The Surgery of the Skull and Brain

by Louis Bathe Rawling

At the lower portion of the exposed dura mater, a crucial incision is made through the dura mater and a blunt-pointed trocar and cannula introduced at the centre of the exposed brain, all visible vessels being avoided. The diagnosis is now confirmed—by the withdrawal of the trocar and the escape of cerebro-spinal fluid.

Fig. 27. The Conversion of Hydrocephalus internus into Cephalocele.

By the introduction of a bundle of horsehair or catgut, passed through the cannula so as to project into the ventricular cavity, and, after the withdrawal of the cannula, tucked, with respect to the proximal ends, into the subdural, extra-dural, or subaponeurotic spaces, it is obvious that drainage may be established between the ventricles and the other regions. Experience showed, however, that drainage into the subaponeurotic space usually converted the condition of hydrocephalus into one of cephalocele (see [Fig. 27]), the fluid collecting as a localized fluid tumour over the region of exploration, whilst extra-dural drains did not permit of sufficiently rapid reabsorption of fluid. Subdural drainage gave the best results, the cerebro-spinal fluid being brought into relation with the pia-arachnoid meshwork of vessels. It would, of course, be infinitely preferable if the ventricular fluid could be brought into direct relation with the veins of the subarachnoid space, for the cerebro-spinal tension and venous pressure are equal, and all excess of cerebro-spinal fluid would be absorbed as soon as it is formed. This course is, however, impossible to carry out. We have, therefore, to rest content with less direct contact, drainage into the subdural space. This ventricular-subdural drainage, as obtained by horsehair, catgut, and silk, apparently leads to but temporary benefit, probably owing to falling together of the brain substance and obliteration of the adventitious passage.

Silver tubes and bone tubes have been utilized, but the results are sometimes disappointing. In one of my recent cases the two halves of a bone tube were utilized. The tube was cut across in an oblique manner at about its centre, the two parts set at right angles to one another and sewn together with silk. One arm is introduced into the ventricle, the other tucked underneath the dura mater. The child improved considerably, but the method is not altogether satisfactory and by no means easy of application. In another case I utilized strands of silver wire. The depth of brain-tissue necessary to reach the ventricular cavity was measured, and two or three strands of wire introduced so as to project well into that space, then steadied with forceps whilst the proximal ends were bent at right angles to the surface of the brain and tucked underneath the dura mater. The method was unsatisfactory.

Tubular drainage is not essential, for the fluid escapes from the ventricle as much alongside the tube as through its lumen. Still, I believe that tubular drainage is preferable to other methods, and, realizing the difficulty of introducing a right-angled tube—one arm to project into the ventricle, the other to lie beneath the dura mater—Messrs. Arnold & Son are now making for me small and light right-angled silver tubes so constructed that each limb can be inserted independently, after which they can be locked together. This method appears to overcome many of the difficulties previously encountered. The tube is inserted after the formation of the osteoplastic flap, as described above. The four dural flaps are then united, preferably by cross union of their apices, the bone-flap is replaced, and the scalp-flap sewn accurately into position. Collodion gauze, applied to the wound, aids in the prevention of cerebro-spinal escape.

The scalp and bone-flaps are framed, and the dural incision carried out low down, so as to make the opening to the brain as valvular as possible. All these precautions are taken to avoid leakage of cerebro-spinal fluid, a most troublesome complication—adding to the risk of infection and often resulting in an acute eczematous condition of the surrounding skin.

By this method it is hoped that a permanent fistulous communication will be formed between the lateral ventricle and the subdural space.

Ventriculo-abdominal drainage.

The following method of drainage has been devised by Cushing: ‘It having been established that the ventricle can be emptied by the lumbar route, and that the withdrawal of fluid is not prejudicial to the child’s well-being, the following procedure is carried out. A laparotomy is performed; the posterior layer of peritoneum to the left of the rectum is split; the body of the fifth lumbar vertebra, just under the bifurcation of the vessels is exposed; the bone is trephined and one-half (the female portion) of a silver cannula, exactly the size of the trephine, is inserted and held in position. The child is then turned on his face and a laminectomy performed; the subarachnoid space is opened, the strands of the cauda separated, and the posterior half (male portion) of the cannula is invaginated, so that it locks into the portion inserted anteriorly. Both wounds are then closed. The fluid for a time finds its way into the peritoneal cavity, but ultimately into the retro-peritoneal space whence it is taken up by the receptaculum chyli, as experimental observations have shown.’