Two-depth Transcranial Doppler Research Articles

The Relationship between Intracranial Pressure and Visual Field Zones in Normal-Tension Glaucoma Patients.

Growing evidence suggests that intracranial pressure (ICP) plays an important role in the pathophysiology of glaucoma, especially in normal-tension glaucoma (NTG) patients. Controversial results exist about ICP’s relationship to visual field (VF) changes. With the aim to assess the relationship between ICP and VF zones in NTG patients, 80 NTG patients (age 59.5 (11.6) years) with early-stage glaucoma were included in this prospective study. Intraocular pressure (IOP) (Goldmann), visual perimetry (Humphrey) and non-invasive ICP (via a two-depth Transcranial Doppler, Vittamed UAB, Lithuania) were evaluated. Translaminar pressure difference (TPD) was calculated according to the formula TPD = IOP − ICP. The VFs of each patient were divided into five zones: nasal, temporal, peripheral, central, and paracentral. The average pattern deviation (PD) scores were calculated in each zone. The level of significance p < 0.05 was considered significant. NTG patients had a mean ICP of 8.5 (2.4) mmHg. Higher TPD was related with lower mean deviation (MD) (p = 0.01) and higher pattern standard deviation (PSD) (p = 0.01). ICP was significantly associated with the lowest averaged PD scores in the nasal VF zone (p < 0.001). There were no significant correlations between ICP and other VF zones with the most negative mean PD value. (p > 0.05). Further studies are needed to analyze the involvement of ICP in NTG management.

Human ophthalmic artery as a sensor for non-invasive intracranial pressure monitoring: numerical modeling and in vivo pilot study

Intracranial pressure (ICP) monitoring is important in managing neurosurgical, neurological, and ophthalmological patients with open-angle glaucoma. Non-invasive two-depth transcranial Doppler (TCD) technique is used in a novel method for ICP snapshot measurement that has been previously investigated prospectively, and the results showed clinically acceptable accuracy and precision. The aim of this study was to investigate possibility of using the ophthalmic artery (OA) as a pressure sensor for continuous ICP monitoring. First, numerical modeling was done to investigate the possibility, and then a pilot clinical study was conducted to compare two-depth TCD-based non-invasive ICP monitoring data with readings from an invasive Codman ICP microsensor from patients with severe traumatic brain injury. The numerical modeling showed that the systematic error of non-invasive ICP monitoring was < 1.0 mmHg after eliminating the intraorbital and blood pressure gradient. In a clinical study, a total of 1928 paired data points were collected, and the extreme data points of measured differences between invasive and non-invasive ICP were − 3.94 and 4.68 mmHg (95% CI − 2.55 to 2.72). The total mean and SD were 0.086 ± 1.34 mmHg, and the correlation coefficient was 0.94. The results show that the OA can be used as a linear natural pressure sensor and that it could potentially be possible to monitor the ICP for up to 1 h without recalibration.

Prospective Clinical Study of Non-Invasive Intracranial Pressure Measurements in Open-Angle Glaucoma Patients and Healthy Subjects.

Background and Objective: Glaucoma is a progressive optic neuropathy in which the optic nerve is damaged. The optic nerve is exposed not only to intraocular pressure (IOP) in the eye, but also to intracranial pressure (ICP), as it is surrounded by cerebrospinal fluid in the subarachnoid space. Here, we analyse ICP differences between patients with glaucoma and healthy subjects (HSs). Materials and Methods: Ninety-five patients with normal-tension glaucoma (NTG), 60 patients with high-tension glaucoma (HTG), and 62 HSs were included in the prospective clinical study, and ICP was measured non-invasively by two-depth transcranial Doppler (TCD). Results: The mean ICP of NTG patients (9.42 ± 2.83 mmHg) was significantly lower than that of HSs (10.73 ± 2.16 mmHg) (p = 0.007). The mean ICP of HTG patients (8.11 ± 2.68 mmHg) was significantly lower than that of NTG patients (9.42 ± 2.83 mmHg) (p = 0.008) and significantly lower than that of HSs (10.73 ± 2.16 mmHg) (p < 0.001). Conclusions: An abnormal ICP value could be one of the many influential factors in the optic nerve degeneration of NTG patients and should be considered as such instead of just being regarded as a “low ICP”.

