Reliability for non-invasive somatosensory cortex localization: Implications for pre-surgical mapping

Jack Solomon; Shaun Boe; Timothy Bardouille

doi:10.1016/j.clineuro.2015.10.001

Reliability for non-invasive somatosensory cortex localization: Implications for pre-surgical mapping

Clin Neurol Neurosurg. 2015 Dec:139:224-9. doi: 10.1016/j.clineuro.2015.10.001. Epub 2015 Oct 9.

Authors

Jack Solomon¹, Shaun Boe², Timothy Bardouille³

Affiliations

¹ Laboratory for Brain Recovery and Function, Dalhousie University, 5869 University Avenue, Halifax, Nova Scotia, Canada B3H 1X7; Department of Psychology and Neuroscience, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia, Canada B3H 4R2. Electronic address: jc347066@dal.ca.
² Laboratory for Brain Recovery and Function, Dalhousie University, 5869 University Avenue, Halifax, Nova Scotia, Canada B3H 1X7; Department of Psychology and Neuroscience, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia, Canada B3H 4R2; School of Physiotherapy, Dalhousie University, 5869 University Avenue, Halifax, Nova Scotia, Canada B3H 1X7. Electronic address: s.boe@dal.ca.
³ Department of Psychology and Neuroscience, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia, Canada B3H 4R2; Biomedical Translational Imaging Centre (BIOTIC), QEII Health Sciences Centre, 3900-1796 Summer Street, Halifax, Nova Scotia, Canada B3H 3A7; School of Physiotherapy, Dalhousie University, 5869 University Avenue, Halifax, Nova Scotia, Canada B3H 1X7. Electronic address: tim.bardouille@dal.ca.

PMID: 26519893
DOI: 10.1016/j.clineuro.2015.10.001

Abstract

Objectives: In patients with epilepsy or space occupying tumors in cortical regions, surgical resection is often considered as the primary treatment. Pre-surgical neuroimaging can provide a detailed map of pathological and functional cortex, leading to safer surgery. Mapping can be achieved non-invasively using magnetoencephalography (MEG), and is concordant with invasive findings. However, the reliability of MEG mapping between sessions is not well established. The inter-session reliability is an important property in pre-surgical mapping to establish resection margins, but repeated scans are impracticable. The present study sought to quantify the intersession reliability of MEG localization of somatosensory cortex (S1).

Patients and methods: Eighteen healthy individuals underwent MEG sessions on 3 consecutive days. Five participants were excluded due to technical issues during one of the three days. Each session included clinical-style S1 localization using electrical stimuli to each median nerve at sub-motor thresholds. The 35 ms peak of the somatosensory evoked field was used for localizing S1 in each session using a single equivalent current dipole model. Intersession reliability was quantified using two methods. Average Euclidean Distance (AED) quantified the difference in localization between each session and the inter-session mean localization. Session Euclidean Distance (SED) quantified the difference in localization between each pair of sessions.

Results and discussion: Results showed the AED was 4.8 ± 1.9 mm, whereas the SED was 8.3 ± 3.4mm. While the AED values obtained parallel those reported previously in smaller samples, the SED values were substantially larger.

Conclusion: Clinicians should consider up to an 8mm confidence interval around the estimated location of S1 based on MEG pre-surgical mapping.

Keywords: Intersession reliability; Magnetoencephalography; Median nerve stimulation; Neurosurgery; Pre-surgical mapping; Somatosensory cortex; Source localization.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adult
Female
Humans
Magnetoencephalography / methods
Magnetoencephalography / standards*
Male
Median Nerve / physiology
Neurosurgical Procedures / methods
Neurosurgical Procedures / standards*
Preoperative Care*
Reproducibility of Results
Somatosensory Cortex / anatomy & histology*
Young Adult