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Kelli N. Beavers Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.

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Charles T. McCauley Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.

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Nathalie Rademacher Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.

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History

An 18-year-old warmblood gelding was referred for evaluation of a fluid-filled soft tissue swelling in the cranial cervical region immediately caudal to the region between the frontal bone and temporal fossa (ie, the poll). The soft tissue swelling had been present for approximately 1 year.

Palpation of the soft tissue swelling had always resulted in signs of pain. The referring veterinarian performed a centesis of the swelling on 2 occasions; each time a thin, yellow, slightly turbid fluid was removed, only to have the fluid-filled swelling return. The most recent centesis was performed approximately 60 days prior to referral. At that time, a fluid sample was submitted for bacterial culture and antimicrobial susceptibility testing. The swelling was then injected with corticosteroids.

Bacterial culture results of the fluid sample were positive for Staphylococcus spp. On the basis of susceptibility test results, antimicrobial treatment was initiated. One week following the injection of corticosteroids, the swelling substantially increased in size and appeared to be progressively more painful on palpation. The horse was then referred for further evaluation of the mass.

At hospital admission, a turgid and fluctuant swelling was evident bilaterally at the level of the first and second cervical vertebral bodies, with the swelling on the left side more prominent than on the right. Palpation of the soft tissue swelling resulted in signs of pain. The horse held its head at or just above the level of the shoulder and would intermittently turn its head, as if in discomfort. No other abnormalities were observed on physical examination. A complete radiographic series including lateral, oblique, and dorsoventral projections of the cranial cervical vertebrae was obtained (Figure 1; only the lateral image is provided).

Figure 1—
Figure 1—

Right-to-left lateral radiographic view of the caudal occipital and cranial cervical area of an 18-year-old warmblood gelding evaluated because of a fluid-filled soft tissue swelling in the cranial cervical region immediately caudal to the region between the frontal bone and temporal fossa (ie, the poll).

Citation: Journal of the American Veterinary Medical Association 251, 2; 10.2460/javma.251.2.149

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →

Diagnostic Imaging Findings and Interpretation

A focal, well-defined, oval soft tissue swelling is evident dorsal to the occipital bone and first cervical vertebra (Figure 2). A moderate amount of amorphous mineralization is associated mainly with the cranial and dorsal portion of the soft tissue swelling. Radiographic findings are suggestive of fluid and dystrophic mineralization involving the cranial nuchal bursa. There is no radiographic evidence of secondary osseous changes in the occipital bone or cervical vertebrae.

Figure 2—
Figure 2—

Same radiographic image as Figure 1. Noticed the well-defined, oval soft tissue swelling (white arrows) with associated mineralization. The soft tissue swelling is dorsal to the caudal portion of the occipital bone and the first cervical vertebra.

Citation: Journal of the American Veterinary Medical Association 251, 2; 10.2460/javma.251.2.149

Ultrasonography of the affected area was performed to evaluate the cranial nuchal bursa, including the fluid within the bursa, the nuchal ligament, and the dorsal surface of the first and second cervical vertebrae (Figure 3). A large, oval, well-defined, heterogeneous mass ventral to the nuchal ligament, measuring at least 6.6 cm in depth and with a wall thickness of 0.5 cm was identified. Loculated areas of hypoechoic fluid were present within the mass, in addition to multiple hyperechoic, distally shadowing foci of various sizes and shapes consistent with mineralization. The nuchal ligament maintained normal fiber orientation, echogenicity, and margins.

Figure 3—
Figure 3—

Longitudinal ultrasonographic image of the radiographically evident lesion dorsal to the first cervical vertebra of the horse in Figure 1. A well-defined encapsulated ovoid structure (beyond the field of view included in this image) is seen ventral to the nuchal ligament (not depicted), which is unremarkable. This encapsulated structure is of mixed echogenicity; loculated areas of hypoechoic fluid are present in addition to multiple hyperechoic, distally shadowing foci of various sizes and shapes, consistent with mineralization. Image obtained with a 10-MHz linear transducer.

Citation: Journal of the American Veterinary Medical Association 251, 2; 10.2460/javma.251.2.149

Differential diagnoses based on diagnostic imaging findings included chronic severe cranial nuchal bursitis (of septic or nonseptic origin), abscess, necrotic granuloma, or necrotic tumor. A specific differential diagnosis of infectious origin with important zoonotic potential in this horse was brucellosis. Infections in horses with Brucella abortus can result in cranial nuchal bursitis, also known as poll evil, as well as other bursal infections and vertebral osteomyelitis.1

Treatments and Outcome

The diagnosis of cranial nuchal bursitis was confirmed by ultrasonographically assisted bursoscopy. Bursoscopy has been reported to be the definitive diagnostic and therapeutic technique for cranial nuchal bursitis.2 During bursoscopy, a sample for aerobic bacterial culture was obtained, which yielded no growth, and the bursa was thoroughly debrided and lavaged.

Comments

The cranial nuchal bursa is a subligamentous bursa that is positioned between the funicular portion of the nuchal ligament and the dorsal arch of the first cervical vertebra.3 As with other bursae, it is found in an area of pressure or friction and serves to evenly distribute the pressure between the nuchal ligament and first cervical vertebra. It is described as being flat to comma-shaped, following the contour of the nuchal ligament, and contains a very small amount of fluid.4 Under normal circumstances, the cranial nuchal bursa is not evident on routine radiographic imaging of the cranial cervical region. The cranial nuchal bursa in clinically normal horses can, however, be consistently imaged by MRI or ultrasonography providing important information in horses with clinical signs of bursitis.4 When diseased, the cranial nuchal bursa becomes distended with fluid, often extending beyond its typical margin from the middle third of the first cervical vertebra caudally to the articulation between the first and second cervical vertebrae.4 In addition, there is thickening and proliferation of its synovial lining and the accumulation of fluid ranging in consistency from serous to purulent. This becomes apparent radiographically as a round to ovoid, increased soft tissue opacity dorsal to the first and second cervical vertebrae, sometimes containing variable mineral opacities.4 Radiography was important for the initial diagnosis in the horse of the present report as it highlighted the dystrophic mineralization, which has been reported for horses with cranial nuchal bursitis.2 Radiographic findings were also used to rule out an osseous abnormality in the cranial cervical vertebrae as the source of pain.

Ultrasonography was useful in the case described in the present report. It allowed for characterization of the fluid present in the bursa, assessment of the integrity of the nuchal ligament, determination of the thickness of the bursal wall, measurement of the depth from the surface of the skin to the bursa, and evaluation of the surface of the first and second cervical vertebrae. In addition, although an approach to the cranial nuchal bursa has been described by use of superficial landmarks, ultrasound guidance was used to ensure proper placement of the endoscope for bursoscopy in the horse of the present report. This has been suggested to be important in chronic disease as the anatomy may be distorted, making assessment of superficial landmarks difficult. Cranial nuchal bursitis of nonseptic origin and its diagnosis and treatment have been recently reported by Garcia-Lopez et al.2 In horses with clinical signs of cranial nuchal bursitis, which include swelling and signs of pain, the use of radiography and ultrasonography can assist in the diagnosis, especially in horses with subtle clinical signs. The outcome for surgical treatment is excellent, with all 4 affected horses in the report by Garcia-Lopez et al2 achieving complete resolution of clinical signs.

References

  • 1. Sellon DC, Nicoletti PL. Brucellosis. In: Sellon DC, Long MT, eds. Equine infectious diseases. St Louis: Saunders Elsevier, 2014; 337339.

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  • 2. García-López JM, Jenei T, Chope K, et al. Diagnosis and management of cranial and caudal nuchal bursitis in four horses. J Am Vet Med Assoc 2010; 237: 823829.

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  • 3. Constantinescu GM, Constantinescu IA. Clinical dissection guide for large animals: horse and large ruminants. Ames, Iowa: Iowa State Press, 2004; 322.

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  • 4. Abuja GA, García-López JM, Manso-Díaz G, et al. The cranial nuchal bursa: anatomy, ultrasonography, magnetic resonance imaging and endoscopic approach. Equine Vet J 2014; 46: 745750.

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  • Figure 1—

    Right-to-left lateral radiographic view of the caudal occipital and cranial cervical area of an 18-year-old warmblood gelding evaluated because of a fluid-filled soft tissue swelling in the cranial cervical region immediately caudal to the region between the frontal bone and temporal fossa (ie, the poll).

  • Figure 2—

    Same radiographic image as Figure 1. Noticed the well-defined, oval soft tissue swelling (white arrows) with associated mineralization. The soft tissue swelling is dorsal to the caudal portion of the occipital bone and the first cervical vertebra.

  • Figure 3—

    Longitudinal ultrasonographic image of the radiographically evident lesion dorsal to the first cervical vertebra of the horse in Figure 1. A well-defined encapsulated ovoid structure (beyond the field of view included in this image) is seen ventral to the nuchal ligament (not depicted), which is unremarkable. This encapsulated structure is of mixed echogenicity; loculated areas of hypoechoic fluid are present in addition to multiple hyperechoic, distally shadowing foci of various sizes and shapes, consistent with mineralization. Image obtained with a 10-MHz linear transducer.

  • 1. Sellon DC, Nicoletti PL. Brucellosis. In: Sellon DC, Long MT, eds. Equine infectious diseases. St Louis: Saunders Elsevier, 2014; 337339.

    • Search Google Scholar
    • Export Citation
  • 2. García-López JM, Jenei T, Chope K, et al. Diagnosis and management of cranial and caudal nuchal bursitis in four horses. J Am Vet Med Assoc 2010; 237: 823829.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3. Constantinescu GM, Constantinescu IA. Clinical dissection guide for large animals: horse and large ruminants. Ames, Iowa: Iowa State Press, 2004; 322.

    • Search Google Scholar
    • Export Citation
  • 4. Abuja GA, García-López JM, Manso-Díaz G, et al. The cranial nuchal bursa: anatomy, ultrasonography, magnetic resonance imaging and endoscopic approach. Equine Vet J 2014; 46: 745750.

    • Crossref
    • Search Google Scholar
    • Export Citation

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