Magnetic resonance imaging, computed tomography, and histopathological features of suspected cervical spinal fibrous hamartoma in a young dog

Introduction / Purpose: This report describes the clinical, MRI, CT, and post-mortem findings of an unusual presentation of a cervical intradural-extramedullary mass causing non-ambulatory tetraparesis in a young dog. Methods: An eight-month-old female German Shepherd was presented with a two-month history of right sided hemiparesis progressive to non-ambulatory tetraparesis. A cervical spine MRI was performed using a 1.5T scanner, which included T2-weighted, T1-weighted pre- and postcontrast, T2-STIR and T2-GE sequences. Additionally, dynamic CT-angiography and CT-myelography of the cervical spine were performed using a 64-row multidetector scanner. A cerebrospinal fluid sample was obtained after the CT. The patient was euthanased, and post-mortem examination and histopathology were performed. Results: The MRI showed a multilobulated and faintly contrast-enhancing mass of mixed signal intensity occupying most of the cross-sectional area of the vertebral canal at the level of cervical vertebrae C3-C4. CT-angiography and CT-myelography revealed circumferential attenuation of the subarachnoid space by the mass, with no evidence of vascular involvement. Cerebrospinal fluid analysis revealed normal total cell count with an increased proportion of neutrophils and a mild increase in total protein concentration. Post-mortem examination and histopathology revealed an intradural-extramedullary mass composed of dense bundles of eosinophilic collagen, low density of mesenchymal cells forming fibrous connective tissue and mild adipose tissue infiltration, with no evidence of inflammatory or neoplastic cells. Discussion / Conclusion: The age of presentation and histopathological findings of this case are consistent with a fibrous hamartoma of infancy, an uncommon lesion described in the human literature, rarely reported with spinal localisation.