Rolandas Zakelis

Clinical Assessment of Noninvasive Intracranial Pressure Absolute Value Measurement Method

Objective: To assess prospectively the accuracy and precision of a method for noninvasive intracranial pressure (ICP) measurement compared with invasive gold standard CSF pressure measurement. Methods: Included were 62 neurologic patients (37 idiopathic intracranial hypertension, 20 multiple sclerosis, 1 Guillain-Barré syndrome, 1 polyneuropathy, and 3 hydrocephalus). The average age was 40 ± 12 years. All patients had lumbar puncture indicated as a diagnostic procedure. ICP was measured using a noninvasive ICP measurement method, which is based on a two-depth high-resolution transcranial Doppler insonation of the ophthalmic artery (OA). The OA is being used as a natural pair of scales, in which the intracranial segment of the OA is compressed by ICP and the extracranial segment of the OA is compressed by extracranial pressure (Pe) applied to the orbit. The blood flow parameters in both OA segments are approximately the same in the scales balance case when Pe = ICP. All patients had simultaneous recording of noninvasive ICP values and invasive gold standard CSF pressure values. Results: Analysis of the 72 simultaneous paired recordings of noninvasive ICP and the gold standard CSF pressure showed good accuracy for the noninvasive method as indicated by the low mean systematic error (0.12 mm Hg; confidence level [CL] 0.98). The method also showed high precision as indicated by the low SD of the paired recordings (2.19 mm Hg; CL 0.98). The method does not need calibration. Conclusion: The proposed noninvasive ICP measurement method is precise and accurate compared with gold standard CSF pressure measured via lumbar puncture.

Improved diagnostic value of a TCD-based non-invasive ICP measurement method compared with the sonographic ONSD method for detecting elevated intracranial pressure

Abstract Objectives: To compare the diagnostic reliability of optic nerve sheath diameter (ONSD) ultrasonography with a transcranial Doppler (TCD)-based absolute intracranial pressure (ICP) value measurement method for detection of elevated ICP in neurological patients. The ONSD method has been only tested previously on neurosurgical patients. Methods: A prospective clinical study of a non-invasive ICP estimation method based on ONSD correlation with ICP and an absolute ICP value measurement method based on a two-depth TCD technology has recruited 108 neurological patients. Ninety-two of these patients have been enrolled in the final analysis of the diagnostic reliability of ONSD ultrasonography and 85 patients using the absolute ICP value measurement method. All non-invasive ICP measurements were compared with ‘Gold Standard’ invasive cerebrospinal fluid (CSF) pressure measurements obtained by lumbar puncture. Receiver-operating characteristic (ROC) analysis has been used to investigate the diagnostic value of these two methods. Results: The diagnostic sensitivity, specificity, and the area under the ROC curve (AUC) of the ONSD method for detecting elevated intracranial pressure (ICP >14·7 mmHg) were calculated using a cutoff point of ONSD at 5·0 mm and found to be 37·0%, 58·5%, and 0·57, respectively. The diagnostic sensitivity, specificity, and AUC for the non-invasive absolute ICP measurement method were calculated at the same ICP cutoff point of 14·7 mmHg and were determined to be 68·0%, 84·3%, and 0·87, respectively. Conclusions: The non-invasive ICP measurement method based on two-depth TCD technology has a better diagnostic reliability on neurological patients than the ONSD method when expressed by the sensitivity and specificity for detecting elevated ICP >14·7 mmHg.

Location of the internal carotid artery and ophthalmic artery segments for non-invasive intracranial pressure measurement by multi-depth TCD

ABSTRACT The aim of the present study was to locate the ophthalmic artery by using the edge of the internal carotid artery (ICA) as the reference depth to perform a reliable non-invasive intracranial pressure measurement via a multi-depth transcranial Doppler device and to then determine the positions and angles of an ultrasonic transducer (UT) on the closed eyelid in the case of located segments. High tension glaucoma (HTG) patients and healthy volunteers (HVs) undergoing non-invasive intracranial pressure measurement were selected for this prospective study. The depth of the edge of the ICA was identified, followed by a selection of the depths of the IOA and EOA segments. The positions and angles of the UT on the closed eyelid were measured. The mean depth of the identified ICA edge for HTG patients was 64.3 mm and was 63.0 mm for HVs (p = 0.21). The mean depth of the selected IOA segment for HTG patients was 59.2 mm and 59.3 mm for HVs (p = 0.91). The mean depth of the selected EOA segment for HTG patients was 48.5 mm and 49.8 mm for HVs (p = 0.14). The difference in the located depths of the segments between groups was not statistically significant. The results showed a significant difference in the measured UT angles in the case of the identified edge of the ICA and selected ophthalmic artery segments (p = 0.0002). We demonstrated that locating the IOA and EOA segments can be achieved using the edge of the ICA as a reference point. Abbreviations: OA: ophthalmic artery; IOA: intracranial segments of the ophthalmic artery; EOA: extracranial segments of the ophthalmic artery; ICA: internal carotid artery; UT: ultrasonic transducer; HTG: high tension glaucoma; SD: standard deviation; ICP: intracranial pressure; TCD: transcranial Doppler

