Computer mapping of brain-stem sensory centers in man RONALD R. TASKER, M.D., F.R.C.S.(C), hN H. ROWE, PH.D., PEXER HAWRYLYSHYN,B.Sc., AND LESLIE W. ORGAN, M.D.
Departments of Surgery, Electrical Engineering, and Physiology, University of Toronto and the Neurosurgical Unit, Toronto General Hospital, Toronto, Ontario, Canada A computer program is described for use on-line with a two-stage stereotaxic technique in man. It has four capabilities. It transposes coordinates between a brain atlas and a stereotaxic frame, simultaneously adjusting for variations in individual brain dimensions. Corrections for electrode trajectories, and for any irregularities of placement of the stereotaxic frame in the head are also made. It plots an operative template that shows electrode trajectories and the sites from which physiological data are collected appropriately oriented upon a sagittal diagram of the brain. It graphically displays physiological data in the form of a Woolsey-type figurine chart that indicates threshold in milliamperes and, through the use of coded symbols, the quality of response and certain other data. It stores all this data in a tape library together with the locations of any lesions made. This makes it possible to replot any individual patient's operative data at any time. It also permits scanning of the stored protocols from all patients for any particular type of data either by itself or in combination with other data. This retrieved information is plotted on appropriate sagittal brain diagrams corrected for individual variations in brain size. Illustrations of the capabilities of the program are presented particularly with reference to the primary afferent pathways of the upper brain stem. KEY W o R o s brain s t e m
9 9
stereotaxic surgery 9 computer program 9 electrical stimulation 9 afferent pathways
LTHOUGH Horsley and Clarke 5 introduced stereotaxic surgery into the animal laboratory in 1908, individual anatomical variations made human stereotaxis impractical until Spiegel, et al.fl "1~ added x-ray contrast studies to the HorsleyClarke skull landmarks. It soon became apparent, however, that something more than radiological localization would be required to obtain the best results in the operating room, and a variety of physiological techniques soon evolved for the identification of the various
A
,t58
neurological structures through which a stereotaxic probe might pass. Meanwhile, computer techniques with biomedical applications were being developed and it was natural that the next phase in stereotaxis would be the incorporation of this new technology. Most programs thus far developed for use during stereotaxic operations have served to transpose the three-dimensional coordinates of the position of the stereotaxic probe between the grid system of the frame and that
J. Neurosurg. / Volume 44 / April, 1976
C o m p u t e r m a p p i n g of b r a i n - s t e m sensorv c e n t e r s of the brain atlas regardless of the angle of incidence of the electrode to the brain? '3'8 Bertrand, et al., ~ have developed an elegant program which first expands or shrinks the standard atlas diagram as need be to conform to the patient's individual thalamic dimensions and then computes a televised graphic display of the progress of the electrode through successive brain structures with stored atlas diagrams and data describing the trajectory. Fox and Green 4 have developed a program controlled by biplanar television which uses polar rather than rectangular coordinates for the purpose of manipulating their probe in two planes simultaneously, while maintaining the alignment of the probe to the target in each plane. Indeed, the scope of computers in stereotaxic surgery seems infinite. In the laboratory it is now possible for a computer to guide and advance an electrode, then to record, review, and store the data it collects. 8 Our own computer program was developed because of the need to display a large quantity of physiological data collected in the operating room graphically and on-line in such a way as to optimize its use, through visual inspection, for the selection of the lesion site.
Stereotaxic Method Stereotaxic procedures, all performed for the relief of intractable pain or involuntary movement, are carried out in two stages using the Leksell frame, n'12 During the first stage, which is performed under general anesthesia, a frontal burr hole is placed in the same sagittal plane as the intended target to allow all electrode tracts to be plotted in the same sagittal plane. Thus, plotting and review of the collected physiological data are simplified. As accurately as is possible by eye, the stereotaxic frame is applied to the skull in the midline position. A positive contrast third ventriculogram permits measurement with our technique of three-dimensional frame coordinates for the anterior and posterior commissures and for a third point on the midsagittal plane of the brain, usually the top of the septum pellucidum. The dorsal height of the thalamus is measured above the midcommissural point. During the second stage, which is carried out under local anesthesia, the frame is reapplied to the skull precisely as before with special pins. Serial stimulation is J. Neurosurg. / Volume 44 / April, 1976
FIG. 1. Homunculus diagram No. 6 divided into numbered regions to permit computerized storage. A stimulation-induced response of tingling in the contralateral hallux would be coded Figurine 6, 19P; added numerals would indicate the threshold in milliamperes.
