Meningeal Enhancement post Lumbar Puncture
LP is frequently delayed till contrast MRI is done, on the grounds that; recent LP may lead to spurious meningeal enhancement on MRI. While this phenomenon is frequently cited in clinical practice, review of the literature reveals that there are only two studies to date investigating the claim that uncomplicated LP procedure can cause meningeal enhancement.63,64 In 1994, Mittl et al. performed an ambi-spective study of patients who had an LP performed within 30 days before a contrasted brain MRI. However, they did not compare their cases to a control group. Only 2 cases had meningeal enhancement on MRI (one out of eleven in the retrospective group and one out of 97 in the prospective group), wherein lumbar puncture was performed 30 days prior to contrasted MRI. However, a traumatic tap and intracranial hypotension arguably explained these 2 cases of unexplained pachymeningeal enhancement.63
In a retrospective study, Weasley et al. analysed contrast enhancement on MRI brain in patients, who had LP before imaging which served as cases (77 cases) and compared them to controls in whom LP was not done before MRI (707 controls).Out of 77 cases , only one had unexplained meningeal enhancement(1.2%). Of the 36 patients in the control group who had enhancement, none of it were unexplained (p=0.098).64 So, the deferring of LP until after brain MRI probably may not be helpful in situations where performing LP is vital.