MRI and Radiographic finding
Using pre-contrast and post-contrast T2- and T1-weighted MRI images helps in distinguishing and identifying various tissues and lesions (
AlZubi Ali Ahmad, 2023). The hyperintense signal change in the spinal cord parenchyma was confirmed at the tenth thoracic vertebra to the first lumbar vertebra and a substance suspected of being blood pressing against the spinal cord was observed in the epidural region (Fig 1).
In addition, the signal of the surrounding muscles around the spinous process increased from the caudal thoracic vertebrae to the lumbar vertebrae and the spinous process of the 1
st lumbar vertebra was fractured (Fig 2). During the 3 days of hospitalization following the diagnosis, the patient was prescribed PDS (0.5 mg/kg, q12h Solondo Tab., YUHAN Co., Korea), gabapentin (10 mg/kg, q12h, Gabalep Cap., Chong Kun Dang Pharmaceutical Corp., Korea), streptokinase (0.05 T/kg, q12h, Verase Tab., Nelson, Korea) and misoprostol (5 mg/kg, q12h, Misoprostol Tab., Nelson, Korea) and the clinical symptoms were gradually improved.
Six months later, the cat presented again with more severe back pain and bilateral hind limb lameness. There was a knuckling sign, but no sensory or reflex impairment of the hind limb. The patient had no sensory or motor nerve problems in the neck, face, forelimbs or tail. Complete blood count revealed a mild neutrophilia elevation (11.76*109/L; reference range, 2.3-10.29*109/L) and serum biochemical values were within the reference ranges (data not shown).
To confirm the lesion of the thoracolumbar spinal cord via MRI, anaesthesia was induced using midazolam and propofol to allow implantation of the tracheal tube and general anaesthesia was performed by respiratory anaesthesia using isoflurane at the same dose. In the present study, we found that an abscess and a hematoma were severely compressing the spinal cord in the epidural region of the 13
th thoracic vertebra and the 1
st lumbar vertebra (Fig 3).
Surgical intervention
Surgical decompression was conducted the day after the diagnosis was confirmed by MRI. The patient was placed in the left recumbent position and the skin was incised between the eighth thoracic and third lumbar vertebrae to allow entry into the thoracolumbar space and to ensure visibility of the surgical field. When the subcutaneous fat and muscle were separated, there were no noticeable abnormalities in the subcutaneous tissue or the paravertebral muscles. A left-sided hemilaminectomy was performed using an ultrasonic surgical device (Sonocure, Tokyo Iken Co., Japan) between the thirteenth thoracic vertebra and the first lumbar vertebra. After the spinal canal was opened, pus exuded from the epidural space (Fig 4A) and a large amount of friable tissue that was compressed by the spinal cord was removed (Fig 4B). It was identified as spinal epidural empyema and the spinal cord appeared to be mostly normal. The area of the lesion was flushed with a large amount of sterile saline solution. The incised subcutaneous tissue and skin were routinely sutured (Fig 4C).
Postoperative management
The abscess that was recovered from the epidural space was subjected to aero/anaerobic bacteria identification and an antibiotic susceptibility test. During hospitalization, the patient was given oral gabapentin (10 mg/kg, q12h) and intravenous injections of cefazolin (25 mg/kg, q12h, IV, cefazolin inj., Chong Kun Dang Pharmaceutical Corp., Korea) and famotidine (0.5 mg/kg, q12h, IV, Gaster, Donga ST, Korea) into the vein, twice a day for five days.
Staphylococcus aureus was identified in the bacterial culture test. The results of the antibiotic susceptibility test revealed sensitivity to ampicillin, trimethoprim/sulfamethoxazole, amikacin, imipenem, amoxicillin/clavulanic acid, cefazolin, ampicillin/sulbactam and enrofloxacin, except for ampicillin. Based on the sensitivity results, antibiotics were empirically replaced with cefixime (10 mg/kg, q12h, Cefixime cap., Nelson, Korea). Additional drugs, including famotidine (0.5 mg/kg, q12h, PO famotidine, Hanmi Pharm, Korea), metronidazole (10 mg/kg, q12h, PO, Flasinyl Tab., HK Inno. N Corp.), gabapentin (10 mg/kg, PO, q12h) and streptokinase (0.05 T/kg, PO, q12h), were given twice a day for seven days.
After surgery, the patient’s walking ability and condition were check intermittently. The patient’s appetite was good on the day after surgery and a knuckling sign in the left hind limb was observed intermittently on the third day after surgery. The patient could walk independently enough to bear weight on both hind limbs. On the eighth day after the surgery, MRI was performed under the same anaesthesia scheme. All epidural suppurative lesions that were compressing the spinal cord disappeared (Fig 5A and B).
SEE is a serious neurological disease that is caused by the accumulation of suppurative substances outside the dura mater of the spinal canal. In another study, computed tomography confirmed the presence of an abscess in the epidural space of the cervical spine. The problem was caused by a scratch during surgery
(Granger et al., 2007). In addition, there were cases in which bacteria invaded the epidural space due to the hematogenous spread of infection, contiguous infections involving the adjacent tissues, direct inoculation and migration of foreign bodies
(Stefani et al., 2008; Trebacz et al., 2013; Monteiro et al., (2016); Woodruff et al., (2019); Guo and Lu, 2020).
In the present study, it was considered that purulent exudate was induced by a
Staphylococcus aureus invasion of a spinous process fracture of the first lumbar vertebrae. In other cases of a spinal epidural abscess presenting concurrently with osteomyelitis, although
Staphylococcus aureus was isolated from the resected soft tissue and was sensitive to fluoroquinolones and clindamycin, the infection was treated with oral enrofloxacin and oral clindamycin for 3 days
(Rapoport et al., 2016). In this study,
Staphylococcus aureus was isolated only in the epidural space between the thirteenth thoracic vertebra and the first lumbar vertebra and there was no invasion outside the spinal cord. Although there were no changes in CBC indicating toxicity, neutrophilia leukocytosis was confirmed and there were no specific findings in the serum chemistry analysis. Antibiotics were administered based on the results of the sensitivity tests involving bacteria that were isolated from the aspiration of 3 of 5 dogs with an epidural abscess and a diagnosis of disc spondylitis, prostatitis and dermatitis. Two dogs received conventional primary care and were cured within 2 weeks without surgical treatment
(Monteiro et al., 2016). However, in this case, since no other infectious diseases were found in the other area, microbiological tests were performed using the results of the antibiotic sensitivity tests that were administered during the surgical intervention and suppurative substances in the epidural space were treated by hemilaminectomy. On the third day after surgery, there was no problem in daily life.
SEE in cats can cause pressure atrophy of the vertebrae and serious neurological disorders, but even if treatment is not started early, the condition may not progress right away or have a poor prognosis
(Miki et al., 2022). In this case, although PDS and gabapentin were prescribed at the first presentation to resolve the compression of the spinal cord and neuropathic pain, it was not fundamentally successful because antibiotics could not be taken for 6 months. At the time of presentation, the patient was found to have an intermittent knuckling sign, mild ataxia and decreased proprioceptive response in the left hindlimb. Six months after the first diagnosis and despite the clinical symptoms becoming more serious than before, surgical intervention and good adherence to an effective antibiotic regimen improved the prognosis.
