An 8.5 yr MN Terrier Mix presented on appointment to our Neurology service for progressive pain. He was diagnosed with back pain by his primary veterinarian a month earlier. At that time was started on gabapentin and prednisone.

The patient re-presented to his primary veterinarian a few weeks later persistently painful and with a fever. He was started on oral doxycycline to cover for tickborne disease and his prednisone dose was increased. He continued to become progressively painful and unwilling to walk on his own. At the time of his scheduled Neurology appointment, he needed to be carried outside to use the bathroom and was biting his owners with any handing (which was very unusual for him).

On examination the patient was extremely fractious, vocalizing, and resistant to any handling. He was short-strided in the pelvic limbs with a left pelvic limb lameness, febrile (103 F), and painful on left hip extension.

Due to the severity of his clinical signs he was admitted for immediate further testing. Radiographs of the spine were concerning for bony lysis at the lumbosacral junction, and thoracolumbar MRI confirmed severe lumbosacral diskospondylitis with osteomyelitis, cellulitis, and meningitis. Oral cephalexin was started, and his owners reported mild improvement in his pain at home after several doses.

A blood culture and brucella AGID were negative. A urine culture revealed a proteus mirabilis infection which had decreased sensitivity to cephalexin. Oral cefpodoxime was started, and cephalexin discontinued based on his urine culture results. This medication change lead to more rapid and complete neurological improvement at home.  As of the time of publication the patient is neurologically normal, several months into antibiotic treatment.

Figure 1: Spinal radiograph (magnified to highlight the lumbosacral disc space)

Ventral remodeling at the level of the lumbosacral disc space. The lumbosacral endplates are concerning for early lysis (yellow arrow)

Figure 2: Sagittal T2-weighted imaging of the lumbar spine

The yellow arrows highlight the lumbosacral disc which is severely hyperintense and abnormal in shape. The abnormal hyperintense content protrudes into the lytic vertebral endplates. The red arrow highlights a thickened urinary bladder with a gas bubble is noted in the apex.

Figure 3: Sagittal (left) and Transverse (right) T1-weighted post-contrast images at the level of the lumbosacral junction

The lumbosacral disc and associated abnormal material are highly contrast enhancing (red arrow). The transverse image highlights the contrast enhancement of the annulus and thickened meninges (red arrows). There is no obvious extradural compression at this site.

Figure 4: Patient on recheck had an unremarkable neurological examination and his previous fractious behavior had resolved

Clinically relevant facts:

• L7-S1 is most common site for diskospondylitis in dogs. Bony infection (diskopondylitis) and neoplasia (osteosarcoma) should be primary differentials for dogs with severe spinal pain and minimal neurological deficits.

• Staphylococcus spp are the most common etiology for canine diskospondylitis, therefore oral cephalexin is recommended while blood/urine cultures and brucella testing are pending. When treating diskospondylitis every 8 hour cephalexin dosing is recommended.

• The urinary tract is the most common source of infection, therefore blood and

urine cultures are recommended at the time of diagnosis. Brucella AGID testing is also recommended due to the zoonotic potential. Reportedly about 50% of diskospondylitis cases will have negative cultures.

• Corticosteroid therapy is associated with neurological worsening in dogs with diskospondylitis, and can predispose to the development of empyema and/or pathological fracture.

• Treatment for diskospondylitis is recommended for a minimum of 6 months before tapering antibiotics is recommended.

• Radiographic evidence of diskospondylitis can be diagnostic, however information about the number of sites involved and any concurrent extradural spinal cord compression will offer valuable prognostic information and may alter the treatment plan. It should also be noted that radiographic evidence often lags behind clinical signs. Repeat spinal radiographs 4 weeks following initial presentation is warranted in dogs suspicious for diskospondylitis who are unable to pursue advanced imaging.

Authored by: Amanda Landry, DVM, DACVIM (Neurology)