Equine Standing CT: Clinical Applications in Diagnosing Common Head and Cervical Pathology
Advances in standing computed tomography (CT) have significantly expanded diagnostic capability in equine practice. The Equina® standing CT system provides high resolution, multiplanar, three-dimensional visualization of osseous and soft tissue structures of the head and cervical region under sedation. This reduces anesthetic risk and improves diagnostic accuracy across a wide range of pathology. Recent developments, including a rear mounted headboard that allows consistent access to C6 and C7 and expanded options for imaging under general anesthesia, have further broadened clinical utility. The following review summarizes six categories of equine head and neck disease in which standing CT has become central to diagnostic evaluation, with representative cases acquired using the Equina® system.
Skull & Mandibular Fractures
Case Example: 15‑Year‑Old Welsh Section A Mare
History
The mare was referred following multiple traumatic kicks to the head with concern for mandibular and temporomandibular joint injury. The owner reported dull mentation, abnormal left optic reflexes, left‑sided facial nerve deficits (drooping ear and muzzle), dysphagia with hypersalivation, and increased respiratory effort accompanied by inspiratory stridor.
Presentation
On arrival, the mare displayed significant neurologic compromise and upper airway obstruction. Due to the severity and localization of signs, a standing CT was performed for full assessment.
CT Findings
Standing CT revealed a severely comminuted, mildly displaced, non‑articular fracture of the left mandibular ramus and neck. A small, mildly displaced non‑articular fracture of the left paracondylar process was also identified.
A faint hypoattenuating line within the left parietal/zygomatic region was consistent with a vascular channel rather than an acute fissure. Extensive soft tissue swelling produced moderate–severe pharyngeal narrowing, and the left guttural pouch was collapsed or filled with soft tissue attenuation, compatible with hematoma or compression from surrounding edema.
Outcome
CT enabled accurate localization and classification of fractures and soft tissue compromise, guiding treatment planning and airway monitoring.
Sinus Disease / Dental Pathology
Case Example: 16‑Year‑Old Warmblood Mare
History
The mare presented with a firm, progressive swelling over the frontal sinus region and intermittent mild purulent discharge from the right nostril. Airflow remained normal bilaterally, and no cranial nerve deficits were present.
Presentation
Physical examination revealed a convex, firm swelling over the frontal sinus with mild right‑sided nasal discharge. Facial symmetry and neurologic function were intact. Standing CT was pursued to characterize the lesion.
CT Findings
Imaging identified a peripherally mineralized conchofrontal midline mass, consistent with a sinus cyst. Additional findings included bilateral, asymmetric rhinitis, paranasal sinusitis, hyperostosis of the right maxillary alveolar bone (teeth 109–111), and mild odontoclastic tooth resorption with hypercementosis of the incisors.
Outcome
A standing bilateral frontonasal bone‑flap procedure was performed, allowing complete cyst removal without complication. The mare recovered uneventfully and was discharged with an excellent prognosis.
Temporomandibular Joint Septic Arthritis
Case Example: 17‑Year‑Old Quarter Horse Gelding
History
The gelding was referred for worsening swelling, pain, and dysfunction of the left temporomandibular joint (TMJ). Clinical signs included lethargy, reduced feed intake, difficulty chewing hay, and marked sensitivity over the affected area.
Presentation
The gelding exhibited significant facial swelling, heat, and pain on palpation. He chewed hay slowly and occasionally quidded, though soft feed intake was normal. Initial diagnostics showed severe synovial inflammation and bacterial infection.
CT Findings
CT demonstrated severe septic TMJ arthritis, condylar osteomyelitis, a chronic nondisplaced fracture with osseous sequestration, left otitis media, and Grade 3 bilateral temporohyoid osteoarthropathy. Additional chronic skull changes were also present, confirming advanced, multifocal disease.
Outcome
Despite arthrotomy, lavage, and aggressive antimicrobial therapy, infection progression and extensive osteomyelitis resulted in a grave prognosis. Mandibular condylectomy was considered but deemed unlikely to restore comfort due to suspected persistent stylohyoid osteomyelitis. Humane euthanasia was elected.
Soft Tissue Pathology — Perilaryngeal Emphysema with Abscess
Case Example: 8‑Year‑Old Quarter Horse Gelding
History
The gelding developed severe cervical and perilaryngeal emphysema after repeated nasogastric intubation and upper airway procedures for a prior colic hospitalization.
Presentation
The horse arrived with diffuse subcutaneous emphysema of the pharyngeal and cervical regions, marked swelling, and reliance on a temporary tracheostomy. Endoscopy revealed near‑complete airway obstruction from laryngeal edema, though no discrete perforation was visualized.
