Fibrous Encapsulation of Self-Sizing Spiral Cuff Electrode
Cross section of nerve where a spiral cuff had been implanted
for seven months (top). Empty outer area is where the cuff
had been. Narrow layer of encapsulation tissue can be seen
around the nerve and the cuff.
In the lower right, a cross section of a nerve with two wraps
of a spiral cuff around it is shown.
Responses to Self-Sizing Spiral Cuff Electrode.
CNR: Cuff to Nerve Ratio is shown at top of the table.
At 7 to 11 Months after implantation , no detectable impairment
Type-1 response." - These nerves exhibit the thin myelin
that is associated with axonal regeneration and remyelination.
Type-2 response” - Axonal swelling and distension were
also observed. Distended axons generally show an extremely
thin myelin sheath whereas regenerated or remyelinated axons
show a reduced, but still substantial sheath. The density
and distribution of myelinated axons appears normal in these
Type-3 response”- If no apparent loss of myelinated
axon density was found at the distal level, the effect at
the cuff level most likely due to Schwann cell proliferation
rather than to axonal loss. Nerves with an apparent low myelinated
axon density at the cuff level but none at the distal level.
Type -4 response” - Nerves that exhibit an apparent
low myelinated axon density at both the cuff and distal levels.
Conclusion - insult was random and could not be attributed
to CNR- most likely due to the implant procedure.