Congenital hypotonia: clinical and developmental assessment

Identifying the underlying cause of congenital hypotonia remains difficult, despite advances in diagnostic laboratory and imaging techniques. Clinical evaluation strategies and standardized developmental tests can assist in differentiating hypotonia resulting from primary involvement of the upper motoneuron (central hypotonia) versus that involving the lower motoneuron and motor unit (peripheral hypotonia). This is especially important in infants with idiopathic hypotonia. This review outlines and describes the components of the clinical assessment: detailed infant and family history, clinical techniques and characteristics for differentiating hypotonia of central versus peripheral origin, and clinical evaluation (muscle tone, primitive reflexes, deep tendon reflexes, etc). Recent research that has contributed to the differential diagnosis of congenital hypotonia is reviewed and directions for future research are provided. Ideally, the assessment of infants with congenital hypotonia is best accomplished by an interdisciplinary team of developmental specialists including pediatricians, medical geneticists, child neurologists, and physical or occupational therapists.