Abstract
Hypotonia in infants can be a confusing clinical presentation leading to inaccurate evaluation and unnecessary investigations. Hypotonia can result from a variety of central or peripheral causes. Therefore, hypotonia is a phenotype of many clinical conditions with variable prognosis. It is important to recognize that hypotonia is not equivalent to weakness. Infants with central causes, such as Down syndrome, may have severe hypotonia with normal muscle strength. Peripheral hypotonia is frequently associated with weakness, which can be predominantly distal in neuropathies or predominantly proximal in myopathies. In general, central hypotonia is much more commonly encountered; however, the prognosis is worst for hypotonia secondary to neuromuscular pathology. The distinction between central and peripheral hypotonia is therefore critical for proper evaluation and management. Stepwise and accurate assessment is very important to reach the correct diagnosis promptly. In this review, I present a concise clinical approach for evaluating the hypotonic infant. Some practical tips and skills are discussed to improve the likelihood of obtaining an accurate diagnosis. Reaching a specific diagnosis is needed for providing appropriate therapy, prognosis, and counseling.