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Stereotactic imaging of the pallidal target
Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
2002 (English)In: Movement Disorders, ISSN 0885-3185, E-ISSN 1531-8257, Vol. 17, no suppl 3, S130-S134 p.Article in journal (Refereed) Published
Abstract [en]

In 48 consecutive patients, we applied a new stereotactic imaging technique to individually visualize the pallidal target before surgery. A turbo spin-echo proton density sequence (acquisition time, 6 minutes 5 seconds) was used for 2-mm-thick contiguous axial scanning. Pallidocapsular border, medial putaminal border, and optic tract were visualized bilaterally in all patients. Boundaries of globus pallidus internus, globus pallidus externus, and lamina medullaris interna were clearly visualised in 71% of the patients. The anatomic target point was chosen in the middle of the visualized posteroventral pallidum, irrespective of the position of this point in relation to commissures. The lateralities of pallidocapsular border, lamina medullaris interna, and medial boundary of putamen were measured bilaterally in each patient, and the width of the posteroventral pallidum was assessed. The laterality of structures (measured from a point 2 mm anterior to midcommissural point and at a level 2-4 mm below anterior commissure-posterior commissure line) showed a wide range. The position of the pallidocapsular border varied by up to almost 1 cm between the most medial and the most lateral one. There were also variations in the position of the pallidal structures between left and right hemispheres in the same patients. The posteroventral pallidum was slightly more wide on the left than the right side. Given the significant inter- and intra-individual variabilities of the position of pallidal structures, it may be hazardous to rely solely on the atlas and the commissures for targeting. A magnetic resonance imaging sequence that enables visualization in each individual patient of the target area and its surroundings may contribute to less electrode passes during intraoperative physiological exploration and to more exact location of the lesion or chronic electrode in the posteroventral pallidum.

Place, publisher, year, edition, pages
2002. Vol. 17, no suppl 3, S130-S134 p.
Keyword [en]
deep brain stimulation;Parkinson's disease;MRI;stereotactic surgery;pallidum
National Category
URN: urn:nbn:se:umu:diva-55146DOI: 10.1002/mds.10154PubMedID: 11948767OAI: diva2:525729
Available from: 2012-05-09 Created: 2012-05-09 Last updated: 2012-05-16Bibliographically approved
In thesis
1. Stereotactic imaging in functional neurosurgery
Open this publication in new window or tab >>Stereotactic imaging in functional neurosurgery
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: The birth of stereotactic functional neurosurgery in 1947 was to a great extent dependent on the development of ventriculography. The last decades have witnessed a renaissance of functional stereotactic neurosurgery in the treatment of patients with movement disorders. Initially, these procedures were largely based on the same imaging technique that had been used since the birth of this technique, and that is still used in some centers. The introduction of new imaging modalities such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) provided new potentials, but also new challenges for accurate identification and visualisation of the targets in the basal ganglia and the thalamus with an urge to thoroughly evaluate and optimize the stereotactic targeting technique, as well as evaluate accurately in stereotactic space the location and extent of stereotactic Radiofrequency (RF) lesions and the position of deep brain stimulation (DBS) electrodes.

Aims: To study the differences between CT and MRI regarding indirect atlas coordinates in thalamic and pallidal procedures and to evaluate and validate visualisation of the pallidum and the subthalamic nucleus in view of direct targeting irrespective of atlas-derived coordinates. Furthermore, to evaluate the contribution of RF parameters on the size of stereotactic lesions, as well as the impact of size and location on clinical outcome.

Method: The coordinates in relation to the landmarks of the 3rd ventricle of the targets in the pallidum and ventrolateral thalamus were compared between CT and MRI in 34 patients. In another 48 patients direct visualization  of the pallidum was evaluated and compared to indirect atlas based targeting. The possibility and versatility of visualizing the Subthalamic Nucleus (STN) on short acquisition MRI were evaluated in a multicentre study, and the use of alternative landmarks in identification of the STN was demonstrated in another study. In 46 patients CT and MRI were compared regarding the volume of the visible RF lesions. The volume was analysed with regard to coagulation parameters, and the location and size of the lesions were further evaluated concerning the clinical outcome.

Results:Minor deviations were seen between MRI and  CT coordinates of brain targets. The rostro-caudal direction of these deviations were such that they would be easily accounted for during surgery, why MRI can obviate the need for CT in these procedures. MRI using a proton density sequence provided detailed images of the pallidal structures, which demonstrated considerable inter-individual variations in relation to the landmarks of the 3rd ventricle. By using a direct visualization of the target, each patient will act as his or her own atlas, avoiding the uncertainties of atlas-based targeting. The STN could be visualized on various brands of MRI machines in 8 centers in 6 countries with good discrimination and with a short acquisition time, allowing direct visual targeting. The same scanning technique could be used for postoperative localization of the implanted electrodes. In cases where the lateral and inferior borders of the STN cannot be easily distinguished on MRI the Sukeroku sign and the dent internal-capsule-sign signs might be useful. The volume of a stereotactic RF lesion could be as accurately assessed by CT as by MRI. The lesion´s size was most strongly influenced by the temperature used for coagulation. The lesions´ volumes were however rather scattered and difficult to predict in the individual patient based solely on the coagulation parameters. For thalamotomy, the results on tremor was not related to the lesion´s volume. For pallidotomy, larger and more posterior-ventral lesions had better effect on akinesia while effects on tremor and dyskinesias were not related to size or location of the lesions.

Conclusions: The minor deviations of MRI from CT coordinates can be accounted for during surgery, why MRI can obviate the need of CT in these procedures. Direct visualized targeting on MRI of the pallidum is superior to atlas based targeting. The targets in the pallidum and the STN, as well as the location of the electrodes, can be well visualized with short acquisition MRI. When borders of the STN are poorly defined on MRI the Sukeroku sign and the dent internal-capsule-sign signs proved to be useful. The volumes of RF lesions can be accurately assessed by both stereotactic thin slice CT and MRI. The size of these lesions is most strongly influenced by the temperature of coagulation, but difficult to predict in the individual patient based on the coagulation parameters.

Within certain limits, there were no clear relationships between lesions´ volume and location and clinical effects of thalamotomies and pallidotomies.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2012. 48 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1462
Deep brain stimulation, pallidotomy, thalamotomy, Parkinson's disease, essential tremor, CT, MRI
National Category
Research subject
urn:nbn:se:umu:diva-55141 (URN)978-91-7459-325-9 (ISBN)
Public defence
2012-06-08, Room E04, Building 6E, Norrlands universitetssjukhus, Umeå, 09:00 (English)
Available from: 2012-05-16 Created: 2012-05-09 Last updated: 2012-05-16Bibliographically approved

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