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CHAPTER 22
are depressed but none of them abolished, while reflex depression in the macaque,
baboon and especially the chimpanzee may be almost as great as or even greater than in
man.
The duration of spinal cord depression in man varies considerably, and reflex
activity of skeletal muscles may appear within a period from 3 or 4 days (this occurs in
particular in young individuals) and up to 6 weeks after injury. Septic conditions result
ing from pressure sores and infection of the urinary tract play an essential part in delaying
reflex automatism of the spinal cord. The physiological derangement in the isolated cord
during spinal shock naturally also affects the onset of automaticity of bowels and bladder,
which may be considerably delayed, as may also be the dysbalance of temperature
regulation, in transections of the cervical cord. This will be discussed in the respective
chapters concerning these problems.
(4)
Caudal and cephalad direction of reflex depression
It is generally agreed that the direction of reflex depression is from proximal to caudal—
i.e. the reflex depression is more severe and lasts longer in the segments of the isolated
cord situated more proximal to the transection, and the distal segments follow later.
Thus, in complete transverse lesions of the cervical cord, the arm and finger reflexes as
well as the abdominal reflexes are abolished immediately, while the reflexes of the distal
parts of the paralysed legs, such as ankle jerks and, in particular, reflex responses to
plantar stimulation (plantar or dorsi flexion of the toes and weak withdrawal response of
one or both legs) as well as bulbo-cavernosus and anal reflexes may be present or dis
appear only after some latent period, a proof of the dysbalance of the afferents and
efferents at various levels within the isolated cord.
From experimental studies on cord transection in animals, it was for many years
accepted that the transient depression of the excitability of the cord in the stage of spinal
shock manifests itself in caudal direction only. Sherrington mentioned, as an example
of the absence of headwards spread of depression due to spinal shock, the fact that, in
spinal animals after transection of the 5th cervical segment, the respiratory activity of the
phrenic motor cells is hardly affected and in transection behind the brachial enlargement
he found the reaction of the upper limbs little if at all disturbed. However, this concept
was not confirmed by Ruch & Watts (1934), who described distinct changes in reflex
activity following post-brachial transection or cold block of the spinal cord. Earlier,
Monakow (1914) who introduced the term 'diaschisis' (meaning dissolution of neural
function) postulated that diaschisis is operative not only in the downward direction but
also upward. From my personal experience in traumatic complete lesions in man, an
upward spread of transient depression of cord function in the initial stages of spinal
shock is by no means unusual. For instance, the transient impairment of finger move
ment and loss of reflex of the forearm may occur in upper thoracic lesions as low as T4.
This transient impairment representing a concussional effect of the cord above the
transection may disappear within a few hours or few days after injury.