Changing the paradigm of intracranial hypertension in brain tumor patients: a study based on non-invasive ICP measurements

BackgroundThe ultrasound based non-invasive ICP measurement method has been recently validated. Correlation of symptoms and signs of intracranial hypertension with actual ICP measurements in patients with large intracranial tumors is controversial. The purpose of this study was to assess ICP in patients with brain tumors, presenting with neurological signs and symptoms of elevated ICP and to further evaluate the value and utility of non-invasive ICP monitoring.MethodsTwenty patients underwent non-invasive ICP measurement using a two-depth transcranial Doppler ultrasound designed to simultaneously compare pulse dynamics in the proximal (intracranial), and the distal (extracranial) intraorbital segments of the ophthalmic artery through the closed eyelid.ResultsForty-eight measurements were analyzed. Radiological characteristics included tumor volume (range = 5.45–220.27cm3, mean = 48.81 cm3), perilesional edema (range = 0–238.27cm3, mean = 74.40 cm3), and midline shift (mean = 3.99 mm). All ICP measurements were in the normal range of 7–16 mmHg (ICPmean: 9.19 mmHg). The correlation of demographics, clinical and radiological variables in a bivariate association, showed a statistically significant correlation with neurological deficits and ICPmax (p = 0.02) as well as ICPmean (p = 0.01). The correlation between ICP and neurological deficits, showed a negative value of the estimate. The ICP was not increased in all cases, whether ipsilateral nor contralateral to the tumor. The multivariate model analysis demonstrated that neurological deficits were associated with lower ICPmax values, whereas maximum tumor diameter was associated with larger ICPmax values.ConclusionsThis study demonstrated that ICP in patients with intracranial tumors and mass effect is not necessarily increased. Therefore, clinical signs of intracranial hypertension do not necessarily reflect increased ICP.

Noninvasive Monitoring and Neurointerventional Management of Idiopathic Intracranial Hypertension

AbstractIdiopathic intracranial hypertension (IIH) is characterized by isolated rise in intracranial pressure (ICP) leading to chronic, debilitating headaches, tinnitus, and vision loss. Conventional diagnostics and monitoring primarily require the use of invasive procedure like lumbar puncture to measure ICP, while traditional management strategies involve weight reduction and medical treatment with acetazolamide. In an effort to reduce the need for invasive procedures, noninvasive methods of ICP monitoring such as optic nerve sheath diameter measurements and two-depth transcranial Doppler ultrasonography have been developed. In cases of refractory and fulminant IIH, surgical management strategies such as optic nerve sheath fenestration (ONSF), ventriculoperitoneal (VP) and lumboperitoneal (LP) shunting, and transverse venous sinus stenting are used to relieve symptoms via ICP reduction. While ONSF and VP/LP shunting exhibit utility primarily for the treatment of vision loss and headache, respectively, venous sinus stenting may prove to be an effective option in the management of all symptoms of IIH. Most importantly, consideration of the patient’s individual symptoms and values should be taken into account when choosing the optimal surgical management strategy for patients with IIH.

Intracranial, intraocular and ocular perfusion pressures: differences between morning and afternoon measurements

Purpose: To assess how intracranial pressure (ICP), intraocular pressure (IOP) and ocular perfusion pressure (OPP) differ between the morning and the afternoon in healthy subjects.Design: Prospective pilot study.Methods: Ten healthy subjects age 26.5 (1.2) years were included in the prospective pilot study. For each participant, blood pressure, heart rate, IOP, ICP and calculated OPP, translaminar pressure difference (TPD) were assessed two times per day, in the morning (9 ± 1 a.m.) and afternoon (2 ± 1 p.m.) by the same experienced operator. Best-corrected visual acuity and body mass index were also evaluated. TPD was calculated as IOP minus ICP. ICP was measured using a non-invasive two-depth transcranial Doppler device. P &lt; 0.05 was considered significant.Results: Mean ICP was higher during afternoon (10.09 (1.8) mmHg) compared to morning ICP (9.80 (2.2) mmHg), but the difference was not statistically significant (p = 0.14). By analyzing ICP according to different refractive errors categories, we found that emmetropic patients had higher ICP (morning 11.94 (3.0), afternoon 11.5 (2.6) mmHg), compared to myopic (accordingly, 9.14 (1.2) and 9.72 (1.3) mmHg) or hypermetropic (accordingly, 8.85 (0.7) and 9.17 (0.8) mmHg) patients, but the difference was not statistically significant (p &gt; 0.05). We also found that higher OPP in the morning was correlated to lower TPD (r = -0.65; p = 0.04).Conclusion: We found no significant variations in ICP, IOP or OPP during morning and afternoon in young healthy subjects. Higher OPP was related to lower TPD in the morning. Further prospective studies are warranted to investigate diurnal ICP variations in glaucoma patients to understand if fluctuations in ICP and TPD may contribute to the disease process.

Neuroretinal rim area and ocular haemodynamic parameters in patients with normal-tension glaucoma with differing intracranial pressures

PurposeTo assess the differences in the neuroretinal rim area (NRA) and ocular haemodynamic parameters in patients with normal-tension glaucoma (NTG) with differing intracranial pressure (ICP) values.Methods40 patients (11 males) with...