carried out at threshold by a 1.5-mm co-axial electrode with a 0.5-mm pole separation activated by trains of square wave pulses at 100 Hz and 3 mS pulse duration. These are delivered every 2 mm as the electrode is advanced toward each of three targets in the same sagittal plane chosen on the basis of the x-ray studies to bracket the expected target area. Exploration usually commences 10-ram above and continues 4 to 10-mm beyond each of these targets. During each procedure, stimulation data are collected at at least 30 sites, some of which yield multiple responses. If necessary, additional stimulation is carried out when a computerized graphic display of all the data is printed out and used to guide selection of the site at which the RF lesion is made. Computer Technique In studying the spatial relationships of the stimulation data for the purpose of target selection, it is particularly important to appreciate the patterns of somatotopo459
R. R. Tasker, et al. TABLE 1
Code used & figurine charts Diagnostic C o d e 1 2 3 4 5 6 7 8 9
= = = = = = = = =
pain P a r k i n s o n ' s disease essential t r e m o r multiple sclerosis cerebellar t r e m o r dystonia torticollis spasticity other, miscellaneous
Quality o f R e s p o n s e C o d e K W H B Vi P
= = = = = =
cold warm hot burning vibration paresthesia, tingling, numbness, electric shock E T = emotional G = taste (gustatory) S m = smell (olfactory) Vo = vocal
Ai = auditory ipsilateral Ac = auditory contralateral A u = general auditory Oi = visual ipsilateral Oc = visual contralateral Ot = general visual (optic) VA = vestibular anticlockwise VC = vestibular clockwise V R = vestibular to the right VL = vestibular to the left V ? = general vestibular Di = dizzy N = nausea
F TD TR TA MID MIA MR MT Do ** ??
= faint, light-headed, woozy = tremor driving = tremor reduction = t r e m o r arrest = involuntary movem e n t drive = involuntary movem e n t arrest = m o t o r response = muscle twitch = pain (dolorogenic) = pial response = u n k n o w n , miscellaneous
Ff~. 2. C o m p u t e r - d r a w n o p e r a t i v e t e m p l a t e b a s e d o n t h e s a g i t t a l s e c t i o n at 13.5 m m f r o m t h e m i d l i n e in t h e S c h a l t e n b r a n d a n d Bailey a t l a s . ~ T h e p a t i e n t ' s a n t e r i o r a n d p o s t e r i o r c o m m i s s u r e s a r e p l o t t e d in t e r m s o f L e k s e l l f r a m e c o o r d i n a t e s a n d t h e a t l a s d i a g r a m is a d j u s t e d to t h e p a t i e n t ' s i n t e r c o m m i s s u r a l d i s t a n c e a n d d o r s a l h e i g h t o f t h a l a m u s ( h e r e 16.5 r a m ) . T h r e e p o t e n t i a l t a r g e t sites a r e i n d i c a t e d by s t a r s . 460
J. Neurosurg. / Volume 44 / April, 1976
Computer mapping of brain-stem sensory centers graphically coded information obtained in the somatosensory system. It is also necessary, however, to recognize the relationship between somatosensory and auditory, vestibular, motor, and occasionally other types of response while keeping in mind both threshold and orientation with respect to anatomical landmarks. At the same time, corrections must be applied for any individual variations of brain dimensions, for angulation or eccentric positioning of the Leksell frame upon the head, and for any deviation of the electrode trajectory from a parasagittal course. Such a task, which requires graphic display of the collected data in order to choose a lesion site that is both effective and safe, is impossible to carry out by hand. To solve this problem, a computer system was developed for the collection, processing, and on-line display of the data. To collect and store the data in a series of data files, a lightweight portable video-data terminal is installed in the operating room interfaced by telephone with the University of Toronto computer and operated in an interactive mode. The series of programs stored in the computer permits the retrieval of the operative data. This includes the threedimensional frame coordinates for the anterior and posterior commissures and the point on the septum pellucidum, the dorsal height of the thalamus, the angle of trajectory of the electrode in the anteroposterior direction, the degree of deviation of electrode trajectory from parasagittal, the sagittal plane explored, and the physiological data themselves. The determination of the XYZ frame coordinates of the anterior and posterior commissures allows computerized correction for individual variations of the thalamic length, for any rotation of the stereotaxic frame in a horizontal plane about a vertical brain axis, and for any lateral displacement of the frame. Corrections for any degree of tilt of the frame about an anteroposterior brain axis is made possible by supplying the computer with the XYZ coordinates of a third point on the brain's midsagittal plane in addition to those of the commissures, usually the top of the septum pellucidum. If the electrode deviates from a parasagittal course, sites on its trajectory will deviate more and more from the sagittal plane of the target, the greater their distance above or below the target. Determination of J. Neurosurg. / Volume 44 / April, 1976
FI6. 3. Computerized stretching (upper) and shrinkage (lower) of the operative template to conform to individual thalamic dimensions.