Graphical and statistical analyses of the oculocardiac reflex during a non-invasive intracranial pressure measurement

Purpose This study aimed to examine the incidence of the oculocardiac reflex during a non-invasive intracranial pressure measurement when gradual external pressure was applied to the orbital tissues and eye. Methods Patients (n = 101) and healthy volunteers (n = 56) aged 20–75 years who underwent a non-invasive intracranial pressure measurement were included in this retrospective oculocardiac reflex analysis. Prespecified thresholds greater than a 10% or 20% decrease in the heart rate from baseline were used to determine the incidence of the oculocardiac reflex. Results None of the subjects had a greater than 20% decrease in heart rate from baseline. Four subjects had a greater than 10% decrease in heart rate from baseline, representing 0.9% of the total pressure steps. Three of these subjects were healthy volunteers, and one was a glaucoma patient. Conclusion The incidence of the oculocardiac reflex during a non-invasive intracranial pressure measurement procedure was very low and not associated with any clinically relevant effects.

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

BACKGROUND Increased intracranial pressure (ICP) causes secondary damage in traumatic brain injury (TBI), and intracranial hemorrhage (ICH). Current methods of ICP monitoring require surgery and carry risks of complications. OBJECTIVE To validate a new instrument for noninvasive ICP measurement by comparing values obtained from noninvasive measurements to those from commercial implantable devices through this pilot study. METHODS The ophthalmic artery (OA) served as a natural ICP sensor. ICP measurements obtained using noninvasive, self-calibrating device utilizing Doppler ultrasound to evaluate OA flow were compared to standard implantable ICP measurement probes. RESULTS A total of 78 simultaneous, paired, invasive, and noninvasive ICP measurements were obtained in 11 ICU patients over a 17-mo period with the diagnosis of TBI, SAH, or ICH. A total of 24 paired data points were initially excluded because of questions about data independence. Analysis of variance was performed first on the 54 remaining data points and then on the entire set of 78 data points. There was no difference between the 2 groups nor was there any correlation between type of sensor and the patient (F[10, 43] = 1.516, P = .167), or the accuracy and precision of noninvasive ICP measurements (F[1, 43] = 0.511, P = .479). Accuracy was [-1.130; 0.539] mm Hg (CL = 95%). Patient-specific calibration was not needed. Standard deviation (precision) was [1.632; 2.396] mm Hg (CL = 95%). No adverse events were encountered. CONCLUSION This pilot study revealed no significant differences between invasive and noninvasive ICP measurements (P < .05), suggesting that noninvasive ICP measurements obtained by this method are comparable and reliable.

Correlation among decreased regional cerebral oxygen saturation, blood levels of brain injury biomarkers, and cognitive disorder

Objective This study was performed to investigate the correlation among decreased regional cerebral oxygen saturation (rSO2), blood levels of brain injury biomarkers, and postoperative cognitive disorder (POCD) after cardiac surgery with cardiopulmonary bypass (CPB). Methods This prospective observational study included 59 patients undergoing coronary artery bypass graft surgery with CPB. All patients underwent neuropsychological tests (Mini Mental State Evaluation, Rey Auditory Verbal Learning Test, digit span test, digit symbol substitution test, and Schulte table) the day before and 10 days after the surgery. The blood levels of two brain injury biomarkers, neuron-specific enolase (NSE) and glial fibrillary acidic protein (GFAP), were measured before and 1 day after the surgery. Results The rSO2 decreased during surgery in 21 (35%) patients. POCD was detected in 22 (37%) patients. After the surgery, no significant changes in the GFAP blood level occurred in any patients. No significant correlations were found among the decreased rSO2, increased NSE blood level, and rate of POCD. Conclusion These results suggest that a decrease in rSO2 during cardiac surgery is not necessarily related to the development of POCD or an increased blood level of the brain injury biomarker NSE.

Innovative Computerized Non-invasive Intracranial Pressure Measurement Technology and Its Clinical Validation

An innovative non-invasive absolute intracranial pressure (aICP) measurement method has been validated by multicenter comparative clinical studies. The method is based on two-depth transcranial Doppler technology and employs intracranial and extra cranial segments of the ophthalmic artery as a pressure sensor. The ophthalmic artery is used as a natural pair of scales which compares aICP with controlled pressure aPe which is externally applied to the orbit. In the case of scales balance, aICP=aPe. A two-depth transcranial Doppler device is used as a pressure balance indicator. The proposed method is the only non-invasive aICP measurement method which does not need patient-specific calibration.