Article, Ophthalmology

Real-time optic nerve sheath diameter reduction measured with bedside ultrasound after therapeutic lumbar puncture in a patient with idiopathic intracranial hypertension

Unlabelled image

optic nerve sheath diameter r”>Case Report

Contents lists available at ScienceDirect

American Journal of Emergency Medicine

journal homepage: www. elsevier. com/ locate/ajem

American Journal of Emergency Medicine 33 (2015) 860.e5-860.e7

Real-time optic nerve sheath diameter reduction measured with bedside ultrasound after therapeutic lumbar puncture in a patient with idiopathic Intracranial hypertension

Abstract

idiopathic intracranial hypertension (IIH), also referred to as pseudotumor cerebri, is a condition of raised intracranial pressure with unknown etiology. sonographic measurement of optic nerve sheath diameter has been shown to be a reliable, noninvasive method to characterize elevated ICP in a variety of settings. However, little is known about the immediate response of ONSD to an acute re- duction in ICP after lumbar puncture. We describe a case of an emergen- cy department patient with IIH in whom we identified real-time change in ONSD correlated with a decrease in cerebrospinal fluid pressure after a therapeutic lumbar puncture. Ocular ultrasound and ONSD measure- ments were performed by a trained provider using a 9- to 13-MHz lin- ear transducer and an ultrasound machine with ocular software package and low mechanical index settings for data collection (MTurbo; SonoSite Inc, Bothell, WA). The ONSD was measured 30 minutes prior to and 30 minutes after a therapeutic lumbar puncture. Opening and clos- ing pressures were recorded. Optic nerve sheath diameter measure- ments correlated with ICP as measured by opening and closing lumbar puncture pressures and showed an acute reduction in ONSD within 30 minutes after lumbar puncture. Sonographic measurement of ONSD re- duction may be a novel, noninvasive and convenient way to follow acute reductions in ICP. Further investigation is necessary in order to validate this finding.

Idiopathic intracranial hypertension (IIH), formerly known as Benign intracranial hypertension and commonly referred to as pseudotumor cerebri, is a condition of raised Intracranial pressure of unknown etiology. The annual incidence of IIH has been reported to be 0.9 to 1.6 per 100 000 in the United States [1], but increases to 19/100 000 among women 20 to 44 years old who are more than 20% above ideal body weight [2]. Diagnosis of IIH is made by the revised Modified Dandy Criteria [3].

Ocular ultrasound has been explored as a noninvasive method of evalu- ating for raised ICP in patients with a headache and risk factors for IIH. Its use for evaluation of intracranial hypertension was first postulated in 1996 when Helmke and Hansen [4,5] observed in two studies that injecting gelatin into the perineural subarachnoid space (SAS) of cadaver optic nerve specimens was directly correlated with an increase in optic nerve sheath di- ameter (ONSD), as measured with a linear ultrasound probe over the orbit. The authors found that when using a high-frequency linear transducer, ONSD measurements could be obtained with a resolution of less than 0.5

mm. They validated their findings in a subsequent study assessing 24 patients admitted to a pediatric neurosurgical intensive care unit [6].

Since these seminal studies were published, multiple authors have explored the use of ocular ultrasound to detect elevated ICP noninva- sively and reliably with sonography for conditions such as traumatic and nontraumatic intracranial hemorrhage, cerebral venous sinus thrombosis, and IIH [7-13].

Despite the growing body of literature focusing on more exact sono- graphic ONSD cutoff values for ICP N 20 cm H2O, few investigators have evaluated the use of measuring declining ONSD or changes in ONSD as a surrogate for effective treatment or reduction in ICP. Hence, it is still largely unknown how accurately this technique correlates with fluctu- ating or decreasing ICP, such as in patients with IIH after lumbar punc- ture (LP). A case report by Lochner and colleagues [14] in 2013 demonstrated a reduction of ONSD as well as resolving optic disc eleva- tion in a patient with IIH after 12 months of medical management. In 2011, Hansen and colleagues [15] worked on quantifying the effect of gelatin injection into the SAS of cadaveric optic nerve preparations. In vitro, they showed that rapid decompression of the SAS decreased ONSD within a few minutes and was quantifiable with sonography. However, they suggested that the sheath diameter reversibility may be impaired after prolonged episodes of intracranial hypertension and sustained ICP loads of 45 to 55 mmHg. There are no current clinical data to substantiate this finding.

We describe the case of an emergency department (ED) patient with IIH and ultrasonographic measurement of ONSD performed 30 minutes prior to therapeutic LP and 30 minutes afterward.

We had the opportunity to measure both the opening and closing pres- sures by manometry in a patient with IIH. A trained provider also sonographically measured the ONSD in accordance with previously pub- lished methods [7,16] 30 minutes before and 30 minutes after the LP. We used a 9- to 13-MHz high-frequency linear transducer and an ultrasound machine with ocular software package and low mechanical index settings for data collection (MTurbo; SonoSite Inc, Bothell, WA).

