1. Correct Answer: D. L5-S1

Rationale: In the elderly, degenerative changes and difficulties in positioning the patient may contribute to difficulty in accessing the intrathecal space. The paramedian approach offers an alternative to the midline approach that can overcome inadequate flexion or a calcified interspinous ligament. The size of the interlaminar space can influence the success of lumbar puncture. Ultrasound analysis of the influence of age on spinal anatomy has demonstrated that younger patients have larger interlaminar spaces than elderly patients, and that in all patients the L5-S1 interspace has the largest interlaminar height.

1. Bae J, Park SK, Yoo S, Lim YJ, Kim JT. Influence of age, laterality, patient position, and spinal level on the interlamina space for spinal puncture. Reg Anesth Pain Med. 2020;45:27-31.

2. Correct Answer: A. Paramedian sagittal and transverse

Rationale: The combination of paramedian sagittal and transverse sonographic views yields useful information in determining a patient’s lumbar spine anatomy. The paramedian sagittal view allows identification of the lumbosacral junction and the determination of the precise levels of laminae and transverse processes. The transverse view allows identification of the spinous and articular processes, as well as the angle of rotation in the case of scoliosis. Both views can be used to identify the anterior and posterior complexes, yielding information about the depth at which the epidural space will be reached.

1. Chin A, van Zundert A. Chapter 23: Spinal anesthesia. In: Hadzic A, eds. Hadzic’s Textbook of Regional Anesthesia and Acute Pain Management, 2nd ed. McGraw-Hill; 2017.

3. Correct Answer: D. All of the above

Rationale: A systematic review and meta-analysis of 31 clinical trials demonstrated that when used for placement of spinal and epidural anesthetics and performance of lumbar punctures, lumbar neuraxial ultrasound provided several advantages: improved identification of specific vertebral levels, increased procedural success rate, and improved safety.

In one study, compared with gold standard computed tomography (CT), ultrasound was able to correctly identify a given intervertebral space in up to 90% of cases. Conversely, other studies have shown palpation to be notoriously unreliable, with accurate identification of spaces as infrequent as 29% of the time. The increased success rate of ultrasound-guided procedures was attributable to the correlation between ultrasound-measured depth and actual needle depth. Evidence for safety outcomes varied, with strong evidence for a decrease in the number of attempts and a nonsignificant trend toward a lower incidence of headache. No difference was found in the rate of spinal/epidural hematoma, although being such a rare event, no study was sufficiently powered to detect a difference (and indeed, no hematomas were observed in any study included in the analysis). Nevertheless, the authors of the meta-analysis note that it can be reasonably concluded that decreasing the number of procedural attempts, as ultrasound guidance does, would decrease the risk of spinal/epidural hematoma.

1. Broadbent CR, Maxwell WB, Ferrie R, Wilson DJ, Gawne-Cain M, Russell R. Ability of anaesthetists to identify a marked lumbar interspace. Anaesthesia. 2000 Nov;55(11):1122-1126.

2. Perlas A, Chaparro LE, Chin KJ. Lumbar neuraxial ultrasound for spinal and epidural anesthesia: a systematic review and meta-analysis. Reg Anesth Pain Med. 2016 Mar-Apr;41(2):251-260.