Resumen:    Desde octubre de 1993 hasta marzo de 1997, aproximadamente 1019 pacientes recibieron tratamiento de forma ambulatorio mediante radiocirugía con Bisturí Gamma.  De estos pacientes. 182 tuvieron por lo menos 8 meses de seguimiento y se les trató por enfermedad metastática.  Hubieron 47 pacientes que tuvieron una sola metástasis cerebral, mientras que los 135 restantes presentaron entre 2 y 38 lesiones.  En esta serie de 182 pacientes, 48 han recibido tratamiento dos veces, 14 pacientes han recibido tratamiento tres veces, y uno ha recibido tratamiento seis veces, orientado a 38 sitios diferentes durante un período de 32 meses.  Tres pacientes requirieron tratamiento médico al presentárseles necrosis por radiación, diagnosticada mediante biopsia estereotáctica.  Todos ellos recibieron tratamiento en una misma lesión por lo menos dos veces, y permanecieron sintomáticos debido a la necrosis.

No hubo diferencia importante entre el tiempo de supervivencia promedio de los 22 pacientes que fallecieron y que recibieron tratamiento para una sola metástasis, con un promedio de 11,3) meses (media de 6,4), y el de los 81 pacientes que fallecieron y que recibieron tratamiento de metástasis múltiple, con un promedio de 12,2 meses (media de 10,6).  En los 64 pacientes sobrevivientes con metástasis múltiple. el tiempo de supervivencia promedio es de 26,0 meses (media de 22,7).  De estos pacientes, 38 han sobrevivido al tratamiento aproximadamente 18 meses.  Los 25 pacientes sobrevivientes con una sola metástasis tienen un tiempo de supervivencia promedio de 27,8 meses (media de 25,4).  Diez de estos pacientes han sobrevivido más de 18 meses.

En general, 86 pacientes murieron de enfermedad sistémica progresiva y 17 murieron de enfermedades progresivas del sistema nervioso central.  De las 86 muertes debidas a enfermedad sistémica progresiva. 9-0 ocurrieron en la categoría de una sola metástasis y 65 en la categoría de metástasis múltiple.  La enfermedad sistémica progresiva ha sido responsable del 81% (65/80) de las muertes en los pacientes con metástasis múltiple y del 91% (20/22) de las muertes en pacientes con una sola metástasis.

CONCLUSIÓN:     Llegamos a la conclusión de que el número de lesiones tratadas en metástasis cerebrales no influye en el resultado, sino que es el control de la enfermedad sistémica el que realmente determina el resultado.  La radiocirugía con Bisturí Gamma ofrece un control eficaz de la progresión en casos de metástasis cerebrales solas o múltiples con muy baja morbilidad.

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Abstract: Chiari 1 Malformations (hindbrain hernias) were describes more than a century ago and characterized as to their severity.  Type II lesions are seen almost exclusively with myelomeningocele patients and are defined as caudal descent of the cerebellar vermis, brain stem and IV ventricle.  Type III lesions are rare and are the most severely involved.  These patients have movement of portions of the cerebellum and brain stem out through a sac at the junction of the skull and cervical spine.  Type 1 Chiarl malformations are the mildest deformities and defined as caudal descent of the cerebellar tonsils.  Generally the brain stem and forth ventricle are not caudally displaced.  Since the advent of MRI the definition of Chiari I malformations has changed with time.  Originally 3 mm of caudal descent was thought to be significant, then up to 5 mm and more recently as much as 7 mm of displacement has been thought to be within the normal range.  Descent of the tonsils is also a function of age with displacement of equal amounts being more significant in the older population.  Other characteristics are also important in evaluating a patient with caudal descent of the tonsils.  Are the tonsils pointed, is there a retroflexed dens, is the posterior fossa small, is there an associated syrinx.  All of the factors should be born in mind in determining and interpreting an MRI of the cranio-cervical junction for a Chiari I malformation.

Presentation of the patient with a Chiari I malformation is multifaceted.  Many children, even infants. may just have valsalva induced pain and arching.  Infants as young as 6 months may extend the cervical spine and cry as a consequence of sneezing, straining or laughing.  The infant may even grab the back of the neck with a hand before they are verbal.  Later in life scoliosis, leg weakness, sensory loss and again pain are primary methods of presentation.  Of special comment is that neurogenic bladder symptoms are almost never seen with a syrinx or Chiari I malformation until severe weakness has developed.

