|Year : 2019 | Volume
| Issue : 2 | Page : 200-205
Assessment of brain midline shift using sonography in neurocritical patients
Tamer A Helmy, Mohamed A Abdelhady, Hashem A Ahmed
Department of Critical Care Medicine, Faculty of Medicine, University of Alexandria, Alexandria, Egypt
|Date of Submission||04-Jun-2018|
|Date of Acceptance||05-Feb-2019|
|Date of Web Publication||12-Jun-2019|
Tamer A Helmy
Professor in Department of Critical Care Medicine, Alexandria university, Alexandria
Source of Support: None, Conflict of Interest: None
Introduction Brain midline shift (MLS) is a life-threatening condition that requires urgent diagnosis and treatment.
Aim of the work The aim of this study was to assess the brain MLS using transcranial sonography (TCS) and compare it with that of plain computed tomography (CT) in neurocritical patients.
Patients and methods The study was carried out on 50 neurocritical patients admitted to the Alexandria Main University Hospitals at the Critical Care Medicine Units with a Glasgow coma score of less than 8. The ultrasound (US) MLS was measured through the temporal bone window by measuring the difference between the distance from the skull to the third ventricle on both sides as soon as possible before obtaining the brain CT. CT MLS was determined by measuring either the difference between the distance from the external bone table and the center of the third ventricle bilaterally (method 1) or the distance between the ideal midline and the septum pellucidum (method 2).
Results A total of 50 neurocritical patients were included. The MLS (mean±SD) was 4.18±2.15 mm using US and 5.06±2.47 mm using CT (method 1) and 5.23±2.60 mm using CT (method 2). The Pearson’s correlation coefficient (r) between US MLS and CT MLS was 0.986 with method 1 (P<0.001) and 0.984 with method 2 (P<0.001). The area under the receiver operating characteristic curve for detecting a significant MLS with TCS was 0.990 (95% confidence interval=0.916–1.000%) in (method 1) and, using 4 mm as a cutoff, the sensitivity was 94.7%, the specificity 93.5%, and the positive predictive value was 90% and the negative predictive value was 96.7%. The area under the receiver operating characteristic curve for detecting a significant MLS with TCS was 0.988 (95% confidence interval=0.916–1.000%) (in method 2) and, with a cutoff of 4 mm, the sensitivity was 95% %, the specificity was 96.6%, and the positive predictive value was 95% and the negative predictive value was 96.7%.
Conclusion This study suggests that TCS could detect MLS with reasonable accuracy in neurocritical patients and that could serve as a bedside tool to facilitate early diagnosis and treatment for patients with a significant intracranial mass effect.
Keywords: brain computed tomography, brain midline shift, transcranial sonography
|How to cite this article:|
Helmy TA, Abdelhady MA, Ahmed HA. Assessment of brain midline shift using sonography in neurocritical patients. Res Opin Anesth Intensive Care 2019;6:200-5
|How to cite this URL:|
Helmy TA, Abdelhady MA, Ahmed HA. Assessment of brain midline shift using sonography in neurocritical patients. Res Opin Anesth Intensive Care [serial online] 2019 [cited 2019 Oct 14];6:200-5. Available from: http://www.roaic.eg.net/text.asp?2019/6/2/200/260147
| Introduction|| |
In neurocritical care, one of the most life-threatening conditions that require urgent intervention is brain midline shift (MLS). In addition to the clinical examination, computed tomography (CT) is considered to be the cornerstone technique for management of those patients .
A CT scan classification based on data from the Traumatic Coma Data Bank was proposed by Marshall and colleagues, including an MLS of more than 0.5 cm as one of the main criteria for the severity of traumatic brain injury ,.
Ropper observed that following stroke, alteration of consciousness was directly proportional to the MLS on CT  and Pullicino et al.  found that both MLS and coma were independent predictors of mortality at 15 days following acute stroke.
