Tailored operative technique for Chiari Type I malformation using intraoperative color Doppler ultrasonography

Thomas H. Milhorat, Paolo A. Bolognese, Robert G. Grossman, Harold L. Rekate, Ulrich Batzdorf

Research output: Contribution to journalArticlepeer-review

105 Scopus citations


OBJECTIVE: We describe an operative technique for Chiari Type I malformation that uses color Doppler ultrasonography as a guide for performing patient-specific posterior fossa decompressions. The technique has been used since 1999 in more than 300 operations. METHODS: On the basis of real-time anatomic and physiological measurements, the following goals of surgery were monitored: 1) adequate decompression of the cervicomedullary junction; 2) creation of a retrocerebellar space of 8 to 10 cm3 volume; and 3) establishment of optimal cerebrospinal fluid flow between the cranial and spinal compartments. RESULTS: The size of the craniectomy was tailored to conform to the area of cerebellar impaction as demarcated by compressed subarachnoid spaces. A laminectomy was not performed unless the cerebellar tonsils were herniated below C1. Before opening the dura, color Doppler ultrasonography imaging was invaluable in planning operative strategies. A simple duraplasty without additional steps was found to be appropriate treatment in occasional patients with minimal tonsillar herniation (5-8 mm). In all other cases, it was necessary to perform an internal decompression that included lysis of the arachnoid and shrinkage of the cerebellar tonsils to achieve the goals of surgery. Optimal cerebrospinal fluid flow through the foramen magnum in anesthetized, prone patients was found to have the following characteristics: a peak velocity of 3 to 5 cm/s, bidirectional movement, and a waveform exhibiting vascular and respiratory variations. The attainment of surgical goals was confirmed in most patients by postoperative neuroimaging. CONCLUSION: Color Doppler ultrasonography imaging is an important technological advance that permits the neurosurgeon to tailor the steps of Chiari surgery according to patient-specific variables. The success of this technique depends on the mastery of a new and sophisticated monitoring modality.

Original languageEnglish (US)
Pages (from-to)899-906
Number of pages8
Issue number4
StatePublished - Oct 1 2003


  • Cerebrospinal fluid flow
  • Chiari Type I malformation
  • Color Doppler imaging
  • Intraoperative ultrasound imaging
  • Posterior fossa decompression

ASJC Scopus subject areas

  • Clinical Neurology
  • Surgery


Dive into the research topics of 'Tailored operative technique for Chiari Type I malformation using intraoperative color Doppler ultrasonography'. Together they form a unique fingerprint.

Cite this