Characteristics of cognitive impairment due to stroke in different lateralized anterior thalamic nuclei groups
[Abstract] Objective To investigate the characteristics of cognitive impairment due to stroke in the left and right anterior thalamic nucleus clusters. Methods Eight patients (6 on the left side and 2 on the right side) with anterior thalamic nucleus cluster stroke underwent extensive cognitive testing, and the results were compared with the mean values of 80 normal controls to determine the cognitive domains impaired. Results Six patients with left-sided anterior thalamic cluster stroke had severe verbal memory impairment and three patients had graphic memory involvement, with a more prominent decline in delayed recall performance. five patients had executive function impairment. two patients with right-sided anterior thalamic cluster stroke had only mild verbal memory impairment and normal graphic memory. Conclusions The left anterior thalamic nucleus is a key site of memory and cognition, and damage can lead to severe memory and cognitive impairment. Damage to the right anterior thalamic nucleus has a lesser effect on memory and cognition. Lateralization of the processing of verbal and graphic cognitive material at the thalamic level is not constant. Zhou Aihong, Department of Neurology, Xuanwu Hospital, Capital Medical University
[Keywords] Cognitive impairment; anterior thalamic nucleus
Stroke in the thalamus can cause significant memory impairment and other cognitive impairments, leading to dementia in severe cases. There are many nuclei in the thalamus, among which the anterior thalamic nucleus is widely connected with the frontal cortex and hippocampus and plays an important role in the memory loop [1,2]. Currently, the characteristics of cognitive impairment due to stroke in the anterior thalamic nucleus are still unclear and the differences in cognitive impairment due to stroke in the left and right lateralities need to be investigated. In this study, we applied a broad cognitive assessment to investigate the characteristics of cognitive impairment due to stroke in the left and right anterior thalamic nucleus to provide a basis for clinical diagnosis.
Data and methods
I. Study population
Eight patients with acute onset anterior thalamic nucleus stroke were enrolled in the Xuanwu Hospital Stroke Clinic of Capital Medical University from January 2009 to May 2010 (Table 1). There were 6 cases of left-sided stroke and 2 cases of right-sided stroke. Six cases were male and two were female, aged 45 to 72 years, with 6 to 17 years of education. Case 6 had hemorrhage in the left anterior thalamic nucleus and the rest had infarction. 6 patients with left-sided stroke had sudden onset of memory impairment, unresponsiveness and other higher cortical functions as the main symptoms, cases 2 and 6 had apathy and lack of self-knowledge, case 1 had right-sided limb weakness, and case 4 had dizziness. The right-sided stroke patients in cases 7 and 8 both had left-sided limb weakness as the main symptom, but in case 8 the weakness had recovered by the time of cognitive assessment. The National Institutes of Health Stroke Scale (NIHSS) score was 2 for one left-sided and one right-sided stroke patient and 0 for the rest. All patients had a confirmed head MRI or CT scan in the acute phase of onset.
Table 1 Demographic and clinical characteristics of the patients
Characteristics
Case 1
Example 2
Case 3
Case 4
Example 5
Example 6
Example 7
Example 8
Normal control
Sex (male/female)
Male
Male
Male
Male
Female
Male
Male
Female
56/24
Age (years)
45
65
46
69
60
61
72
45
65.85 (6.94)
Years of education (years)
11
13
17
6
8
11
8
8
10.00 (3.35)
Stroke side
left
left
left
Left side
Left side
Left side
Right side
Right side
Stroke type
Infarct
infarct
infarction
infarction
infarction
hemorrhage
infarction
infarction
NISSH
2
0
0
0
0
0
2
0
MRI/CT
MRI left anterior thalamic nucleus T1 low signal, T2 high signal
MRI left anterior thalamic nucleus T1 low signal, T2 high signal
MRI left anterior thalamic nucleus T1 low signal, T2 high signal
MRI left anterior thalamic nucleus T1 low signal, T2 high signal
MRI left anterior thalamic nucleus T1 low signal, T2 high signal
CT high density in the left anterior thalamic nucleus
MRI right anterior thalamic nucleus T1 low signal, T2 high signal
MRI right anterior thalamic nucleus T1 low signal, T2 high signal
Normal controls were 80 cases, all healthy volunteers from the community, without neurological or psychiatric disorders, without intellectual impairment, without systemic diseases that may cause cognitive impairment, and with a Clinical Dementia Rating Scale score of 0.
