THE SCALP
Surgical Anatomy--Injuries: _Contusion_; _Haematoma_;
_Cephal-haematoma_; _Wounds_; _Avulsion_--Diseases: _Infective
conditions_; Cystic and solid tumours; Air-containing swellings;
Vascular tumours.
#Surgical Anatomy.#--The _skin_ of the scalp is intimately united to
the _epicranial aponeurosis_ by a network of firm fibrous tissue
containing some granular fat, and representing the subcutaneous
connective tissue. These three layers constitute the scalp proper, and
they are so closely connected as to form a single structure which can
be moved to a certain extent by the action of the epicranius muscle.
The epicranius (occipito-frontalis) muscle with its aponeurosis
extends from the superciliary ridge in front to the superior nuchal
(curved) line of the occipital bone behind, and laterally to the level
of the zygoma where it blends with the temporal fascia. Between the
scalp proper and the _pericranium_ is a quantity of loose areolar
tissue, in the meshes of which extravasated blood or inflammatory
products can rapidly spread over a wide area. Blood extravasated under
the pericranium is limited by the attachments of this membrane at the
sutures.
The _blood supply_ of the frontal region is derived from the internal
carotid arteries through their supra-orbital branches; the remainder
of the scalp is supplied from the external carotids through their
temporal, posterior auricular and occipital branches. The vessels,
which run in the subcutaneous tissue, superficial to the epicranial
aponeurosis, anastomose freely with one another and across the middle
line. The main branches run towards the vertex, and incisions should,
as far as possible, be directed parallel with them.
The _venous return_ is through the frontal, temporal, and occipital
veins. These have free communications, through the _emissary veins_,
with the intra-cranial sinuses, and by these routes infective
conditions of the scalp may readily be transmitted to the interior of
the skull. The most important of the emissary veins are: the
_mastoid_, _condyloid_, and _occipital_, passing to the transverse
(lateral) sinus; the _parietal_, which enters the superior sagittal
(longitudinal) sinus; and a branch from the nose which traverses the
foramen caecum and enters the anterior end of the superior sagittal
sinus.
The supra-trochlear, supra-orbital and auriculo-temporal branches of
the trigeminal nerve, together with the greater and lesser occipital
nerves, supply the scalp with sensation, while the muscles are
supplied from the facial nerve.
The _lymph vessels_ pass to the parotid, occipital, mastoid, and
submaxillary groups of glands, the different areas of drainage being
ill-defined.
INJURIES OF THE SCALP
#Subcutaneous Injuries.#--_In simple contusion_ of the superficial
layers, owing to the density of the tissues, the blood effused is
small in quantity and remains confined to the area directly injured,
which is firm and tender to the touch, swollen and discoloured. The
disappearance of the swelling may be hastened by elastic pressure and
massage.
_Haematoma of the scalp_ results when lacerated vessels bleed into the
sub-aponeurotic space. Owing to the laxity of the connective tissue in
this area, the effused blood tends to diffuse itself widely, and,
according to the position assumed by the patient, gravitates to the
region of the eyebrow, the occiput, or the zygoma. When a large artery
is torn the swelling may pulsate. A haematoma of the scalp may readily
be mistaken for a depressed fracture of the skull, owing to the fact
that the margins of the effusion are often raised and of a firm
resistant character. A differential diagnosis can usually be made by
observing that the swelling is on a higher level than the rest of the
skull; that the raised margin can to a large extent be dispersed by
making firm, steady pressure over it with the finger; and that, on
doing so, the smooth and intact surface of the skull can be
recognised. When a fracture exists, the finger sinks into the
depression and the irregular edge of the bone can be felt. In doubtful
cases, if cerebral symptoms are present, an exploratory incision
should be made.
Even a large haematoma is usually completely absorbed, but the
dispersion of the clot may be hastened by massage and elastic
pressure. Any excoriation or wound of the skin must be disinfected.
Sometimes a blood-cyst, consisting of a connective-tissue capsule
filled with a yellowish-red fluid, remains, and may require to be
emptied with a hollow needle.
These effusions are to be distinguished from the _cephal-haematoma_, in
which the blood collects between the pericranium and the bone. This is
oftenest seen in newly born children as a result of pressure on the
head during delivery, and is characterised by its limitation to one
particular bone--usually the parietal--the further spread of the blood
being checked by the attachment of the pericranium at the sutures.
Occasionally a permanent thickening of the edges of the bone remains
after the absorption of the extravasated blood. This condition is to
be diagnosed from traumatic cephal-hydrocele (p. 390).
#Wounds of the Scalp.#--So long as a scalp wound, however extensive,
is kept free from infection, it involves comparatively little risk,
but the introduction of organisms to even the most trivial wound is
fraught with danger, on account of the ease and rapidity with which
the infection may spread along the emissary veins to the meninges and
intra-cranial sinuses.
The deeper the wound, the greater is the risk. If the epicranial
aponeurosis is divided, the "dangerous area" between it and the
pericranium is opened, and if infection occurs, it may lead to
widespread suppuration. Should the wound extend through the
pericranium, infection is more liable to spread to the bone and to the
cranial contents.
