超音波検査技術

Purpose: Spontaneous anterior interosseous nerve paralysis (sAINP) is a rare disease with sudden onset that causes difficulty in flexing the interphalangeal joint of the thumb and index finger. Improvement in most cases is achieved with conservative treatment and subsequently with surgery, such as interfascicular neurolysis, 3–6 months after onset if no improvement is observed. Although sAINP often presents with hourglass-like constrictions in some fascicles of a median nerve trunk, these findings are rarely detected with an imaging modality and are only identified during surgery. Recently, the development of ultrasonography (US) has facilitated detection of these constrictions on ultrasonography. The aim of this study was to evaluate the usefulness of US for sAINP.

Subjects and Methods: Four patients clinically diagnosed with sAINP underwent US at our institution between July 2015 and October 2017. US was performed to observe nerve fascicles in the median nerve trunk within 10 cm proximal from elbow flexion level and to identify fascicular constriction with an 18 to 24 MHz linear probe.

Results and Discussion: US revealed hourglass-like constrictions in all cases at one to two positions in one or two fascicles. In three of four cases, surgery was performed and the constrictions were confirmed at two positions in one fascicle. US revealed maximum constriction at the US marked position in all three cases and follow-up US revealed an improvement in constrictions, following surgery. However, one minor constriction in one patient was not detected.

Conclusion: Thus, this study suggests that US is useful for diagnosing sAINP and can therefore aid in determining the treatment strategy, and follow-up observation required.