Intervertebral disc disease of the cervical and cranial thoracic vertebrae in equidae: eight cases

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.