Ultrasound imaging and directed needle biopsy in the diagnosis of selective involvement in muscle disease.

Four children investigated for neuromuscular disorder by routine ultrasound imaging showed selective involvement within the quadriceps femoris muscle, with involvement of the vasti and sparing of the rectus femoris. This was confirmed by concurrent needle biopsy of the two muscles. Real-time ultrasound imaging is quick, noninvasive, readily accepted by children, and has the advantage over CT scans of being practical for routine outpatient use. Needle biopsy is relatively atraumatic and enables one to select specific superficial and deep muscles for concurrent biopsy.