Initial Management at Presentation
Chiari I malformation
- Surgical decompression of foramen magnum if treatment required: Presently, there is no alternative to surgical therapy for Chiari I malformation, and the indications for surgery are somewhat controversial. Most surgeons agree that adequate CSF flow from the foramen of Magendie should be visualized at the time of surgery before surgery is deemed complete (10).
- Confirm stability of craniocervical junction: Significant craniocervical instability should be ruled out with dynamic cervical spine films prior to surgery. The presence of skull base abnormalities such as basilar invagination or ventral compression should alert the surgeon to the possibility of chronic craniocervical instability that might need a concomitant craniocervical fusion with or without transoral odontoid resection.
Chiari II malformation
- Surgical decompression of cervical canal if treatment indicated: Unlike Chiari I malformation, the bony decompression focuses on the area of hindbrain herniation (i.e., upper cervical spine) and generally need not involve the posterior fossa or foramen magnum. These structures are not involved in the symptomatology of this entity, and the risk of injuring the torcular is high. Cervical laminectomy to the level of the lowest hindbrain tissue is sufficient.
- Care by pediatric neurosurgical specialist: Unlike the Chiari I malformation, patients with Chiari II malformation should always be referred to a center and pediatric neurosurgeon experienced with this pathology because of the complex anatomy and significant possibility of neurological injury.
- Insure shunt for hydrocephalus functional: Intraoperative shunt exploration should be performed or at least strongly considered prior to decompression for Chiari II malformation. Symptoms from a shunt malfunction in these patients can mimic Chiari II malformation symptoms, and a shunt revision poses much less risk. Generally, shunt taps and appearance on radiographs should not be used as proof of shunt function in these patients. Instead, surgical shunt exploration is preferred. It is the experience of many of the Chiari experts that since the recognition that shunt malfunction can occur without ventriculomegaly (10) and can mimic Chiari II malformation symptoms, there has been a sharp decline in the number of decompressions performed for Chiari II malformations.
- Routine and 3-month MRI: Initial follow-up should take place 1–2 weeks after surgery for clinical evaluation and suture removal. An MRI scan should be obtained at 3 months.
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