the mediolateral trajectory angle allows calculation of such deviations at each stimulation site. Corrections for tilt, rotation, or lateral translation of the frame, and for deviations of electrode trajectories from parasagittal are seldom necessary and even then are usually negligible in magnitude. Storage of the physiological data is accomplished with reference to numbered homunculus diagrams subdivided into numbered body regions as illustrated in Fig. 1. To these diagrams may be added alphanumeric symbols that indicate threshold in milliamperes and quality of somatosensory response such as tingling, coolness, and the presence of auditory, vestibular, 461
R. R. Tasker, et al.
Flr 4. Left: Computer-drawn operative template showing three electrode trajectories with stimulation sites. Triangles indicate points at which stimulation up to 2 to 3 mA produced no detectable response in the conscious, unmedicated patient. Sites indicated by numerals, which in turn indicate distance in millimeters above or below the target, are those at which responses occurred. Asterisks indicate lesion sites. Right." Unedited computer-drawn Woolsey-type figurine chart showing the body part appropriately oriented in space, in which stimulation evoked sensory responses at each positive site plotted in the diagram at left. Symbols such as P, FP, AU, indicate details of the response as outlined in Table 1. Right hand numerals under each figurine indicate threshold in milliamperes. Central numerals under each figure correspond to the numerals on the plot at left.
visual, and other effects according to the code shown in Table 1. When all the operative data have been collected and stored, a command from the terminal in the operating room then initiates execution of a program stored in the computer for processing the data which are then plotted with an electrostatic or an incremental pen plotter. The plotting can be considered in steps. At the conclusion of the first stage of the stereotaxic procedure, the computer plots an operative template as shown in Fig. 2 in readiness for selection of tentative targets for exploration during the second stage. The appropriate sagittal section from the Schaltenbrand and Bailey atlas 7 is stretched or shrunk as need be first along the intercommissural line, then vertically, until it fits the patient's 462
brain dimensions. This process is illustrated in Fig. 3. The resultant diagram is then plotted with a superimposed grid ruled in millimeters and reading in Leksell frame coordinates. During the second stage, the computer adds on-line to this template electrode trajectories and stimulation sites appropriately oriented in space as shown in Fig. 4 left. At this stage any corrections necessary in the XYZ coordinates of stimulation sites occasioned by any translation, rotation, or tilt of the frame with respect to the brain or any deviation of the electrode from a parasagittal course are printed out. The computer simultaneously constructs a second on-line plot during the second stage procedure which is shown in Fig. 4 right. At each stimulation site, appropriately oriented in space the re-
J. Neurosurg. / Volume 44 / April, 1976
Computer mapping of brain-stem sensory centers
FL~. 5. Unedited computerized plot of all auditory data stored to date at 9, 11, 13.5, and 16.0 mm from the midline. Corrections for brain dimensions have been applied and sites charted on the nearest available atlas diagram. Stars indicate contralateral responses with the threshold proportional to the size of the symbol. Circles indicate bilateral responses again with threshold proportional to the size of the circle.
