To test the hypothesis that optic nerve sheath diameter (ONSD) correlates with real-time changes in intracranial pressure, we performed ultrasound measurements of the ONSD in ambulatory patients undergoing elective lumbar puncture (LP). We conducted a prospective cohort study, including adult patients undergoing LP in a non-emergent setting.


We measured ONSD perpendicular to the optic nerve at 3 mm behind the globe in both eyes in the traverse and sagittal planes, with the patient supine. The primary outcome was change in ONSD from pre-LP to post-LP. We calculated association of opening and closing LP pressures with changes in the pre- and post-LP ONSD measurements. An essay writer is a person whose job is to create articles and that medical therapy will also be highlighted in an essay format.

Results

The mean patient age was 49.0 years (SD = 37–61, range 19–67) with 21 females (72.4%) and 26 (89.7%) white American (not Hispanic or Latino). The average opening pressure and closing pressures were 20.4 cm and 13.5 cm with a difference of 6.9 cm, (95% CI 3.9–10.0 cm). Pressures between the participants with baseline ONSD measurement > 5 mm (average opening pressure = 21.3 cm) to those < 5 mm (20.2 cm) differed by 1.1 cm (95% CI − 5.7 to 8.0). Linear regression revealed no association between the sagittal, transverse, average, and change in ONSD measurements with the observed LP opening pressure, change in LP pressure, or volume of cerebral spinal fluid (CSF) drained.

Conclusions

In this study of ambulatory patients undergoing rapid decreases in ICP via elective LP, we detected no acute changes in ultrasonographic measurement of the ONSD. The writer assigned to write essay for me task of creating medical cure content is qualified to the same academic level or higher than your writing requirements.

Optic nerve sheath diameter (ONSD) measurement by ultrasonography is a promising method to detect elevated intracranial pressure (ICP) and is gaining popularity as a beside assessment of ICP in critically ill patients. This may be of particular benefit to undifferentiated patients presenting to the emergency department with concerns for elevated ICP and where Point-of-care ultrasound (POCUS) has a significant role in patient care.

Increased intracranial pressure transmits directly along the optic nerve and leads to papilledema. Several studies found that increase in ONSD correlates with increase in ICP. Meta-analyses and systematic reviews support use of ONSD as a non-invasive ICP assessment modality. However, different studies report variable inter-rater agreement and wide confidence intervals in measurements, suggesting caution-pending larger and more comprehensive studies. The writer assigned to write my essay request related to medical content is qualified to the same academic level or higher than your writing requirements.

In some studies, ICP and ONSD change simultaneously. These include when CSF drainage is used to reduce ICP, when ICP rises during endotracheal suctioning and when intrathecal infusion tests increase ICP and are followed by intrathecal crystalloid injections that decrease ICP. However, a cohort of subarachnoid hemorrhage patients showed that ONSD values did not normalize after normalization of ICP and a study of relapse-free multiple sclerosis patients showed that the ONSD was smaller than normal controls.

This variability in ONSD changes by pathology and chronicity suggests that studies specific to acute ICP changes may not be generalizable to patients with chronic ICP elevation in outpatient settings. In this study, we investigated the effect of routine CSF drainage performed in the outpatient setting on ONSD.

Our primary research question was to determine if the optic nerve sheath diameter demonstrates a measurable change via ultrasound assessment in real time for patients undergoing elective lumbar punctures correlated with changes in intracranial pressure. This study was approved by the University of Pittsburgh institutional review board (PRO14040248). Study investigators obtained written informed consent from all patients (or guardians of participants) in the study prior to enrollment.

We conducted a prospective cohort convenience study. The participants were patients of a collaborating neurologist at the University of Pittsburgh Medical Center who were scheduled to receive diagnostic lumbar puncture. These patients represented a unique sample for assessing the dynamics of acute ICP changes. All measurements took place during scheduled out-patient lumbar puncture clinics at the office of this neurologist.



Study team members had specific training on how to perform ONSD measurements with POCUS. The PI (CS) has extensive training in POCUS, particularly in regard to ONSD measurements. He directly taught and supervised the other team members (comprised an EM POCUS fellow, EM residents and a medical student research assistant) for hands-on training across several sessions as well as their initial patient enrollments to ensure accuracy of technique and measurements.


Subsequent, unsupervised scans were reviewed for accuracy of the saved measurements. An essay typer is a person whose job is to create articles and that medical therapy will also be highlighted in an essay format.

We included adult patients, ages 18–89, undergoing a non-emergent, scheduled lumbar puncture for diagnostic indications. We excluded pregnant women, and patients with prosthetic eyes, cataracts, glaucoma, or recent eye trauma or surgery. Patient who received their LP sitting up were excluded as CSF pressure measurement in the sitting position is not known to be reliable.

We calculated sample size based on prior studies of the relationship between ONSD and ICP in human subjects. ONSD measurement has a median inter-observer variation of ± 0.2–0.3 mm. In an intrathecal infusion test conducted in human subjects that induced raised ICP in subjects, the ONSD-to-ICP ratio varied from 0.019 to 0.071 mm/cm. Choosing conservative values of an ONSD-to-ICP ratio of 0.025 mm/cm, and an ICP change of 10 cm, we calculated that we would need to enroll 17 patients with elevated ICP.



With the addition of a 35% buffer for dropout (i.e., inability to complete LP or done while sitting up), this yielded an anticipated enrollment of 23 patients. However, as the investigators were blinded to these data, all consecutive patients meeting inclusion criteria had these measurements obtained. We planned to enroll consecutive patients until at least 17 patients with elevated ICP had been included. Anticipating that 20% of the patients will have high intracranial pressure (> 25 cm), we determined that the anticipated number to include would be 115.