Needle Electromyography: Hemorrhagic Risks and Complications

Abstract & Commentary

By Michael Rubin, MD, FRCP(C), Professor of Clinical Neurology, Weill Cornell Medical College, New York, NY. Dr. Rubin receives grant/research support from Pfizer and is on the speaker's bureau of Athena Diagnostics.

Synopsis: Needle EMG is a safe procedure in patients who are taking antiplatelet or warfarin therapy.

Source: Lynch SL et al. Complications of needle electromyography: Hematoma risk and correlation with anticoagulation and antiplatelet therapy. Muscle Nerve 2008;38:1225-1230.

Is there an increased risk of hematoma formation following needle electromyography (EMG) in patients on aspirin, clopidogrel, or warfarin? To address this question, adult patients undergoing EMG of the tibialis anterior muscle, as part of a routine lower extremity EMG, were enrolled in a prospective, case-control study undertaken at the Mayo Clinic Electromyography Laboratory. Post-EMG ultrasound examination of the tibialis anterior muscle was central to the study design, and hence, embedded metal in proximity to the tibialis anterior was criteria for exclusion. Participating patients completed a questionnaire addressing medication use, including herbal supplements and potential blood thinners. Following needle EMG of the tibialis anterior muscle, ultrasound of the muscle was performed to ascertain the presence and size of hematoma, if any. Needle EMG was performed by a supervised resident, fellow, or attending, following standard technique, using a concentric 50 mm needle directed in a straight line along 3 different tracks, following which the needle was removed and firm pressure applied to achieve hemostasis. Informed consent and HIPAA authorization were obtained in all instances. Fisher's exact test provided statistical analysis.

Among 209 enrolled patients, 101 were on warfarin with an INR > 1.4 (range, 1.5-4.2), 57 were on antiplatelet agents (aspirin, clopidogrel, or both), and 51 served as control subjects. Among the warfarin patients, 80 had an INR of 2.0 or more and 27 had an INR of 3.0 or more. No control patient had ultrasound evidence of hematoma, and only 1 aspirin/clopidogrel patient and 2 warfarin patients had subclinical hematoma. No statistically significant difference was appreciated between the groups. All hematomas were asymptomatic, with no evidence of bruising or swelling at the needle entry site following the study. Long-term follow-up of medical records at 3-15 months similarly reported no complaints of pain following the EMG. Needle EMG rarely causes hematoma formation. It may be safely performed even in patients on warfarin with INR in the therapeutic range.

Commentary

Patients with lymphedema or prosthetic joints represent two other situations in which the safety of needle EMG is brought into question. Lymphedema may follow lymph node dissection or radiation, and patients are often cautioned to avoid any percutaneous procedure in the affected limb, including venipuncture due to the risk of infection. Prosthetic joints may become infected due to hematogenous spread of bacteria as may occur following dental procedures or gastrointestinal studies, and possibly needle EMG. Guidelines issued by the American Association of Neuromuscular and Electrodiagnostic Medicine state that, based on the medical literature, no contraindication to needle EMG exists in either of these conditions.1 Nevertheless, clinical judgment should be exercised to determine whether the information to be obtained outweighs the risk of complication.

Reference

1. American Association of Neuromuscular and Electrodiagnostic Medicine. Needle EMG in certain uncommon clinical contexts. Muscle Nerve 2005;31:398-399.