Myelomeningocele

What Is It?

A myelomeningocele (sometimes called a meningomyelocele) is the most severe form of spina bifida. It is a congenital malformation that results when an error in the normal development of the nervous system, particularly the spinal cord and spine, occurs. The malformation results in incomplete development of the bottom end of the spinal cord, the spinal nerves and all the soft-tissue and bony coverings on the back of the spine. This results in a sac, filled with cerebrospinal fluid, which bulges out the back, generally in the lower back or lumbar region.

The meninges are the coverings of the brain and spinal cord, including, from outside to inside, the tough dura mater, the arachnoid membrane and the delicate pia mater. While a meningocele is a malformation just of the outermost coverings of the spinal cord, a myelomeningocele includes abnormal development of the underlying spinal cord itself. In development, normally the nervous system develops from a plate of cells that fold to become a tube, the neural tube. If the lower end of the tube does not close normally, it can lead to varous forms of spina bifida, meningocele being the most severe.

While this represents the most severe form of spina bifida, less severe is just involvement of the meninges, the coverings of the spinal cord, called a meningocele. The most mild form is spina bifida occulta, which does not involve any of the nervous system structures or the meninges, just a small, occult bony spine malformation in the lower back.

What Types of Symptoms Are Typical?

First, these deformities are usually very obvious at birth, presenting as a sac of variable size bulging from the back. Very often the skin and other soft-tissues overlying the sac are malformed as well and often cerebrospinal fluid leads from the area.

Because a meningomyelocele includes abnormal development of the end of the spinal cord, neurological symptoms are common. In less severe forms the child may be born with some normal movement of the legs, but in more severe cases they may be born with very significant disability of the movement and sensation of the legs. Even if a child has some reflex movement of the legs at birth, the abnormal spinal cord and poor coverings on the back very frequently lead to further trauma to the spinal cord which can lead to progressive loss of nervous system function.

Because the sac is practically open to the outside environment in many cases, there is also a high risk of infection, leading to meningitis.

There is a close association with myelomeningocele and hydrocephalus and the Arnold-Chiari Malformation (Type II). Many patients with this malformation will also have hydrocephalus which may require separate treatment.

How Is The Diagnosis Typically Made?

Generally, myelomeningocele is obvious at birth, presenting as a sac with abnormal skin on the lower back, although the size and exact location can vary. In some patients, a pre-natal ultrasound examination can reveal the malformation prior to the time of birth.

After the malformation is detected, generally some imaging study such as an MRI scan or further ultrasounds are used to distinguish myelomeningocele from other malformations such as meningocele and to evaluate for hydrocephalus and any other malformations which may occur simultaneously.

What Are Some Common Treatments?

Generally, when a child is born with this malformation, urgent surgical correction of the deformity is suggested. The goal of surgery is to remove the excess tissues, to cover and protect the abnormal spinal cord and to close and protect the nervous system structures from the outside environment. These goals aim at preventing further neurological deterioration and preventing infection which can be introduced through the abnormal coverings. While surgery cannot correct that abnormal development of the spinal cord, it can help to correct that abnormality in the coverings of the spine, to help preserve what function there is.

With treatment, outcomes vary considerably. Many patients will have permanent disability of the legs and bowel and bladder dysfunction. Others may preserve some function.

Some patients who present with hydrocephalus will require subsequent treatment of the that condition as well.

Each case varies and can be very different in size, location, extent of the malformation, etc. Therefore, each individual patient's treatment plan can vary considerably and should be discussed with their own personal physicians.

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Important Note: This site is not intended to offer medical advice. Every patient is different, and only your personal physician can help to counsel you about what is best for your situation. What we offer is general reference information about various disorders and treatments for your education.

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