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Teaching the plantar reflex
Teaching the plantar reflex* P.G.H.M.
R a i j m a k e r s , M. C a s t r o C a b e z a s , J . A . S m a l , a n d J. v a n G i j n * *
Introduction Summary
The plantar response is a frequently performed diagnostic test in general practice. In the judgement of this response major interobserver variation and bias has been demonstrated. 1,2 In teaching the technique and interpretation of the plantar response a videotape might be particularly useful. We introduced an instructional videotape for medical students in which three main criteria for recognizing a Babinski sign were demonstrated. 3 1) There must be a contraction of the extensor hallucis longus muscle ( E H L ) . This can be reliably checked by inspection of the E H L tendon, which clearly protrudes under the skin when the muscle is active. A n upgoing big toe without E H L contraction can be produced if the foot dorsiflexes as a whole, or can be falsely suggested if the little toes go down. 2) The response should be part of a flexion synergy. The Babinski sign is part of a primitive withdrawal reflex which is seen in full degree during the first year of life and which may again include the upgoing toe response after injury of the pyramidal tract. 4 E H L contraction is therefore pathological only if it occurs synchronously with activity in other (physiological) flexor muscles of the leg. In some subjects the flexion synergy is weak, but usually the tensor fasciae latae can be seen to tighten as a reference.
The efficacy of an instructional videotape about the interpretation of the plantar response was evaluated during a two week neurological clerkship. Experimental groups saw the videotape, control groups did not. All students (n = 65) assessed plantar responses of two to four different patients. Their judgement was compared with that of one senior neurologist. Only the students who had seen the videotape showed a significant improvement in performance on a second test (t-test, t=-2.26, p=0.031). In addition, these students more frequently took account of the flexion synergy (Fisher exact test, p<0.001). Video can be an efficient tool in medical education. Key words: Plantar reflex; Babinski; Instructional videotape.
3) The response must be reproducible. Voluntary withdrawal can be confusing. In the case of a true extensor response, repeated stroking of only a few centimetres of skin will produce each time an approximately similar fraction of toe and leg movements, whereas voluntary withdrawal will be abolished or inconstant. Furthermore, voluntary toe movements tend to hold on longer, for a few seconds after stimulation, and reflex movements do not. Finally, stimulation of the dorsum of the foot, at the lateral part, will
* Part of this work was presented at the Third International Conference on Teaching and Assessing Clinical Competence (Groningen, May 22-24, 1989). * * University Department of Neurology and Department of Medical Education, University of Utrecht, The Netherlands Address for correspondence: Prof. Dr. J. van Gijn, UniversityHospital Utrecht, Department of Neurology, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. Accepted 11-2-91 Clin Neurol Neurosurg 1991. Vol. 93-3
201
usually also produce an extensor response, if present, and most people are less ticklish at that site.
ities: I certainly extensor; II possibly extensor; III neither extensor nor flexor; IV possibly flexor; V certainly flexor.
In this study we tested the efficacy of the videotape in the evaluation of the plantar response. We also evaluated the use of the three criteria by medical students.
The judgement of the students was compared with that of a senior neurologist - the same throughout the study - who had previously examined the same legs, and who applied the same three criteria that were emphasized in the videotape. Differences between the judgement of individual students and that of the expert neurologist were quantified by means of a standardized rating scale. In this scale a mismatch between the two major categories, normal (III, IV, V) and pathological (I, II), was weighted much more heavily than differences within the same category. This differential weighting was designed before the study. The scale intervals were then judged sufficiently equal to warrant the application of parametric tests. For each plantar response examined, a student could gain 1 to 6 points. The highest score corresponds to maximal agreement, the lowest score to maximal disagreement. The test score for each student was computed by averaging the scores for the four patients. At the end of each test the students were asked to complete a questionnaire to evaluate which, if any, of the three aspects of the plantar response they had considered. The unpaired t-test was used for comparing the final test scores and the mean increase in score of students with and without video instruction. Entrance test and final test scores were compared by means of the paired t-test. Chi-square test and Fisher exact test were used to compare the frequencies with which the three criteria were applied in each group.
