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Objective Design 3D printed skull contoured brain biopsy guides (3D-SCGs) from computed tomography (CT) or T1-weighted magnetic resonance imaging (T1W MRI). Study Design Feasibility study. Sample Population Five beagle dog cadavers and two client-owned dogs with brain tumors. Methods Helical CT and T1W MRI were performed on cadavers. Planned target point was the head of the caudate nucleus. Three-dimensional-SCGs were created from CT and MRI using commercially available open-source software. Using 3D-SCGs, biopsy needles were placed into the caudate nucleus in cadavers, and CT was performed to assess needle placement accuracy, followed by histopathology. Three-dimensional-SCGs were then created and used to perform in vivo brain tumor biopsies. Results No statistical difference was found between the planned target point and needle placement. Median needle placement error for all planned target points was 2.7 mm (range: 0.86-4.5 mm). No difference in accuracy was detected between MRI and CT-designed 3D-SCGs. Median needle placement error for the CT was 2.8 mm (range: 0.86-4.5 mm), and 2.2 mm (range: 1.7-2.7 mm) for MRI. Biopsy needles were successfully placed into the target in the two dogs with brain tumors and biopsy was successfully acquired in one dog. Conclusion Three-dimensional-SCGs designed from CT or T1W MRI allowed needle placement within 4.5 mm of the intended target in all procedures, resulting in successful biopsy in one of two live dogs. Clinical Significance This feasibility study justifies further evaluation of 3D-SCGs as alternatives in facilities that do not have access to stereotactic brain biopsy.

Objective Design 3D printed skull contoured brain biopsy guides (3D-SCGs) from computed tomography (CT) or T1-weighted magnetic resonance imaging (T1W MRI). Study Design Feasibility study. Sample Population Five beagle dog cadavers and two client-owned dogs with brain tumors. Methods Helical CT and T1W MRI were performed on cadavers. Planned target point was the head of the caudate nucleus. Three-dimensional-SCGs were created from CT and MRI using commercially available open-source software. Using 3D-SCGs, biopsy needles were placed into the caudate nucleus in cadavers, and CT was performed to assess needle placement accuracy, followed by histopathology. Three-dimensional-SCGs were then created and used to perform in vivo brain tumor biopsies. Results No statistical difference was found between the planned target point and needle placement. Median needle placement error for all planned target points was 2.7 mm (range: 0.86-4.5 mm). No difference in accuracy was detected between MRI and CT-designed 3D-SCGs. Median needle placement error for the CT was 2.8 mm (range: 0.86-4.5 mm), and 2.2 mm (range: 1.7-2.7 mm) for MRI. Biopsy needles were successfully placed into the target in the two dogs with brain tumors and biopsy was successfully acquired in one dog. Conclusion Three-dimensional-SCGs designed from CT or T1W MRI allowed needle placement within 4.5 mm of the intended target in all procedures, resulting in successful biopsy in one of two live dogs. Clinical Significance This feasibility study justifies further evaluation of 3D-SCGs as alternatives in facilities that do not have access to stereotactic brain biopsy.

