2. Meningomyelocele, where some portion of the spinal cord proper is included within the sac;
3. Syringomyelocele, where the central canal of the cord is dilated into a cyst of some size, over which the structures of the cord proper are more or less thinly spread out, the whole being covered with the spinal dura.
The first form is by far the simplest and most amenable to treatment. The other forms are much more serious, and the third form is hopeless so far as operative surgery is concerned.
The greater proportion of these cases occur in the lumbar region, at least 70 per cent. being met with in the lower region of the spine, including the sacrum. It occurs occasionally in the neck and in the mid-dorsal region.
[Fig. 411] illustrates the general appearance of such a tumor. The opening of communication may be very small or may involve the arches of several vertebræ. So with the tumor itself, it may be small and almost imperceptible, or it may attain almost the size of a child’s head. The overlying skin is rarely absent; it is usually covered with a growth of hair, and its presence in the region of the spinous processes, coupled with the presence of any perceptible tumor, should cause suspicions of the so-called spina bifida occulta.
Fig. 411
Spina bifida. (Bradford.)
These tumors are situated in the middle line or very near to it, and are compressible in proportion to the thinness of their coverings. When small they can be collapsed by pressure, the same not infrequently causing pressure symptoms, as the fluid is forced into the cranial cavity, such as coughing, vomiting, vertigo, etc. If the fluid can be easily expressed from the sac the opening may be regarded as relatively large. If pressure makes no alteration in the size of the growth the case should then be regarded as one where the small original communication has been closed by natural processes. Some of these tumors have more or less of a pedicle and others are broadly sessile. The tendency is ever toward increase in size, being rapid or slow according to the thickness of the protecting membranes and the size of the opening. While spontaneous occlusion may occur there is practically no spontaneous repair of the bony defect. The surgeon should beware of a tumor of congenital origin situated in or near the middle line, anywhere from the root of the nose, over the head, and down to the tip of the coccyx. Such a tumor should be regarded with suspicion until shown to be harmless. Many cases of spina bifida are accompanied by other congenital defects, such as club-foot, or hydrocephalus. Symptoms may or may not be present. When present they will be of the paralytic type and affect those parts of the body below the level of the growth. They are due to the involvement of the cord or the nerves. The ever-present danger in such cases is of rupture with escape of the contents, with its proportionate reduction of intraspinal pressure, and the possibilities of infection, with rapid death from meningitis. Inasmuch as some of these cysts have such thin walls that transillumination is possible it will be seen how great may be this danger.