SEPs N30 amplitude in Parkinson's disease and in pharmacologically induced rigidity: relationship with the clinical status

Non-dominant hand movement facilitates the frontal N30 somatosensory evoked potential

Background

Previous literature has shown that the frontal N30 is increased during movement of the hand contralateral to median nerve stimulation. This finding was a result of non-dominant left hand movement in right-handed participants. It is unclear however if the effect depends upon non-dominant hand movement or if this is a generalized phenomenon across the upper-limbs. This study tests the effect of dominant and non-dominant hand movement upon contralateral frontal and parietal somatosensory evoked potentials (SEPs) and further tests if this relationship persists in left hand dominant participants. Median nerve SEPs were elicited from the wrist contralateral to movement in both right hand and left hand dominant participants alternating the movement hand in separate blocks. Participants were required to volitionally squeeze (~ 20% of a maximal voluntary contraction) a pressure-sensitive bulb every ~3 seconds with the hand contralateral to median nerve stimulation. SEPs were continuously collected during the task and individual traces were grouped into time bins relative to movement according to the timing of components of the Bereitschaftspotential. SEPs were then averaged and quantified from both FCZ and CP3/4 scalp electrode sites during both the squeeze task and at rest.

Results

The N30 is facilitated during non-dominant hand movement in both right and left hand dominant individuals. There was no effect for dominant hand movement in either group.

Conclusions

N30 amplitude increase may be a result of altered sensory gating from motor areas known to be specifically active during non-dominant hand movement.

Topographic MN-SSEPs (N18, N20 and N30) might characterize underlying CNS involvements in representative types of cerebral palsy

This study is aimed at constructing the neurophysiological basis for determining the characteristic features of cerebral motor disturbance in representative cerebral palsy (CP) types using topographical S-SEPs technology. Median-nerve stimulated S-SEPs (MN-SSEPs) were examined for 23 patients with four representative types of cerebral palsy: 6 athetotic (including 3 patients due to hypoxic-ischemic encephalopathy (HIE) and 3 to kernicterus), 7 hemiplegic, 5 diplegic and 5 tetraplegic types, and 13 normal controls. In HIE group of athetotic CP, frontal N30 specifically showed severe amplitude reduction or abolishment. In hemiplegic CP, both N20 and N30 on the affected cerebral side tended either to disappear or to be normally evoked at the same time, and their mean amplitudes declined severely. In diplegic CP, the amplitudes of subcortical N18 and parietal N20 were not small but significantly enlarged. N30 amplitude stayed within normal. The reason for this unexpected enlargement of N18 and N20 is unclear, but may be partly due to premature birth which caused abnormally abundant dendritic spine due to absence from perinatal normal spine elimination in the brainstem. In several quadriplegic patients, both N20 and N30 disappeared. The mean amplitude of N30 severely decreased. In conclusion, topographical results of N18, N20 and N30 may basically suggest the underlying involvement of nervous structures in CP according to their representative type.

Amantadine sulfate infusion effect on N30 somatosensory evoked potentials in Parkinson's disease

The purpose of this study was to evaluate the effect of amantadine sulfate infusion on the N30 component of the median nerve short-latency somatosensory evoked potentials (SSEPs) in patients with Parkinson's disease (PD). Twenty patients with advanced PD and severe motor fluctuations received a 6-day course of amantadine sulfate infusion (400 mg/day) plus their usual levodopa medication. Patients were assessed clinically by means of the Unified Parkinson's Disease Rating Scale (UPDRS-III and -IV). SSEPs to median nerve stimulation were recorded from the parietal and frontal regions before and after the 6-day course of amantadine infusion. Mean UPDRS motor score during the ON and OFF phase improved after amantadine infusion, as did motor fluctuations. SSEP changes resulting from amantadine sulfate treatment were observed in the P20-N30 amplitude as follows: Mean P20-N30 amplitudes before and after treatment were 2.15 +/- 1.11 microV and 3.06 +/- 1.19 microV respectively (p = 0.000), whereas mean N30-P40 amplitude increased from 2.7 +/- 1.6 microV to 3.9 +/- 1.3 microV after treatment (p = 0.000). Our results indicate that coincident to its clinical impact, amantadine infusion in patients with PD affects electrophysiologic parameters as well.

