Arachnoiditis-MRI Findings

MRI is the study of choice for the diagnostic evaluation of arachnoiditis. T1-weighted MRIs may reveal an indistinct or absent cord outline due to the increase in the signal intensity of the surrounding CSF. T2-weighted MRIs may demonstrate CSF loculation and obliteration of the subarachnoid space or irregularly thickened, clumped nerve roots, which occasionally may be misinterpreted as a tethered cord or a thickened filum terminale. With more severe arachnoiditis, progression of nerve root clumping and leptomeningeal adhesions may lead to angular defects in the dural sac. Peripheral adherence of the nerve roots to the walls of the thecal sac produces the so-called featureless, or empty, sac.
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