Cromeens B, McKinney JL, Leonard J, Governale L, Brown J, Henry C, Levitt M, Wood R, Besner G, Islam MP. Pygopagus Conjoined Twins: A Neurophysiologic Intraoperative Monitoring Schema. J Clin Neurophysiol. 2016 Oct 1. [Epub ahead of print]
Conjoined twins occur in up to 1 in 50,000 live births with approximately 18% joined in a pygopagus configuration at the buttocks. Twins with this configuration display symptoms and carry surgical risks during separation related to the extent of their connection which can include anorectal, genitourinary, vertebral, and neural structures. Neurophysiologic intraoperative monitoring (NIOM) for these cases has been discussed in the literature with variable utility. We present a case of pygopagus twins with fused spinal cords and imperforate anus where the use of NIOM significantly impacted surgical decision making in division of these critical structures.
Twin girls born conjoined were partially fused at the spine and shared a single imperforate anus. Apportioning nerve roots and anal sphincter muscles correctly as the twins were separated was essential to their future health.
Using free-run electromyography and triggered electromyography, the NIOM group helped surgeons to know which tissue belonged to which girl during the 16-hour separation, performed in September 2015. Electromyography records the electrical activity of muscle tissue, which can be spontaneous or activated during manipulation or stimulation of the nerves connected to those muscles.
The results show the benefits of NIOM beyond traditional neurosurgical or orthopedic cases, surgeons and NIOM group members report in a case study published online in the Journal of Clinical Neurophysiology.
The girls, now 2 years old, returned home in January 2017, walking and playing independently and described as healthy and happy.
"Conjoined children need to undergo separation, and it may be an accepted risk that some muscle is divided so that it's not functional to the child who is apportioned it," says Monica Islam, MD, a pediatric neurologist and director of the Evoked Potential and Intraoperative Monitoring Program at Nationwide Children's. "But muscle, nerve or other tissue apportioned to the wrong twin is of no use."
"We were able to provide information that helped guide the surgeons with perhaps a little more confidence in a high-risk situation — that they were proceeding with separation to preserve the highest degree of neurologic function possible and optimal anal sphincter function in each child," continues Dr. Islam, who is also an assistant professor of Clinical Pediatrics at The Ohio State University College of Medicine.
Prior to surgery, the medical team couldn't clearly identify to which baby some nerve roots belonged in the presumed spinal cord cleavage plane. The team was also uncertain whether the twins shared the sphincter equally.
The NIOM group was involved in early planning and devised a strategy to assist in identifying appropriate tissue division in real time and in a crowded surgical suite.
The group used color-coded wires for each child's legs, right side and left side, to monitor nerve and muscle activity. They arranged six electrodes like a clock face around the shared anal sphincter, coded with six rainbow colors in red, orange, yellow, green, blue and violet in order to ease tracking of which portion of sphincter, when stimulated, elicited a response in which patient.
Using the two types of electromyography, the group identified activity patterns indicating which nerve roots belonged to which baby and revealing that a more oblique cleavage plane was required than the plane that would have been chosen intuitively, team members say. Monitoring also enabled the team to map the sphincter. As they recorded each location on the clock face, they identified the owner of that portion of sphincter muscle: the twin whose leg muscles simultaneously fired…
After separation, the twins underwent completion anoplasties. They retain full motor capacity of their legs and feet and appear to have normal innervation of pelvic structures. Their sphincters respond to direct muscle stimulation, but fecal continence won't be known for a few years.