Embedded wireless intracranial pressure monitoring implant at microwave frequencies

Intracranial Pressure (ICP) monitoring is a significant tool that aids in the management of neurological disorders like hydrocephalus, head trauma, tumors, colloid cysts, cerebralhematomas etc. ICP is the pressure exerted on the rigid, bony skull by its constituents that are brain, cerebrospinal fluid, and the cerebral blood. Increased ICP can lead to brain damage, disability, and death. Various modalities have been developed for the monitoring of ICP in hospitals and in ambulatory conditions. Currently, only catheter based systems have made it to the clinical practice. The catheter based systems can only be used in a hospital setting, and have a limited useful life due to drift and risk of infection.The motivation for this research was the intent to develop a completely implantable, wireless ICP monitoring implant that can provide long-term monitoring of the pressure in ambulatory conditions. The uniqueness of this work is accentuated by the ability of the implant to transmit at 2.4 GHz. These implants have undergone a battery of tests in the in-vitro and invivo (canine) studies during which the feasibility of microwave transmission through scalp was established. Long-term animal studies were conducted to determine the integrity,biocompatibility, and the performance of the implant in a biological environment. Animal studies for long durations with epidural implants showed a thickening of the dura mater undersensor area. Therefore, the effect of dural thickness on the sensitivity of pressure sensing mechanism was simulated. The histo-pathological examination of the tissue specimens thatwere excised at the termination of an animal study showed the presence of lymphocytes, and fibrous tissue which is a normal immunological reaction to a foreign body. These tests did not reveal any toxicity due to the presence of the implant. In the animal studies that were conducted with sub-dural implants, a correlation coefficient of 0.94 and better was determined between the gold standard for ICP monitoring and our implant. In our latest animal study a sub-dural implant has been successfully tested in an animal for a duration of one month, thus proving the reliability of the implant packaging and its performance for a long-duration ICP monitoring application. This study also underscores the applicability of our ICP implant for monitoring of traumatic brain injuries, among other applications.Ph.D., Biomedical Engineering -- Drexel University, 200

Advances in Intracranial Pressure Monitoring and Its Significance in Managing Traumatic Brain Injury

Intracranial pressure (ICP) measurements are essential in evaluation and treatment of neurological disorders such as subarachnoid and intracerebral hemorrhage, ischemic stroke, hydrocephalus, meningitis/encephalitis, and traumatic brain injury (TBI). The techniques of ICP monitoring have evolved from invasive to non-invasive—with both limitations and advantages. Some limitations of the invasive methods include short-term monitoring, risk of infection, restricted mobility of the subject, etc. The invasiveness of a method limits the frequency of ICP evaluation in neurological conditions like hydrocephalus, thus hampering the long-term care of patients with compromised ICP. Thus, there has been substantial interest in developing noninvasive techniques for assessment of ICP. Several approaches were reported, although none seem to provide a complete solution due to inaccuracy. ICP measurements are fundamental for immediate care of TBI patients in the acute stages of severe TBI injury. In severe TBI, elevated ICP is associated with mortality or poor clinical outcome. ICP monitoring in conjunction with other neurological monitoring can aid in understanding the pathophysiology of brain damage. This review article presents: (a) the significance of ICP monitoring; (b) ICP monitoring methods (invasive and non-invasive); and (c) the role of ICP monitoring in the management of brain damage, especially TBI

Protection against Blast-Induced Traumatic Brain Injury by Increase in Brain Volume

Blast-induced traumatic brain injury (bTBI) is a leading cause of injuries in recent military conflicts and it is responsible for an increased number of civilian casualties by terrorist attacks. bTBI includes a variety of neuropathological changes depending on the intensity of blast overpressure (BOP) such as brain edema, neuronal degeneration, diffuse axonal damage, and vascular dysfunction with neurological manifestations of psychological and cognitive abnormalities. Internal jugular vein (IJV) compression is known to reduce intracranial compliance by causing an increase in brain volume and was shown to reduce brain damage during closed impact-induced TBI. We investigated whether IJV compression can attenuate signs of TBI in rats after exposure to BOP. Animals were exposed to three 110 ± 5 kPa BOPs separated by 30 min intervals. Exposure to BOP resulted in a significant decrease of neuronal nuclei (NeuN) together with upregulation of aquaporin-4 (AQP-4), 3-nitrotyrosine (3-NT), and endothelin 1 receptor A (ETRA) expression in frontal cortex and hippocampus one day following exposures. IJV compression attenuated this BOP-induced increase in 3-NT in cortex and ameliorated the upregulation of AQP-4 in hippocampus. These results suggest that elevated intracranial pressure and intracerebral volume have neuroprotective potential in blast-induced TBI

