The tumor may thus appear in the pharynx, or in the inouth, or protrude through the splieno-maxillary fissure, or into the orbit, causing displacement of the eye.
The physical characteristics of the three forms of congenital tumor difTer according to the size of the opening in the skull and the nature of their con tents. Owing to possible error in diag nosis, all tumors of this kind should re ceive most careful physical examination, pressure upon it causes symptoms of cerebral compression, such as nausea, vomiting, irregular respiration, strabis mus, and even convulsions.
(b) Meningocele appears as a more uniformly round or oval pedunculated tumor, usually small at birth and subse quently increasing, more or less in size.
especially if any surgical interference should be contemplated.
(a) Encephalocele presents the small est tumor of the three, usually rounded or oval with a broad base, and having a pretty firm resistance to the touch.
It is translucent, fluctuates distinctly, does not pulsate, is made intense on the crying of the child, or during forced ex piratory efforts, and it is reducible upon pressure.
Sometimes the tumor is marked by a. median furrow, dividing it into two lateral halves. The tumor is opaque, does not fluctuate, has distinct pulsation synchronous with the heart's action, and (c) Hydrenceplaalocele presents the largest tumor of the three forms of this condition. The tumor is lobulatecl, pendulous, and more or less peduncu lated; and there is fluctuation, translu cency of parts of the tumor, according to the amount and location of the liquid contained within it, and usually absence of pulsation. The surface of the mass is covered with hair if the tumor is small, but if large the hair is only about its base, being absent over its fundus. It is liable to increase of size and to final rupt ure with rapid collapse or convulsions prior to death. Pressure does not pro duce the marked signs of cerebral com pression observed in cases of encephalo cele. In some cases some form of pa ralysis may also be present, with micro cephalus and hydrocephalus.
Differential Diagnosis.—Any of these conditions may possibly be confounded with cephalhmmatoma, serous or seba ceous cysts, abscesses, nmvi, and polypi.
Such mistakes having been made, it is most important that the most careful ex amination should precede any surgical interference; but, with ordinary care and attention to the physical characteristics of these forms of hernia cerebri, mistakes of this kind should never occur. The diagnosis, therefore, is usually a simple matter, and is readily made -upon careful examination of the tumor. The fact that tbese conditions usually occur in the median line, that meningocelc is redu cible, that encephalocele is attended by signs of cerebral compression when press ure is madc upon the tumor, and pul sates distinctly, and that all of them are made tense upon forced expiration, should separate them from any of the above conditions. In many of the cases the edges of the bony opening through which the protrusion occurs can be felt by palpation, with partial reduction by pressure. Hydrencephalocele can hardly be confounded with any of the above affections, owing to its large size, its pendulous, pedunculated, and lobulated conformation, with semitranslucency, and its strictly congenital history. All of these cases are apt to be associated with other deformities, and some form of paralysis is frequently present in cases of hydrencephalocele.
Etiology and Pathology.—The excit ing causes of these three forms of con genital malformations are practically un known. It is probable that injury to the mother may account for some of the cases. The influence of certain maternal impressions may operate here, by in ducing an arrest of development.
The most widely accepted view of the pathology of these states is that they are all due to a primary intra-nterine hydro cephalus, and that the resultant in creased intracranial pressure during the closure of the cranial cavity causes a por tion of the intracranial contents to be forced outside, an aperture being main tained. Other possible causes are am niotic adhesions to the scalp of the fcetus, and arrest of development in the bones concerned. This arrest of bony develop ment may be caused by amniotic adhe sions. However, the fact that these pro trusions occur in the median line favors hydrocephalus as the causative condi tion.