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The neurological diagnostic process
T I N S - April 1979
109
5. Lenox, R. H., Gandhi, O. P., Meyerhoff, J. L. sacrificed is coupled to the microwave milliseconds. If we are to be able to and Grove, H.M. (1976) IEEE Trans. field with the same efficiency, thereby correlate such events with neurochemical Microwave Theory Tech. 24, 58--61. estimating the net power received by each changes in rapidly turning over meta6. Lenox, R. H., Meyerhoff, J. L., Gandhi, O. P. animal. With the microwave waveguide bolites, it will be necessary to apply and Wray, H.L. (1977) J. Cyclic Nucieotide applicators presently in use, the investi- increasing amounts of power for shorter Research 3, 367-379. 7. Lust, W. D.,Passonneau, J. V.andVeech, R. L. gator must determine the configuration of periods of time. In order to accomplish (1973) Science 181,280--282. heating patterns within the brain by this most effectively it will be necessary to 8. Medina, M. A., Jones, D. J., Stavinoha, W. B. assessing the pattern of regional enzyme apply the microwave energy as uniformly and Ross, D.H. (1975) J. Neurochem. 24, inactivation versus duration of exposure as possible throughout the brain. The 223-227. for each region of interest. It is critical that requirement for increased amounts of 9. Meyerhoff, J.L., Balcom, G.J. and Lenox, R. H. (1978) Brain Res. 152, 161-169. a time course of inactivation be power incident to the animal is technodocumented for each enzyme involved in logically achievable, but generation of a 10. Meyerhoff, J. L., Gandhi, O. P., Jacobi, J. H. and Lenox, R. H. (1979) IEEE Trans. Microthe metabolism of the substrate of uniform field within the brain during a wave Theory Tech. (in press). interest, since irreversible inactivation of waveguide exposure requires further 11. Meyerhoff, J. L, Lenox, R.H., Kant, G.J., different enzymes may require differing research. Studies of the parameters Mougey, E. H., Pennington,L. L. and Sessions, G. R. (1978) Society for Neuroscience Abs. 4, amounts of heat energy deposition. Since n e c e s s a r y to attain this goal are in 1111. the fields generated within the animal are progress. Microwave irradiation will conalso orientation-dependent in current tinue to be very useful to the neuro- 12. Schmidt, M.J., Schmidt, D. E. and Robison, G. A. (1971) Science 173, 1142-1143. microwave systems, there is a persisting sciences, but variables inherent in the 13. Stavinoha, W. B. (1978) In: D. Jenden (ed.), requirement to immobilize the animal to a technology must be recognized and Cholinergic Mechanisms and Psychopharmaco. logy, Plenum Press, New York, pp. 169-179. standard orientation vis-a-vis the polariza- controlled wherever possible. 14. Stavinoha,W., Pepelko, B. and Smith,P. (1970) tion of the microwave E field. These kinds Pharmacologist 12, 257. of parameters must be worked out for Reading list 1. Balcom, G.J., Lenox, R.H. and Meyerhoff, 15. Swaab, D.F. (1971) J. Neurochem. 18, each inactivation unit and for each species 2085-2092. J. L. (1975) J. Neurochem. 24, 609-613. of animal to be studied. Once these 2. Brown, P.V., Lenox, R.H. and Meyerhoff, conditions have been clearly designated, J.L. (1978) IEEE Trans. Biomed. Eng. 25, R. H. Lenox and P. V. Brown are members of the the investigator can use the microwave 205-208. Department of Psychiatry, Neuroscience Research technique to advantage. 3. Butcher, L. L. and Butcher, S. G. (1976) Life Unit, and J. L. Meyerhoff is Chief of the NeuroendoSci. 19, 1079-1088. crinology and Neurochemistry Branch, Department 4. Jones, D. J., Medina, M. A., Ross, D. H. and of Medical Neurosciences, Division of NeuroFuture of microwave inactivation systems Stavinoha, W.B. (1974) Life Sci. 14, psychiatry, Walter Reed Army Medical Center, Microwave inactivation technology 1577-1585. Washington, DC 20012, U.S.A. continues to develop; attempts are being made to overcome some of the limitations of the techniques noted above. The energy t c a I t| I't, distribution and accompanying heat pattern within a load exposed in a microwave field are dependent not only upon the shape, dielectric properties, and its orientation with respect to the field, but also upon the frequency of the microwave field. Our laboratory has studied the pattern of energy, deposition at different frequencies using cytochemical techniques to identify patterns of enzyme Present clinical education leaves medical students to develop their diagnostic expertise inactivation. We previously observed that through experience alone. However, recent studies have s h o w n that the attainment o f this heat deposition as well as pattern of expertise can be accelerated by the teaching o f appropriate information and decisions enzyme inactivation in the rat brain at theory. John Balla feels that students can, and should, be actively taught to convert 2450 MHz with two different applicator clerical, inductive data collection into an expert technique which follows specific leads in designs was non-uniform and markedly a deductive process. affected by rotation of the rat head. Using Over the last few years the process of Kleinmuntza was one of the first to a waveguide applicator designed for clinical diagnosis has been the