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Nuchal Crest Avulsion Fracture in 2 Horses: a Cause of Headshaking

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Nuchal Crest Avulsion Fracture in 2 Horses: a Cause of Headshaking Clinical communication — Kliniese mededeling Nuchal crest avulsion fracture in 2 horses: a cause of headshaking A Voigta, M N Sauleza* and C M Donnellana ally to the 1st larger opacity. The nuchal ABSTRACT crest appeared irregular and was sus- The medical records of 2 Thoroughbred horses that developed headshaking after blunt pected to be the corresponding fracture trauma to the occipital region are reviewed. The history, signalment, clinical signs, diagnostic bed. methods, diagnosis and treatment were recorded in each case. Both horses displayed head- Ultrasonographic examination was shaking, while one horse repeatedly lifted its upper lip and pawed excessively at the performed of the nuchal ligament with a ground. In both horses, diagnostic imaging of the occipital region revealed avulsion fragments 7.5 MHz T-Piece linear array multi- of the nuchal crest and a nuchal desmitis in association with hyperfibrinogenaemia. The frequency transducer. The right nuchal presence of an avulsion fragment of the nuchal crest with associated nuchal desmitis ligament had a 23 × 8.4 mm, diagonally should be considered in horses presenting with headshaking and may respond favourably up to 18 mm, hyperechoic line which cast to conservative therapy. a clean acoustic shadow 28 mm caudally Keywords: equine, headshaking, nuchal crest desmitis, trauma. to the nuchal crest. An additional 2.7 mm Voigt A, Saulez M N, Donnellan C M Nuchal crest avulsion fracture in 2 horses: a cause smaller structure could be seen 8 mm of headshaking. Journal of the South African Veterinary Association (2009) 80(2): 111–113 (En.). cranially to the large one. The right Department of Companion Animal Clinical Studies, Equine Internal Medicine, Faculty of nuchal ligament measured 1.07 cm2 vs Veterinary Science, Private Bag X04, Onderstepoort, 0110 South Africa. 0.69 cm2 on the left. The nuchal ligament on the right lost its homogenous appear- ance and the ligament fibres appeared to INTRODUCTION racehorse gelding developed acute onset be hypoechoic. Although headshaking is a widely of spontaneous and repetitive vertical, Following interpretation of diagnostic recognised disorder, a precise aetiology horizontal and rotary movement of his imaging results, avulsion fragments of the is seldom found and treatment is often head and neck of 3-week duration. The nuchal crest, with an associated nuchal unrewarding. The purpose of this case headshaking varied in intensity through- desmitis caused by suspected blunt report is to review the clinical records of 2 out the day and occurred both at rest and trauma to the occipital region constituted horses that developed headshaking after during exercise. A lateral radiograph the most significant finding. Serum bio- blunt trauma to the occipital region with (Fig. 1) of the occipital region revealed chemical analysis revealed hyperfibrino- resultant nuchal crest avulsion fracture a 22 × 15 mm mushroom-shaped trabe- genaemia (7 g/ , reference range <4 g/ ) and associated nuchal desmitis. The sig- culated mineral opacity visible 30 mm which may have been due to inflamma- nificance of the abnormalities was con- caudal to the nuchal crest with an addi- tion of the nuchal ligament. firmed by the infiltration of a local tional 6 mm opacity located 10 mm crani- The gelding was managed with anaesthetic agent and an anti-inflamma- tory substance. This report further explores the heterogeneity of this syn- drome by discussing the causes, clinical signs, diagnostic procedures and treat- ments that may be considered in horses with headshaking. MATERIALS AND METHODS The clinical records of 2 horses admitted between October 2007 and June 2008 to the Equine Clinic of the Onderstepoort Veterinary Academic Hospital (OVAH) that had a primary complaint of head- shaking are reviewed. The history, signal- ment, clinical signs, diagnostic methods, diagnosis and treatment were recorded in each case. CASE HISTORY Case 1 A 12-year-old, retired Thoroughbred aDepartment of Companion Animal Clinical Studies, Equine Internal Medicine, Faculty of Veterinary Science, Private Bag X04, Onderstepoort, 0110 South Africa. Fig. 1: Lateral view of the occipital region of a 12-year-old Thoroughbred racehorse, show- *Author for correspondence. ing a 22 × 15 mm mushroom-shaped trabeculated mineral opacity located caudal to the E-mail: [email protected] nuchal crest (arrow) anda6mmopacity located cranial to the 1st larger opacity (arrow- Received: March 2009. Accepted: May 2009. head) (Horse 1). 