A recent article in Muscle & Nerve, 2019, Vol. 6, by Jothi and Bland, just published solely involved 20 people with use of a splint and ultrasound and 20 people with the splint and no ultrasound.  It showed no added benefit in the symptomatic relief gained with the use of a splint upon adding ultrasound. 

Ultrasound is getting a lot of attention lately mostly for the use of diagnosis.  This is the case where it is being used in an attempt to add treatment benefit unsuccessfully.  I am not surprised that no added benefit has been demonstrated. Surgery, and usually endoscopic carpal tunnel release (ECTR), offers the most reliable solution for carpal tunnel syndrome.  This is based upon the proved fact carpal tunnel syndrome is related to elevated pressure in the tight space in the carpal tunnel as the nerve goes from the lower end of the forearm into the palm of the hand.