Early detection of MLS is thus very important because it allows the implementation of an appropriate treatment plan (North American recommendations from 2006 call for a surgical evacuation in the case of an MLS > 0.5 cm in the presence of severe traumatic brain injury, extradural, subdural, or intracerebral hematoma) .
However, even though head CT is considered to be the gold standard technique to diagnose MLS, serial CTs of ICU patients can be associated with significant morbidity and secondary brain injuries related to their transport . Routinely repeated CT scans, even in patients with significant brain injuries, does not contribute to patient care .
Transcranial B-mode sonography (TCS) is a neuroimaging technique that displays the brain parenchyma and the intracranial ventricular system through the intact skull. Seidel and colleagues described in 1996 a simple method to determine the MLS with sonography. This study evaluated the dislocation of the third ventricle from the brain midline by transcranial duplex sonography in 10 healthy volunteers. The mean dislocation was 0.2±0.3 mm. Eighteen stroke patients were investigated within 12 h by both duplex sonography and CT and the dislocation of the third ventricle was measured. Correlation between the two methods was high (r=0.87). This seemed to correlate well with CT findings. In addition, it could be an early outcome predictor by rapidly detecting a significant MLS in acute stroke .
| Aim of the work|| |
The aim of this study was to assess the brain MLS using TCS and compare it with that of plain CT in neurocritical patients.
| Patients and methods|| |
This prospective study was carried out on 50 neurocritical adults of both sexes (according to sample size calculation using G power) who were admitted to the Alexandria Main University Hospitals at the Critical Care Medicine Department. Approval of the medical ethics committee of Alexandria Faculty of Medicine and an informed consent was taken from the patient or the next of kin before conducting the study.
- Neurocritical patients with Glasgow coma score (GCS) of less than 8.
- Patients of age more than 18 years.
- Decompressive craniectomy.
- Patients with temporal subcutaneous hematoma.
- Maxillofacial trauma.
All patients included in the study were subjected to complete history taking, systematic clinical examination, and full neurological assessment. GCS was calculated on admission.
The ultrasound (US) MLS was measured through the temporal acoustic bone window using a low frequency (2–4 MHz) probe using (EMP 2100) an US device prior to plain brain CT. The third ventricle was identified as a double hyperechogenic image over the midbrain; the distance between the external bone table and the center of the third ventricle was measured bilaterally in millimeters and the difference between the two readings divided by two was used to calculate the MLS.
The CT MLS was measured by two methods:
The distance between the external bone table and the center of the third ventricle at the orbitomeatal plane, allowing visualization of the third ventricle (in the same plane as the sonographic measurement) .
The distance between the ideal midline and the septum pellucidum .
CT method (1) was used as a gold standard and 5 mm was considered a significant MLS.
The measurement of MLS using TCS was compared with that of plain CT.
Statistical analysis of the data
Data were fed to the computer and analyzed using IBM SPSS software package, version 20.0 (IBM, USA). Qualitative data were described using number and percent. Quantitative data were described using range (minimum and maximum), mean, SD, and median. Significance of the obtained results was judged at the 5% level.
The used tests were
- Paired t test: for normally quantitative variables, to compare between two periods.
- Pearson’s coefficient: to correlate between two normally quantitative variables.
- Kruskal–Wallis test: for abnormally quantitative variables, to compare between more than two studied groups.
- Spearman’s coefficient: to correlate between two abnormally quantitative variables.
- Receiver operating characteristic (ROC) curve: it is generated by plotting sensitivity (TP) on the y axis versus 1-specificity (FP) on the x axis at different cutoff values. The area under the ROC curve denotes the diagnostic performance of the test. Area more than 50% gives acceptable performance and area about 100% is the best performance for the test. The ROC curve allows also a comparison of performance between two tests.