Background: Quantitative magnetic resonance imaging (QMRI) techniques of magnetization transfer ratio (MTR) and diffusion tensor imaging (DTI) provide microstructural information about the spinal cord. Objective: Compare neurologic grades using the modified Frankel scale with MTR and DTI measurements in dogs with thoracolumbar intervertebral disk herniation (IVDH). Animals: Fifty-one dogs with thoracolumbar IVDH. Methods: Prospective cohort study. Quantitative MRI measurements of the spinal cord were obtained at the region of compression. A linear regression generalized estimating equations model was used to compare QMRI measurements between different neurological grades after adjusting for age, weight, duration of clinical signs, and lesion location. Results: Grade 5 (.79 × 10−3 mm2/s [median],.43−.91 [range]) and axial (1.47 × 10−3 mm2/s,.58−1.8) diffusivity were lower compared to grades 2 (1.003,.68−1.36; P =.02 and 1.81 × 10−3 mm2/s, 1.36−2.12; P <.001, respectively) and 3 (1.07 × 10−3 mm2/s,.77−1.5; P =.04 and 1.92 × 10−3 mm2/s, 1.83−2.37; P <.001, respectively). Compared to dogs with acute myelopathy, chronic myelopathy was associated with higher mean (1.02 × 10−3 mm2/s,.77−1.36 vs.83 × 10−3 mm2/s,.64−1.5; P =.03) and radial diffusivity (.75 × 10−3 mm2/s,.38−1.04 vs.44 × 10−3 mm2/s,.22−1.01; P =.008) and lower MTR (46.76, 31.8−56.43 vs. 54.4, 45.2−62.27; P =.004) and fractional anisotropy (.58,.4−0.75 vs.7,.46−.85; P =.02). Fractional anisotropy was lower in dogs with a T2-weighted intramedullary hyperintensity compared to those without (.7,.45−.85 vs.54,.4−.8; P =.01). Conclusion and Clinical Relevance: Mean diffusivity and AD could serve as surrogates of severity of spinal cord injury and are complementary to the clinical exam in dogs with thoracolumbar IVDH.

Background Stereotactic brain biopsy (SBB) allows for histopathologic diagnosis of brain tumors. Adverse events (AE) occur in 5 to 29% of dogs after SBB, but risk factors associated with developing AE are poorly described. Objective Identify clinicopathologic, diagnostic imaging, or procedural variables that are associated with AE in dogs after SBB. Animals Twenty-nine dogs with brain tumors. Methods Retrospective, case-control study. Dogs had laboratory investigations performed before SBB, as well as clinical examinations and diagnostic imaging of the brain before and after SBB. Cases experienced AE after SBB including transient exacerbation of preexisting neurologic deficits, transient new deficits, or permanent neurologic deficits. Controls had SBB performed without AE. Fisher's exact and Student'sttests were used to examine associations between the postulated risk factors and AE. Results Adverse events occurred in 8/29 (27%) dogs, and 7/8 AE (88%) were transient. Cases were significantly more likely to have T2W-heterogenous tumors (88 versus 38%;P= .04) and lower platelet counts (194.75 +/- 108.32 versus 284.29 +/- 68.54 x10(3)/mm(3),P= .006). Dogs with gradient echo signal voids present on baseline imaging were significantly more likely to have hemorrhage present after biopsy, and 7/8 (88%) of cases had hemorrhage on imaging after SBB. Conclusion and Clinical Importance Twenty-seven percent of dogs undergoing SBB experience AE, with the majority of AE resolving with 1 week. Platelet counts should be >= 185 000/mm(3)to minimize risk of SBB-associated AE. Observation of intracranial hemorrhage after biopsy can have important clinical implications, as this was observed in 88% of dogs with AE.

Background Stereotactic brain biopsy (SBB) allows for histopathologic diagnosis of brain tumors. Adverse events (AE) occur in 5 to 29% of dogs after SBB, but risk factors associated with developing AE are poorly described. Objective Identify clinicopathologic, diagnostic imaging, or procedural variables that are associated with AE in dogs after SBB. Animals Twenty-nine dogs with brain tumors. Methods Retrospective, case-control study. Dogs had laboratory investigations performed before SBB, as well as clinical examinations and diagnostic imaging of the brain before and after SBB. Cases experienced AE after SBB including transient exacerbation of preexisting neurologic deficits, transient new deficits, or permanent neurologic deficits. Controls had SBB performed without AE. Fisher's exact and Student'sttests were used to examine associations between the postulated risk factors and AE. Results Adverse events occurred in 8/29 (27%) dogs, and 7/8 AE (88%) were transient. Cases were significantly more likely to have T2W-heterogenous tumors (88 versus 38%;P= .04) and lower platelet counts (194.75 +/- 108.32 versus 284.29 +/- 68.54 x10(3)/mm(3),P= .006). Dogs with gradient echo signal voids present on baseline imaging were significantly more likely to have hemorrhage present after biopsy, and 7/8 (88%) of cases had hemorrhage on imaging after SBB. Conclusion and Clinical Importance Twenty-seven percent of dogs undergoing SBB experience AE, with the majority of AE resolving with 1 week. Platelet counts should be >= 185 000/mm(3)to minimize risk of SBB-associated AE. Observation of intracranial hemorrhage after biopsy can have important clinical implications, as this was observed in 88% of dogs with AE.

