Journal of Obstetric Anaesthesia and Critical Care

: 2019  |  Volume : 9  |  Issue : 2  |  Page : 65--69

Optic nerve sheath diameter measured using ocular sonography is raised in patients with eclampsia

Renu Bala1, Arnab Banerjee2, Susheela Taxak1, Rajesh Kumar1,  
1 Department of Anaesthesiology and Critical Care, Pt. B.D. Sharma PGIMS, Rohtak, Haryana, India
2 Department of Anaesthesiology and Critical Care, All India Institute of Medical Science, New Delhi, India

Correspondence Address:
Dr. Rajesh Kumar
Department of Anaesthesiology and Critical Care, Pt. B.D. Sharma PGIMS, Rohtak - 124 001, Haryana


Introduction: Eclampsia is one of the leading causes of maternal morbidity. Neurological sequelae are quite common and contribute to poor prognosis in these patients. Ultrasonographic measurement of optic nerve sheath diameter (ONSD) as noninvasive monitor of raised intracranial pressure (ICP) might aid in management of these patients. Based on these facts, this study intended to study the difference between ONSD in eclampsia versus noneclamptic parturients admitted to intensive care unit (ICU). The trends in ONSD were followed in patients with eclampsia to assess the association between ONSD and resolution of neurological symptoms. Materials and Methods: The present observational study comprised 46 patients and was conducted in our ICU from January 2015 to June 2015. Postpartum eclamptic patients requiring ventilatory support in the ICU were enrolled in group E (n = 24), while postpartum patients admitted for some other causes but requiring ventilatory support were enrolled in group C (n = 22). Transorbital ultrasound was done to measure ONSD using SonoSite M-Turbo machine. It was repeated daily in both the groups till patients were extubated or expired. The vital parameters, treatment, and investigations were also noted. Results: The ONSD in group E was 0.64 ± 0.02 cm, while in group C it was 0.45 ± 0.03 cm (P < 0.0001). Blood pressure was much higher in group E (P < 0.001). ONSD had positive correlation with systolic blood pressure than diastolic blood pressure. In group E, 22 patients were extubated, and following extubation ONSD decreased to normal value in 16 patients while in 6 patients it was still raised. Overall mortality was 6 (13%); 2 (8.3%) in group E and 4 (18.2%) in group C. Conclusion: ONSD was higher in patients with eclampsia suggesting raised ICP, and with subsidence of disease process it decreased. Thus, it may be adopted as a routine monitoring in these patients to guide management and predict prognosis, although further studies are required to support our findings.

How to cite this article:
Bala R, Banerjee A, Taxak S, Kumar R. Optic nerve sheath diameter measured using ocular sonography is raised in patients with eclampsia.J Obstet Anaesth Crit Care 2019;9:65-69

How to cite this URL:
Bala R, Banerjee A, Taxak S, Kumar R. Optic nerve sheath diameter measured using ocular sonography is raised in patients with eclampsia. J Obstet Anaesth Crit Care [serial online] 2019 [cited 2020 Jul 6 ];9:65-69
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Full Text


A noninvasive tool which can reliably predict raised intracranial pressure (ICP) is highly desirable in clinical scenarios such as hepatic encephalopathy, eclampsia, and postischemic neuropathy where patients might have raised ICP but use of invasive methods is limited. In the past one decade, ultrasonographic (USG) measurement of optic nerve sheath diameter (ONSD) has proved quite promising not only as diagnostic tool but also providing information regarding prognosis of patients with raised ICP.[1],[2] In normal adults, it is 4–4.5 mm and levels above 5 or 5.5 mm (in some studies) denote raised ICP.[3] A recent meta-analysis has shown it to carry high sensitivity and specificity. The other advantages are that it can be performed bed side, no special equipment (apart from routine ultrasound machine and probe) is required, and it can be repeated many times.[1],[2],[3],[4]

Patients with eclampsia are prone to neurological complications such as cerebral edema, subarachnoid hemorrhage, cerebral ischemia, and infarct which may lead to raised ICP.[5] Thus, monitoring of ICP is very crucial in them; however, the invasive monitoring which is considered as gold standard is either not feasible or contraindicated due to bleeding or coagulation issues.[6] Ultrasonographic measurement of ONSD is of great utility in these patients.[1] In light of these findings, we intended to study ONSD the differences between eclamptic and noneclamptic patients which was the primary objective of our study. The secondary objectives were trends in ONSD over the course of time to analyze whether ONSD reaches normal value with the improvement in patient's clinical condition. Our study was based on the hypothesis that patients with eclampsia will have increased ONSD because of raised ICP.

