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Diagnostic value of the optic nerve sheath in the diagnosis of increased intracranial pressure in traumatic brain patients
Maryam Ziaei1, Soudabeh Moodi1, Seyed Mehdi Pourafzali2, Ali Abdolrazaghnejad3
1 Department of Emergency Medicine, Khatam-Al-Anbia Hospital, Zahedan University of Medical Sciences, Zahedan, Iran
2 Department of Emergency Medicine, School of Medicine, Shahrekord University of Medical Sciences, Shahrekord, Iran
3 Department of Emergency Medicine, Khatam-Al-Anbia Hospital, Zahedan University of Medical Sciences; Infectious Diseases and Tropical Medicine Research Center, Research Institute of Cellular and Molecular Sciences in Infectious Diseases, Zahedan University of Medical Sciences, Zahedan, Iran
| Date of Submission | 28-Jul-2022 |
| Date of Acceptance | 13-Sep-2022 |
| Date of Web Publication | 19-May-2023 |
Correspondence Address:
Assoc. Prof. Ali Abdolrazaghnejad
Department of Emergency Medicine, Khatam-Al-Anbia Hospital, Zahedan University of Medical Sciences; Infectious Diseases and Tropical Medicine Research Center, Research Institute of Cellular and Molecular Sciences in Infectious Diseases, Zahedan University of Medical Sciences, Zahedan
Iran
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/abr.abr_248_22
Background: Increased intracranial pressure (ICP) is a modifiable secondary injury that is associated with poor outcomes in patients with traumatic brain injuries (TBIs). Therefore, the present study was conducted with the aim of determining the ICP of TBI patients by measuring the thickness of the optic nerve sheath diameter (ONSD).
Materials and Methods: The present cross-sectional study was conducted on 220 patients with severe TBI that referred to Khatam-al-Anbya Hospital in Zahedan in 2021. The measurement of ONSD was performed by ultrasonography.
Results: The results of this study revealed that 22.7% of TBI patients had high ICP. The mean of right and left ONSD in patients with normal ICP was 3.85 ± 0.83 and 3.85 ± 0.82 mm, respectively, and was significantly lower than that of patients with abnormal ICP (high ICP) with the mean of 3.85 ± 0.82 and 6.12 ± 0.84 mm, respectively (P value <.001). In addition, the right ONSD with the cutoff point of 5.13 mm, the sensitivity of 84%, and the specificity of 95.29% and the left ONSD with the cutoff point of 5.24 mm, the sensitivity of 90%, and the specificity of 95.88% had a significant diagnostic value in the diagnosis of high ICP (P value <.05).
Conclusion: The findings of the present study indicated that the measurement of ONSD is a cost-effective and minimally invasive procedure with a higher accuracy in diagnosing high ICP in TBI patients.
Keywords: Brain trauma, intracranial pressure, optic nerve
How to cite this article:
Ziaei M, Moodi S, Pourafzali SM, Abdolrazaghnejad A. Diagnostic value of the optic nerve sheath in the diagnosis of increased intracranial pressure in traumatic brain patients. Adv Biomed Res 2023;12:128 |
How to cite this URL:
Ziaei M, Moodi S, Pourafzali SM, Abdolrazaghnejad A. Diagnostic value of the optic nerve sheath in the diagnosis of increased intracranial pressure in traumatic brain patients. Adv Biomed Res [serial online] 2023 [cited 2023 Jun 7];12:128. Available from: https://www.advbiores.net/text.asp?2023/12/1/128/377218 |
| Introduction | |  |
Traumatic brain injuries (TBIs) are the main causes of mortality, disability, and social and economic losses in numerous countries.[1] Considering the increasing prevalence of TBI and its various complications, especially the severe physical and mental complications, the high financial costs and the high prevalence of mortality, the rapid, accurate, and appropriate control of patients' brain function are very indispensable.[2] Any change and increase in the components of the content of the skull causes a change in the volume of the other components inside the skull and consequently leads to the increased intracranial pressure (ICP) due to the limitation of the space inside the skull.[3],[4] As a result of ICP, cerebral blood pressure declines and causes decreased cerebral oxygen and secondary cerebral ischemia.[5] Therefore, the ICP assessment is very important for managing TBI because it can be potentially fatal in case of providing no intervention.[6],[7],[8] The gold standard for diagnosing ICP is utilization of a very invasive external ventricular drain device, which is not available in the initial evaluation and may be contraindicated in patients with coagulopathy. Hence, considering the problems in the standard ICP monitoring approaches, such as being difficult, the increased risk of bleeding and infection, the need to transfer patients to the operating room for placing the intraventricular catheter, and as a result the need for the simultaneous presence of a special team for ventricular catheterization, nowadays the application of noninvasive alternatives that do not have the mentioned difficulties has received due attention.[9]
In this regard, the measurement of optic nerve sheath diameter (ONSD) has been proposed as a noninvasive approach for diagnosing ICP.[10],[11],[12] Considering that the central nerves of the optic nerve are surrounded by subarachnoid membrane and cerebrospinal fluid, ICP increases ONSD by affecting the optic nerve.[13] The advantage of this approach is its undemanding nature, which is convenient for the patient and does not require transferring the patient to other equipped departments.
Although various studies have been conducted in this regard and have shown the significant direct relationship between ONSD and patients' ICP level,[14],[15] few studies have been performed in the Iranian population with a focus on evaluating experts' skill in using ultrasound to measure ONSD. Therefore, the diagnostic value of ONSD in the diagnosis of ICP in TBI patients was investigated in this study.
| Materials and Methods | | |
This was a cross-sectional and diagnostic study. The population of the study included all patients with severe TBI that referred to emergency department (ED) of Khatam-al-Anbya Hospital in Zahedan in 2021.
At the confidence level of 95%, 80% power of the test, and considering the diagnostic sensitivity of ONSD in identifying ICP comparison with the Rotterdam computed tomography (CT) criteria in previous studies equal to 82% and the matching ratio is equal to 0.90[16] and the error level is 0.15; 220 people were determined as samples size.
Inclusion criteria were patients aged more than 18 years with severe TBI (Glasgow Comma Scale [GCS] ≤8), no eye injuries, and the consent provided by the patient or their companions to participate in the study.
The exclusion criteria consisted having a history of diseases related to eye surgeries and eye-related diseases, a history of diabetes, eye-related masses, severe and direct trauma to the eyes, a history of brain and nerve surgery, and a history of diseases related to the spinal cord.
A simple random sampling was performed among the TBI patients. First, all adult patients who suffered head trauma for any reason and referred to the ED were classified based on the Glasgow score and then patients with severe TBI (GCS ≤8) requiring sedation, mechanical ventilation, and ICP monitoring were selected.
The ICP monitoring device Codman Micro-Sensor transducer (Johnson & Johnson Inc.), one of the microtransducers used for ICP monitoring, was positioned at the decompressed side in selected cases based on the advice from attending neurosurgeons. After the operation, a Codman ICP Express cranial monitor (Johnson & Johnson Inc.) was used to monitor ICP. The ICP value measured by this method was used as a standard reference. ICP is normally 7–15 mm Hg; at 20–25 mm Hg, the upper limit of normal, treatment to reduce ICP may be needed.
In the next step, a brain CT scan was performed based on the treatment protocol. Then, the measurement of ONSD was performed using an ultrasound device by a trained and experienced expert who was not aware of the results of the brain CT scan. Before performing the optic nerve ultrasonography, the essential information was given to the patients' family and ethical consent was obtained from the patients' companion. The measurement of ONSD using an ultrasound device required the patient to be first placed in the supine position in a horizontal situation up to 20 degrees, and all patients were sedated with intravenous midazolam at the dose of 0.5 to 1 mg before performing the ultrasound. To prevent pressure on the eye, a thick layer of gel was applied on the closed upper eyelid. Then, the 5.6-7.5 Hz linear probe was placed on the temporal surface of the eyes and on the gel and sonography was performed.
The collected data were entered into SPSS software (version 25). The data were presented as means ± standard deviation (SD) or n (%). An independent samples t-test and Chi-squared test were run at the level of inferential statistics. In addition, receiver operating characteristic analysis was used to evaluate the diagnostic value. The significance level of less than 0.05 was considered in all analyses.
Ethical issues
Ethical issues (including plagiarism, data fabrication, and double publication) have been completely observed by the authors. The research conducted in accordance with the tents of the Declaration of Helsinki. The Ethics Committee of Zahedan University of Medical Sciences approved this study. The institutional ethical committee at Zahedan University of Medical Sciences accepted all study protocols (IR.ZAUMS.REC.1397.159).
