**4. CT scan optic nerve sheath diameter**

Measurement of the optic nerve sheath by tomography is also a valid method. In a study with 41 patients, with a cut-off point of 6.35 mm, obtained a sensitivity of 0.93 (95% СI 0.84–1.00), specificity of 0.80 (95% СI 0.50–1.00), and AUC was 0.87 (95% СI 0.69–1.00). The values are different between several studies. Sekhon et al.

**103**

*Management of Patients with Brain Injury Using Noninvasive Methods*

sensitivity of 83% and specificity of 94% [15, 16, 25–28].

reported that ONSD measured 3 mm posterior to the retina by portable CT predict elevated ICP with a cutoff point of 6.0 mm, the sensitivity of 97% and specificity of 42% [15]. Vaiman et al. describe that ONSD could also predict elevated ICP when measured 10 mm posterior to the retina and with a cutoff point of 5.5 mm, the

Recently Liu et al. described that 4.99 mm was the ideal cutoff point to predict PIC>20 mmHg., with a sensitivity and specificity of 68.75% and 94.74%, respectively. Also, these authors developed a prognostic model with the admission GCS and Rotterdam tomographic scores. They observed that when the measurement of the optic nerve sheath was included, there was a higher discriminative power, sensitivity, and specificity for surgical indication. There are standard indications for surgical intervention described in the various guidelines (hematoma, compression of the cisterns at the base, deviation from the midline, and Glasgow coma scale). Complementary, the width of the sheath of the optic nerve, especially if higher than 5.09 mm (in this Liu et al. model) can be a predictor of

Despite this, we note that this analysis will help a lot in decision making. New studies with a more significant number of patients will be able to assess whether the sheath of the optic nerve will be included in flowcharts for surgical indica-

The ONSD dimensions measured by MRI have been reliable in predicting ICP as reported by recent studies. Geeraerts et al. found that ONSD measured by conventional brain T2-weighted MRI correlates with invasive ICP [33]. They have demonstrated that an enlarged ONSD was a robust predictor of raised ICP with an area under Receiver Operating Statistic (ROC) curve equal to 0.94. An ONSD <5.30 mm was unlikely to be associated with raised ICP, whereas an ONSD above 5.82 mm was

The most significant limitation of its use in the acute phase of trauma is related to the examination duration and the need for care related to the magnetic

Near infrared spectroscopy (NIRS) is an imaging technique used in both clinical and emergency medicine, as well as in research laboratories to quantify and mea-

This is done by monitoring changes of the oxygen saturation of hemoglobin molecules in the body, based on the absorbance of near-infrared light by hemoglobin. The importance of such measures, especially in cerebral physiology, is that the human brain utilizes oxygen to continuously supply neurons with energy used for vital body functioning. In the absence of oxygen, as is the case during ischemic stroke or exsanguination, cognitive and functional impairment resulting in death

Patients with raised ICP have alterations in the NIRS, mainly during the Lundberg B waves. Based on their observations in patients with TBI, spontaneous fluctuations in Hb and HbO2 changed their pattern with an increase in ICP [35–38].

sure the oxygenation status of human tissue non-invasively [34].

*DOI: http://dx.doi.org/10.5772/intechopen.94143*

surgical indication [15, 16, 22–30].

**5. MRI optic nerve sheath diameter**

associated with a 90% probability of raised ICP.

**6. Near-infrared spectroscopy - NIRS**

tion [16, 31, 32].

field [30, 31].

often occurs.

*Management of Patients with Brain Injury Using Noninvasive Methods DOI: http://dx.doi.org/10.5772/intechopen.94143*

*Advancement and New Understanding in Brain Injury*

**3. US optic nerve sheath diameter (ONSD)**

Two measurements are made for optic nerve:

tions that may lead to ICH.

anterior segment, behind the globe.

plane, with the probe in the vertical.

the eyeball to the apex of the orbit.

the presence of raised ICP [9–11].

trauma on ONSD are unclear [3, 18–24].

**4. CT scan optic nerve sheath diameter**

setting [11, 12].

dilations [13–18].

of reduction of ICC, in situations as traumatic brain injury, stroke, intracranial tumors, hydrocephalus, central nervous system infections, reduction in cerebral flow, post cardiorespiratory arrest, liver diseases, kidney diseases and other condi-

The optic nerve can be anatomically subdivided into an intraocular, intraorbital, canalicular, and intracranial segment [8]. The optic nerve, as part of the central nervous system, is covered by a leptomeningeal sheath, which is expandable in the

Optic nerve sheath ultrasound is a simple, safe, inexpensive, bedside diagnostic test analogous to the measurement of BP and has the potential to replace invasive ICP monitoring in cases of raised ICH. Ophthalmic ultrasound typically uses a frequency between 5 and 10.5 MHz to evaluate the eye and orbit [9, 10].

One in the transverse plane, with the probe in horizontal, and one in the sagittal

The final ONSD is the average of these measurements. ONSD is measured 3 mm behind the optical disc [11, 12]. The optic nerve appears as a sagittal hypoechoic structure, 4.5 to 5 mm thick, with 25 mm in length that runs from the outer part of

The optical disc is seen as a hyperechoic line at the posterior pole of the globe. With high interobserver agreement, with a median difference of 0.2–0.3 mm [11]. Ultrasonography of the optic nerve sheath is easy to perform. Despite this, in-depth knowledge of the anatomy of ultrasound and the scanning technique is mandatory for the proper use of the technique in the appropriate clinical

Most authors have suggested that the reasonable upper value of ONSD is 5 mm. However, further studies suggest that the cutoff value of the ONSD that provides the best precision for the prediction of intracranial hypertension (ICP = 20 mmHg) is 5.7–6.0 mm and that the ONSD values above this limit should alert the doctor for

According to Geeraerts et al., a strong relationship was found between the ONSD average and the ICP. When using 5.8 mm values as a cutoff point, a very low

Despite the advantages, ultrasound of the optic nerve sheath has some limitations. In patients with ocular trauma and other diseases of the optic nerve complex, the assessment of ONSD can be challenging. Traumatic optic neuropathy is seen in a significant number of patients with severe head trauma, and the effects of eye

Measurement of the optic nerve sheath by tomography is also a valid method. In a study with 41 patients, with a cut-off point of 6.35 mm, obtained a sensitivity of 0.93 (95% СI 0.84–1.00), specificity of 0.80 (95% СI 0.50–1.00), and AUC was 0.87 (95% СI 0.69–1.00). The values are different between several studies. Sekhon et al.

probability of having a high ICP was observed when the ONSD had smaller

**102**

reported that ONSD measured 3 mm posterior to the retina by portable CT predict elevated ICP with a cutoff point of 6.0 mm, the sensitivity of 97% and specificity of 42% [15]. Vaiman et al. describe that ONSD could also predict elevated ICP when measured 10 mm posterior to the retina and with a cutoff point of 5.5 mm, the sensitivity of 83% and specificity of 94% [15, 16, 25–28].

Recently Liu et al. described that 4.99 mm was the ideal cutoff point to predict PIC>20 mmHg., with a sensitivity and specificity of 68.75% and 94.74%, respectively. Also, these authors developed a prognostic model with the admission GCS and Rotterdam tomographic scores. They observed that when the measurement of the optic nerve sheath was included, there was a higher discriminative power, sensitivity, and specificity for surgical indication. There are standard indications for surgical intervention described in the various guidelines (hematoma, compression of the cisterns at the base, deviation from the midline, and Glasgow coma scale). Complementary, the width of the sheath of the optic nerve, especially if higher than 5.09 mm (in this Liu et al. model) can be a predictor of surgical indication [15, 16, 22–30].

Despite this, we note that this analysis will help a lot in decision making. New studies with a more significant number of patients will be able to assess whether the sheath of the optic nerve will be included in flowcharts for surgical indication [16, 31, 32].

### **5. MRI optic nerve sheath diameter**

The ONSD dimensions measured by MRI have been reliable in predicting ICP as reported by recent studies. Geeraerts et al. found that ONSD measured by conventional brain T2-weighted MRI correlates with invasive ICP [33]. They have demonstrated that an enlarged ONSD was a robust predictor of raised ICP with an area under Receiver Operating Statistic (ROC) curve equal to 0.94. An ONSD <5.30 mm was unlikely to be associated with raised ICP, whereas an ONSD above 5.82 mm was associated with a 90% probability of raised ICP.

The most significant limitation of its use in the acute phase of trauma is related to the examination duration and the need for care related to the magnetic field [30, 31].

## **6. Near-infrared spectroscopy - NIRS**

Near infrared spectroscopy (NIRS) is an imaging technique used in both clinical and emergency medicine, as well as in research laboratories to quantify and measure the oxygenation status of human tissue non-invasively [34].

This is done by monitoring changes of the oxygen saturation of hemoglobin molecules in the body, based on the absorbance of near-infrared light by hemoglobin. The importance of such measures, especially in cerebral physiology, is that the human brain utilizes oxygen to continuously supply neurons with energy used for vital body functioning. In the absence of oxygen, as is the case during ischemic stroke or exsanguination, cognitive and functional impairment resulting in death often occurs.

Patients with raised ICP have alterations in the NIRS, mainly during the Lundberg B waves. Based on their observations in patients with TBI, spontaneous fluctuations in Hb and HbO2 changed their pattern with an increase in ICP [35–38]. The basis of NIRS relies upon two principles:


The propagation of light in tissue depends on the combination of absorption, scattering, and reflection properties of photons. Absorption and scatter in tissue is dependent on the wavelength. Scatter decreases with increasing wavelengths; thereby favoring the transmission of near-infrared light compared to visible light.

NIRS, like most technology, has various limitations. The most important of those limitations are as follows: interference from non-targeted chromophores; indefinite differential path-length; unknown scattering loss factor; and complicated signal interpretation.

Considering the pending technical challenges, the limited number of patients studied, and the conflicting results and opinions on this subject, we believe that this non-invasive method of predicting ICP should be restricted to research centers.

Cerebral injury due to hypoxic/ischemic and hyperperfusion are common issues associated with clinical and surgical practice. Monitoring of cerebral oxygenation during surgery, e.g.; cardiac and cerebral endarterectomy, has been shown to improve patient outcomes and reduce the risk of negative surgical outcomes. In addition to surgical monitoring, NIRS technology provides useful insight into cerebral hemodynamics when used in combination with other cerebral monitoring systems. NIRS monitoring and comparisons have been made with transcranial Doppler (TCD) and electroencephalography (EEG) in its ability to accurately predict cerebral ischemia and hyperperfusion. In addition to perioperative monitoring in clinical settings, many researchers utilize the various NIRS systems to reflect on the cerebral tissue oxygenation status during environmental and exercise interventions despite strong evidence and proper analytical techniques [36, 39].
