A system of practical medicine. By American authors. Vol. 5

by Unknown

The size of a spina bifida varies from that of a walnut to that of a child's head, or even larger: in some rare instances, such as those recorded by Lezelius and Richard, the whole spinal column has been cleft, and the tumor has extended from nucha to sacrum; but cases of this kind seldom come under the surgeon's observation, as children with such extensive deformity usually perish shortly after birth. The shape of the swelling is rounded, or more often oval; it is commonly sessile, but occasionally pedunculated; and it is sometimes lobulated, the lobules being separated by more or less distinct sulci. The skin covering the tumor is in some cases normal, with more or less fat in the subcutaneous connective tissue, but more often thin, tightly stretched, red, shining, and occasionally ulcerated; more rarely it is thickened and leathery, as in a case referred to by Sir Prescott Hewett. Sometimes a navel-like depression is found at some part of the surface, corresponding, as pointed out by Follin and Duplay, and by Erb, to the place of attachment, on the interior of the sac, of the terminal extremity of the spinal cord. The cutaneous investment is sometimes altogether wanting, the spinal dura mater itself forming the external covering of the tumor. It is in these cases especially that ulceration and rupture are apt to occur.

Spinæ bifidæ are usually soft and fluctuating, and occasionally partially reducible; their tension and elasticity are increased when the child is in the upright position or during the acts of expiration and crying, and are diminished during inspiration or when the child is laid upon its face. When the part is relaxed a bony prominence can be felt on either side, and the aperture in the vertebral column can be more or less distinctly outlined. The swelling is apt to be painful on pressure. If the tumor is of moderate size and covered with healthy skin, there are usually no constitutional symptoms, and, even where ulceration and rupture occur, the opening may heal and a spontaneous cure may possibly ensue. More often, as the tumor increases in bulk—or at any time if pressure be made upon it—various nervous symptoms are observed: drowsiness, muscular twitchings, convulsions, and often paraplegia and paralysis of the sphincters. Rupture is usually followed by the development of spinal meningitis, or may prove directly the cause of death by the loss of cerebro-spinal fluid which it causes; in other instances, however, if the rupture be a small one, healing may occur (as already mentioned) or a fistulous opening may persist; in rare cases the fluid may escape by a process of transudation without rupture, as in an example recorded by Laborie.

As may be inferred from what has already been said, the course of spina bifida is usually rapid and toward a fatal termination. In some instances, however, as in cases observed by Holmes, and more recently by Lithgow, spontaneous recovery has followed the obliteration of the channel which unites the sac with the cavity of the spinal membranes; and in other instances, without a cure having been effected, life has been prolonged for very many years. Thus, Behrend reports a case in which a patient with spina bifida lived to the age of fifty, and Holmes refers to another in which death resulted from an independent disease at the age of forty-three. But a still more remarkable case was recorded by Callender, the patient in this instance having reached the age of seventy-four.

PATHOLOGY AND MORBID ANATOMY.—The most important points for consideration in respect to the anatomy of spina bifida are the relations which the spinal cord and spinal nerves bear to the sac, and the nature of the contained fluid. It is ordinarily said that the spinal cord itself commonly enters the sac of a spina bifida—the report of the London Clinical Society's committee gives the proportion of cases in which it does so at 63 per cent.—and Holmes figures a specimen from the museum of St. George's Hospital, London, in which this condition is obviously present; on the other hand, Mayo-Robson in eight operations only once found the cord implicated; and the late John B. S. Jackson of Boston—whose name will be recognized as one of high authority in regard to all questions of morbid anatomy—once assured me that he had made very many dissections of spinæ bifidæ, and that he had invariably found that the cord stopped short of the sac, and that only the nerves entered the latter: this, as negative evidence, cannot of course contravene such positive evidence as that of the specimen referred to by Holmes, but it would seem to show that the condition was a less common one than is generally supposed, and that in at least a fair proportion of cases the cord itself did not form part of the sac contents. This remark applies especially to those cases in which the fluid is accumulated in the subarachnoid space, and in which, as pointed out by Sir P. Hewett, the cauda equina or spinal nerves are pushed by the vis a tergo into the sac; but when the dropsical effusion occupies the central canal of the cord, this is apt to be flattened and spread out like a thin lining to the sac, just as the brain is spread over the inner wall of the skull in cases of internal hydrocephalus; and, on the other hand, when the accumulated fluid fills the cavity of the arachnoid the cord is apt to be pushed forward, and the sac may be entirely devoid of all nerve-structures. Such, too, according to Giraldès, is the case in spina bifida of the cervico-dorsal region.