| Results | | |
In this study, of 220 TBI patients with the mean age of 28.89 ± 8.89 years (18-66 years) and the mean GCS of 6.1 ± 1.51,[3],[4],[5],[6],[7],[8] 172 (78.2%) and 48 (21.8%) patients were male and female, respectively. In addition, 22.7% of these patients had high ICP. Furthermore, the mean of right and left ONSD in patients with normal ICP was 3.85 ± 0.83 and 3.85 ± 0.82 mm, respectively, and was significantly lower than that of the patients with abnormal ICP (high ICP) with the mean of 3.85 ± 0.82 and 6.12 ± 0.84 mm, respectively (P value <.001) [Table 1]. | Table 1: Patients' baseline and clinical characteristics based on their ICP
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The evaluation of the receiver operating characteristic analysis revealed that the right ONSD had the cutoff point of 5.13 mm, the sensitivity of 84%, and the specificity of 95.29% and the left ONSD had the cutoff point of 5.24 mm, the sensitivity of 90%, and the specificity of 95.88%. In addition, the mean of two eyes at the cutoff point was 5.22 with sensitivity and specificity of 86.00 and 97.06, respectively. The ONSD of both eyes and mean of them had a significant diagnostic value in the diagnosis of high ICP (P value <.05) [Table 2] and [Figure 1]. | Figure 1: The ROC curve for comparing the diagnostic value of ONSD in diagnosing high ICP in TBI patients
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 | Table 2: Diagnostic value of the right and left ONSD values in the prognosis of ICP in TBI patients
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| Discussion | | |
The results of the present study showed that 22.7% of TBI patients had high ICP. Moreover, the mean of right and left ONSD in patients with high ICP was significantly higher than that of the patients with normal ICP in this study. In addition, the diagnostic value of ONSD in the right and left eyes with the cutoff points of >5.13 mm and >5.24 mm, the sensitivity of 84% and 90%, and the specificity of 95.29% and 95.88%, respectively, was significant for diagnosing high ICP. In fact, it can be stated that the measurement of ONSD can be an acceptable approach in diagnosing abnormal ICP.
Various studies have been conducted regarding the diagnostic value of ONSD in the diagnosis of ICP and the outcome of various types of patients. For instance, the study of Dehnadi Moghadam et al.[14] showed that ONSD >7.25 mm had the sensitivity of 100% and the specificity of 95% in diagnosing ICP >15 mmHg.
The optic nerve, as part of the central nervous system, is wrapped by the dural sheath. The optical nerve sheath is the continuation of the subarachnoid space at the optic nerve and its tissues are connected with the subarachnoid space. Thus, an increase in ICP results in a corresponding elevation of the ONSD.[15]
As per the results of some other studies, the mean of ONSD in patients without and with radiological signs of high ICP was about 4.4 mm and 6.3 mm, respectively, and its specificity and negative predictive value were 90% and 100%, respectively.[16],[17]
Turkin et al.'s[18] study calculated the ONSD cutoff point of 6.35 mm, the sensitivity of 93%, and the specificity of 80% for TBI patients with high ICP. Besides, they reported a significant relationship between ONSD values and ICP increase.
The findings of the mentioned studies were in line with those of the present study and were indicative of the high diagnostic accuracy of ONSD measurement (right and left) in diagnosing high ICP. However, the cutoff point obtained in the aforementioned study was slightly higher than that of the present study.
In addition, Young et al.[19] conducted a study in the pediatric population with the aim of evaluating the relationship between ONSD and ICP in TBI patients. They reported the relationship between ONSD and ICP as 0.712, which was a direct and significant relationship. In addition, they stated that ICP monitoring should be performed in TBI children, whose mean ONSD is more than 6.1 mm.
The results of another study on a child with cerebral malaria also indicated that the measurement of ONSD by sonography can be used as a reliable approach for diagnosing and predicting the increase of ICP in these patients.[20] Although the examined patients were different from those of the present study, the findings of the aforementioned study regarding the relationship between ONSD and high ICP were similar to those of this study. Moreover, it seems that this measurement can be considered as a suitable and reliable diagnostic criterion for diagnosing high ICP in both adults and children.
It is necessary to mention that the non-evaluation of other criteria such as rotterdam computed tomography score (RCTS), glasgow outcome scale (GOS), and patient outcome can be regarded as the limitations of the present study. However, in cases where the assessment of ICP by invasive approaches is problematic or not feasible, it is worth mentioning that due to the existence of a direct relationship between ONSD and ICP, the measurement of ONSD by ultrasound can be performed at the patients' bedside to identify the patient deterioration as quickly as possible and take required actions to prevent patients' death. Therefore, this point can be considered as the strength of the present study. Nevertheless, it is suggested to conduct future studies with a larger sample size and in other types of diseases to comment more decisively about the diagnostic value of ONSD in the prognosis of the patients' condition and outcome.
| Conclusion | | |
The results of the present study revealed that the measurement of ONSD in TBI patients is a minimally invasive and cost-effective approach with high accuracy in diagnosing ICP. Therefore, this measurement can be employed in EDs for patients suspected of high ICP so that the speed of diagnosis and the accuracy of examination can be increased and most individuals with head trauma can be screened.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1]
[Table 1], [Table 2]
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