The Surgery of the Skull and Brain

by Louis Bathe Rawling

CEPHALOCELES

The term ‘Cephalocele’ has been applied to all those tumours which project through a gap or deficiency in the bones of the vault and base of the skull. The tumour may be congenital or traumatic in origin: the membranes of the brain may alone protrude (meningocele), or the tumour may be composed of normal or altered brain-substance: all the varying conditions, however, are included under one term—cephalocele. Congenital and traumatic cephaloceles differ, however, so markedly from one another, both with regard to their pathology and treatment, that they must be considered separately.

Congenital cephaloceles.

Billroth and the late Professor von Bergmann were the first to narrate cases in which this deformity was present, Lyssenkow[4] added much to the previous records, and de Quèrvain,[5] by prolonged researches, drew further attention to the subject.

Lyssenkow divided the congenital variety into two main groups—exencephaly and cephalocele—the former resulting from a general error in development (the ‘Acrania’ of Muscatelle), the latter a partial or local developmental failure. In exencephaly there is an extensive gap in the vault of the skull, the remainder of the skull being microcephalic in nature, the brain projecting outwards in a varying degree, and the ventricular spaces distended with fluid. In cephaloceles the hole in the skull is usually circumscribed, although the sutures may be widely separated and the ventricles distended with fluid, yet both skull and brain may be normally developed in all other respects.

Exencephaly

presents but few points of surgical interest, insomuch as the condition is barely compatible with life.

Cephaloceles

occupy a very different position. The condition is by no means confined to man, and many instances are recorded as occurring throughout the animal kingdom. Norsa Gurrieri,[6] for instance, records a case occurring in the embryo of Mus decumanus vel albinus. The same writer insists that the developmental error involves bones of either cartilaginous or membranous origin, and that the atrophic condition of the bone is the primary cause and the ectopia of the brain a secondary result.

Lyssenkow,[7] after careful investigation of tumours removed by operation and after death, found scattered nerve-fibres, fat-cells, striated muscle and vessels—the products, therefore, of both ectoderm and mesoderm. He also observed the frequent occurrence of an intimate union or fusion between the cephalocele and the overlying integument, and, in consequence, the theory was formulated that the greater number of cephaloceles were in reality cephalomata or true teratoid tumours.

It would appear, therefore, that a cephalocele results from the incomplete cutting off of the neural canal in the head region of the embryo from the overlying epiblast, with consequent fusion between the primary neural tube (from which the brain is developed) with the primordial mesoblastic membranous cranium (from which the membranes are developed), and with the overlying epiblastic layer (from which the epidermal portion of the scalp is developed). In consequence of this localized fusion of layers, the outer dermic coat (from which the membranous skull is developed) fails to form. Bony defects therefore exist through which brain-matter protrudes, the projecting portion often being intimately attached to the skin, and containing not only epiblastic elements, but also mesoblastic tissue from irregular occlusion of the same. The mesoblastic involvement is proved by the presence in the tumour of muscle tissue, vessels, &c.

Position of the tumour.

The tumour may project through the vault or base of the skull. In the former case, it is almost invariably situated in close relation to the middle line of the skull, from nasion to below the inion.

Fig. 20. An Occipital Cephalocele. (For further description, see text.)

1. Occipital cephaloceles—the commonest variety—occupy, anatomically, two positions (1) between the two lower segments of the occipital bone (inferior occipital cephaloceles), often involving the foramen magnum and sometimes complicated by a condition of cervical spina bifida, and (2) between the two upper segments of the occipital bone (superior occipital cephaloceles), occasionally involving the posterior fontanelle.

The tumour may possess a broad base or may be definitely pedunculated. In the former instance the gap in the bone may be of considerable size and the margins everted: in the latter case, the hole may be quite small.

The deformity is frequently associated with other congenital defects—hydrocephalus, microcephalus, spina bifida, hare lip, hernia, and talipes.

2. Sincipital cephaloceles occur next in order of frequency. The tumour projects between the nasal bones and the nasal process of the superior maxilla (naso-frontal), between the nasal process of the maxilla and the orbital plates of the ethmoid (naso-ethmoidal), or between the nasal bones (nasal).

