INJURIES OF THE SKULL
Contusions--FRACTURES--Of the vault: _Varieties_--Of the Base:
_Anterior fossa_--_Middle fossa_--_Posterior fossa_.
The bones of the skull may be contused or fractured. These injuries
are not in themselves serious: their clinical importance is derived
from the injury to the intra-cranial contents with which they are
liable to be associated.
#Contusion# of the skull may result from a fall, a blow, or a gun-shot
injury. In the majority of cases the damage to soft parts--scalp,
meningeal vessels, or brain--overshadows the osseous lesion, which of
itself is comparatively unimportant.
FRACTURES OF THE SKULL
While it is convenient to consider separately fractures of the vault
and fractures of the base of the skull, it is to be borne in mind that
it is not uncommon for a fracture to involve both the vault and the
base. Fractures in either situation may be simple or compound.
FRACTURES OF THE VAULT
#Mechanism.#--When the skull is broken by _direct_ violence, the
fracture takes place at the seat of impact, and its extent varies with
the nature of the impinging object and the degree of violence exerted.
If, for example, a pointed instrument, such as a bayonet, a foil, or a
spike, is forcibly driven against the skull, the weapon simply crashes
through the bone, disintegrating it at the point of entrance, and
cracking or splintering it for a variable, but limited, distance
beyond. On the other hand, when the head is struck by a "blunt"
object--for example, a batten falling from a height--the force is
applied over a wider area and the elastic skull bends before it. If
the limits of its elasticity are not exceeded, the bone recoils into
its normal position when the force ceases to act; but if the bone is
bent beyond the point from which it can recoil, a fracture takes
place--"_fracture by bending_." The bone gives way over a wide area,
the affected portion may be comminuted, and one or more of the
fragments may remain depressed below the level of the rest of
the skull. Cracks and fissures spread widely in different
directions--often (70 to 75 per cent.) extending into the base. In
almost all fractures of the vault the inner table splinters over a
wider area than the outer, partly because it is more brittle and is
not supported from within, but also because the diffusion of the force
as it passes inwards affects a wider area. If a bullet traverses the
cranial cavity the inner table is more widely shattered at the
aperture of entrance, and the outer table at the aperture of exit. Von
Bergmann reported thirty cases in which the inner table alone was
fractured by a blow on the head.
Fractures by _indirect_ violence--that is, fractures in which the bone
breaks at a point other than the seat of impact--are almost always due
to violence inflicted with a blunt object, and acting over a wide
area--such, for example, as when the head strikes the pavement. Much
discussion has taken place as to the method of their production. It
has been shown that when the skull is depressed at one point by a
force impinging on it, it bulges at another, so that its whole contour
is altered. But the elasticity of the bone varies at different parts
of the skull, owing to differences in thickness and in structure. If,
therefore, the part which is depressed--that is, the part directly
struck--happens to be less elastic than the part which bulges, it
gives way, and a fracture by "bending" results; but if the bulging
part is the less elastic, it bursts outwards--_fracture by_
"_bursting_." The term "fracture by _contre-coup_" has been
incorrectly applied to such fractures when the area of bulging happens
to be opposite to the seat of impact. _Contre-coup_, properly
so-called, is only possible in a perfectly spherical body, which, of
course, the skull is not.
When a high-velocity bullet penetrates the head, it exerts on the
incompressible, semi-fluid brain an explosive (hydro-dynamic) force,
which is transmitted to all points on the inner surface of the skull
and leads to shattering of the bone.
_Repair._--The repair of fractures of the skull is usually attended
with an exceedingly small amount of callus. Except in the presence of
infection, separated fragments live and become reunited, but they may
unite in such a manner as to project towards the brain and, by
irritating the cortical centres, cause traumatic epilepsy. In
comminuted fractures, the lines of fracture remain permanently visible
on the bone, but fissured fractures may leave no trace. Gaps left in
the skull by injury or operation are, after a time, filled in by a
fibrous membrane, which may undergo ossification from the periphery
towards the centre, but unless the aperture is a small one it is
seldom completely closed by bone. The new bone which forms is derived
from the old bone at the margins of the opening. Permanent defects in
the skull are chiefly injurious if they are accompanied by lesions of
the underlying dura, such as adhesions to the brain; large gaps may
cause giddiness on stooping, or on forcible expiration, as in blowing
the nose or playing a wind instrument.
