Massive midline occipitotemporal resection of the skull for treatment of multilobular osteochondrosarcoma in two dogs

CASE DESCRIPTION: Two 6-year-old male dogs were evaluated for removal of midline occipito-temporal multilobular osteochondrosarcomas. CLINICAL FINDINGS: Physical examination revealed mild ataxia in 1 dog and large masses of the central occipitotemporal portion of the skull in both dogs. Computed tomography, magnetic resonance imaging (MRI), or both revealed large bone-origin occipitotemporal masses with impingement of the brain and the sagittal and transverse venous sinuses. Three-dimensional contrast magnetic resonance image reconstruction delineated collateral venous circulation around the tumor and venous sinus occlusion in 1 dog. TREATMENT AND OUTCOME: Tumors in both dogs were surgically removed and the skull defects repaired with polymethyl methacrylate prostheses. Twenty-four hours after surgery, 1 dog had normal mentation, cranial nerve function, and conscious proprioceptive responses, whereas the other dog had depressed mentation but no neurologic deficits. Both dogs were discharged 4 days after surgery with normal mentation and no neurologic deficits. CLINICAL RELEVANCE: Findings suggested that MRI and computed tomography can play a key role in assessment of essential cortical collateral circulation when surgical removal of tumors is likely to result in bilateral disruption of transverse venous sinuses. Without robust collateral circulation and proper preoperative planning, removal of massive skull tumors in the midline occipitotemporal region will likely result in substantial morbidity or death. However, results in the 2 dogs reported here indicate the feasibility of removing such tumors with good outcomes in the presence of well-developed collateral venous drainage.