CHAPTER XI

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.

_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.

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.