#Varieties.#--For descriptive purposes, fractures of the vault are
divided into the fissured, the punctured, the depressed, and the
comminuted varieties. Clinically, however, these varieties are often
combined. The practical importance of a given fracture depends upon
whether it is simple or compound, rather than upon the exact nature of
the damage done to the bone. Compound fractures which open the dura
mater are the most serious. Simple fractures result, as a rule, from
diffuse forms of violence, and are liable to spread far beyond the
seat of impact. Compound fractures result from severe and localised
violence--for example, the kick of a horse or the blow of a
hammer--and tend to be limited more or less to the seat of impact. In
gun-shot injuries, however, there are usually numerous fissures
radiating from the point at which the missile enters the skull.
#Fissured fractures# generally result from blows by blunt objects or
from falls, and they usually extend far beyond the area struck, in
most cases passing into the base. The fissure may pass through the
bone vertically or obliquely, and it may implicate one or both tables.
So long as the fracture is simple, it can scarcely be diagnosed except
by inference from the associated symptoms of meningeal or cerebral
injury. When compound, the crack in the bone can be seen and felt. It
is recognised by the eye as a split in the bone, filled with red
blood, which, as often as it is sponged away, oozes again into the
gap. In fractures by bursting a tuft of hair may be caught between the
edges of the fracture, and this adds to the difficulty of purifying
the wound.
_Diagnosis._--A normal suture may be mistaken for a fissured fracture.
A suture, however, may generally be recognised by its position, the
irregularity of its margins, and the absence of blood between its
edges. At the same time, it is not uncommon, especially in children,
for a suture to be sprung by violence applied to the head, or for a
fissured fracture to enter a suture and, after running in it for some
distance, to leave it again. The edges of a clean cut in the
periosteum may be mistaken for a fissure in the bone, especially if
reliance is placed on the probe for diagnosis. This error can be
avoided by raising the edge of the periosteum from the bone, with the
gloved finger. On combined auscultation and percussion a peculiar
"hollow-cask" sound may be detected in some cases of fissured fracture
of the vault.
Fissured fractures as such call for no _treatment_. When compound, the
wound must be disinfected; and intra-cranial complications, such as
meningeal haemorrhage, laceration of the brain, or infection, are to be
treated on the lines already described.
#Punctured fractures# are of necessity compound, and on account of the
risks of infection are to be looked upon as serious injuries. They
result from the localised impact of a sharp, and usually infected
object the point of which is not infrequently left either in the bone
or inside the skull. Fragments of bone are often driven into the
brain, and short fissures frequently pass in various directions from
the central aperture.
_Diagnosis._--When the instrument impinges on the head obliquely,
after piercing the scalp it may pass for some distance under it before
perforating the skull, so that on its withdrawal a valvular wound is
left, and at first sight it appears that only the scalp is involved.
Sometimes a foreign body left in the gap so fills it up that it is
difficult to detect the fracture with a probe or even with the finger.
In all doubtful cases the scalp wound should be sufficiently enlarged
to exclude such errors. We have known of a case of a man who died of
meningitis resulting from a punctured fracture of the vault caused by
the spoke of an umbrella, the fracture having escaped recognition
until the meningeal symptoms developed.
_Treatment._--The scalp wound must be purified, being opened up as far
as necessary for this purpose. The infected portion of bone should be
removed to render possible the purification of the membranes and
brain, and to permit of drainage.
#Depressed and Comminuted Fractures.#--As these varieties almost
always occur in combination, they are best considered together. The
terms "indentation fracture," "gutter fracture," "pond fracture," have
been applied to different forms of depressed fracture, according to
the degree of damage to the bone and the disposition of the fragments
(Figs. 188, 189, 190). These fractures may be simple or compound.
[Illustration: FIG. 188.--Depressed Fracture of Frontal
Bones--involving the air sinus on both sides--with a fissured fracture
radiating from it.
(From Professor Harvey Littlejohn's collection.)]
[Illustration: FIG. 189.--Depressed and Comminuted Fracture of Right
Parietal Bone: Pond Fracture. The patient sustained the injury twenty
years before death.]
