Y B Benovitski1, A Lai2, C C McGowan3, O Burns3, V Maxim3, D A X Nayagam4, R Millard3, G D Rathbone3, M A le Chevoir5, R A Williams6, D B Grayden7, C N May8, M Murphy2, W J D'Souza2, M J Cook2, C E Williams3. 1. The Bionics Institute, East Melbourne, Victoria, Australia. Electronic address: ybenovitski@bionicsinstitute.org. 2. Department of Medicine, St. Vincent's Hospital, The University of Melbourne, Melbourne, Victoria, Australia. 3. The Bionics Institute, East Melbourne, Victoria, Australia. 4. The Bionics Institute, East Melbourne, Victoria, Australia; Department of Anatomical Pathology, The University of Melbourne, St Vincent's Hospital, Melbourne, Australia. 5. Faculty of Veterinary and Agricultural Science, The University of Melbourne, Melbourne, Victoria, Australia. 6. Department of Anatomical Pathology, The University of Melbourne, St Vincent's Hospital, Melbourne, Australia. 7. Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, Victoria, Australia; Centre for Neural Engineering, The University of Melbourne, Melbourne, Victoria, Australia. 8. The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Melbourne, Victoria, Australia.
Abstract
OBJECTIVE: Minimally-invasive approaches are needed for long-term reliable Electroencephalography (EEG) recordings to assist with epilepsy diagnosis, investigation and more naturalistic monitoring. This study compared three methods for long-term implantation of sub-scalp EEG electrodes. METHODS: Three types of electrodes (disk, ring, and peg) were fabricated from biocompatible materials and implanted under the scalp in five ambulatory ewes for 3months. Disk electrodes were inserted into sub-pericranial pockets. Ring electrodes were tunneled under the scalp. Peg electrodes were inserted into the skull, close to the dura. EEG was continuously monitored wirelessly. High resolution CT imaging, histopathology, and impedance measurements were used to assess the status of the electrodes at the end of the study. RESULTS: EEG amplitude was larger in the peg compared with the disk and ring electrodes (p<0.05). Similarly, chewing artifacts were lower in the peg electrodes (p<0.05). Electrode impedance increased after long-term implantation particularly for those within the bone (p<0.01). Micro-CT scans indicated that all electrodes stayed within the sub-scalp layers. All pegs remained within the burr holes as implanted with no evidence of extrusion. Eight of 10 disks partially eroded into the bone by 1.0mm from the surface of the skull. The ring arrays remained within the sub-scalp layers close to implantation site. Histology revealed that the electrodes were encapsulated in a thin fibrous tissue adjacent to the pericranium. Overlying this was a loose connective layer and scalp. Erosion into the bone occurred under the rim of the sub-pericranial disk electrodes. CONCLUSIONS: The results indicate that the peg electrodes provided high quality EEG, mechanical stability, and lower chewing artifact. Whereas, ring electrode arrays tunneled under the scalp enable minimal surgical techniques to be used for implantation and removal.
OBJECTIVE: Minimally-invasive approaches are needed for long-term reliable Electroencephalography (EEG) recordings to assist with epilepsy diagnosis, investigation and more naturalistic monitoring. This study compared three methods for long-term implantation of sub-scalp EEG electrodes. METHODS: Three types of electrodes (disk, ring, and peg) were fabricated from biocompatible materials and implanted under the scalp in five ambulatory ewes for 3months. Disk electrodes were inserted into sub-pericranial pockets. Ring electrodes were tunneled under the scalp. Peg electrodes were inserted into the skull, close to the dura. EEG was continuously monitored wirelessly. High resolution CT imaging, histopathology, and impedance measurements were used to assess the status of the electrodes at the end of the study. RESULTS: EEG amplitude was larger in the peg compared with the disk and ring electrodes (p<0.05). Similarly, chewing artifacts were lower in the peg electrodes (p<0.05). Electrode impedance increased after long-term implantation particularly for those within the bone (p<0.01). Micro-CT scans indicated that all electrodes stayed within the sub-scalp layers. All pegs remained within the burr holes as implanted with no evidence of extrusion. Eight of 10 disks partially eroded into the bone by 1.0mm from the surface of the skull. The ring arrays remained within the sub-scalp layers close to implantation site. Histology revealed that the electrodes were encapsulated in a thin fibrous tissue adjacent to the pericranium. Overlying this was a loose connective layer and scalp. Erosion into the bone occurred under the rim of the sub-pericranial disk electrodes. CONCLUSIONS: The results indicate that the peg electrodes provided high quality EEG, mechanical stability, and lower chewing artifact. Whereas, ring electrode arrays tunneled under the scalp enable minimal surgical techniques to be used for implantation and removal.
Authors: Jens P Dreier; Sebastian Major; Coline L Lemale; Vasilis Kola; Clemens Reiffurth; Karl Schoknecht; Nils Hecht; Jed A Hartings; Johannes Woitzik Journal: Front Neurosci Date: 2019-04-24 Impact factor: 4.677