DBS in STN and macrorecording using electrodes of stimulation: what can be done and where we are?

Damien Debatisse(1), Etienne Pralong(1), Claudio Pollo(2), Gregoire Waljers(3), Jocelyne Bloch(2), Marie-Hélène Tétreault(1), Jean-Guy Villemure(2).

(1)NCH-UNN-(2)Neurosurgery Dpt- (3)EPFL CHUV Lausanne,

Switzerland

14th Meeting of the World Society for Stereotactic and Functional NeurosurgeryRome, 13-17 June 2005

To validate a localization technique of the DBS electrode in the subthalamic nucleus (STN) based on the analysis of the electrophysiological signal recorded through the DBS contacts before electrode internalization.

Today, surgical approaches in Parkinson’s disease are commonly used around the world. They may improve patient’s comfort or even lead to a “relapse” in parkinsonians that did not previously respond to traditional pharmacological medicine. Deep brain stimulation (DBS) electrodes target localization can be performed with the help of microrecordings, and/or physiological response and/or neuronavigation. The method of choice depends strongly on the surgical team know-how.

1. Introduction:

2. objective:

3. Méthods: The trajectory was chosen using a standard procedure. Electrode entry-point was chosen 3 mm in front of the coronal

suture and 3 cm lateral to the midline plane. Trajectory end point was chosen at the infero-lateral part of the subthalamic region as visualized on an inverse recovery IRM plane orthogonal to the AC-PC line and passing 3 mm behind the AC-PC mid point. Electrode tracks traversed the anterior nuclei of the thalamus, passed through the white matter tracts of the thalamic fasciculus, the zone incerta and lenticular fasciculus before entering the STN (Fig.1).

3. Data acquisition was performed on 7 patients (4 males/3 females, 72 ± 8 year-old).4. Recordings were performed using the DBS electrode contacts and scalp electrodes (right, left or both) (Fig.2). 5. Signals were recorded using a Micromed ® (Italy) 32 channels system at 512 Hz, low passed filtered at 128 Hz and high

passed filtered at 1 Hz. 6. The signal was visualized using a monopolar montage or an averaged reference (all derivations or DBS derivation only)

(Fig 4). 7. Somatosensory potentials (SEP) were performed on the median nerve during DBS electrode lowering to the STN, Off line

analysis was performed using linear and temporal techniques (wavelet and FFT) with EEimagine ® software from ANT ® (Germany) (Fig5).

4. Résuls:

EEG data analysis on the intracerebral (IN) and scalp electrodes (OUT) using FFT, wavelet and phases reveals statistically significant (t < 0.05) in all cases in term of phases, frequencies and synchronization between the IN and the OUT derivations. On the other hand, OUT electrodes signal was correlated. SEP (4 cases) analysis demonstrate phase opposition between the upper (0-1) and the lower (1-2; 2-3) electrode contacts on both sides.

This study confirms 1) the possibility to record electrophysiological signal from DBS electrode contacts during Parkinson’s disease surgery). 2) The presence of signal variations between the DBS contacts and between the DBS and scalp derivations representing a localization signature of DBS contacts. 3) The possibility to record SEP responses through the DBS electrodes. In conclusion, we believe that on line signal acquisition/analysis during DBS electrode placement can help to optimize STN localization. Such encouraging results should be confirmed by prospective studies comparing radiological and clinical outcomes in the future.

Target Localisation

Trajectory to the STN

Electrode entry-point:3 mm in front of the coronal suture and 3 cm lateral to the midline plane

TargetInfero-lateral part of the subthalamic region as visualized on an inverse recovery IRM plane orthogonal to the AC-PC line and passing 3 mm behind the AC-PC mid point.

Electrode tracks Anterior nuclei of the thalamus

Passed through the white matter tracts of the thalamic fasciculusthe zone incertalenticular fasciculus

STN

Eventually the SNr

STN QI = 0.4

Clinical good effect

EEG:F4

EEG:F3

EEG:P4

EEG:P3

Ref et Ground

Plot 0Plot 1Plot 2Plot 3

Plot 0Plot 1Plot 2Plot 3

Macrorecording IN et OUT

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RH

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Bipolar Plots

Fig.1) Fig.2) Recordings were performed using the DBS electrode contacts and scalp electrodes (right, left or both)

Fig 3) Microrecording: electrode tracks traversed the anterior nuclei of the thalamus, passed through the white matter tracts of the thalamic fasciculus, the zone incerta and lenticular fasciculus before entering

the STN

Fig.4) Signals were recorded using a Micromed ® (Italy) 32 channels system at 512 Hz, low passed filtered at 128 Hz and high passed filtered at 1 Hz. The signal was visualized using a monopolar montage or an averaged reference

(all derivations or DBS derivation only)

Fig.5) Somatosensory potentials (SEP) were performed on the median nerve during DBS electrode lowering to the STN, Off line analysis was performed using linear and temporal techniques (wavelet and FFT) with EEimagine ® software from ANT ® (Germany).

EPs IN-OUT for Left Median Stimulation EPs IN-OUT for Right Median Stimulation EPs IN only on bipolar PLOTS for Right Median Stimulation

5.Discussion and Conclusion: