The floppy infant: a practical approach.

Cerebral, non paralytic and peripheral paralytic hypotonia are briefly discussed. Criteria which help in the differential diagnosis are emphasized. In the usual cerebral hypotonia, muscle strength is preserved but muscle tone is decreased. However, there are a few conditions in which cerebral hypotonia is severe enough to resemble paralytic hypotonia. These conditions include the Prader-Willi syndrome (first phase), the Zellweger syndrome and some cases of congenital myotonic dystrophy. In peripheral or paralytic hypotonia muscle weakness and hypotonia go hand-in-hand. A few practical diagnostic criteria are given which allow the differentiation between anterior horn cell disease, polyneuropathy, neonatal myasthenia and myopathy. Finally, essential or benign hypotonia is briefly alluded to.