Increased thalamocortical connectivity from the affected thalamus to the unaffected hemisphere in a stroke patient

Consciousness is controlled by complicated actions of various neural structures (Schiff, 2010; Long et al., 2016). The thalamocortical connections between the central thalamus and cerebral cortex are considered an important neural structure for consciousness (Laureys et al., 2000; Schiff, 2010; Jang and Lee, 2015). Here, we report a patient who revealed increased thalamocortical connectivity from the affected thalamus to the unaffected hemisphere through interthalamic adhesion.

A 79-year-old right-handed female underwent decompressive craniectomy for brain swelling due to infarction in the right intracerebral artery territory. At 10 weeks after onset when she started rehabilitation, brain MRI showed a leukomalatic lesion in the right fronto-parieto-occipito-temporal lobes, subcortical white mater, and midbrain (Figure 1A). The patient showed a vegetative state, with a Glasgow Coma Scale score of 6 (eye opening: 1, best verbal response: 1, and best motor response: 4) (full score: 15), Coma Recovery Scale-Revised score of 3 (auditory: 0, visual: 0, motor: 2, verbal: 1, communication: 0, and arousal: 0) (full score: 23), Mini-Mental State Examination score of non-checkable (full score: 30), Functional Ambulation Category score of 0 (full score: 5) and Motricity Index score of 21 (right extremities), and 14 (left extremities) (full score: 100) (Teasdale and Jennett, 1974; Folstein et al., 1975; Demeurisse et al., 1980; Cunha et al., 2002; Giacino et al., 2004). The patient provided signed informed consent. This study was conducted retrospectively, and approval for the study was obtained from the Institutional Review Board of Yeungnam University Hospital (approval No. YUMC-2019-06-032) on June 21, 2019.

Diffusion tensor imaging was obtained at 10 weeks after onset using a 6-channel head coil on a 1.5 T Philips Gyroscan Intera. Fiber tracking was conducted using Functional Magnetic Resonance Imaging of the Brain Diffusion Software with routine options (0.5 mm step lengths, 5000 streamline samples, curvature thresholds: 0.2). Two parts of the ascending reticular activating system (ARAS) were analyzed by the following regions of interest (ROI): the lower dorsal ARAS between the reticular formation of the pons (RF, seed ROI) and the intralaminar nuclei of the thalamus (ILN, target ROI) (Yeo et al., 2013), after which the thalamocortical connections between the ILN [seed ROI] and the cerebral cortex were reconstructed (Jang et al., 2014).

The right lower dorsal ARAS showed narrowing and the majority of the right thalamocortical connections were connected to the left hemisphere via the interthalamic adhesion (Figure 1B).

Figure 1 DTT and MRI for a 79-year-old female patient with infarction in the right intracerebral artery territory.

In this patient, DTT revealed that the majority of the thalamocortical connections between the ILN and the cerebral cortex in the right (affected) hemisphere were connected from the right thalamus to the left (unaffected) hemisphere through the interthalamic adhesion in a stroke patient. The central thalamus is a core structure of consciousness because it directly links to the cerebral cortex, brainstem and basal forebrain, and indirectly links to the cortico-basal ganglia-thalamo-cortical loop system (Schiff, 2010). It appears that the increased thalamocortical connections from the thalamic ILN of the affected hemisphere to the unaffected hemisphere in this patient might be a compensatory phenomenon to the severe damage of the affected hemisphere. A thalamus is connected to an opposite thalamus through the interthalamic adhesion. Many studies using DTT have demonstrated the thalamocortical connections between the ILN and the cerebral cortex in normal subjects and patients with recovery of injured thalamocortical connections following brain injury (Jang et al., 2014; Jang and Kwon, 2019). However, the phenomenon that the thalamocortical connections from the thalamic ILN to the opposite hemisphere has not been clarified in patients with disorders of consciousness as well as normal subjects (Jang et al., 2014; Jang and Kwon, 2019). Therefore, further studies on the anatomy and function of the thalamocortical connections from the thalamic ILN to the opposite hemisphere in both normal and pathologic conditions should be warranted.

Sung Ho Jang, You Sung Seo, Sung Jun Lee＊

Department of Physical Medicine and Rehabilitation, College of Medicine, Yeungnam University, Daegu, Republic of Korea

＊Correspondence to:Sung Jun Lee, BS, hssj8020@hanmail.net.

orcid:0000-0001-5094-8199 (Sung Jun Lee)

Received:May 29, 2019

Peer review started:June 3, 2019

Accepted:November 20, 2019

Published online:January 31, 2020

doi:10.4103/1673-5374.274350

Author contributions:Study conception, design, and supervision: SHJ. Image drafting and revision: YSS and SJL. Critical revision of manuscript for intellectual content: SJL. All authors approved the final version of this manuscript.

Conflicts of interest:The authors declare that they have no competing interests.

Financial support:This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIP) (No. 2018R1A2B6000996; to SHJ).

Institutional review board statement:Approval for the study was obtained from the Institutional Review Board of Yeungnam University Hospital (approval No. YUMC-2019-06-032) on June 21, 2019.

Declaration of participant consent:The authors certify that they have obtained the appropriate participant consent form. In the forms, the participants have given their consent for their images and other clinical information to be reported in the journal. The participants understand that their names and initials will not be published and due efforts will be made to conceal his identity.

Reporting statement:This study follows the Recommendations for the Conduct, Reporting, Editing and Publication of Scholarly Work in Medical Journals developed by the International Committee of Medical Journal Editors.

Biostatistics statement:No statistical method was used in this study.

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Data sharing statement:Datasets analyzed during the current study are available from the corresponding author on reasonable request.

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Peer review:Externally peer reviewed.

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