subject of study the diagnostic process, and he felt exposure at 986 MHz, recent studies in increasing scrutiny. The realization that that the highly structured nature of the our laboratory have shown non- the diagnostic process lends itself to clinical data which was presented to the uniformity of heat deposition in the brain, clinical analysis has important practical as neurologist made it particularly amenable but have also demonstrated that the well as theoretical implications. From the to analysis. He was able to study a number pattern of energy absorption at 986 MHz practical point of view, we may be able to of neurologists using a technique similar is independent of orientation of the ask if teaching methods could be to the game of '20 questions'. A n 'actor', animal within the waveguide (Fig. 3) 2. improved and whether computer techno- who would have to be an expert Thus, the use of this frequency with rats logy has a place in clinical diagnosis. From neurologist, would think of a specific might alleviate the requirement of rigor- the theoretical side, we can expect diagnosis. The 'examiner' would then ask ous immobilization of the subject during significant advances in diagnostic skills questions to which 'yes' or 'no' answers sacrifice. once we have a better understanding of only were given. Kleinmuntz was able to Neurophysiological events occur in the diagnostic process itself. show that the expert 'examiner' tended to
The neurological diagnostic process
(~ El~vler/Nonh~HollandBiomedicalPress1979
110 go from the general to the specific, and used categorization of diseases into groups. The expert was also capable of asking the most pertinent questions, so that there would be few false leads followed by him. He also concluded that this to some extent depended on visual representation of the nervous system in the neurologist's mind and there was a constant process of feedback between the symptoms and anatomical location. Thus, specific questions would be asked in the way of active hypothesis testing. He found that the clinicians who were studied were able to verbalize and therefore could be assessed adequately. He was also able to conclude that with changing data, hypotheses would also change. A great deal of hypothesis formation depended on statistical knowledge, and the expert was able to behave as a good statistition. From all this, 'clinical intuition' was concluded to be amenable to 'rigorous scientific study'. Wartman 5 studied an expert neurologist, particularly to see how his thought processes were organized whilst diagnosis was taking place. He felt that this involved symbolic manipulation similar to the manipulations which would be carried out by a computer. He was also able to show that the various diseases would be categorized into groups and that this was necessary because of the inability of the human brain to deal with more than 5 --- 2 concepts at any one time. He found that most of the questions asked by the neurologist were specifically directed at testing specific hypotheses. In hypothesis formation probability played a significant part in that questions were nearly always goal-oriented. He demonstrated that after the interview the neurologist only tended to remember what he regarded as pertinent information, forgetting the rest. Salamon, Gr6my and their colleagues 4 in France have for some time been working with neurological diagnostic problems, and their aim has been to modify teaching approaches and curriculum content, and also to show how computer technology could be used in the process. They also suggested the importance of distinguishing the aetiological and topographic phases of the process. One may therefore conclude that the method of the expert involves early hypothesis formation from early cues. Such cues may involve early pattern recognition where a number of cues are immediately put into a pattern which is recognized by the expert. These early hypotheses are then tested and re-
TINS - April 1979
evaluated. This is the process where clarification of the symptoms will take place so that they may be put into clearly defined categories. The expert wilt never accept statements from a patient without testing them and clarifying them. If the data thus obtained conflict with the original hypothesis then alternates will be formed and again re-evaluated. The process is therefore one of sequential data collection with feedback resulting in confirming or discarding hypotheses. These hypotheses are put into a hierarchy where the most probable and the one with the most utility ranks before all the rest. (Utility refers equally to the danger of missing the diagnosis as to the availability of treatment.) Throughout this process there is immediate conversion of symptoms into relevant anatomy and pathology which is related to the expert's vast fund of knowledge. From these, deductions are made and relevant questions could again be asked, looking for further significant information. Looking at this process it becomes obvious that it is by no means an unbiased impartial method of data collection where the history is followed by the examination and then specialized t e s t s before a diagnosis is made. On the contrary, the scheme involves well-defined