 Materials and Methods

The present observational study was conducted in the intensive care unit (ICU) of our institution from January 2015 to June 2015 after obtaining approval from institutional ethics committee. A total of 46 postpartum patients admitted to our ICU and requiring mechanical ventilation were enrolled for the study. An informed and written consent was obtained from guardian/kin of the patient for participation in the study. The patients having hyperthyroidism, glaucoma, optic neuroma or neuritis, cerebrovascular disease, and epilepsy (seizure other than eclampsia) were excluded from the study. The patients who were diagnosed cases of eclampsia were assigned group E (n = 24), while others in group C (n = 22). Patient's demographic profile was noted. Mechanical ventilation, blood transfusion, fluid therapy, and drug therapy were followed as per standard protocol of our ICU. All routine investigations deemed necessary were done and standard monitoring was carried out.

On day “0” of admission, transorbital ocular sonography was done to measure ONSD. SonoSite M-Turbo ultrasound machine with linear probe having frequency of 7.5 MHz was used. The intensivist having experience of more than 25 ocular ultrasound for ONSD in normal and in patients with raised ICP performed all the measurements. The patients were laid supine with head raised to 30°. A tegaderm was applied on their closed eyes carefully so that there was no air interface between them. A thick layer of sterile ultrasound gel was applied on it and the probe was placed gently on superior and lateral aspect of the upper eyelid without exerting any pressure. Then, the probe was angled slightly caudally and medially until an axial view of the orbit was obtained displaying entry of optic nerve into the globe. Depth and gain were adjusted accordingly. The image was frozen, and the cursors were placed on the outer contours of the dural sheath, at a retrobulbar position 3 mm behind the globe and perpendicularly to the optic nerve axis. The ONSD was calculated as the horizontal distance between the two cursors [Figure 1]. The average of three readings was taken. Similarly, the process was repeated for the other eye too. Vital parameters (heart rate, systolic blood pressure, blood pressure, and oxygen saturation) were noted.{Figure 1}

The ocular sonography was conducted daily, and ONSD values were noted. It was carried out till patients were discharged from ICU or expired. The length of ICU stay was also noted.

Statistical analysis

The continuous variables were presented as mean and standard deviation and compared using Student's t-test. The categorical data were expressed as frequency and percentage and compared using Chi-square or Fisher's exact test. The sensitivity, specificity, positive predictive value, and negative predictive value along with 95% confidence interval were calculated. Pearson's correlation coefficient (r) was calculated to determine the effect of systolic blood pressure (SBP) and diastolic blood pressure (DBP) on ONSD variations in each group. All statistical analysis was performed using SPSS software version 16 and P value less than 0.05 was considered as significant.


The demographic profile as shown in [Table 1] was comparable between the two groups except parity. Patients in group E were mostly primiparous, while in group C were multiparous. In group C, the indications for ICU admission were postpartum hemorrhage (n = 15), adult respiratory distress syndrome (n = 4), and cardiac disease (n = 3). ONSD of both the eyes was higher in group E as shown in [Table 2]. Blood pressure of patients with eclampsia was much higher in group E on day “0” of admission [Table 3]. In [Table 4], the association of BP with ONSD is shown and SBP was found to be more associated with raised ONSD when compared with DBP, although it was statistically nonsignificant in both the cases. Sensitivity, specificity, positive predictive value, and negative values are shown in [Table 5]. ICU stay of the patients is shown in [Figure 2]. The correlation of ICU stay with ONSD on day “0” was also analyzed which was statistically significant in group E, r = 0.59 (P = 0.002); while in group C, it was nonsignificant r = −0.13 (P = 0.56). The mortality was 6 of 46 (13%); 2 (8.3%) in group E and 4 (18.2%) in group C as depicted in [Figure 3]. The survivors (n = 22) in group E were successfully extubated within 1–3 days after admission. After extubation, 16 patients had decreased ONSD (decrease in 25% of ONSD when compared with day “0” or value less than 0.5 cm), while 6 patients had unchanged ONSD (defined as ONSD more than 0.5 cm or decrease of less than 25% of day “0” value). [Table 6] shows trends in ONSD among surviving patients of both groups till day “2.”{Table 1}{Table 2}{Table 3}{Table 4}{Table 5}{Figure 2}{Figure 3}{Table 6}


Eclampsia is a life-threatening obstetrical emergency occurring in 1 out of 2000 deliveries. It is characterized by onset of convulsion or seizure activity. A majority of the patients are young primigravida. Onset of convulsion usually occurs in third trimester of pregnancy with 80% occurring during intrapartum and within 48 h following delivery. It accounts for the 6% of direct maternal deaths.[5],[7],[8]

There are various theories proposed for neurological effects of eclampsia, and a varied picture of cerebral pathology occurs. As a result, the chances of raised ICP are quite high as shown in brain imaging studies.[5],[9] Monitoring of ICP is very crucial in patients with eclampsia as ICP monitoring has been shown to improve clinical pharmacological treatment of intracranial hypertension in a rising number of situations.[10] The use of routine monitors such as invasive techniques, computed tomography (CT) scan, and magnetic resonance imaging (MRI) brain are limited or not feasible. Among noninvasive tools of ICP monitoring, USG measurement of ONSD has proved its worth in several such clinical scenarios; therefore, we used this technique considering ONSD as a surrogate marker of raised ICP.[3],[11]

