Today’s Pediatric Anesthesia Article of the Day is an excellent review article of the medical and neurosurgical management of spina bifida. Unfortunately, and perhaps not surprisingly (the article was written by a neurosurgeon after all), the anesthetic management of the surgical repair is not discussed at all. Thus, to supplement this PAAD, I’ve asked Dr. Debnath Chatterjee, the editor and chief of Open Anesthesia, to write a brief review of the anesthetic management of this developmental malformation that I will post tomorrow. But first a word from Dr. Glaucomflecken. Myron Yaster MD
Original article
Bermans J Iskandar and Richard H Finnell. Spina Bifida. N Engl J Med. 2022 Aug 4;387(5):444-450. PMID: 3592145
“Failure of the neural tube to fuse during the third week of gestation leads to an open neural-tube defect at the cranial level (anencephaly), the spinal level (myelomeningocele or, simply, spina bifida), or both (craniorachischisis)”.1 “A myelomeningocele is an open defect consisting of a malformed spinal cord that has no dura, bone, muscle, or skin coverage, with associated susceptibility to infection and cerebrospinal fluid (CSF) leakage” (figure).1 “Incomplete formation of the lower spinal cord causes leg, bladder, and bowel dysfunction. Although experimental evidence confirming any of the many proposed pathophysiological causes is lacking, the assumption has been that the open spinal defect and associated CSF leakage in utero can cause lack of distention of the primitive cerebral ventricular system, leading to anatomical intracranial abnormalities, including herniation of the cerebellar vermis and medulla into the spinal canal (Chiari II malformation). The Chiari II malformation, in turn, obstructs the flow of CSF around the lower brain stem, causing ventricular dilatation with increased intracranial pressure (hydrocephalus) and cystic dilatation of the spinal cord (syringomyelia), with brain-stem and upper spinal cord dysfunction. Months or years later, scarring (arachnoiditis) of the myelomeningocele repair site may result in traction on the spinal cord, leading to a tethered cord in at least a third of patients, with symptoms that include back and leg pain and worsening leg, bladder, and bowel function. Repeated surgery is often required to release the spinal cord from surrounding scar tissue”.1
The prevalence of neural tube defects can be reduced by about 70% by daily folate consumption, either with vitamins or fortified wheat flour, taken at least one month prior to pregnancy.2, 3 Because the diagnosis is often made via 2nd trimester ultrasonography, management options include prenatal repair (“fetal surgery”)4, 5, post-natal repair, and although not mentioned in the article fetal termination (abortion), particularly with anencephaly. “Infants who have undergone prenatal repair have improved motor function of the legs and feet at 30 months, with a lower incidence of hydrocephalus (40%, vs. 82% with postnatal repair) and Chiari II malformation (64% vs. 96%) at 1 year”.4, 5 Whether the magnitude of these improved outcomes will continue to be seen as the prenatal repair is performed at more centers with lower case volumes or with new techniques such as fetoscopic surgery is currently unknown. The risks associated with prenatal repair as reported in the MOMS study4 included premature rupture of membranes, risk of uterine rupture with subsequent pregnancies, as well as fetal complications of premature birth, subsequent intraspinal inclusion cysts and tethered cord syndrome.
Regardless of when surgical repair is performed, patients with spina bifida have multiple subsequent medical and surgical problems that affect them throughout their lives. They include: hydrocephalus, Chiari II malformation, syringomyelia, tethered spinal cord, which may temporarily exacerbate the underlying neurologic deficit, shunt malfunction, or, foot deformities or contractures that affect standing, walking, or transferring from or to a wheelchair, as well as the need for subsequent surgeries, such as those for scoliosis and hip and limb contractures. Neurogenic bladder may cause urinary tract infection and may require lifelong intermittent catheterization. Urologic surgery may be necessary to ameliorate neurogenic bladder. The ACE procedure (antegrade continence enema) may be performed to ameliorate constipation. Thus, most patients with spina bifida are operating room “frequent flyers” and they and their families may have very specific requests on how anesthesia is induced, positioning, and post operative pain control. Finally, the article underlines that regardless of how or when the neurosurgical repair was performed, always consider increased intracranial pressure as a cause for neurologic deterioration regardless of ventricular size on imaging studies.
Patients with meningocele have a lifelong risk of anaphylaxis to latex and latex exposure should be scrupulously avoided, although it is unknown whether the risk has decreased from the era when these patients were repeatedly exposed to latex through used of red rubber catheters for catheterization and latex gloves for medical and surgical procedures. The pathophysiology/epidemiology of this increased risk of latex allergy in this population is unknown.
Like many primarily pediatric diseases of the past (think congenital heart disease, CF, sickle cell disease), “most of the estimated 166,000 persons in the United States who are living with spina bifida are adults”.1 So to our many readers who anesthetize both children and adults, these patients are coming to your ORs soon. Finally, we are also including in the references a consensus-based guideline by the Spina Bifida Association and its physician partners as a resource to you.6
References
1. Iskandar BJ, Finnell RH. Spina Bifida. The New England journal of medicine. Aug 4 2022;387(5):444-450. doi:10.1056/NEJMra2116032
2. Grosse SD, Collins JS. Folic acid supplementation and neural tube defect recurrence prevention. Birth Defects Res A Clin Mol Teratol. Nov 2007;79(11):737-42. doi:10.1002/bdra.20394
3. Wang H, De Steur H, Chen G, et al. Effectiveness of Folic Acid Fortified Flour for Prevention of Neural Tube Defects in a High Risk Region. Nutrients. Mar 9 2016;8(3):152. doi:10.3390/nu8030152
4. Adzick NS, Thom EA, Spong CY, et al. A randomized trial of prenatal versus postnatal repair of myelomeningocele. The New England journal of medicine. Mar 17 2011;364(11):993-1004. doi:10.1056/NEJMoa1014379
5. Farmer DL, Thom EA, Brock JW, 3rd, et al. The Management of Myelomeningocele Study: full cohort 30-month pediatric outcomes. American journal of obstetrics and gynecology. Feb 2018;218(2):256.e1-256.e13. doi:10.1016/j.ajog.2017.12.001
6. Spina bifida association. Guidelines for the care of people with spina bifida, 4th edition. Accessed 08/6/2022, https://www.spinabifidaassociation.org/wp-content/uploads/Guidelines-for-the-Care-of-People-with-Spina-Bifida-2018.pdf