What Is Your Neurologic Diagnosis?

Leanne Shutt Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.

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Taya M. Marquardt Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.

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Kelsey A. Cline Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.

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Amanda R. Taylor Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.

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A 10-year-old 4.36-kg (9.59-lb) spayed female domestic longhair cat was evaluated because of pelvic limb paresis of 7 weeks' duration. The cat was kept indoors with outdoor access, and had previously been apparently healthy. The owners first found the cat nonambulatory in their yard 2 hours after being let outside and immediately took it to the referring veterinarian. Radiographic findings suggested a possible pelvic fracture, but the cat had adequate urinary continence. Cage rest was recommended. After minimal improvement over time, a referral examination was arranged. The physical examination was limited owing to the cat's temperament. The cat would bear weight on both pelvic limbs; when supported to ambulate, the thoracic limb movement appeared normal but the pelvic limbs angled to the left with decreased movement. A neurologic examination was performed.

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
Nonambulatory paraparesis; right-sided paresis more severe than left-sided paresisT3-L3 spinal cord segments
Absent postural reactions with proprioceptive deficits in the pelvic limbsT3-L3 spinal cord segments
Increased extensor tone in pelvic limbsT3-L3 spinal cord segments

Likely location of 1 lesion

Right-sided lesion within the T3-L3 spinal cord segments

Etiologic diagnosis—Differential diagnoses considered for the cat included trauma, vascular event (fibrocartilaginous embolism [FCE], ischemic myelopathy, or hemorrhage), intervertebral disk extrusion, and neoplasia. Diagnostic testing included a CBC, serum biochemical analysis, urinalysis, and bacterial culture of urine (to assess for signs of systemic infection or inflammation or concurrent disease). Three-view thoracic radiography (to screen for pulmonary metastasis) and vertebral column radiography (to rule out the presence of fractures, osteolytic neoplasia, luxations or subluxations, or evidence of intervertebral disk disease) were performed. Ultrasonographya of the abdomen was performed to assess abdominal organs. Magnetic resonance imaging of the T3 through L3 spinal cord segments and surrounding tissues was performed with a 1.5-T scannerb and a human spine coil (to assess the spinal cord parenchyma for evidence of trauma, ischemia, hemorrhage, or neoplasia). The following MRI sequences were acquired: sagittal and transverse T2-weighted turbo spin-echo (repetition time [TR], 4,000.0 to 5,948.0 milliseconds; echo time [TE], 115.5 to 119.7 milliseconds; slice thickness, 3.0 mm); sagittal short tau inversion recovery (TR, 4,362.0 milliseconds; TE, 16.8 milliseconds; slice thickness, 3.0 mm); sagittal half-Fourier acquisition single-shot turbo spin-echo (TR, 60,000.0 milliseconds; TE, 614.1 milliseconds; slice thickness, 2.0 mm); transverse fluid attenuating inversion recovery (TR, 6,000.0 milliseconds; TE, 110.4 milliseconds; slice thickness, 5.0 mm); transverse T1-weighted turbo spin-echo precontrast agent administration and transverse, dorsal, and sagittal T1-weighted postcontrast agent administration (TR, 500 to 995.0 milliseconds; TE, 9.8 to 10 milliseconds; slice thickness, 4.0 mm); transverse T2*-weighted gradient echo (TR, 1,188.0 milliseconds; TE, 23.5 milliseconds; slice thickness, 4.0 mm); and transverse T1-weighted post-contrast agent administration with fat saturation (TR, 1,235.0 milliseconds; TE, 9.9 milliseconds; slice thickness, 4.0 mm). Postcontrast agent administration images were obtained following IV administration of 0.1 mmol of gadoteridolc/kg (0.045 mmol/lb). A CSF sample was collected for analysis (to screen for evidence of inflammation, neoplasia, or trauma). An occult feline heartworm antigen-antibody test (to determine heartworm disease status) was performed.

Diagnostic test findings—The CBC did not reveal any important abnormalities. Serum creatine kinase activity was 618 U/L (reference interval, 100 to 250 U/L) and BUN concentration was 33.5 mg/dL (reference interval, 5 to 30 mg/dL); these findings were considered attributable to difficulty in blood sample collection and mild dehydration (prerenal azotemia), respectively. There were no other notable serum biochemical abnormalities. Analysis of a urine sample revealed a moderate number of RBCs (3+ on dipstick and 10 to 20 cells/field [400X] on sediment examination) with trace bacteria in the sediment. Bacterial culture of urine was negative for growth.

Thoracic radiography revealed a mild diffuse bronchial pattern throughout the lung parenchyma and mild cardiomegaly. Ventral spondylosis from the T11 vertebra to the L1 vertebra was identified on radiographic views of the vertebral column (Figure 1). Wedging of the intervertebral disk space was present at the levels of T11–12 and T12–13, and the vertebral canal was malaligned at T12–13. Abdominal ultrasonographic findings were normal. On sagittal MRI images, there was a large irregular lesion within the spinal cord parenchyma that extended the entire length of the L5 vertebral body. Compared with the appearance of gray matter, the lesion was hyperintense in all T2-weighted images and isointense in T1-weighted images (Figure 2). The lesion was associated with the gray matter and was more severe on the right side. Overlying the cranial half of the L4 vertebral body on the transverse gradient echo T2*-weighted images was a focal area of signal void on the right dorsal aspect of the spinal cord. On post-contrast agent administration images, there was heterogeneous, ill-defined contrast enhancement of the L5-associated lesion. In addition, there was a malalignment of the vertebral column at the T12-T13 junction. Overlying the thoracolumbar junction, there was mixed T2-weighted hyperintense–T1-weighted isointense signal (compared with that of normal muscle) within the epaxial muscles. Analysis of a CSF sample revealed macrophagic pleocytosis with 9 nucleated cells/μL. The macrophages contained proteinaceous debris with occasional erythrophagia. A moderate number of erythrocytes (2,490 RBCs/μL) was present. The result of the occult feline heartworm antigen-antibody test was negative.

