Lipomyelomeningocele: Pathology, Treatment, and Outcomes

A Review

Christina E. Sarris, B.S; Krystal L. Tomei, M.D., M.P.H; Peter W. Carmel, M.D; Chirag D. Gandhi, M.D.

Disclosures

Neurosurg Focus. 2012;33(4):e3 

In This Article

Intraoperative Monitoring

Lipomyelomeningocele may be considered a high-risk group within spinal dysraphisms amenable to resection given the absence of a discrete plane between the lipoma and neural placode, and the rotational component that may be present as a result of the laterality of the lipoma.[28] To facilitate safe resection of lipomatous components and detethering of the spinal cord via sectioning of the filum terminale, intraoperative neurophysiological monitoring may be used, and may alter the intraoperative surgical plan.[57] Monitoring may include somatosensory evoked potentials, motor evoked potentials, and both stimulated and free-run electromyograms. This monitoring requires the use of total intravenous anesthesia, generally propofol and fentanyl or remifentanil, with only short-acting muscle relaxants used during induction so as not to interfere with monitoring ability.[6,28,38] Somatosensory evoked potentials monitor the integrity of the dorsal column pathway, and frequently the tibial nerve is monitored for evaluation of the L4–S3 nerve roots, although this method is limited by long averaging times and fluctuations in response.[36,38] Motor evoked potentials may be obtained for the quadriceps, anterior tibial, and gastrocnemius muscles, as well as bilateral external anal sphincters using needle electrodes to monitor the lumbosacral nerve roots.[28] Because younger children have more immature myelinated fibers, monitoring of motor evoked potentials may require double-train stimulation to obtain useful motor evoked potential amplitudes.[31,32] The difficulty of obtaining free-run electromyograms should be noted when electrocautery is used.[6] Stimulated electromyography, however, allows for identification of functional nerve roots and delineation of nervous tissue from filum and scar elements.[36,38] In particular, external anal sphincter monitoring allows assessment of the pudendal nerve comprised by the S2–4 nerve roots and provides a good approximation of external urethral sphincter injury as well, although it may not well approximate injury to the parasympathetic nerves that supply the detrusor muscle.[36]

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