| Intracranial Pressure (ICP) monitoring is a significant tool that aids in the management of neurological disorders like hydrocephalus, head trauma, tumors, colloid cysts, cerebral hematomas 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 in-vivo (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 under sensor area. Therefore, the effect of dural thickness on the sensitivity of pressure sensing mechanism was simulated. The histo-pathological examination of the tissue specimens that were 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. |