Background: Quantitative magnetic resonance imaging (QMRI) techniques of magnetization transfer ratio (MTR) and diffusion tensor imaging (DTI) provide microstructural information about the spinal cord. Objective: Compare neurologic grades using the modified Frankel scale with MTR and DTI measurements in dogs with thoracolumbar intervertebral disk herniation (IVDH). Animals: Fifty-one dogs with thoracolumbar IVDH. Methods: Prospective cohort study. Quantitative MRI measurements of the spinal cord were obtained at the region of compression. A linear regression generalized estimating equations model was used to compare QMRI measurements between different neurological grades after adjusting for age, weight, duration of clinical signs, and lesion location. Results: Grade 5 (.79 × 10−3 mm2/s [median],.43−.91 [range]) and axial (1.47 × 10−3 mm2/s,.58−1.8) diffusivity were lower compared to grades 2 (1.003,.68−1.36; P =.02 and 1.81 × 10−3 mm2/s, 1.36−2.12; P <.001, respectively) and 3 (1.07 × 10−3 mm2/s,.77−1.5; P =.04 and 1.92 × 10−3 mm2/s, 1.83−2.37; P <.001, respectively). Compared to dogs with acute myelopathy, chronic myelopathy was associated with higher mean (1.02 × 10−3 mm2/s,.77−1.36 vs.83 × 10−3 mm2/s,.64−1.5; P =.03) and radial diffusivity (.75 × 10−3 mm2/s,.38−1.04 vs.44 × 10−3 mm2/s,.22−1.01; P =.008) and lower MTR (46.76, 31.8−56.43 vs. 54.4, 45.2−62.27; P =.004) and fractional anisotropy (.58,.4−0.75 vs.7,.46−.85; P =.02). Fractional anisotropy was lower in dogs with a T2-weighted intramedullary hyperintensity compared to those without (.7,.45−.85 vs.54,.4−.8; P =.01). Conclusion and Clinical Relevance: Mean diffusivity and AD could serve as surrogates of severity of spinal cord injury and are complementary to the clinical exam in dogs with thoracolumbar IVDH.

Intramedullary signal change (ISC) is a non-specific finding that is frequently observed on magnetic resonance imaging (MRI) examinations of the canine spinal cord. ISC can represent a variety of primary pathological processes such as neoplasms or myelitides or secondary changes such as edema, cysts, gliosis, or myelomalacia. An unusual phenotype of ISC is the "snake-eye" myelopathy (SEM), which refers to bilaterally symmetric T2 hyperintensities preferentially affecting the ventral horn gray matter on transverse MR images, which resemble a pair of snake's eyes. The pathophysiology of SEM is poorly understood in humans, and this imaging finding may be associated with cervical spondylotic myelopathy, spinal cord ischemia, ossification of the posterior longitudinal ligament, amyotrophic lateral sclerosis, and Hirayama disease. Here we describe four dogs with cervical MRI examinations consistent with an SEM-like phenotype. All dogs initially presented with a central cord syndrome or tetraparesis referable to a C6-T2 neuroanatomic localization, which was attributed to disc-associated spinal cord compression in three cases, while one dog had the SEM-like phenotype with no identifiable etiology. Once the SEM-like phenotype was present on MRI examinations, dogs demonstrated insidious clinical deterioration despite therapeutic interventions. Deterioration was characterized by lower motor neuron weakness and neurogenic muscle atrophy progressing to paralysis in the thoracic limbs, while neurological functions caudal to the level of the SEM-like lesion remained largely preserved for months to years thereafter. Neuropathological features of the SEM-like phenotype include multisegmental cavitations and poliomyelomalacia of laminae VI-IX of the caudal cervical spinal cord, although the lesion evolved into pan-necrosis of gray matter with extension into the adjacent white matter in one case with an 8 years history of progressive disease. Although the pathophysiology of SEM remain