- Prone: The encephalocele is repaired with the infant positioned prone overlying two well-padded gel chest rolls. The head is placed face down onto a well-padded horseshoe headrest with extreme care taken to prevent pressure on the globes. All pressure points are carefully padded.
- Neck flexed: The neck is flexed as needed to get adequate exposure of the encephalocele, and the occipitocervical region is prepared thoroughly with chlorhexidine gluconate/isopropyl alcohol solution, which is allowed to dry. Grasping forceps may be used to elevate the encephalocele sac to ensure complete skin preparation. Care must be taken when manipulating the sac to prevent brainstem dysfunction. Care must also be taken to prevent chlorhexidine gluconate/isopropyl alcohol solution from getting into the patient’s eyes.
- Vertical skin incision: For cervical and low-lying occipital encephaloceles, the sac is opened vertically to allow access to both the upper cervical spine and the posterior fossa. To ensure adequate closure of the skin at the end of the operation, the vertical incision is made in an elliptical fashion around the circumference of the sac at some distance away from the neck of the sac.
- Expose spine elements: When the encephalocele arises entirely from a defect in the cervical spine, it is repaired by a midline posterior approach with the dissection beginning at normal cervical spine levels rostral and caudal to the defect (8). The normal levels of the cervical spine immediately rostral and caudal to the bony defect and encephalocele stalk are exposed by performing limited laminectomies both above and below the level of the defect.
- Expose encephalocele stalk: The bony defect surrounding the stalk may have to be widened to provide a better exposure of the encephalocele stalk. If possible, the sac should not be entered at this stage of the operation. Instead, blunt dissection is performed to separate the skin from the underlying dura until the neck of the sac and the margins of the skull defect can be seen.
- Open dura: Metzenbaum scissors are used to open the dura near its dome and expose the interior of the sac. CSF is drained, and a specimen is sent for culture.
- Free herniated neural tissue: The herniated neural tissue is inspected, and the dissection plane previously developed between the dura and skin is extended circumferentially toward the neck of the encephalocele to expose the underlying skull defect and surrounding bone.
At this point, the contents of the sac are carefully examined to determine the proper surgical approach (24). The extent to which an encephalocele can be corrected depends on the size of the malformation and the amount/type of herniated brain tissue. No attempt should be made to reduce the herniated tissue back into the intracranial compartment (21).
- Simple meningocele: If there is no neural tissue present, consistent with a simple meningocele, the redundant skin and dura are excised, leaving a cuff of dura at the base that is closed in a watertight fashion. However, if neural tissue is present in the sac, the surgeon must decide whether to resect or preserve this tissue.
- Encephalocele with nonfunctional neural tissue: In many cases, the extracranial neural tissue is severely dysplastic and ischemic and contains few viable neurons. Moreover, in cases where there is a large amount of extracranial tissue, the tissue cannot be easily reduced. Thus, if the extracranial neural tissue is deemed nonfunctional, it can be excised flush with the skull defect. Blunt dissection and bipolar cautery are used to circumferentially isolate the neural tissue from the dura at the base of the sac, and the herniated tissue is then transected at its base. Large arterial and venous vascular channels are often found coursing through the tissue and must be thoroughly clipped and/or cauterized prior to excising the tissue. Meticulous hemostasis is achieved, and the dura is closed in a watertight fashion using a patch graft as needed.
- Encephalocele with functional neural tissue: In patients with functional extracranial neural tissue, every attempt should be made to preserve the functional brain tissue. Therefore, a dural patch graft and expansion cranioplasty may be required to close the defect around the herniated tissue that cannot be excised due to its presumed functionality. In some cases where there is viable neural tissue in the encephalocele preventing immediate closure, CSF diversion can facilitate regression of the tissue into the cervical spinal canal and enable delayed closure (8).
In patients with occipitocervical encephaloceles with a large skull defect resulting from a large amount of herniated tissue, several techniques are available to close the skull defect.
- Calvarial graft: In young infants capable of new bone regeneration, a full thickness calvarial graft can be harvested from adjacent normal skull to cover the skull defect, and then surrounding barrel stave expansile osteotomies can be performed (1).
- Delayed cranioplasty: Alternatively, the encephalocele can be closed with a duraplasty shortly after birth followed by delayed cranioplasty with a split thickness autologous bone graft harvested when the child’s bone is sufficiently thick or a CT-guided custom-fitting implant. In patients who present with hydrocephalus, initial treatment may involve placement of a ventriculoperitoneal shunt to allow for regression of the encephalocele sac contents back into the cervical spinal canal and subsequent delayed closure of the cervical encephalocele (8).
- Trim excess: To close the skin, the excess partial thickness skin is trimmed away, and blunt dissection is performed within the subgaleal space to mobilize sufficient skin for a tension-free closure (24).
- Two-layer closure: The skin is then closed in two layers: the galea is closed first with buried interrupted 4-0 vicryl sutures followed by closure of the skin with a running 5-0 monofilament suture.
Occasionally, a shunt is required to drain excess CSF from the brain and/or to treat associated hydrocephalus, which may not develop until after the encephalocele has been repaired (21).