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.