Discospondylitis (also spelled diskospondylitis) is an infection of the intervertebral disc and adjacent vertebral endplates. This condition represents a significant clinical entity in canine neurology and is commonly tested on the NAVLE.
Overview and Clinical Importance
Discospondylitis (also spelled diskospondylitis) is an infection of the intervertebral disc and adjacent vertebral endplates. This condition represents a significant clinical entity in canine neurology and is commonly tested on the NAVLE. The infection typically develops secondary to hematogenous spread of bacteria from distant sites, though direct inoculation and migrating foreign bodies are also recognized routes. Understanding the pathophysiology, clinical presentation, diagnostic approach, and treatment is essential for successful board examination performance and clinical practice.
Discospondylitis is predominantly a disease of dogs and is rare in cats. The condition carries significant morbidity if not diagnosed and treated promptly, potentially leading to permanent neurological dysfunction, pathologic fractures, or spinal cord compression. Early recognition and appropriate antimicrobial therapy are key to favorable outcomes.
High-YieldDiscospondylitis is one of the most common infectious causes of spinal pain in dogs. Always consider this diagnosis in any dog presenting with spinal hyperesthesia, especially if fever, weight loss, or reluctance to move is present. The L7-S1 junction is the most commonly affected site.
| Route |
Description and Examples |
| Hematogenous Spread |
Most common route. Bacteria spread from urinary tract infections, prostatic infections, endocarditis, dental disease, or skin infections via bloodstream to vertebral endplates |
| Migrating Foreign Body |
Plant awns (grass awns) that migrate through tissues. Typically target L2-L4 region. More common in certain geographic regions |
| Direct Inoculation |
Penetrating wounds, bite wounds (especially in cats), epidural injections, or surgical contamination following spinal procedures |
| Iatrogenic |
Post-surgical complication following spinal decompression surgery. Risk factors include obesity and large breed dogs |
Etiology and Pathophysiology
Routes of Infection
Discospondylitis typically starts in the vertebral endplate, then spreads to the adjacent intervertebral disc. The blood supply within the vertebral endplates consists of capillary beds with reduced blood flow velocity. Pores in the endplate that normally allow nutrient distribution also provide a route for organisms to enter the intervertebral disc. The minimal vascular supply of the intervertebral disc further enables infection within the disc space.
Routes of Infection and Sources
Causative Organisms
NAVLE TipBrucella canis accounts for less than 10% of discospondylitis cases, but ALL dogs with suspected discospondylitis should be tested due to its ZOONOTIC POTENTIAL. Brucella testing is especially important in intact dogs, those from the southeastern United States, and dogs with a history of breeding. Remember: Brucella is an intracellular organism with no curative treatment - infected dogs require lifelong antibiotic therapy and should be neutered.
| Organism Type |
Common Agents |
Clinical Notes |
| Bacterial (Most Common) |
Staphylococcus spp. (S. pseudintermedius, S. aureus) - 60% of cases
Streptococcus spp.
Escherichia coli
Brucella canis |
Staphylococcus is the most frequently isolated organism from blood cultures. Consider UTI as primary source |
| Fungal |
Aspergillus terreus
Aspergillus deflectus
Other Aspergillus spp. |
German Shepherd Dogs are predisposed due to IgA deficiency. Guarded prognosis. Screen with galactomannan antigen |
| Other Bacteria |
Enterococcus spp.
Pseudomonas aeruginosa
Salmonella spp.
Nocardia spp. |
Less common but should be considered in culture-negative cases or treatment failures |
Signalment and Breed Predispositions
Epidemiology
- Sex: Males are overrepresented (approximately 1.6:1 to 2:1 male to female ratio)
- Age: Median age is 7 years; most commonly affects dogs greater than 10 years of age. However, can occur at any age
- Size: Large and giant breed dogs are most commonly affected
- Species: Primarily a canine disease; rare in cats
Breed Predispositions
| Overrepresented Breeds |
Special Considerations |
| German Shepherd Dog |
Strongly predisposed to fungal (Aspergillus) discospondylitis due to IgA deficiency. Always screen with galactomannan antigen testing |
| Great Dane |
Giant breed predisposition; higher risk of post-surgical discospondylitis |
| Doberman Pinscher |
Commonly affected large breed |
| Boxer, Rottweiler, Labrador Retriever |
Frequently affected breeds in large studies |
| French Bulldog, English Bulldog |
Increasingly reported; possible association with spinal conformation |
Clinical Presentation
Primary Clinical Signs
Spinal hyperesthesia (pain) is the most common presenting complaint, occurring in over 80% of cases. Clinical signs are often progressive over weeks to months, though acute presentations can occur with pathologic fractures or sudden spinal cord compression.