[Illustration: FIG. 190.--Pond Fracture of Left Frontal Bone, produced
during delivery.
(From a photograph lent by Mr. J. H. Nicoll.)]
As a rule the whole thickness of the skull is broken, and, as usual,
the inner table suffers most. In infants the bones may be merely
indented, the fracture being of the greenstick variety. All degrees of
severity are met with, from a simple, localised indentation of the
bone, to complete smashing of the skull into fragments.
_Diagnosis._--When compound, the nature of these fractures is readily
recognised on exploring the wound, but their extent is not always easy
to determine, and it is not uncommon for extensive fissures to pass
into the base.
A haematoma of the scalp may readily be mistaken for a depressed
fracture. The condensation of the tissues round the seat of impact and
the soft coagulum in the centre, closely simulate a depression in the
bone; but if firm pressure is made with the finger, the irregular edge
of the bone can be recognised, and the depressed portion is felt to be
on a lower level. On the other hand, a depression in the bone is
sometimes obscured by an overlying haematoma, and unless great care is
taken the fracture may be overlooked.
_Treatment._--All are agreed that compound depressed and comminuted
fractures--whether associated with cerebral symptoms or not--should
be operated on to enable the wound to be purified, and the normal
outline of the skull to be restored by elevating or removing depressed
or separated fragments. Except in young children, in whom considerable
degrees of depression are frequently righted by nature, most surgeons
recommend operative interference even in simple fractures with the
object of elevating the depressed bone, and to anticipate subsequent
complications such as persistent headache, attacks of giddiness,
traumatic epilepsy, or insanity. Others, including von Bergmann and
Tilmanns, consider that the risk of such sequelae ensuing is not
sufficient to justify a prophylactic operation of such severity as
trephining.
The operation is described in _Operative Surgery_, p. 93.
FRACTURES OF THE BASE
The base of the skull may be fractured by a pointed object, such as a
fencing foil, a knitting pin, or the end of an umbrella, being forced
through the orbit, the nasal cavities, or the pharynx. These injuries
will be referred to in describing fractures of the anterior fossa.
The majority of basal fractures result from such accidents as a fall
from a height, the patient landing on the vertex or on the side of the
head, or from a heavy object falling on the head. The violence is
therefore indirect in so far as the bone breaks at a point other than
the seat of impact.
In other cases the base is broken by the patient falling from a height
and landing on his feet or buttocks, the force being transmitted
through the spine to the occiput, and the bone giving way around the
foramen magnum. Sometimes the condyle of the lower jaw is driven
through the base of the skull by a blow or fall on the chin, and
fissures radiate into the base from the glenoid cavity. It is usual to
describe these also as fractures by indirect violence, but as the
skull gives way at the point where it is struck, these are really
fractures by direct violence. Von Bergmann, Bruns, and Messerer have
done much to elucidate the mechanism of basal fractures.
In the consideration of the mode of production of basal fractures by
indirect violence, the irregular shape of the cavity, the varying
strength and thickness of its different parts, and the existence of
the foramina through the bone are to be borne in mind. The force
acting on the skull tends to increase one diameter of the cavity, and
to diminish the opposite diameter. The resulting fracture, therefore,
is due to bursting of the skull, and tends to take place at the part
which has least elasticity--that is, at the base. It has been found
that the site and direction of basal fractures bear a fairly constant
relation to the direction of the force by which they are produced.
When, for example, the skull is compressed from side to side, the line
of fracture through the base is usually transverse, and it may
implicate one or both sides (Fig. 191). On the other hand, when the
pressure is antero-posterior, the fracture tends to be longitudinal;
and when oblique, it tends to be diagonal.
[Illustration: FIG. 191.--Transverse Fracture through Middle Fossa of
Base of Skull.]
Fractures of the base usually take the form of a single fissure, or a
series of fissures, which, as a rule, run through the foramina in
their track. Small portions of bone are sometimes completely
separated. It is common for a fissure through the base to be
continued for a considerable distance on to the vault.
The fracture may involve only one fossa, but as a rule fissures
radiate into two or all of them. Fractures of the anterior and middle
fossae are usually rendered compound by tearing of the mucous membrane
of the nose, the pharynx, or the ear.
