Letters to the Editor

Letters to the Editor

Indian Pediatrics 1999;36: 1280-1281

Brachioradialis Reflex

Kalra and Mittal(1) describe the difficulty in eliciting the brachioradialis reflex by conventional methods and propose an alternative method of elicitation. As far as the difficulty in elicitation of brachioradialis reflex is concerned, it is known that young children tend to have brisk reflexes in the legs than in arms and many normal children have upper limb reflexes which are sluggish by adult standards(2) and this may be more true of brachioradialis reflex. However, an apparently absent reflex may become normal when reinforcement maneuvres like clenching of teeth are employed(2,3). and this technique must be attempted before a reflex is labelled as being absent. Occasionally, persons are encountered who are otherwise in perfect health, but show sluggish or absent reflexes(3). Therefore a complete absence of a tendon reflex in itself cannot be regarded as abnormal and has to be correlated with observations on the neurological examination before it can be considered to be indicative of disease(3).

Elicitation of a deep tendon reflex by direct percussion of a muscle is not appropriate, has no value in neurological diagnosis and is to be avoided(4,5). There are several fallacies of this techniques. Elicited in this manner, it probably cannot be called a tendon or stretch reflex! All normal muscles contract in response to direct mechanical stimulation like percussion(4-6), the so called idiomuscular contraction or myotatic irritability and only those fibres that have been tapped directly contract(5). Moreover, even when a tendon reflex is truly absent, the muscle may remain excitable to direct percussion(5). In fact, there is an increased muscular response to direct stimulation for a short period after the nerve supply has been severed. This pheno-menon may persist until atrophy has taken place(4). Direct percussion of muscle will elicit a prompt and sustained contraction but a delayed relaxation in a person who has underlying myotonia(4-6) and it may be regarded as a positive (rather exaggerated) tendon reflex, which in fact, it is not. Therefore, a (brachioradialis) reflex elicited by direct percussion of the muscle, may in fact be a false positive with all its implications in the diagnosis and/or localization of the neurological disorder. Hence this alternative technique of eliciting a tendon reflex by direct stimulation of muscle can not be recommended.

Jatinder S. Goraya,
Senior Lecturer,
Department of Pediatrics,
Governemnt Medical College Hospital,
Sector 32, Chandigarh 160 047, India.

References

1. Kalra V, Mittal R. The brachioradialis reflex. Indian Pediatr 1999; 36: 729.

2. Brett EM, Normal development and neurological examination beyond the newborn period. In: Pediatric Neurology, 2nd edn. Ed Brett EM. Edinburgh, Churchill Livingstone 1991; pp 27-52.

3. Mayo Clinic and Mayo Foundation. Reflexes. In: Mayo Clinic Examinations in Neurology, 7th edn. Rochester, Mosby, 1998; pp 241-254.

4. Haerer AF. The reflexes. In: DeJong's The Neurological Examination, 5th edn. Philadelphia, Lippincott - Raven, 1992; pp 429-432.

5. Mayo Clinic and Mayo Foundation. Motor Function Part II. Specific study of muscle. In: Mayo Clinic Examinations in Neurology, 7th edn. Rochester, Mosby, 1998; pp 171-240.

6. Adams RD, Victor M. Principles of clinical myology: Diagnosis and Classification of Muscle Diseases. In: Principles of Neurology. New York, Mc Graw - Hill Inc, 1993; pp 1184-1198.