CLINICAL BOTTOM LINE
How should I apply this information?
The information in this article supports our clinical experience: hypotonia positively correlates with motor delays in children. Therefore, physical therapists need to closely monitor infants with hypotonia for motor delays and intervene appropriately. The authors suggest that nuchal hypotonia was the strongest contributor to lower Bayley II scores, and thus development of head control may be a key motor skill to assess.
What should I be mindful about when applying this information?
The authors of this study should be commended for investigating a difficult question. Hypotonia lacks a specific definition, and although characteristics have been identified,1,2 we also lack specific outcome measures to quantify hypotonia. As a result, the results include subjective assessments of muscle tone for which validity and reliability have not been established. This is a substantial limitation that prevents generalization of these findings. The exclusion of infants with weakness, defined in this study as “reduced antigravity movements and/or decreased active resistance to force exerted by the examiner,” is unclear. Beyond this definition, the authors do not explain how weakness was identified. Hypotonia and decreased strength are considered to be correlated by other authors who have investigated this topic.1–6 Joint hyperlaxity may have influenced hypotonia, yet this was not assessed. In a survey of pediatric occupational and physical therapists, joint hypermobility was the most agreed-upon characteristic of hypotonia.2 Therefore, the lack of specific examination of these 2 issues (weakness and joint hypermobility) suggests caution in applying the results of this study to clinical practice.
Ginny Paleg, PT, DScPT, MPT
Montgomery County Infants and Toddlers Program
Kathy Martin, PT, DHSc
Krannert School of Physical Therapy, University of Indianapolis
1. Martin K, Inman J, Kirschner A, Deming K, Gumbel R, Voelker L. Characteristics of hypotonia in children: a consensus opinion of pediatric occupational and physical therapists. Pediatr Phys Ther. 2005;17:275–282.
2. Martin K, Kaltenmark T, Lewallen A, Smith C, Yoshida A. Clinical characteristics of hypotonia: a survey of pediatric physical and occupational therapists. Pediatr Phys Ther. 2007;19:217–226.
3. Prasad AN, Prasad C. The floppy infant: contribution of genetic and metabolic disorders. Brain Dev. 2003;25:457–476.
4. Hunt PM, Virji-Babul N. Development of a quantitative measure of hypotonia for individuals with Down syndrome: a pilot study. Physiother Can. 2002;54:37–41.
5. Steifel L. Hypotonia in infants. Pediatr Rev. 1996;17:104–105.
6. Jacobson RD. Approach to the child with weakness or clumsiness. Pediatr Clin N Am. 1998;45:145–168.