routes of collecting data to verify or disprove hypotheses. This has lead CampbelP to ask if medical education is a hoax, in that it is obvious that what is being taught to medical students is opposite to the practice of the expert. To this stage, what we have learnt about the diagnostic process has had little practical application. Computers are used mainly for storage of information. Thelre are reports of the use of desk computers for neurological diagnosis 2, but little else of great practical importance. For instance, few, if any, medical schools would make a positive effort to teach students the basics of information and decisions theory which are involved in the diagnostic process. We feel that this is a great pity and a hindrance to their future work. Therefore, our own interest has concerned the process as seen in medical students at different levels of their development. We have been contrasting their technique with that of the expert. Our method involves video-taping students and experts whilst taking a history and then replaying the tape whilst the subjects are being interrogated about their thought processes. Lately, one of us has been acting the part of a patient, so that we may be able to standardize the
procedure. No 'Oscars' were awarded, but we felt that the method was very successful, especially when one neurologist in all seriousness asked the 'patient' for a referral letter from her local doctor, and another asked her to undress so that he could examine her. We feel that lack of clarification of symptoms and inability to convert symptoms into meaningful anatomy and pathology are the gravest problems faced by students. Their technique tends to be one of clerical, inductive data collection as opposed to following specific leads and using them in a deductive process, It is hoped that proper techniques may eventually be taught to students at an earlier stage of their development so that their diagnostic skills may be improved as a result. We also foresee the possibility where postgraduates who have particular problems may have special video-tape coaching sessions to see themselves, much as is done in some ski or tennis coaching 'clinics'. JOHN 1. BALLA Dept. of Neurology, Melbourne, Australia.
Prince Henry's Hospital.
1. Campbell, E. J. M. (1976) Lancet i, 134--136. 2. Hofferberth, B. and Gottschaldt, M. (1978) Meth. Inform. Med. 17.
3. Kleinmuntz,B. (1968) In: B. Kleinmuntz(ed.), Formal Representation o f Human Judgment,
Wiley, New York, pp. 149--186. 4. Salamon, R., Bernadet, M., SamSon, M., Derouesne, C. and Gr6my, F. (1976) Meth. Inform. Med. 15, 174-179. 5. Wortman, P. M. (1972) Computer.s and Biomedical Research 5, 315-328.
109
5. Lenox, R. H., Gandhi, O. P., Meyerhoff, J. L. sacrificed is coupled to the microwave milliseconds. If we are to be able to and Grove, H.M. (1976) IEEE Trans. field with the same efficiency, thereby correlate such events with neurochemical Microwave Theory Tech. 24, 58--61. estimating the net power received by each changes in rapidly turning over meta6. Lenox, R. H., Meyerhoff, J. L., Gandhi, O. P. animal. With the microwave waveguide bolites, it will be necessary to apply and Wray, H.L. (1977) J. Cyclic Nucieotide applicators presently in use, the investi- increasing amounts of power for shorter Research 3, 367-379. 7. Lust, W. D.,Passonneau, J. V.andVeech, R. L. gator must determine the configuration of periods of time. In order to accomplish (1973) Science 181,280--282. heating patterns within the brain by this most effectively it will be necessary to 8. Medina, M. A., Jones, D. J., Stavinoha, W. B. assessing the pattern of regional enzyme apply the microwave energy as uniformly and Ross, D.H. (1975) J. Neurochem. 24, inactivation versus duration of exposure as possible throughout the brain. The 223-227. for each region of interest. It is critical that requirement for increased amounts of 9. Meyerhoff, J.L., Balcom, G.J. and Lenox, R. H. (1978) Brain Res. 152, 161-169. a time course of inactivation be power incident to the animal is technodocumented for each enzyme involved in logically achievable, but generation of a 10. Meyerhoff, J. L., Gandhi, O. P., Jacobi, J. H. and Lenox, R. H. (1979) IEEE Trans. Microthe metabolism of the substrate of uniform field within the brain during a wave Theory Tech. (in press). interest, since irreversible inactivation of waveguide exposure requires further 11. Meyerhoff, J. L, Lenox, R.H., Kant, G.J., different enzymes may require differing research. Studies of the parameters Mougey, E. H., Pennington,L. L. and Sessions, G. R. (1978) Society for Neuroscience Abs. 4, amounts of heat energy deposition. Since n e c e s s a r y to attain this goal are in 1111. the fields generated within the animal are progress. Microwave irradiation will conalso orientation-dependent in current tinue to be very useful to the neuro- 12. Schmidt, M.J., Schmidt, D. E. and Robison, G. A. (1971) Science 173, 1142-1143. microwave systems, there is a persisting sciences, but variables inherent in the 13. Stavinoha, W. B. (1978) In: D. Jenden (ed.), requirement to immobilize the animal to a technology must be recognized and Cholinergic Mechanisms and Psychopharmaco. logy, Plenum Press, New York, pp. 169-179. standard orientation vis-a-vis the polariza- controlled wherever possible. 