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History

4 year old male castrated La Mancha goat

• Dorsal cervical mass first appreciated 2 weeks prior to presentation

• Ataxia and abnormal head nodding behavior first noted 4 days prior to presentation

• Poor quality haircoat and underweight

• Bloodwork: Anemia (PCV: 18%) based on minimum database performed at presentation. Normal fibrinogen.

• Vital parameters within normal limits.

 

 

Radiographic Images

Lateral and DV radiograph of the cranial cervical spine

o Marked heterogeneous, amorphous mineralization of the dorsal and right-sided cervical soft tissues that measures approximately 20cmL x 5.6cm, extending from the occipital protuberance to the level of the mid body of C3

o Moderate associated soft tissue swelling; soft tissues dorsal to C2 most affected

o The mass appears continuous with the nuchal ligament caudally o Moderate irregular osteoproliferation (periosteal reaction vs enthesophytosis) of the caudal occiput and the craniodorsal aspect of C1 vs superimposition of previously described mineralization

Ultrasound Images

Ultrasound of the nuchal bursa

o The atlantal bursa is distended with a marked amount of heterogeneous, but generally hypoechoic material with innumerable small hyperechoic shadowing foci and anechoic fluid.

o Small hyperechoic shadowing foci are also noted within the nuchal ligament and the dorsal cervical musculature (semi spinalis capitus and rhomboideus muscles) with fiber disruption of these structures and interspersed poorly organized hypoechoic tissue.

o The primary differential based on imaging findings and patient history is dystrophic mineralization and bursitis secondary to chronic caprine arthritis-encephalitis (CAE) infection.

o Other considerations included parasitic infection/granuloma/abscess (eg. associated with onchocerca) or neoplasia (e.g. fibrosarcoma vs. extraskeletal osteosarcoma).

Outcome

o A fine needle aspirate of the mass yielded colorless but slightly turbid fluid. Fluid analysis revealed 3,100 cell/uL comprised of primarily lymphocytes with a total protein of 2.6g/dL.

o Cerebrospinal fluid was collected from the lumbosacral space. The CSF appeared grossly normal, had a low white blood cell count at 7 cells/uL, and normal total protein of 39 mg/dL. No atypical cells or overt infectious agents were identified.

o CT and attempt at surgical resection/debulking were offered, but owner elected humane euthanasia given poor prognosis.

Post-mortem CT Images

Post mortem CT revealed the mass to follow the course of the nuchal ligament from the occipital bone to the funicular portion at C3 caudally and extend to the atlanto-occipital joint just dorsal to the spinal cord without causing any spinal cord compression. Mineralization extended between the occipital bone and cranial aspect of C1 and along and into the epaxial muscles. Incidental bilateral auricular debris was also noted

Post-mortem Images

Large pocket of soft to gritty tan material replacing ~10 cm long segment of nuchal ligament; this pocket was contiguous with several other pockets of similar tan material/turbid light yellow fluid (not shown).caption
Opened cranial nuchal bursa showing villous lining with gritty tan material on surface; ventral aspect of nuchal bursa was adhered to adjacent muscle and protruded into AO space, abutting/compressing spinal cord, NL = nuchal ligament; * = site of communication with cranial nuchal bursa (NB)caption
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  • Atlantal bursa and nuchal ligament: severe chronic atlantal bursitis and nuchal desmitis with extensive nuchal ligament fiber degeneration, fragmentation, and mineralization
  • Spinal cord (C1): rare dilated myelin sheaths and swollen axons. While the inflamed atlantal bursa abuts the cervical spinal cord at the atlanto-occipital space, axonal degeneration indicative of compression of the C1 spinal cord segment is exceedingly mild.
  •  Right carpus and common extensor tendon: chronic lymphoplasmacytic synovitis and degenerative extensor tendinopathy
  •  Skin (sternal): regional chronic lymphoplasmacytic dermatitis and cellulitis with fat necrosis and fibrosis (compatible with chronic trauma)
  •  Lungs: acute pulmonary edema
  •  Liver: moderate diffuse hepatocellular lipidosis

Discussion

Caprine arthritis-encephalitis (CAE) is a multi-organ-system disease caused by a retrovirus that affects the central nervous system (CNS) and connective tissues with cases of interstitial pneumonia and indurative mastitis also described. Most goats do not develop clinical signs, but for clinically affected patients, the CNS component is seen primarily in young goats (2-4 months of age) as an acute encephalomyelitis, but may also affect older goats. The connective tissue form of CAE typically presents clinically as chronic arthritis in adult goats, with involvement of the carpus being most frequently reported1,2. Gradually noticeable distension of the atlantal and supraspinous bursa, in particular, has also been reported in a group of affected goats with these lesions becoming radiographically prominent because of distension with fluid and mineralization of necrotic debris as in the case presented here2. Onset is insidious in most individuals but sudden in some, and loss of body condition and poor haircoat in patients with arthritis is common1,2. In a pathologic study of 12 goats with CAE, lesions were most often associated with synovial-lined structures, including joints, tendon sheaths, and bursae (particularly the atlantal and supraspinous bursae), and were typified by synovial cell proliferation, subsynovial mononuclear cell infiltration, the presence of fibrin, fibrinous concretions, necrosis, and mineralization. Fluid and mineralized material occasionally extended from capsular or periarticular lesions into the joint space. Extrasynovial lesions were located in kidneys, vessels, and brain. Focal necrosis and mineralization of skeletal muscle were present in one goat3. Imaging findings in this case are similar to those previously reported 2,4.  The most common route of transmission of CAEV infection is by ingestion of colostrum or milk from infected does, but contact transmission between goats of all ages has also been demonstrated 1,2. No vaccine is available for caprine arthritis-encephalitis and no specific treatments exist for the components of CAE besides supportive care for mildly affected patients1.

References

1. Phelps SL, Smith MC. Caprine arthritis-encephalitis virus infection. J Am Vet Med Assoc. 1993 Dec 15;203(12):1663-1666.

2. Crawford TB, Adams DM. Caprine arthritis-encephalitis: clinical features and presence of antibody in selected goat populations. J Am Vet Med Assoc. 1981 April 1;178(7):713-719.

3. Crawford TB, Adams DS, Sande RD, et al. The connective tissue component of the caprine arthritis-encephalitis syndrome. AmJ Pathol 1980;100:443-454.

4. Garry F, Rings DM. Multiple nodular mineralized masses in the nuchal ligament, adjacent muscle, and epidurally in the atlanto-occipital space. J Am Vet Med Assoc. 1985 Sep 15;187(6):641-642.

 

** The authors would like to thank Susan Bender, VMD, PhD, DACVP – University of Pennsylvania, PADLS New Bolton Center for histopathological analysis and associated images.