Tethered Cord Syndrome Associated with a Thickened Filum Terminale in a Dog

A1-year-old female neutered English Cocker Spaniel was presented with a 9 months history of progressive right pelvic limb lameness. Survey radiographs, computed tomography (CT), magnetic resonance imaging (MRI), and joint taps of the pelvis, stifles, hock joints and tarsi, performed before referral, were within normal limits. Medical management with meloxicam did not result in clinical improvement. Treatment with gabapentin, initiated 7 days before presentation, resulted in improvement. General physical examination did not reveal any abnormalities. Neurological examination revealed paraparesis, right pelvic limb lameness, a low tail carriage, proprioceptive deficits expressed by delayed hopping, but intact paw placement in both pelvic limbs, a reduced withdrawal reflex in the right pelvic limb and decreased tail tone. Pain was elicited on lumbosacral palpation, dorsal extension of the tail and extension of both hips. The remainder of the neurological examination was within normal limits. Her neurological lesion was localized to the L4-S3 spinal cord segments. A complete blood count and biochemistry panel were within normal limits. After premedication with methadone (0.2 mg/kg IM) and acepromazine (0.0 1mg/kg IM), anesthesia was induced with propofol (4–6 mg/kg, IV), and maintained with sevoflurane in oxygen. MRI of the lumbar and lumbosacral vertebral column was performed with the dog in dorsal recumbency with flexed limbs (ie, frog-leg position). The imaging protocol included sagittal and transverse plane T2-weighted (repetition time (ms) (TR), echo time (ms) (TE), 3000/120), sagittal and dorsal plane T2-weighted short-tau inversion recovery (TR/TE, 3612/80), and transverse plane T2-weighted BAL TGRAD (TR/TE, 7.9/3.9) sequences. Sagittal and transverse plane T1-weighted (T1W TSE) (TR/TE, 400/8) images were acquired before and after IV injection with gadolinium contrast. MRI demonstrated possible caudodorsal displacement of the conus medullaris. Mild lumbosacral intervertebral disk protrusion was also seen (Fig 1). After MRI, a CT examination of the lumbosacral vertebral column was performed using a 16-slice scanner. After completion of the transverse CT study, sagittal and dorsal reconstructions were made. CT imaging (Fig 2) confirmed the MRI findings and did not reveal any other vertebral or spinal abnormalities. Differential diagnoses included tethered cord syndrome and dynamic lumbosacral vertebral canal stenosis. Given her initial positive response, medical management was continued with gabapentin (10mg/kg, q8h, PO), carprofen (2mg/kg, q12h, PO) and restricted exercise for 4 weeks. A re-examination 4 weeks later demonstrated progression of her clinical signs characterized by more pronounced paraparesis and right pelvic limb lameness. General anesthesia was induced and maintained with the aforementioned protocol. A standard dorsal lumbosacral laminectomy, from L7 to S2 was performed. After opening the vertebral canal, a ligamentous structure was identified between the conus medullaris and the dorsal lamina of S2, which caused caudodorsal displacement and traction of the conus medullaris (Fig 3A,B). After sectioning and sampling the distal aspect of this ligamentous structure, the conus medullaris regained a more cranial position. The wound was closed routinely. Intraoperative analgesia was provided with ketamine (loading dose of 0.5 mg/kg IV followed by a CRI at 10 lg/kg/min IV) and methadone (0.1 mg/kg q4h, IV). Postoperative analgesia consisted of a combination of methadone (0.2 mg/kg, q4h, IV), carprofen (2 mg/kg, q12h, PO) and gabapentin (10 mg/kg, q8h, PO). The dog was discharged from hospitalization 4 days after surgery. The owner was advised to provide strict rest for 4 weeks in combination with gabapentin and carprofen for 2 more weeks. From the Department of Veterinary Clinical Science and Services, (De Decker, Gregori, Kenny, Hoy, Volk); Department of Pathology and Pathogen Biology, The Royal Veterinary College, University of London, North Mymms, Hertfordshire England (Erles). Department of Veterinary Clinical Science and Services, The Royal Veterinary College, University of London, Hawkshead Lane, North Mymms, Hertfordshire AL97TA, England. This case report was presented in abstract form (poster) at the 27 Symposium of the European College of Veterinary Neurology (ECVN), 18–20 September 2014, Madrid, Spain. Corresponding author: S. De Decker, Department of Veterinary Clinical Science and Services, The Royal Veterinary College, University of London, Hawkshead Lane, North Mymms, Hertfordshire AL97TA, England; e-mail: [email protected]. Submitted September 15, 2014; Revised October 28, 2014; Accepted November 11, 2014. Copyright © 2015 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of American College of Veterinary Internal Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. DOI: 10.1111/jvim.12522 Abbreviations: