Somebody else's nervous system

Focal myelomalacia and syrinx formation after accidental intramedullary lidocaine injection during lumbar anesthesia: A report of 3 cases

Three cases of focal myelomalacia and syrinx formation occurring as complications of lumbar spinal anesthesia are reported. In all three instances complication occurred due to accidental injection of lidocaine into the substance of the spinal cord. The primary complaint in all the three cases was severe sharp and shooting pain in both lower limbs, being more severe in certain dermatomes. Neurological deficits were noticed after the effect of the anesthetic agent had worn off. Sensory and motor deficits were asymmetrical and focal; these improved in 6-12 months time. Pain persisted for 1-3 years and then subsided gradually. Carbamazepine and gabapentin were effective in symptomatic relief of this pain. MRI of the dorsolumbar spine done 4-6 months after the spinal anesthetic procedure showed myelomalacic changes with focal syrinx formation in the conus and epiconus region of the spinal cord. The syrinx extended 1-2 vertebral segments in the vertical plane but was confined to a small area in the axial plane. Attempting to use higher lumbar intervertebral spaces for access to the subarachnoid space or epidural space may lead to inadvertent puncture of the lower dorsal spaces; this makes the procedure of spinal anesthesia at this level prone for spinal cord injury, with subsequent risk of development of myelomalacic syrinx in the conus and epiconus region of the spinal cord.

Foot drop after spinal anesthesia in a patient with a low-lying cord

Damage to the spinal cord/conus medullaris due to incorrect identification of the lumbar space is a known complication of lumbar puncture. However, damage to a low-lying cord using an appropriate interspace is extremely rare. We describe a 26-year-old woman who underwent emergency caesarean section under spinal anesthesia. She developed right foot drop immediately after surgery, which gradually recovered over the next 10 months. Magnetic resonance imaging revealed a low lying cord with a fatty filum terminale and intramedullary T2 hyperintensity, suggestive of needle damage.

Effect of spinal flexion on the conus medullaris: a case series using magnetic resonance imaging

Anatomy textbooks state that the conus medullaris moves cephalad when the vertebral column is flexed. This could confer protection against spinal cord damage during dural puncture, but has not been demonstrated in vivo. We therefore imaged the spine of 10 volunteers using magnetic resonance imaging to determine if such movement occurs with the spine in the neutral and flexed positions. The position of the conus medullaris in relation to the superior endplate of the L1 vertebra was determined. On spinal flexion, the conus medullaris moved cephalad in three subjects and caudad in three subjects, with no change in the remaining four. The median overall movement (95% CI [range]) was 0 mm (4 mm caudad to 1 mm cephalad [3 mm caudad to 1 mm cephalad]; p = 1.0). Whilst spinal flexion may facilitate needle insertion during dural puncture, it is unlikely to confer extra protection against spinal cord damage.

Historical Article

The history of the design of spinal needle tips is discussed, from the first needles used by J. Leonard Corning in 1885 to innovative, modern needle designs that continue to appear on the market. The shape of the needle tip started as a cutting bevel and developed into the atraumatic tip and the pencil-point tip in current common use. Innovative designs such as the stylet-tipped needle and the directional needle are described, as well as the needles used for continuous spinal anaesthesia.