CT Findings
Standing CT revealed:
Extensive perilaryngeal and retropharyngeal emphysema extending ventrally along fascial planes
Intralesional feed material and/or abscessation within retropharyngeal tissues
Regional cellulitis, suggesting penetrating mucosal trauma or sealed perforation
Significant laryngeal compression with reduced arytenoid mobility
Tracheitis and tracheal wall edema, likely related to the tracheostomy tube
Tracking cervical emphysema approaching the vertebral canal
Mild incidental right maxillary sinusitis
Outcome
Intensive antimicrobial therapy and supportive care led to progressive resolution of emphysema and abscessation. Laryngeal function normalized, swelling resolved, and the gelding returned to normal eating and behavior. Outpatient airway re‑evaluation was planned.
Cervical Vertebral Trauma
Case Example: 2‑Month‑Old Quarter Horse Colt
History
The colt was discovered 36 hours after a suspected halter‑related trauma with mild right head tilt, intermittent depression, and swelling over the left cranial neck and head.
Presentation
On referral, the colt was bright and neurologically appropriate. Examination revealed mild head tilt, palpable crepitus over the injury site, normal gait at walk and trot, and no overt neurologic deficits. CT was performed to evaluate suspected cervical fracture.
CT Findings
CT identified fractures of the right jugular process and the right lamina of C1, with an open C1 fracture allowing a small amount of gas to enter the vertebral canal. Fragment displacement caused moderate canal narrowing at C1–C2 and subluxation of the right atlanto‑occipital joints. Soft tissue within the vertebral canal suggested hemorrhage or inflammatory debris, and mild spinal cord compression was suspected.
Outcome
The CT findings provided definitive localization and severity grading, guiding further decision‑making regarding stabilization, prognosis, and monitoring.
Cervical Vertebral Disc & Canal Abnormalities
Case Example: 5‑Year‑Old Thoroughbred Gelding
History
The gelding experienced an acute episode of severe pain followed by collapse and violent thrashing. He had been performing normally prior to the event. Examination revealed grade 3–4 hind‑limb ataxia, with the horse nearly falling when turning. Radiographs and ultrasound did not reveal a cause, prompting CT evaluation.
Presentation
Despite significant ataxia, standing CT successfully imaged the cervical vertebrae through the C5–C6 region.
CT Findings
Findings included:
Mild funnel‑shaped narrowing of the vertebral canal at C4–C5
Lateromedial elongation and dorsoventral shortening of cranial C4 and C5
Flattened spinal cord appearance, with loss of surrounding epidural fat
Moderate dorsal lamina extension (C3–C5)
Mild endplate flaring (C3–C4)
Mild periarticular spur formation (C2–C6)
Mild buttress formation of the right cranial articular process of C6
Narrow intervertebral disc spaces (C2–C5)
Reduced intra‑vertebral sagittal ratios at C4 and C5 (<0.50), consistent with cervical canal stenosis
Outcome
The CT findings provided critical diagnostic information to guide neurologic prognosis and management, clarifying the structural abnormalities contributing to the horse’s severe ataxia.
CT Cervical Myelography
The Equina® system supports CT myelography for evaluating spinal cord compression, extradural attenuation, and canal stenosis. The case of a 7-year-old Quarter Horse gelding demonstrates excellent contrast filling of the subarachnoid space with high-resolution three-dimensional reconstructions. These images provide clear definition of the cervical cord contour and canal margins.
CT myelography increases diagnostic sensitivity in neurologic cases where CT imaging alone may not demonstrate cord compression sufficiently.
General Anesthesia Imaging Capabilities
Although designed for standing sedation, the Equina® platform can be used for recumbent imaging when necessary. Asto CT has developed an 80-centimeter surgical table extension that allows rapid and safe positioning of horses under general anesthesia. The extension supports loads up to 750 pounds and has been used clinically to complete cervical imaging from induction to recovery in less than 20 minutes. Imaging in lateral recumbency can provide visualization through C7 and T1 depending on conformation.
Access to Caudal Cervical Spine (C6 and C7)
With the rear mounted headboard and revised head support, clinicians can now consistently image the caudal cervical region including the cranial aspect of C7 in standing horses. This capability has been confirmed through studies performed at multiple clinical sites.
Conclusion
Equine standing CT has reshaped the diagnostic approach to head and cervical pathology. Recent improvements to the Equina® system, including enhanced access to the caudal cervical spine, expanded general anesthesia imaging capabilities, and integration of CT myelography, continue to broaden the range of cases that can be evaluated effectively. These capabilities improve diagnostic accuracy and enable earlier, more targeted clinical intervention.
All referenced cases were acquired using the Equina® CT system.