Materials and methods
Twelve clusters of five to eight fifth-year medical students (total number 65) at the University of Utrecht rotated through the Department of Neurology for a two week instructional course in neurology. This clerkship included a regular series of 5 to 10 instructional videotapes on various subjects in neurology, and also bedside teaching by a senior neurologist. Previously all students had followed a clerkship in internal medicine and pediatrics. In their pre-clinical period they had been exposed to neurological teaching in the form of 60 clinical lectures, followed by an examination, and two 15-hour courses on the neurological examination and on the history in neurological disease. The students were asked to participate on a voluntary basis. A "Solomon four-group design" was applied, with two experimental and two control groups (with and without entrance test).5 The entrance test was similar to the final test, and was included (for half the clusters of students) to measure the baseline level of knowledge. The other half was used to distinguish between an effect of the videotape and a possible effect of the entrance test. Each cluster of students was randomly assigned to one of the four groups. Only in the experimental groups the videotape about the plantar response was included. This videotape lasted approximately 13 minutes; it was shown on day 8 of the clerkship. On day 2 the entrance test was performed, in half of the experimental and control clusters. On day 10 the final test was performed in all groups. In each test the student was asked to examine four randomly selected legs, of four different patients. The students did not receive any additional information about the patients. They performed and evaluated the reflexes and expressed their judgement by choosing between five possibil202
Results
Sixty-five students were involved in this study; 32 were male, and the mean age was 25 years. The entrance test means for the video group (n=14) and non-video group (n=20) were 3.82 (SD + 1.16) and 4.50 (SD + 1.23), respectively (Table 1). This suggests some sampling error, but the difference was not statistically significant. The final test mean in these two groups was 4.76 (SD __. 0.62) for the video group, and 4.35 (SD + 1.17) for the non-video group. The
unpaired t-test revealed no significant difference in final test means between these two groups. But if the analysis is restricted to the students who performed an entrance test, the mean increase in score (final test score minus entrance test score) for the non-video group was -0.15 (SD + 1.52) and for the video group 0.94 (SD + 1.28), which is a statistically significant difference in favour of the video group (t-test, t=-2.26, p=0.031). Pairwise comparison of entrance and final scores showed a significant difference for the video group (paired t-test, t=-2.75, p=0.016). Table 1 Test scores for each group ( + standard deviation). group
non-video non-video video video
number mean of students entrance test score
16 20 15 14
mean final test score
4.56(+0.73) 4.50(+1.23) 4.35(+1.17) 4.56(+0.60) 3.82(+1.16) 4.76(+0.62)
The students in the video group had more often taken the flexion synergy into account in the final test (29 of 29, versus 25 of 36 students in the non-video group; Fisher exact test, p<0.001). The difference between video and non-video was not significant for the subgroups who had an entrance test (chi square: 1.95, n.s.), because the attention for the flexion synergy in the nonvideo group was higher for the students with an entrance test than in those without (Fisher exact test, p<0.01). For the other two recommended criteria for evaluating the plantar reflex, no significant differences were found between control and experimental groups. Discussion
In an effort to reduce the interobserver variation in the judgement of the plantar reflex that has been reported earlier 2 we introduced a videotape in the neurology course for medical students. We chose a videotape for this study in order to eliminate the interindividual variation of teaching by clinicians. Videotapes are often recommended in teaching clinical skills, although their efficacy shows wide differences.61~ In this video we introduced three main criteria for the interpretation of the plantar response.
General application of these three criteria might lead to a more uniform judgement by clinicians. The differences between experimental and control groups were relatively small and the final results were not significantly different. But only in the group of students who saw the video a significant increase in performance was found. That the differences were small can be explained by the fairly high initial knowledge, which limited further rises in performance. The high performance rates in the groups without video indicate that earlier lectures and practical sessions had been quite effective. In addition, the voluntary basis of participation may have selected the more interested students, resulting in a higher level of knowledge at entry. To measure an increase in knowledge a baseline value is necessary. For this purpose we performed an entrance test. Because of the possible influence of the entrance test on the final results we used the "Solomon four-group design". Our finding that the students with an entrance test in the non-video group more frequently observed the flexion synergy in the final test clearly demonstrates an educational effect of the entrance test in itself. This may explain why an additional effect of the video instruction on this aspect of the final test was attenuated. All students who saw the video took account of the flexion synergy, against approximately 70% of students in the non-video situation. Obviously instruction by video is more effective in emphasizing the importance of the flexion synergy than clinical teachers alone. Van Gijn and Bonke 1 reported earlier that this synergy is largely ignored, and that even experienced neurologists may look at the toes only. The criteria about contraction of the extensor hallucis longus muscle and about the reproducibility were often indicated by students, irrespective of whether they had or had not seen the videotape. Apparently these criteria for the plantar reflex are already well known by medical students. Video instruction about the plantar reflex seems particularly appropriate for students with a lower baseline level of knowledge. The time of clinical teachers can be saved to some extent by this method, while the videotape provides a comparable or higher efficiency of learning. The use of this videotape may lead to a better and more 203
uniform interpretation
of the plantar response.
