Previous to withdrawal of the evacuator, a small rubber or cigarette drainage-tube is introduced, projecting into the abscess cavity at the one end, and brought out through the scalp-flap at the other. It is advisable to stitch the tube in position.
The dural flaps are replaced in their proper position, but no attempt is made at sewing them together. The scalp-flap is sutured with the aid of a few salmon-gut stitches and the dressings applied. The tube may be shortened daily, and dispensed with after seven to ten days, according to the progress of the case.
Trephining for cerebellar abscess. The abscess usually occupies the antero-external aspect of the lateral lobe of the cerebellum. It can be drained with advantage below the level of the lateral sinus and behind the posterior border of the mastoid process.
The patient should be in the semi-prone position, the head as forwardly flexed as the administration of the anæsthetic allows.
The incision starts below the external occipital protuberance, and, following the line of the occipital crest, curves downwards along the posterior border of the mastoid process, terminating at the apex of that prominence. The cutaneo-muscular flap is turned down, every precaution being taken to diminish hæmorrhage, insomuch as severe bleeding may take place from occipital vessels, and from the mastoid and other emissary veins. Hæmorrhage from the former source is controlled with forceps, that from the emissary veins by the introduction of the end of a blunt probe into the orifice of the foramen. More permanent occlusion can be obtained by plugging the foramen with catgut, with a sterilized wooden match, or by means of special ivory, bone, and wooden pegs.
The trephine is applied in such a manner that its circle falls well below the lower level of the lateral sinus and behind the mastoid process. After removal of the disk, the dura mater is cautiously opened by crucial incision and the evacuating instrument introduced, the cerebellum being explored in the forward and slightly inward direction—towards the posterior aspect of the petrous bone. The abscess should be reached within 11⁄2 inches from the opening in the bone. A drainage tube is introduced, stitched in position, in the manner described when dealing with temporo-sphenoidal abscess. This tube should be shortened daily and dispensed with after seven to ten days.
Trephining for frontal abscess. An abscess of the frontal lobe is generally situated so far back, and connected with the source of the trouble (the frontal sinus) by so long a ‘stalk’ of infection, that considerable difficulty may be experienced in attempting drainage from the frontal or nasal regions. Moreover, operations conducted through the frontal region are apt to result in considerable deformity. The operation may therefore be conducted with advantage from the temporo-frontal region. In this situation, the bone is thin, the operation can be conducted between the split fibres of the temporal muscle, excellent drainage is supplied, and the scar is inconspicuous.
For a general description of the intermusculo-temporal operation, the reader is referred to [p. 121]. In this instance, the field of operation is shifted further forwards, otherwise the details are very similar. The skin incision commences above and in front of the external angular frontal process, curves along the temporal crest, and terminates well in front of the ear. The temporal fascia is turned down and the muscle split in the general direction of its fibres, and well retracted on either side. The trephine is applied, the dura mater incised, and the abscess evacuated and drained in the manner previously described. The tube may be removed after seven to ten days.
The treatment of a chronic encapsuled abscess, wherever situated. In attempting to evacuate a chronic encapsuled abscess, both the trocar and cannula and the evacuator merely impinge against, and tend to push aside, the dense enclosing wall of the abscess cavity. When such obstruction is suspected, a director should be introduced in the direction of the abscess, and the brain explored till the resistance of the abscess-wall is encountered. With the aid of two narrow spatulæ, or other suitable instrument, the passage through the brain is gently enlarged till the wall of the abscess becomes visible. The margins of the passage through the brain are gently retracted and the abscess-wall freely incised with the knife. After the evacuation of the pus, a drainage tube can be introduced, but, as such a method seldom permits of a permanent cure—the abscess filling up again as soon as the tube is withdrawn—it is generally advisable to attempt the entire removal of the abscess-wall. The cut edges of the capsular incision are seized with narrow-bladed forceps, gentle traction applied, and the surrounding brain substance carefully peeled away. As a rule, there is no great difficulty attendant on this process and the hæmorrhage is seldom severe. The cavity that remains in the brain substance is lightly packed with gauze, this packing being allowed to remain for twenty-four to thirty-six hours, after which it is withdrawn and a little fresh gauze introduced, if necessary. The cavity fills up with extraordinary rapidity, mainly as a result of the expansion and falling together of the surrounding brain (see [Figs. 86 and 86a]).