Fiber Spectra Distribution of a Typical Peripheral Sensory Nerve

Sensory neuropathy is often selective for an individual sub-population of nerve fibers while sparing others.  This results in various types of “painless” and "painful" nerve damage or neuro-pathy.  This table illustrates the neuro-selectivity of standard sensory nerve tests and the Neurometer evaluation.  In one automated painless procedure, the Neurometer tests all three sub-populations of sensory nerve fibers .

Peripheral nerves are composed of three distinct sub-populations of nerve fibers that are characterized by their diameter.  The above figure above illustrates the number of fibers vs. diameter that comprise the typical sensory nerve.  These various sub-populations of nerve fibers transmit different sensations. The smallest (unmyelinated) fibers transmit dull pain and temperature, the middle diameter (small myelinated) fibers transmit fast pain, temperature and pressure sensation, and the largest (myelinated) fibers transmit touch and pressure sensation.  These three sub populations of nerve fibers work together to transmit normal sensation.  For example, when one touches a glass, first the glass is felt (at (50 m/s) and only afterward the temperature (at 1 m/s).  The right table below compares the neuroselectivity of the Neurometer CPT evaluation versus the Skin Punch Biopsy and the Nerve Conduction Velocity and the Somatosensory Evoked Potential evaluations. Additional diagnostic test comparisons are available at this link.

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