- Bland and Altman plot: for the agreement between two quantitative values.
| Results|| |
Sixty percent of the studied patients were men. The mean age was 48.90±21.19 years. The mean admission GCS was 7.12±1.66. All the cases were mechanically ventilated. Twenty-one (42%) patients of the studied cases died, the length of ICU stays ranged from 1 to 24 days with a mean of 11.04±6.30. The days on mechanical ventilator ranged from 1 to 24 days, mean±SD 7.36±7.02 ([Table 1]).
|Table 1 Distribution of the studied cases according to Marshall classification (N=50)|
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Computed tomography results
CT MLS was 5.06±2.47 mm (using method 1) and 5.23±2.60 mm (using method 2). An MLS of more than 5 mm with CT was observed in 17 (34%) patients.
Transcranial sonography results
Measurement of MLS by TCS showed an average of 4.18±2.15 mm. An MLS of more than 5 mm was observed in 12 (24%) patients. The correlation coefficient between US MLS and CT MLS was 0.986 with method 1 (P <0.001), and 0.984 with method 2 (P<0.001).
The correlation coefficient between CT MLS (method 1) and CT MLS (method 2) was 0.995 (P<0.001). The limits of agreements for MLS measurements with US and the two CT methods are presented in [Table 2], showing a bias of −0.88 mm and limits of agreement from −1.02 to −0.74 mm for US and CT (method 1) and a bias of −1.05 mm and limits of agreement from −1.23 to −0.88 mm for US and CT (method 2).
|Table 2 Agreement of ultrasound with computed tomography methods 1 and 2|
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The sensitivity and the specificity of US to detect a significant MLS (i.e. MLS >5 mm) were analyzed with the ROC curve. In method (2) the area under the ROC curve was 0.988 (95% confidence interval=0.916–1.000%) and with a cutoff of 4 mm, the sensitivity was 95%, the specificity 96.6%, and the positive predictive value was 95% and the negative predictive value was 96.7%.
When the CT (method 1) was used to define a ‘significant’ MLS (i.e. MLS >5 mm), the area under the ROC curve was 0.990 and with a cutoff of 4 mm, the sensitivity was 94.7%, and the specificity was 93.5%. The positive predictive value was 90% and the negative predictive value was 96.7%.
The bias between both methods (method 1 and method 2) was −0.146 mm, and the correlation coefficient was 0.995 (P<0.001) ([Figure 1]).
|Figure 1 ROC curve forthe detection of a CT MLS (method 1)>5 mm (with TCS.CT computed tomography; MLS; midline shift TCS, transcranial sonography.|
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The correlation coefficient of the difference between US MLS and CT MLS was 0.641 (P<0.001). The smaller the MLS the narrower the difference between the measurement of US MLS and CT MLS.
The narrowest difference between US MLS and CT MLS (0.37±0.12) was observed at an MLS of less than 2 mm.
Twenty-one (42%) patients of the studied cases died; the length of ICU stays ranged from 1 to 24 days with a mean of 11.04±6.30. The days of mechanical ventilator ranged from 1 to 24 days (mean, 7.36±7.02).
There was significant relation between US MLS and mortality; 100% of the cases survived with a US MLS of less than 4 mm. Eighty-three percent died when the US MLS was (4–6 mm;100% of the cases with a US MLS greater than 6 mm died ([Table 3],[Table 4],[Table 5]).
|Table 3 Relation between computed tomography midline shift and (difference between ultrasound midline shift and computed tomography midline shift)|
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|Table 4 Correlation between ultrasound midline shift with Glasgow coma score, ICU stay, and ventilation days|
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|Table 5 Relation between ultrasound midline shift with Glasgow coma score, ICU stay, and ventilation days|
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The relation between US MLS and GCS was statistically significant, the greater the US MLS the lower the GCS. The relation between US MLS and length of ICU stay and ventilation days was tested and it was statistically significant. The greater the US MLS the longer the length of ICU stay and ventilation days, except in patients with an US MLS of greater than 6 mm because of early death.
| Discussion|| |
The early detection of an MLS in neurosurgical patients is very important because it allows the implementation of an appropriate treatment plan. Brain CT is considered to be the gold standard to diagnose MLS. Serial CTs in neurosurgical ICU patients can be associated with significant morbidity and secondary brain injuries related to their transport.
