LETTERS: NEW OBSERVATIONS
Ultrasound-Guided Needle Electromyography for Assessing Diaphragmatic Myoclonus Kai-Hsiang S. Chen, MD,1
Li-Ta Keng, MD,2 Yu-Ting Kuo, BSc,1 Yi-Cheng Tai, MD,3 and Robert Chen, MA, MBBChir, MSc, FRCPC4,5,6,*
Diaphragmatic myoclonus is a rare movement disorder, and the diagnosis could be conﬁrmed only by diaphragmatic needle electromyography (EMG).1 Here, we introduce ultrasound-guided needle EMG to improve the accuracy and safety of the procedure. A 64-year-old woman reported involuntary, intermittent abdominal movements for 1 year. They caused mild respiratory discomfort such as shallow breathing without shortness of breath. They occurred almost all the time while awake but were absent during sleep. The abdominal jerks could not be suppressed voluntarily but were transiently reduced during deep inspiration. Neurologic examination showed abdominal contractions with jerk-like movements (Video S1) and was otherwise normal. Brain and cervical magnetic resonance imaging and electroencephalogram were unremarkable. We performed the ultrasoundguided needle EMG to conﬁrm the diagnosis. With the patient in the left decubitus position, an ultrasound transducer (Philips iE33, Cambridge, MA) was placed at the intercostal space between the right eighth and ninth ribs on the posterolateral chest wall, with the long axis parallel to the rib direction. The position and direction of the transducer was adjusted to ensure that lung tissue was not close to the needle trajectory during inspiration to decrease the risk of inadvertent pneumothorax. The needle EMG was inserted at a 45 angle from the right edge of the ultrasound transducer in-plane to the transducer view and was monitored real time with ultrasound. The EMG was recorded continuously (sampling rate 48 kHz, ﬁlter 10–2000 Hz; Sierra Summit, Cadwell Industries, Kennewick, WA). The diaphragm was visualized at a depth of 2 to 4 cm as a horizontal hypoechoic band with hyperechoic margin beneath
intercostal muscles, which has hypoechoic appearance with surrounding hyperechoic fascia. The diaphragm could be conﬁrmed by increasing thickness during inspiration, contrasting with the adjacent lung and liver tissues. Indentation of the liver surface synchronized with respiration and EMG bursts ﬁring ensured that the needle tip was within the diaphragm but not piercing the hepatic capsule (Fig. 1A). Irregular, short bursts (~50–150 milliseconds) of abnormal EMG activities at the frequency around 1 Hz occurred between or within normal diamond-shaped diaphragmatic EMG bursts associated with inspiration (Fig. 1B). The abnormal EMG bursts were suppressed when the patient took deep breaths, but were not entrained or suppressed while performing 2 Hz tapping of the left hand. This EMG ﬁndings conﬁrmed the diagnosis of diaphragmatic myoclonus. Although it has been suggested that diaphragmatic motion can be assessed with ultrasound alone,2 EMG provides high temporal resolution to evaluate EMG burst durations and timing between bursts, which are important in distinguishing myoclonus from other movements. Although previously described techniques involve inserting the EMG needle from the anterior chest wall using anatomical landmarks,3,4 ultrasound guidance provides visual conﬁrmation that the needle is in the diaphragm, which improves accuracy and safety. The liver indentation sign is a novel ﬁnding and has not been reported in literature. No further needle advancement was made once liver indentation appeared to reduce the risk of liver puncture. Although appearing safe in our case, further studies are required to afﬁrm the efﬁcacy and safety of the procedure.
