What Is Your Neurologic Diagnosis?

Mariana Vigeral Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.

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Stephanie A. Thomovsky Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.

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Chee Kin Lim Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.

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R. Timothy Bentley Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.

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A 7-year-old 54.5-kg (119.9-lb) neutered male Labrador Retriever was evaluated because of a sudden onset of paraplegia. Six days earlier, the dog was observed to be dragging its right pelvic limb. The dog had a history of left shoulder joint osteoarthritis and idiopathic epilepsy; epilepsy was currently being treated with phenobarbital. There was no known history of trauma, and the owner reported that the dog had no signs of pain. Physical examination revealed a rectal temperature of 38.2°C (100.7°F) and a heart rate of 100 beats/min. The dog was panting, and signs of pain were elicited only on manipulation of the left shoulder joint. Previous diagnostic findings included moderate anemia (Hct, 29.9%; reference range, 37% to 55%), mild neutrophilia (14.1 × 103 neutrophils/μL; reference range, 3 × 103 neutrophils/μL to 12 × 103 neutrophils/μL), and mild hyperglobulinemia (4.0 g/dL; reference range, 1.7 to 3.8 g/dL).

What is the problem? Where is the lesion? What are the most probable causes of this problem? What is your plan to establish a diagnosis? Please turn the page.

Assessment

Anatomic diagnosis

ProblemRule out location
Pelvic limb paraplegiaT3-L3 or L4-S1 spinal cord lesion
Normal pelvic limb reflexes in a paraplegic dogT3-L3 spinal cord lesion
Cutaneous trunci reflex absent caudal to the T10 vertebra bilaterallyLesion in the region of the T8 and T9 vertebrae
Inability to attain sternal recumbency after being placed in lateral recumbencyCaudal cervical or cranial thoracic spinal cord lesion, vestibular lesion, or problem related to shoulder joint osteoarthritis

Likely location of 1 lesion

A lesion within the T3 through L3 segments of the spinal cord was suspected because the pelvic limb reflexes were normal yet paraplegia was observed (upper motor neuron paraplegia). The dog's inability to attain sternal recumbency from a laterally recumbent position was suspected to be secondary to shoulder joint osteoarthritis, but this problem can be associated with spinal cord lesions in the caudal cervical or cranial aspect of the thoracic vertebral column.

Etiologic diagnosis—Differential diagnoses for the dog's apparently nonpainful T3-L3 myelopathy included neoplasia (extradural, intradural-extramedullary, or intramedullary) or fibrocartilaginous emboli. Of the possible neoplastic spinal cord lesions, the most likely location of a tumor that would result in spinal hyperesthesia would be extradural. Differential diagnoses that were considered less likely because of the lack of signs of pain were intervertebral disk disease, diskospondylitis, empyema, vertebral fracture or luxation, and meningomyelitis.

Diagnostic test findings—The dog was referred for further evaluation 5 days later. A repeated CBC and serum biochemical analysis were performed to evaluate for any changes associated with the sudden onset of paraplegia. Results indicated that the dog had mild hyperproteinemia (9 g/dL; reference range, 6 to 8 g/dL), moderate anemia (RBC count, 4.05 × 106 RBCs/μL [reference range, 5.50 × 106 RBCs/μL to 8.50 × 106 RBCs/μL]; Hct, 26.8%; and hemoglobin concentration, 9 g/dL [reference range, 12 to 18 g/dL]), mild leukocytosis (17.1 × 103 WBCs/μL; reference range, 6 × 103 WBCs/μL to 17 × 103 WBCs/μL) characterized by moderate neutrophilia (15 × 103 neutrophils/μL; reference range, 3 × 103 neutrophils/μL to 12 × 103 neutrophils/μL), and lymphopenia (0.7 × 103 lymphocytes/μL; reference range, 1.0 × 103 lymphocytes/μL to 5.0 × 103 lymphocytes/μL). Urinalysis revealed moderate proteinuria (1+), bilirubinuria (2+), hematuria (2+), and trace bacteriuria with a moderate number of inflammatory cells. Urine specific gravity was 1.022 (reference range, 1.010 to 1.030). The dog was afebrile, and heart and respiratory rates were within reference ranges.

Survey radiography of the thorax revealed irregularities in the caudal endplate of the T5 vertebra and cranial endplate of the T6 vertebra, shortening of the T5 and T6 vertebral bodies, and narrowing and poor definition of the T5–6 intervertebral disk space (Figure 1). The most likely radiologic diagnosis for these findings was diskospondylitis with secondary compression fractures. Vertebral neoplasia was considered less likely because the bony lesions involved 2 adjacent vertebral endplates and were centered around the intervertebral disk space.1 Magnetic resonance imaging of the thoracic and lumbar portions of the vertebral column was performed to further assess the spinal cord and determine the cause of paraplegia. Typically, dogs with diskospondylitis have spinal hyperesthesia rather than paraplegia2; thus, MRI was pursued to determine whether there was a secondary cause of paraplegia in this case.

