Neurologic manifestations of achondroplasia.
Achondroplasia is the best described and most common form of the congenital short-limbed dwarfing conditions. Achondroplasia is apparent at birth and has a birth prevalence of 1 in 20000-30000 live-born infants. Achondroplasia is inherited as an autosomal dominant condition, although 80% of cases occur sporadically as new events in their families. Achondroplasia is caused, in virtually all of the cases, by a G380R mutation in fibroblast growth factor receptor 3 (FGFR3). Patients with achondroplasia should be evaluated by a multidisciplinary team of clinicians including geneticists, neurologists, and orthopedists, since there are numerous bony and neurological complications. The most severe complication results from craniocervical stenosis and medullary and upper spinal cord compression, which can have devastating and even lethal sequelae during early childhood. In subsequent decades, including adolescence, spinal cord and nerve compression are more prominent. The neurological complications of achondroplasia have been recognized in adults for more than a century and are attributed to bony defects, connective tissue structures, or both. Similar neurological complications are now appreciated in infants, young children, and teenagers with achondroplasia. Defective connective tissue elements in achondroplasia frequently lead to ligamentous laxity, which can aggravate the complications associated with bony stenosis. Bony abnormalities are known to cause neurological morbidity and lead to a shortened lifespan. Neurological complications associated with achondroplasia are reviewed, including recommendations for the evaluation and management of these clinical problems.