| 제목 |
Ultrasound-Guided Electromyography Needle Placement in External Anal Sphincter |
| 소속 |
College of Medicine, The Catholic University of Korea, Department of Rehabilitation Medicine1, Seoul St. Mary2 |
| 저자 |
Dong Yoon Park, M.D1*, Yeon Gyu Choi, M.D2, Joo Hyun Park, M.D., Ph.D 2† |
Introduction: Anal sphincter needle electromyography (EMG) is useful tool to evaluate various neurologic lesions such as cauda equine lesion and sacral plexopathy. Conventional technique is often challenging to perform anal sphincter EMG in clinical practice because of the small size of anal sphincter muscle and variation of anatomical land marks. Accurate and precise needle placement into external anal sphincter (EAS) can be done with ultrasound. We preliminarily observed the EAS in one healthy volunteer and identified the EAS muscle in static and dynamic examination for proper transducer placement. Ultrasound-guided EAS needle placement was conducted in the cadaver models to evaluate its accuracy.
Methods: Preliminary study was conducted to investigate the ultrasound image of EAS and proper transducer locations. The only one case of the EAS of 33 year-old healthy volunteer was identified including dynamic exam. After the preliminary study, ultrasound-guided needle placement was performed in cadavers. The 12 side of the EAS in 6 fresh cadavers were involved. The average age was 69.3 years old (range 55 - 80 years). Four of them were females and the other two were males. The cadavers were placed in the lateral recumbent position. A hockey stick transducer was placed on the left side of perianal area in the coronal plane. When the transducer was placed, the handle of it was naturally tilted toward contralateral buttock because of normal hump of buttocks. Then, the transducer was rotated by perpendicular to the coronal plane and tilted the handle of the probe medially about 45 degrees to get inside to outside view (Fig. 1). The probe was moved from lateral to medial side while observing the EAS. After the EAS was identified by ultrasound, the wire placement under real time ultrasound guidance was performed. 1.5inch 21 gauge needles containing 26 gauge florist wires with a hooked end were used. The wires were hooked at the end so that the wire could be firmly lodged inside the muscle. The needle with fine wire in it pierced the posterior side of the skin and proceeded to the EAS. After confirming that the tip of needle is located in the EAS, the needle is withdrawn to stay the wire with a hooked end inside the EAS (Fig. 2). The tissues were dissected to figure out the accuracy of the fine wire placement and other structure invasions. Accuracy in this study was defined as the percentage of the cases in which the tips of the wires were located inside the EAS.
Results: The accuracy was 91.7% (11 of 12 sides) in cadaver models (Fig. 3). The tip was located outside the muscle in the one case and located in the subcutaneous tissue. No anal mucosa or internal anal sphincter invasion was observed.
Conclusions: Ultrasound-guided needle EMG of the EAS was proven accurate and safe in cadaver and expected to be used in clinical practice. The authors recommend that further studies in vivo with large number of cases are needed.
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Schematic illustration of perianal area in the lateral recumbent position and the ultrasound transducer. Rectangle indicates transducer in the short axis (a) and long axis (b) views.
The ultrasound image of the EAS(arrowheads) of the healthy volunteer in short axis (A) and long axis view (B). Ultrasound guided needle placement was performed (C) in cadaver.
Dissection image of the cadaver. The tip of the florist wire was located in the left side of the EAS (asterisk).
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