0038-2809 Jl S.Afr.vet.Ass. (2009) 80(2): 111–113 111 phenylbutazone (Phenylbutazone BP, Kyron Laboratories Pty Ltd) (2.2 mg/kg, q12h, PO), dexamethazone (Kortico, Bayer Ltd.) (0.1 mg/kg, q24h, PO) and trimethoprim-sulfamethoxazole (Purbac®, Aspen Pharmacare) (25 mg/kg, q12h, PO) to reduce swelling caused by the suspected trauma to the poll. Local infiltration con- sisting of 45 mg methylprednisolone acetate (DepoMedrol™, Pfizer), 100 mg lignocaine hydrochloride (Lignocaine Injection 2 %, Bayer Ltd.) and Sarapin® (High Chemical Company) was adminis- tered in the nuchal ligament in the region of the nuchal fragment. No further head- shaking episodes occurred following treatment and the gelding was discharged from the clinic. Follow-up consultation 12 weeks after discharge indicated that no headshaking behaviour had been noticed. Case 2 Fig. 2: Lateral oblique radiographic view of the occipital region of a 5-year-old Thorough- A 5-year-old, retired Thoroughbred race- bred racehorse, showing mineral opacities ranging from 5 to 10 mm (arrow) adjacent to the horse gelding developed signs of head- nuchal crest external occipital protruberance (Horse 2). shaking at rest and during exercise of 6-month duration. Clinical symptoms nuchal ligament in the region of the bony tion on the occiput2. This may be seen as included lifting of the upper lip, pawing fragment. After performing the infiltra- an incidental finding, but affected horses excessively and resting his head on the tion, the gelding was lunged and no head- tend to resist the reins, find difficulty in ground. Physical examination revealed shaking behaviour was noticed. Follow- flexion at the poll and may rear or shake hypertrophy of the ventral neck muscles. up consultation 1 year after discharge the head2,4. A radiograph (Fig. 2) of the occipital region indicated that the gelding’s headshaking Horses with insertional desmitis of the showed mineral opacities ranging from 5 behaviour had decreased by 90 %. nuchal ligament or injury to the tendon to 10 mm adjacent to the nuchal crest of insertion of semispinalis may have a external occipital protruberance which DISCUSSION tendency to shake their heads4. These appeared irregular and was suspected to In a retrospective study of 100 horses injuries usually occur due to trauma to be the corresponding fracture bed. These with headshaking, a specific aetiology the region or an excessive amount of mineral opacities had a rounded appear- could not be identified in 90 % of the cases lunging exercise while restricted with side ance and were considered to be due to and in only 2 horses could it be shown or draw reins4. In a report of insertional trauma to the poll region which occurred that correction of the disorder led to desmopathy of the nuchal ligament, several months previously. elimination of clinical signs6. Several 12 horses presented with various clinical Ultrasonographic examination of the underlying diseases can present with signs such as reluctance to bend the head, nuchal ligament was performed as de- headshaking signs, but the majority of stiffness of the neck, excessive head turn- scribed above. An 11 mm hyperechoic cases are idiopathic7,8,17,18. Irritation by ing and headshaking when exercised1. line could be seen casting an acoustic insects, dental disease, guttural pouch Diagnostic procedures performed on the shadow 10 mm to the right of the midline mycosis and empyema, otitis media and 12 horses indicated exostosis of the and 11 mm caudoventral to the nuchal interna, cranial nerve disorders, ocular protuberantia occipitalis, calcification of crest. Additional smaller concave hyper- disease, subepiglottal cyst, premaxillary the ligamentum nuchae or insertion echoic lines up to 5 mm on the right and bone cyst, ethmoid haematoma, fracture desmopathy1. 3 mm on the left of the midline were of the frontal bone, maxillary osteoma, As found in this report, horses with observed. The nuchal ligament on the protozoal myeloencephalitis and Trom- headshaking commonly show uncontrol- right lost its homogenous appearance bicula autumnalis larval infestation are all lable shaking of the head in a vertical, hor- and the ligament fibres appeared to be considered possible causes5,6,9,14,16,20. izontal or rotary direction without any hypoechoic with associated loss of fibre Nuchal crest avulsion fractures with apparent physical stimulus7,18. Other alignment. The right nuchal ligament corresponding nuchal ligament desmitis signs include nose rubbing, striking at the measured 1.9 cm2 vs 0.85 cm2 on the left. was the most significant finding in the 2 nose with the forelegs, head pressing and Following interpretation of diagnostic cases in this report. Furthermore, the head- active avoidance of light, warmth or wind imaging results, an avulsion fragment of shaking behaviour decreased in both on the face. Worsening of clinical signs with the nuchal crest, with an associated after the nuchal ligament was infiltrated exposure to light are common features of nuchal desmitis was the most significant
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