Of The Dura Mater Of The Spinal Cord

1. The fibrous investment, and the other membranes of the spinal cord, are but partially developed, or are not developed at all, in cases of acephalus, in -which, at the same time, the spinal cord is wanting (amyelia).

2. The principal deviation from the natural size and form of the dura mater is the saccular dilatation met with in partial spina bifida - hydrorachis, of which I shall have to speak hereafter.

3. Its continuity is broken not only by penetrating bodies from without, and by fragments of the vertebrae, when they are fractured and comminuted, - by either of which it may be wounded in various ways, - but also from other causes. Thus we find various openings in it: in cases of extensive spina bifida (atelomyelia of Béclard), it is deficient at its posterior part. It may be lacerated in the cervical region by the odontoid process of the axis, whenever, in consequence of inflammation and suppuration of the ligaments, and of caries, that vertebra is dislocated. Ulcerated openings form in it from the pressure of abscesses, and particularly of those abscesses which are connected with caries of the ribs and vertebrae, etc.

4. Diseases Of Its Texture

1. Inflammation

Inflammation of the spinal dura mater occurs as a consequence of accidental injuries, and is propagated from adjoining inflamed and suppurating tissues, such as ligaments and bone; but it does not arise from any other cause. Its characters are those of inflammation of fibrous tissue in general; and when it extends more deeply, it gives rise further to circumscribed exudation on the inner free surface of the membrane. If the conditions under which it originated do not destroy life too soon, either by the pressure of the swollen vertebrae on the spinal cord, by spontaneous dislocation of the vertebrae, and laceration of the cord, or otherwise, the inflammation may reach its natural terminations. In those cases in which the inflammation of the bone and the caries heal, the dura mater continues permanently thickened, and adherent to the bone, and even to the visceral layer of the arachnoid also. In other cases, the inflammation of the dura mater terminates in suppuration and perforating ulcer. It may thereupon extend, as a circumscribed inflammation, to the inner membranes, and to the cord itself, or may spread out into a general spinal meningitis.

2. Adventitious Growths

They are mainly confined to cancerous growths.

a. Cancer of the fibrous spinal membrane, known as fungus durce matris spinalis, resembles, in its general characters, the fungus of the dura mater of the brain. It may be a primary disease, or the membrane may degenerate secondarily in consequence of being involved in cancer of the vertebrae, and especially of the bodies of those bones. It generally grows exuberantly over a considerable extent of the surface of the membrane, either on its outer or inner side: and as, in the latter case, the arachnoid is destroyed by the advancing growth, the canal of the dura mater is sometimes entirely filled up. Not unfrequently, when it springs from the bones, it involves principally the fibrous sheaths of the nerves and their ganglia in the intervertebral foramina. More rarely it forms circumscribed tumors.

With regard to the form of the disease, it is most commonly the medullary. Its usual seat is the inferior dorsal, and the lumbar regions of the vertebral column.

b. Tuberculosis of the dura mater of the cord occurs in cases of tuberculous caries of the vertebrae, both in the form of an inflammation attended with tubercular exudation, and in that of tuberculous suppuration.

It is remarkable that no production of bone, such as occurs so commonly within the cranium, and is known in that situation as ossification of the dura mater, should ever be met with in the dura mater of the cord; or, at least, it is an extremely rare appearance. Its place is here occupied by the deposition of bone on the free inner layer of the spinal arachnoid.