14. Stavinoha,W., Pepelko, B. and Smith,P. (1970) tion of the microwave E field. These kinds Pharmacologist 12, 257. of parameters must be worked out for Reading list 1. Balcom, G.J., Lenox, R.H. and Meyerhoff, 15. Swaab, D.F. (1971) J. Neurochem. 18, each inactivation unit and for each species 2085-2092. J. L. (1975) J. Neurochem. 24, 609-613. of animal to be studied. Once these 2. Brown, P.V., Lenox, R.H. and Meyerhoff, conditions have been clearly designated, J.L. (1978) IEEE Trans. Biomed. Eng. 25, R. H. Lenox and P. V. Brown are members of the the investigator can use the microwave 205-208. Department of Psychiatry, Neuroscience Research technique to advantage. 3. Butcher, L. L. and Butcher, S. G. (1976) Life Unit, and J. L. Meyerhoff is Chief of the NeuroendoSci. 19, 1079-1088. crinology and Neurochemistry Branch, Department 4. Jones, D. J., Medina, M. A., Ross, D. H. and of Medical Neurosciences, Division of NeuroFuture of microwave inactivation systems Stavinoha, W.B. (1974) Life Sci. 14, psychiatry, Walter Reed Army Medical Center, Microwave inactivation technology 1577-1585. Washington, DC 20012, U.S.A. continues to develop; attempts are being made to overcome some of the limitations of the techniques noted above. The energy t c a I t| I't, distribution and accompanying heat pattern within a load exposed in a microwave field are dependent not only upon the shape, dielectric properties, and its orientation with respect to the field, but also upon the frequency of the microwave field. Our laboratory has studied the pattern of energy, deposition at different frequencies using cytochemical techniques to identify patterns of enzyme Present clinical education leaves medical students to develop their diagnostic expertise inactivation. We previously observed that through experience alone. However, recent studies have s h o w n that the attainment o f this heat deposition as well as pattern of expertise can be accelerated by the teaching o f appropriate information and decisions enzyme inactivation in the rat brain at theory. John Balla feels that students can, and should, be actively taught to convert 2450 MHz with two different applicator clerical, inductive data collection into an expert technique which follows specific leads in designs was non-uniform and markedly a deductive process. affected by rotation of the rat head. Using Over the last few years the process of Kleinmuntza was one of the first to a waveguide applicator designed for clinical diagnosis has been the subject of study the diagnostic process, and he felt exposure at 986 MHz, recent studies in increasing scrutiny. The realization that that the highly structured nature of the our laboratory have shown non- the diagnostic process lends itself to clinical data which was presented to the uniformity of heat deposition in the brain, clinical analysis has important practical as neurologist made it particularly amenable but have also demonstrated that the well as theoretical implications. From the to analysis. He was able to study a number pattern of energy absorption at 986 MHz practical point of view, we may be able to of neurologists using a technique similar is independent of orientation of the ask if teaching methods could be to the game of '20 questions'. A n 'actor', animal within the waveguide (Fig. 3) 2. improved and whether computer techno- who would have to be an expert Thus, the use of this frequency with rats logy has a place in clinical diagnosis. From neurologist, would think of a specific might alleviate the requirement of rigor- the theoretical side, we can expect diagnosis. The 'examiner' would then ask ous immobilization of the subject during significant advances in diagnostic skills questions to which 'yes' or 'no' answers sacrifice. once we have a better understanding of only were given. Kleinmuntz was able to Neurophysiological events occur in the diagnostic process itself. show that the expert 'examiner' tended to
The neurological diagnostic process
(~ El~vler/Nonh~HollandBiomedicalPress1979
110 go from the general to the specific, and used categorization of diseases into groups. The expert was also capable of asking the most pertinent questions, so that there would be few false leads followed by him. He also concluded that this to some extent depended on visual representation of the nervous system in the neurologist's mind and there was a constant process of feedback between the symptoms and anatomical location. Thus, specific questions would be asked in the way of active hypothesis testing. He found that the clinicians who were studied were able to verbalize and therefore could be assessed adequately. He was also able to conclude that with changing data, hypotheses would also change. A great deal of hypothesis formation depended on statistical knowledge, and the expert was able to behave as a good statistition. From all this, 'clinical intuition' was concluded to be amenable to 'rigorous scientific study'. Wartman 5 studied an expert neurologist, particularly to see how his thought processes were organized whilst diagnosis was taking place. He felt that this involved symbolic manipulation similar to the manipulations which