128-channel somatosensory evoked potentials in the differential diagnosis of parkinsonian disorders.

Purpose: The differential diagnosis of parkinsonian disorders can be very difficult, especially at an early stage. In this study, we investigated whether SEP amplitude recorded by 128-channel EEG is useful for diagnosis of parkinsonian disorders, and in particular whether SEP asymmetry can differentiate corticobasal degeneration (CBGD) from other parkinsonian disorders.

Methods: We recorded median nerve SEPs in 47 patients suspected of CBGD, supranuclear palsy or definite Parkinson's disease at an early stage.

Multichannel recording of tibial-nerve somatosensory evoked potentials.

Study Aims: The topography of the peaks of tibial-nerve somatosensory evoked potential (SEP) varies among healthy subjects, most likely because of differences in position and orientation of their cortical generator(s). Therefore, amplitude estimation with a standard one- or two-channel derivation is likely to be inaccurate and might partly cause the low sensitivity of SEP amplitude to pathological changes. In this study, we investigate whether 128-channel tibial-nerve SEP recordings can improve amplitude estimation and reduce the coefficient of variation.

Quantifying interhemispheric symmetry of somatosensory evoked potentials with the intraclass correlation coefficient.

Although large intersubject variability is reported for cortical somatosensory evoked potentials (SEPs), variability between hemispheres within one subject is thought to be small. Therefore, interhemispheric comparison of SEP waveforms might be clinically useful to detect unilateral abnormalities in cortical sensory processing. We developed and evaluated a new technique to quantify interhemispheric SEP symmetry that uses a time interval including multiple SEP components, measures similarity of SEP waveforms between both hemispheres and results in high symmetry values even in the presence of small interhemispheric anatomic differences.

Multichannel recording of median nerve somatosensory evoked potentials.

Objectives: Clinical applications of multichannel (>or=64 electrodes) electroencephalography (EEG) have been limited so far. Amplitude variability of evoked potentials in healthy subjects is large, which limits their diagnostic applicability. This amplitude variability may be partially due to spatial undersampling of anatomical variations in cortical generators.