Received: 1 September 2020 Revised: 8 February 2021 Accepted: 16 June 2021 DOI: 10.1002/vrc2.141 CASE REPORT Horses and other equids Basisphenoid bone fracture in two juvenile horses with different clinical presentation Valentina Vitale Eduard Gascón Ignacio Corradini Lara Armengou Eduard Jose-Cunilleras Departament de Medicina i Cirurgia Animals, Abstract Universitat Autonoma de Barcelona Hospital Clinic Veterinari, Barcelona, Spain Basilar skull fractures in horses can occur at any age, although young horses are partic- ularly prone to this type of injury. This manuscript describes two foals with a basisphe- Correspondence noid bone fracture, with clinical presentations ranging from mild neurological signs up Lara Armengou, Departament de Medicina i Cirur- to severe neurological compromise. The absence of neurological signs does not exclude gia Animals, Universitat Autonoma de Barcelona Hospital Clinic Veterinari, Barcelona, Spain. a fracture of this bone, as lethargy and retropharyngeal swelling may be the only clin- Email: lara.armengou@uab.cat ical signs. Radiography can help define skeletal trauma involving the basilar region of the head, but superimposition of complex skull anatomy limits its use. Endoscopy of the [Correction added on 27 July 2021, after first guttural pouches region can be also helpful, but it does not provide enough evidence for online publication: the order of author names a diagnosis. Thus, computed tomography is the optimal imaging technique for a rapid was updated.] and straightforward diagnosis, as it is superior to radiography defining the type of frac- ture and the location of the fragments as well as the soft tissue involvement. BACKGROUND CASE PRESENTATION Basilar skull fracture (BSF) occurs most commonly after a Case  horse rears over backwards and strikes the ground with the poll of the head.1,2 Hyperextension of the head leads to con- A rescued 8-month-old crossbred colt, approximately 250 kg traction of the longus capitis muscle, with the potential for a bodyweight, was referred to Unitat Equina-Fundació Hos- resultant fracture with or without displacement of fragments pital Clínic Veterinari, Universitat Autònoma de Barcelona. of the basisphenoid and basioccipital bones.3,4 Although Previous to referral, the colt felt over backward during the the traumatic event can occur at any age, young horses are oral administration of an anthelmintic drug. On admission, particularly prone to this type of injury as they are more likely the foal showed lethargy and an inspiratory rasping noise. to resist head restraint.5 Clinical signs are highly variable and On complete neurological examination, no other deficits were the extent of structural damage can be difficult to determine observed. clinically.6 BSFs have a poor prognosis and the diagnosis by Radiographs of the skull were taken under sedation, using a radiographic examination is difficult, especially if there are fixed system generator (SHF 835; SEDECAL, Algete, Madrid, no displaced bone fragments.7–9 Neurologic damage can be Spain), and an X-ray tube (Varian G-292; Varex Imaging the result of either direct trauma by displaced bone fragments Corporation, Las Vegas, NV, USA) at a film focal distance of or intracranial haemorrhage, inflammation and secondary 100 cm. Left to right latero-lateral and dorsoventral views of brain injury.1 The enhanced resolution and sensitivity of the base of the skull were obtained using a Konica Minolta CT make it the ideal imaging modality for the diagnosis of Regius model 170 computed radiology (CR) equipment (Kon- skull fractures in horses.8,10 Compared to radiography, it also ica Minolta). On the lateral view, two osseous fragments, provides the possibility to precisely locate the fracture site 4.5 × 11.6 mm and 16.3 × 8.6 mm were seen just ventral to within specific areas of the base of the skull. To date, there is a the basioccipital bone (Figure 1a). Soft tissue opacification limited number of published studies or case reports of BSF in of the guttural pouches and ventral deviation of the dor- horses. This article describes the clinical presentation of two sal pharyngeal wall were also observed. On a dorsoventral foals with a basisphenoid fracture, their diagnostic imaging view, a 2 × 9.5 mm fragment displaced to the right side findings and outcome. and a lack of alignment between the basisphenoid and the This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2021 The Authors. Veterinary Record Case Reports published by John Wiley & Sons Ltd on behalf of British Veterinary Association