Page 142 - Edited - Webster HEAD AND NECK - part 2-Merge PDF

HN 330

sinuses is usually rapidly fatal.) The perturbations in the foetal circulatory system caused by marked perinatal
anoxia may cause intracerebral or intraventricular haemorrhage - the latter usually fatal.

2. Specific peripheral and spinal nerve and brachia, plexus injuries at birth and in later
life.

I. With modern obstetric practice, such birth injuries are again rare. Of the cranial nerves, the seventh
(facial) may be damaged by mis-applied obstetric forceps, the tip of one blade of which, in the normal absence
of the mastoid process in the newborn, can extend beneath the temporal bone and crush the nerve, sometimes,
(but rarely), on both sides. The facial palsy is not pleasing to the parents, and if bilateral can make suckling
difficult, but usually rapidly recovers.

II. THE BRACHIAL PLEXUS

That the greater part of the innervation of the upper limb is innervated by cervical spinal nerves has
certain consequences.

(1) The upper limb dermatomes (HN 332) are virtually all cervical: you should remember the
sequence: shoulder C4; lateral arm C5; lateral forearm and thumb C6; three lateral fingers and
corresponding palm and dorsum of hand C7; (the sequence now reverses, moving towards the trunk): little
finger and corresponding hand and wrist C8; medial forearm Tl; medial arm T2; axilla T3.

(2) The upper limb muscles receive segmental innervation in a regular way and particular
movements are dependent upon particular spinal nerves (HN 333).

(3) It follows that if specific movements depend on specific spinal nerves, so must upper limb
tendon jerks (HN 333; 334). The sensibility of upper limb dermatomes by definition depends upon the integrity
of particular cervical spinal nerves and cord segments.

(4) Pathology of the cervical vertebral column (e.g. severe osteoarthritis) may present as
disturbance so of upper limb functions - pain, tingling, enfeebled movements and muscle wasting. These
symptoms and signs will relate to particular dermatomes and muscles/movements.

(5) The obliquity of descent of spinal nerves C5-C8 into the upper limb means that violent neck
movements can disrupt the brachial plexus. HN 335 shows that different relative movements of the upper limb
and neck put undue tension on either upper or lower brachial plexus roots in an entirely predictable manner.
Thus:

a) Lower brachial plexus/spinal nerve lesions

(i) Déjerine-Klumpke palsy. If, in an effort to promote the delivery, traction is applied to one upper limb
which has been delivered before the head (and rest of the foetus), the lowermost roots [usually C(7) and 8 and
Th1 - virtually corresponding to the lowermost trunk of the plexus and root value of the ulnar nerve, but
overlapping the root values of both median and radial nerves] of the brachial plexus may be stretched (HN 335
Fig. D). If, during breech delivery, one arm is retained with the head, similar effects result from
tugging inexpertly on the delivered trunk (c.f. HN 335 Fig. D & 336). Fig. HN 336 also shows that this same
injury occurs in adults who, when falling from a height, grab at a support in an effort to break their fall. It can
also occur as a consequence of sitting with one arm outstretched - say along the back of a park bench or
settee - for long periods, as when smooching, or very drunk - or both. Hence its alternative name "Saturday night
paralysis". Finally, chest surgery may require the patient's arm to be pulled alongside his/her face for long
periods: the lower brachial plexus is vulnerable, especially if muscle-relaxing drugs are used. The sensory loss
or numbness and paraesthesiae lies within dermatomes C8 and Thl (compare HN 337 & 332). This is
accompanied by a lower motor neuron (flaccid) paralysis of muscles which extend the elbow and flex the
wrist, as well as of the intrinsic muscles of the hand (HN 333). The elbow is therefore flexed, the wrist extended
and all the fingers "clawed" (HN 337). If the injury is so severe that the first thoracic spinal nerve or its anterior

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