II. Study methods
All subjects underwent extensive cognitive measures and the patient group was assessed 3 months after the stroke. Except for the mini-mental state examination (MMSE), all test items were divided into the following five cognitive domains: (1) Attention: Chinese version of the Wechsler Adult Intelligence Test (WAIS-RC) numerical breadth parallax score test [3]. (2) Memory: verbal memory was measured using the WHO-UCLA Auditory Verbal Learning Test (WHO-UCLA AVLT) [4]; visual memory was measured using the simplified Rey Complex Graphical Memory Test [5]. (3) Executive functions: control of distractions was measured using the brief Stroop test (24 items, 4 colors) distractions section (Part C) [6]; thinking flexibility was measured using the Semantic Categorization Fluency Test (animals) [6]; planning and logical abilities were measured using the WAIS-RC Picture Arrangement subtest (1, 3, 5, 7 items) [3]; concept formation and transformation abilities were measured using the California Card Sorting Test [7]; abstract generalization ability using the WAIS-RC Similarity subtest (1, 2, 3, 4 items) [3]; and working memory using the WAIS-RC Digit Breadth Backward Recitation subtest [3]. (4) Information processing speed: WAIS-RC Digit Symbol subtest [3] and Stroop test color block section (Part A) [6]. (5) Visual-spatial structure skills: brief Rey complex figure copying [5], WAIS-RC block subtest (items 3, 4, 6, 7) [3] and clock drawing test [8].
III.Statistical methods
SPSS 11.5 software was used for analysis. An abnormality criterion of 1.5 standard deviations below the normal control mean was used.
Results
Table 2 Comparison of patients’ cognitive test results and normal control means
Cognitive test
Example 1
Example 2
Case 3
Example 4
Example 5
Example 6
Example 7
Example 8
Normal control
MMSE
21*
25*
28
21*
25*
27
26
27
28.83 (1.06)
Attention.
Number breadth parsimonious
8
7
8
7
7
5*
8
7
7.51 (0.87)
Verbal memory (WHO-UCLA AVLT).
Immediate recall (five times average)
5.2*
4.4*
4.6*
6.2*
5.6*
6.0*
8*
9*
11.26(1.12)
Short-time delay recall (3 m)
0*
2*
4*
2*
1*
2*
11
12
13.41 (1.36)
Long-time delayed recall (30 m)
0*
0*
3*
2*
2*
5*
8*
9*
13.21 (1.17)
Recertification (hit-misstatement)
5*
1*
9*
10*
9*
7*
11*
12
13.98 (1.05)
Visual memory (Rey graphics).
Immediate memory
2*
11
13
10
11
10
11
10
12.48 (1.90)
Delayed recall (30 m)
0*
11
9
8*
11
8*
11
9
12.12 (1.97)
Execution function.
Stroop Quiz C Error Response
5*
13*
3
5*/
6*
3
3
4
2.30 (1.72)
Semantic classification fluency (animals)
5*
14.00
11.00*
7*
10*
14
14
16
18.52 (3.47)
Image arrangement
4*
8
16
8
10
12
12
11
11.58 (2.99)
California Card Sort
4
2*
8
6
4
6
6
6
6.42 (1.18)
Digital breadth backwards
4
3*
5
3*
4
4
3*
4
4.68 (0.93)
Information processing speed.
Numeric symbols
21
21
12*
24
26
37
20
19
33.81 (9.46)
Stroop test A time(S)
30*
24
18
27*
25
25
20
22
18.24 (4.34)
Visual-spatial structure skills.
Rey graphic copying
15
13
16
14
15
15
14
13
14.63 (1.07)
Building block quiz
8*
8*
16
16
16
12
12
14
15.12 (2.43)
Note: * 1.5 standard deviations below the normal mean.
