Myeloschisis is the most severe form of open spinal dysraphism, where the neural tube fails to close completely, resulting in a flat, open neural plate that lies flush with the skin surface without a sac, meninges, or skin covering. It represents complete failure of primary neurulation.

 

Q. How does myeloschisis differ from myelomeningocele?
 

In myelomeningocele, the neural placode protrudes outward and may form a sac; in myeloschisis, the placode is completely flat and level with the skin, with no CSF-filled sac and no meningeal expansion. Myeloschisis indicates a more profound neurulation failure and generally has more severe neurological deficits.

 

Q. What is the embryological basis of myeloschisis?

 

Myeloschisis results from a complete failure of primary neurulation, specifically the failure of the neural folds to elevate and fuse in the midline between gestational days 22 and 28.

 

The sequence of embryological events includes:

Failure of Neural Fold Fusion: The primitive neuroectoderm fails to invaginate and remains exposed as a flat, un-closed neural plate (placode).

 

Failure of Dysjunction: Because fusion never occurs, the surface ectoderm fails to separate from the neuroectoderm.

 

Blockade of Mesodermal Migration: The persistent connection between surface ectoderm and neural tissue prevents paraxial mesenchyme from migrating into the dorsal midline.

 

Absence of Dorsal Elements: Lacking mesodermal investment, there is subsequent failure of formation of the dura mater, paraspinal muscles, posterior bony arches (spina bifida), and overlying dermis.

 

Consequently, the neural placode lies completely exposed on the infant's back, continuous at its lateral margins with the surrounding skin, and subject to secondary in utero chemical damage from amniotic fluid exposure.

 

Q. What are the clinical features of myeloschisis?
 

Infants present with a wide, open, flat placode at birth, typically in the lumbar or lumbosacral region. Neurological deficits are severe and correspond to the lesion level, including complete motor and sensory loss below the defect, neurogenic bladder, and lower limb deformities. There is near-universal association with Chiari II malformation, hydrocephalus, and brainstem abnormalities.

 

Q. How is myeloschisis diagnosed?
 

Diagnosis is clinical at birth: a flat, exposed neural plate without skin or sac. MRI is later performed to evaluate Chiari II, hydrocephalus, and associated anomalies. Antenatal ultrasound and fetal MRI can detect the open defect, ventriculomegaly, and hindbrain changes.

 

Q. How will you manage a newborn with myeloschisis?
 

Management parallels myelomeningocele: immediate sterile dressing, prone positioning, antibiotics if indicated, and urgent closure within 24–48 hours. The goal is to prevent infection and protect the neural tissue, though neurological deficits are typically fixed. Concurrent evaluation for hydrocephalus and Chiari II is essential.

 

Q. How is the defect surgically repaired?
 

The surgical repair of myeloschisis follows the principles of open spinal dysraphism closure, aiming to preserve functional neural tissue, prevent infection/CSF leak, and eliminate tethering. However, because the placode is wide and flat rather than sac-like, reconstruction requires precise micro-dissection and layered closure.

 

Surgical steps include:

 

Microdissection of the Placode (Defining the Junction):

Under the operating microscope, the junction between the non-neural surface epithelium and the neural placode is identified.

The epithelium is sharply dissected off the placode edge to prevent epidermal inclusion cysts (dermoids) down the road.

 

Re-tubularization of the Placode:

The flat, open placode is gently folded inward and its lateral edges are approximated using fine (6-0 or 7-0) monofilament sutures.

Re-creating a neural tube restores central canal geometry and minimizes future spinal cord tethering to surrounding tissue.

 

Watertight Dural Closure:

The dural edges—found tethered laterally along the margins of the bony defect are sharply mobilized.

A watertight, non-constricting duraplasty is performed over the placode (using autologous fascia or dural matrix graft if primary dural edges do not meet).

 

Myofascial Flap Reconstruction:

The paraspinous muscular fascia is incised laterally and mobilized medially over the dural closure to create a strong, secondary protective tissue barrier.

 

Tension-Free Skin Closure:

The surrounding skin and subcutaneous tissue are extensively undermined in the subgaleal-equivalent plane.

A robust, multi-layered skin closure is achieved. For very large defects, plastic surgical techniques (such as rotational flaps or relaxing incision maneuvers) are utilized to avoid tension and wound dehiscence.

 

Q. What is the prognosis in myeloschisis?
 

Prognosis is generally poorer than in typical MMC because of the extent of neurulation failure. Lower-limb paralysis and neurogenic bladder are expected. Hydrocephalus is common and may require shunting. Long-term complications include tethered cord, scoliosis, and urological deterioration.