High-YieldFever is NOT a consistent finding in discospondylitis - only 8-30% of dogs are febrile at presentation. A lack of fever should NOT rule out infectious etiology. Discospondylitis should always be considered in any dog with fever of unknown origin.
Neuroanatomical Localization Based on Lesion Site
NAVLE TipL7-S1 is the MOST COMMONLY affected site (approximately 27% of cases), followed by thoracolumbar junction. More than 40% of dogs have MULTIPLE lesions - always image the ENTIRE spine! The neuroanatomical localization may not match the most affected imaging site because not all lesions cause clinical signs.
| Sign Category |
Clinical Manifestations |
Frequency |
| Spinal Pain |
Hyperesthesia on palpation, reluctance to move, stiff gait, kyphosis or lordosis, crying out when picked up |
Greater than 80% |
| Constitutional Signs |
Fever (temperature greater than 103.5°F), lethargy, decreased appetite, weight loss |
Fever only 8-30% |
| Neurologic Deficits |
Ataxia, paresis (ambulatory or non-ambulatory), paralysis. Deficits correlate with lesion location |
Approximately 30% |
| Gait Abnormalities |
Stilted pelvic limb gait, shifting lameness (especially with lumbosacral involvement), reluctance to jump |
Common |
Diagnostic Approach
Diagnostic Imaging
Radiography
Spinal radiography remains an important screening tool for discospondylitis. However, radiographic changes typically lag behind clinical signs by 2-4 weeks (up to 6 weeks reported) because approximately 70% bone destruction must occur before changes are visible.
Advanced Imaging: CT and MRI
MRI is the GOLD STANDARD for diagnosing discospondylitis and can detect lesions earlier than radiography. Approximately 33% of dogs have NO radiographic evidence of disease but have lesions visible on MRI.
High-YieldThere is POOR agreement between radiographs and MRI for detecting discospondylitis. When radiographs are negative but clinical suspicion is high, pursue advanced imaging. MRI may detect lesions in dogs with normal radiographs AND normal CT.
Laboratory Diagnostics
NAVLE TipOrganism isolation FAILS in 50-60% of discospondylitis cases! If blood and urine cultures are negative and the patient is not responding to empirical therapy, consider fluoroscopically-guided disc aspiration for culture. Negative cultures should NOT preclude treatment.
| Lesion Location |
Expected Clinical Signs |
| Cervical (C1-C5) |
Cervical pain, tetraparesis with UMN signs in all four limbs, possible respiratory compromise with severe lesions |
| Cervicothoracic (C6-T2) |
LMN signs to thoracic limbs (decreased reflexes), UMN signs to pelvic limbs, cervical pain |
| Thoracolumbar (T3-L3) |
Back pain, paraparesis/paraplegia with UMN signs to pelvic limbs, normal thoracic limb function. MOST COMMON neuroanatomical localization (40%) |
| Lumbosacral (L4-S3) |
Lumbosacral pain, LMN signs to pelvic limbs (decreased reflexes, flaccid paralysis), fecal/urinary incontinence, tail weakness |
| L7-S1 (Most Common Site) |
Cauda equina syndrome: lumbosacral pain, stilted pelvic limb gait, shifting lameness, decreased patellar reflex, decreased anal tone, urinary/fecal dysfunction |
Treatment
Antimicrobial Therapy
Medical management with targeted antibiotic therapy is the mainstay of treatment. Since organism isolation fails in 50-60% of cases, empirical treatment with antibiotics that have good bone penetration and cover Staphylococcus/Streptococcus is acceptable and recommended.