3
Acknowledgements
4
We are deeply indebted to Liesbeth Hamstra, Laetitia de Kort, Ellen Jansen and Robby Ramcharan for the practical organization of the tests. We also thank L.J. Kappelle, J.G.M. Gerritsma and J.C. van Latum for their critical comments on earlier versions of this paper, and H. Frericks for his advice on statistics. The production of the videotape was made possible by a grant from Sandoz b.v.
5
6 7
8
References 1
2
204
Interpretation of plantar reflexes: biasing effect of other signs and symptoms. J Neurol Neurosurg Psychiatry 1977; 40:787. VAN GUN J. The plantar reflex; a historical, clinical and electromyographic study. Meppel: Krips Repro, 1977 (Thesis, Erasmus University, Rotterdam). V A N G I I N J, B O N K E B.
9
10
VAN GUN J. Equivocal plantar responses: a clinical and electromyographic study. J Neurol Neurosurg Psychiatry 1976; 39:275-82. VAN GUN J. The Babinski sign and the pyramidal syndrome. J Neurol Neurosurg Psychiatry 1978; 41:865-73. CAMPBELL D T , S T A N L E Y JC. Experimental and Quasiexperimental Designs for Research and Teaching. Chicago: Rand McNally College Publishing, 1966:24-25. H U N T D D , D A O A D A K I S CS, W A R D N G , RIES J R . Live versus Videotaped Interviews. J Med Educ 1983; 56:916-18. P A N L R, LEWIS R , N I C C O L I N I R, R U B E N S T E I N R. Teaching the mental status examination: comparison of three methods. J Med Educ 1982; 57:626-29. P A E G L E R D , WILKINSON E J , D O N N E L L Y MB. Videotaped versus traditional lectures for medical students. Medical Education 1980; 14:387-93. BESWICK W, C O O P E R D , W H E L A N G. Videotape demonstration of physical examination: evaluation of its use in medical undergraduate teaching. Medical Education 1982; 16:197-201. K A U F M A N D M , K A U F M A N R G . Usefulness of videotape instruction in an Academic Department of Neurology. J Med Educ 1983; 58:474-78.
R a i j m a k e r s , M. C a s t r o C a b e z a s , J . A . S m a l , a n d J. v a n G i j n * *
Introduction Summary
The plantar response is a frequently performed diagnostic test in general practice. In the judgement of this response major interobserver variation and bias has been demonstrated. 1,2 In teaching the technique and interpretation of the plantar response a videotape might be particularly useful. We introduced an instructional videotape for medical students in which three main criteria for recognizing a Babinski sign were demonstrated. 3 1) There must be a contraction of the extensor hallucis longus muscle ( E H L ) . This can be reliably checked by inspection of the E H L tendon, which clearly protrudes under the skin when the muscle is active. A n upgoing big toe without E H L contraction can be produced if the foot dorsiflexes as a whole, or can be falsely suggested if the little toes go down. 2) The response should be part of a flexion synergy. The Babinski sign is part of a primitive withdrawal reflex which is seen in full degree during the first year of life and which may again include the upgoing toe response after injury of the pyramidal tract. 4 E H L contraction is therefore pathological only if it occurs synchronously with activity in other (physiological) flexor muscles of the leg. In some subjects the flexion synergy is weak, but usually the tensor fasciae latae can be seen to tighten as a reference.
The efficacy of an instructional videotape about the interpretation of the plantar response was evaluated during a two week neurological clerkship. Experimental groups saw the videotape, control groups did not. All students (n = 65) assessed plantar responses of two to four different patients. Their judgement was compared with that of one senior neurologist. Only the students who had seen the videotape showed a significant improvement in performance on a second test (t-test, t=-2.26, p=0.031). In addition, these students more frequently took account of the flexion synergy (Fisher exact test, p<0.001). Video can be an efficient tool in medical education. Key words: Plantar reflex; Babinski; Instructional videotape.