Abnormality of N30 somatosensory evoked potentials in Parkinson's disease: a multidisciplinary approach

PURPOSE OF THE STUDY

Assess the N30 component of median nerve somatosensory evoked potentials (SEPs) in patients with Parkinson's disease (PD) and correlate its parameters with the severity of the disease, general cognitive ability and regional cerebral blood flow (rCBF).

PATIENTS AND METHODS

Twenty-three non-demented, non-depressed PD patients (at stage II and III of the disease) and 23 age- and education-matched normal controls were enrolled in the study. SEPs were elicited by median nerve stimulation. PD patients' cognitive ability was assessed by means of: 1) Raven's Colored Progressive Matrices (RCPM); 2) the Test of Non-Verbal Intelligence (TONI-2); and 3) the Wisconsin Card Sorting Test (WCST). The patients' rCBF was evaluated by HMPAO SPECT.

RESULTS

There was no difference between SEP N30 latency in PD patients and controls (P > 0.05). The P20-N30 peak-to-peak amplitude was lower in PD patients bilaterally (P < 0.05), and the amplitude of N30-P40 was lower on the right side only (P < 0.05). A significant increase in the amplitude ratio P14-N20/P20-N30 was observed in PD patients (P < 0.05). The correlation of these findings with the clinical parameters of the disease, and notably motor signs, was not significant. Of the three neuropsychological tests only the RCPM showed a positive relation to right P20-N30 amplitude. Regression analysis between SEP parameters and rCBF showed a correlation of N30 amplitude with blood flow in parietal cortical areas, but not in frontal regions.

Sensory and motor interfering influences on somatosensory evoked potentials

The interfering influences by which the different components of the early somatosensory evoked potentials are modified are reviewed from both neurophysiologic and clinical perspectives. Special consideration is given to the specific differences between sensory and motor interferences. In this context, the specific effect of the mental movement simulation task on the frontal N30 component is discussed in relation to the involvement of this evoked wave as a physiologic index of the dopaminergic motor pathways. Relevant interfering approaches, including concurrent events ranging from tactile stimulation to locomotion, are reviewed and discussed insofar as these data provide insights into the neurophysiologic processes of interaction between competing internal models controlling motor acts and sensory information.

The effect of deep brain stimulation on the frontal N30 component of somatosensory evoked potentials in advanced Parkinson's disease patients

OBJECTIVES

In the present study we investigated whether in advanced Parkinson's disease (PD) patients the frontal component of short somatosensory evoked potentials (SEPs) to median nerve stimulation may be modified by basal ganglia deep brain stimulation (DBS).

METHODS

We recorded the SEPs in 6 PD patients undergoing bilateral functional neurosurgery in the internal globus pallidus (GPi) (4 patients) and in the nucleus subthalamicus (STN) (two patients) during ineffective and effective bilateral BDS. Pre-operatively, the SEPs were also recorded in off therapy and during apomorphine infusion.

RESULTS

From the evaluation of the latency and the amplitude characteristics of the major parietal (N20 and P25) and frontal (N30) components, we observed that whereas the parietal waves did not vary in any condition, the N30 potential showed a remarkable amplitude increase during apomorphine as well as during effective bilateral GPi or STN DBS. Furthermore, after the stimulators were turned off we noticed that the N30 amplitude potential progressively faded almost in parallel with the attenuation of DBS clinical effects.

CONCLUSIONS

Our results lead to the conclusion that the bilateral DBS of both GPi and STN is really effective in producing a selective increase of frontal N30 amplitude probably improving the supplementary motor area functional activity, but these results do not clarify whether this amelioration is due to a central or a 'long loop' mechanism.