A young female presented to an outside hospital with headache of one day duration. An MR brain study was done and interpreted as showing acute subarachnoid hemorrhage in the right temporal/occipital region. The patient was transferred to our hospital for treatment and before performing a lumbar puncture a head CT was done. The CT was interpreted as normal. CSF was obtained and was also normal.
Analysis of images showed an artifact involving the right lower side of the skull seen only on the DWI, ADC and a T2* sequence. This magnetic susceptibility artifact was found out to have been due to a metal chain. Upon arrival in our CT scanner, the technologists removed the chain to prevent artifacts.
Discussion:
In FLAIR images, an inversion pulse is applied to suppress the normal signal intensity from CSF. Multiple causes result in T2 prolongation of CSF signal making it bright on FLAIR and include: inhaled oxygen, increased proteins due to presence of blood or infection, tumor, propofol, and hyperdynamic pulsations such as those seen in the basilar cisterns particularly around arteries. Artifacts resulting in hyperintense CSF include: motion, inhomogeneity in amplitude of initial inversion pulse, chemical shift, cross-talk, truncation, suboptimal inversion time, overlapping of imaging planes and as in this patient, magnetic susceptibility artifact. Metals may result in incomplete nulling of CSF signal simulating hemorrhage or increased CSF proteins. This is commonly seen in the frontal regions in patients with dental braces.
References:
- Cianfoni A, Martin MGM, Hesselink JR, et al. Artifact simulating subarachnoid and intraventricular hemorrhage on single-shot, fast spin-echo fluid-attenuated inversion recovery imaging caused by head movement: a trap for the unwary. AJNR Am J Neuroradiol 2006; 27: 843-849
- Tha KK, Terae S, Kudo K, Miyasaka K. Differential diagnosis of hyperintense cerebrospinal fluid on fluid-attenuated inversion recovery images of the brain. Part 2: non-pathological conditions. British J Radiol 2009; 82: 610-614
