Injuries of nerves and their consequences - Reflex Sympathetic ...

224 INJURIES OF NERVES.
themselves largely diseased,
— a fact which must be settled
connected with the existence of anal-
by other symptoms
gesia and the absence of reflex motions. In certain cases,
then, of spinal disease, the muscles continue to respond to
some form of current, and do not Avaste ;
while in others
the reverse occurs, just as in injuries of extra-central nerve
trunks.
When cutaneous anesthesia exists, it is often easy to
learn whether its cause lies in the nerves or the central
organs by following the plan proposed by Stich.* If the
insensible region can be made the point of departure of
reflex movements, the anaesthesia is of central birth, because
to have reflex motion an excitation must have
reached the spine, by which we infer healthy nerves,
while the mere presence of the anaesthesia will, in this
case,
indicate the existence of disease in
the spine above
the point which is the seat of the reflex power exhibited.
If the proof be negative, and if the excitation cause no
movement, we can arrive at no definite conclusion, until,
following the same sensitive nerve up the limb, and by
seeking to excite through it reflex acts, by touching the
skin with a hot sponge or ice at successive points, we learn
if at any upper portion of tegument we can produce this
result. Should we get an aflirmative reply, we may presume
that the anaesthesia is of peripheral origin. "When,
finally, the answer is negative up to the spine itself,
we
learn nothing by this method, the total absence of all
reflex movement being equally compatible with either
loss of conducting power in the peripheral trunks and
branches and with extensive alteration of spinal centres.
The value of this means must be necessarily limited by
the difiiculty of exciting reflex acts from all regions of skin.
* Empfehlung der Erregung von Keflexbewegungen als diagnostisches
Hilfsmittel (Annalen des Charite Krankenhauses zu Berlin, 1856.) Also
Jaccoud, Paraplegics, p. 498, whence this account is taken