Antibiotic Selection
Monitoring Treatment Response
- Clinical improvement: Expected within 1-2 weeks (resolution of fever, improved appetite, reduced pain)
- Radiographic monitoring: Recheck every 2-4 months. Changes lag behind clinical improvement by weeks to months
- Treatment duration: Continue antibiotics 2-4 weeks AFTER radiographic resolution AND clinical resolution
- Radiographic healing: Characterized by ankylosis (fusion) and replacement of lytic bone with osseous proliferation
- CRP monitoring: Return to normal CRP desired before discontinuing antibiotics
Adjunctive Therapy
High-YieldAVOID CORTICOSTEROIDS in discospondylitis! Prior steroid therapy is associated with an increased risk of progressive neurological deterioration (OR 4.7). Steroids may mask clinical improvement while allowing infection to progress.
| Radiographic Finding |
Description |
| Early Changes |
Collapsed or narrowed intervertebral disc space, subtle vertebral endplate irregularity, loss of sharp endplate margins |
| Classic Findings |
Osteolysis of adjacent vertebral endplates, sclerosis peripheral to lytic areas, irregular endplate margins with permeative lysis |
| Chronic/Healing |
Bridging spondylosis, vertebral body shortening, ankylosis (fusion) of adjacent vertebrae, smoothening of previously irregular margins |
| Severe Complications |
Pathologic fractures, vertebral subluxation, spinal instability |
Prognosis
Risk Factors for Relapse
- History of trauma (OR 9.0 - significantly increased relapse risk)
- Premature discontinuation of antibiotics
- Multifocal lesions
- Fungal etiology
- Inconsistent medication administration
| Modality |
Key Findings |
Advantages |
| MRI |
T2/STIR hyperintensity of disc and endplates
T1 hypointensity of affected structures
Contrast enhancement of endplates and soft tissues
Epidural extension visible |
Gold standard for diagnosis. Detects early disease. Shows spinal cord compression, epidural empyema, and soft tissue involvement |
| CT |
Endplate erosion and osteolysis
Periosteal proliferation
Vertebral body morphology changes
Vacuum phenomenon may be present |
Excellent bone detail. Detects subtle endplate changes. Useful for CT-guided biopsy. More available than MRI |
| Test |
Yield |
Common Findings |
Notes |
| Blood Culture |
27-40% |
Staphylococcus spp. most common (60%) |
Perform BEFORE starting antibiotics. Better yield if febrile |
| Urine Culture |
15-28% |
Staphylococcus, E. coli common |
UTI may be primary source. Always submit |
| Disc Aspirate/Culture |
41-43% |
Staphylococcus spp. (70%) |
Fluoroscopy or CT-guided. Higher yield than blood/urine |
| Brucella Serology |
7-10% positive |
RSAT, 2ME-RSAT, AGID, IFA |
ALWAYS test - zoonotic risk |
| Galactomannan Antigen |
90% sensitive |
Detects Aspergillus |
Essential for German Shepherds. Serum or urine |
| C-Reactive Protein |
Non-specific |
Elevated with inflammation |
More consistent than fever/leukocytosis. Monitor treatment response |
| Indication |
First-Line Agents |
Dosage |
Duration |
| Empirical (Culture Negative) |
Cephalexin (most common)
OR Amoxicillin-clavulanate |
Cephalexin: 30 mg/kg PO q8h
Amox-clav: 15 mg/kg PO q12h |
Minimum 6-8 months; often 6-12 months or longer |
| Brucella canis |
Doxycycline PLUS Enrofloxacin |
Doxycycline: 5 mg/kg PO q12h
Enrofloxacin: 10-20 mg/kg PO q24h |
LIFELONG - Brucella cannot be cured. Neuter patient |
| Fungal (Aspergillus) |
Itraconazole
OR Voriconazole
+/- Terbinafine |
Itraconazole: 5 mg/kg PO q24h
Voriconazole: 5 mg/kg PO q12h |
Minimum 6-12 months. Guarded prognosis |
| Treatment |
Indications and Notes |
| Analgesia |
Gabapentin, tramadol, and/or NSAIDs. Typically needed early in treatment to manage hyperesthesia |
| Exercise Restriction |
Cage rest or strict confinement for 4-6 weeks following diagnosis to prevent pathologic fractures |
| Surgical Intervention |
Indicated for: severe spinal cord compression, vertebral subluxation/instability, pathologic fractures, epidural empyema, failure of medical therapy. Procedures include decompression, debridement, and stabilization |
| Etiology |
Prognosis |
Key Points |
| Bacterial (Non-Brucella) |
Good to Excellent |
Most cases resolve with early, aggressive, prolonged antibiotic therapy. Relapses can occur if treatment is stopped too early |
| Brucella canis |
Fair (with lifelong treatment) |
Cannot be cured. Good quality of life achievable with lifelong antibiotics. Requires neutering and owner precautions due to zoonotic potential |
| Fungal (Aspergillus) |
Guarded to Poor |
Often disseminated at diagnosis. Treatment expensive and prolonged. Median survival approximately 226-531 days with treatment |