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ORIGINAL ARTICLE |
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| Ahead of print
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False negativity in towel test for elbow flexion assessment in brachial plexus birth palsy. Can we attribute to handedness?
Terrence Jose Jerome
Department of Orthopedics, Hand and Reconstructive Microsurgery, Olympia Hospital & Research Centre, Trichy, Tamil Nadu, India
| Date of Submission | 20-Jun-2020 |
| Date of Acceptance | 06-Aug-2020 |
| Date of Web Publication | 12-Jul-2021 |
Correspondence Address:
Terrence Jose Jerome,
Department of Orthopedics, Hand and Reconstructive Microsurgery, Olympia Hospital & Research Centre, 47, 47A Puthur High Road, Puthur, Trichy 620017, Tamil Nadu.
India
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/jpn.JPN_162_20
 Abstract | | |
Objectives: The towel test is considered as a reliable clinical examination finding to test the elbow flexion in Brachial plexus birth palsy. A mature central nervous system makes this test positive at 6 months’ time and those who failed the test require microsurgical exploration and nerve repair/transfers for upper limb functions. Not all infants pass in this test. Majority of the children develop a clear hand preference at 6 months of age. We hypothesize the validity of the towel test in brachial plexus birth palsy children between 6 and 9 months of age and the possibility of mother and infant handedness in the false-negative tests. Materials and Methods: A retrospective analysis conducted between 2015 and 2019 about the utility of “towel test” involving 12 boys and 11 girls was analyzed and interpreted. The side involved in these infants and the mother’s handedness was also noted. Based on the age, side, gender, and mother-handedness, the results of towel tests were statistically interpreted. Results: The mean age of the infants involved was 6.6 months (range 6–9 months). Twenty children (87%) had positive tests. Three (13%) infants (male = 2; female = 1) had false-negative test. There was no action on the normal side to remove the towel but weak movements in the affected upper limb persisted to try and remove the towel. The left-hand mother’s infant had false-negative towel test, which was found statistically significant (P < 0.01). Conclusion: Clinicians should know that false negativity may coexist while using the towel test and handedness could be a possibility in them. In such conditions, additional tests can be used to assess the ongoing motor recovery in brachial plexus birth palsy children between 6 and 9 months of age.
Keywords: Brachial plexus birth palsy, false negativity, handedness, towel test
| Introduction | |  |
Brachial plexus birth palsy is a common injury affecting 1–4 children per 1000 live births.[1] It is diagnosed shortly after birth due to the absence of active movement in the shoulder, elbow, wrist, and fingers. Subsequently, the mother notices subjective improvement and the clinicians diagnose motor improvements using certain standard tests and assessment tools. Bertelli and Ghizoni[2] described a simple “towel test” to assess the elbow flexion in infants less than 9 months of age. Many surgeons including the author have noticed shortcomings in the test and could not be used as a reliable test in the clinical examinations. Of the total world’s population, 10% are left-handed.[3] Majority of the children develop a clear hand preference at 6 months of age.[4] The effect of handedness on child development can affect the test and the results. We hypothesize the validity of the towel test in brachial plexus birth palsy children between 6 and 9 months of age and the possibility of handedness in the false-negative tests.
| Materials and Methods | | |
A retrospective analysis conducted between 2015 and 2019 about the utility of “towel test” involving 12 boys and 11 girls was analyzed and interpreted. The side involved in these infants and the mother’s handedness was also noted. The infants were assessed in the supine position and the pictures and videos were taken with parent’s consent. The child’s face was covered with a towel and if the child removed the towel from the face then the test was considered positive and negative if there was no such action. We repeated the test three times in the outpatient clinic with an interval of 10 minutes in a comfortable child. Of three tests, if the child performs the towel test more than one occasion it was considered positive. A positive test confirmed the shoulder flexion, elbow flexion, and extension and finger movements. Based on the age, side, gender, and mother-handedness, the results of towel tests were statistically interpreted. Qualitative (gender, side) and quantitative variables (age) were evaluated using a t test. A comparison of the variables was done using the chi-square test. Two-tailed P values of 0.05 or less were considered significant [Table 1]. The study was approved by the Ethical Board Committee and the consent was obtained from the parents. The mother details were collected during their visit to the hospital.
| Results | | |
The mean age of the infants involved was 6.6 months (range 6–9 months). Fifteen had right side and eight had left side involvement [Table 2]. Twenty children (87%) had positive tests. Three (13%) infants (male = 2; female = 1) had no action in the normal side but weak movements in the involved upper limb despite testing three times in a row [Figure 1]. In addition, the mother also confirmed the absence of normal upper limb movement at their home with the towel test. Of these three infants, two mothers were left-handed and one was right-handed. These infants' normal (uninvolved) upper limb was examined by the pediatrician, neurologist, and the author on several occasions and found clinically normal [Figure 2]. These infants were also made to play with toys, rattles and bells, cookies and found to have normal function. There were weak movements in the involved side trying to remove the towel but no active motion on the normal side. Instead, all three children try and rotate the face and the body towards the involved side without attempting to remove the towel by the normal hand. This could be a reverse of the towel test in these patients and considered a false negative towel test [Video 1].  | Figure 1: Six-month-old boy with left-side brachial plexus birth palsy involving C5, 6 and 7 nerve roots with weak hand function. There is no Horner’s syndrome. Towel test shows no movement at the normal right upper limb but weak and attempted shoulder abduction in the involved left upper limb. The mother was left-handed
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 | Figure 2: Normal movements and functions in the right upper limb without a towel. No movements with towel
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Age (P = 0.6), side involved (P = 0.1), and gender (P = 0.58) have no statistical significance with the results of the towel test. But the left-hand mother has statistical significance (P < 0.001) in influencing the results of the towel test.