The patient was in the supine position for pre- and post-LP ONSD mea- surements, and the linear transducer was placed over the closed eye, with copious gel applied over the eye lid to avoid pressure on the eye. The scan- ning field was adjusted to view the entry of the optic nerve into the globe. The ONSD was measured 3 mm behind the globe, in an axis perpendicular to the optic nerve. Two measurements were made in the transverse plane and in the sagittal plane. The reported measurement for each nerve corre- sponds to the mean of multiple ONSD measurements.

A 25-year-old woman previously diagnosed as having IIH presented to the ED with a 2-day history of progressive headache, nausea, vomiting, and intermittent blurry vision. The patient had been pre- scribed acetazolamide several months prior to presentation but

0735-6757/(C) 2014

860.e6 J. Singleton et al. / American Journal of Emergency Medicine 33 (2015) 860.e5860.e7

image of Figure

Figure. Using a 9- to 13-MHz linear transducer, ultrasound images of the right eye were obtained before (A) and after (B) LP. ONSD is measured 3 mm behind the retina, encompassing the full diameter of the hypoechogenic stripe representing the optic nerve sheath.

admitted to poor compliance due to adverse effects. The week prior to presenting to the ED, her treating neurologist transitioned her to methazolamide with minimal symptom relief.

In the ED, the patient’s physical examination was unremarkable, except for trace papilledema with obscuration of the superior, inferior, and temporal aspects of the optic disc margins bilaterally. Her visual acuity was 20/40 (OD) and 20/30 (OS). Given that the patient’s history and physical examination were highly consistent with untreated IIH, and recent negative magnetic resonance imaging and magnetic reso- nance venography, we did not pursue further imaging.

After informed consent was obtained, an ocular ultrasound was per- formed using a 9- to 13-MHz linear transducer probe 30 minutes prior to the planned LP. Pre-LP measurements of the left and right eye ONSD were 7.2 and 6.8 mm, respectively. The patient then underwent an LP with opening pressure of 36 cm H2O and closing pressure of

19.5 cm H2O after removal of 19 cc of clear, colorless cerebrospinal fluid (CSF). A second ocular ultrasound was performed 30 minutes af- terward. Optic nerve sheath diameter measurements in the left and right eyes were 5.8 and 6.2 mm, respectively (Figure). There were no immediate complications from either procedure.

The patient’s symptoms improved over the next 60 minutes after CSF removal, and she was discharged home on methazolamide with follow-up in neurology and neuro-ophthalmology clinics.

To our knowledge, our case report is the first of its kind to demon- strate real-time changes in ONSD measured within 30 minutes of a ther- apeutic LP in a patient with a diagnosis of IIH in the ED setting, with correlation of these changes to opening and closing pressure changes as well as clinical symptoms. The patient had an ONSD reduction of

1.4 mm in the left eye and 0.6 mm in the right eye 30 minutes after re- moval of 19.5 cc of CSF, correlating with a reduction in measured CSF pressure of 16.5 cm H2O. The patient also reported improvement of clin- ical symptoms within 60 minutes after LP. Our findings would support the in vitro study results of Hansen and colleagues [15] in 2011 that showed acute ONSD reduction within minutes of decompression of the SAS using removal of gelatin. However, no human studies thus far have demonstrat- ed real-time changes in ONSD following a therapeutic LP.

The correlation between therapeutic LP and reduction in ONSD has been seen in patients up to within 1 day of the procedure. Bauerle and Nedelmann [10] showed ONSD reduction after therapeutic LP within this time frame in 10 subjects with newly diagnosed IIH. Although Bauerle and Nedelmann were able to demonstrate bilateral decrease

in ONSD after removal of 30 to 50 mL CSF within 1 day postprocedure, they found that the degree of ONSD response to therapeutic LP was var- iable in subjects with IIH. They concluded that a defective CSF circula- tion in the optic nerve sheath in some patients with IIH, referred to as optic nerve compartment syndrome, may have affected their results.

There are numerous advantages to the use of noninvasive ICP mea- surement by ocular ultrasound vs invasive ICP measurement by intraparenchymal and intraventicular transducers, including conve- nience, availability, and noninvasiveness. In addition, it has been shown that physicians can be easily taught these point-of-care ocular ultrasound applications and show excellent interobserver reliability [13,17].

In summary, we report a patient with IIH in whom we compared direct ICP measurements by manometry at LP with real-time decrease in ONSD as measured by noninvasive ocular ultrasound. This finding suggests that the ONSD is a possible means for assessment of real-time reduction in ICP, up to within 30 minutes of pressure changes. In order to validate this finding, it would be ideal to design a large study comparing pre-LP and post-LP ONSD in patients undergoing therapeutic LP for treatment of IIH.

