Increased signal in the subarachnoid space on fluid-attenuated inversion recovery imaging associated with the clearance dynamics of gadolinium chelate: a potential diagnostic pitfall

Abstract

Background and purpose: Hyperintense CSF in the subarachnoid space (SAS) on fluid-attenuated inversion recovery (FLAIR) imaging has been reported in numerous pathologic conditions, including subarachnoid hemorrhage, meningitis, meningeal carcinomatosis, superior sagittal thrombosis, adjacent tumors, status epilepticus, and stroke. It has also been reported in otherwise healthy patients undergoing anesthesia with supplemental oxygen. We present a series of 11 patients with hyperintense CSF signal intensity in the SAS on FLAIR imaging after previous administration of gadolinium chelate.

Materials and methods: Head MR images of patients who had a prior gadolinium-enhanced body, spine, or brain MR imaging and who had increased signal intensity in the SAS on FLAIR images were prospectively and retrospectively reviewed. Correlation was made with the clinical and laboratory findings.

Results: Eight of the 11 patients had negative findings on lumbar punctures. Seven patients had either chronic renal insufficiency or acute renal failure, but the remaining 4 had normal renal function. Nine patients had no other significant intracranial abnormalities, and 2 patients had acute infarcts remote from the CSF hyperintensity. One patient had follow-up studies at 24 and 48 hours, documenting resolution of the CSF hyperintensities.

Conclusion: Given the sharp rise in volume of contrast-enhanced MR imaging studies, it is inevitable that some patients will have undergone a contrast-enhanced MR imaging 24-48 hours before an MR imaging of the brain. The neuroradiologist should be aware that previous administration of gadolinium chelate can cause increased signal intensity in the SAS on FLAIR imaging in patients with or without a history of renal insufficiency and without abnormalities known to disrupt the blood-brain barrier.

Fig 1.

A 74-year-old man with normal renal function who underwent a gadolinium-enhanced MR imaging of the head and MR angiography (MRA) of the neck because of a transient ischemic attack and who had a follow-up head MR imaging the next day. A, Normal MRA findings of the neck. B, Precontrast axial FLAIR image shows no signal intensity in the SAS on the date of the gadolinium administration. C, Repeat noncontrast coronal FLAIR image 24 hours later shows increased signal intensity in the SAS. The patient had an emergent lumbar puncture, which was negative for subarachnoid hemorrhage, infection, or malignant cells.

Fig 2.

A 21-year-old man with chronic renal insufficiency who underwent gadolinium-enhanced MRA of the abdomen followed by MR imaging of the brain 6 days later to rule out causes of syncope. A, Normal findings on abdominal MRA. B, Precontrast FLAIR image shows diffuse increased signal intensity in the SAS 6 days after the gadolinium injection. The patient had an emergent lumbar puncture, which was as negative for subarachnoid hemorrhage, infection, or malignant cells.

Fig 3.

An 81-year-old man with normal renal function who underwent a triple-dose (60 mL) 3D MRA of the spine to exclude a dural arteriovenous fistula, followed by MR imaging of the brain 24 hours later for a syncopal episode. Upper thoracic (A) and thoracolumbar (B) spinal MRA images demonstrate no evidence of a dural arteriovenous fistula. C, Precontrast FLAIR image shows increased signal intensity in the SAS and in the lateral ventricles 24 hours after gadolinium injection. The patient returned to the department and was imaged a second time due to the T2 spin-echo appearance to ensure that there was not a technical error in the initial FLAIR sequence and was found to have similar results.

Fig 4.

A 79-year-old man with normal renal function evaluated for a transient ischemic attack. A, Precontrast axial FLAIR image shows no abnormal signal intensity in the SAS. B, Forty-eight hours postgadolinium injection, repeat MR imaging shows diffuse increased signal intensity in the subarachnoid space (SAS) on coronal FLAIR images due to delayed clearance of the gadolinium chelate. C, Repeat MR imaging 72 hours postgadolinium injection shows resolution of the increased signal intensity in the SAS.