Is the Optic Nerve Head Structure Impacted by a Diagnostic Lumbar Puncture in Humans?
We read with great interest the study by Poli et al,1 who evaluated whether a diagnostic lumbar puncture (LP) is followed by optic nerve head (ONH) and parapapillary anatomic changes in 16 eyes of 8 nonglaucomatous patients using a swept-source optical coherence tomography (OCT) device. They found that none of the evaluated structures, including the anterior surface of lamina cribrosa (LC) and Bruch membrane opening (BMO), showed any anatomic changes at any timepoint after LP.
We have recently reported significant ONH changes by enhanced depth imaging OCT in a prospective longitudinal study, including 12 eyes newly diagnosed of papilledema. Translaminar pressure difference (TLPD), calculated as intraocular pressure (IOP) minus the lumbar cerebrospinal fluid pressure (CSFP), was inversely correlated with anterior LC position at baseline, and directly with LC reversal movement after lowering CSFP and edema resolution. Eyes with higher TLPD showed apart from a significantly larger backward LC movement, a larger BMO shrinking after lowering CSFP compared with eyes with lower TLCD.2 A similar relationship between TLPD and LC position has been reported in a retrospective study by Villarruel et al3 in 11 eyes with idiopathic intracranial hypertension.
Poli and colleagues concluded that diagnostic LP, with a median cerebrospinal fluid extracted volume of 1.65 mL, was a safe procedure regarding deep ONH structures in nonglaucomatous subjects. However, the authors did not mention any data about the CSFP, IOP, or the TLPD. Differences in the design and purpose between our study and Poly and colleagues study are evident (a LP in healthy subjects vs. patients treated with papilledema), but it seems reasonable, according to the above-mentioned findings, to hypothesize that a PL in patients with papilledema could also significantly affect to ONH structures, above all if we keep in mind that there is a linear relationship between the volume of CSF removed and the amount of CSF pressure relieved.4 Therefore, we want to stress that the conclusion by Poly and colleagues cannot be extrapolated to patients with intracranial hypertension.
In Poli and colleagues study, a bed rest in the prone posture was recommended for 2 hours to minimize post-LP headache. However, OCT scanning was repeated at 5 and 60 minutes, so patient had to be seated at least twice during this postpuncture period. This point must be clarified, so both IOP and CSFP reduced when moving from supine to sitting.5 Furthermore, the level of both CSF pressure and TLPD should be taken into account in future research.