PMC6624786_01
Topography, MRI, and gross pathological appearance of canine snake eye myelopathy (SEM)-like phenotype. (A) Schematic and normal T2W transverse MR image (lower inset) of canine C5 spinal cord segment illustrating putative arterial supply and Rexed laminar structure of the gray matter (upper inset). SEM-like lesions appear as bilaterally symmetric lesions (white dashed ovals) distributed in laminae VI-IX of the gray matter. (B) Transverse T2W MRI through the cranial aspect of C5 from Case 1 with the SEM-like phenotype demonstrating bilaterally symmetric intramedullary hyperintensities in the ventral horn gray matter and dorsoventral flattening of the spinal cord. (C) The SEM-like phenotype is pathologically characterized by bilateral cavitations in the C5 ventral horns and poliomalacia; Case 1.
fvets-06-00219-g0001.jpg
PMC6624786_01_fvets-06-00219-g0001.jpg
F1
T2W (Figure 1B) and FLAIR images, the hyperintensities were bilaterally symmetric and restricted to the ventral gray matter. Bilateral cavitary lesions (Figure 1C) involving ventral horn gray matter was observed extending from the cranial aspect of the C5 through the C8 spinal cord segments.
PMC6624786_02
Serial MRI and neuropathology of Case 2. (A) Transverse T2W image with hypointense extradural lesion at C5-C6 disc space, lateralized to the right aspect of the vertebral canal, and causing marked compression and displacement of the spinal cord. The lesion is of mixed signal intensity on transverse TIW post-contrast images (B) suggesting the presence of extradural hemorrhage admixed with hypointense extruded disc (white arrow). (C) Sagittal T2W image obtained 7 days after surgery demonstrating the C5-C6 ventral slot defect and a tubular hyperintense intramedullary lesion extending from the cranial aspect of C5 to the cranial aspect of C7. On transverse images, the SEM-like phenotype appears as bilaterally symmetric T2W hyperintense (D) gray matter lesions that are mildly T1W hyperintense (E) and contrast-enhancing (F). Despite resolution of the previous extradural compression, the spinal cord throughout the lesion region is swollen with attenuation of the subarachnoid space. (G) Histology of the C6 spinal cord demonstrating various stages of cavitations (black arrow) and gray matter necrosis, with neurons in the lateral portions of laminae VII and IX displaying acidophilic necrosis characterized by angular and hypereosinophilic cytoplasm and nuclear pyknosis. At the junction of the intermediate and ventral gray horns (dashed line) with spinal cord white matter, there is also white matter vacuolization. H&E stain.
fvets-06-00219-g0002.jpg
PMC6624786_02_fvets-06-00219-g0002.jpg
F2
An MRI of the cervical spine was performed under general anesthesia, the results of which were consistent with C5-C6 IVDH with associated compressive extradural hemorrhage (Figures 2A,B). However, contrast-enhancing ISC with an SEM-like phenotype was observed (Figures 2C-F), and subacute reperfusion injury, intramedullary hemorrhage, edema, myelitis, or infarction considered possible etiologies for the imaging abnormalities. Pathological findings in the gray matter were similar to those described for Case 1, except that at the junction of the ventral and intermediate gray horns with white matter, vacuolization of the white matter associated with variable axonal swelling was observed (Figure 2G).
PMC6624786_03
Serial MRI and neuropathology of Case 3. T2W transverse (A) and parasagittal images (B) at the time of initial diagnosis of C6-C7 CSM demonstrating no ISC within the spinal cord. Transverse (C) T2W and dorsal STIR (D) obtained 6 years after initial surgery revealing bilaterally symmetric hyperintense SEM-like lesions in the ventral gray matter overlying the C6-C7 disc space. On MRI examination obtained 2 years after panels (C,D), the previously noted SEM-like lesions have coalesced into a singular T2W/STIR hyperintense intramedullary lesion involving all gray matter regions (E,F), and spinal cord atrophy has also progressed at the C6-C7 site. (G) Geographic cavitation (asterisks) and gray matter necrosis is present in the gross specimen of the C6 spinal cord segment. (H) Bilateral cavitation and necrosis of the gray matter is evident on a histologic section of the C6 spinal cord with vacuolization extending into the surrounding white matter. H&E stain.
fvets-06-00219-g0003.jpg
PMC6624786_03_fvets-06-00219-g0003.jpg
F3
A cervical MRI examination performed at that time revealed disc-associated CSM at C6-C7, with no abnormal ISC detected (Figures 3A,B). T2W/STIR hyperintensity consistent with an SEM-like phenotype was observed over the disc space of C6-C7 (Figures 3C,D), as were changes within the vertebral bodies of C6-C7 consistent with a previous ventral slot procedure. The T2W/STIR hyperintense lesions affecting the gray matter (Figures 3E,F). The dog was euthanized and a necropsy performed. On sectioning, the C6 segment contained extensive bilateral cavitations, poliomyelomalacia, and tan discoloration of the gray matter (Figure 3G). Microscopic examination revealed that the cavitary processes extending from the C5-C7 segments largely obliterated the gray matter bilaterally and extended in a symmetric cribriform fashion far into adjacent white matter, with changes most extensive in the C6 segment (Figure 3H).
PMC6624786_04
MRI features of the SEM-like phenotype, Case 4. (A) Sagittal T2W image with linear hyperintense intramedullary lesion extending from the cranial aspect of C6 to the cranial aspect of C7. On transverse images, SEM appears as bilaterally symmetric T2W and T2*GRE (B) hyperintense lesions in the ventral gray matter that are T1W isointense (C) and non-enhancing following intravenous gadolinium administration (D). There is heterogeneously increased T2W signal [(B), arrow] and contrast enhancement (D) of the left serratus ventralis muscle.
fvets-06-00219-g0004.jpg
PMC6624786_04_fvets-06-00219-g0004.jpg
F4
An MRI examination of the cervical spine was obtained under general anesthesia (Figure 4), with ISC with an SEM-like phenotype identified in the caudal cervical spinal cord.