EQUINE VETERINARY EDUCATION Equine vet. Educ. (2020) 32 (8) 437-443 doi: 10.1111/eve.13125


Original Article


Intervertebral disc disease of the cervical and cranial thoracic vertebrae in equidae: eight cases S. Dyson*†


, V. Busoni‡ and A. Salciccia‡


†Centre for Equine Studies, Animal Health Trust, Newmarket, Suffolk, UK; and ‡Equine Clinic, University of Li Li


ege, Belgium


*Corresponding author email: sue.dyson@aol.com Keywords: ataxia; discospondylitis; forelimb lameness; horse; neck locking; neck stiffness


Summary Intervertebral disc disease in the cervical and cranial thoracic vertebrae is unusual in horses and the majority of documented cases have been associated with infection and resulted in ataxia. The current retrospective study documents the clinical and imaging features, and outcome in eight


Equidae with neck stiffness forelimb lameness (n = 3) or ataxia (n = 2) assessed during a 10-year period at two clinics. The Equidae (one donkey and seven horses) ranged in age from 1.5 to 12 years (median 5.5 years). The duration of clinical signs ranged from 1 to 6 months (median 1.5 months). The donkey had a depressed demeanour. All Equidae had reduced range of neck movement. The donkey and one horse showed mild and severe ataxia respectively. Two horses showed a propensity to stumble on each forelimb, one of which exhibited forelimb lameness on the lunge or ridden. Two additional horses showed lameness in hand. One horse experienced ‘neck locking’ during grazing. Radiological abnormalities were identified involving the intervertebral symphysis between the sixth cervical vertebra (C6) and C7 in four Equidae; in two horses the articulation between C7 and the first thoracic vertebra (T1) was involved. One horse had abnormalities of the intervertebral symphyses of both C7 and T1, and T1 and T2. In one horse the articulation between C2 and 3 was affected. The donkey was treated with a prolonged course of doxycycline and improved. An advanced dressage horse returned to full-function after surgical fusion of the affected intervertebral symphysis. Intervertebral disc disease is a rare cause of neck stiffness lameness or ataxia.


Introduction


Discospondylitis is an inflammatory condition involving the vertebral bodies adjacent to the intervertebral symphysis (Nomina Anatomica Veterinaria 2005) and their associated intervertebral disc. Discospondylitis in the cervical and cranial thoracic vertebral column is an unusual condition, to which there is only limited reference in the equine literature (Adams et al. 1985; Hillyer et al. 1996; Speltz et al. 2006; Sweers and Carsten 2006; Alward et al. 2007; Garcia et al. 2015). Most reports describe the condition in adult horses and clinical signs have included neck stiffness, neck pain, a stiff or short- stepping forelimb gait and forelimb lameness. Ataxia is also reported as a clinical sign, associated with protrusion of disc material into the vertebral canal (Foss et al. 1983; Nixon et al. 1984; Adams et al. 1985; Stadler et al. 1988; Furr et al. 1991;


Hillyer et al. 1996; Colbourne et al. 1997; Sweers and Carsten 2006; Garcia et al. 2015). Infection has been recognised as the cause in the majority of horses (Foss et al. 1983; Nixon et al. 1984; Adams et al. 1985; Stadler et al. 1988; Furr et al. 1991; Hillyer et al. 1996; Colbourne et al. 1997; Sweers and Carsten 2006; Garcia et al. 2015) but attempts to identify the aetiological agent were largely unsuccessful. The aetiology of intervertebral disc disease in other reported cases remains unclear, although trauma has been reported (Adams et al. 1985; Speltz et al. 2006; Denoix 2007). Previous surveys of 17 horses from 3 months to 19 years of


age (Yovich et al. 1985) and 103 horses from birth to 23 years of age (Bollwein and Hanichen 1989), had indicated that the cervical intervertebral discs consist of fibrocartilage, with no nucleus pulposus. Age-related degenerative changes were identified, but even with severe disintegration of the discs, no related clinical signs had been recognised. However, a recent gross and histological study of the intervertebral discs of 33 Warmblood horses demonstrated that there was a nucleus pulposus and annulus fibrosus which were similar in structure to dogs and people, although the distinction between the regions was much less clear (Bergmann et al. 2018). Grade 4 and 5 degenerative changes (on a scale of


0–5) were found in 36% of horses in the segment between the fifth cervical (C5) and first thoracic (T1) vertebrae, which was a considerably higher frequency of occurrence than elsewhere in the vertebral column. It has been suggested that disc degeneration may increase intervertebral mobility, and associated dorsal bulging of the dorsal longitudinal ligament could potentially contribute to spinal nerve root compression at the entrance to the intervertebral foramen (K. Whitwell, personal communication, cited by Dyson 2011). The purpose of this report was to describe the history,


clinical and imaging features of intervertebral disc disease in eight Equidae, in six of which ataxia was not observed.


Materials and methods Case records from the University of Li


ege,


437


ege and the Animal


Health Trust (AHT) from 2008 to 2018 were interrogated to identify Equidae (D1 and H2–8, Table 1) with a diagnosis of cervical intervertebral disc disease. All animals underwent comprehensive static and dynamic physical examinations, repeated on several occasions. Horses 5–8 were evaluated moving on the lunge and ridden. Horse 6 underwent diagnostic analgesia of the lame forelimb (Bassage and Ross 2011). Ultrasound-guided (Nielsen et al. 2003) intra-articular


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