Our study suggested that it is possible to detect MLS with a reasonable accuracy in neurocritical patients with various intracranial pathologies using TCS. This could facilitate early diagnosis and treatment for patients with significant intracranial mass effects. It is a noninvasive tool, decreases exposure to radiation, and hazards of transport.
Bogdahn et al.  described for the first time the identification of cerebral structures with sonography and was able to identify the third ventricle in 45 of 52 patients.
Seidel et al.  subsequently proposed to measure the MLS with US by setting the center of the third ventricle as a reference. This method was used to determine the mass effect of patients presenting with acute ischemic stroke .Gerriets et al.  studied the value of MLS measurement to predict fatal outcome at different time points after stroke onset. It showed that an US MLS of more than 4 mm within the first 32 h was associated with a near 100% mortality, with the exception of a patient having undergone decompressive craniectomy .
Transcranial duplex sonography was used to monitor ventricular width in patients with hydrocephalus. Ninety-two attempts to clamp either lumbar or extraventricular drainage were monitored in 37 patients during a 1-year period. A cutoff value for increase of ventricular width of 5.5 mm yielded high sensitivity (100%) and specificity (83%) .
In 61 patients with supratentorial ischemic infarction, the sonographic measurement of MLS was compared with cranial CT in a 12-h time window. Transcranial color-coded duplex sonography and cranial CT measurements of MLS were correlated, the correlation coefficient was more than 0.9 .
Motuel et al.  tested the accuracy of sonography in detecting MLS in comparison with CT, 52 neurosurgical ICU patients were included. The Pearson’s correlation coefficient (r) between sonography and CT scan was 0.65 (P<0.001). The sensitivity was 84.2% and the specificity was 84.8%.
In our study, the best correlation between TCS and CT was obtained by using the distance between the external bone table and the center of the third ventricle measured from the CT cuts in the orbitomeatal plane that allowed visualizing the third ventricle (method 1), with a bias of only −0.88 mm. The correlation coefficient between TCS and CT was slightly better when using CT method 1 compared with method 2 (0.986 vs. 0.984). The bias was smaller and the limits of agreement were narrower when using CT method 1 (mean bias of −0.88 mm and limits of agreement from −1.02 to −0.74 mm) for TCS and CT method 1 versus a mean bias of −1.05 mm and limits of agreement from −1.23 to −0.88 mm for TCS and CT method 2. This could be due to the fact that CT method 1 uses the same imaging plane as TCS, whereas CT method 2 uses a different plane (which is the neuroradiologists’ conventional way to measure MLS). Using a different imaging plane could, thus, have increased the bias between sonography and CT without affecting the correlation.
In our study, we found that TCS seemed to systematically underestimate the CT MLS (the MLS was 4.18±2.15 mm with TCS, 5.06±2.47 mm with CT method 1, and 5.23±2.60 mm with CT method 2).
In our study, the ability to detect significant MLS (>5 mm in CT scan) with TCS was good, with a sensitivity and specificity of around 95% when using a threshold for a significant MLS set at 4 mm, although MLS was underestimated by TCS. The smaller the MLS the narrower the difference between the measurement of US MLS and CT MLS.
The relation between US MLS and GCS was statistically significant, the greater the US MLS the lower the GCS. The relation between US MLS and length of ICU stay and ventilation days was tested and it was statistically significant. The greater the US MLS, the longer the length of ICU stay and ventilation days, except in patients with an US MLS of greater than 6 mm because of early death.
| Conclusion|| |
This study suggests that TCS could detect MLS with reasonable accuracy in neurocritical patients and may serve as a reliable bedside tool to facilitate early diagnosis and treatment for patients with a significant intracranial mass effect.
The measurement of MLS using sonography and CT were not simultaneous and as the brain MLS can change rapidly, it is possible that the decrease in agreement between methods could in part be due to the changing MLS at different time points.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]