The committee of the London Clinical Society classify cases of spina bifida in three divisions: (1) Those in which the membranes only protrude (spinal meningocele); (2) those in which the protrusion involves both the cord and membranes (meningo-myelocele); and (3) those in which the central canal of the cord itself forms the cavity of the sac (syringo-myelocele). The last variety is the rarest, as the second is the most common. In meningo-myeloceles the spinal cord with its central canal is continued within the median, vertical portion of the sac, and at this part there is no covering of true skin; the nerve-roots which traverse the sac arise from this intramural portion of the central nervous system.

Humphry of Cambridge, England, makes a somewhat similar classification of spinæ bifidæ, recognizing as the most common variety the hydrorachis externa anterior, in which the fluid occupies the subarachnoid space in front of the spinal cord, and in which “the cord and the nerves are stretched backwards and outwards upon the sac, and are there confluent, together with the arachnoid, pia mater, and dura mater, or their representatives, in the thin membrane which forms the hindmost part of the wall of the sac;” rarer forms are the hydro-meningocele, or hydrorachis externa posterior, in which the fluid accumulates behind the cord, which does not enter the sac, and the hydro-myelocele or hydrorachis interna, in which the fluid occupies the central spinal canal.

The theory which, according to the Clinical Society's committee, best explains the pathological anatomy of spina bifida is that which assumes a primary defect of development of the mesoblast from which the structures closing in the vertebral furrow are developed.

The fluid of spina bifida appears to be identical in character with the cerebro-spinal fluid. Bostock found that it was very slightly clouded by the application of heat, and that it contained, in 100 parts, 97.8 of water, 1.0 of chloride of sodium, 0.5 of albumen, 0.5 of mucus, 0.2 of gelatin, and some traces of lime. Five specimens more recently analyzed by Hoppe-Seyler gave an average of 98.8 parts water, 0.15 parts proteids, and 1.06 extractives and salts. Turner found a reaction somewhat similar to that of grape-sugar, as had been previously found by Bussy and Deschamps in cerebro-spinal fluid itself, but in two specimens analyzed by Noad for Holmes it was at least very doubtful whether sugar was actually present. “The first specimen was found to be completely neutral; its specific gravity was 1.0077; it contained phosphates, but no reaction could be obtained resembling that of sugar. The second specimen ... did give a reaction with copper like that of sugar, but no trace of fermentation could be obtained.” Three analyses, however, made by Halliburton for the London Clinical Society's committee showed uniformly a decided trace of sugar, with a diminution in the quantity of proteids, which appeared to consist entirely of globulin.

In some cases the sac of a spina bifida contains, besides nerve-structures and cerebro-spinal fluid, both fibrous and fatty tissues.

DIAGNOSIS.—Ordinary fatty tumors have been mistaken for spinæ bifidæ, but such an error could only be committed through carelessness: more difficult is the diagnosis from certain forms of congenital cyst, occupying the median line of the back, and still more difficult the diagnosis from the several affections known as false spina bifida. In the former case the distinction might be made by noting the irreducibility, constant shape, and unchanging tenseness of the cyst, and perhaps, as suggested by T. Smith, by tracing the line of spinous processes beneath it; some information, too, might perhaps be gained by chemical examination of the fluid obtained by puncture. Under the name of false spina bifida Holmes includes three distinct conditions: these are—(1) a true spina bifida, in which the connection with the spinal membranes has in some way been obliterated, the sac then communicating with the vertebral canal, but not with the theca; (2) a congenital, cystic, or fatty tumor, taking its origin within the vertebral canal, and projecting through an opening caused by a gap in the laminæ; and (3) a tumor containing fœtal remains, and properly regarded as an example of included fœtation. In any of these cases a positive diagnosis might be impossible, and the probable nature of the tumor could only be inferred by noting the absence of one or more of the characteristic symptoms of true spina bifida.