![]() ![]() To our knowledge, no study has confirmed that there is more space in the posterior thecal sac at C1–C2 with neck extension over flexion or with prone-versus-supine positioning. 8 Recently, thin-section MR imaging techniques have been used to assess cervical spinal canal dimensions in healthy volunteers. 5 ⇓– 7 Measurements of the posterior cervical thecal sac are reported with x-ray myelography, with mention of a subjective change in dural configuration and lack of subjective movement of the cord at the C1–C2 level on flexion and extension. That the diameter of the spinal canal varies on imaging with neck position, notably in flexion or extension, is well-documented however, these studies are focused on the mid- and lower cervical spine in regard to stenosis from spondylotic change. 3 As a result, the size of the posterior thecal sac in various neck positions during puncture is of interest. Under fluoroscopic guidance, the needle is advanced into the posterior thecal sac between the C1 and C2 vertebrae at approximately the junction of the anterior two-thirds and posterior one-third of the spinal canal. This positioning may also be used for C1–C2 puncture for CSF sampling, though there is no contrast as in myelography to warrant the extended neck position. 3, 4 Neck extension is helpful in the prevention of intrathecal contrast spilling into the intracranial space. 1, 2Ĭ1–C2 puncture for myelography is often performed with the patient in the prone position with the neck extended, though the procedure can be performed with patients in the lateral decubitus and supine positions. Disadvantages include a slightly increased risk of damage to nearby structures such as the spinal cord, vessels, or nerves. Additionally, cervical puncture can be helpful to delineate the upper margin of an obstructive mass within the spinal canal below the cervical level. Administering contrast via cervical puncture has several advantages, including less dilution of contrast within the cervical canal, better control of contrast to prevent intracranial spillage, and the ability to perform the procedure with the patient in a prone or supine position. For cervical myelography, cervical puncture may actually be the preferred method for instillation of intrathecal contrast.Īlthough its use is being curbed by heavily T2-weighted, high-resolution MR imaging techniques, cervical myelography is still indicated in patients who have a contraindication to MR imaging or equivocal findings on MR imaging or who have failed MR imaging. In these cases, cervical puncture may be performed as an alternative. These include patients with severe lumbar spondylosis, extensive bony lumbar fusion, lumbar canal stenosis, spinal dysraphism, extensive lumbar hardware, and lumbar epidural abscess. There are subsets of patients, however, in whom lumbar puncture is not possible or is contraindicated. Often the approach for accessing the thecal sac for CSF sampling or myelography is via lumbar puncture. ABBREVIATION: SPACE sampling perfection with application-optimized contrasts by using different flip angle evolution ![]()
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