Again MRI is the only procedure that can adequately evaluate the problem.  Computerized tomography (CT) of the head to rule out a Chiari 1 malformation is notorious for generating misleading information.

Treatment of the Chiari I malformation is surgery for the patient with clear symptoms or in the presence of a syrinx.  The surgery involves a suboccipital craniectomy and C-1 laminectomy.  Many surgeons follow the bony decompression with dural grafting.  The relief of symptoms (pain) is immediate.  Complications are quite uncommon and long term follow-up is grafting.

More perplexing is the child with diffuse head pain and a hindbrain hernia in the intermediate range.  Each of these situations must be considered individually.  More recently a limited number of patients have been evaluated without any evidence of a Chiari I malformation and large or holocord syrinxes.  After careful analysis 6 children were operated upon in this category each with a resolution of their syrinx.  This has been termed "Chiari 0" implying there is no hindbrain hernia and yet a posterior fossa decompression was effective in resolving their situation.

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Abstract: The faces of occult spinal dysraphism are varied and interesting.  These congenital malformations of the spinal cord are linked together by a common etiology, presentation, timing of the embryologic error, and the propensity to occur together.  The diseases processes in question are: split cord anomalies (diastematomyelia), tethered spinal cord from a thickened filum terminale, terminal syringomyelia, dermal sinus tracts, lipomyelomeningocele, meningocele manqué, and neurentic cysts.  In addition to occurring together all can be seen in association with myelomeningocele.

Presentation of these entities range from the neonatal period with a skin signature (2/3 of patients) to childhood presentations with orthopedic or urologic changes to adults with chronic disabilities that are eventually forced to see a physician because of life altering pain.  The skin changes suggestive of occult spinal dysraphism include: local hirsutism, dermal sinus, fiat capillary hemangioma, midline subcutaneous mass, human "tail", midline "cigarette burn" (incompletely formed dermis) or simply a deviation of the upper aspect of the gluteal crease.  Of these skin changes true focal hirsutism is the most predictive of a surgically significant intradural problem.  There is a close association of this skin change with split cord anomalies.  The least predictive change is the fiat capillary hemangioma with (10% of lumbar lesions having a surgically significant intradural correlation. It is important to differentiate these skin changes from simply a coccygeal pit.  Coccygeal pits are a common (4-8% of newborns) finding and are a midline depression of the skin directly over the coccyx.  All these innocent lesions are within the gluteal crease.  A similar skin change above the gluteal crease is significant and appropriate to evaluate.

One third of patients will have normal skin.  Screening patients for the presence of occult spinal dysraphism by examining the skin only is inappropriate.  The presence of a neurogenic bladder or progressive orthopedic deformity of the feet or legs should trigger consideration of neurologic cause. It is unusual for these patients to present primarily to the neurosurgeon they almost always must be recognized by the pediatrician, urologist, neurologist or orthopedist.

Once the problem is considered, MRI is the current best method of confirmation.  Plain radiographs may detect a spina bifida in the dorsal elements of the sacrum or lumbar spine and document spinal deformity but are an inaccurate method of screening patients for surgically significant problems.

There are no medical alternatives to treatment of these lesions.  All seven pathologic entities demand surgical attention.  The risk of surgical intervention varies depending on the complexity of the situation but is almost always less risky then the natural history.

Outcome with regard to neurological function is directly a function of the patient's status prior to operation.  Pain is very likely to be relieved, motor strength may improve and sensory disturbance can get better but is also most likely to be injured with operation.  Bladder dysfunction is unlikely to improve.

In summary, patients with occult spinal dysraphism can be easily diagnosed with MRI and prevented from expressing the natural history of their disease through surgical intervention.  Surgery in experienced hands carries little risk of serious permanent injury and should be seriously considered once the diagnosis is confirmed.

lt appears there is a clear genetic link between these problems and the more overt form of neural tube defect-myelomeningocele.  Without dietary supplementation with folic acid the rate of a subsequent pregnancy to the same couple carries a similar risk of an open neutral tube defects as if the initial involved child had had a myelomeningocele.

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