Imaging and histopathologic features of reversible nerve root and peripheral nerve edema secondary to disc herniation in a cat

Outcomes of surgically and conservatively managed thoracolumbar and lumbosacral intervertebral disc herniations in cats

BACKGROUND

Limited information is available regarding intervertebral disc herniation (IVDH) and its treatment in cats.

OBJECTIVES

Describe outcomes after surgical or conservative treatment of cats with thoracolumbar and lumbosacral IVDH.

ANIMALS

Ninety-two cats from 2 referral populations (2012-2022) with compressive IVDH between the T3 and S1 vertebrae.

METHODS

Retrospective cohort study evaluating outcomes of surgical (49 cats) and conservative (36 cats) management of IVDH; 7 cats were euthanized at diagnosis. Outcome was assessed using hospital and referring veterinarian records and client questionnaires. Successful outcome was defined as regained or improved ambulation, urinary and fecal continence, and no requirement for analgesic medication.

RESULTS

Incidence of IVDH during the study period was 0.44% (92/20849). Surgical treatment resulted in 62% (6 weeks) and 74% success (6 months). Conservative treatment resulted in 54% (6 weeks) and 65% success (6 months). Neurological grade at presentation was higher in cats treated surgically (median, 2; range, 1-5) than in those treated conservatively (median, 2; range, 0-4; P = .001). Regardless of treatment type, cats suffering trauma were more likely to have a successful outcome 6 weeks after treatment compared with those without history of trauma (odds ratio, 5.3; 95% confidence interval, 1.05-26.78; P = .04). Neurological deficits remained in the majority of cats for both treatment types (92%, conservative; 86%, surgical at 6 weeks). Acute-on-chronic IVDH with characteristics of both extrusion and protrusion were identified in 10% of cats.

CONCLUSIONS AND CLINICAL IMPORTANCE

Conservative treatment could be as effective as surgical decompression in cats with thoracolumbar or lumbosacral IVDH.

Prevalence, clinical presentation and MRI of intervertebral disc herniations in cats

OBJECTIVES

The aims of this study were to evaluate the prevalence and to describe the clinical and diagnostic imaging features of the different types of feline intervertebral disc herniation (IVDH).

METHODS

Medical records and imaging studies were retrospectively reviewed for cats diagnosed with IVDH between January 2008 and October 2020. Information obtained from the clinical records included signalment, clinical presentation, the presence of spinal hyperaesthesia and neurolocalisation. Diagnostic imaging findings, including type (ie, intervertebral disc extrusion [IVDE], intervertebral disc protrusion [IVDP] or acute non-compressive nucleus pulposus extrusion (ANNPE), site and number of IVDHs, were recorded. The association between breed, age, sex, duration and severity of neurological signs, the presence of spinal pain and MRI features was evaluated.

RESULTS

Forty-three cats were included. A total of 50 IVDHs were identified: 39 cats were diagnosed with a single IVDH and four with multiple IVDHs. The most common type of IVDH was ANNPE (n = 22), followed by IVDP (n = 19) and IVDE (n = 9). Neuroanatomical localisation included L4-S3 (n = 19/43), T3-L3 (n = 18/43) and C1-C5 (n = 6/43). Cats with a single IVDH were statistically significantly associated with a diagnosis of ANNPE (P = 0.023) compared with cats with multiple IVDHs affected by IVDP (P = 0.004). Males were more commonly affected by IVDE (P = 0.020) and females by ANNPE (P = 0.020). Cats with IVDP had a longer duration of clinical signs (P <0.001) than cats with ANNPE and demonstrated milder neurological deficits (P = 0.005). IVDEs were statistically significantly associated with spinal hyperaesthesia (P = 0.013), while ANNPEs were not (P = 0.014).

CONCLUSIONS AND RELEVANCE

ANNPE, IVDP and IVDE are each associated with distinctive clinical scenarios. Thoracolumbar and mid-to-caudal lumbar regions are the most affected, followed by the cranial cervical spine segment.

Lumbar intervertebral foraminal disc extrusion in a cat

Case summary

A 10-year-old domestic longhair cat was presented for investigations into a 4-day history of acute-onset lethargy, hyporexia and right pelvic limb lameness. Based upon the neurological examination, a right femoral nerve localisation was suspected. Pelvic radiographs identified a dorsally displaced L5–L6 intervertebral disc, with subsequent MRI suggestive of a right L5–L6 neuritis secondary foraminal intervertebral disc extrusion. Medical management, consisting of rest and analgesia, resulted in near-complete resolution of clinical signs in 37 days.

Relevance and novel information

To our knowledge, this is the first report of a lumbar foraminal intervertebral disc extrusion in a cat and should be considered on the differential list for acute-onset pelvic limb lameness in the absence of neurological deficits.

Imaging and histopathologic features of reversible nerve root and peripheral nerve edema secondary to disc herniation in a cat

Nerve root enlargement with increased contrast uptake has been reported in dogs and humans secondary to nerve root compression. In cats, nerve root enlargement and contrast uptake only have been reported in association with inflammatory and neoplastic diseases, but not as a sequela to nerve root compression. An 8‐year‐old oriental short hair cat was presented with acute neurologic deficits consistent with left‐sided sciatic nerve deficit and possible L6‐S1 myelopathy. Magnetic resonance imaging (MRI) was performed and identified compression of the cauda equina and L7 nerve root associated with intervertebral disc herniation (IVDH) at L6‐L7 as well as widespread sciatic nerve enlargement with moderate rim enhancement. A hemilaminectomy was performed to evacuate herniated disc material. The nerve root was biopsied and submitted for histological evaluation. Interstitial nerve edema was diagnosed. Follow‐up MRI 3 months postoperatively showed complete remission of the changes. Nerve root thickening together with contrast enhancement may represent nerve edema in cats secondary to IVDH.