Increased Connectivity of Thalamocortical Tract/Occipital Cortex Concurrent with Recovery of Impaired Consciousness in a Stroke Patient: A Diffusion Tensor Tractography Study: A Case Report

Background: Little has been reported about the role of the occipital cortex in the recovery from impaired consciousness. In this case report, we report on a stroke patient who showed increased connectivity of the thalamocortical tract (TCT), including the occipital cortex, on follow-up diffusion tensor tractography (DTT) that was concurrent with recovery of impaired consciousness. Case presentation: A 64-year-old male patient underwent craniectomy and hematoma removal for spontaneous intracerebral hemorrhage (ICH) in the left fronto-parieto-temporal lobes and extraventricular catheterization for intraventricular hemorrhage (IVH). When he started rehabilitation eight weeks after onset, he was in a minimally conscious state with a Coma Recovery Scale-Revised (CRS-R) score of 14. On 8-week DTT, decreased connectivity of the TCT between the thalamic intralaminar nuclei and the cerebral cortex was observed in both medial prefrontal cortices (mPFCs), the occipital cortex, and the left parietal cortex. By contrast, on 12-week DTT, TCT connectivity had increased to include both medial prefrontal cortices and the right occipital cortex. Conclusion: Increased neural connectivity of the TCT to the mPFC and the occipital cortex, as shown by DTT, contributed to the recovery of impaired consciousness in a stroke patient. The results suggest that increased neural connectivity to the occipital cortex might contribute to the recovery of impaired consciousness in stroke patients.

The Usefulness of Diffusion Tensor Tractography in Diagnosing Neuropathic Pain: A Narrative Review

Diffusion tensor tractography (DTT) is derived from diffusion tensor imaging. It has allowed visualization and estimation of neural tract injury, which may be associated with the pathogenesis of neuropathic pain (NP). The aim of the present study was to review DTT studies that demonstrated the relationship between neural injuries and NP and to describe the potential use of DTT in the evaluation of neural injuries that are involved in the pathophysiological process of NP. A PubMed search was conducted for articles published until July 3, 2020, which used DTT to investigate the association between neural injuries and NP. The key search phrase for identifying potentially relevant articles was (diffusion tensor tractography AND pain). The following inclusion criteria were applied for article selection: (1) studies involving patients with NP and (2) studies in which DTT was applied for the evaluation of NP. Review articles were excluded. Altogether, 108 potentially relevant articles were identified. After reading the titles and abstracts and assessment of eligibility based on the full-text articles, 46 publications were finally included in our review. The results of the included studies suggested that DTT may be beneficial in identifying the pathophysiological mechanism of NP of various origins including central pain caused by brain injuries, trigeminal neuralgia, sciatica, and some types of headache. Further studies are needed to validate the efficacy of DTT in investigating the pathophysiology of other types of NP.