Repair: Surgical Management Based on a 30-Year Experience

Fig. 1

Spectrum of the possible presentations of myelomeningocele (MMC). (a) Complete exposure of the placode surrounded by thin and dystrophic skin. This skin layer must be preserved in order to attempt a reliable closure, but achieving such a closure may be very difficult. (b) Complete exposure of the placode and large skin defect: challenging closure. (c) The placode is exposed and elevated by a filled meningocelic sac: after the dissection of the arachnoid plane and cerebrospinal fluid (CSF) escape, the placode can be easily replaced in the spinal canal and the redundant, intact skin allows a relatively easy closure. (d) Placode partially covered by dystrophic skin and contained in a large meningocelic sac: after the neurulation and the replacement of the placode in the spinal canal, redundant skin may result and its reduction may be required

The operation starts with a limited midline linear skin incision at the upper and lower limits of the malformation, in order to identify the normal elements rostral and caudal to the spinal defect. Then the incision is brought along the border between the dystrophic skin and the arachnoid that surrounds the malformation and circumferentially until the entire placode (with its incomplete arachnoid margin) is completely freed and normal dural margins are identified. The next step is the microsurgical dissection of the free placode along the junctional zone: care must be taken when manipulating the border of the placode for the presence of the adjacent dorsal root entry zone. Care has to be taken to avoid arachnoid and dermal/epidermal remnants on the placode, since they can be responsible for delayed cord tethering or dermoid/epidermoid cyst formation [4, 19, 24, 34].

Sectioning of the filum terminale is an integral part of the procedure that is needed to minimize the risk of secondary tethering [19, 24, 30]. Inspection of the inner aspect of the open dural sac is mandatory to reveal the presence of aberrant nerve roots that terminate in the dural sac: the sectioning of them is not related to worsening of the patient’s neurological status. Differently, all the intradural vascular vessels must be manipulated carefully and mobilized from the arachnoidal adhesions, and their coagulation should be avoided.

Subsequently, the freed lateral edges of the placode are approximated in the midline, and their pia-arachnoid borders are sutured under microscope magnification, with a 7.0 nonabsorbable monofilament, avoiding an excessively tight closure, in order to reconstruct the medullary anatomy (surgical neurulation) [9, 23]. This procedure is not performed to improve the neurological outcome, but to reduce the occurrence of symptomatic late tethering [21, 23].

The dural layer is dissected starting from rostral and caudal normal tissues and then approximated on the midline; afterwards, it is sutured with either 5.0 silk suture or monofilament (continuous suture is preferred). In cases of a narrow spinal canal or when the dural layer is missing, dural patching is necessary. In the first instance, the dural patching is required to obtain a capacious dural sac to prevent re-tethering of the placode, while in the second instance, dural patching is necessary to restore the dural layer itself. The dural patch may be realized using various dural substitutes, the most physiological being represented by autologous tissues, such as muscle or muscular fascia. Alternatively, synthetic dural substitutes and/or dural glues can be useful to obtain a watertight dural closure. A Valsalva maneuver should be performed after completing the dural suture to verify water-tightness. The thoracolumbar fascia is then dissected and sutured over the reconstructed dural sac in order to reinforce the dural closure.

Reconstruction of the superficial layers is performed undermining the skin and the subcutaneous tissue from the muscular fascia. Attention must be paid to preserve, as much as possible, the vessels that provide the blood supply of the cutaneous coverings [17, 28]. The subcutaneous layers are approximated and anchored to the underlying fascia in order to create an adequate support for the skin and to reduce the incidence of retracting scars. Initially, following closure, the skin may be blanched as a sign of tension (Fig. 2). Such initial discoloration usually improves rapidly; wound dehiscence rarely occurs. A nitroglycerine ointment has been suggested to be helpful in some cases [16].

Fig. 2

(a) MMC with large skin defect. The skin reconstruction and closure is realized through a Z-shaped skin incision that allows us to move the edges of the surgical wound and to fill the gap (b). Note the discoloration immediately after the end of the procedure (b) and the good outcome, with regular healing and skin relaxation, after 10 days (c)

Skin closure can be performed in a midline vertical fashion or with a horizontal or oblique suture, with skin edges having little or no tension (Fig. 2). Although rare, in cases of a big myocutaneous defect (namely, larger than 20–25 cm²), reconstruction by a plastic surgeon could be necessary [9]. In our experience, this was required in less than 0.5 % of cases.

During the first 24–48 postoperative hours, the infant is recovered in the neonatal intensive care unit (ICU) to monitor the vital functions and, in particular, to detect possible signs of brainstem dysfunction. If possible, the patient is maintained prone for the first 5 postoperative days, with the lower back slightly elevated above the level of the head to reduce the risk of CSF leakage from the wound. Prophylactic intravenous antibiotics are administered for 3–5 days.

In the past few years some studies and protocols have reported that fetal repair of spina bifida is now considered a standard of care at some fetal centers. However, prenatal repair is a complex and challenging procedure, requiring the most expert, comprehensive care for both mother and fetus [36]. The surgical team’s level of experience in all aspects of care surrounding the operation is of paramount importance. Therapy that is highly dependent on the provider is of limited benefit to the wider population.

In-Utero MMC Repair

In the past 20 years, in-utero treatment of MMC has been gaining greater and greater popularity in selected patients, thus representing an additional therapeutic alternative for a fetus with MMC. Studies in animal models and clinical case series laid the groundwork for a clinical trial to test the safety and efficacy of fetal MMC repair. During the late 1990s and early 2000s, results of nonrandomized clinical trials suggested that significant benefit might result from the prenatal repair of MMC [3]. At present, a prospective, randomized study (the Management of Myelomeningocele Study or MOMS trial) [2] has shown that fetal surgery for MMC before 26 weeks gestation may preserve neurological function, reverse the hindbrain herniation of the Chiari II malformation, and obviate the need for the postnatal placement of a VPS. However, this study also demonstrates that fetal surgery is associated with significant risks related to the risk of chorio-amnion separation, premature rupture of membranes, oligohydramnios, and preterm delivery, in addition to a 3 % fetal mortality rate [1].

Conclusions

Rare in developed countries, but still frequent in developing ones, MMC is still associated with significant lifelong morbidity. Adequate surgical planning is crucial to obtain an adequate repair of the defect and to minimize surgical damage of neural structures and perioperative complications. The surgical technique here summarized is the result of a literature analysis and our 30-year personal experience that could be useful to introduce young surgeons to this particular and not common procedure.

Acknowledgements

Nothing to declare.

Conflict of Interest Statement

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