Spinal epidural empyema in pug

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1 Vet Times The website for the veterinary profession Spinal epidural empyema in pug Author : ELISA BEST, IAN JENNINGS Categories : Vets Date : May 26, 2014 ELISA BEST BVSc, CertSAS, MRCVS IAN JENNINGS BVSc, BSc, CertVDL, MRCVS describe the diagnosis and treatment decisions they made when a two-year-old female entire pug presented with acute paraparesis Summary A young pug presented with acute paraparesis, which rapidly deteriorated to paralysis. Presumptive diagnosis of an epidural empyema was made using MRI, and was confirmed surgically and through blood culture. Treatment consisted of surgical decompression and antibiotics, which led to a satisfactory outcome. Key words spinal abscess/empyema, Schiff-Sherrington, dorsal laminectomy, Pasteurella multocida A TWO-YEAR-OLD female entire pug was admitted to the Rowe Veterinary Hospital, Bristol for evaluation of acute onset paraparesis. The dog had been sent to stud three weeks previously, and had been clinically normal up until 12 hours prior to presentation, when it became inappetent and had vomited. The owner had confined the dog to its crate overnight and that morning had found it distressed, panting and walking on 1 / 14

2 tiptoes. On presentation it was found to be mildly pyrexic (temperature 39.4 C), panting and very anxious. The dog was able to walk, but both pelvic limbs were rigid with both stifles in hyper-extension and both feet were knuckled over. General clinical examination was unremarkable, apart from increased upper respiratory noise and pain on palpation of the caudal thoracic spine. Neurological examination showed loss of proprioception in both pelvic limbs with increased muscle tone and exaggerated spinal reflexes. Voluntary movement was present in both pelvic limbs. The pug was able to walk normally on its forelimbs; no proprioceptive deficits were present and spinal reflexes were normal. The limbs did, however, show increased muscle tone. Cranial nerve examination was unremarkable. The lesion was localised to the T3 to L3 region of the spinal cord. Routine haematology, biochemistry and electrolytes were performed. Apart from moderate leukocytosis (white blood cell count / mm [6-17]) and granulocytosis (granulocytes /mm [3-11.5]), there were no significant findings. Abdominal ultrasound ruled out pregnancy and was also otherwise unremarkable. The dog was placed on intravenous fluids and analgesia was administered, namely buprenorphine (0.02mg/ kg every six hours IV) and meloxicam (0.05mg/kg every 24 hours SC). However, it deteriorated and by the following morning it had lost voluntary movement in both pelvic limbs, as well as some muscle tone. Spinal reflexes were still present, but not as marked as the previous day. The pug also started to show Schiff-Sherrington posture (Figure 1). As it had passed diarrhoea, NSAIDs were discontinued and gastroprotectants (ranitidine 2mg/kg every eight hours IV) commenced. The dog was anaesthetised and MRI of its spine was performed. The images were acquired using a 1.5 tesla high field scanner. T2-weighted (T2W), T1-weighted (T1W) and short tau inversion recovery (STIR) images were obtained of the thoracolumbar spine in the sagittal plane and transversely from T11 to T13. Following the intravenous administration of a paramagnetic contrast medium, further images were obtained in the sagittal and transverse planes (T1Wgad). A lesion was identified extending from the level of the T11/T12 intervertebral disk space to the cranial aspect of T13, causing a left-sided dorsolateral extradural compression of the spinal cord, resulting in 50 per cent reduction in cord diameter. The lesion appeared hyperintense on T2W and STIR images, and isointense to muscle on T1W images (Figure 2). An increase in signal from the caudal part of the dorsal lamina of T12 and the dorsal paraspinal muscles at the level of the T12/T13 articulation was also appreciated in the 2 / 14

