Assessment of interobserver agreement and use of selected magnetic resonance imaging variables for differentiation of acute noncompressive nucleus pulposus extrusion and ischemic myelopathy in dogs

Abstract

OBJECTIVE To evaluate interobserver agreement for features used in presumptive diagnosis of acute noncompressive nucleus pulposus extrusion (ANNPE) or ischemic myelopathy by MRI, compare findings on postcontrast T1-weighted (T1W) MRI sequences with fat saturation (FS) for the 2 conditions, and determine whether length and directional patterns of hyperintensity of the intramedullary spinal cord on T2-weighted (T2W) fast spin echo (FSE) MRI sequences differ between dogs with these diseases. DESIGN Retrospective, observational study. ANIMALS 20 dogs with clinical signs compatible with ANNPE (n = 14) or ischemic myelopathy (6). PROCEDURES 3 observers evaluated MRI data (including T2W FSE, T2W single-shot FSE, and T1W FS sequences) for dogs with a presumptive diagnosis of ischemic myelopathy or ANNPE. Interobserver agreement for variables of interest including presumptive diagnosis was assessed by κ statistic calculations. Associations between diagnosis and variables of interest were assessed with Fisher exact or Cochran-Mantel-Haenszel tests. RESULTS Perfect interobserver agreement (κ = 1 for all comparisons) was found for the presumptive diagnosis of ischemic myelopathy versus ANNPE. Meningeal enhancement on postcontrast T1W FS MRI images and nonlongitudinal directional pattern of intramedullary hyperintensity on T2W FSE images were significantly associated with a diagnosis of ANNPE. Greater length of intramedullary hyperintensity was significantly associated with a diagnosis of ischemic myelopathy. CONCLUSIONS AND CLINICAL RELEVANCE Directional pattern and length of intramedullary hyperintensity on T2W FSE MRI images and enhancement patterns in postcontrast T1W FS sequences may provide important contributions to the criteria currently used in the presumptive diagnosis of ischemic myelopathy versus ANNPE.

Predictors of urinary or fecal incontinence in dogs with thoracolumbar acute non‐compressive nucleus pulposus extrusion

“…The influence of the location of the T2W hyperintensity in transverse MRI sections in terms of the affected funiculi (dorsal, ventral, lateral, or combinations of them) on the outcome was technically challenging to be investigated. The reasons behind this difficulty included not only limitations because of resolution of the MRI signal within the spinal cord but also the frequently oblique pattern of the T2W hyperintesity in longitudinal sections, which caused changes in the location of the lesion in transverse images according to the level of the section …”

“…Currently, the diagnosis of ANNPE is based on detection of specific MRI features in dogs presented with peracute, nonprogressive, and most often lateralized clinical signs of spinal cord dysfunction. The MRI features suggestive of ANNPE include (a) the presence of a narrowed intervertebral disc with reduced volume of nucleus pulposus located below a focal T2‐weighted hyperintense intramedullary spinal cord lesion; (b) the presence of extradural material compatible with hydrated nucleus pulposus at the same level, causing no or minimal spinal cord compression; (c) the presence of a cleft in the dorsal part of the anulus fibrosus; (d) the presence of meningeal or epidural contrast enhancement in postcontrast T1‐weighted fat‐suppressed images . Considering the nonsurgical nature of the disease, histological confirmation of the diagnosis is rarely obtained; however, the MRI signal characteristics of extradural hydrated nucleus pulposus have been histopathologically validated in 2 studies and can support the diagnosis together with history and clinical signs .…”

Outcome comparison in dogs with a presumptive diagnosis of thoracolumbar fibrocartilaginous embolic myelopathy and acute non‐compressive nucleus pulposus extrusion

“…The MRI features of FCEM have been validated in histopathology in sporadic cases1 6. Recent studies have demonstrated moderate (κ=0.56)17 to perfect (κ=1)18 interobserver agreement in recognising MRI patterns of presumptive FCEM or ANNPE.…”

Magnetic Resonance Imaging Findings in 13 Neurologic Pot-Bellied Pigs

“…FCE and ANNPE share similar MRI features including focal intramedullary T2W hyperintensity compared to normal spinal cord (21,29,30). Imaging features more consistent with ANNPE include lesion location centered over an intervertebral disc space, diminished T2W signal within the nucleus pulposus, and a narrowed intervertebral disc space, with minimal or no spinal cord compression at the affected level of the spinal cord (29,30). Although ANNPE has not been described in pigs, the pigs described as cases 5 and 6 shared some of the imaging features described in dogs with ANNPE, suggesting a similar process may have occurred in these two animals.…”

“…Although a definitive diagnosis requires spinal cord histopathology, certain MRI changes can be identified to aid in an ante-mortem diagnosis of these conditions. FCE and ANNPE share similar MRI features including focal intramedullary T2W hyperintensity compared to normal spinal cord (21,29,30). Imaging features more consistent with ANNPE include lesion location centered over an intervertebral disc space, diminished T2W signal within the nucleus pulposus, and a narrowed intervertebral disc space, with minimal or no spinal cord compression at the affected level of the spinal cord (29,30).…”