Somatosensory cortical plasticity after toe-to-index transfer Hikmat Hadoush a , Toru Sunagawa a , Kazuyoshi Nakanishi b and Mitsuo Ochi b We quantified and compared neuroimaging data and behavioral data (cortical plasticity and hand sensibility, respectively) from a patient who underwent toe-to-index transplantation. Magnetoencephalographic (MEG) recordings of somatosensory-evoked fields (SEFs) response to mechanical tactile stimulation of the index and little fingers of both hands were obtained in parallel with a hand sensibility test from the patient at multiple sessions (week 4, 12, and 24 after the operation). Cortical plasticity refers to SEFs’ latency, dipole strength, and primary somatosensory representation, and the Euclidean distance between primary somatosensory representations of the index and the little fingers. Hand sensibility refers to a patient’s conscious perception of tactile stimulation applied to the transplanted index finger and scored by Semmes-Weinstein monofilaments. SEFs recordings from six healthy participants at one session were used for comparative purposes. At week 4, although the patient had no conscious perception in the left transplanted index to tactile stimulation, SEFs were recorded in response to tactile stimulation. At weeks 12 and 24, the Euclidean distance between primary somatosensory representations of the transplanted index and little fingers increased, together with SEFs dipole strength, whereas SEFs latencies decreased. These occurred in parallel to improvement in hand sensibility. Primary somatosensory representations of the index and little fingers of the patient’s intact right hand were similar to those of the healthy participants’ right hand, indicating the consistency of MEG recording during the follow-up sessions. In conclusion, a combination of neuroimaging and behavioral data may be essential for better assessment of functional recovery after a toe-to-digit operation because the cortical recovery observed by MEG preceded that of hand sensibility observed clinically. NeuroReport 23:1000–1005  c 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins. NeuroReport 2012, 23:1000–1005 Keywords: magnetoencephalography, primary somatosensory cortex, Semmes-Weinstein monofilaments, toe-to-index a Graduate School of Health Sciences and b Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan Correspondence to Toru Sunagawa MD, PhD, Graduate School of Health Sciences, Hiroshima University, 1-2-3 Kasumi, 734-8551 Hiroshima, Japan Tel/fax: + 81 82 257 5457; e-mail: torusuna@hiroshima-u.ac.jp Received 9 August 2012 accepted 12 September 2012 Introduction Nerve regeneration and functional recovery following nerve repair are important aspects for clinical neurology. Toe-to-digit transplantation appears to be an excellent model to study peripheral regeneration and cortical reorganization [1]. Using this model, many neuroimaging studies have examined cortical reorganization of the transferred toe-to-hand in the primary somatosensory cortex [1,2], reporting that cortical reorganization of the transplanted digit may play an essential role in good functional recovery. The functional recovery after toe-to-hand transplantation is commonly evaluated using the hand sensibility test, which is a behavioral sensory test that scores the conscious perception of tactile stimulation using Semmes-Weinstein monofilaments [3]. Previous toe-to- digit or digit-to-digit studies [1,2,4–6] did not show a relationship between recovery in the hand sensibility (perception) and recovery in the primary somatosensory cortex as the concurrent assessment of behavior data and neuroimaging data was lacking. In addition, their studies had been carried out months or years after the surgical repair and after the patients consciously detected or perceived the tactile stimulation; therefore, little is known about the behavior sensory function and somato- sensory cortical plastic changes in the initial phase of recovery (e.g. 4 weeks after the operation). Moreover, these studies examined cortical plasticity of the involved hand only, showing no evidence for the stability of their neuroimaging data. Therefore, the aim of this study was to quantify and compare behavioral data and neuroimaging data (cortical plasticity and hand sensibility, respectively) from a patient who underwent toe-to-index transplanta- tion at three phases of nerve regeneration (early, mid- way, complete; 4, 12, 24 weeks after the operation, respectively). Materials and methods Participants We report data from a 43-year-old male patient (right handed) who underwent a successful toe-to-index transplantation (after 4 weeks of injury) in his left (nondominant) hand, and from six healthy members of our lab (two women, four men, 22–30 years old, all right handed). All clinical evaluations and recordings were approved by the ethics committee of Graduate School of Health Sciences, Hiroshima University. 1000 Somatosensory systems, pain 0959-4965  c 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI: 10.1097/WNR.0b013e32835a649e Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.