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Chapter 13: Surgical Treatment of Skull Tumors 123

of the muscles of the skull attach to the mandible and maxilla for Surgical Technique
mastication [16]. The main muscular group encountered during The surgical approach to the mass will vary depending on its
craniectomy is the temporalis muscle. The margins of the tempo- location but whenever possible should be curvilinear to allow
ralis muscle include the orbital ligament and frontal crest crani- access to the entire region of the skull and temporalis fascia.
ally, the zygomatic arch laterally, the external sagittal crest When a skin incision is created, the biopsy tract should be
medially, and the dorsal nuchal line caudally [17] (Figure 13.3). removed in cases of malignancy, with a 1‐cm margin, and this
The most significant vessels that may be encountered during rou- entire tract of tissue should remain with the mass (Figure 13.6).
tine craniectomy include the dorsal sagittal and transverse Following skin incision, depending on the location, the tempora-
sinuses, which lie within the dura [18] (Figure 13.4). The dorsal lis fascia and muscle may be identified overlying the mass. For
sagittal sinus extends along the midline rostrally, from the cribri- bony tumors that are not growing into this fascia it should be
form plate to the occipital bone, and enters the skull at the level preserved for closure. Depending on the location of the mass, the
of the tentorium [18]. temporalis fascia may be incised on the medial or lateral border.
The temporalis muscle is then preserved, or removed as a margin
associated with the mass, to expose the skull using a combination
Patient Positioning of sharp dissection, electrocoagulation, and periosteal elevation.
Craniectomy for skull tumors requires extensive preoperative plan-
ning and a wide clip and surgical preparation. In cases of primary
bone tumors, the skin should be freely moveable over the mass and
therefore does not require extensive resection (except for the biopsy
tract). The patient will be placed in sternal recumbency or slightly
oblique to allow for easy access to the entire head (Figure 13.5). A
vacuum bag or patient positioning device can help to ensure the
animal remains in the same position throughout surgery. Patients
should receive antimicrobial prophylaxis 30 min prior to the start of
surgery and every 90 min thereafter.

Figure 13.3 Illustration of the temporalis muscle, which is encountered dur-
ing dorsal or rostral craniectomy and can be used for reconstruction of the Figure 13.5 The patient is positioned in sternal recumbency with the assis-
defect. Source: Courtesy of Emily Wong. tance of a vacuum bag. The entire head is clipped and prepared for surgery.

Figure 13.4 Illustration of the sinuses that may
be encountered during craniectomy. Care must
be taken to avoid damage to the dorsal sagittal
sinus (A) and paired transverse sinuses (B),
which are located within the dura and can be dis-
rupted during bone removal. Source: Courtesy of
Emily Wong.