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Letters to the Editor Indian Pediatrics 1999;36: 1281-1283 |
Brachioradialis Reflex |
| I read with interest the recent communication on this subject(1). I differ from the idea of eliciting the reflex by tapping over the muscle. Brachioradialis reflex is one among the other deep tendon reflexes which are clinically muscle stretch reflexes. The authors have also mentioned that it is a deep tendon reflex and tapping over the muscle will not elicit the same. Myotonia and fasciculations which are muscle oreinted responses are to be identified by tapping over the muscle. Each tendon reflex has got a root value as well as specific localization. Even in children this reflex can be elicited not only at the level just above the styloid process of radius but also along the lower one third of the lateral surface of the radius or at its tendon of origin above the lateral epicondyle of humerus(2). Because the stimulus is mediated through the deeper sense organs such as neuromuscular and neurotendinous spindles, propreoceptive reflexes are produced by indirect stimulation of muscles and calling forth of a response to a sudden stretch imposed upon them. They are Not evoked by direct stimulaton of muscle tissues(2). Biceps, triceps and brachioradialis of upper extremities may be elicited only to a slight extent even in normal adults. If they are conspicuous, one can assume the presence of general reflex exaggeration. Clinical examina-tion is better evaluated if it is universal and is accepted by all. I also feel that the fundamentals of clinical examination are to be precise and accurate and not to be altered by individual's experiences. D. Meikandan, References 1. Kalra V, Mittal R. The brachioradialis reflex. Indian Pediatr 1999; 36: 729. 2. Haerer AF. The reflexes. In: DeJong's The Neurological Examination, 5th edn. Philadelphia, Lippincot-Raven, 1992; pp 429-436. It has been rightly pointed that the upper limb reflexes are sluggish as compared to adults and that is our experience as well. This is especially true of the brachioradialis reflex which is often not elicited even by tapping at the lower one-third of the lateral surface of the forearm or at its tendon of origin above the lateral epicondyle of the humerus in practical clinical examination of children. Reinforcement maneuvres which can increase the positivity of the reflexes are difficult to employ in infants and young children, and mentally subnormal children who would not cooperate in the maneuvre. Hence the upper limb reflexes are by and large elicited with great difficulty in young children, if at all. The responses which are elicited by tapping the muscle directly include: (a) myotonia where there is a contraction of the muscle followed by a delayed relaxation; (b) fasiculation where there is contraction of groups of muscle fibres which may be spontaneous or evoked by tapping the muscle but there is no movement at the joint; and (c) normal contraction where the fibres that are tapped directly, contract(1). This muscle contraction may persist when the stretch reflex is abolished, and hence this method has not been recommended for clinical evaluation. However, a visual observation of these phenomena is quite different from what is observed when the brachioradialis is tapped. The contraction so obtained is very similar to that elicited in a positive stretch reflex. Besides, the authors have also observed that the positivity of this contraction correlates well with the state of the other reflexes; i.e., the reflex is exaggerated if the other reflexes are brisk and diminished or absent in other generalized hyporeflexic states, and this has been mentioned earlier(1). Additionally, the authors have found that this contraction by direct tapping is seen most prominently in the brachioradialis muscle and also in almost all children (as compared to adults). Hence we feel tapping the brachioradialis in children should be tried if conventional method of elicitation of reflex fails. The interpretation may be as follows: (a) if there is no correlation it should be assumed that the reflex is absent; (b) in generalized hyporeflexia, the brachioradialis reflex elicited by muscle tapping should be taken as negative; (c) if there is a brisk contraction and there is generalized hyperreflexia, the reflex is taken as exaggerated; (d) if there is a brisk contraction and the other reflexes are normal, the reflex is taken as exaggerated; and (e) if there is a brisk contraction on one side as compared to the other, the reflex should be taken as exaggerated. While it is true that clinical examinations must be universal and acceptable to all, the search for finding newer ways to improve our evaluation and examination skill should not end. As it is, the reliance on investigations rather than clinical examination for diagnosis has increased greatly during the last decade. Hence any new observations must not be discarded simply because they do not comply with already laid down practice. The authors feel an attempt must be made to evaluate them personally in several patients before labelling it as unacceptable. We would be happy to share the experience of other pediatricians after they have evaluated patients. Veena Kalra, Reference 1. Mayo Clinic and Mayo Foundation. Motor Function Part II. Specific study of msucle. In: Mayo Clinic Examinations in Neurology, 7th edn. Rochester, Mosby, 1998; pp 171-240. |
