Radiographic and computed tomographic features of a subarachnoid diverticulum causing compressive cervical myelopathy in a yearling Warmblood horse

Abstract

SummaryA 1‐year‐old Belgian Warmblood with a previously known history of successfully repaired temporal and parietal bone fractures sustained at 14 days of age was presented for investigation of a recent, acute and progressive quadrilateral ataxia. The owner reported a lack of coordination and difficulty getting up, with progressing paresis 2 weeks prior to the presentation. Neurological examination revealed pronounced hypermetria/dysmetria in the walk and trot in all four limbs. No evidence of cranial nerve deficits was observed. The horse was in good general condition with unremarkable clinical parameters. Survey lateral radiographs of the cervical spine revealed significant signs of cervical vertebral malformation, including hypertrophy of the articular process joints, indicating narrowing of the spinal canal with suspected cervical stenotic myelopathy. Cervical computed tomographic (CT) myelography revealed the presence of multiple dorsal subarachnoid diverticula causing significant spinal cord compression at multiple locations, with osteoarthrosis of the cervical articular process joints. Due to a poor prognosis and guarded surgical outcome, the owner declined further treatment, and the horse was discharged with conservative corticosteroid treatment. The patient was euthanised shortly after the initial presentation due to progressive worsening signs. To the authors' knowledge, CT myelography findings in a yearling with cervical subarachnoid multiple diverticula have not been previously published. This case illustrates the usefulness of advanced imaging techniques, such as CT myelography, in combination with static and dynamic radiography to provide a better and more accurate diagnosis.

Subarachnoid diverticula in horses

“…Recent publications have proved the aid of computed tomography of the equine cervical spine and this modality is now used on many occasions. More investigation leads to more findings and, as described by Olszewska et al (2024) in this issue, particularly rare diagnoses. Subarachnoid diverticula are intradural extramedullary lesions of the vertebral canal leading to serious spinal cord compression and neurological disease.…”

“…MRI is superior to CT myelography in the rare instance where the diverticulum does not communicate with the subarachnoid space (Thrall, 2018). However, as stated by Olszewska et al (2024), this is not feasible in horses due to the size limitation.…”

“…Lesions other than CVM involving compression of the spinal cord, such as abnormalities of the subarachnoid space, are much less commonly described in horses and much more extensively in small animals and humans. Especially those involving primary lesions of the subarachnoid space as described by Olszewska et al (2024).…”

“…The discussed theories for congenital abnormalities described are (i) the development of diverticula due to a one-way-valve effect causing pressure disturbances leading to gradual spinal cord compression and these diverticula or (ii) abnormal development of the arachnoid membrane during embryogenic development (Olszewska et al, 2024). In general, subarachnoid diverticula (also named intradural arachnoid diverticula or spinal arachnoid diverticula) are rare, especially in equine literature with only three case reports over the last 50 years (Allison & Moeller Jr, 2000;Fisher et al, 1981;Olszewska et al, 2024). Olszewska et al is the first one to describe them ante-mortem on a cross-sectional image modality.…”

“…The most common location in small animals, predominantly dogs, is the cranial cervical or caudal thoracic region. The lesions are usually single but can be multiple, as seen in Olszewska et al (2024).…”