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Somatosensory functions are subdivided into two large groups: the elementary somatosensory functions, which consist of light touch, pain, thermal sensation, joint position sense and vibration sense, and the intermediate somatosensory functions, which include two-point discrimination, tactile localisation, weight, texture and shape perception. It is generally accepted that the functional localisation of somatosensory function is the postcentral gyrus, but some researchers suggested that the insula is also involved in somatosensory function.1
Insula is a multimodal area and has a major role as a convergence zone implicated in the coordination between internal and external information through emotional subjective awareness. However, the subregional specificity of somatosensory functions in the insula has not been fully elucidated.2 We experienced three cases of stroke restricted exactly to the subregions of the insula which showed heterogeneous somatosensory dysfunction. For these patients, we performed a close examination of the intermediate somatosensory function, and discussed the relation between the insula and intermediate somatosensory function.
Patients and methods
An 81-year-old, right-handed woman who had difficulty speaking in February 2017 was transferred to our hospital. MRI revealed a lesion in the right middle insula (figure 1A). The symptom improved at the time of hospital arrival and she underwent the best medical treatment. The symptom disappeared on the next day. Intelligence and elementary somatosensory functions were normal. The results of the intermediate somatosensory examinations showed that two-point discrimination, tactile localisation and graphesthesia were significantly impaired.
Contributors MS: planning the study. KaM: acquisition of data, conducting and reporting the work. MS, KaM, KT, YU: interpretation of data and discussion of the results. MS and HT: revising the manuscript critically for important intellectual content. AI, HI, KoM, AS, MA, AN, KeM: the attending physicians of each patient, and indication the relationship with the patients. HT: approval of the version of the manuscript to be published. All authors approved the final version of the manuscript, and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Basic study of the diagnosis of dementia by visual, auditory, tactile stimuli: Study of brain mechanisms by fMRI.
Provenance and peer review Not commissioned; externally peer reviewed.
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