quired homunculus diagram is drawn with the body part to which any somatosensory response is referred shaded in. Symbols indicating threshold, quality of sensation, and other data are added according to Table 1 producing a Woolsey-type figurine chart. The entire operative input is also stored in a second data file which can be printed in hard copy by a high-speed printer, and into which any amount of detail can be entered. The dual print-out is now inspected, any additional studies made and plotted, final lesion selection made, and lesion location added to the data file. J. Neurosurg. / Volume 44 / April, 1976
Finally the computer stores all the operative and physiological data for each patient in a tape library so that not only can any individual patient's data be plotted at any time, but also the pooled data from all patients can be scanned for any chosen type of response. After corrections for individual variations of brain dimensions, pooled data are plotted on appropriate sagittal sections of the brain from the Schaltenbrand and Bailey atlas ~ in a dual plot. One of these indicates by symbols the site of response, defining the relative threshold by the size of the symbol. The other plots numerals for matching 463
R. R. Tasker, et al. against the symbols which refer to entries listing full details for each site selection in the hard copy. Figure 5 illustrates the former type of print-out for the auditory system plotted at 9, 11, 13.5, and 16.0 mm from the midline. These data, which show the rostral progression of auditory responses through the lateral lemniscus near the inferior colliculus, the brachium of the inferior colliculus, and the medial geniculate, compare well with the data selected and plotted by hand in our publication on the auditory system. TM Differences are due to exclusion of some of our earlier data which was unsuitable for computer storage from the present print-out and the addition of subsequent material. The capabilities of this search-and-plot facility include, in addition to selection of any one given type of sensory, motor or other response, the comparison of responses of various types. For instance, points giving rise to a somatosensory response of a certain type in a certain body part may be plotted alongside points where stimulation suppressed tremor, either for all patients or only for those with a selected diagnosis such as essential tremor, or the whole brain stem can be charted with a series of Windrose diagrams to show the proportions of stimulations that produced responses referred say to the lips, the hand, and the foot at the various sites stimulated. Similarly proportions of stimulations that produced responses of different qualities may be plotted. The possibilities are as infinite as the permutations and combinations of the stored data. It is hoped that this brief description of our program and its application may be of interest both in the laboratory and the operating room whenever the collection, storage, and display of neurophysiological data is required.
2. Birg W, Mundinger F: Computer calculations of target parameters for a stereotactic apparatus. Acta Neurochir 29:123--129, 1973 3. Coloff E, Gleason CA, Alberts WW, et al: Computer-aided localization techniques for stereotaxic surgery. Confin Neurol 35:65-80, 1973 4. Fox JL, Green RC: Polar coordinates and television monitoring in stereotaxic brain surgery. Confin Neurol 31:123-128, 1969 5. Horsley V, Clarke RH: The structure and functions of the cerebellum examined by a new method. Brain 31:45-124, 1908 6. Peluso F, Gybels J: Calculation of position of electrode point during penetration in human brain. Confin Neuroi 32:213-218, 1970 7. Schaltenbrand G, Bailey P: Introduction to Stereotaxis with an Atlas of the Human Brain, vol 2. Stuttgart: Georg Thieme, 1959 8. Siegel L: A computer-controlled stereotaxic system. IEEE Trans Biomed Eng 16:197-204, 1969 9. Spiegel EA: Development of stereoencephalotomy for extrapyramidal diseases. J Neurosurg 24:433-439, 1966 10. Spiegel EA, Wycis HT, Marks M, et al: Stereotaxic apparatus for operations on the human brain. Science 106:349-350, 1947 11. Tasker RR: Simple localization for stereoencephalotomy using the portable central beam of the image intensifier. Confin Neurol 26:209-212, 1965 12. Tasker RR, Organ LW: Mapping of the somatosensory and auditory pathways in the upper midbrain and thalamus of man, in Somjen EE (ed): NeurophysiologyStudied in Man. International Congress Series no. 253. Amsterdam: Excerpta Medica, 1971, pp 169-187 13. Tasker RR, Organ LW: Stimulation-mapping of the upper human auditory pathway. J Neurosurg 38:320-325, 1973
This paper was presented at the Richard A. Lende Memorial Symposium, August 16, 1974, at the Albany Medical College, Albany, New York. References This research was supported by a grant from the 1. Bertrand G, Olivier A, Thompson CJ: Com- Toronto General Hospital Foundation. Address reprint requests to: Ronald R. Tasker, puter display of stereotaxic brain maps and probe tracts. Acta Neurochir [Suppl] M.D., Room 121, University Wing, Toronto General Hospital, Toronto, Canada. 21:235-243, 1974
464
J. Neurosurg. / Volume 44 / April, 1976
