Porencephaly

PHOENIX, ARIZ. -- Clinicians "can learn a lot" by using magnetic resonance imaging in conjunction with ultrasound to diagnose central nervous system abnormalities, Dr. Deborah Levine said at the annual meeting of the American Institute of Ultrasound in Medicine.

MRI can offer additional information concerning anatomical details that are important for counseling patients, said Dr. Levine, director of obstetric and gynecologic ultrasound in the department of radiology at Beth Israel Deaconess Medical Center, Boston.

For example, in a case of ventriculomegaly, MRI can help clinicians examine regions of porencephaly. But Dr. Levine was quick to point out that clinicians should be cautious in counseling patients about what MRI might be showing. "We don't know the natural history of all of these abnormalities," she said. "Although we will tell patients that we'd rather not have porencephaly, we can't tell them what it means when there's a focal area of porencephaly [other than] that the prognosis will be worse than if we hadn't seen it."

She discussed the case of a 26-week-old fetus with a large arachnoid cyst that was referred to her clinic to check for possible schizencephaly. Ultrasound showed "what looked like a very large cyst pushing the ventricles [in the brain] aside," she said. MRI revealed that the arachnoid cyst went across the midline of the brain and elevated both cerebral hemispheres, "but it clearly did not communicate with the ventricles."

A sagittal view on MRI showed a "mass effect" that the cyst was having on the pons and the midbrain. "But the question is, what do you do with that information?" Dr. Levine asked. "For this fetus, we counseled the patients that we were concerned about how the baby would do at birth. Would it be able to breathe? Would it be able to feed normally because of all this mass effect?"

She and her associates took follow-up MRI images of the child's head at 4 and 12 months of age. The arachnoid cyst stayed the same size; the child never needed surgery and was asymptomatic.

She added that using MRI has helped her to identify intratentorial hematomas that had previously been misdiagnosed as arachnoid cysts based on ultrasound exams alone. The key diagnostic difference between the two is that "arachnoid cysts hug the brain and intratentorial hematomas hug the bone," Dr. Levine said.

BY DOUG BRUNK

San Diego Bureau

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