Lipomyelomeningocele
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Lipo = fat
Myelo = the nerves of the spinal cord
Meningo = the meninges, or membranes (coverings) around the spinal cord
Cele = a swelling
Lipomyelomeningocele is a condition in which an abnormal growth of fat attaches to the spinal cord and its membranes.
Lipomyelomeningocele arises from an event very early in an embryo’s development. About the third week after conception, a sheet of cells called the neural plate folds to form a tube called the neural tube. The top of the neural tube becomes the brain, and the rest of the tube becomes the spinal cord. Lipomyelomeningocele occurs when an error in the closure of the neural tube allows a type of cell called mesenchyme to contact the inside of the neural tube. These cells prevent the tube from closing properly, disrupting the formation of meninges (membranes, or coverings) and bones around the spinal cord.
Wherever the mesenchymal cells touch the outside of the neural tube, they develop into spinal meninges as usual. Everywhere else, they develop into fat cells. The end result is a fatty growth called a lipoma that begins in or near the spinal cord, connects with the meninges, and extends past the bones of the spinal canal to form a pad of fat beneath the skin.
Normally, the spinal cord is able to move somewhat freely within the spinal canal. But in lipomyelomeningocele, the cord’s movement is restricted by the lipoma’s connection with the meninges and the area outside the spinal canal. This condition is called a tethered spinal cord, and it may have severe consequences.
Lipomyelomeningocele is one type of spinal dysraphism. It may be associated with other forms of dysraphism, dermoid or epidermoid cysts, or Chiari malformation.
Symptoms
When lipomyelomeningocele causes symptoms, they are usually due to pressure or pulling on the tethered spinal cord. Symptoms can include problems with bowel and bladder function, frequent urinary tract infections, spasticity, back and leg pain, muscle weakness or sensory loss in the legs, neuromuscular scoliosis, foot and leg orthopedic abnormalities, and difficulty walking.
As many as half of the infants and children diagnosed with lipomyelomeningocele have no neurological symptoms at the time of diagnosis.
Diagnosis
Lipomyelomeningocele may be diagnosed in utero. However, the diagnosis is challenging and depends in some measure on the positioning of the fetus in the womb.
It can be diagnosed at birth by the presence of a pad of fat over the lower spine. Other skin signs such as a patch of thick hair, a deep dimple, or a red birthmark called a hemangioma over the lower spine are common in infants with various forms of spinal dysraphism, including lipomyelomeningocele.
In infants with signs of lipomyelomeningocele or another form of spinal dysraphism, spinal ultrasound, and Magnetic Resonance (MR) imaging can allow doctors to make a specific diagnosis. MR imaging uses magnets, radio waves and a computer to form detailed pictures of the body’s structures–including bones, fat, and the spinal cord.
Risk Factors
Like other forms of spinal dysraphism, lipomyelomeningocele has complex causes that are not yet completely understood. It is slightly more common in babies of Hispanic ancestry, babies born to mothers who are particularly young or old for childbearing, and babies born to mothers who are obese.
Unlike some other forms of spinal dysraphism, lipomyelomeningocele does not generally seem to be inherited in families. It does not seem to be influenced by the presence of folic acid. (Folic acid supplementation in mothers is known to reduce the incidence of other forms of spinal dysraphism, such as myelomeningocele, or open spina bifida.)
Treatments
During surgery for lipomyelomeningocele, the pediatric neurosurgeon will free the spinal cord from its attachment to the lipoma, remove as much of the lipoma as safely possible, and close the membranes over the spinal cord. The goals of the surgery are to prevent deterioration of neurological function in the future and to preserve or improve current function.
In most cases, there are no guielines for the timing of lipomyelomeningocele surgery. Most doctors believe it is better to operate before any neurological symptoms are present, to prevent such symptoms from developing. In some cases it may be better to wait and watch carefully, performing surgery only if symptoms appear.