BT_RA 1.6 Describe the myotomal innervation

Not New Year’s Eve fireworks, but even more beautiful – stained glass in Sainte-Chapelle, Paris

Firstly, I would like to wish all of you an extremely Happy New Year!! I hope that 2019 has started well for you. I have had a lovely and relaxed start to the new year and am lucky enough to be heading away skiing in Japan at the end of this week, which will be very welcome respite from the scorching temperatures forecast here.

This is actually a pretty useful LO. I use this LO in practice when I am asked to see a patient on the pain round with leg weakness and an epidural in situ. Our usual practice is to examine the patient and work out whether the weakness is consistent with a peripheral nerve injury, esp in orthopaedic patients, or something more central.

Would you be able to distinguish between a peripheral nerve lesion versus a cord/nerve root problem by the pattern of weakness (and sensory disturbance – but that is covered by another LO)?

I do virtually no orthopaedic anaesthesia, but a good knowledge of myotomal innervation would be very helpful for determining which approach to the brachial plexus will provide the best anaesthesia for your patient and the surgeon.

BT_RA 1.6 Describe the myotomal innervation

The answer to all of these statements can be found in Anatomy of Anaesthetists. This is the sort of thing that may come up in an MCQ, but I can’t imagine much else…. until you reach the Final Exam

All the muscles distal to the wrist are supplied by T1 T/F

Isolated numbness on the lateral aspect of the thigh, with no muscle weakness, is inconsistent with an L2 or L3 nerve root lesion T/F

Injury to the obturator nerve will result in weakness only to hip adduction unlike an L4 nerve root compression, which is also likely to cause quadriceps weaknessT/F

Both an injury to the common peroneal nerve injury and an S1 lesion can cause foot drop T/F

Comfortable surgery on the shoulder would require a block of the nerve roots from C3 – C8 T/F

As an aside, another important muscle is supplied by some of the above dermatomes. Can you think of it? Does this pose any issues in healthy patients? Is unilateral blockade of this muscle ever an issue?

BT_RA 1.7 Describe the midline and paramedian approaches to the sub-arachnoid space and epidural space

BT_RA 1.17

Beyond listing the structures you (hopefully) traverse with a spinal needle, it’s not easy to chase down a few facts about this topic without going to the literature, and even that is sparse.

the paramedian approach avoids the ligamentum flavum    T/F

the paramedian approach avoids the interspinous ligament   T/F

the paramedian approach is made more difficult by calcification in the supraspinous ligament   T/F

the first pass success rate of a median approach is greater than that of a paramedian approach in the elderly     T/F

the first pass success rate of a median approach is greater than that of a paramedian approach in younger patients    T/F

SS_OB 1.7

SS_OB 1.7 Describe the changes in the anatomy of the maternal vertebral column, the spinal cord and meninges relevant to the performance of a central neuraxial block including epidural, spinal and combined spinal-epidural, with appropriate surface markings


TRUE/FALSE  The risk of inadvertent venous puncture, with epidural placement in pregnant women, is the same as in the non-pregnant population

TRUE/FALSE  The line joining the iliac crests (Tuffier’s line) may transverse the body of L5 in late pregnancy

TRUE/FALSE  Epidural space pressure may be positive during labour

TRUE/FALSE  Epidural veins are engorged in late pregnancy

TRUE/FALSE   The ligamentum flavum softens during pregancy