Diffuse idiopathic skeletal hyperostosis of the spine in a nine-year-old cat

Thoracic Vertebral Canal Stenosis and Vertebral Instability in a Young Minuet Cat

This report describes a unique case of thoracic vertebral canal stenosis and vertebral instability in a 1 yr old Minuet cat. The cat presented with a history of chronic progressive nonambulatory paraparesis. Myelography with neutral and stress positions revealed dynamic compression at T1-4. Computed tomography and MRI revealed multiple sites of vertebral endplate osteolysis, adjacent bone sclerosis, intervertebral disk space narrowing, and spondylotic bridging within the cervical and cranial thoracic vertebral bodies and pedicles, particularly at C6-T4. The cat underwent a right-sided T1-4 hemilaminectomy and C7-T4 vertebral stabilization using positively threaded profile pins and polymethylmethacrylate. The cat fully recovered without any complication. The case highlights the potential for young cats, especially those with a chondrodysplastic condition, to develop vertebral canal stenosis and vertebral instability. The surgical treatment described herein resulted in an excellent outcome.

Demographics, clinical findings and diagnoses of cranial thoracic myelopathies (T1-T6 vertebrae) in cats

OBJECTIVES

The aim of the study was to describe the patient demographics, clinicopathological features and presumptive or final diagnoses in cats with myelopathies between the T1 and T6 vertebrae.

METHODS

This retrospective multicentre case study enrolled cases between 2015 and 2022 that were diagnosed with myelopathies between the T1 and T6 vertebrae as the primary cause for the presenting clinical signs.

RESULTS

A total of 21 cases matched the inclusion criteria, 13 males (11 castrated and 2 entire) and 8 spayed females (median age 93 months; range 5-192). Most of the cases presented with a chronic and progressive history (76% and 86%, respectively), with a median duration of 29 days (range 1-2880). At the time of presentation, 90% of the cases were localised to the T3-L3 spinal cord segments based on neurological examination. The most common underlying pathology was neoplasia (42.9%), followed by inflammatory (24%), anomalous (19%), degenerative (9.5%) and vascular (4.8%) disorders. The most common location was T3-T4 (29%), followed by T2-T3 and T5-T6 (19% each). The cutaneous trunci reflex was normal in 86% of the cases and most of the cases (71%) did not show spinal discomfort upon admission.

CONCLUSIONS AND RELEVANCE

Neoplasia was the most common cause of cranial thoracic myelopathy in this study. The lack of pathognomonic clinical signs for this specific region highlights the importance of assessing the entire thoracolumbar region up to and including at least the T1 vertebra when investigating cases with signs consistent with a T3-L3 myelopathy.

Evidence for a genetic contribution to the ossification of spinal ligaments in Ossification of Posterior Longitudinal Ligament and Diffuse idiopathic skeletal hyperostosis: A narrative review

Diffuse Idiopathic Skeletal Hyperostosis (DISH) and Ossification of the Posterior Longitudinal Ligament (OPLL) are common disorders characterized by the ossification of spinal ligaments. The cause for this ossification is currently unknown but a genetic contribution has been hypothesized. Over the last decade, many studies on the genetics of ectopic calcification disorders have been performed, mainly on OPLL. Most of these studies were based on linkage analysis and case control association studies. Animal models have provided some clues but so far, the involvement of the identified genes has not been confirmed in human cases. In the last few years, many common variants in several genes have been associated with OPLL. However, these associations have not been at definitive levels of significance and evidence of functional significance is generally modest. The current evidence suggests a multifactorial aetiopathogenesis for DISH and OPLL with a subset of cases showing a stronger genetic component.

Minimally invasive spinal surgery in a young cat with vertebral hypertrophy

Case summary

A 2-year-old neutered female Scottish Fold cat was presented with an 8-week history of progressive back pain, paraparesis and decrease of postural reactions in both pelvic limbs. MRI showed spinal cord compression from both ventral sides, which originated from the T4 vertebral body and pedicle. The lesion compressing the spinal cord had a bone-like density on CT, and endoscopic surgery was performed to excise it. Histopathological examination of the resected tissue showed no evidence of malignancy and the lesion was diagnosed as vertebral hypertrophy. After surgery, the neurological status of the cat gradually improved. The cat was ambulant at the follow-up evaluation 2 weeks after surgery. Six months later, hindlimb paresis had improved considerably, and no recurrence was observed on CT.

Relevance and novel information

This is the first description of thoracic vertebral canal stenosis due to hypertrophy of a single vertebra in a young cat. Excision of the hypertrophic vertebra by endoscopic surgery is less invasive than open surgery and may give a good prognosis.

