Guide
The thalamus is part of the diencephalon and functions as a transit center between the cortex and the subcortical region of the brain, also playing an important role in regulating arousal and levels of consciousness. Lesions of different blood vessels in the thalamus can lead to different thalamus infarction syndromes, and the clinical and imaging manifestations of infarction in common parts of the thalamus are sorted out in this paper through the form of graphic and text combination.
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<h1>Overview of the characteristics of thalamus blood supply</h1>
Different parts of the thalamus obtain blood supply from the anterior and posterior circulation, respectively. The parathalamus midal artery (or penetrating artery) usually comes from the anterior circulation and supplies blood to the anterior and lower parts of the thalamus and midbrain; the blood vessels from the posterior circulation supply blood to the rest of the thalamus, the medial side of the thalamus and midbrain is fed by branches from the P1 segment of the posterior cerebral artery (PCA), and the lateral and upper sides and upper of the thalamus are fed by the P2 segment branches (Figures 1, 2).
Fig. 1 Blood supply arteries of the thalamus
Fig. 2 Lateral view (A) and dorsal view (B) showing major thalamus supply arteries and nuclei
<h1>Thalamus infarction and clinical syndrome</h1>
Anterior thalamus infarction
The anterior thalamus region is fed by a thalamus nodule artery that originates 1/3 of the middle of the posterior communication artery, unlike other thalamus artery regions that originate from PCA. The clinical features of infarction at this site are obvious, mainly manifested by severe and extensive neuropsychological defects.
Early infarction in this area may show varying degrees of altered levels of consciousness and taciturnity, while persistent personality changes are seen in the later stages of the disease, including temporal and spatial localization disorders, apathy, lack of self-awareness, etc., and emotional disorders may be obvious. Other common symptoms of anterior thalamus infarction are anterograde memory impairment, as well as aphasia with low-frequency dysphonia and dysarthria.
Fig. 3 Schematic diagram of arterial supply to the thalamus nodule and imaging of infarction
Infarction in the median parathalamic region
This site is fed by a parathalamic mid-artery, which emanates from the P1 segment of the PCA, which has more associated variation and can be divided into 3 categories according to different sites of origin (Figure 4).
➤ Type I: the most common variant of the parathalamic median artery, with bilateral symmetrical vascular origin, and both paracial median arteries originating in the P1 segment of the corresponding PCA.
➤ Type II: This variant is bilaterally asymmetrical and can be divided into two subtypes. Type IIa bilaterally derives blood supply from ipsilateral PCA; type IIb is the so-called Percheron artery, that is, the paranadial middle artery first emanates from unilateral PCA and then splits into two branches, and this single arterial trunk supplies blood to both the bilateral midthalamus and midbrain regions.
➤ Type III: This variant is also bilaterally symmetrical, with bilateral PCA emitting a parathalamic mid-artery and an arched vessel in the middle of the bilateral parathalasmous artery.
Fig. 4 Schematic diagram of variation in the parathalamus median artery
Symptoms of parathalamic mid-artery infarction depend on the type of vascular variation and may be unilateral or bilateral. In patients with unilateral paramitron infarction, the early stages are characterized by decreased levels of excitement and fluctuating levels of consciousness, which can last from hours to days. In the long run, emotional and behavioral changes will still occur, including restlessness, agitation, disorientation, apathy, etc. Left infarction may also present as language dysfunction.
Fig. 5 Schematic diagram of parathalamic mid-middle artery blood supply and imaging of infarction
Bilateral thalamus infarction caused by Percheron arterial occlusion is well understood. This syndrome is relatively rare, accounting for 7% of all ischemic strokes, and typical symptoms include a total of 4 points:
➤ Vigilance disorders, such as coma or stiffness;
➤ Obvious memory impairment, difficult to produce new memories, often fictitious;
➤ Changes in instinct and mood, generally accompanied by irritability, apathy or long-term appearance of bad mood;
➤ Vertical gaze paralysis, which may not have a vertical glance and tracking movements.
Other clinical symptoms include disorientation, confusion, and apathetic mutism. Neurologic disorders and drowsiness can be restored in most patients, but cognitive deficits and apathy tend to be more severe and long-lasting.
Fig. 6 Imaging of infarction in the Percheron arterial blood supply area
Subterternaly thalamus infarction
The inferior lateral thalamus artery, also known as the thalamus-knee artery, originates from the P2 branch of the PCA and is located after the level of the posterior communication artery and consists of a group of small arteries that supply blood to the lateral area of the subthalamus.
Infarction of the inferior lateral artery of the hypothalamus can lead to thalamus syndrome, the most prominent feature being severe pain that cannot be relieved by analgesics may be related to the separation of the thalamus from cortical inhibition. Thalamus pain is often delayed and can occur immediately. About 80% of patients with infarction in this area have this syndrome.
Other symptoms of the syndrome include sensory loss and limb movement disorders. Sensory impairment can involve all types of sensations, but not necessarily all of them in a single patient. Symptoms of sensory loss and weakness hemiplegia are strongly suggestive if the patient presents with symptoms of sensory loss and weakness hemiplegia.
In addition, patients develop pure sensory syndrome (loss of all forms of sensation), especially when symptoms affect the face and arms, which are also highly suggestive of lesions in this area. Some patients with pure sensory syndrome may also present with delayed pain and/or sensory dullness.
Scholars have described a special hand symptom in which the patient's hand is bent and rotated internally, and the thumb is hidden under other fingers, called the thalamus hand, which is also a characteristic manifestation of infarction in this area. At present, patients with infarction at this site have not developed more complex behavioral syndromes, and occasionally there have been reports of language disorders and aphasia.
Fig. 7 Schematic diagram of subthalamic lateral artery blood supply and imaging of infarction
Infarction of the posterior part of the thalamus
This site is fed by the posterior choroidal artery. The retrochoroidal arteries also come from the P2 segment of PCA, which is also composed of a group of small blood vessels. The number of reports of infarction at this site is still limited, and in the existing reports, the most common symptom is quadrant blindness, which may be accompanied by hemiplexation loss, cortical aphasia and memory impairment.
A characteristic manifestation of retrochoroidal artery infarction is eye movement disorders, which are not characteristic of thalamus infarction and are relatively rare. In addition, patients may present with a delayed complex hyperkinesia syndrome, including ataxia, tremor, dystonia, myoclonus, and chorea.
Fig. 8 Schematic diagram of retrochoroidal artery blood supply and imaging of infarction
医脉通编译自：Li S, Kumar Y, Gupta N, et al. Clinical and Neuroimaging Findings in Thalamic Territory Infarctions: A Review[J]. Journal of Neuroimaging, 2018.