12-06-2006

En el Club de revistas de Mayo, comenté lo siguiente sobre melanocitosis neurocutánea en los Nevus melanocíticos congénitos (NMC )

"Large or multiple congenital melanocytic nevi: Occurrence of neurocutaneous melanocytosis in 1008 persons

Bett BJ
Journal of the American Academy of Dermatology February 2006 pages 767-777

Melanocitosis neurocutánea (MN) es la presencia de grandes o múltiples nevus congénitos con melanocitosis benigna o maligna en leptomeninges y cerebro.
En el análisis de una base de datos con 1008 personas con nevus congénitos gigantes o múltiples, la muerte por melanoma (MM), ocurrió en 4.8% y por MN, en 2.3%, pero, una vez que MN sintomática se diagnosticó, la mortalidad en este grupo subió al 34%...es decir MN es temible.
La imagenología por resonancia magnética (MRI) cerebral y espinal, no fué de gran ayuda para diagnosticar MN, en el estudio de de Bett y lo atribuye a la inexperiencia de algunos radiólogos...ocurren MRI falsas positivas y falsas negativas...la más alta sensibilidad de este examen se obtiene antes de los 4 meses de edad...hace poco, en otro club de revistas del 2004, comentaba que este examen era lo más importante para llegar al diagnóstico.

La conclusión de Bett es que para el diagnóstico de MN en personas con nevus congénitos gigantes, prima la sintomatología: hidrocefalia y convulsiones.
Se considera que si un paciente tiene MN, es superfluo tratar el nevus.

Entonces...los pacientes con nevus gigantes congénitos además de lo cosmético, tienen 2 grandes riesgos: MM (dentro del nevus, o extracutáneo) y MN."

Hasta aquí, el comentario del artículo…pero en una discusión entre dermatólogos por intenet, me llegó lo siguiente que es un punto de vista diferente y bien sustentado…lo pongo en el idioma original:

My understanding is that we should do nothing differently _if_ the child is neurologically asymptomatic.
I had to deal with this issue recently when we saw a case at birth of a giant bathing trunk nevus in a little girl who was found to also have neurocutaneous melanosis (NCM). The little girl was asymptomatic neurologically and has been meeting her developmental milstones normally.
When I saw her at three months of age, she was an active happy little girl, __similing__ to her mother and kicking with her legs.
The clinicians were under the impression that the prognosis is uniformly bad because of the positive MRI, __and I did agree with them__.
I reviewed the literature at the time and concluded that the prognosis is not necessarily guarded.
Actually, some of the best papers I read on this were by Dr. Ilona Frieden's group in San Francisco [e.g. Plast. Reconstr. Surg. 107: 933, 2001:
In this paper, the authors report on 42 cases of NCM. 10 of those (23%) were neurologically _asymptomatic_ and showed positive findings on MRI. Only one of those
patients developed symptoms in an average followup period of 5 years].

If the patient becomes neurologically symptomatic, then the prognosis is poor.
In Dr. Frieden's experience, the presence of neurocutaneous melanosis without neurologic symptoms does not necessarily indicate a guarded prognosis.
The presence of melanotic deposits on MRI should not affect our management decisions that we would make if the patient had the same large nevus with a negative MRI. It is recommended that any big surgeries (if contemplated) be postponed till the patient is
2-3 years old, as most patients with neurologically _symptomatic_ NCM become manifest by that age.
Dr. Ruiz-Maldonado in Mexico points out in one of his papers [Dermatology. 1997;195(2):125-8.] that neurologic evaluation of such patients should be done by an experienced pediatric neurologist, as some subtle manifestations may not be picked up by some non-specialized examiners.
In his paper, he reports on patients with giant congenital nevi on the head and neck area. 11 of those were found to have mild neurologic symptoms by experienced examiners (and they were previously considered asymptomatic). And those patient did not actually have evidence of NCM by MRI.

Doing an MRI now may be controversial but I don't think it's a bad idea, especially that you have a nevus in the lumbosacral area. In the paper quoted above by Dr. Frieden's group, Foster el et. recommend doing MRIs (of the spine) on all patients with a giant congenital nevus with lumbosacral involvement (perhaps this is more important in
cases where the giant nevus itself involves the lumbosacral area, unlike the case in your patient, but still, I would still consider an MRI). The reason for that rercommendation is to detect the presence of a tethered cord which is a treatable condition and can lead to
neurologic deterioration if left untreated.
I would vote for doing an MRI now rather than wait. Foster et al also point out in their paper that the detection of melanotic deposits in the central nervous system becomes more difficult as the child grows older, and that they are most detectable by MRI in the first 4 months of age.

Jairo Mesa Cock