DIFFUSE IDIOPATHIC SKELETAL HYPEROSTOSIS WITH SECONDARY DYSPHAGIA IN A BLACK-HANDED SPIDER MONKEY (ATELES GEOFFROYI)

A 32-yr-old male black-handed spider monkey (Ateles geoffroyi) with marked kyphosis and reduced spinal range of motion developed intermittent regurgitation, which was managed with an acid reducer. Diffuse idiopathic skeletal hyperostosis (DISH) was suspected in this animal due to radiographically evident ossification of the anterior longitudinal ligament. At repeat radiographic evaluation 1.5 yr later, due to weight loss and increased frequency of regurgitation, the cervical spine was deviated ventrally and appeared to be impinging on the thoracic inlet. The spider monkey was humanely euthanized due to poor prognosis, and the presumptive diagnosis of DISH was confirmed via postmortem computed tomography and necropsy. DISH has not been reported in black-handed spider monkeys, and secondary dysphagia, an uncommon but recognized consequence in humans, has not been reported in a nonhuman primate. Earlier recognition of this possibly underreported disease process may increase treatment options and effectiveness of intervention.

Evaluation of agreement and correlation of results obtained with MRI-based and macroscopic observation-based grading schemes when used to assess intervertebral disk degeneration in cats

OBJECTIVE

To evaluate agreement in results obtained with an MRI-based grading scheme and a macroscopic observation-based grading scheme when used to assess intervertebral disk (IVD) degeneration in cats.

SAMPLE

241 MRI and 143 macroscopic images of singular IVDs in 44 client-owned cats (40 cadaveric and 4 live).

PROCEDURES

Singular images of IVDs were obtained of live cats admitted for treatment of suspected neurologic disease (MRI images of IVDs) and of cadavers of cats euthanized for reasons unrelated to spinal disease (MRI and macroscopic images of IVDs) at the Small Animal Hospital, Vetsuisse Faculty, Zurich, Switzerland, between January 12, 2015, and October 19, 2015. The IVD images were randomized and evaluated twice by 4 observers for each grading scheme. Inter- and intraobserver reliability for the grading schemes was assessed with Cohen weighted κ analysis. Agreement and correlation between results obtained with the 2 grading schemes were determined with Cohen weighted κ and Spearman correlation coefficient (ρ) analyses, respectively.

RESULTS

Inter- and intraobserver agreement between results was substantial to almost perfect (mean weighted κ, 0.66 to 0.83 and 0.71 to 0.86, respectively) for the MRI-based grading scheme and moderate to substantial (mean weighted κ, 0.42 to 0.80 and 0.65 to 0.79, respectively) for the macroscopic observation-based grading scheme. Between the 2 grading schemes, agreement in results was moderate (mean ± SE weighted κ, 0.56 ± 0.05), and the correlation was strong (ρ = 0.73).

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that the MRI-based and macroscopic observation-based grading schemes used in the present study could be used reliably for classifying IVD degeneration in cats.

Thoracic vertebral canal stenosis due to articular process hypertrophy in two cats treated by hemilaminectomy with partial osteotomy of the spinous process

Case summary

A 9-year-old neutered female British Shorthair cat (case 1) and a 13-year-old neutered male domestic shorthair cat (case 2) showed signs of chronic T3-L3 myelopathy, which progressed over 6 and 12 months, respectively. On presentation, case 1 had moderate pelvic limb proprioceptive ataxia and ambulatory paraparesis, and case 2 was non-ambulatory paraparetic and had urinary incontinence. Bilateral enlargement of the articular process joints at T11-T12 in case 1 and T3-T4 in case 2 causing dorsolateral extradural spinal cord compression was shown on MRI. Surgical decompression by a unilateral approach through hemilaminectomy with partial osteotomy of the spinous process was performed in both cases. The side of the approach was chosen based on the severity of the cord compression. Surgery resulted in a satisfactory outcome with short hospitalisation times. On discharge, case 1 showed mild postural reaction deficits on both pelvic limbs. Case 2 had regained urinary continence and could ambulate unassisted, although it remained severely ataxic. The 6 month follow-up showed very mild paraparesis and proprioceptive ataxia in both cats. No chronic medical treatment was required.

Relevance and novel information

This is the first report to describe clinical presentation, imaging features, surgical treatment and outcomes of thoracic vertebral canal stenosis owing to bilateral articular process hypertrophy in cats with no adjacent spinal diseases. Thoracic articular process hypertrophy should be included in the differential diagnosis of adult cats with chronic progressive myelopathy. Hemilaminectomy with partial osteotomy of the spinous process might be an appropriate surgical technique in these cases.