Basal fractures are frequently associated with contusion and
laceration of the brain, and also with injuries of one or more of the
cranial nerves.
#Fracture of the anterior fossa# may result from a blow on the
forehead, nose, or face; or from a punctured wound of the orbit or of
the nasal cavity. Often the injury is at first considered trivial, and
it is only when infective complications, in the form of meningitis or
cerebral abscess, develop, that its true nature is suspected. This
fossa may also be implicated in fractures of the vault, fissures
extending from the vertex to the orbital plate of the frontal bone, or
to the lesser wing of the sphenoid.
_Clinical Features._--Unless the fracture is compound through opening
into the nose or pharynx, there are few symptoms by which it can be
recognised. When compound, there may be bleeding from the pharynx or
nose from tearing of the periosteum and mucous membrane related to the
basi-sphenoid and ethmoid respectively. When the haemorrhage is
profuse, it is probable that the meningeal vessels or even the venous
sinuses have been torn. Cerebro-spinal fluid may escape along with the
blood, but it is seldom possible to recognise it. If the flow is long
continued, the patient may be conscious of a persistent salt taste in
the mouth, due to the large proportion of sodium chloride which the
fluid contains. In very severe injuries, brain matter may escape
through the nose or mouth.
Fracture of the anterior fossa is often accompanied by extravasation
of blood into the orbit, pushing forward the eyeball and infiltrating
the conjunctiva (_sub-conjunctival ecchymosis_). This occurs
especially when the orbital plate of the frontal bone is implicated.
The blood which infiltrates the conjunctiva passes from behind
forwards, appearing first at the outer angle of the eye and spreading
like a fan towards the cornea. Later it spreads into the upper eyelid.
When the orbital ridge is chipped off, without the cavity of the skull
being opened into, the haemorrhage shows at once both under the
conjunctiva and in the upper lid. If the frontal sinus is opened, air
may infiltrate the scalp.
The olfactory, optic, oculo-motor, pathetic, ophthalmic division of
the trigeminal, and the abducens nerves are all liable to be
implicated.
_Diagnosis._--It is scarcely necessary to state that bleeding from the
nose or mouth may occur after a blow on the face without the
occurrence of a fracture of the skull. It is only when it is long
continued and profuse that the bleeding suggests a fracture. Similarly
effusion of blood in the region of the orbit may be due to a simple
contusion of the soft parts ("black eye"), or to gravitation of blood
from the forehead or temple. Sub-conjunctival ecchymosis also may
occur independently of a fracture implicating the anterior fossa--for
example, in association with an ordinary black eye, or with fracture
of the orbital ridge or of the zygomatic (malar) bone.
Finally, paralysis of the cranial nerves may result from pressure of
blood-clot, or from the nerves being torn without the skull being
fractured.
#Fracture of the middle fossa# is usually the result of severe
violence applied to the vault, as, for example, when a man falls from
a height, or is thrown from a horse and lands on his head.
_Clinical features._--The most conclusive sign of fracture of the
middle fossa is the escape of dark-coloured blood in a steady stream
from the ear, followed by oozing of cerebro-spinal fluid. The bleeding
from the ear may go on for days, the blood gradually becoming lighter
in colour from admixture with cerebro-spinal fluid. Finally the blood
ceases, but the clear fluid continues to drain away, sometimes for
weeks, and in such quantity as to soak the dressings and the pillow.
In our experience, the escape of cerebro-spinal fluid is much less
common than is generally supposed. In most cases, on examining the ear
with a speculum, the tympanic membrane is found to be ruptured; when
it is intact, the blood and cerebro-spinal fluid may pass down the
Eustachian tube into the pharynx. The escape of brain matter from the
ear is exceedingly rare. Emphysema of the scalp sometimes results when
the fracture passes through the mastoid cells. The facial and acoustic
nerves and the maxillary and mandibular divisions of the trigeminal
are frequently implicated. Deafness is a serious and not uncommon
accompaniment of fracture of the middle fossa, as the fracture
involves the labyrinth and is attended with haemorrhage and the
formation of new bone.