Acknowledgments

We would like to acknowledge the efforts of Dr Terrance Lee, MD, and Dr Nicole Dubosh, MD, for their contributions to the research and data collection for this case report.

Jennifer Singleton, MD?

Alon Dagan, MD Jonathan A. Edlow, MD Beatrice Hoffmann, MD, PhD

Department of Emergency Medicine at Beth Israel Deaconess Medical Center

Harvard Medical School, Boston, MA

?Corresponding author: Department of Emergency Medicine Administration, Beth Israel Deaconess Medical Center, 1 Deaconess Rd

Boston MA 02215

Email addresses: [email protected] (Singleton J.)

[email protected] (Dagan A.) [email protected] (Edlow J.) [email protected] (Hoffmann B.)

http://dx.doi.org/10.1016/j.ajem.2014.12.030

J. Singleton et al. / American Journal of Emergency Medicine 33 (2015) 860.e5860.e7 860.e7

References

  1. Radhakrishnan K, Ahlskog JE, Cross SA, Kurland LT, O’Fallon WM. Idiopathic intracra- nial hypertension (pseudotumor cerebri). Descriptive epidemiology in Rochester, Minn, 1976 to 1990. Arch Neurol 1993;50(1):78-80.
  2. Durcan FJ, Corbett JJ, Wall M. The incidence of pseudotumor cerebri. Population studies in Iowa and Louisiana. Arch Neurol 1988;45(8):875-7.
  3. Friedman DI, Jacobson DM. Diagnostic criteria for idiopathic intracranial hyperten- sion. Neurology 2002;59(10):1492-5.
  4. Helmke K, Hansen HC. Fundamentals of transorbital sonographic evaluation of optic nerve sheath expansion under intracranial hypertension. I. Experimental study. Pediatr Radiol 1996;26(10):701-5.
  5. Hansen HC, Helmke K. The subarachnoid space surrounding the optic nerves. An ultrasound study of the optic nerve sheath. Surg Radiol Anat 1996;18(4):323-8.
  6. Helmke K, Hansen HC. Fundamentals of transorbital sonographic evaluation of optic nerve sheath expansion under intracranial hypertension II. Patient study. Pediatr Radiol 1996;26(10):706-10.
  7. Blaivas M, Theodoro D, Sierzenski PR. Elevated intracranial pressure detected by bedside emergency ultrasonography of the optic nerve sheath. Acad Emerg Med 2003;10(4):376-81.
  8. Geeraerts TS, Merceron S, Benhamou D, Vigue B, Duranteau J. Non-invasive assess- ment of intracranial pressure using ocular sonography in Neurocritical care patients. Intensive Care Med 2008;34(11):2062-7.
  9. Kimberly HH, Shah S, Marill K, Noble V. Correlation of optic nerve sheath diameter with direct measurement of intracranial pressure. Acad Emerg Med 2008;15(2):201-4.
  10. Bauerle J, Nedelmann M. Sonographic assessment of the optic nerve sheath in idio- pathic intracranial hypertension. J Neurol 2011;258(11):2014-9.
  11. Dubourg J, Javouhey E, Geeraerts T, Messerer M, Kassai B. Ultrasonography of optic nerve sheath diameter for detection of raised intracranial pressure: a systematic re- view and meta-analysis. Intensive Care Med 2011;37:1059-68.
  12. Amini A, Kariman H, Arhami Dolatabadi A, Hatamabadi HR, Derakhshanfar H, Mansouri B, et al. Use of the sonographic diameter of optic nerve sheath to estimate intracranial pressure. Am J Emerg Med 2013;31(1):236-9.
  13. Bauerle J, Lochner P, Kaps M, Nedelmann M. Intra- and interobserver reliability of sonographic assessment of the optic nerve sheath diameter in Healthy adults. J Neuroimaging 2012;22(1):42-5.
  14. Lochner P, Nardone R, Tezzon F, Coppo L, Brigo F. Optic nerve sonography to monitor treatment efficacy in idiopathic intracranial hypertension: a case report. J Neuroim- aging 2013;23(4):533-4.
  15. Hansen HC, Lagreze W, Krueger O, Helmke K. Dependence of the optic nerve sheath diameter on acutely applied subarachnoidal pressure–an experimental ultrasound study. Acta Ophthalmol 2011;89(6):528-32.
  16. Kilker BA, Holst JM, Hoffmann B. bedside ocular ultrasound in the emergency department. Eur J Emerg Med. Advance online publication. PMID 24002686.
  17. Blaivas M, Theodoro D, Sierzenski PR. A study of bedside Ocular ultrasonography in the emergency department. Acad Emerg Med 2002;9(8):791-9.