LAUSR

Direct measurements of intracranial pressure (ICP) by lumbar puncture (LP) remain the criterion standard for diagnosing, following, and treating specific neurologic, neurosurgical, and neuro-ophthalmic conditions with elevated ICP. In this issue of JAMA Ophthalmology, Wang et al1 used ultrasonography to document optic nerve sheath diameter (ONSD), and their results reported a correlation between noninvasive ultrasonography and dynamically monitored ICP. The ONSD was measured before LP in 60 patients on admission. Patients with elevated ICP were divided into 2 groups: group 1 (200 < LP ≤ 300 mm H2O) and group 2 (LP > 300 mm H2O). Patients underwent follow-up ONSD and LP measurements within 1 month. For the 60 patients on admission, the ONSD and ICP values were strongly correlated. In addition, the follow-up evaluations after treatment revealed that the elevated ICP and dilated ONSD had returned to normal. The use of ultrasonography has been reported previously as a potential noninvasive test for elevated ICP. This study adds further evidence for the sensitivity and specificity of ultrasonography for this purpose. I already use orbital ultrasonography for supporting a diagnosis of elevated ICP in the following common clinical circumstances in neuro-ophthalmology including (1) differentiating difficult cases of pseudopapilledema vs papilledema (especially with borderline elevated ICP on LP), (2) following patients with proven papilledema and elevated ICP with residual posttreatment disc changes (eg, disc elevation without obligatory signs of increased ICP) for whom repeated LP might be undesirable or unnecessarily invasive or painful, (3) evaluating patients with significant postpapilledema or another optic atrophy with possible elevated ICP for whom the papilledema may no longer be able to manifest ophthalmoscopically (ie, “a dead nerve can’t swell”), (4) evaluating patients with cerebrospinal fluid shunts for elevated ICP due to possible shunt malfunction, and (5) following patients who refuse or cannot undergo a standard LP for measuring ICP (eg, patients who are taking anticoagulation or antiplatelet agents or have intracranial lesions that have a mass effect on neuroimaging studies). In this study,1 the 2 groups (less and more than 300 mm H2O ICP) were able to be differentiated by ONSD on ultrasonography, but further work will be necessary to determine if the study results are generalizable to lower or higher levels of ICP.