Figure 1—
Figure 1—

Lateral survey radiographic views of the thoracic vertebral column of a 7-year-old dog that was evaluated because of a sudden onset of paraplegia. A—Image obtained at the time of initial diagnosis. The caudal endplate of the T5 vertebra and cranial endplate of T6 vertebra are irregular with foreshortening of both vertebral bodies and loss of the intervertebral disk space. The locations of the T5 and T6 vertebrae are indicated by the asterisk. B—Image obtained 8 months after initial diagnosis. There is shortening of the T5 and T6 vertebrae with an ill-defined, thin, irregular lucent line between the vertebrae. This lucent line is in the location of the intervertebral disk space. In this location, there is well-defined bridging bone ventral to the vertebral bodies. Increased bone opacity at the level of the T5–6 intervertebral foramina and facet joints is evident.

Citation: Journal of the American Veterinary Medical Association 253, 9; 10.2460/javma.253.9.1117

Magnetic resonance imaging was performed with a 1.5-T unita to obtain T2-weighted sagittal, dorsal, and transverse images; T1-weighted sagittal and transverse images; and postcontrast T1-weighted sagittal, dorsal, and transverse images. The MRI images (Figure 2) confirmed shortening of the T5 and T6 vertebral bodies and loss of the T5–6 intervertebral disk space. There were irregular T2-weighted hyperintense (relative to the spinal cord) foci within the caudal endplate of the T5 vertebra and the cranial endplate of the T6 vertebra. These irregular foci were iso- to hypointense in T1-weighted images with moderate and heterogeneous enhancement on postcontrast T1-weighted images. The T1-weighted and T2-weighted hypointense proliferative new bone was present at the T5 and T6 vertebral endplates, extended dorsally into the ventral aspect of the spinal canal, and caused mild ventral extradural compression of the spinal cord. The proliferative new bone also extended dorsolaterally into both the T5 and T6 intervertebral foramina and ventrally along the ventral margin of the T5 and T6 vertebral bodies. These findings were consistent with an aggressive, mixed osteolytic and osteoblastic lesion involving the adjacent T5 and T6 vertebral endplates with secondary compression fracture, most likely attributable to diskospondylitis.

Figure 2—
Figure 2—

Magnetic resonance images of the dog's thoracic vertebral column at the level of T5–6. This montage includes T2-weighted sagittal (A) and transverse (D) images, T1-weighted sagittal (B) and transverse (E) images, and postcontrast T1-weighted sagittal (C) and transverse (F) images. In panels A though C, the asterisk denotes the location of the T5 and T6 vertebrae; in panels D through F, the arrowheads denote the ventral aspect of the vertebral bodies.

Citation: Journal of the American Veterinary Medical Association 253, 9; 10.2460/javma.253.9.1117

Blood samples were obtained from the jugular and left saphenous veins for bacterial culture; cultures yielded no bacterial growth. A urine sample was collected via catheterization for culture, which yielded growth of Staphylococcus pseudintermedius (≥ 105 CFUs/mL). Results of antimicrobial susceptibility testing indicated that the bacterium was susceptible to tested drugs. Fine-needle aspiration of the intervertebral disk space was not pursued because of the proximity of the pleural space and the high risk of pneumothorax.

The dog was treated with enrofloxacin and cefazolin while urine culture results were pending. After 5 days of IV administration of antimicrobials, the dog was transitioned to oral administration of enrofloxacin for an additional 24 hours prior to being discharged from the hospital. The owner was instructed to treat the dog orally with cephalexin and ciprofloxacin. Ciprofloxacin was chosen over enrofloxacin because of client cost concerns. Therapeutic laser treatments were performed daily on the dog's left shoulder joint during hospitalization for a total of 5 treatments, and the dog was treated orally with tramadol, gabapentin, and deracoxib. Treatment with phenobarbital was continued because of the dog's idiopathic epilepsy. Administrations of tramadol and gabapentin were discontinued 3 weeks after initiation of treatment.