Fig. 21. A Cephalocele over the Anterior Fontanelle.
(For further description, see text.)

3. More rarely, the tumour overlies the anterior or posterior fontanelle. A case of this nature is depicted in [Fig. 21], the tumour, situated over the anterior fontanelle, bulging over the temporal and frontal regions to a remarkable extent.

4. Basal cephaloceles protrude through the cartilaginous base of the skull, either through the cribriform plate of the ethmoid, between the pre- and basi-sphenoid, or between the basi-sphenoid and basi-occiput, often projecting as a polypoid growth in the nose or naso-pharynx.

An interesting case of basal hernia was reported by von Mayer.[8] The child, 3 days old, was admitted with a tumour projecting into the right nostril, covered with mucous membrane, translucent, encrusted with scabs, pedunculated, and closely resembling a nasal polypus. The possibilities were fully recognized and all necessary precautions taken. The right half of the nose was turned back as a flap, the tumour isolated, ligatured, and removed. Death occurred after six weeks. An oval hole was found in the left half of the cribriform plate through which the dura mater projected and to the margins of which the membrane was firmly adherent. The pedicle contained ganglion-cells and nerve-fibres, whilst the parts removed showed, from without inwards, mucous membrane, dura mater, arachnoid, pia, and glial tissue.

Size, structure, and contents.

Sincipital cephaloceles are usually quite small, but the occipital variety and those situated in the region of the anterior fontanelle frequently attain a great size (see [Figs. 20]-[22]).

Fig. 22. An Occipital Cephalocele. (For further description, see text.)

It is not always possible to determine whether the tumour consists of a mere outward protrusion of membranes (meningocele), or whether brain-matter enters into the formation of the tumour (meningo-encephalocele). Fluctuation, translucency, and pulsation are all points to be investigated. All these features are, however, deceptive, and several cases are on record in which operative measures were carried out under the impression that the surgeon had to deal with a pure meningocele, and in which it was afterwards found that brain-matter formed the basis of the swelling.

When the tumour is large, the skin adherent, when no pedicle is present, when fluctuation and pulsation are absent, and when the tumour is of firm consistency, then it is practically certain that brain-matter shares largely in the formation of the tumour. On the other hand, it is not unusual to find that the brain projects markedly outwards without resulting in any symptoms of brain irritation: fluctuation and pulsation are also not infallible signs, since the brain may occupy the base of the tumour, ‘corking-up’ the gap in the bone, or the brain may be so thinned by ventricular distension that a mere shell of cerebral matter lies beneath the scalp-covering.

Looking at the question from all points of view, it may be accepted that most cephaloceles contain either true brain-matter or the mixed epiblastic and mesoblastic elements described by Lyssenkow.

The following case serves to illustrate some of these facts:[9]—

The child was 3 months old, and presented a tumour, the size of an orange, situated between the occipital protuberance and the nape of the neck. The mass was pedunculated, the stalk being about the size of a four-shilling piece in diameter. It was soft, translucent, irreducible, and swelled up on coughing. An attempt at removal was carried out, and, after incising the outermost layers, three ounces of cerebro-spinal fluid escaped. A second tumour was then found occupying the base of the swelling. This was also punctured, more fluid escaping. Both sacs were cut away and the wound sewn up. Death occurred on the third day, preceded by convulsions, retraction of the head and neck, and high fever. The autopsy showed that the fontanelles were widely open, the anterior measuring 4 inches from side to side and 2¹⁄₂ from before backwards. The bones of the vault were markedly thinned. In the subdural space there was a quantity of fluid, and the cerebral substance was soft and diffluent, the convolutions flattened, and the ventricles distended. There was a broad gap in the occipital bone, extending downwards into the foramen magnum, and in this situation the cerebellum had bulged backwards into the protruding mass. (See [Fig. 22]).

For differential diagnosis, see [p. 57].

Treatment.

