Dr. Douglas McCreery
Huntington Medical Research Institutes

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Dr. Douglas McCreery of the Huntington Medical Research Institutes (HMRI) has led a team of scientists to make a significant advance in the treatment of deafness and other conditions that are due to the impairment of neural function.

Dr. McCreery, who has a bachelor’s degree in electrical engineering and a Ph.D. in biomedical engineering from the University of Connecticut, began his scientific career as a postdoctoral fellow at the University of Minnesota Medical School, where he later became a research associate in the Department of Neurosurgery. He moved to the HMRI in 1979 and has been the director of its Neural Engineering Laboratory since 2001.

Dr. McCreery works with a multidisciplinary group of scientists focused on developing implantable devices to replace or augment impaired function of the nervous system. In collaboration with the House Ear Institute (Los Angeles) and the Cochlear Corporation (Sydney, Australia), Dr. McCreery has been instrumental in the development of a new device, the Penetrating Auditory Brainstem Implant (PABI), which has the potential to restore a degree of hearing to profoundly deaf people for whom hearing aids and cochlear implants are not an option. The PABI devices work by translating sound waves into electrical impulses that can be fed directly to the cochlear nucleus, a hearing center of the brain, using a set of tiny implanted electrodes.

Electrode array used in PABI devices

Devices designed to restore hearing by stimulating neurons are not new. Cochlear implants, which translate sound waves into electrical impulses and transmit them to the auditory nerve, bypass the complex workings of the inner ear; they can therefore restore some hearing to individuals who have damaged or non-functioning inner-ear components.

However, cochlear implants require a functioning auditory nerve. If the nerve has been damaged or severed, the signals transmitted by the implant are unable to reach the area of the brain called the cochlear nucleus, where auditory signals are processed.

While a number of scenarios may result in the degradation or destruction of the auditory nerve, a condition that is frequently associated with loss of auditory nerve function is Neurofibromatosis Type II (NF2). NF2 produces bilateral tumors on the cranial nerve where the auditory nerve is located. The growth and subsequent removal of these tumors usually results in destruction of the auditory nerve.

This gap in the hearing pathway requires a mechanism to circumvent the auditory nerve. The Auditory Brainstem Implant (ABI) device developed in the 1990s stimulates the cochlear nucleus directly, bypassing both the inner ear and the auditory nerve. Similar to cochlear implants, ABI devices consist of an external sound processor and transmitter, as well as an internal receiver and a stimulating unit: the electrode array.

Scanning electron micrograph of an individual microelectrode

ABI devices allow individuals to discern many environmental sounds. However, they do not provide the depth-of-sound discrimination that is required for speech recognition. To address this problem, Dr. McCreery and his colleagues at HMRI have developed a new type of electrode that is inserted into the cochlear nucleus, permitting detection of a wider range of pitches. Their goal is to enable the wearers of the device to distinguish the patterns and pitches of the spoken word.

In addition to creating the electrode array portion of the PABI device, Dr. McCreery’s group has developed a patented insertion tool for the fragile electrode assembly. The PABI device is currently in clinical trials, and there have already been a number of successful implantations.

The HMRI Neural Engineering Laboratory is also working on using microelectrodes for other applications, such as blindness, Parkinson’s disease, epilepsy, spinal cord injury and strokes. The objective is to achieve specific neural stimulation without damaging nerve cells. The laboratory has earned an international reputation for its work on the interface between the electrodes and neural tissues

Dr. McCreery and his colleagues have successfully developed a means by which electrical impulses generated from external sources can be fed directly into targeted neural tissue -- a technology that shows great promise for treating a number of debilitating diseases and conditions. Davis Wright Tremaine LLP congratulates Dr. Douglas McCreery on his successes in the implementation of microelectrodes and PABI devices, and is pleased to feature him as its Life Sciences Inventor of the Month.

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