Ischemic Myelomalacia Due to Cartilage Emboli Associated with Chronic Diskospondylitis in a Group of Swine

Abstract

Rear limb paralysis in market age swine occurs sporadically and can be attributed to a variety of causes, including fractures, spinal abscesses, and ischemic myelomalacia due to cartilage (fibrocartilage) emboli from the nucleus pulposus. 11,16 Cartilage emboli resulting in ischemic myelomalacia have been reported in several species, most commonly in adult large-and giant-breed dogs and rarely in swine. [4][5][6]9,10,[14][15][16] In a recent report, there was a high incidence of rear limb paresis/paralysis in a large group of finishing pigs caused by ischemic myelomalacia due to fibrocartilage emboli in the spinal cord. 3 However, no factors were identified in the affected pigs that predisposed them to development of cartilage emboli. In this follow-up report to that case, we describe an additional group of finishing pigs with ischemic myelomalacia caused by cartilage emboli. These pigs also had chronic diskospondylitis.Market weight swine in a production unit with approximately 1,800 grow-finish swine developed a high incidence of acute rear limb paralysis following transportation to market (25/1,800 swine affected). 3 These swine were from a high-lean, heavily muscled genetic line that had a rapid growth rate, and they were extremely large (127 kg) when transported. Nine of these paralyzed swine were submitted to the Iowa State University Veterinary Diagnostic Laboratory (ISU-VDL) for necropsy. All 9 of these swine had ischemic myelomalacia associated with cartilage emboli in spinal cord vessels. However, abnormalities in the spine were not detected, and a predisposing cause for the cartilage emboli was not discovered. Several weeks later, acute rear limb paralysis developed in several market weight swine in additional groups (500 swine/group) from the same production unit. The circumstances of this episode were similar to those of the previous episode of paralysis, occurring after transportation to market. Five paralyzed swine were submitted to the ISU-VDL for necropsy and complete examination of the spinal cord and spine. The spinal cords were removed following dorsal laminectomy, and the spines were sectioned longitudinally with a bandsaw in a dorsoventral vertical plane. Sections of vertebrae, intervertebral disks, and the entire spinal cords from all 5 pigs were fixed in 10% neutral buffered formalin. Vertebrae were demineralized in a 25% aqueous solution of formic acid, and all tissues were embedded in paraffin, sectioned at 5 m, and stained with hematoxylin and eosin. Replicate sections were stained with Alcian blue at pH 2.5 to identify fragments of nucleus pulposus.From the Department of Veterinary Pathology and the Veterinary

Fibrocartilaginous Embolic Myelopathy in a Horse

“…The emboli may involve vessels of the spinal cord, leptomeninges or both. Fibrocartilaginous embolism (FCE) and ischaemic myelopathy have been commonly described in humans (Tosi et al., 1996) and dogs (Hayes et al., 1978; Cauzinille and Kornegay, 1996) with a few cases in lambs (Jeffery and Wells, 1986), pigs (Tessaro et al., 1983; Haynes and Benson, 1999), turkeys (Stedman et al., 1998) cats (Scott and O'Leary, 1996) and two cases in horses (Taylor et al., 1977; Fuentealba et al., 1991). The clinical presentation may be similar to other conditions involving the spinal cord such as trauma, wobbler syndrome, cervical vertebral malformation or intervertebral disc prolapse.…”

Arterial lumbosacral spinal cord infarction in a 4-year-old post-parturient cow

“…It is speculated that the alteration of the subarachnoidal blood vessels which were probably the branches of the dorsal spinal arteries may have followed that of the dorsal spinal arteries several days later, presumably in a period corresponding with parturition, thereby giving rise to ischaemia due to decreased or arrested arterial blood supply and resulting in infarction of the watershed areas at the spinal cord. Fibrocartilaginous embolism derived from the nucleus pulposus of the intervertebral disc, the precise pathogenesis of which remains poorly understood, is an important risk factor for the development of spinal cord infarction or myelomalacia in several domestic or other animal species, such as the cat (Scott & O'Leary 1996;Mikszewski et al 2006), the dog (Cauzinille 2000), the pig (Haynes & Benson 1999), the horse (Fuentealba et al 1991), the bovine species (Landolfi et al 2004) and the lion (Ricci et al 2010). Other risk factors confirmed so far are limited to a small number, including necrotizing polyarteritis involving the leptomeniges of the spinal cord in dogs (Hoff & Vandevelde 1981), general anesthesia in a horse (Lerche et al 1993), an episode of hypotension associated with a surgical procedure in a monkey (Zeiss et al 2001) and aortic catheter implantation in a calf (Offinger et al 2011).…”

Fibrocartilaginous Embolic Myelopathy in a Calf

“…Clinically, acute to subacute, nonprogressive, focal spinal cord dysfunction in the absence of hyperpathia is suggestive of fibrocartilaginous embolic myelopathy. 4,7,8 The following is a case report of fibrocartilaginous embolic myelopathy in a bovine.…”

“…Fibrocartilaginous embolism (FCE) of the spinal cord, or rarely the brain stem, is a relatively uncommon cause of acute, nonprogressive neurological dysfunction that has been previously described in humans, 15 dogs, 2,3,5,7,11 pigs, 1,8,10,14 horses, 6,13 cats, 2,16 and a lamb. 9 Spinal cord injury results from occlusion of the vasculature (arteries, veins, or a combination of both) within the cord parenchyma or the adjacent leptomeninges by masses of fibrocartilaginous material histochemically identical to fibrocartilage of the nucleus pulposus of the intervertebral disk.…”

“…Clinically, acute to subacute, nonprogressive, focal spinal cord dysfunction in the absence of hyperpathia is suggestive of fibrocartilaginous embolic myelopathy. 4,7,8 The following is a case report of fibrocartilaginous embolic myelopathy in a bovine.A 5-month-old Angus heifer calf was presented to the ambulatory service of the Virginia-Maryland Regional College of Veterinary Medicine Veterinary Medical Teaching Hospital (VMTH), Blacksburg, Virginia, with a history of being acutely down. The calf was found in lateral recumbency and was unable to rise with assistance.…”