| Discussion | | |
Brachial plexus birth palsy will recover in 66 to 92% of children spontaneously within the first 2 months of life and, therefore, have no long-term sequelae.[5] The children are given a passive range of motion exercises during this time and who do not recover spontaneously by 2 months of age are likely to have permanent motor deficits, or alteration in function (10–30%).[6] There have been various tests and scores to assess the ongoing motor recovery such as Modified Mallet Scores, Toronto Score Test, and Active Movement Score (AMS). No scoring system is comprehensive, and it is very difficult to correlate or compare them.[6]
The most important single prognostic sign is the recovery of elbow flexion and simple test to determine this can focus the surgeon about the child’s recovery pattern. Besides, electromyography can predict the flexion recovery, it has overestimation as a potential disadvantage.[7] The absence of elbow flexion at 3–9 months is an important criterion to operate.[8],[9] Physical examinations like a hand to mouth (cookies test), active range of movements, and Medical Research Council (MRC) grading are all validated to assess the elbow flexion and detect biceps contraction in infants with brachial plexus birth palsy.[10]
Thomas and Dargassie[11],[12] described the “hand to face test” during their study of normal child development. The child’s face is covered with a towel and the ability to remove the towel at 5 months (40%), 6 months (80%), 7 months (95%), and 9 months (100%) are found in the study.[12] Children of 9 months of age have 100% ability to remove the towel from the face by their elbow flexion assisted with shoulder and hand movements.
Bertelli and Ghizzoni[2] described the towel’s test to assess the shoulder flexion, elbow flexion, and extension, finger flexion, and extension by keeping a towel over the child’s face where the child removes the towel from the face. The towel removal is done by the uninvolved (normal side) limb whereas the affected side fails in doing this maneuver. The goal of the test was to induce motion and provoke arm movements. The ideal age to perform this test is 6–9 months where the primitive reflexes are replaced by voluntary movements in children. Age (P = 0.6), side involved (P = 0.1), and gender (P = 0.58) have no statistical significance with the results of the towel test in our study.
Further, the test was very useful and reliable in 87% (n = 20) of the infants where the normal hand removed the towel quickly and the affected side failed because of weak or absent biceps contraction. But in 13% (n = 3), the normal hand did not remove the towel despite three attempts and normal neuromotor functions. The affected limb attempts to remove the towel. This made our observations to rethink about the validity and reliability in assessing the elbow flexion in a child between 6–9 months. These three children had false-negative towel test, where the left hand tried to remove the towel with shoulder abduction and poor elbow flexion and hand functions.
Handedness has been widely studied in disciplines ranging from psychology to medicine and in all fields of clinical relevance. The impact of handedness on children’s cognitive development is largely studied including health, attitudes, and social adjustments.[13] There are numerous theories to predict the differences in the cognitive abilities of left and right-handed individuals. Many authors have argued general cognitive disadvantage for left-handed individuals[14] and low level of achievements in them.[15] In addition to genetic effects, reduced cognitive performance in left-handers could be the result of brain pathology, perinatal brain insults, bacterial meningitis, females, older mothers, and birth asphyxia.[16],[17],[18] Overall, there is no difference between left and right-handers for tests of mental rotation, 3D drawing ability, and spatial visualization.[19]
There is an interesting link between brain pathology and handedness with genetic components passed by left-hand mothers.[20] Two mothers in our study who were left-handed had their baby failed in the towels test. We surmise that the left-handedness of the baby could be the reason for towel test failure. From this study, we inferred that left-hand mother has significant influence over the handedness of the growing baby. (P < 0.01) In such patients towel tests with the left side, involvement may have false-negative results. The child may try to use the left hand even if it is affected by brachial plexus birth palsy and does not use the normal right upper limb to remove the towel. The left-handed population accounts for 10%–12% in the world’s total population and may vary between the countries.[3] Girls are less likely to be left-handed than boys. Majority of the children develop a clear hand preference at 6 months of age[4] and further rate of development is variable.[21] In utilizing the towel test as a diagnostic modality to assess the elbow flexion in an infant between 6–9 months age, false negativity and handedness should be borne in every surgeons’ mind. In such conditions, where false negativity arises and infants of left-hand mothers, other modalities of assessment can be tried. The active motion scale (AMS)[22] can be an alternate assessment tool where a child can be provoked to grade the movements on a scale of 0–7.
The limitation of our study was a retrospective observational study with a small sample size. In addition, an EMG would have helped the author to assess the normal side biceps and affected biceps activity during the false-negative towel test. For futuristic reasons, it would be interesting to follow up with these children to determine whether their hand preference has been established as same and whether towel test could predict the handedness earlier.
| Conclusion | | |
As there is 13% false negativity in the “towel test,” surgeons should be aware while assessing the elbow flexion recovery in brachial plexus birth palsy. Left-handedness may be genetically transmitted from their left-hand mothers. one should always include the handedness of the mother during the evaluation of the brachial plexus birth palsy assessment. EMG may help in these false negativity cases, but it can overestimate the biceps recovery. Additional tests and scores will definitely help in these circumstances.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| References | | |
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[Figure 1], [Figure 2]
[Table 1], [Table 2]
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