The MMSE was lower than normal controls in 4 of the 6 patients with left anterior thalamic nucleus stroke (cases 1, 2, 4, 5). 6 patients had severe verbal memory deficits, with more severe decline in delayed recall. 3 patients (cases 1, 4, 6) also had graphic memory involvement, but overall, to a lesser extent than verbal memory. Four patients (cases 1, 2, 4, and 5) had significantly worse scores than normal controls on several executive function tests, and one patient in case 3 had abnormalities on one executive function test. Abnormalities in information processing speed were seen in three patients (cases 1, 3, and 4), and two patients (cases 1 and 2) had decreased visuospatial structure skills. Taken together, a total of 5 patients (cases 1, 2, 3, 4, and 5) showed impairment in 2 or more cognitive domains (Table 2).
Two patients with right anterior thalamic nucleus stroke had normal MMSE scores, only mild impairment in verbal memory, normal graphic memory, and mild impairment in case 7 with digit breadth backwards (Table 2).
Discussion
In the present study, all 6 patients with left anterior thalamic nucleus stroke had memory impairment, disorientation, and unresponsiveness in higher cortical functions as the starting symptoms, and 2 had mental behavior abnormalities such as apathy and lack of self-knowledge, and only 1 had physical weakness; after 3 months of review, the cognitive impairment and mental behavior abnormalities persisted, and objective cognitive assessment confirmed the presence of 2 or more cognitive domains in 5 patients. abnormalities. These findings suggest that damage to the left anterior thalamic nucleus, a key site of memory and cognition, can lead to persistent and severe cognitive decline, and that patients may lack positive signs of sensory or motor systems. Other national and international studies have also suggested that left-sided thalamic lesions can lead to lasting cognitive impairment [2,9].
The thalamus is the subcortical center and relay station for various sensory (except olfactory) transmissions and exerts important influence on the activities of the motor system, sensory system, limbic system, superior reticular system, and cerebral cortex. The thalamus has mainly anterior, medial, and lateral nuclei clusters. The anterior thalamic nucleus is a relay station of the limbic system, receiving fibers from the papillary body of the thalamus and sending fibers to the cingulate gyrus, participating in the formation of the Papez loop (hippocampus → fornix → papillary body → papillary thalamic tract → anterior thalamic nucleus → cingulate gyrus → hippocampus), which plays an important role in memory and cognition [10]. As in the patients in this study, lesions of the anterior thalamic nucleus can disrupt the integrity of these loops, leading to severe memory deficits, cognitive impairment, and psychobehavioral abnormalities. The six patients in the present study with left-sided thalamic damage had lesions involving the anterior nucleus, which could explain their clinical cognitive symptoms.
In the present study, the anterior thalamic nucleus was also involved in two patients with right-sided thalamic stroke, but the patients showed only mild verbal memory deficits, suggesting that the cognitive impact of right-sided anterior thalamic nucleus stroke is less severe compared to the left side. However, right-sided thalamic strokes have also been reported to cause global amnesia [11,12]. Given the small number of patients with right-sided stroke in this study, the effect of right-sided thalamic stroke on cognition needs to be further investigated.
Regarding the characteristics of cognitive impairment due to right- and left-sided thalamic strokes, some literature reports that left-sided thalamic strokes mainly lead to verbal memory impairment [1,13], whereas right-sided lesions lead to impairment of visual memory or visuospatial function [16], suggesting a lateralization of the processing of verbal and graphic cognitive material at the thalamic level. However, there is still much controversy regarding this hypothesis. Some studies have shown that either left- or right-sided thalamic strokes can lead to global amnesia [16,11], while others suggest that left-sided strokes lead to global amnesia, while right-sided strokes lead to impaired graphic memory [14-15]. In the present study, six patients with left anterior thalamic nucleus stroke had severe verbal memory deficits, and graphic memory was also involved in three patients, one of which was more severe, whereas two patients with right anterior thalamic nucleus stroke had only mild verbal memory deficits and normal graphic memory. This suggests that left anterior thalamic nucleus lesions usually lead to verbal memory deficits and sometimes to global amnesia, whereas graphic memory can be uninvolved in right-sided strokes, so that lateralization of cognition at the thalamic level is not constant.
References (omitted)
Figure 1. Example 3 head MRI: diffusion-weighted phase showing high signal in the left anterior thalamic nucleus.
Figure 2. Example 4 head MRI: T2 scan showing high signal in the left anterior thalamic nucleus.
Figure 3 Example 6 Head CT: high density in the left anterior thalamic nucleus.