3) The response must be reproducible. Voluntary withdrawal can be confusing. In the case of a true extensor response, repeated stroking of only a few centimetres of skin will produce each time an approximately similar fraction of toe and leg movements, whereas voluntary withdrawal will be abolished or inconstant. Furthermore, voluntary toe movements tend to hold on longer, for a few seconds after stimulation, and reflex movements do not. Finally, stimulation of the dorsum of the foot, at the lateral part, will
* Part of this work was presented at the Third International Conference on Teaching and Assessing Clinical Competence (Groningen, May 22-24, 1989). * * University Department of Neurology and Department of Medical Education, University of Utrecht, The Netherlands Address for correspondence: Prof. Dr. J. van Gijn, UniversityHospital Utrecht, Department of Neurology, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. Accepted 11-2-91 Clin Neurol Neurosurg 1991. Vol. 93-3
201
usually also produce an extensor response, if present, and most people are less ticklish at that site.
ities: I certainly extensor; II possibly extensor; III neither extensor nor flexor; IV possibly flexor; V certainly flexor.
In this study we tested the efficacy of the videotape in the evaluation of the plantar response. We also evaluated the use of the three criteria by medical students.
The judgement of the students was compared with that of a senior neurologist - the same throughout the study - who had previously examined the same legs, and who applied the same three criteria that were emphasized in the videotape. Differences between the judgement of individual students and that of the expert neurologist were quantified by means of a standardized rating scale. In this scale a mismatch between the two major categories, normal (III, IV, V) and pathological (I, II), was weighted much more heavily than differences within the same category. This differential weighting was designed before the study. The scale intervals were then judged sufficiently equal to warrant the application of parametric tests. For each plantar response examined, a student could gain 1 to 6 points. The highest score corresponds to maximal agreement, the lowest score to maximal disagreement. The test score for each student was computed by averaging the scores for the four patients. At the end of each test the students were asked to complete a questionnaire to evaluate which, if any, of the three aspects of the plantar response they had considered. The unpaired t-test was used for comparing the final test scores and the mean increase in score of students with and without video instruction. Entrance test and final test scores were compared by means of the paired t-test. Chi-square test and Fisher exact test were used to compare the frequencies with which the three criteria were applied in each group.
Materials and methods
Twelve clusters of five to eight fifth-year medical students (total number 65) at the University of Utrecht rotated through the Department of Neurology for a two week instructional course in neurology. This clerkship included a regular series of 5 to 10 instructional videotapes on various subjects in neurology, and also bedside teaching by a senior neurologist. Previously all students had followed a clerkship in internal medicine and pediatrics. In their pre-clinical period they had been exposed to neurological teaching in the form of 60 clinical lectures, followed by an examination, and two 15-hour courses on the neurological examination and on the history in neurological disease. The students were asked to participate on a voluntary basis. A "Solomon four-group design" was applied, with two experimental and two control groups (with and without entrance test).5 The entrance test was similar to the final test, and was included (for half the clusters of students) to measure the baseline level of knowledge. The other half was used to distinguish between an effect of the videotape and a possible effect of the entrance test. Each cluster of students was randomly assigned to one of the four groups. Only in the experimental groups the videotape about the plantar response was included. This videotape lasted approximately 13 minutes; it was shown on day 8 of the clerkship. On day 2 the entrance test was performed, in half of the experimental and control clusters. On day 10 the final test was performed in all groups. In each test the student was asked to examine four randomly selected legs, of four different patients. The students did not receive any additional information about the patients. They performed and evaluated the reflexes and expressed their judgement by choosing between five possibil202
Results
Sixty-five students were involved in this study; 32 were male, and the mean age was 25 years. The entrance test means for the video group (n=14) and non-video group (n=20) were 3.82 (SD + 1.16) and 4.50 (SD + 1.23), respectively (Table 1). This suggests some sampling error, but the difference was not statistically significant. The final test mean in these two groups was 4.76 (SD __. 0.62) for the video group, and 4.35 (SD + 1.17) for the non-video group. The
unpaired t-test revealed no significant difference in final test means between these two groups. But if the analysis is restricted to the students who performed an entrance test, the mean increase in score (final test score minus entrance test score) for the non-video group was -0.15 (SD + 1.52) and for the video group 0.94 (SD + 1.28), which is a statistically significant difference in favour of the video group (t-test, t=-2.26, p=0.031). Pairwise comparison of entrance and final scores showed a significant difference for the video group (paired t-test, t=-2.75, p=0.016). Table 1 Test scores for each group ( + standard deviation). group
non-video non-video video video
number mean of students entrance test score
16 20 15 14
mean final test score
4.56(+0.73) 4.50(+1.23) 4.35(+1.17) 4.56(+0.60) 3.82(+1.16) 4.76(+0.62)
The students in the video group had more often taken the flexion synergy into account in the final test (29 of 29, versus 25 of 36 students in the non-video group; Fisher exact test, p<0.001). The difference between video and non-video was not significant for the subgroups who had an entrance test (chi square: 1.95, n.s.), because the attention for the flexion synergy in the nonvideo group was higher for the students with an entrance test than in those without (Fisher exact test, p<0.01). For the other two recommended criteria for evaluating the plantar reflex, no significant differences were found between control and experimental groups. Discussion
In an effort to reduce the interobserver variation in the judgement of the plantar reflex that has been reported earlier 2 we introduced a videotape in the neurology course for medical students. We chose a videotape for this study in order to eliminate the interindividual variation of teaching by clinicians. Videotapes are often recommended in teaching clinical skills, although their efficacy shows wide differences.61~ In this video we introduced three main criteria for the interpretation of the plantar response.