The owner was instructed to provide the dog with strict cage rest and controlled physical rehabilitation. The dog was also to be taken to a physical rehabilitation specialist for laser treatment of the shoulder joint and underwater treadmill exercise for a total of 4 sessions. The owner was also instructed on how to catheterize the dog's urinary bladder in a sterile manner at home twice daily. Within a week, the dog was able to consciously urinate at home and no longer required intermittent catheterization. Eight months after initiating antimicrobial treatment, the dog was fully ambulatory with mild paresis and proprioceptive ataxia. At this time, a CT scan including multiplanar reformatted images of the thoracic and lumbar portions of the vertebral column revealed resolution of the diskospondylitis and bony lesion (Figure 3). Cross-sectional CT of the vertebral column allowed easy visualization of the vertebral endplates and unlike recheck MRI, sedation could be used. Following the CT scan, oral administrations of ciprofloxacin and cephalexin were discontinued.

Figure 3—
Figure 3—

Sagittal multiplanar reformatted CT image of the dog's thoracic vertebral column in a bone window (window level, 300; window width, 1,500) obtained 8 months after initiation of antimicrobial treatment. Notice the compression fracture of the T5 and T6 vertebral bodies with a diminished T5–6 intervertebral disk space (asterisk). The opposing margins of the T5 and T6 vertebral bodies are irregular and sclerotic with smoothly marginated ventral spondylosis deformans.

Citation: Journal of the American Veterinary Medical Association 253, 9; 10.2460/javma.253.9.1117

Comments

Diskospondylitis is an infection (bacterial or fungal) of the endplates of 2 adjacent vertebrae and the associated intervertebral disk space. It commonly affects middle-aged to older, large-breed dogs. Fever and spinal hyperesthesia are the most common clinical signs.2 Presumptive diagnosis of diskospondylitis can be made on the basis of survey radiographic views of the vertebral column when a mixture of lysis and proliferation of the vertebral endplates is observed.3 At early stages in the infection process, lesions may not be apparent radiographically; CT and MRI are required for increased sensitivity for detection.1,3,4 Common MRI and CT findings associated with diskospondylitis include erosion and irregularities of vertebral endplates with narrowing of the intervening intervertebral disk space.3 This disease process can lead to collapse of the disk and, in rare cases, concurrent spinal cord compression.3 Common vertebral body MRI findings include hypointensity on T1-weighted images, hypointensity on T2-weighted images, and moderate enhancement on postcontrast images.1 Affected intervertebral disks are commonly isointense on T1-weighted images and hyperintense on T2-weighted images and have marked enhancement on postcontrast images.1 In dogs with diskospondylitis, destruction of cortical bone margins and disruption of cortical bone continuity are the most common features detectable by advanced imaging.1 Early bone lysis can also be detected by CT imaging.4 The severity of spinal cord compression observed on all images can be directly correlated with the severity of neurologic deficits.3

Neoplasia, particularly vertebral neoplasia, commonly affects middle-aged to older dogs. Common signs of vertebral neoplasia include signs of pain and mild neurologic deficits.5 The main radiographic change associated with vertebral neoplasia is bone lysis without proliferation.5 In general, vertebral tumors more commonly involve 1 vertebral body1 rather than the endplates of adjacent vertebrae, as observed in the dog of the present report. In cases of neoplasia, the intervertebral disk space is typically not affected.1 That being said, in rare situations, vertebral tumors may lead to destruction of adjacent vertebral endplates in addition to collapse of the disk space.5

Given the radiographic lesions observed in the case described in the present report, diskospondylitis with secondary compression fracture causing shortening of the adjacent vertebral bones and leading to the absence of a visible disk space was considered the most likely diagnosis. Clinically, the dog's signs did not clearly support a diagnosis of diskospondylitis; the patient did not have obvious signs of spinal hyperesthesia and, on initial examination, was afebrile with minimal evidence of inflammation (as determined by results of a CBC). Magnetic resonance imaging findings confirmed that there was active lysis and inflammation of the caudal T5 and cranial T6 vertebral endplates. Ventral extradural compression of the spinal cord secondary to extensive proliferation of new bone into the spinal canal and secondary vertebral compression fracture were also observed. The irregularly hyperintense areas of the caudal endplate of the T5 vertebra and the cranial endplate of the T6 vertebra on T2-weighted images suggested acute and active diskospondylitis.1 Radiography of the affected portion of the vertebral column every 2 to 4 months with strict adherence to medical treatment was recommended to determine progression of disease. For this dog, the treatment outcome was favorable.

Footnotes

a.

Signa LX 9.0 unit, General Electric Co, Milwaukee, Wis.

References

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  • 3. Harris JM, Chen AV, Tucker RL, et al. Clinical features and magnetic resonance imaging characteristics of diskospondylitis in dogs: 23 cases (1997–2010). J Am Vet Med Assoc 2013;242:359365.

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  • 4. Kirberger RM. Early diagnostic imaging findings in juvenile dogs with presumed diskospondylitis: 10 cases (2008–2014). J Am Vet Med Assoc 2016;249:539546.

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