Figure 1—
Figure 1—

Left lateral radiographic view of the thoracolumbar portion of the vertebral column of a cat with a 7-week history of pelvic limb lameness. Notice the ventral spondylosis of the T11, T12, T13, and L1 vertebrae; narrowing of the intervertebral disk space, vertebral foramen, and articular facets at T11–12 and T12–13; and malalignment of the vertebral canal, all suggestive of previous subluxation.

Citation: Journal of the American Veterinary Medical Association 251, 4; 10.2460/javma.251.4.395

Figure 2—
Figure 2—

Transverse T1-weighted precontrast agent administration (A), transverse T1-weighted postcontrast agent administration (B), and transverse T2-weighted (C) MRI images at the level of the L5 vertebral body in the cat in Figure 1. Notice a lesion within the central part of the cord that is associated with gray matter. It is hyperintense on the T2-weighed image; trace heterogeneous amounts of contrast agent are present in the otherwise isointense lesion on T1-weighted postcontrast agent administration images. These are all MRI characteristics commonly associated with an ischemic event.

Citation: Journal of the American Veterinary Medical Association 251, 4; 10.2460/javma.251.4.395

Comments

Animals that are allowed or kept outdoors are especially at risk for traumatic injuries as they are largely unattended and have more access to dangerous situations including proximity to moving vehicles. The cat of the present report was allowed outdoors and although its owners were not present to witness an injury, the cat likely was involved in a traumatic event.

Problems related to traumatic spinal cord injuries vary from vertebral fractures to vertebral luxations or subluxations to intervertebral disk extrusions, depending on the magnitude and direction of the applied force. As a result of any of these insults, there may be multiple lesions affecting the spinal cord or surrounding structures, including ischemia, compression, hemorrhage, and laceration.1

The signalment, history, and clinical signs in the case described in the present report were key pieces of information. The cat was found outside in an acutely nonambulatory condition. The clinical signs were asymmetric and apparently nonpainful. Throughout the 7-week period prior to the referral examination, the clinical signs minimally improved. On the basis of these facts and the absence of a compressive lesion on diagnostic images, the differential diagnosis list pointed to a few disease processes, namely trauma, a vascular event (FCE, other ischemic myelopathy, or hemorrhage), and neoplasia.2–6

Vertebral radiography and MRI revealed a T12–13 subluxation and a lesion within the epaxial muscles dorsal to this area.7 The signal changes within the muscle could have represented edema or fibrosis, consistent with subluxation. These combined findings were suggestive of a traumatic event.

The cat had a spinal cord parenchymal lesion over the L5 vertebral body identified via MRI, which was indicative of an ischemic event.8–11 Although a definitive diagnosis of FCE or ischemic myelopathy cannot be obtained without histologic examination of affected tissue, MRI findings can be extremely helpful in obtaining a presumptive antemortem diagnosis by providing supportive imaging characteristics and ruling out other causes.4,6,9,10 In the case described in the present report, the signal void over the L4 vertebral body on the T2*-weighted images likely represented hemorrhage.12 The erythrophagia detected in macrophages in the CSF sample also supported hemorrhage13 at an earlier time point.

For the cat of the present report, the occurrence of trauma that impacted the thoracolumbar area as well as the mid-lumbar area was considered likely. This trauma resulted in muscular damage and subluxation of the vertebral column, and may have caused an FCE or have ruptured spinal blood vessels. Given that a traumatic incident can be the cause of ischemic or hemorrhagic events, we speculated that the mid-lumbar portion of the spinal cord in the area became ischemic following interruption of blood supply secondary to trauma. In cases of ischemic events, the gray matter is more severely affected than the white matter, as in the cat of the present report, because of its greater metabolic demand.14 The asymmetry of the lesion and the resulting clinical signs would be explained by the asymmetric distribution of the blood supply of the spinal cord, if an ischemic event secondary to trauma had caused this lesion.15

For small animals with nonsurgical traumatic spinal cord injuries or ischemic myelopathy, supportive care is the mainstay of treatment.16–18 Actions such as regular urinary bladder expression, patient rotation to avoid development of pressure sores, administration of enemas, skin care, and provision of adequate nutrition may all be necessary.9,16 Prior to the referral examination, the cat of the present report had adequate urinary continence.

Physical therapy has been shown to have a positive effect on clinical outcomes of dogs with FCE-related myelopathy as it encourages neuronal plasticity and minimizes negative effects of immobilization (eg, muscle atrophy or joint contracture).2,16,18 For the cat of the present report, physical therapy was recommended but owner compliance was suboptimal. After 1 month of restricted exercise, the cat had returned to its normal level of activity. However, according to the referring veterinarian, the cat had regained ambulatory status but retained marked proprioceptive deficits.

Footnotes

a.

Philips iE33 xMATRIX Ultrasound System, Philips Medical Systems, Eindhoven, The Netherlands.

b.

Infinion 1.5-Tesla scanner with a human knee coil, Philips Medical Systems, Andover, Mass.

c.

Gadoteridol (Prohance), Bracco Diagnostics Inc, Township, NJ.

References

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