Chapter 22

DISEASES OF THE CRANIAL BONES

Suppurative periostitis and osteomyelitis--Tuberculosis-- Syphilis--Tumours.

#Suppurative Periostitis and Osteomyelitis.#--These conditions may be the result of infection through the blood stream, but as a rule they follow upon a breach of the surface caused by a wound, a severe burn as in epileptics, a tertiary syphilitic ulcer, or a compound fracture that has become infected. Sometimes they follow suppuration in the middle ear and mastoid or in the frontal sinus, and epithelioma and rodent cancer that has ulcerated and become infected after spreading from the face towards the vertex. They are occasionally associated with acute cellulitis of the scalp. When the infection is blood-borne suppuration occurs on both aspects of the bone--a point of importance in treatment.

The illness is usually ushered in by a rigor, and this is soon followed by other signs of suppuration--high temperature, pain and tenderness, and the formation of a fluctuating swelling in relation to the bone. When pus forms between the bone and the dura, there is a characteristic oedema of the overlying area of the scalp--spoken of as _Pott's puffy tumour_--which is of value as indicating the extent of the disease in the bone, and of the collection of pus between it and the dura. When suppuration occurs under the pericranium, an incision gives exit to a quantity of pus, and exposes an area of bare bone. If the incision is made early, this bone may soon be covered by granulations and recover its vitality; but if operation is delayed, it usually undergoes necrosis. The sequestrum that forms includes, as a rule, only the outer table, but in some cases the whole thickness of the bone undergoes necrosis. In either case the separation of the sequestrum is an exceedingly slow process, and is not accompanied by the formation of new bone. When the whole thickness of the skull is lost, there may be a protrusion of the contents of the skull--hernia cerebri; should the patient survive, the gap becomes filled in by a dense fibrous membrane which is fused with the dura mater.

Serious complications, in the form of meningitis, cerebral abscess, sinus phlebitis, and general pyaemia, are liable to develop at any time during the progress of the infection, and we have seen pyaemia develop after the suppuration in the skull had been recovered from.

_Treatment._--Early, free, and, if necessary, multiple incisions are indicated to admit of disinfection of the affected area, and of the establishment of drainage. If the symptoms point to suppuration having occurred between the bone and the dura, the skull should be trephined and further bone removed with the rongeur forceps as may be required.

Time may be saved by separating the sequestrum with the aid of an elevator or sharp spoon, or by chiselling away the dead part till healthy vascular bone is reached.

#Tuberculosis# of the cranial vault is usually met with in children. The disease commences in the diploe, and results in the formation of a central sequestrum, around and beneath which the tuberculous process spreads. Granulations form between the skull and the dura, and on the outer aspect lifting up the pericranium. The sequestrum is slowly thrown off, and when separated is circular like a coin and presents worm-eaten edges.

A circumscribed, tender swelling forms, at first yielding an obscure sensation of fluctuation, but later, when the pus is no longer confined under the pericranium, assuming the characters of a cold abscess, which gradually becomes superficial, and eventually bursts through the scalp, forming one or more sinuses.

The abscess should be laid open, all tuberculous granulations scraped away, and the sequestrum removed, with the aid of the chisel if it has not already become loose. On inserting the finger through the opening, it appears to penetrate to an alarming extent; this is due to the accumulation of tuberculous material between the skull and the dura mater, depressing the latter. After healing is completed, a depression or gap in the bone remains.

#Syphilis.#--Syphilitic affections occur during the tertiary period of the disease, and usually implicate the frontal and parietal bones (Fig. 202). They are described in Volume I., p. 462.

#Tumours.#--_Osteoma_ of the skull has been described with diseases of bone (Volume I., p. 481).

_Sarcoma._--All forms of sarcoma are met with, implicating the bones of the skull. They may originate in the pericranium, in the diploe, or in the dura mater, and usually involve the bones of the vault. They sometimes occur in children (Fig. 203).

The tumour grows chiefly towards the surface, but it also tends to invade the cranial cavity, and may thus assume the shape of a dumb-bell. Its growth is usually rapid, and results in the formation of a diffuse soft swelling, which sometimes pulsates, and sooner or later fungates through the skin. On account of its rapid growth the tumour is liable to be mistaken for an abscess, and in some cases the nature of the disease is only discovered after making an exploratory incision, and finding that the finger passes through a softened area in the bone.

When the cranial cavity is encroached upon, signs of compression ensue. After the tumour has fungated, infective complications within the skull are liable to develop. In all cases the prognosis is extremely unfavourable.

If diagnosed sufficiently early, an attempt may be made to remove the tumour, but often the operation has to be abandoned, either on account of the haemorrhage which attends it, or because of the extent of the disease.

The bones of the skull may become the seat of _secondary growths_ by the direct spread of cancer from the soft parts, _e.g._ rodent cancer (Fig. 204), or by metastasis of cancer or sarcoma from distant parts of the body, or of thyreoid tumours. Metastatic cancer would appear to be conveyed by the blood stream; it may occur in a diffuse form--cancerous osteomalacia--softening the calvaria so that at the post-mortem examination it may be removed with the knife instead of the saw; or it occurs in a discrete or scattered form, and then the macerated skull presents a number of circular and oval perforations.