Meningocystocele results from a local dilatation of the central canal, occurring after the spinal marrow is closed, when there is an opening in the bone through which the dorsal portion of the spinal marrow is protruded. In this form of spina bifida the external cutane ous coverings are closed, covering the arca medullarascidosa, which is adherent to the pia that has also protruded and takes the place of the bulging posterior pOrti011 of the spinal marrow-. The hernial sac there fore represents the cystic and dilatated central canal and communicates directly with the cavities of the afferent and efferent portions of the spinal marrow. -As the ventral portion of the spinal marrow is more or less completely preserved, the motor nerves which take their origin in that portion are normally developed, and palsies of the extremities are less commonly observed in this form of spina bifida. Asso ciation with hydrocephalus is frequent.
ilecingocele is the rarest form of spina bifida. The spinal marrow is closed and there is merely a collection of fluid on the dorsal side of the spinal cord with a saccular protrusion of the pia. The meningocele contains no nerves, or at most a few fibres of the cauda equina may be forced outward by the tion of fluid. Meningocele is usually pedunculated, and it may attain the size of a child's head. The tumor is most frequently situated over the sacrum. Palsies practically do not occur in this form of spina bifida. The frequent association of meningocele with other forms of spina bifida and. more than anything else, the extreme difficulty of recognizing this form of spinal hernia except at the autopsy, renders it doubtful whether all the conditions described under this head are really simple meningoceles. 'Mon Bergmann denies absolutely that meningocele occurs as an isolated affe8tion. In all forms of spina bifida the dura mater is open on its posterior surface and becomes merged in the walls of the hernial sac. Differentiation of the three forms of spina bifida is most important from the standpoint of therapeutics, but unfortunately exceedingly difficult. In quite typical cases the following diagnostic points are of service. 1Iyelocele has a broad, sessile base. the outer covering exhibiting the above-mentioned division into three layers; a large opening in the bone is present, through which firmer constituents can be felt. It is practically impossible to replace the tumor, and severe motor and sensory palsies cmcluding paralysis of the rectum and bladder) are observed. Meningocek is often pedunculated. The bone cleft is smaller; the tumor is perfectly transparent on lateral trans-illumination, and no solid constituent can be felt. The covering consists of normal skin and the condition is not
accompanied by palsies. Ai yelocystocele also has a broad, sessile base; is covered by normal, albeit much attenuated, skin; masses of solid tissue can be felt and, finally, there are sometimes sensory, but rarely motor, disturbances.
In very rare eases hernia of the spinal marrow occurs in the an terior wall of the vertebral column (spina bifida anterior).
It appears from the above description that the symptoms of spina bifida may be extremely variable. We shall here confine ourselves to those which are observed in myelocele, situated in the lumbosacral region, the most frequent as well as the gravest of the various forms, and concerning which expert opinion is very frequently sought, even in the case of newborn infants. In order to gain a proper understanding of this disturbance we must bear in mind the innervation, which is shown in the following scheme.
With regard to the sensory innervation.it will suffice to say that the skin of the greater portion of the upper and inner side of the leg is sup plied by the second, third and fourth lumbar nerves; that of the foot and lower side of the leg by the fifth lumbar and second sacral nerves; that of the popliteal space and the posterior aspect of the thigh by the second sacral nerve; that of the perineum, the anus, the mucous mem brane of the bladder, the buttocks and the inner side of the thigh by the third and fourth sacral nerves.
It appears from the above that when the spina bifida is situated in the lower lumbar or in the sacral portion of the spinal cord, complete motor (except the iliopsoas) and sensory paralysis of the kgs, rectum, bladder and perinea! muscles must be present. In addition to the com plete atonic paralysis of the legs, this form of palsy is distinguished by obliteration of the anal fold, or even by a funnel-shaped protrusion of the anal region (paralysis of the levator ani and sphincter ani). At the same time the thighs are flexed at the hip-joint at a right, or even an acute angle because the iliopsoas (see scheme) is usually intact. Direct prolapse of the rectum and uterus has also been occasionally observed. Owing to the complete loss of sensation in the skin, so that the infants do not cry when they soil themselves, and probably also on account of trophic changes in the skin deep ulcers often develop in the skin of the buttocks. in the genital region and on the inner aspect of the thigh. All reflexes are completely absent in the legs, although the electric irritability of the mus cles, strangely enough, may be preserved. Club-foot is usually present.