High resolution ultrasound imaging after complete median or ulnar nerve transection; a pilot study

Currently, there is no easily accessible non-invasive technique available to
visualize peripheral nerves. The existence of such a technique would be useful
in diagnosing nerve transections and follow-up after nerve repair. After nerve
repair sprouts will form and regenerating axons will grow into the distal
stump. Besides a Tinel*s sign (distal tingling on percussion of the nerve),
which is not always present, there are no clinical signs of regeneration until
the axons reach the muscles or skin receptors. In practice this may last up to
12 months depending on the distance that needs to be bridged by the
regenerating nerve, the type of nerve, the age of the patient and numerous
other factors. If function fails to return within the expected period, surgical
exploration may be justified. Causes of failure of nerve regeneration may be a
discontinuity of the nerve, obstruction by fibrosis or the formation of a
neuroma. In these cases the patient would benefit from earlier exploration to
resolve the cause and reestablish nerve function in an earlier phase.

Ultrasound scanning is a non-invasive imaging technique applied widely in
medicine. A disadvantage compared to other imaging techniques is its low
spatial resolution. Recently, a High Resolution (14MHz) Ultrasound (HR US)
scanner has become available in our institution. Pilot tests showed that it is
capable of displaying large nerves in healthy subjects in clear contrast to its
environment. Using this technique the nerve diameter and circumference, and its
aspect (density (grayness) and inhomogeneity) can be quantified. These
parameters may be indicative for nerve regeneration and therefore HR US may be
a useful technique to follow nerve regeneration after nerve repair in large
nerves.

The aim of our study is to investigate the value of HR US to visualize and
quantify regeneration of transected median or ulnar nerves as a function of
time after surgical nerve repair.

The present study will be of a prospective nature. Patients after complete
median or ulnar nerve transection and repair will undergo HR US scanning
examinations of the arm 1, 3, 6 and 12 months postoperatively. These additional
HR US investigations will be scheduled on the same day as regular appointments
in the outpatient clinic. HR US data will be correlated to clinical findings,
moving and static 1-point and 2-point-discrimination and EMG data.

There are no adverse effects known of ultrasound investigations at 10-14 MHz.
The concentric needle EMG is experienced as (mildly) unpleasant, depending on
the muscle under investigation and can occasionally cause bruises. All other
EMG investigations are not invasive and have no known adverse effects.

Although not likely, a nerve repair may fail. In those cases this will probably
be visualized with HR US, and these subjects will be excluded from the study
and sent to the treating plastic surgeon for further evaluation and treatment
accordingly. Otherwise, the participation of patients in this study is of no
influence on their treatment.

Further, no unexpected findings with clinical relevance are expected in this
investigation.