The usual varieties of wounds--incised, punctured, contused, and
lacerated--are met with in the scalp, and they vary in degree from a
simple superficial cut to complete avulsion. For medico-legal purposes
it is important to bear in mind that a scalp wound produced by the
stroke of a blunt weapon, such as a stick or baton, may closely
simulate a wound made with a cutting instrument.
On account of the density of the integument and its close connection
with the aponeurosis, scalp wounds do not gape unless the epicranial
aponeurosis is widely divided. This facilitates union in incised
wounds, but interferes with drainage in the long narrow tracts which
result from punctures, and which are so liable to be infected and to
implicate the sub-aponeurotic space, the pericranium, or even the
bone. It also favours the inclusion in the wound of a foreign body,
such as the broken point of a knife, or a piece of glass. The bleeding
from scalp wounds is often profuse and difficult to control, because
the vessels, fixed as they are in the dense subcutaneous tissue,
cannot retract and contract so as to bring about the natural arrest of
haemorrhage, and it is difficult to apply forceps or ligatures to their
cut ends, suture ligatures are more efficient. On account of the free
arterial anastomosis in the deeper layers of the integument, large
flaps of scalp will survive when replaced, even if badly bruised and
torn, and it is never advisable to cut away any un-infected portion of
the scalp, however badly it may be lacerated or however narrow may be
the pedicle which unites it to the head.
_Gun-shot wounds_ of the scalp are usually associated with damage to
the skull and brain. A spent shot, however, may pierce the scalp, and
then, glancing off the bone, lodge in the soft parts.
_Complete Avulsion._--In women, the scalp is sometimes torn from the
cranium as a result of the hair being caught in revolving machinery.
The portion removed, as a rule, consists of integument and aponeurosis
with portions of muscle attached. In a few cases the pericranium also
has been torn away. So long as any attachment to the intact scalp
remains, the parts should be replaced, and, if asepsis is maintained,
a satisfactory result may be hoped for. When the scalp is entirely
separated, recourse must be had to skin-grafting.
_Treatment of recent Scalp Wounds._--To ensure asepsis, the hair
should be shaved from the area around the wound, and the part then
purified. Gross dirt ground into the edges of lacerated wounds is best
removed by paring with scissors. Undermined flaps must be further
opened up and drained--by counter-openings if necessary. When there is
reason to suspect their presence, foreign bodies should be sought for.
Bleeding is arrested by forci-pressure or by ligature; when, as is
often the case, these measures fail, the haemorrhage may be controlled
by passing a needle threaded with catgut through the scalp so as to
include the bleeding vessel. The wound is stitched with horse-hair or
silk, and, except in very small and superficial wounds, it is best to
allow for drainage. With the use of iodine as a disinfectant, it is
often advantageous to dispense with dressings altogether.
#Complications of Scalp Wounds.#--The most common complications are
those due to infection, which not only aggravates the local condition,
but is apt to lead to spreading cellulitis, osteomyelitis, meningitis,
or inflammation of the intra-cranial sinuses. These dangerous sequelae
are liable to follow infection of any scalp wound, but more especially
such as implicate the sub-aponeurotic area, or the pericranium. In the
integument, a small localised abscess, attended with pain and oedema
of surrounding parts, may form. Pus forming under the aponeurosis is
liable to spread widely, pointing above the eyebrow, in the occipital
region, or in the line of the zygoma. Suppuration under the
pericranium tends to be limited by the inter-sutural attachments of
the membrane. Necrosis of the outer table, or even of the whole
thickness of the skull, may follow, although it is by no means
uncommon for large denuded areas of bone to retain their vitality.
The onset of infection is indicated by restlessness, throbbing pain
and heat in the wound, a feeling of chilliness or the occurrence of a
rigor, and tension of the stitches from oedema of the surrounding
tissues. The oedema often extends to the eyelids and face; a puffiness
of the eyelids, indeed, is not infrequently the first evidence of the
occurrence of infection in the wound.
_Treatment._--When suppuration ensues, the stitches should be removed,
the wound opened up and purified with eusol, and packed. A dressing of
ichthyol and glycerine should be employed for a few days.
_Erysipelas of the scalp_ may originate even in wounds so trivial as
to be almost invisible, or from suppurative processes in the region of
the frontal sinuses or nasal fossae. It tends to be limited by the
attachments of deep fasciae, and seldom spreads to the cheek or neck.
Symptoms of cerebral complications, in the form of delirium or coma,
and of meningitis may supervene. Cellulitis beneath the aponeurosis
from mixed infection is a dangerous complication.
DISEASES OF THE SCALP
#Infective Conditions.#--It is not uncommon for _localised abscesses_
to occur in the subcutaneous cellular tissue in delicate children, and
such collections are not infrequently associated with pediculi,
impetigo, or chronic dermatitis. They develop slowly and painlessly,
and are only covered by a thin, bluish pellicle of skin. It is not
improbable that they result from a mixed infection by pyogenic and
tuberculous organisms. As a rule they heal quickly after incision and
drainage, but when they are allowed to burst, tedious superficial
ulcers may form. Localised abscesses may also form in connection with
disease of the cranial bones. _Suppuration_ following upon injuries
has already been referred to.
