ASHEVILLE, N.C. — If you suspect a postdural puncture headache but aren't sure, order a T1-weighted MRI with gadolinium contrast for the patient, David C. Mayer, M.D., advised at the Southern Obstetric and Gynecologic Seminar.
“It used to be that there were no imaging studies available to make the diagnosis of postdural puncture headache. That has now changed,” said Dr. Mayer, a professor of obstetrics and gynecology and of anesthesiology at the University of North Carolina at Chapel Hill.
Signs of postdural puncture headaches (PDPH) cannot be seen on CT scans (with and without contrast) or noncontrast MRI.
MRI (T1 weighted) with gadolinium contrast, however, reveals changes that can make a difference in the diagnosis of PDPH. This particular type of MRI rules out more serious conditions, such as subdural hematoma and intracranial masses. The two key findings using T1-weighted contrast MRI are meningeal enhancement and descent or sagging of the brain. Diffuse meningeal enhancement is seen on the MRI. “The meninges … light up with gadolinium,” Dr. Mayer explained.
Less frequently, the pituitary may appear large—though this can be seen with CT as well—and engorged cerebral venous sinuses may also be seen.
Downward displacement of the brain can also be seen (similar to a Chiari malformation) with this type of imaging. There may also be descent of the cerebellar tonsils, obliteration of prepontine, perichiasmatic cisterns, flattening of the optic chiasm, crowding of the posterior fossa, as well as decreased ventricular size, according to Dr. Mayer.
PDPH onset commonly occurs while the patient is in the hospital. The headache usually has a postural component—worsening on standing and decreasing in a prone position. Other common symptoms include neck pain, nausea and vomiting, changes in hearing, and visual blurring or field cuts. However, atypical symptoms include interscapular pain, low-back pain, face numbness or weakness, galactorrhea, and radicular upper-limb symptoms.
“What people are now learning is that it is not just a pressure problem, it's a volume problem,” Dr. Mayer said.
CSF volume is a very well-regulated system. When volume changes occur, the system compensates. Intracranial veins dilate to maintain intracranial volume. Extensive venodilation may exert pressure on pain-sensitive structures (such as the meninges). The pituitary may enlarge. Brain sag—possibly as a result of reduced CSF pressure/volume—can compress and stretch structures and veins in the brain, leading to an increased risk of subdural hematoma.