Preparation for Surgery for Chiari Malformations in Children

Indications for Surgery

Chiari I malformation

• Neurological signs: The presence of neurological deficits, especially if progressive, is an indication for surgery.
• Syringomyelia: Most, but not all, surgeons consider the presence of syringomyelia to be an indication for surgery.
• Intractable symptoms that are debilitating: Severe intractable symptoms that are debilitating the patient are an indication for surgery. The caveat, however, is to make sure that the symptoms are typical for Chiari I (such as Valsalva-induced occipital headaches). Atypical symptoms such as frontal headaches may not improve with surgery.
• Insure ICP normal before treating: ICP monitoring, which can be minimally invasive, should precede decompression if there is questionable elevation in ICP (pseudotumor cerebri occasionally accompanies Chiari I malformation). Other pathological conditions such as hydrocephalus or mass lesion should always be treated prior to performing a decompression for Chiari I malformation.

Chiari II malformation

• Chiari symptoms and functioning shunt

Preoperative Orders

Chiari I malformations

• Routine

Chiari II malformations

• Evaluation lower cranial nerves: It can be quite useful to consider preoperative brainstem auditory evoked potentials as well as sleep study, swallow study, and consultation with otolaryngology for direct laryngoscopy.

Anesthetic Considerations

Chiari I malformations

• Excessive blood loss: Patients undergoing posterior fossa decompressions are at risk of blood loss from a large occipital sinus (especially infants). Adequate preparation for bleeding and air emboli should be initiated, including arterial line, blood type and screen, etc.

Chiari II malformations

• Respiratory compromise: Experienced pediatric anesthesiologists should be involved as these infants and children often have respiratory compromise from their disease.

Devices to Be Implanted

• Dural substitute: Dural graft substitutes are used at some institutions.

Ancillary/Specialized Equipment

• Neuromonitoring: Brainstem auditory evoked potentials are used at some centers.
• Ultrasound: Ultrasound can be used during surgery to assess CSF flow from the fourth ventricle outlet foramina and to help determine if CSF pulsations are present. This information has been used to guide the extent of surgical intervention by some centers.