Floor plan - 2013 Annual Meeting - American Association for Hand ...

ASPN SCIENTIFIC PAPER SESSION B
In Vivo Microscopy of the Peripheral Nerve, a Quantitative Analysis Following Injury using
Optical Coherence Tomography (OCT)
Institution where the work was prepared: Massachusetts General Hospital, Harvard Medical School, Boston, MA,
USA
Francis Patrick Henry, MD; Hyle Boris Park, PhD; Esther A. Z. Rust; M.A. Randolph, MAS; Johannes F. DeBoer, PhD;
Jonathan M. Winograd, MD; Massachusetts General Hospital, Harvard Medical School
INTRODUCTION:
Electrophysiological and invasive ex vivo histological techniques remain the current gold standard method for assessing nerve injury
and regeneration. In vivo assessment of a nerve without destruction of the tissue would greatly advance both grading and monitoring
following neural injury. Optical Coherence Tomography (OCT) is a minimally-invasive optical tomographic imaging technique which
uses coherent light to offer good penetration with micrometer axial and lateral resolution in tissues. Using a multifunctional OCT system
we plan to quantitatively and qualitatively assess changes in optical density and birefringence of nerve following injury.
METHODS:
A standard demyelinating crush injury was reproduced in the sciatic nerves of male Sprague Dawley rats. Animals were randomized into
groups (n=8) and nerve exposure with OCT imaging was undertaken at day 1 and weeks 1, 2, 3 and 4 following injury. The uninjured
nerve was used as a control. Functional analysis was undertaken weekly with standardized walking track analysis. Histomorphometry of
both control and injured nerve was undertaken following imaging to allow verification of our findings.
RESULTS:
All animals demonstrated loss of sciatic nerve function following nerve injury. Recovery was documented with sciatic functional index
data approaching normal at four weeks. OCT imaging revealed a quantifiable change in birefringence of the nerve (as measured by
phase retardation graphs) following a simple crush injury. These changes can be characterized both visually and in graph form to indicate
definitive injury and recovery in a longitudinal pattern. Figures below are examples of a normal nerve and samples 2 and 3 weeks
following injury. Regeneration can be assessed with the recovery of phase retardation versus depth over time as characterized by a
change in the slope of the graph (red line). The initial decrease and subsequent increase following injury represents recovery and reorganization
of the nerve fibers.
CONCLUSION:
We conclude that OCT has the ability to image the peripheral nerve revealing quantitative and qualitative changes in composition
which may be used to grade injury and regeneration over time. This technology which permits in vivo, real time imaging of nerves could
provide invaluable diagnostic and prognostic information following neural injury.
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