would be carried out by a computer. He was also able to show that the various diseases would be categorized into groups and that this was necessary because of the inability of the human brain to deal with more than 5 --- 2 concepts at any one time. He found that most of the questions asked by the neurologist were specifically directed at testing specific hypotheses. In hypothesis formation probability played a significant part in that questions were nearly always goal-oriented. He demonstrated that after the interview the neurologist only tended to remember what he regarded as pertinent information, forgetting the rest. Salamon, Gr6my and their colleagues 4 in France have for some time been working with neurological diagnostic problems, and their aim has been to modify teaching approaches and curriculum content, and also to show how computer technology could be used in the process. They also suggested the importance of distinguishing the aetiological and topographic phases of the process. One may therefore conclude that the method of the expert involves early hypothesis formation from early cues. Such cues may involve early pattern recognition where a number of cues are immediately put into a pattern which is recognized by the expert. These early hypotheses are then tested and re-
TINS - April 1979
evaluated. This is the process where clarification of the symptoms will take place so that they may be put into clearly defined categories. The expert wilt never accept statements from a patient without testing them and clarifying them. If the data thus obtained conflict with the original hypothesis then alternates will be formed and again re-evaluated. The process is therefore one of sequential data collection with feedback resulting in confirming or discarding hypotheses. These hypotheses are put into a hierarchy where the most probable and the one with the most utility ranks before all the rest. (Utility refers equally to the danger of missing the diagnosis as to the availability of treatment.) Throughout this process there is immediate conversion of symptoms into relevant anatomy and pathology which is related to the expert's vast fund of knowledge. From these, deductions are made and relevant questions could again be asked, looking for further significant information. Looking at this process it becomes obvious that it is by no means an unbiased impartial method of data collection where the history is followed by the examination and then specialized t e s t s before a diagnosis is made. On the contrary, the scheme involves well-defined routes of collecting data to verify or disprove hypotheses. This has lead CampbelP to ask if medical education is a hoax, in that it is obvious that what is being taught to medical students is opposite to the practice of the expert. To this stage, what we have learnt about the diagnostic process has had little practical application. Computers are used mainly for storage of information. Thelre are reports of the use of desk computers for neurological diagnosis 2, but little else of great practical importance. For instance, few, if any, medical schools would make a positive effort to teach students the basics of information and decisions theory which are involved in the diagnostic process. We feel that this is a great pity and a hindrance to their future work. Therefore, our own interest has concerned the process as seen in medical students at different levels of their development. We have been contrasting their technique with that of the expert. Our method involves video-taping students and experts whilst taking a history and then replaying the tape whilst the subjects are being interrogated about their thought processes. Lately, one of us has been acting the part of a patient, so that we may be able to standardize the
procedure. No 'Oscars' were awarded, but we felt that the method was very successful, especially when one neurologist in all seriousness asked the 'patient' for a referral letter from her local doctor, and another asked her to undress so that he could examine her. We feel that lack of clarification of symptoms and inability to convert symptoms into meaningful anatomy and pathology are the gravest problems faced by students. Their technique tends to be one of clerical, inductive data collection as opposed to following specific leads and using them in a deductive process, It is hoped that proper techniques may eventually be taught to students at an earlier stage of their development so that their diagnostic skills may be improved as a result. We also foresee the possibility where postgraduates who have particular problems may have special video-tape coaching sessions to see themselves, much as is done in some ski or tennis coaching 'clinics'. JOHN 1. BALLA Dept. of Neurology, Melbourne, Australia.
Prince Henry's Hospital.
1. Campbell, E. J. M. (1976) Lancet i, 134--136. 2. Hofferberth, B. and Gottschaldt, M. (1978) Meth. Inform. Med. 17.
3. Kleinmuntz,B. (1968) In: B. Kleinmuntz(ed.), Formal Representation o f Human Judgment,
Wiley, New York, pp. 149--186. 4. Salamon, R., Bernadet, M., SamSon, M., Derouesne, C. and Gr6my, F. (1976) Meth. Inform. Med. 15, 174-179. 5. Wortman, P. M. (1972) Computer.s and Biomedical Research 5, 315-328.