Ultrasonographic investigation of the atlanto-occipital articulation in the horse

Ultrasonography of the spinal cord and the collection of cerebrospinal fluid from the Atlanto-occipital space in goat

Ultrasonography, a non-invasive and useful technique, is used for the examination of Atlanto-occipital space structural visualization. The collection of cerebrospinal fluid is more accurate and easier under ultrasound-guided procedure. In this study, longitudinal and transverse views of the Atlanto-occipital space were scanned and their different structural dimensions were measured in sixty healthy Beetal goats. In longitudinal plane, gap between skin and arachnoidea ranged from 8.71 to 10.21 mm (mean ± SD, 9.76 ± 0.44 mm). Depth of the subarachnoid gap dorsal and ventral to the spinal cord ranged from 2.14 to 3.23 mm (mean ± SD, 2.81 ± 0.33mm) and from 6.09 to 7.68 (mean ± SD, 7.02 ± 0.45 mm) respectively. Spinal cord diameter varied from 3.76 to 5.26 mm (mean ± SD, 4.57 ± 0.44 mm) and entire dural sac diameter varied from 12.59 to 15.69 mm (mean ± SD, 14.37 ± 0.74 mm). The spinal cord can be seen only in longitudinal plane over a distance of 1.81 to 2.93 mm (mean ± SD, 2.46 ± 0.35 mm). While in the transverse plane, gap between the skin and arachnoidea ranged from 11.01 to 13.11 mm (mean ± SD, 12.39 ± 0.54 mm). Depth of the subarachnoid space dorsal and ventral to spinal cord varied from 5.05 to 6.13 mm (mean ± SD, 5.59 ± 0.34 mm) and 4.12 to 5.25 (mean ± SD, 4.65 ± 0.29 mm) respectively. Spinal cord diameter ranged from 4.45 to 5.90 mm (mean ± SD, 5.24 ± 0.44 mm) and entire dural sac diameter varied from 14.68 to 16.96 mm (mean ± SD, 15.58 ± 0.57 mm). These standard measurements will be the reference values in healthy Beetal goats. Cerebrospinal fluid was colourless with the quantity of 2-4 ml (mean ± SD, 3 ± 0.89 ml). It was neither turbid nor coagulate. The white blood cell count was 10/µl and red blood cells were not present. Furthermore, total protein and glucose were also measured, which ranged from 23.5 to 28 mg/dl (mean ± SD, 25.78 ± 2.32 mg/dl) and 38-50 mg/dl (mean ± SD, 43.33 ± 4.60 mg/dl) respectively. Ziehl-Neelsen Staining and gram staining were negative.

Chronic Atlantoaxial Luxation Imaging Features in a Pony with Intermittent Neck Stiffness

A 17-year-old mixed breed pony was presented with intermittent neck stiffness during regular training rides in the six months preceding its admission. All parameters were within the normal range, except for an increase in heart rate (48 bpm) during the examination. Concave areas were observed at the level between the atlas and axis vertebrae (C1-C2) on both the left and right sides of the neck. Radiographs were taken of the laterolateral, left ventrodorsal oblique, and right ventrodorsal oblique projections in the cranial cervical region. The images revealed severe structural disorders, including trauma with luxation of the atlantoaxial joint, a fusion of the atlas and axis vertebrae, and evidence of a false joint in the axis bone. Subsequent ultrasonography showed hyperechoic areas in the rectus capitis caudalis and obliquus capitis caudalis muscles. Neck mobility was improved after two weeks of stall rest, administration of oral phenylbutazone (4.4 mg/kg), and topical cold gel treatment. The overstretching of surrounding soft tissues accompanying chronic injury of cranial cervical area may result in neck stiffness in the aging pony. Radiographic and ultrasonographic findings were consistent with the presence of cranial cervical trauma leading to neck stiffness. These findings emphasized the essential role of imaging diagnostics in treating a pony with intermittent neck stiffness.

Arthroscopic approach and intra-articular anatomy of the equine atlanto-occipital joint

OBJECTIVE

To develop arthroscopic approaches to the atlanto-occipital (A-O) and describe associated arthroscopic anatomy.

STUDY DESIGN

Experimental ex vivo study and clinical case report.

ANIMALS

Ten equine cadaver joints and 1 clinical case.

METHODS

CT arthrograms of 8 A-O joints were performed to determine the placement of an arthroscopic portal. Arthroscopy was performed via dorsal and/or ventral approaches (dorsal or ventral to the longissimus capitis tendon) in 10 cadaveric A-O joints and the A-O joint of a 2-week-old foal with septic arthritis. Accessible cartilage was debrided in 3 cadaver joints. Accessibility and risks were assessed by review of arthroscopic images, postoperative necropsy, and computed tomography (CT).

RESULTS

Dorsal and ventral outpouchings of the A-O joint were identified with CT. Arthroscopy of the dorsal pouch provided access to 50% of the dorsocranial occipital condyle and 15% of the dorsocranial atlas articular surfaces. Joint distension caused displacement of the dura. Dura perforation occurred with a blind dorsal approach in 2 of 5 joints. Dura perforation did not occur after ultrasonography-guided approaches. Arthroscopic debridement of septic arthritis and osteomyelitis was successful in 1 clinical case.

CONCLUSION

Approaches to the A-O joint were determined from CT examinations. The cranial aspect of the dorsal pouch of the A-O joint was accessed via arthroscopic triangulation in all horses of this study. Ultrasound-guided joint access prevented perforation of vital structures, including the spinal canal.

CLINICAL SIGNIFICANCE

Advanced imaging improves the diagnosis of A-O joint pathology. Descriptions of arthroscopic anatomy and accessibility provide important information for surgical intervention.

Aspectos tomográficos da coluna cervical de equinos

Descreveu-se a anatomia da região cervical de equinos adultos, com base em imagens obtidas no exame de tomografia computadorizada helicoidal realizado em peças anatômicas de equinos adultos. A tomografia computadorizada foi o método de imagem diagnóstica de escolha e possibilita as reconstruções de imagens tridimensionais e em outros planos anatômicos, como sagital e coronal. Todas as imagens foram adquiridas e avaliadas em filtro e janela para tecido ósseo. Observaram-se diferenças anatômicas e as particularidades normais das vértebras, principalmente da região occipitoatlantoaxial, a qual apresenta maior incidência de alterações.

Ultrasound-guided atlanto-occipital puncture for myelography in the horse

Complications of cervical myelography arising from the puncture of the subarachnoid space to collect the cerebrospinal fluid and to inject the contrast medium have been described in humans and animals. In this study, 2 ultrasound-guided procedures were developed for puncture of the atlanto-occipital subarachnoid space, collection of cerebrospinal fluid, and injection of contrast medium. Myelography was performed on 6 ataxic horses using these procedures. The first attempt to puncture the subarachnoid space was successful in 5 horses and in one horse, a second attempt was necessary. Collection of cerebrospinal fluid and injection of contrast medium were achieved without difficulty. Ultrasound-guided myelography allowed reduction of potential complications associated with blind percutaneous puncture of the subarachnoid space. Methods described in this study should be tried-at least initially in an experimental setting--to collect cerebrospinal fluid from the atlanto-occipital site in standing horses where it may represent an alternative method when lumbosacral cerebrospinal fluid collection has been unsuccessful or contaminated with blood.