Departments of Surgery, Electrical Engineering, and Physiology, University of Toronto and the Neurosurgical Unit, Toronto General Hospital, Toronto, Ontario, Canada A computer program is described for use on-line with a two-stage stereotaxic technique in man. It has four capabilities. It transposes coordinates between a brain atlas and a stereotaxic frame, simultaneously adjusting for variations in individual brain dimensions. Corrections for electrode trajectories, and for any irregularities of placement of the stereotaxic frame in the head are also made. It plots an operative template that shows electrode trajectories and the sites from which physiological data are collected appropriately oriented upon a sagittal diagram of the brain. It graphically displays physiological data in the form of a Woolsey-type figurine chart that indicates threshold in milliamperes and, through the use of coded symbols, the quality of response and certain other data. It stores all this data in a tape library together with the locations of any lesions made. This makes it possible to replot any individual patient's operative data at any time. It also permits scanning of the stored protocols from all patients for any particular type of data either by itself or in combination with other data. This retrieved information is plotted on appropriate sagittal brain diagrams corrected for individual variations in brain size. Illustrations of the capabilities of the program are presented particularly with reference to the primary afferent pathways of the upper brain stem. KEY W o R o s brain s t e m
9 9
stereotaxic surgery 9 computer program 9 electrical stimulation 9 afferent pathways
LTHOUGH Horsley and Clarke 5 introduced stereotaxic surgery into the animal laboratory in 1908, individual anatomical variations made human stereotaxis impractical until Spiegel, et al.fl "1~ added x-ray contrast studies to the HorsleyClarke skull landmarks. It soon became apparent, however, that something more than radiological localization would be required to obtain the best results in the operating room, and a variety of physiological techniques soon evolved for the identification of the various
A
,t58
neurological structures through which a stereotaxic probe might pass. Meanwhile, computer techniques with biomedical applications were being developed and it was natural that the next phase in stereotaxis would be the incorporation of this new technology. Most programs thus far developed for use during stereotaxic operations have served to transpose the three-dimensional coordinates of the position of the stereotaxic probe between the grid system of the frame and that
J. Neurosurg. / Volume 44 / April, 1976
C o m p u t e r m a p p i n g of b r a i n - s t e m sensorv c e n t e r s of the brain atlas regardless of the angle of incidence of the electrode to the brain? '3'8 Bertrand, et al., ~ have developed an elegant program which first expands or shrinks the standard atlas diagram as need be to conform to the patient's individual thalamic dimensions and then computes a televised graphic display of the progress of the electrode through successive brain structures with stored atlas diagrams and data describing the trajectory. Fox and Green 4 have developed a program controlled by biplanar television which uses polar rather than rectangular coordinates for the purpose of manipulating their probe in two planes simultaneously, while maintaining the alignment of the probe to the target in each plane. Indeed, the scope of computers in stereotaxic surgery seems infinite. In the laboratory it is now possible for a computer to guide and advance an electrode, then to record, review, and store the data it collects. 8 Our own computer program was developed because of the need to display a large quantity of physiological data collected in the operating room graphically and on-line in such a way as to optimize its use, through visual inspection, for the selection of the lesion site.
Stereotaxic Method Stereotaxic procedures, all performed for the relief of intractable pain or involuntary movement, are carried out in two stages using the Leksell frame, n'12 During the first stage, which is performed under general anesthesia, a frontal burr hole is placed in the same sagittal plane as the intended target to allow all electrode tracts to be plotted in the same sagittal plane. Thus, plotting and review of the collected physiological data are simplified. As accurately as is possible by eye, the stereotaxic frame is applied to the skull in the midline position. A positive contrast third ventriculogram permits measurement with our technique of three-dimensional frame coordinates for the anterior and posterior commissures and for a third point on the midsagittal plane of the brain, usually the top of the septum pellucidum. The dorsal height of the thalamus is measured above the midcommissural point. During the second stage, which is carried out under local anesthesia, the frame is reapplied to the skull precisely as before with special pins. Serial stimulation is J. Neurosurg. / Volume 44 / April, 1976
FIG. 1. Homunculus diagram No. 6 divided into numbered regions to permit computerized storage. A stimulation-induced response of tingling in the contralateral hallux would be coded Figurine 6, 19P; added numerals would indicate the threshold in milliamperes.
