Shedding Some Light on Neurocutaneous Melanocytosis
Dr. Yasmin Khakoo
By Patricia McAdams, Staff Writer, Nevus Outreach
After the birth of a baby with an exceedingly rare condition such as a large congenital melanocytic nevus (CMN), parents are overwhelmed with questions and worries, only to learn of the risk of an even rarer neurological condition that can piggyback on CMN. Yasmin Khakoo, MD, talked to parents at the 2012 Nevus Outreach Conference in Texas about this condition, called neurocutaneous melanocytosis (NCM). Melanocytes are cells that produce melanin — the pigment that colors our skin. NCM refers to deposits of melanin in the brain or central nervous system.
Pediatric neurologist/neuro-oncologist at Memorial Sloan-Kettering Cancer Center, in New York, Khakoo is among the leading caregivers in the country of children with NCM. While most babies born with CMN do not have this neurological condition, doctors like to rule it out early, so children with this diagnosis can get the very best of care. The primary way to diagnose NCM is with magnetic resonance imaging (MRI).
Who should get an MRI
Khakoo recommends that all babies with CMN get an MRI of the brain and spine with and without contrast before four months of age, especially if he or she has more than 20 satellite nevi. This imaging test so early in a child’s life is desirable, because it allows the clearest view of even small deposits of melanin, which are more difficult to see as the brain’s myelin develops (this is not to say that a skilled radiologist cannot see NCM on the MRIs of older patients, only that it may not be as easy to see. –Ed.) Myelin is a sheath that forms a protective coating on nerve fibers.
“If that initial MRI is normal and your child has no neurological symptoms, then no further MRI is recommended,” Khakoo says.
“If the initial MRI is positive for NCM, then your child should be followed closely by a child neurologist. If your child experiences no symptoms, a repeat MRI is not indicated unless some complications develop.”
Babies need to be sedated for an MRI, but there is only a very slight risk from anesthesia, Khakoo says. The good news is that the MRI itself is not harmful for a young child. CT scans, which take less time than MRI, do not provide the same level of detail that MRI scans can. Additionally CT scans expose the child to a small amount of radiation. CT scans may be required, however, if a child is unwell, or if the anesthesia required for an MRI is felt to be unsafe for the child.
According to the Nevus Outreach data registry, which dates back to 1998 and includes 1003 individuals with CMN, 76 individuals, or 7.6 percent have been diagnosed with NCM, though not all have symptoms. Some children with NCM are, and remain, symptoms free, doctors have found.
Hydrocephalus, sometimes referred to as water on the brain, is one possible complication of NCM. Khahoo says that each of us has spinal fluid bathing our brain, but hydrocephalus refers to an excess of that fluid. This excess fluid can account for anything from vomiting to headaches to trouble walking. Doctors treat hydrocephalus with a shunt that ferries some of that fluid to another location in the body, where it can be absorbed. New types of shunts can be programmed to shunt fluid at different rates depending upon the cause of the hydrocephalus.
Seizures are another complication of NCM in some children, but these can often be managed with medications. There are lots of new anti-convulsant medications available today, Khakoo says. She recommends, however, that you take your child to a strong pediatric epilepsy center, if he or she experiences seizures, because this therapy can be complicated. For children who do not respond to anti-convulsant medication, surgery to remove the brain tissue causing the seizure may give kids a seizure-free life.
While the prospect of brain surgery is frightening to families, some parents choose to proceed with surgery when their child is not helped by meds. Kathy Stewart and Nevus Outreach director Mark Beckwith, for example, chose surgery for their daughter Megan two years ago when her seizures could not be controlled.
“Megan is a walking testament to surgery making a huge difference in her life,” says Stewart. “The (melanin) deposit on her amygdala was removed when she was 14 and she has been seizure free ever since.”
Khakoo says that children with NCM should also have a basic ear and eye exam to rule out melanin deposits on or near a child’s eye or auditory nerves, which could affect hearing or vision.
Most instances of NCM involve benign deposits of melanocytes that may — or may not — cause any symptoms. In very rare instances, melanocytes may transform into a form of melanoma. Khakoo points out, however, that while NCM is a very serious neurological disorder and some children have symptoms that must be treated, “many of these children are doing fine even years after their symptoms began.”
According to Khakoo, having a neurological condition may result in behavior or developmental issues for some children. But every child diagnosed with NCM is eligible for early intervention services. Khakoo encourages families to take advantage of all these services, which may benefit children enormously.
“Certain seizure medications help to treat behavior issues as well,” she says. “And teenagers with seizures may be eligible for scholarships from Pfizer and other organizations, too.”.
In looking toward the future, Khahoo explained that certain pathways have been found to be important in patients with CMN and NCM. “This finding suggests that a targeted form of immunotherapy may one day play a part in future treatments for this condition.”