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13 Surgical Treatment of Skull Tumors

Michelle Oblak and Andy Shores

Indications images and it is important to exercise caution when placing force on
Skull tumors are an uncommon primary bone tumor in the dog. the biopsy needle as the center of the mass can be softer, resulting in
Affected dogs have two classic presentations: the young dog with a disruption of the medial tumor capsule or iatrogenic brain trauma.
protracted history of a slowly growing mass, or the geriatric dog
with a newly discovered mass [1–3]. Rarely, these masses can invade
into the surrounding soft tissues and brain parenchyma, but more Preoperative Imaging
commonly these are tumors of bone that act as space‐occupying Skull radiographs can be helpful for evaluating the size of the mass
lesions [1,3–5]. In most cases, patients are asymptomatic [3–6]. and extent of cranial vault involvement. CT and magnetic resonance
Clinical signs may be seen if the tumor is in an area near the tempo- imaging (MRI) may be used independently or in combination
romandibular joint or orbit, or if it invades the sinus. Rarely, paren- depending on the clinical signs and expected soft tissue changes
chymal compression can result in circling, ataxia, seizures, or other [4,5,14]. Often the choice of advanced imaging modality will be
neurological abnormalities associated with the region of the brain determined based on personal preference as well as availability.
affected. Most dogs present because of a progressive mass effect on While CT can provide good anatomical localization and overview
the head but it is important to be aware that there may still be sig- for surgical planning, MRI is more sensitive for any potential parenchy-
nificant brain compression, despite a lack of clinical signs [4–6]. mal changes and can also help to better delineate important vascular
Any type of primary bone tumor can also develop in the skull structures [14].
but the most common differential diagnoses for primary skull During evaluation of advanced imaging results, close attention
tumors include multilobular osteochondrosarcoma, osteoma, and should be paid to the proximity of the dorsal sagittal and transverse
osteosarcoma [1–8]. Less commonly primary chondrosarcoma, venous sinuses, evidence of contrast enhancement within the tem-
squamous cell carcinoma, and fibrosarcoma can also occur in this poralis muscle, and involvement of the frontal sinus or cribriform
location [6,8]. plate. In addition, imaging will allow for a determination of the
When a patient presents for a suspected skull tumor, the diagnos- extent of the resultant skull defect and consideration of reconstruc-
tic work‐up is similar to that of any other tumor. Staging may tion options.
include a full physical examination and health screening (complete One significant advantage of incorporating CT into the planning
blood count, biochemistry profile and urinalysis, three‐view process is the ability to reconstruct images. Multiple planes and
thoracic radiographs, abdominal ultrasound) in addition to further three‐dimensional reconstruction can help with preoperative visu-
diagnostic evaluation. When the mass is malignant, fine‐needle alization and planning, as well as for client education (Figure 13.1,
aspiration and cytology may yield a diagnostic result [9]. If inci- Video 13.1). In complex cases where further insight and planning is
sional biopsy of the mass is to be undertaken, it should be per- required, three‐dimensional printing of the skull and associated
formed after advanced imaging is obtained and with the surgical mass can further assist with surgical preparation and planning
approach in mind, as the biopsy tract will need to be removed dur- (Figure 13.2).
ing definitive surgery [10,11]. Definitive diagnosis and prognosti-
cation from biopsies can be challenging due to the small sample
sizes [12,13]. Often a Jamshidi bone marrow biopsy needle or Surgical Anatomy
Michele Trephine bone biopsy instrument is required to obtain an The main bone regions of the cranium include the frontal, pari-
adequate sample of the tumor. In these cases, depth should be meas- etal, temporal, and occipital bones [15]. The cribriform plate
ured in advance from radiographs or computed tomography (CT) separates the cranial cavity from the nasal sinuses. The majority

Current Techniques in Canine and Feline Neurosurgery, First Edition. Edited by Andy Shores and Brigitte A. Brisson.
© 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/shores/neurosurgery

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