Recommendations for Ultrasound Guidance for Diagnostic Nerve Blocks for Spasticity. What Are the Benefits?

Abstract

The diagnostic nerve block (DNB) for spasticity is the percutaneous application of an anesthetic to an individual peripheral nerve trunk (mixed motor sensory nerve), nerve branch to a muscle or an intramuscular branch. The DNB causes a temporary paralysis to assess the contribution of muscle(s) on the spastic pattern and may unmask a fully or partially increased joint range of motion. The anesthetic literature supports the use of ultrasound (US) guidance to improve nerve blocks for sensory targets. This communication summarizes the potential advantages that support the use of US to improve DNB technique. Nerves are much smaller than muscle targets and have various known innervation patterns. US allows for rapid localization of the target before injection, particularly in complex anatomy patterns. The nerve trunks are typically found adjacent to or encapsulating blood vessels, which can be quickly identified with or without color Doppler, allowing the clinician to scan from the vessels to the target and avoid intravascular injection. Lower stimulation levels can be used as the targeted muscle(s) can be seen stimulating rather than only on the surface. A shorter needle insertion time and lower stimulation levels should cause less discomfort to the patient. Smaller volumes of anesthetic may be used as the fluid is seen reaching its target and cessation of stimulation is observed. Further study is needed to identify evidence supporting US utilization with electrical stimulation in DNBs for spasticity management, as US use during nerve blocks for perineurial anesthesia has demonstrated improved patient safety and procedural efficiency.