carried out at threshold by a 1.5-mm co-axial electrode with a 0.5-mm pole separation activated by trains of square wave pulses at 100 Hz and 3 mS pulse duration. These are delivered every 2 mm as the electrode is advanced toward each of three targets in the same sagittal plane chosen on the basis of the x-ray studies to bracket the expected target area. Exploration usually commences 10-ram above and continues 4 to 10-mm beyond each of these targets. During each procedure, stimulation data are collected at at least 30 sites, some of which yield multiple responses. If necessary, additional stimulation is carried out when a computerized graphic display of all the data is printed out and used to guide selection of the site at which the RF lesion is made. Computer Technique In studying the spatial relationships of the stimulation data for the purpose of target selection, it is particularly important to appreciate the patterns of somatotopo459
R. R. Tasker, et al. TABLE 1
Code used & figurine charts Diagnostic C o d e 1 2 3 4 5 6 7 8 9
= = = = = = = = =
pain P a r k i n s o n ' s disease essential t r e m o r multiple sclerosis cerebellar t r e m o r dystonia torticollis spasticity other, miscellaneous
Quality o f R e s p o n s e C o d e K W H B Vi P
= = = = = =
cold warm hot burning vibration paresthesia, tingling, numbness, electric shock E T = emotional G = taste (gustatory) S m = smell (olfactory) Vo = vocal
Ai = auditory ipsilateral Ac = auditory contralateral A u = general auditory Oi = visual ipsilateral Oc = visual contralateral Ot = general visual (optic) VA = vestibular anticlockwise VC = vestibular clockwise V R = vestibular to the right VL = vestibular to the left V ? = general vestibular Di = dizzy N = nausea
F TD TR TA MID MIA MR MT Do ** ??
= faint, light-headed, woozy = tremor driving = tremor reduction = t r e m o r arrest = involuntary movem e n t drive = involuntary movem e n t arrest = m o t o r response = muscle twitch = pain (dolorogenic) = pial response = u n k n o w n , miscellaneous
Ff~. 2. C o m p u t e r - d r a w n o p e r a t i v e t e m p l a t e b a s e d o n t h e s a g i t t a l s e c t i o n at 13.5 m m f r o m t h e m i d l i n e in t h e S c h a l t e n b r a n d a n d Bailey a t l a s . ~ T h e p a t i e n t ' s a n t e r i o r a n d p o s t e r i o r c o m m i s s u r e s a r e p l o t t e d in t e r m s o f L e k s e l l f r a m e c o o r d i n a t e s a n d t h e a t l a s d i a g r a m is a d j u s t e d to t h e p a t i e n t ' s i n t e r c o m m i s s u r a l d i s t a n c e a n d d o r s a l h e i g h t o f t h a l a m u s ( h e r e 16.5 r a m ) . T h r e e p o t e n t i a l t a r g e t sites a r e i n d i c a t e d by s t a r s . 460
J. Neurosurg. / Volume 44 / April, 1976
Computer mapping of brain-stem sensory centers graphically coded information obtained in the somatosensory system. It is also necessary, however, to recognize the relationship between somatosensory and auditory, vestibular, motor, and occasionally other types of response while keeping in mind both threshold and orientation with respect to anatomical landmarks. At the same time, corrections must be applied for any individual variations of brain dimensions, for angulation or eccentric positioning of the Leksell frame upon the head, and for any deviation of the electrode trajectory from a parasagittal course. Such a task, which requires graphic display of the collected data in order to choose a lesion site that is both effective and safe, is impossible to carry out by hand. To solve this problem, a computer system was developed for the collection, processing, and on-line display of the data. To collect and store the data in a series of data files, a lightweight portable video-data terminal is installed in the operating room interfaced by telephone with the University of Toronto computer and operated in an interactive mode. The series of programs stored in the computer permits the retrieval of the operative data. This includes the threedimensional frame coordinates for the anterior and posterior commissures and the point on the septum pellucidum, the dorsal height of the thalamus, the angle of trajectory of the electrode in the anteroposterior direction, the degree of deviation of electrode trajectory from parasagittal, the sagittal plane explored, and the physiological data themselves. The determination of the XYZ frame coordinates of the anterior and posterior commissures allows computerized correction for individual variations of the thalamic length, for any rotation of the stereotaxic frame in a horizontal plane about a vertical brain axis, and for any lateral displacement of the frame. Corrections for any degree of tilt of the frame about an anteroposterior brain axis is made possible by supplying the computer with the XYZ coordinates of a third point on the brain's midsagittal plane in addition to those of the commissures, usually the top of the septum pellucidum. If the electrode deviates from a parasagittal course, sites on its trajectory will deviate more and more from the sagittal plane of the target, the greater their distance above or below the target. Determination of J. Neurosurg. / Volume 44 / April, 1976
FI6. 3. Computerized stretching (upper) and shrinkage (lower) of the operative template to conform to individual thalamic dimensions.
