After having exposed the sinus as freely as possible, the ‘bridge’ of bone separating it from the outer wall of the jugular foramen is removed in small pieces by nipping it away with narrow biting forceps until the jugular bulb is exposed from its outer surface. The facial nerve should not be injured, as it lies in front and external to the portion of the bone to be removed.
In performing the later stages of the operation, the patient’s head should be turned well over to the opposite side in order to get a good view of the parts lying behind and beneath the mastoid process; and in tracking the sinus downwards, the probe should be used carefully in order to try and define the exact position of the jugular fossa.
Piffl’s operation. Owing to the anatomical difficulty of reaching the jugular bulb by following the sigmoid sinus downwards, especially in those cases in which the sinus lies far forwards and in which, at the same time, there is a very well-developed jugular fossa, Piffl recommends exposure of the jugular bulb from above through the auditory canal. The object of this method is to prevent injury to the facial nerve, which he states is almost certain to occur in Grunert’s operation, if carried out in cases such as those just mentioned.
After the complete mastoid operation has been performed, the skin incision is extended downwards and forwards in order that the soft tissues may be freed from the floor and anterior surface of the bony portion of the auditory canal as far forward as the Glaserian fissure. The soft tissues are pulled forward with a blunt hook to give sufficient room. The lower portion of the tip of the mastoid is removed by means of the gouge, as far as can be done without injuring the facial nerve, which in this operation is pulled backwards with the soft tissues at the posterior inferior margin of the wound. The lower bony margin of the auditory canal, now freely exposed, is removed by means of a pair of fine biting forceps until the floor of the tympanic cavity is reached. If there be not sufficient room, the bone may be clipped away as far as the styloid process, which also may be removed by bone-forceps after the muscles attached to it have been dissected off.
In freeing the styloid process, its posterior surface must be approached with caution for fear of injuring the facial nerve, which here lies in close connexion with it. In the front of the wound the capsule of the temporo-maxillary joint may be exposed, but must not be interfered with.
After removal of the styloid process, the uppermost portion of the external jugular vein should be seen emerging from the jugular fossa. This is followed upwards by careful removal of the bone between it and the floor of the auditory canal and tympanic cavity, until the jugular bulb is brought into view. This part of the operation must be proceeded with very cautiously, the bone being nibbled away in small fragments with gouge forceps which are of sufficient strength to nip through the bone without having to wrench it away. The amount of bone to be removed and the difficulty of the operation depend largely on the anatomical condition found.
Whether Grunert’s or Piffl’s operation has been employed, the operation may be completed either by incising the outer wall of the sinus and jugular bulb, then curetting out the thrombus, and finally washing through the lower portion of the vein from above downwards, or by the more radical method of also exposing the upper portion of the jugular vein throughout its whole length. To do this the post-aural incision is continued downwards until it joins the one previously made in the neck. To obtain room, the neck must be somewhat extended and the jaw pulled well forward and the sterno-mastoid muscle backwards. The jugular vein is then dissected upwards towards the bulb.
The nearer the jugular fossa is approached the deeper and more difficult becomes the exposure of the vein. Passing in front of it may be found the stylo-pharyngeal, stylo-hyoid, and digastric muscles. In Grunert’s operation they need not be cut through as the vein will lie posterior to them. In Piffl’s operation these muscles probably have been already reflected forward, after removal of the styloid process.
Particular care must be taken not to injure the nerve trunks, which are in such close relationship with the vein. Lying immediately behind the vein is the vagus nerve; the spinal accessory passes downwards and outwards behind it, and the glosso-pharyngeal and hypoglossal nerves forwards between the vein and the internal carotid artery.
After the vein, the jugular bulb, and the sigmoid sinus have been exposed throughout their course, their outer wall is cut through with a pair of blunt-pointed scissors along its whole length, so as to convert the venous canal into an open gutter. The thrombus is then curetted out and the dissected portion of the jugular vein cut off as high up as possible. Any bleeding from the inferior petrosal sinus or condyloid veins, which may not be thrombosed, should be arrested by direct pressure of a strip of gauze over the bleeding points. The wound cavity is then washed out with a weak biniodide solution and dried.