Validation of Noninvasive Absolute Intracranial Pressure Measurements in Traumatic Brain Injury and Intracranial Hemorrhage: Preliminary Results

Aim: Increased intracranial pressure (ICP) is considered to be the most important mechanism of secondary brain injury in patients with acute traumatic brain injury (TBI), and intracranial hemorrhage (ICH) including subarachnoid hemorrhage (SAH). Currently, ICP can be measured and registered only using invasive techniques in routine clinical practice. Routine ICP monitoring in terms of intraventricular and intraparenchymal measurements are invasive, require a surgical procedure, and are associated with complications such as infection and intracranial bleedings. The aim of this ongoing study is the validation of noninvasive absolute ICP measurements with standard methods of invasive measurements obtained with intraventricular or intraparenchymal probes. Additionally, the accuracy and precision of noninvasive absolute ICP will be evaluated. Preliminary results are presented. Methods: The noninvasive ICP measurement device used in this study has been developed in the Telematic Science Laboratory at the Kaunas University of Technology, Lithuania. Noninvasive technique for measurement of ICP is based on simultaneously measuring of an ophthalmic artery (OA) blood flow parameters in the intracranial (IOA) and extracranial (EOA) segments of the OA with two-depth transcranial Doppler (TCD) measurements including mechanical head frame for fixation of ultrasonic transducer on the closed eye lid. No individual patient-specific calibration is required. Approval of Swissmedic and our EC was obtained in December 2013. Results: A total of 43 repeatable simultaneous paired noninvasive and invasive ICP measurements in 10 patients admitted with TBI, SAH, or ICH in our ICU. Preliminary results showed an accuracy (systematic error) of noninvasive absolute ICP measurement of 0.64 mm Hg, and a precision (standard deviation of the random error) SD = 1.76 mm Hg. The mean systematic error (0.64 mm Hg) from 43 data points showed a statistically significant evidence. To reach significant evidence > 95%, more paired data points are needed. During our 15 months study period no adverse event was observed. Conclusion: Preliminary results of this study showed that noninvasive transcranial Doppler absolute ICP measurement correlates with standard invasive ICP measurement. This method seems to be safe and reliable. The introduction of this technique is might be promising for the preoperative evaluation of patients presenting with severe stroke and brain tumors.

Update in intracranial pressure evaluation methods and translaminar pressure gradient role in glaucoma.

Glaucoma is one of the leading causes of blindness worldwide. Historically, it has been considered an ocular disease primary caused by pathological intraocular pressure (IOP). Recently, researchers have emphasized intracranial pressure (ICP), as translaminar counter pressure against IOP may play a role in glaucoma development and progression. It remains controversial what is the best way to measure ICP in glaucoma. Currently, the 'gold standard' for ICP measurement is invasive measurement of the pressure in the cerebrospinal fluid via lumbar puncture or via implantation of the pressure sensor into the brains ventricle. However, the direct measurements of ICP are not without risk due to its invasiveness and potential risk of intracranial haemorrhage and infection. Therefore, invasive ICP measurements are prohibitive due to safety needs, especially in glaucoma patients. Several approaches have been proposed to estimate ICP non-invasively, including transcranial Doppler ultrasonography, tympanic membrane displacement, ophthalmodynamometry, measurement of optic nerve sheath diameter and two-depth transcranial Doppler technology. Special emphasis is put on the two-depth transcranial Doppler technology, which uses an ophthalmic artery as a natural ICP sensor. It is the only method which accurately and precisely measures absolute ICP values and may provide valuable information in glaucoma.

The difference in translaminar pressure gradient and neuroretinal rim area in glaucoma and healthy subjects.

Purpose. To assess differences in translaminar pressure gradient (TPG) and neuroretinal rim area (NRA) in patients with normal tension glaucoma (NTG), high tension glaucoma (HTG), and healthy controls. Methods. 27 patients with NTG, HTG, and healthy controls were included in the prospective pilot study (each group consisted of 9 patients). Intraocular pressure (IOP), intracranial pressure (ICP), and confocal laser scanning tomography were assessed. TPG was calculated as the difference of IOP minus ICP. ICP was measured using noninvasive two-depth transcranial Doppler device. The level of significance P < 0.05 was considered significant. Results. NTG patients had significantly lower IOP (13.7(1.6) mmHg), NRA (0.97(0.36) mm2), comparing with HTG and healthy subjects, P < 0.05. ICP was lower in NTG (7.4(2.7) mmHg), compared with HTG (8.9(1.9) mmHg) and healthy subjects (10.5(3.0) mmHg); however, the difference between groups was not statistically significant (P > 0.05). The difference between TPG for healthy (5.4(7.7) mmHg) and glaucomatous eyes (NTG 6.3(3.1) mmHg, HTG 15.7(7.7) mmHg) was statistically significant (P < 0.001). Higher TPG was correlated with decreased NRA (r = −0.83; P = 0.01) in the NTG group. Conclusion. Translaminar pressure gradient was higher in glaucoma patients. Reduction of NRA was related to higher TPG in NTG patients. Further prospective studies are warranted to investigate the involvement of TPG in glaucoma management.