On long-term follow up, cerebral palsy and mental retardation turn out to be the 2 most common causes of FIS. This review focuses on neuromuscular causes of FIS. [ncbi.nlm.nih.gov]

A few are: Brain damage due to lack of oxygen right before or after birth Problems with the way the brain formed in the womb Disorders that affect nerves Achondroplasia Spinal cord injury Cerebral palsy Severe infections Hypotonia isn’t always a sign [webmd.com]

When your baby can’t control her neck muscles, her head will fall forward, backward, or to the side. Feeling limp, especially when you lift her. [webmd.com]

Breastfeeding Handbook for Physicians 2006). Lawrence, R.A. & Lawrence, R.M. Breastfeeding: a guide for the medical profession (Elsevier Mosby, Maryland Heights, MO, 2011). Prime,D.K. et al. [medela.de]

A child with benign congenital hypotonia may not need any therapy, although she may need to see a doctor for related problems, such as joint dislocation. [webmd.com]

With the advent of molecular diagnosis, a few conditions can be diagnosed by DNA analysis of the peripheral lymphocytes (myotonic dystrophy, spinal muscular atrophy); however, for the most part, electrodiagnostic studies and muscle biopsy remain as essential [ncbi.nlm.nih.gov]