Department of Neurology, National Taiwan University Hospital Hsin-Chu Branch, Hsin-Chu, Taiwan; 2Department of Internal Medicine, National Taiwan University Hospital Hsin-Chu Branch, Hsin-Chu, Taiwan; 3Department of Neurology, E-Da Hospital, I-Shou University, Kaohsiung, Taiwan; 4Krembil Research Institute, University Health Network, Toronto, Ontario, Canada; 5Division of Neurology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada; 6 Edmond J. Safra Program in Parkinson’s Disease, University Health Network, Toronto, Ontario, Canada *Correspondence to: Dr. Robert Chen, 7MC-409, Toronto Western Hospital, 399 Bathurst Street, Toronto, Ontario, M5T 2S8, Canada; E-mail: [email protected]
Keywords: diaphragmatic myoclonus, electromyography, ultrasound. Relevant disclosures and conﬂicts of interest are listed at the end of this article. Received 15 April 2020; revised 22 July 2020; accepted 27 July 2020. Published online 1 September 2020 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/mdc3.13043
MOVEMENT DISORDERS CLINICAL PRACTICE 2020; 7(7): 870–871. doi: 10.1002/mdc3.13043 © 2020 International Parkinson and Movement Disorder Society
LETTERS: NEW OBSERVATIONS
CHEN K.-H.S. ET AL.
Disclosures Ethical Compliance Statement: Verbal and written informed consent were obtained from the patient for gathering medical information and videos using approved forms from the National Taiwan University Hospital Hsin-Chu Branch Institutional Review Board. We conﬁrm that we have read the Journal’s position on issues involved in ethical publication and afﬁrm that this work is consistent with those guidelines. Funding Sources and Conﬂict of Interest: The authors report no sources of funding and no conﬂicts of interest. Financial Disclosures for the Previous 12 Months: The authors declare that there are no disclosures to report.
References 1. Chen R, Remtulla H, Bolton CF. Electrophysiological study of diaphragmatic myoclonus. J Neurol Neurosurg Psychiatry 1995;58(4):480–483. 2. Ramos VFML, Considine E, Karp BI, Lungu C, Alter K, Hallett M. Ultrasound as diagnostic tool for diaphragmatic myoclonus. Mov Disord Clin Pract 2016;3(3):282–284. 3. Saadeh PB, Crisafulli CF, Sosner J, Wolf E. Needle electromyography of the diaphragm: a new technique. Muscle Nerve 1993;16(1):15–20. 4. Bolton CF, Grand’Maison F, Parkes A, Shkrum M. Needle electromyography of the diaphragm. Muscle Nerve 1992;15(6):678–681.
FIG 1. (A) Ultrasound image of the diaphragm and liver. The diaphragm is about 2 mm thick. The red arrow indicates the electromyography (EMG) needle shaft, and the white arrow indicates the needle tip–induced indentation on the liver surface. (B) Diaphragmatic EMG recording. The red arrowheads indicate the normal inspiratory EMG activities, the green arrowheads show examples of myoclonic EMG bursts, and the green circles show the myoclonic bursts interrupting normal inspiratory EMG activities.
Author Roles (1) Research Project: A. Conception, B. Organization, C, Execution; (2) Ultrasound-Guided Electromyography Study: A. Performance, B. Formatting; (3) Manuscript: A. Writing of First Draft, B. Review and Critique. K.H.-S.C.: 1A, 1B, 1C, 2A, 2B, 3A L.T.K.: 1B, 1C, 2A Y.-T.K.: 1C, 2B Y.-C.T.: 1A, 1B R.C.: 1A, 3B
Supporting Information Supporting information may be found in the online version of this article. Video S1. This video contained six segments. Segment 1 shows semiregular abdominal contractions with minimal respiratory distress. Segment 2 shows how to position the ultrasound transducer and the way to insert the needle EMG. Segment 3 shows the abnormal EMG bursts during normal breathing. Segment 4 shows no myoclonic bursts when the patient took deep breaths. Segment 5 shows no entrainment or distraction of the diaphragmatic myoclonus EMG burst when the patient performed left wrist tapping at 2 Hz. sEMG , surface EMG. Segment 6 shows the ultrasound real-time monitoring of the location of EMG needle. The indentation of liver surface by the needle tip during inspiration assured the needle was within the diaphragm. The needle is labeled with a green arrowhead, the liver indentation is marked with a red arrowhead, and the thickness of the diaphragm is labeled with a yellow arrowhead.
MOVEMENT DISORDERS CLINICAL PRACTICE 2020; 7(7): 870–871. doi: 10.1002/mdc3.13043