Microelectrode recording: lead point in STN-DBS surgery

Acta Neurochir Suppl (2006) 99: 37 42 # Springer-Verlag 2006 Printed in Austria Microelectrode recording: lead point in STN-DBS surgery M. S. Kim 1, Y. T. Jung 1, J. H. Sim 1,S.J.Kim 2, J. W. Kim 3, and K. J. Burchiel 4 1 Department of Neurosurgery, Inje University Busan Paik Hospital, Busan, Korea 2 Department of Neurology, Inje University Busan Paik Hospital, Busan, Korea 3 Department of Neurology, Dong A University, OHSU, Busan, Korea 4 Department of Neurosurgery, OHSU, Portland, OR, USA Summary Background. Microelectrode recording is an integral part of many surgical procedures for movement disorders. We evaluate the Lead point compared to the NeuroTrek system. We used NeuroTrek in 18 Parkinsonian patients, Lead point-4 in 12 patients, during STN- DBS surgery. We compared MR-Stir image with Microelectrode recording. Method. The MicroGuide system with its integrated screen display provides the user with all the information needed during the surgery on its screen. Microelectrode recordings showed characteristic neuronal discharges on a long trajectory (5 6 mm), intraoperative stimulation induces dramatic improvement of Parkinsonian motor symptoms. Findings. Microrecording data of the Leadpoint showed high background activity, and firing rate of 14 50 Hz. The discharge pattern is typically chaotic, with frequent irregular bursts and pauses. Discussion. The microelectrode recording of the neurotrek and Leadpoint-4 showed unique results of the typical STN spike. The DBS effect is maximized associated by MER mapping. Keywords: Parkinsonian; microelectrode recording; STN-DBS; intraoperative stimulation. Introduction Microelectrode recording is an integral part of many surgical procedures for movement disorder. In the past, clinicians and researchers had to create their own microrecording systems from separately purchased components. This practice resulted in a variety of setups, and many clinical centers are still using these home made systems [16]. Most of the commercially available microrecording devices are Neurotrek (MicroGuide), Lead point 2=Lead point 4, NeuroMap, Guideline system 3000A, Iso-X cell 3þ=Iso Pulsar=micro Targeting, etc [16]. We used the Lead point-4 and Neurotrek (MicroGuide) in STN-DBS surgery of the Parkinsonism. I analysed microelectrode findings in subthalamic nucleus and substania nigra. Materials and methods Eighteen Parkinsonism patients for treatment with neurotrek were enrolled between September, 2001 and August, 2002. in Oregon Health & Sciences University, Portland, OR, USA, and twelve Parkinsonism patients for Lead point-2=4 treatment between November, 2004 and March, 2005 in Busan Paik Hospital, Busan, Korea. Bilateral electrodes were implanted stereotactically under local anesthesia in a single operation. Magnetic resonance imaging (T1, fast spin echo inversion recovery, Stir) was used to determine initial targets. Although there is considerable variation, an approximate target for the central region of the STN nucleus is usually at about 12 mm lateral to the midline, 2 4 mm posterior to the mid-commissural point and 3 mm below the AC-PC line, with Stealth station (Medtronic, Sofamor, Mineapolis, USA) or Gamma-Plan (Elekta, Atlanta, USA). In our procedure, microelectrode recording tracks starts 10 mm above target in the STN. Depending on the 55 60 angle in the sagittal plane, recording usually starts in the thalamic reticular nucleus or in the anterior thalamus Voa, Vop. In this region there are cells with spontaneous burst discharge [13, 14]. The entry into the subthalamic nucleus is apparent when high amplitude spikes with firing rates of 25 45 Hz are found [8]. Tremor cells have also been identified in the human subthalamic nucleus. Since subthalalmic nucleus-like cells may be found in the adjacent, superiorly located zona incerta, the dorsal border of the subthalamic nucleus should be defined by a continuous, cell-dense region, populated by neurons showing movement-related activity [8]. Typically, subthalamic spike is chaotic with frequent irregular bursts and pauses [8]. Below the STN, the substantia nigra, is located whose characteristic features are a high (60 90 Hz) and regular firing rate, but there may be another group with lower rates around 30 Hz [3 5, 7]. The ideal target is defined as one showing clinical benefit and minimal adverse effects after stimulation through the DBS electrode. The position of the Medtronic 3387 quadripolar DBS electrode is chosen so that the 4 electrodes contracts span the 5 6 mm of the subthalamic nucleus [8]. This means that one contact is usually placed in the substantia nigra, two contacts within the subthalamic nucleus, and the superior contact in the zona incerta [8].

38 M. S. Kim et al. Fig. 1. Subthalamic nucleus microelectrode finding in Neurotrek Table 1. Characteristic mean firing rates of subthalamic regions encountered during microelectrode recordings STN mean discharge rate (Hz) STN cells recorded SNr mean discharge rate (Hz) SNr cells Theodosopoulos 34 102 86 6 et al. [17] Hutchison et al. [8] 37 248 71 56 Pidoux et al. [19] 39 45 50 60 Magnin et al. [10] 41 24 Lozano et al. [7] 46 213 Rodriguez et al. [15] 33 200 71 27 Magarinos-Ascone 59 69 190 et al. [9] Kim et al. [our study] 14 52 Gielen FLH [5], described 5 channels tracing of the Lead-point Microelectrode recording and the spikes of the center, lateral, posterior spikes showed excellent view (Figs. 2, 3). Usually, I used 3 5 channels for microelectrode recording. In our study, the mean depth of the subthalamic nucleus was 6 7 mm and our microelectrode recording of the Lead point-4 showed excellent view in center, posterior, laterial, anterior order (Fig. 4). The follow-up is between 6 and 48 months, with a median 28 months. There were no permanent complications from the procedure. Postoperatively, thin section brain CT was checked and DBS location confirmed. Results In our study, the spikes of the subthalamic nucleus showed high-amplitude spikes with firing rates of 14 52 Hz (Fig.1). This is similar to other studies (Table 1). Discussion Bressand et al. [1] showed that there can be remarkable improvement of motor symptoms in Parkinsonism with bilateral deep brain stimulation of the subthalamic nucleus. The most compact of all commercially available microrecording systems is developed and commonly used machine is Microguide. Lead point (Medtronic, Skovlundae, Denmark, and Shoreview, MN) is designed for single and multiple microelectrode recording capable of single-cell isolation and FDA cleared [16].

Lead point in STN-DBS surgery 39 Fig. 2. Subthalamic nucleus microelectrode finding in Lead point 2 The system is delivered in two versions: Lead point 2 accommodates two microelectrodes, and Lead point 4 may simultaneously record from four electrodes, with the fifth electrode being switchable. Lead point 4.0 is available in Europe now, and will soon be available to U.S. users [16]. For microelectrode navigation Lead point uses the microtargeting drive by Frederick Haer & Co. From a nonacademic user point of view, the system is a very good choice because it is compact, easy to use, has good quality of recording=amplification, and is less expensive than its competitors. Another advantage of Lead point is its potential integration with frameless navigation systems that may effectively eliminate the need for multiple instrumentation racks in an already crowded operating room [16]. Anatomic studies have shown somatotopically organized projections to the subthalamic nucleus from various parts of the frontal cortex. An autoradiographic tracer study in macaque monkeys showed motor cortex projections representing the face, arm, and leg arranged lateral to medial within the dorsolateral part of the nucleus [11]. More recently, a study of anterograde tracer injection after intracortical microstimulation mapping in macaque monkeys showed that the facial, forelimb, and hindlimb primary motor cortex projected to the lateral subthalamic nucleus in a lateral to medial arrangement [12]. Similar parts of the supplementary motor area projected in an inverse order into a more medial part of the nucleus [12]. Electrophysiological studies in the normal monkey reveal a predominance of cells responsive to somatosensory examination in the dorsolateral part of the STN [3, 18]. Cells representing the hindlimb are located centrally within this part of the nucleus, whereas forelimb cells are primarily encountered laterally and at the rostral and caudal poles. In a study of Parkinsonian humans undergoing STN surgery, leg-related cells were medial, arm-related cells were lateral, and orofacial cells were located in an intermediate zone [15].

40 M. S. Kim et al. Fig. 3. Continuous microelectrode recording in Lead point 2 Theodosopoulos et al. [17] studied the location of 303 cells during 15 procedures for STN-DBS for Parkinson s disease. The dorsolateral part of the nucleus was the predominant location of the movement-related cells. Within this part of the nucleus, leg- and arm-related cells exhibited different locations. Leg-related cells occupied a relatively central location, whereas arm-related cells tended to populate the lateral part and the rostral and caudal poles of the nucleus. The somatotopic organization of the skeletomotor territory of SNr is unclear. DeLong et al. [2] showed that five of seven arm-related cells recorded in a primate study were located ventrally and posteriorly with respect to orofacial cells. Leg-related activity has not been identified. There is little information on movement-related activity in the human substantia nigra [17]. On a parasagittal approach to the subthalamic nucleus at 55 60 degrees from the AC-PC plane, the typical operative trajectory passes along the anterior part of the thalamus, transverses the zona incerta, enters the subthalamic nucleus, and encounters the substantia nigra past the nucleus s ventral border. Thalamic cells recorded on this trajectory may demonstrate bursting or non bursting patters, with mean discharge rates of 15 19 Hz and 28 19 Hz, respectively [6]. High background activity, frequent multicellular recordings, and firing rates of 30 50 Hz are characteristic of subthalamic nucleus cells [17]. The discharge pattern is typically chaotic, with frequent irregular bursts and pauses [17]. The finding of movement-related activity confirms that the microelectrode is within the dorsolateral subthalamic nucleus, the presumed target area for subthalamic nucleus-deep Brain Stimulation. In our study, the firing rate of 14 50 Hz was seen in subthalamic nucleus and finding of movement related activity of the dorsolateral subthalamic nucleus was checked. Motor symptoms are improved by the micro lesion effect associated with microelectrode recording mapping or DBS lead insertion [17]. In conclusion, the microelectrode recording of Neuro Trek and Lead point showed unique results of the typical subthalamic nucleus spike. Interest in the electrophysiology of the subthalamic nucleus is prompted by

Lead point in STN-DBS surgery 41 Fig. 4. Simultaneous microelectrode recording in STN BEN-GUN its increasing importance in the surgical treatment of Parkinsonism. References 1. Bressand K, Dematteis M, Kahane P, Benazzouz A, Benabid AL (1998) High frequency stimulation of the subthalamic nucleus suppresses absence seizures in the rat: comparison with neurotoxic lesions. Epilepsy Res 31: 39 46 2. DeLong MR, Crutcher MD, Georgopoulos AP (1983) Relations between movement and single cell discharge in the substantia nigra of the behaving monkey. J Neurosci 3: 1599 1606 3. DeLong MR, Crutcher MD, Georgopoulos AP (1985) Primate globus pallidus and subthalamic nucleus: functional organization. J Neurophsiol 53: 530 543 4. DeLong MR, Crutcher MD, Georgopoulos AP (1983) Relations between movement and single cell discharge in the substantia nigra of the behaving monkey. J Neurosci 3: 1599 1606 5. Gielen FLH (2002) Simultaneous microelectrode recordings in STN BEN-GUN therapy and proceeding solution training, pp 23 29 6. Hutchison WD (1998) Neurophysiological identification of the subthalamic nucleus in surgery for Parkinson s disease. Ann Neurol 44: 622 628 7. Hutchison WD, Allan RJ, Opitz H, Levy R, Dostrovsky JO, Lang AE, Lozano M (1998) Neuro-physiologic identification of the subthalamic nucleus in surgery for Parkinson s disease. Ann Neurol 44: 622 628 8. Hutchison WD, Lozano AM (2000) Microelectrode recordings in movement disorder surgery. In: Lozano AM (ed) Movement disorder surgey. Karger, Basel, pp 103 117 9. Magarinos-Ascone C, Riva-Meana C, Figueiras-Mendez R (2000) Neuronal activity in the subthalamic nucleus in Parkinson disease. Rev Neurol 31(1): 66 71 10. Magnin M, Jetzer U, Morel A, Jeanmonod D (2001) Microelectrode recording and macrostimulation in thalamic and subthalamic MRI guided stereotactic surgery. Neurophysiol Clin 31(4): 230 238 11. Monakow KH, Akert K, Kunzle H (1978) Projections of the precentral motor cortex and other cortical areas of the frontal lobe to the subthalamic nucleus in the monkey. Exp Brain Res 33: 395 403 12. Nambu A, Takada M, Tokuno H (1996) Dual somatotopical representations in the primate subthalamic nucleus: evidence for ordered but reversed body-map transformations from the primary motor cortex and the supplementary motor area. J Neurosci 16: 2671 2683 13. Raeva SN, Lukashev A (1993) Unit activity in human thalamic reticularis neurons. II. Activity evoked by significant and nonsignificant verbal or sensory stimuli. Electroenceph Clin Neurophysiol 86: 110 122 14. Racva SN, Lukashev A, Lashin A (1991) Unit activity in human thalamic reticular nucleus. I. Spontaneous activity. Electroenceph Clin Neurophysiol 79: 133 140

42 M. S. Kim et al.: Lead point in STN-DBS surgery 15. Rodriguez MC, Guridi OJ, Alvarez L, Mewesk, Macias R, Vitek J, DeLong MR, Obeso JA (1998) The subthalamic nucleus and tremor in Parkinson s disease. Mov Disord 13 [Suppl] 3: 111 118 16. Slavis KV, Holsapple J (2004) Microelectrode techniques: equipment, components, and system. In: Zvi I, Kim JB (eds) Microelectrode recording in movement disorder surgery. Thieme, New York, pp 14 27 17. Theodosopoulos PV, Marks WJ, Christine C, Starr PA (2003) The locations of movement-related cells in the human Parkinson subthalamic nucleus. Mov Disord 18: 791 798 18. Wichmann T, Bergman H, Delong MR (1994) The primate subthalamic nucleus: I. Functional properties in intact animals. J Neurophysiol 72: 494 506 19. Welter ML, Houeto JL, Bonnet AM, Bejjani PB, Mesnage V, Dormont D, Navarro S, Cornu P, Agid Y, Pidoux B (2004) Effect of high-frequency stimulation on subthalamic neuronal activity in parkinsonian patients. Arch Neurol 61(1): 89 96 Correspondence: Moo Seong Kim, Department of Neurosurgery, Busan Paik Hospital, Kaekeumdong, Jin Koo, Busan 614-735, Korea. e-mail: kinmmo@yahoo.co.kr