the mediolateral trajectory angle allows calculation of such deviations at each stimulation site. Corrections for tilt, rotation, or lateral translation of the frame, and for deviations of electrode trajectories from parasagittal are seldom necessary and even then are usually negligible in magnitude. Storage of the physiological data is accomplished with reference to numbered homunculus diagrams subdivided into numbered body regions as illustrated in Fig. 1. To these diagrams may be added alphanumeric symbols that indicate threshold in milliamperes and quality of somatosensory response such as tingling, coolness, and the presence of auditory, vestibular, 461
R. R. Tasker, et al.
Flr 4. Left: Computer-drawn operative template showing three electrode trajectories with stimulation sites. Triangles indicate points at which stimulation up to 2 to 3 mA produced no detectable response in the conscious, unmedicated patient. Sites indicated by numerals, which in turn indicate distance in millimeters above or below the target, are those at which responses occurred. Asterisks indicate lesion sites. Right." Unedited computer-drawn Woolsey-type figurine chart showing the body part appropriately oriented in space, in which stimulation evoked sensory responses at each positive site plotted in the diagram at left. Symbols such as P, FP, AU, indicate details of the response as outlined in Table 1. Right hand numerals under each figurine indicate threshold in milliamperes. Central numerals under each figure correspond to the numerals on the plot at left.
visual, and other effects according to the code shown in Table 1. When all the operative data have been collected and stored, a command from the terminal in the operating room then initiates execution of a program stored in the computer for processing the data which are then plotted with an electrostatic or an incremental pen plotter. The plotting can be considered in steps. At the conclusion of the first stage of the stereotaxic procedure, the computer plots an operative template as shown in Fig. 2 in readiness for selection of tentative targets for exploration during the second stage. The appropriate sagittal section from the Schaltenbrand and Bailey atlas 7 is stretched or shrunk as need be first along the intercommissural line, then vertically, until it fits the patient's 462
brain dimensions. This process is illustrated in Fig. 3. The resultant diagram is then plotted with a superimposed grid ruled in millimeters and reading in Leksell frame coordinates. During the second stage, the computer adds on-line to this template electrode trajectories and stimulation sites appropriately oriented in space as shown in Fig. 4 left. At this stage any corrections necessary in the XYZ coordinates of stimulation sites occasioned by any translation, rotation, or tilt of the frame with respect to the brain or any deviation of the electrode from a parasagittal course are printed out. The computer simultaneously constructs a second on-line plot during the second stage procedure which is shown in Fig. 4 right. At each stimulation site, appropriately oriented in space the re-
J. Neurosurg. / Volume 44 / April, 1976
Computer mapping of brain-stem sensory centers
FL~. 5. Unedited computerized plot of all auditory data stored to date at 9, 11, 13.5, and 16.0 mm from the midline. Corrections for brain dimensions have been applied and sites charted on the nearest available atlas diagram. Stars indicate contralateral responses with the threshold proportional to the size of the symbol. Circles indicate bilateral responses again with threshold proportional to the size of the circle.