3 sagittal STIR images. There was marked peripheral contrast enhancement on T1Wgad images at the central point of the lesion, which became more diffuse at the level of the T12 vertebral foramina; the site of maximum compression (Figure 3).Contrast enhancement extended bilaterally from the epidural space into the paraspinal muscles. A dehydrated disk at L4/L5 was noted incidentally. The aforementioned findings were considered consistent with an epidural abscess. A urine sample obtained by cystocentesis was submitted for culture and sensitivity. A blood sample for bacterial culture was also performed, after which intravenous antibiotics were commenced, namely cefazolin (22mg/kg every eight hours) and metronidazole (15mg/kg every 12 hours). The dog remained neurologically unchanged after 48 hours of therapy and it was, therefore, decided to perform surgical decompression. Analgesia was provided using methadone (0.3mg/kg every four hours) in conjunction with a ketamine 5?g/ kg/hr and lidocaine 20?g/ kg/hr constant rate infusion. A dorsal approach to the caudal thoracic vertebra was made. On clipping the skin, multiple small, round, scar-like lesions were found over the affected area (Figure 4). No abnormalities were found on dissection of the paraspinal muscles. The dorsal spinous processes were removed from T11, T12 and T13. A dorsal laminectomy extending from T11 to T13 was performed, leaving the articular facets of the vertebra intact to prevent instability. No discrete areas of pus were found; however, the interarcuate ligament at the level of T12 was grossly thickened. This ligament, as well as epidural fat, was removed to reveal the spinal cord (Figure 5). The tissue was submitted for histopathology and bacterial/fungal culture. The area was gently lavaged with warmed sterile saline and closed in a routine manner using triclosan impregnated 2-0 polydioxanone, 3-0 poliglecaprone and sterile cyanoacrylate glue. Postoperative care consisted of ongoing analgesia and intravenous antibiotic administration. The dog started to reflux postoperatively so ranitidine 2mg/kg every eight hours IV and metoclopramide 0.5mg/kg every 12 hours IV was administered to control this. Massage and physiotherapy was instituted 24 hours postsurgery. The dog regained motor function three days postsurgical decompression and was able to walk with sling support after 10 days (Figure 6). Although currently ambulatory, the dog has continued to show ongoing pelvic limb proprioceptive deficits, is moderately ataxic and hypermetric on both pelvic limbs six weeks postsurgery. Histopathology of the excised tissue was consistent with neutrophilic inflammation and necrosis of a variety of connective tissue, including adipose and fibrous tissue. A diagnosis of cellulitis was concluded. Urine and tissue cultures were both negative, but blood culture revealed a scanty pure growth of Pasteurella multocida. On further discussion and questioning, the owner noted one of her other pugs would frequently attack the patient, although the attacker had severe dental disease that rendered the attacks ineffectual. 3 / 14

4 The appearance of the skin over the affected site would be consistent with chronic low-grade trauma from teeth, which have probably inoculated the bacteria into the area. Discussion Spinal epidural empyema (SEE), also referred to as a spinal abscess, is a suppurative septic process in the neural canal resulting in spinal cord compression1. Infection may be by direct local extension or haematogenous spread. It is a rare disease in both dogs and humans, and is rarely reported in the veterinary literature. Prior to the 1930s, this was normally a necropsy finding in humans, but recent advances in both diagnosis and treatment have reduced mortality rate to around 15 per cent1. In humans, intravenous drug use and diabetes mellitus are risk factors for developing this disease (not including post-intervention infections)2. Clinical signs most often reported include spinal pain, fever and varying levels of neurological deficits1,3. In a report featuring seven cases, one presented with Schiff-Sherrington posture, although this is certainly not a consistent finding. Schiff-Sherrington is defined as interference with the ascending motor tracts that results in loss of inhibition to the thoracic limb extensors. This typically results in rigidity and extension of the thoracic limbs, but with normal proprioception and motor function and should not be confused with a C1 to C5 lesion. It is not an indicator of prognosis, but usually indicates a severe lesion in the T3 to L3 spinal cord segment and is often associated with trauma cases. It is unclear why this dog progressed to showing this posture. Diagnosis of SEE in the older literature is often described using myelography followed by surgical exploration. MRI has become the imaging modality of choice in human medicine for the diagnosis of spinal epidural abscesses above that of myelography, CT or CT-myelography, as differentiating between other potential causes of acute myelopathy can be more readily achieved4. Standard or CT myelography also has the potential to seed the infectious agent along the subarachnoid space5. The hyperintense signal on T2W and STIR images, alongside that of the patterns of contrast enhancement of the compressive lesion and paraspinal muscles on T1Wgad images, is consistent with an inflammatory lesion of the epidural space extending into surrounding tissue. Other MRI studies have shown similar imaging patterns with both infectious5 and sterile6 epidural empyema, as well as paraspinal infection7. Identification of the causative organism was identified from culture of both blood and material collected at the time of surgery1. Interestingly, organisms were not isolated from cerebrospinal fluid (CSF) in the largest retrospective study1 and is rarely reported as being positive in humans. CSF did, however, confirm a septic process. CSF was not collected in this case. Bacteria cultured from blood and surgical sites included Escherichia coli, Bacteroides, Staphylococcus intermedius and 4 / 14