General application of these three criteria might lead to a more uniform judgement by clinicians. The differences between experimental and control groups were relatively small and the final results were not significantly different. But only in the group of students who saw the video a significant increase in performance was found. That the differences were small can be explained by the fairly high initial knowledge, which limited further rises in performance. The high performance rates in the groups without video indicate that earlier lectures and practical sessions had been quite effective. In addition, the voluntary basis of participation may have selected the more interested students, resulting in a higher level of knowledge at entry. To measure an increase in knowledge a baseline value is necessary. For this purpose we performed an entrance test. Because of the possible influence of the entrance test on the final results we used the "Solomon four-group design". Our finding that the students with an entrance test in the non-video group more frequently observed the flexion synergy in the final test clearly demonstrates an educational effect of the entrance test in itself. This may explain why an additional effect of the video instruction on this aspect of the final test was attenuated. All students who saw the video took account of the flexion synergy, against approximately 70% of students in the non-video situation. Obviously instruction by video is more effective in emphasizing the importance of the flexion synergy than clinical teachers alone. Van Gijn and Bonke 1 reported earlier that this synergy is largely ignored, and that even experienced neurologists may look at the toes only. The criteria about contraction of the extensor hallucis longus muscle and about the reproducibility were often indicated by students, irrespective of whether they had or had not seen the videotape. Apparently these criteria for the plantar reflex are already well known by medical students. Video instruction about the plantar reflex seems particularly appropriate for students with a lower baseline level of knowledge. The time of clinical teachers can be saved to some extent by this method, while the videotape provides a comparable or higher efficiency of learning. The use of this videotape may lead to a better and more 203
uniform interpretation
of the plantar response.
3
Acknowledgements
4
We are deeply indebted to Liesbeth Hamstra, Laetitia de Kort, Ellen Jansen and Robby Ramcharan for the practical organization of the tests. We also thank L.J. Kappelle, J.G.M. Gerritsma and J.C. van Latum for their critical comments on earlier versions of this paper, and H. Frericks for his advice on statistics. The production of the videotape was made possible by a grant from Sandoz b.v.
5
6 7
8
References 1
2
204
Interpretation of plantar reflexes: biasing effect of other signs and symptoms. J Neurol Neurosurg Psychiatry 1977; 40:787. VAN GUN J. The plantar reflex; a historical, clinical and electromyographic study. Meppel: Krips Repro, 1977 (Thesis, Erasmus University, Rotterdam). V A N G I I N J, B O N K E B.
9
10
VAN GUN J. Equivocal plantar responses: a clinical and electromyographic study. J Neurol Neurosurg Psychiatry 1976; 39:275-82. VAN GUN J. The Babinski sign and the pyramidal syndrome. J Neurol Neurosurg Psychiatry 1978; 41:865-73. CAMPBELL D T , S T A N L E Y JC. Experimental and Quasiexperimental Designs for Research and Teaching. Chicago: Rand McNally College Publishing, 1966:24-25. H U N T D D , D A O A D A K I S CS, W A R D N G , RIES J R . Live versus Videotaped Interviews. J Med Educ 1983; 56:916-18. P A N L R, LEWIS R , N I C C O L I N I R, R U B E N S T E I N R. Teaching the mental status examination: comparison of three methods. J Med Educ 1982; 57:626-29. P A E G L E R D , WILKINSON E J , D O N N E L L Y MB. Videotaped versus traditional lectures for medical students. Medical Education 1980; 14:387-93. BESWICK W, C O O P E R D , W H E L A N G. Videotape demonstration of physical examination: evaluation of its use in medical undergraduate teaching. Medical Education 1982; 16:197-201. K A U F M A N D M , K A U F M A N R G . Usefulness of videotape instruction in an Academic Department of Neurology. J Med Educ 1983; 58:474-78.