In our study, we found ONSD markedly increased in patients with eclampsia when compared with their normal counterparts. All patients were postpartum and admitted on the day or first day after delivery. Dubost et al. conducted a study in patients with pre-eclampsia and found that 20% of them had raised ICP. But since our patients were eclamptic, all of them had raised ICP thus increased ONSD. The median ONSD in pre-eclamptic patients was 0.54 cm as against 0.64 cm (mean) in our study. The control group in both the studies had the same value of 0.45 cm.[6] In a similar study, Singh et al. found that ONSD was the highest in patients with eclampsia (0.58 cm) followed by patients with pre-eclampsia (0.56 cm). While normal pregnant patients had ONSD within normal range (0.47 cm). Moreover, in their study, 44% of patients with pre-eclampsia and 66% of patients with eclampsia had increased ONSD.[12] Ortega et al. too noted increased ONSD in patients with pre-eclampsia/eclampsia when compared with healthy women and pregnant females which was statistically significant but the exact values are not quoted by the authors.[13] In a recent study, Simenc et al. found increased optic disc height in addition to increased ONSD in patients with pre-eclampsia when compared with the control group. In their study, 43% of patients with severe pre-eclampsia had increased ONSD (the cut-off value taken as 5.8 mm). The results in their study were depicted in the form of figures which showed a median value of ONSD in pre-eclampsia group as 0.57 cm, while in control group it was 0.44 cm.[14]

We tried to study correlation between hemodynamic variables and raised ICP. SBP had more positive correlation with increased ICP but not DBP, although it was statistically not evident (P > 0.05). The most likely cause for raised ICP could be hypertension-induced capillary damage causing vasogenic edema. We also found high sensitivity and specificity for this technique as noninvasive monitor of intracranial hypertension similar to earlier findings.[4] We monitored ONSD daily and studied the trends. Twenty-two patients in group E were successfully extubated within 1–3 days of ICU admission. After extubation, though the patients were neurologically sound, ONSD was still raised in 27% of patients whereas it decreased in 73% of patients. Delayed reversibility of optic nerve sheath distension in long-standing intracranial hypertension could be a cause.[15] In brief, neurological symptoms lag behind optic nerve distension at the time of development of intracranial hypertension and reverse happens at the time of resolution of intracranial hypertension. All patients had ONSD in normal range when they were discharged from ICU which correlated to the reversibility of their clinical neurologic symptomatology. The trends in ONSD were earlier studied by Dubost et al. who found raised ONSD till the second day after delivery similar to our study. But on day 7 the values were within normal range.[6] Simenc et al. too followed changes in ONSD till 4 days after delivery and found it still raised and statistically significant when compared with the control group (P < 0.001).[14] The patients who expired had persistent increased ONSD which could be due to sustained neurological complications or development of hepatic encephalopathy following Hemolysis, Elevated liver enzymes and Low platelets count (HELLP) syndrome. ONSD is helpful in prognostication of patients having cerebral pathology. We found that length of ICU stay had positive correlation with ONSD at the time of admission in patients with eclampsia but not in other group. Earlier, it has been used successfully for prognostication of patients with head injury, subarachnoid hemorrhage, posthemicraniectomy, and critically ill patients.[16],[17],[18],[19]

There are few limitations of our study. First, the sample size was small. Second, ONSD measurement was not correlated with other modalities of ICP measurement such as transcranial Doppler, CT scan brain, MRI brain, or invasive technique. Third, all patients in group E were on magnesium sulfate therapy (loading or maintenance) which could have altered ICP and subsequently ONSD. We could not study the effect of magnesium sulfate on ONSD which was beyond the scope of this study. Fourth, being an observational study, methodological issues are there and the quality of study is jeopardized. However, such studies help in strengthening a hypothesis and inspire future interventional studies.


Increased ONSD in patients with eclampsia mirrors the changes in ICP. We opine that USG-measured ONSD should be adopted as a holistic approach for managing these patients. It might help in altering hemodynamics and therapeutic treatment as well as predict the potential for neurological deterioration though further studies are warranted.

Contribution of authors

Dr. Renu Bala: Concept, design, definition of intellectual content, literature search, data acquisition, manuscript preparation, and guarantor.

Dr. Susheela Taxak: Definition of intellectual content, data analysis, manuscript editing, and manuscript review.

Dr. Arnab Banerjee: Definition of intellectual content, data analysis, manuscript editing, and manuscript review.

Dr. Rajesh Kumar: Manuscript preparation, literature search, and data acquisition.

Ethical statement

Informed and written consent was taken at the time of measurement of ONSD. This study is an observational analysis of patients admitted in ICU. The investigation (ultrasonographic measurement of ONSD) is routinely done worldwide and in our hospital, so no ethical aspect is involved in this study.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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