Impaired parts
Case 93
【Progress】
At admission, his sensory disturbance, memory (impressive) disturbance and walking impairment still remained. Because he had cognition disturbance of such as the schedule and words during speaking, he relied upon using visual documents. Walking rehabilitation could expand and strength his walking ability from using device and instrument to using a stick or by himself.
【Discussion】
There is a Y shaped laminal layer in the thalamus dividing three parts: anterior, medial and lateral. Further, lateral part is subdivided into subparts, lateral and inferior (pulvinar). These parts are basically blood-supplied from branches of posterior cerebral artery; anterior part from polar branch (tubero-thalamic) artery; medial part from paramedian branch artery; lateral subpart from inferior lateral branch artery: inferior subpart (pulvinar) from posterior choroidal artery.
Our patient had thalamic hemorrhage. Brain CT and MRI showed hemorrhage occupied medial part, lateral part including lateral subpart and inferior subpart (pulvinar). The problem is what the responsible artery to hemorrhage is. The main symptoms of our patient are right sensory impairment, right paralysis, dysarthria and cognition impairment. Of these, sensory disturbance was fixed with no improvement, cognition disturbance remained, hemiparesis and dysarthria were getting improved by rehabilitation. Lateral part includes motor nucleus (ventral anterior nucleus and ventral lateral nucleus) and sensory nucleus (ventral posterior nucleus) (1-6). Of the symptoms in our patient, sensory impairment was greatest, next, cognition impairment followed by hemiparesis and dysarthria, implying that inferior lateral artery is the probable artery responsible to hemorrhage. The greater hemorrhage is considered to cause knock-on negative effect to the surrounding. In short, sensory (ventral posterior) nucleus was the greatest damage followed by motor nucleus (ventral anterior nucleus and ventral lateral nucleus) inducing disorder of paresis and dysarthria. Dysarthria is reported to be caused by disorder of basal ganglia circuit which includes motor nucleus (ventral anterior and ventral lateral nucleus) of the thalamus (2).
Thalamus was once considered to passively relay information to cortex (1). In these days, several evidences are listed that thalamus play a role of connecting and interacting between cortexes which is meant to be higher order function; pulvinar disorder can produce severe attention deficit: mediodorsal nucleus disorder can produce memory deficit (3-6). Thalamic interactions with cortical and subcortical pathways are important to behavior activity, memory and recognition process (4-6). Further, the cerebellum sends information to prefrontal cortex and posterior parietal cortex and additionally to association areas, serving cognitive functions (3, 4). The damages of ventrolateral nucleus cause the disorder of cognitive function. In our patient, brain CT and MRI showed hemorrhage at medial part and pulvinar of the thalamus. He suffered from memorizing the schedule and relied upon visual items, suspicious of damages of mediodorsal nucleus and/or ventrolateral nucleus.
Pulvinar works integration of visual and oculomotor signals and functions as a key of visual attention function. A main role of pulvinar is to participate in generation of visual salience: the suppression of noise and enhancement of significant signals (7). Fortunately, our patient did not get damages of attention or oculomotor behavior either, indicating the least damage of pulvinar.
【Summary】
We present a sixty six-year-old male suffering from right hemiparesis, severe sensory disorder, dysarthria and cognition. Brain CT and MRI showed hemorrhage of left thalamus. We should keep in mind that, in thalamus, sensory nucleus is related to ventral posterior nucleus whose damages cause sensory disorder, and motor nucleus is related to ventral anterior & ventral lateral nuclei whose damages cause contralateral paresis, dysarthria and cognition disorder. Cognition nucleus is related to medial dorsal nucleus whose damage cause cognition disorder.
【References】
1.Haber S et al. The place of the thalamus in frontal cortical-basal ganglia circuits. Neuroscientist. 2001 Aug;7(4):315-24.
2.Ackermann H, et al. Dysarthria in bilateral thalamic infarction. A case study. J Neurol. 1993 Jun;240(6):357-62.
3.Saalmann YB, et al. The cognitive thalamus Front Syst Neurosci. 2015; 9: 39. Published online 2015 Mar 17. doi: 10.3389/fnsys.2015.00039 PMCID: PMC4362213
4.Baxter M. G. Mediodorsal thalamus and cognition in non-human primates. Front. Syst. Neurosci. 2013; 7:38. 10.3389/fnsys.2013.00038 [PMC free article] [PubMed] [Cross Ref]
5.Bradfield L. A., et al. The role of the anterior, mediodorsal, and parafascicular thalamus in instrumental conditioning. Front. Syst. Neurosci. 2013; 7:51. 10.3389/fnsys.2013.00051 [PMC free article] [PubMed] [Cross Ref]
6.Funahashi S. Thalamic mediodorsal nucleus and its participation in spatial working memory processes: comparison with the prefrontal cortex. Front. Syst. Neurosci. 2013; 7:36. 10.3389/fnsys.2013.00036 [PMC free article]
7.Arend I, et al. The role of the human pulvinar in visual attention and action: evidence from temporal-order judgment, saccade decision, and antisaccade tasks. Prog Brain Res. 2008;171:475-83. doi: 10.1016/S0079-6123(08)00669-9.
2018.2.21
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