showed large areas of hypoperfusion in the cortex of the left hemisphere. At follow up after seven months there was marked improvement in the language disorder and the cortical hypoperfusion. It is suggested that aphasia in patients with subcortical lesions results from secondary cortical dysfunctions. The evidence is confined to patients with stroke lesions. The possible implications of this case on current theories of pathophysiological mechanisms, in particular the ischaemic penumbra theory and the cortical diaschisis theory, are briefly discussed. Cortical diaschisis may be the appropriate explanation in this patient.

Subcortical lesions and aphasia

Recent evidence suggests that subcortical lesions can give rise to aphasic symptoms. Two subcortical structures thought to participate in the pathogenesis of aphasia are the basal ganglia and the thalamus. This paper reports on 3 patients with lesions of the thalamus and 10 patients with lesions of the basal ganglia, most of whom had persistent aphasias. The role of subcortical structures in aphasia and the importance of subcortical structures in neural models of language are discussed.

Neuropsychological functioning in hemiparkinsonism

A standardized neuropsychological battery including measures of intellectual cognitive, memory, attention-concentration, language, abstraction and mental flexibility, and sensory and motor functions was administered to 21 hemiparkinsonian patients (14 with right side and 7 with left side symptoms) and 17 controls matched for age and education. Patients were impaired in all functions except sensory. For motor functions, impairment was ipsilateral to the side of symptoms. For cognitive functions, right side symptoms were associated with verbal deficits whereas left side symptoms were associated with spatial deficits. Thus, a pattern of neuropsychological deficits consistent with the lateralization of motor symptoms may appear in the early stages of the disease.

Thalamic aphasia. A conceptional critique

Four patients with aphasia due to small circumscribed thalamic lesions are presented. A review of the literature on thalamic aphasia revealed 16 similar cases. While the general consensus that only left-sided thalmic lesions are associated with aphasia is confirmed, analysis of the sites of the thalamic infarctions and the dysphasia elements did not reveal an unequivocal correlation. The explanation of this finding is that (a) disruption of any circuit, whether taking place in the connections or in the nuclei, leads to dysfunction and (b) thalamofrontal connections are not topographically arranged according to the thalamic nuclei, but show a frontal rostrocaudal/thalamic mediolateral interrelationship irrespective of thalamic nuclear masses.

Evaluation of memory and language function pre- and postthalamotomy with an attempt to define those patients at risk for postoperative dysfunction

Memory and language dysfunction has been sporadically reported following stereotaxic thalamotomies. In order to determine which patients are at greatest risk and to better define the nature of this dysfunction, we have prospectively evaluated 18 patients undergoing stereotaxic thalamotomies for movement disorders (MDs). Patients were evaluated clinically, with computed tomography (CT) and with memory and language protocols (MLPs) pre- and postoperatively. Patients exhibiting postoperative deficits were again evaluated with the MLP on follow-up visits to the clinic. Significant changes in memory and language function occurred in 7 out of 18 patients. These 7 patients had diverse etiologies for their MDs. Five of the 18 patients had undergone previous thalamotomies on the contralateral side. Three of these 5 patients with bilateral thalamotomies experienced postoperative functional impairments in memory and language while only 4 of 13 patients with a unilateral thalamotomy experienced these problems. The postoperative functional impairments noted were primarily those requiring orientation and speech. All patients with postoperative memory and language impairments were again evaluated with MLPs months after the operation. In 3 of 7 patients, no improvement was noted, while the remaining 4 did recover to baseline. More severe deficits tended to occur in those patients with ventriculomegaly or evidence of other major cerebral tissue loss by preoperative CT scan and in those patients with lower MLP scores preoperatively. Postoperative memory and language dysfunction was not correlated with the number or size of the lesions made, the postoperative general neurologic examination or CT scans, or the clinical response of the MDs. From our data, it appears that patients with more profound neurologic compromise and/or bilateral involvement as evidenced by poor performance on the MLP, tissue loss on CT scanning, or previous thalamic lesion, are most at risk for memory and language dysfunction postoperatively. However, this dysfunction is not necessarily permanent. Preoperative evaluation with MLPs and CT scanning appear to be of value in predicting those patients at greatest risk for postoperative and language dysfunction.

The computer and stereotactic surgery in neurological surgery

The technical aspects, current uses, and future clinical applications of stereotactic surgery and three-dimensional imaging in neurological surgery are reviewed.

The effects of brainstem lesions on vocalization in the squirrel monkey

The present study is an attempt to find out the brain areas involved in the motor coordination of species-specific vocalization. For this purpose, high-frequency coagulations were placed in a systematic manner throughout the brainstem and posterior diencephalon in altogether 43 squirrel monkeys (Saimiri sciureus). The effect of these lesions on different call types elicited by electrical brain stimulation was studied spectrographically. It was found that bilateral destruction of the ventrolateral, ventroposterior and intralaminar thalamus, periventricular and rostral periaqueductal gray, ventral tegmental area of Tsai, nucl. interpeduncularis, nucl. ruber, anterodorsolateral midbrain tegmentum, superior and inferior colliculi, pontine gray, cerebral peduncles, medial pontine reticular formation, raphe and vestibular nuclei did not affect the acoustic structure of the calls tested. On the other hand, lesions in the ventrolateral midbrain involving the substantia nigra and overlying reticular formation, in the midbrain tegmentum just below the inferior colliculus, in the lateral pons and almost the whole medulla (minimal lesion size: 2.5 mm3) changed vocalization significantly. It is suggested that the latter areas are more or less directly involved in the motor coordination of vocalization, while the first are not.

Depression after stereotactic thalamotomy in patients with abnormal movements

A reversible depressive syndrome was found to be a very frequent side effect in a series of 33 patients subjected to stereotaxic surgery for the correction of abnormal movements. The depression was rated according to clinical and to Rorschach test parameters. The syndrome correlated significantly with age, depression being more frequent in adolescence, and with the side of the stereotaxic lesion, depression being more frequent after left thalamotomies in righthanded patients. The first correlation is of practical relevance, since it would clearly be wise to perform surgery before adolescence. The second correlation is of speculative interest in that is suggest a hemispheric asymmetry in the mood regulation processes. The incidence of this side effect in patients with abnormal movements may be further explained by the peculiar features of these patients, who need to be studied thoroughly before surgery.

[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.

Afferents to the cortical larynx area in the monkey

In 3 squirrel monkeys (Saimiri sciureus) horseradish peroxidase was injected into the cortical larynx area within the lower sensorimotor face cortex. Retrogradely labeled cells were found in a continuous band extending all along the upper bank of the Sylvian fissure from Broca's area rostrally to the parietal association cortex (area 7) caudally. In addition, labeled cells were found in the ventrolateral prefrontal cortex, orbital cortex, anterior cingulate gyrus, supplementary motor area, insula and inferior temporal gyrus. Subcortically, labeled neurons were situated in the substantia innominata, basolateral amygdaloid nucleus, lateral and posterior hypothalamus, the thalamic nuclei ventralis lateralis, ventralis posteromedialis, medialis dorsalis, centralis lateralis, centralis inferior, parafascicularis and pulvinaris, the periventricular gray, reticular formation, nucl. annularis, nucl. centralis superior (Bechterew) and locus coeruleus. Many of these structures are connected with the cortical larynx area reciprocally. The possible phonatory role of some of them is discussed.

Aphasia and left thalamic hemorrhage

Left thalamic hemorrhage as a cause of aphasia has not been widely recognized. Large thalamic hemorrhages cause coma, making speech examination impossible; smaller thalamic hemorrhages were difficult to document until recent diagnostic advances. Nine cases of thalamic hemorrhage with aphasia have been described in the literature. This report presents four additional cases. These patients had acute onset of aphasia, supranuclear paralysis of upward gaze, right hemisensory deficits, and mild right hemiparesis. Three of the four patients responded to ventriculostomy drainage with rapid clearing of the supranuclear paralysis of upward gaze, and two later required placement of permanent ventricular shunts. After 1 year, two patients exhibited no clinically detectable speech malfunction and the other two were severely aphasic. The hemiparesis, hemisensory deficits, and ocular pareses all cleared. These cases are discussed with respect to present models of the role of the thalamus in speech.