_Diagnosis._--Care must be taken not to mistake blood which has passed
into the ear from a scalp wound, or which has its origin in a
fracture of the wall of the external auditory meatus or a laceration
of the tympanic membrane, for blood escaping from a fracture of the
base. Under these conditions the blood is usually bright red, is not
accompanied by cerebro-spinal fluid, and the flow soon stops. It is on
record[4] that blood and cerebro-spinal fluid may escape along the
sheath of the acoustic nerve without the bone being broken.
[4] Miles, _Edinburgh Medical Journal_, 1895.
#Fracture of the posterior fossa# is produced by the same forms of
violence as cause fracture of the middle fossa; it is specially liable
to result if the patient falls on the feet or buttocks.
_Clinical Features._--Sometimes a comparatively limited fracture of
the occipital bone results, and in the course of a few days blood
infiltrates the scalp in the region of the occiput and mastoid, or may
pass down in the deeper planes of the neck. As a rule, however, there
is no immediate external evidence of fracture. The patient is
generally unconscious, and shows signs of injury to the pons and
medulla, causing interference with respiration, which soon proves
fatal. The rapidly fatal issue of these cases usually prevents the
manifestation of any injury to the posterior cranial nerves.
_Diagnosis of Basal Fractures._--In the diagnosis of fractures of the
base, reliance is to be placed chiefly upon: (1) the nature of the
injury; (2) the diffuse character of the cerebral symptoms; (3) the
evidence of injury to individual cranial nerves; (4) the occurrence of
persistent bleeding from the nose, mouth, or ear; (5) the
extravasation of blood under the conjunctiva or behind the mastoid
process; and (6) the presence of blood in the cerebro-spinal fluid
withdrawn by lumbar puncture. In rare cases the diagnosis is made
certain by the escape of cerebro-fluid or of brain matter from the
nose, mouth, or ear.
It must be admitted, however, that in a large proportion of cases
which end in recovery, the diagnosis of fracture of the base is little
more than a conjecture. The external evidence of damage to the bone is
so slight and so liable to be misleading, that little reliance can be
placed upon it. The associated cerebral and nervous symptoms also are
only presumptive evidence of fracture of the bone. In all cases,
however, in which there is reason to suspect that the base is
fractured, the patient should be treated on this assumption. It is
often found that, when there are no cerebral symptoms present, it is
difficult to convince the patient of the necessity for undergoing
treatment, and of the risk involved in his leaving his bed and
resuming work.
_Prognosis in Basal Fractures._--The prognosis depends upon the
severity of the cerebral lesions, and on the occurrence of traumatic
oedema or infective intra-cranial complications. Many cases prove
fatal within a few hours from the associated injury to the brain, the
patient dying from cerebral compression due to haemorrhage. If the
patient survives two days, the prognosis is more hopeful (Wagner). It
is possible that the free escape of blood from the nose or ear may in
some cases prevent compression, and to a certain extent render the
prognosis more favourable. Punctured fractures are frequently fatal
from infective complications--meningitis, sinus thrombosis, and
cerebral abscess. These complications are also liable to occur in
fractures rendered compound by opening into the nose, pharynx, or ear,
but they are less common than might be expected.
_Treatment._--The general treatment includes that for all head
injuries. In a number of cases attended with symptoms of compression,
benefit has followed the relief of intra-cranial tension by a
decompression operation. The withdrawal of 30 or 40 c.c. of
cerebro-spinal fluid by lumbar puncture has also proved beneficial in
the same way; Quenu strongly recommends repeated puncture in serious
cases. In a few cases this procedure has been followed by sudden
death.
Steps must be taken to prevent infection from the mucous surfaces
implicated. This is exceedingly difficult in fractures opening into
the pharynx and nose. Owing to the general condition of the patient,
it is usually impossible to employ nasal douching or mouth washes, but
spraying the cavities with peroxide of hydrogen or other antiseptics
may be employed with benefit. In fractures of the middle fossa, the
ear should be gently sponged out and the meatus plugged with gauze,
retained in position by adhesive plaster or a bandage. When there is a
persistent escape of blood or cerebro-spinal fluid, the dressing
requires to be changed frequently.
In compound fractures of the anterior fossa due to perforation through
the orbit, the frontal bone should be trephined to admit of the
removal of loose fragments or of any foreign body that may have
entered the skull and to provide for drainage.