5 Clostridium perfringens1. Pasteurella multocida, cultured from this case, commonly lives in the upper respiratory tract of many vertebrate hosts. In humans, it is the most common bacteria cultured from wounds associated with dog and cat bites. Treatment in humans is still controversial, with both medical and combined medical/surgical therapy being used. The goal of surgery, as in this case, was to decompress the spinal cord, and obtain samples for histopathology and microbial culture and sensitivity. Although reported outcomes in the early literature were poor8, more recent reports suggest that, with early diagnosis and medical and surgical management, a satisfactory outcome can be expected1,5. References 1. Lavely J A, Vernau K M, Vernau W et al (2006). Spinal epidural empyema in seven dogs, Vet Surg 35(2): Alton T B, Patel A, Bellabarba C B et al (2014). Spinal epidural abscesses: risk factors, medical vs surgical management, a retrospective review of 128 cases, Spine J 14(2): Schmiedt C W and Thomas W B (2005). Spinal epidural abscess in a juvenile dog, Vet Comp Orthop Traumatol 18(3): Reihsaus E, Waldbaur H and Seeling W (2000). Spinal epidural abscess: a metaanalysis of 915 patients, Neurosurg Rev 23(4): De Stefani A, Garosi L S, McConnell F J et al (2008). Magnetic resonance imaging features of spinal epidural empyema in five dogs, Vet Radiol Ultrasound 49(2): Cornelis I, De Decker S, Gielen I et al (2013). Idiopathic sterile inflammation of the epidural fat and epaxial muscles causing paraplegia in a mixed breed dog, J Am Vet Med Assoc 242(10): 1,405-1, Holloway A, Dennis R, McConnell F and Herrtage M (2009). Magnetic resonance imaging features of paraspinal infection in the dog and cat, Vet Radiol Ultrasound 50(3): Dewey C W, Kortz G D and Bailey C S (1998). Spinal epidural empyema in two dogs, JAAHA 34(4): / 14

6 Figure 1. The dog showing Schiff-Sherrington posture as it deteriorated neurologically. 6 / 14

7 Figure 2. Sagittal STIR (top) and T2W (bottom) midline images showing a hyperintense lesion dorsal to the spinal cord at the level of T12 vertebral body extending to T12/T13. It can be best appreciated on STIR images, which also show a hyperintensity in the paraspinal muscles dorsal to the vertebra (arrow). 7 / 14

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9 Figure 3. Transverse T1W (left) and T1Wgad (right) images at the level of mid body T12 (top) and at the level of T12/T13 intervertebral space (bottom). The dorsal compression of the spinal cord at midbody T12 shows peripheral enhancement of the lesion (arrow) whereas at the level of T12/T13 9 / 14

10 intervertebral space a diffusely enhancing pattern is seen at the point of maximum compression (arrow). Bilateral enhancement of the paraspinal muscles shows the extent of the inflammation. Figure 4. Appearance of the skin over the surgical site. Multiple small scars were noted. 10 / 14

11 Figure 5. A dorsal laminectomy was used to decompress the spinal cord and obtain samples. 11 / 14

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14 Figure 6. Ten days postsurgery, the patient is ambulatory with sling support. 14 / 14 Powered by TCPDF (