Ultrasonographic Assessment of Carpal Tunnel Syndrome

Mucopolysaccharidosis are lysosomal storage disorders such as Hunter, Hurler, and Sanfilippo syndromes. These patients have a genetic enzyme deficiency that results in the inability to degrade glycosaminoglycans. The glycosaminoglycans accumulate in lysosomes causing cell enlargement and subsequent dysfunction. The accumulation occurs in all tissues including cartilage, joint capsule, and tendons and can lead to carpal tunnel syndrome, trigger digits, and various other orthopaedic manifestations [Van Heest, White]. These children often suffer from severe cognitive impairment and are often unable to communicate pain or numbness. Carpal tunnel syndrome is almost always present, but may not become apparent until symptoms are severe and loss of function has occurred. The current gold standard for diagnosis consists of electromyographic (EMG) and nerve conduction velocity (NCV) studies under sedation or general anesthetic [Khanna].

Primary Objective: The investigators plan to correlate EMG findings and median nerve cross-sectional area in children with mucopolysaccharidosis. The investigators hypothesis is that ultrasonography of the carpal tunnel in patients with mucopolysaccharidosis will prove to be an effective, reliable, and safe method to evaluate the median nerve, thus avoiding the need for EMG studies and anesthesia.

Secondary Objective: The investigators want to determine the cross-sectional area of the median nerve using ultrasonography in a cohort of healthy children, ages 3-12. The investigators plan to evaluate a cohort of healthy children to determine a normal cross-sectional area of the median nerve.