Neurologists
6 years of experience

Accepting new patients
Central Ann Arbor
University of Michigan Medical School
1500 E Medical Center Dr
Ann Arbor, MI 48109
734-936-9010
Locations and availability (3)

Education ?

Medical School Score Rankings
Case Western Reserve University (2004)
  • Currently 4 of 4 apples
Top 25%

Affiliations ?

Dr. Leventhal is affiliated with 2 hospitals.

Hospital Affilations

Score

Rankings

  • University of Michigan Hospitals & Health Centers
    1500 E Medical Center Dr, Ann Arbor, MI 48109
    • Currently 4 of 4 crosses
    Top 25%
  • University of Michigan Health System
  • Publications & Research

    Dr. Leventhal has contributed to 4 publications.
    Title Chronic Histological Effects of the Flat Interface Nerve Electrode.
    Date August 2006
    Journal Journal of Neural Engineering
    Excerpt

    The flat interface nerve electrode (FINE) is designed to reshape peripheral nerves into favorable geometries for selective stimulation. Compared to cylindrical geometries, the ovoid geometries created by the FINE allow more space for contact placement. Furthermore, the amount of electrically excitable tissue between stimulating contacts and target axons is reduced. In this study, the nerve response to the presence of the FINE is examined histologically. Three different FINEs were designed to reshape peripheral nerves to different opening heights designated as 'wide' (1.3 mm), 'medium' (0.5 mm) and 'narrow' (0.1 mm) cuffs. Twelve adult cats were implanted with one cuff each (four in total of each design) on their right sciatic nerves. At least 3 months later, the animals were sacrificed and their sciatic nerves were harvested for histological evaluation. Cross-sectional areas and eccentricities (defined as the major axis divided by the minor axis of the closest fit ellipse to a region) of the nerves were measured to assess the degree of reshaping. The wide and medium cuff designs significantly reshaped the nerves compared to control nerves, though there was no significant difference in eccentricity between nerves implanted with wide and medium cuffs. There was extensive deposition of connective tissue in the epineurium of all nerves implanted with cuffs. No significant difference in fiber counts was measured in any of the groups studied. Only nerves implanted with narrow cuffs showed evidence of axonal injury and/or demyelination. These results, coupled with stimulation selectivity measurements made on the same animals, suggest that safe, selective electrodes can be designed with ovoid geometries. Moderate reshaping caused no damage, while extreme reshaping generated mild-to-moderate nerve damage. It might be possible, however, to redesign the cuffs to slowly reshape the nerves.

    Title Chronic Measurement of the Stimulation Selectivity of the Flat Interface Nerve Electrode.
    Date October 2004
    Journal Ieee Transactions on Bio-medical Engineering
    Excerpt

    The flat interface nerve electrode (FINE) is an attempt to improve the stimulation selectivity of extraneural electrodes. By reshaping peripheral nerves into elliptical cylinders, central fibers are moved closer to the nerve-electrode interface, and additional surface area is created for contact placement. The goals of this study were to test the hypothesis that greater nerve reshaping leads to improved selectivity and to examine the chronic recruitment properties of the FINE. Three FINEs were developed to reshape peripheral nerves to different degrees. Four electrodes of each type were implanted on the sciatic nerves of 12 cats and tested for selectivity over at least three months. There was physiologic evidence of nerve injury in two cats with the tightest cuffs, but the other animals behaved normally. All cuff types were capable of selectively activating branches of the sciatic nerve, as well as groups of fibers within branches. The electrodes that moderately reshaped the nerves demonstrated the most selectivity. Both the selectivity measurements and the recruitment curve characteristics were stable throughout the implant period. From an electrophysiological standpoint, the FINE is a viable alternative for neuroprosthetic devices. A histological analysis of the nerves is under way to evaluate the safety of the FINE.

    Title Subfascicle Stimulation Selectivity with the Flat Interface Nerve Electrode.
    Date October 2003
    Journal Annals of Biomedical Engineering
    Excerpt

    The flat interface nerve electrode (FINE) is an alternative to cylindrical nerve cuffs for functional electrical stimulation (FES). By elongating the nerve in cross section, the FINE places more stimulating contacts around the nerve, and moves central axons closer to the electrode surface. Previous experiments have demonstrated that the FINE can activate selectively each fascicle in the cat sciatic nerve, and modeling studies have indicated that it should be possible to selectively activate groups of axons within individual fascicles. This hypothesis is tested using a combination of experimental and modeling techniques. Pairs of contacts stimulating the same fascicle were tested for subfascicle level selectivity, defined as the fraction of fibers activated by one contact but not by the other. It was possible to achieve greater than 90% selectivity with the FINE, but there was considerable variation in the results. The modeling studies showed that the selectivity achievable with a given contact pair depended strongly on the relative locations of the electrode and fascicle. Therefore, reshaping the cross section of a nerve can provide selectivity at the subfascicular level, but the electrode design must be optimized to improve selectivity across different nerve geometries.

    Title Eroded Monomode Optical Fiber for Whispering-gallery Mode Excitation in Fused-silica Microspheres.
    Date
    Journal Optics Letters
    Excerpt

    We demonstrate the efficient excitation of high-Q whispering-gallery modes in near-spherical fused-silica microparticles in the size range 60-450 microm by the use of an eroded monomode optical fiber. When the sphere is placed in the evanescent field of the guided fiber mode, light is resonantly coupled from the fiber into the microparticle. We report a broadening of resonance modes and a shift of the resonance central frequency as the coupling strength is increased by reduction of the gap between the sphere and the fiber.


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