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EQUINE VETERINARY EDUCATION / AE / AUGUST 2020
analgesia of the left articular process joint between the seventh cervical (C7) and T1 vertebrae was performed in Horse 7. Blood samples were collected for measurement of white blood cell count, fibrinogen and serum haptoglobin (D1), or serum amyloid A (H4) concentrations. Lateral–lateral radiographs of the cervical and cranial thoracic vertebrae were acquired (Butler et al. 2017). Images were interpreted by a Diplomate (V.B.) or an Associate (S.D.) of the European College of Veterinary Diagnostic Imaging.
Results
There were one donkey (D1, Table 1) and seven horses (H2– 8), which ranged in age from 1.5 to 12 years (mean 6.3 years; median 5.5 years). There were five geldings, two stallions and one mare, used for general purpose riding (n = 2, including unaffiliated competition), dressage (n = 2), eventing (1), endurance (1) and driving (1); one horse was unbroken. Breeds included three Warmbloods and one each of Thoroughbred cross, Highland Pony, Akhal T
ek e and a pony.
Height ranged from 142 to 167 cm (n = 4), Cases 5–8; mean 154.8 cm. Bodyweight ranged from 328 to 575 kg (median 480 kg, mean 455 kg).
Clinical features The duration of clinical signs ranged from 1 to 6 months (mean 2.4 months, median 1.5 months). The donkey had a depressed demeanour and low head posture. All horses had a normal neck posture at rest, but when passive neck flexion was assessed using baited stretch exercises, flexion was limited. Neck muscle development was generally poor in five horses (H 3,4,5,7,8), but no focal muscle atrophy was observed. There was no patchy sweating, hyperaesthesia or allodynia, but Horse 5 showed a marked pain response when the caudal aspect of the left side of the neck was palpated when the horse exhibited neck ‘locking’. All Equidae experienced difficulties in lowering the neck to graze, exhibiting a straddled stance with both forelimbs widely separated (D1, H2–4 and 6–8). Horse 3 would not eat from the ground and Horse 7 could not reach the ground to eat. Horse 5, after grazing for several minutes, developed neck ‘locking’: the neck became fixed in a lowered position, sometimes with the neck bent to the right (Fig 1a). He tended to cross the forelimbs while grazing, or had the left front fetlock knuckled forwards. The horse walked forwards
with the neck fixed in a low position. This persisted for up to 10 minutes and would then resolve spontaneously. When evaluated moving in hand in straight lines, five
horses (H 2,5,6,7,8) had a stiff neck posture. When turned in small circle these horses, in addition to Horse 4, had reduced range of motion of the neck. Two Equidae showed mild (D1, grade 1 – forelimbs) and severe (H2, grade 3 – hindlimbs > forelimbs) ataxia respectively (using a 0–4 ataxia-grading scale [Reed 2003; Olsen et al. 2014]). No other animal showed evidence of ataxia or weakness. However, Horses 2 and 6 had a propensity to stumble on each forelimb. For Horse 6 this was most evident when ridden. Horses 4, 6 and 7 exhibited forelimb lameness. Forelimb lameness was evident in hand for Horses 4 and 7, but was only apparent on the lunge or ridden in Horse 6. Horses 5 and 8 had reduced range of motion of the neck on the lunge. Horse 6 was consistently more reluctant to trot willingly on the right rein on the lunge, although paradoxically right forelimb lameness was more obvious on the left rein compared with the right rein. Hopping-type forelimb lameness was not observed. When ridden two horses (H 5,6) tilted the head and neck, with the nose to the right and to the left respectively. Horse 5 had unrelated bilateral hindlimb lameness. The right forelimb lameness in Horse 6 was not improved
by any local analgesic technique and showed deterioration after palmar metacarpal (subcarpal) nerve blocks. The left forelimb lameness in Horse 7 was improved after intra- articular analgesia of the left Ce7-T1 articular process joint, and the horse could then easily lower the head and neck to eat from the ground. Diagnostic analgesia was not performed in Horse 4. Haematological and serum biochemistry results were
within the normal range in all horses. The donkey had mild neutrophilia and an increased serum haptoglobin
concentration, but the total blood leucocyte count and fibrinogen concentration were within the normal range.
Radiological findings The radiological features are summarised in Table 2 (Figs 1– 4b–). Three Equidae (D1 and H2,6) had intervertebral disc disease involving the intervertebral symphysis between C6 and 7; in three horses (H3,4,7) the articulation between C7 and T1 was involved. One horse (H5) had abnormalities of the intervertebral symphyses of both C7-T1 and T1–T2. In one horse (H8) the articulation between C2 and 3 was affected.
TABLE 1: Signalment, work discipline, duration of clinical signs (months) and summary of clinical features of eight Equidae with intervertebral disc disease of the cervical or cranial thoracic vertebrae
Identity D1
H2 H3 H4
H5 H6 H7 H8
Age (years)
5
1.5 12 6
8 5 5 8
Work Breed discipline
Donkey Driving WBL WBL
Akhal T
TB X ek e E
Highland GP Pony GP WBL
Dr (N)
5 2 1 1
+
+ +
+
Dr, dressage (PSG = Prix St Georges; N = Novice); E, Eventing; GP, general purpose riding; LDR, long distance riding (20 km); TB x, Thoroughbred cross; WBL, warmblood.
© 2019 EVJ Ltd
Unbroken Dr (PSG) LDR
1 6 2
1.5
Duration of clinical signs
Depression +
+
Forelimb lameness Stumbling Ataxia
+
+ +
Neck locking
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