Abstract: The present disclosure relates generally to equipment and procedures in the field of surgery and/or diagnostics and, more particularly, to instruments, assemblies and methods for undertaking surgical and/or diagnostic procedures that involve and/or are in proximity to the brain (e.g., cranial procedures and/or surgery). The disclosed assemblies generally include a handle member and an elongated probe that includes an ultrasound transducer. The assemblies may be used in conjunction with K-wires/guidewires, tubular members (e.g., EVD catheters and/or ventricular drains), endoscopes/cameras, and accessory items such as curettes, probes, knives, suction devices, scissors, cautery units, forceps, grasping devices and the like. Advantageous medical diagnostic and surgical instruments, assemblies and methods are provided for use during a broad variety of clinical applications and procedures (e.g.