In considering the question of treatment, the late Professor von Bergmann[10] divided the cases into two groups:—

1. Inoperable cases. When associated with premature synostosis and microcephaly.

When associated with hydrocephalus or marked deformity.

When the tumour is situated below the occipital protuberance.

2. Operable cases. Limited protrusions with none of the above defects and disadvantages.

This classification undoubtedly forms a practical basis on which to estimate the feasibility of operative measures, and it would appear that sincipital and small occipital cephaloceles are the only cases that come within the realms of operative treatment. In estimating the possibility of operation, however, due consideration must be paid to the fact that, in the very great majority of cases, the tumour tends to increase in size, the bones become further thinned, the margins of the gap more everted, and the development of the brain suffers correspondingly. Again, in spite of the fact that some few cases have survived to adult age, yet it is the general rule for the patient to die within a few weeks or months of birth. For desperate ills, corresponding measures must be undertaken, and in the consideration of the more serious cases the surgeon should be biased in favour of operation unless the general condition of the child shows clearly that no success is possible. The best results have been attained in cases of pure meningocele.

Operation.

The unhealthy condition of the overlying integument, especially at the apex of the tumour, prohibits any extensive preparatory cleansing, this process being carried out for the most part when the child is under the anæsthetic.

Scalp-flaps are framed from the region of the base of the tumour, advantage being taken of the more healthy parts. These flaps must be so sized and framed that accurate approximation and complete covering to the gap will be attained at the termination of the operation. The flaps are dissected back to their base. The pedicle of the tumour is defined and an endeavour made to detach it completely from the margins of the osseous defect. This is often a matter requiring considerable patience. The sac of the tumour should then be tapped with trocar and cannula, and the fluid contents allowed to escape slowly, after which the opening into the sac is enlarged and the membranes slit up towards the base of the protrusion.

When dealing with a pure meningocele, the membranous protrusion is cut away in such a manner that sufficient tissue is left to allow of closure of the dural gap. This closure can be carried out either by means of a purse-string suture or by the union of two lateral flaps. In either case, accurate approximation is essential in order to prevent as far as possible the further escape of cerebro-spinal fluid.

If the sac should contain an irregular mass of neuroblastic and mesoblastic tissue, apparently not true cerebral or cerebellar substance, this material can be dissected from the membranous sac, ligatured at its base, and freely cut away.

If the sac should contain true brain substance, the possibility of excision can be raised. In the cerebellar region such measures are contra-indicated, and the surgeon must remain content with an attempt at replacing the cerebellar substance within the cranial cavity. This attempt at reposition will be aided by elevation of the head and, occasionally, by lumbar puncture. If the protrusion corresponds to a region which has no known important function, it may be ligatured and cut away flush with the surface of the gap. Hæmorrhage may be considerable, but can be controlled by ligature, pressure, and irrigation with hot water at a temperature between 110 and 115 degrees Fahrenheit. The degree of shock attendant on the operation may be severe, necessitating the most complete attention to preliminary, operative, and post-operative details (see [Chap. I]).

To remedy the defect of the bone Lyssenkow recommends an osteoplastic operation, a flap composed of pericranium, together with the external table of the skull, being framed from the bone above the defect.

The flap is then turned down in such a way that the pericranial surface faces towards the dura, and the fragment is suspended by the continuity of the pericranium. He reports 72 cases so treated, with 37 recoveries and 35 deaths.

König and von Bergmann oppose this osteoplastic operation on the ground that the extreme thinness of the bone seldom permits of the necessary splitting off of the external table of the skull, and that, even when such a course is feasible, the fragment undergoes necrosis.

Transplantation of decalcified and calcined bone, silver and celluloid plates, have all been tried, with no great amount of success. Ssamoylenko proposes paraffin and vaseline injections, especially for the sincipital variety of cephalocele.

When the surrounding bone is of such a nature that it is possible to form an osteoplastic flap, that course should be adopted. Under other circumstances, it would appear preferable to postpone any attempt to close in or protect the gap in the bone in the hope that nature will remedy the defect in part, the surgeon stepping in at a later date with one of the measures advocated for the protection of gaps in the skull (see [p. 196]).