47 Williams S, et al. Pract Neurol 2017;17:47–50. doi:10.1136/practneurol-2016-001463 HOW TO DO IT How to do it: bedside ultrasound to assist lumbar puncture Stefan Williams, 1 Modar Khalil, 2 Asoka Weerasinghe, 3 Anu Sharma, 4 Richard Davey 5 1 Department of Neurology, Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Leeds, UK 2 Department of Neurology, Hull and East Yorkshire Hospitals NHS Trust, Hull, UK 3 Department of Emergency Medicine, Mid-Yorkshire NHS Trust, Dewsbury, UK 4 Department of Anaesthesia, Mid-Yorkshire NHS Trust, Dewsbury, UK 5 Department of Neurology, Harrogate and District NHS Foundation Trust, Harrogate, UK Correspondence to Dr Stefan Williams, Department of Neurology, Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK; stefanwilliams@doctors.org.uk Accepted 22 October 2016 To cite: Williams S, Khalil M, Weerasinghe A, et al. Pract Neurol Published Online First: [ please include Day Month Year] doi:10.1136/ practneurol-2016-001463 ABSTRACT For many neurologists, lumbar puncture is the only practical procedure that they undertake on a regular basis. Although anaesthetists and emergency physicians routinely employ ultrasound to assist lumbar puncture, neurologists do not. In this article, we outline the technique that we use for an ultrasound-assisted lumbar puncture, together with the evidence base that suggests that ultrasound has significant benefits. We aim to raise awareness of a method that can make lumbar puncture more likely to succeed and to be more comfortable for the patient. INTRODUCTION A lumbar puncture can often help to diagnose a neurological condition, and the procedure is regularly performed on both neurology wards and day units. However, the traditional, palpation-based technique is not always successful (par- ticularly in obese patients), adding to patient discomfort and anxiety. A common solution is to request a fluoros- copy (X-ray)-guided lumbar puncture, but this involves extra cost as well as radi- ation, and it cannot usually be done at short notice. The use of ultrasound imaging to assist lumbar puncture is not new: it was first described in 1971 by Russian authors. 1 Since then, an evidence base has devel- oped suggesting that the technique has several advantages. In addition, modern portable ultrasound equipment can be used at the bedside. Despite this, ultra- sound scanning is not a routine practice in UK neurology departments, and there are few publications on this topic by neu- rologists in the literature. Here we describe the principles and the advan- tages of the method, aiming to encourage colleagues to seek a brief practical instruction and to learn this useful skill. HOW TO DO AN ULTRASOUND-ASSISTED LUMBAR PUNCTURE The basics We can distinguish between procedures that are ultrasound-guided and those that are ultrasound-assisted. ‘Guided’ refers to using real-time imaging to observe the passage of the needle towards and into the intrathecal space. In contrast, we use the ‘assisted’ technique, which is simpler and uses imaging prepuncture to mark the location of needle insertion (as well as to estimate its depth). A portable, bedside ultrasound machine is used, and in the UK it is usually possible to arrange the loan of one of these at short notice from another hospital department, for example inten- sive care, or the medical equipment department that stores outpatient machines ( figure 1). We recommend a low-frequency (2–5 MHz), curvilinear probe (transducer). This has lower reso- lution but deeper penetration than other options. For scanning, the patient is posi- tioned in a conventional lumbar puncture position which can be either lateral decubitus or sitting. Finding the intervertebral level The ultrasound probe is placed on the skin, parallel to the presumed midline, in the lumbar region. It is then slowly moved medially and laterally, until the vertebral laminae are seen. This repre- sents a paramedian view, and the laminae appear as hyperechoic humps, with pos- terior shadowing ( figure 2). By moving the probe caudad, the examiner sees a horizontal line that represents the sacrum. The transducer is then moved cephalad, counting the humps until the midpoint of the probe is level with the 3/4 lumbar intervertebral space. The skin To cite: Williams S, Khalil M, Weerasinghe A, et al. Pract Neurol 2017;17:47–50. Accepted 22 October 2016 Published Online First 28 November 2016