quired homunculus diagram is drawn with the body part to which any somatosensory response is referred shaded in. Symbols indicating threshold, quality of sensation, and other data are added according to Table 1 producing a Woolsey-type figurine chart. The entire operative input is also stored in a second data file which can be printed in hard copy by a high-speed printer, and into which any amount of detail can be entered. The dual print-out is now inspected, any additional studies made and plotted, final lesion selection made, and lesion location added to the data file. J. Neurosurg. / Volume 44 / April, 1976
Finally the computer stores all the operative and physiological data for each patient in a tape library so that not only can any individual patient's data be plotted at any time, but also the pooled data from all patients can be scanned for any chosen type of response. After corrections for individual variations of brain dimensions, pooled data are plotted on appropriate sagittal sections of the brain from the Schaltenbrand and Bailey atlas ~ in a dual plot. One of these indicates by symbols the site of response, defining the relative threshold by the size of the symbol. The other plots numerals for matching 463
R. R. Tasker, et al. against the symbols which refer to entries listing full details for each site selection in the hard copy. Figure 5 illustrates the former type of print-out for the auditory system plotted at 9, 11, 13.5, and 16.0 mm from the midline. These data, which show the rostral progression of auditory responses through the lateral lemniscus near the inferior colliculus, the brachium of the inferior colliculus, and the medial geniculate, compare well with the data selected and plotted by hand in our publication on the auditory system. TM Differences are due to exclusion of some of our earlier data which was unsuitable for computer storage from the present print-out and the addition of subsequent material. The capabilities of this search-and-plot facility include, in addition to selection of any one given type of sensory, motor or other response, the comparison of responses of various types. For instance, points giving rise to a somatosensory response of a certain type in a certain body part may be plotted alongside points where stimulation suppressed tremor, either for all patients or only for those with a selected diagnosis such as essential tremor, or the whole brain stem can be charted with a series of Windrose diagrams to show the proportions of stimulations that produced responses referred say to the lips, the hand, and the foot at the various sites stimulated. Similarly proportions of stimulations that produced responses of different qualities may be plotted. The possibilities are as infinite as the permutations and combinations of the stored data. It is hoped that this brief description of our program and its application may be of interest both in the laboratory and the operating room whenever the collection, storage, and display of neurophysiological data is required.
2. Birg W, Mundinger F: Computer calculations of target parameters for a stereotactic apparatus. Acta Neurochir 29:123--129, 1973 3. Coloff E, Gleason CA, Alberts WW, et al: Computer-aided localization techniques for stereotaxic surgery. Confin Neurol 35:65-80, 1973 4. Fox JL, Green RC: Polar coordinates and television monitoring in stereotaxic brain surgery. Confin Neurol 31:123-128, 1969 5. Horsley V, Clarke RH: The structure and functions of the cerebellum examined by a new method. Brain 31:45-124, 1908 6. Peluso F, Gybels J: Calculation of position of electrode point during penetration in human brain. Confin Neuroi 32:213-218, 1970 7. Schaltenbrand G, Bailey P: Introduction to Stereotaxis with an Atlas of the Human Brain, vol 2. Stuttgart: Georg Thieme, 1959 8. Siegel L: A computer-controlled stereotaxic system. IEEE Trans Biomed Eng 16:197-204, 1969 9. Spiegel EA: Development of stereoencephalotomy for extrapyramidal diseases. J Neurosurg 24:433-439, 1966 10. Spiegel EA, Wycis HT, Marks M, et al: Stereotaxic apparatus for operations on the human brain. Science 106:349-350, 1947 11. Tasker RR: Simple localization for stereoencephalotomy using the portable central beam of the image intensifier. Confin Neurol 26:209-212, 1965 12. Tasker RR, Organ LW: Mapping of the somatosensory and auditory pathways in the upper midbrain and thalamus of man, in Somjen EE (ed): NeurophysiologyStudied in Man. International Congress Series no. 253. Amsterdam: Excerpta Medica, 1971, pp 169-187 13. Tasker RR, Organ LW: Stimulation-mapping of the upper human auditory pathway. J Neurosurg 38:320-325, 1973
This paper was presented at the Richard A. Lende Memorial Symposium, August 16, 1974, at the Albany Medical College, Albany, New York. References This research was supported by a grant from the 1. Bertrand G, Olivier A, Thompson CJ: Com- Toronto General Hospital Foundation. Address reprint requests to: Ronald R. Tasker, puter display of stereotaxic brain maps and probe tracts. Acta Neurochir [Suppl] M.D., Room 121, University Wing, Toronto General Hospital, Toronto, Canada. 21:235-243, 1974
464
J. Neurosurg. / Volume 44 / April, 1976
