Utility of temporally-extended signal space separation algorithm for magnetic noise from vagal nerve stimulators.
OBJECTIVE
To evaluate the utility of a temporally-extended signal space separation algorithm (tSSS) for patients with vagal nerve stimulator (VNS).


METHODS
We evaluated median nerve somatosensory evoked responses (SER) of magnetoencephalography (MEG) in 27 VNS patients (48 sides) with/without tSSS processing. We classified SER dipoles as 'acceptable' if: (A) the location of the dipole was in the expected location in the central sulcus, and (B) the goodness of fit value (GOF) was greater than 80%. We evaluated (1) the number of sides which produced acceptable dipoles in each dataset (i.e. with/without tSSS processing), and in cases where the both data produced reliable dipoles, (2) compared their GOFs and the 95% confidence volumes (CV) (mm(3)). Statistical differences in the GOF and CV between with/without tSSS conditions were determined by paired t test.


RESULTS
Only 11 (23%) responses had reliable dipoles without tSSS processing, while all 48 (100%) had acceptable dipoles under tSSS processing. Additionally, the latter group had significantly higher GOF (increased by 7% on average) and lower CV (mean decrease of 200 mm(3)) than the former (p<0.01).


CONCLUSIONS
Processing with tSSS quantitatively improves dipole fitting of known sources in VNS patients.


CONCLUSIONS
This algorithm permits satisfactory MEG testing in the relatively commonly encountered epilepsy patient with VNS.
Epilepsy Center, Department of Neurology, The Cleveland Clinic, Cleveland, OH 44195, USA.
Yosuke
Y
Kakisaka
John C
JC
Mosher
Zhong I
ZI
Wang
Kazutaka
K
Jin
Anne-Sophie
AS
Dubarry
Andreas V
AV
Alexopoulos
Richard C
RC
Burgess
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000465:Algorithms; D001931:Brain Mapping; D002648:Child; D004827:Epilepsy / Q000628:therapy*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology; D009622:Noise; D012815:Signal Processing, Computer-Assisted; D055536:Vagus Nerve Stimulation / Q000379:methods*; D055815:Young Adult