_Boils and carbuncles_ are not common on the hairy part of the scalp.
_Lupus_ rarely originates on the scalp, although it may spread thither
from the face. _Syphilitic_ lesions are common and present the same
characters as elsewhere. Gummata may develop in the soft parts, but
more commonly they take origin in the pericranium or bone. _Eczema
capitis_ is of surgical importance only in so far as it often forms
the starting-point of infection of lymph glands by pyogenic and other
organisms.
#Cystic and Solid Tumours.#--A great variety of swellings is met with
in the scalp.
_Sebaceous cysts_ or _wens_ are of frequent occurrence, and have been
described in Volume I.
A _dermoid cyst_ is most commonly situated over the position of the
anterior fontanelle, in the region of the occipital protuberance, or
at the lateral angle of the orbit. As it frequently lies in a gap in
the skull, it may be connected by a pedicle with the dura mater, and
is liable to be mistaken for a meningocele.
[Illustration: FIG. 177.--Multiple Wens.
(Photograph lent by Sir George T. Beatson.)]
_Serous cysts_ are occasionally found in the occipital region, and are
believed to be meningoceles that have become shut off from the
interior of the skull before birth.
_Adenomas_ originating in the sebaceous or sweat glands are sometimes
multiple, of a purplish colour, and the skin covering them is thin and
glistening. They show a tendency to ulcerate and fungate, giving rise
to a foetid discharge, and may be mistaken for epithelioma; they are
also liable to become the seat of epithelioma. They are treated by
excision.
Large, flat _papillomas_ or warts may be single or multiple; they are
of slow growth, and as they may also become the starting-point of
epithelioma, they should be removed.
[Illustration: FIG. 178.--Adenoma of Scalp.]
The _plexiform neuroma_ forms a loose soft tumour situated in the
course of one or more branches of the trigeminal nerve, especially
the supra-orbital branch. In its most aggravated form the tumour hangs
over the face or neck in large pendulous masses, and is described as a
_pachydermatocele_ (V. Mott).
A _sarcoma_ usually has its origin in the bones of the skull, and only
implicates the scalp secondarily.
_Epithelioma_ of the scalp may originate in relation to a wart, an
ulcerated wen or sebaceous adenoma, or the cicatrix of a burn. It may
affect comparatively young persons, may spread over a wide area, or
pass deeply and involve the bone. Free and early removal is indicated.
_Rodent cancer_ may originate on the scalp, but usually spreads
thither from the face.
In operating for extensive tumours of the scalp the haemorrhage is
sometimes formidable. It may be controlled by an elastic tourniquet
applied horizontally round the head, or if, on account of the position
of the tumour or from other causes, this is not practicable, by
ligation or temporary clamping of the external carotid on one or on
both sides.
#Air-containing Swellings#--_Pneumatocele Capitis._--Cases have been
recorded in which, as a result of pathological or traumatic
perforations of the mastoid, and less frequently of the frontal cells,
air has passed under the pericranium and given rise to a tense rounded
tumour, resonant on percussion, and capable of being emptied by firm
pressure. Such swellings exhibit neither pulsation nor fluctuation;
and as they are painless, and give rise to almost no inconvenience,
they do not call for treatment.
_Emphysema of the scalp_ may follow fractures implicating any of the
air sinuses of the skull, the air infiltrating the loose cellular
tissue between the pericranium and the aponeurosis, and on palpation
yielding a characteristic crepitation. It usually disappears in a few
days.
#Vascular Tumours.#--_Naevi_ on the scalp present the same features as
elsewhere. If placed over one of the fontanelles, a naevus may derive
pulsation from the brain, and so simulate a meningocele.
_Cirsoid aneurysm_ is usually met with in the course of the temporal
artery, and may involve the greater part of the scalp. Large,
distended, tortuous, bluish vessels pulsating synchronously with the
heart are seen and felt. They can be emptied by pressure, but fill up
again at once on removal of the pressure. The patient complains of
dizziness, headache, and a persistent rushing sound in the head.
Ulceration of the skin over the dilated vessels, leading to fatal
haemorrhage, may take place.
They may be treated by excision, after division and ligation of the
larger vessels entering the swelling; or the dilated vessels may be
cut across at several points and both ends ligated. Krogius recommends
the introduction of a series of subcutaneous ligatures so as to
surround the whole periphery of the pulsating tumour, and interrupt
the blood flow. Ligation of the main afferent vessels, or of the
external or common carotid, has been followed by recurrence, owing to
the free anastomatic circulation in the scalp. In some cases
electrolysis has yielded good results.
_Traumatic aneurysm_ of the temporal artery was comparatively common
in the days when the practice of bleeding from this vessel was in
vogue, but it is seldom met with now.
_Arterio-venous aneurysm_ may also occur in the course of the temporal
artery, as a result of injury, and is best treated by complete
extirpation of the segments of the vessels implicated.