Advances in Intracranial Pressure Monitoring and Its Significance in Managing Traumatic Brain Injury

Intracranial pressure (ICP) measurements are essential in evaluation and treatment of neurological disorders such as subarachnoid and intracerebral hemorrhage, ischemic stroke, hydrocephalus, meningitis/encephalitis, and traumatic brain injury (TBI). The techniques of ICP monitoring have evolved from invasive to non-invasive—with both limitations and advantages. Some limitations of the invasive methods include short-term monitoring, risk of infection, restricted mobility of the subject, etc. The invasiveness of a method limits the frequency of ICP evaluation in neurological conditions like hydrocephalus, thus hampering the long-term care of patients with compromised ICP. Thus, there has been substantial interest in developing noninvasive techniques for assessment of ICP. Several approaches were reported, although none seem to provide a complete solution due to inaccuracy. ICP measurements are fundamental for immediate care of TBI patients in the acute stages of severe TBI injury. In severe TBI, elevated ICP is associated with mortality or poor clinical outcome. ICP monitoring in conjunction with other neurological monitoring can aid in understanding the pathophysiology of brain damage. This review article presents: (a) the significance of ICP monitoring; (b) ICP monitoring methods (invasive and non-invasive); and (c) the role of ICP monitoring in the management of brain damage, especially TBI

Effects of Exposure to Blast Overpressure on Intracranial Pressure and Blood-Brain Barrier Permeability in a Rat Model

<div><p>Exposure to blast overpressure (BOP) activates a cascade of pathological processes including changes in intracranial pressure (ICP) and blood-brain barrier (BBB) permeability resulting in traumatic brain injury (TBI). In this study the effect of single and multiple exposures at two intensities of BOP on changes in ICP and BBB permeability in Sprague-Dawley rats was evaluated. Animals were exposed to a single or three repetitive (separated by 0.5 h) BOPs at 72 kPa or 110 kPa. ICP was monitored continuously via telemetry for 6 days after exposure to BOP. The alteration in the permeability of BBB was determined by extravasation of Evans Blue (EB) into brain parenchyma. A significant increase in ICP was observed in all groups except the single 72 kPa BOP group. At the same time a marked increase in BBB permeability was also seen in various parts of the brain. The extent of ICP increase as well as BBB permeability change was dependent on intensity and frequency of blast.</p></div

Representative images of EB fluorescence in brains of sham-controls and rats exposed to single or repetitive BOP at two different intensities (72 kPa vs 110 kPa).

<p>Sections of brain were analyzed for EB fluorescence in frontal cortex (FCX), hippocampus (HIP), thalamus (THL), and occipital cortex (OCX). The EB fluorescence was increased after exposure to BOP suggesting higher vascular leakage into brain parenchyma.</p

Time course of changes in ICP in response to exposure to BOP.

<p>For each day (marked with vertical dashed lines) a three or four hour segment of data is presented. A) 1x72 kPa; B)3x72 kPa; C) 1x110 kPa; and D) 3x110 kPa. Data are expressed as means ± SE (n = 6 in each group). b—time of blast; * p<0.01—significance of differences in ICP between two adjacent time points, # p<0.01—significance of differences in ICP compared to pre-blast baseline.</p

Quantification of EB fluorescence intensity in sham and blast exposed rats.

<p>Results are shown as relative EB fluorescence units (controls = 1) and are expressed as means ± SE (n = 6). A) Comparison between groups 1x72 kPa and 3x72 kPa; B) 1x110 kPa and 3x110 kPa; C) 1x72 kPa and 1x110 kPa; D) 3x72 kPa and 3x110 kPa. *p<0.05—difference between sham and BOP exposed groups. #p<0.05—difference between BOP exposed groups. FCX: frontal cortex; HIP: hippocampus; THL: thalamus; OCX: occipital cortex.</p