Vet Rec Case Rep. 2021;9:e141. wileyonlinelibrary.com/journal/vrc2  of  https://doi.org/10.1002/vrc2.141  of  Veterinary Record Case Reports basioccipital bone was observed (Figure 1b). Endoscopy of the upper airways revealed severe oedema and hyperaemia LEARNING POINTS/TAKE HOME MESSAGES of the nasopharynx and it was impossible to gain entrance to the guttural pouches. BSF was strongly suspected and CT of ∙ BSF should be suspected in horses with a history of the skull was performed under general anaesthesia with the a fall over backwards. animal positioned in dorsal recumbency. The CT scan was ∙ The absence of signs of intracranial trauma performed using a 16 slices scanner (Brivo CT385; General does not exclude a fracture at the basisphenoid- Electric Healthcare, Chicago, IL, USA) and reviewed in bone basioccipital suture. Lethargy and retropharyngeal and soft tissue windows. The scan parameters were 120 kV and swelling may be the only presenting clinical signs. 159 mA, and slice thickness of 1.25 mm and a gap of 0.6 mm. ∙ CT is superior to radiography in defining the type CT findings revealed a severely comminuted fracture of the of fracture and the location of the fragments as well basisphenoid-basioccipital junction, with a large osseous as the soft tissue involvement. fragment (11.5 × 7.2 mm in the dorsal plane) displaced to the ∙ Delayed lesions of the cranial nerves may occur. left side, and a second fragment (8.2 × 3.6 mm in the dorsal plane) displaced to the right side, with a displacement of the basioccipital bone to the right of the sagittal plane (Figure 2). A soft tissue attenuating structure was detected in the guttural lateral view, a fracture at the basisphenoid-basioccipital junc- pouches area, compatible with haemorrhage or hematoma. A tion was suspected (Figure 4a). On the dorsoventral view, diagnosis of BSF was reached. an 11.5 × 8.9 mm osseous fragment was seen on the left The colt was hospitalized and treated with oral suxibu- side of the basisphenoid-basioccipital suture. Partial soft tis- zone (3.3 mg/kg every 12 hours) and intravenous antimi- sue opacification of the guttural pouches was also present crobial therapy with sodium penicillin (22000 UI/kg every (Figure 4b). 6 hours) and gentamicin (6.6 mg/kg every 24 hours). The A CT of the skull was performed under general anaesthe- clinical progression was good, the inspiratory stridor disap- sia with the filly positioned in dorsal recumbency. The scan peared and the mental status improved over the first week of parameters were 120 kV and 35 mA, and slice thickness of hospitalisation. The foal was discharged 2 weeks after admis- 1.25 mm and a gap of 0.6 mm. Iobiditriol, an iodinated non- sion with a recommendation to continue stall rest, avoid- ionic contrast (Xenetix 300 mg iodine/ml; Laboratorios Far- ance of manipulation of the head and continuation of ther- macéuticos Guerbet, Madrid, Spain) was injected via intra- apy with antibiotic and NSAID for another 2 weeks. Upon re- arterial 16G BD-Angiocath catheter (BD, Eysins, Nyon, CH) evaluation, 1 month later, neurological examination was nor- in the right common carotid artery using a pressure injector mal, except for a mild right head tilt detectable while eating. (Nemoto A-60; Nemoto Kyorindo Company, Tokyo, Japan). Radiographic re-evaluation of the skull revealed callus bone As previously described,11 a continuous arterial infusion pro- formation at the fracture point. No obliteration of the guttural tocol during scanning was used with an injection rate of 2 ml/s pouches or displacement of the dorsal pharyngeal wall were (100 ml of contrast injected). The post-contrast scan was ini- observed (Figure 3). Nine months after referral, the head tilt tiated with a 3 seconds delay from the start of the contrast had resolved and the animal had atrophy of the left masseter medium administration. muscle attributed to neurological atrophy likely caused by a CT findings revealed a severely comminuted fracture of lesion of the left mandibular nerve. No other deficits of the the basisphenoid-basioccipital physeal junction (Figure 5). A neurological examination were observed. Eighteen months large fragment of 23.3 × 7.6 mm was located in the right after referral, the owner reported a good outcome with sub- ventrocaudal aspect of the basisphenoid bone. Multiple frag- tle remaining difficulties when eating. ments were located in the left dorsolateral aspect of the basioc- cipital bone. A soft tissue attenuating structure was detected Case  in the left guttural pouch, compatible with haemorrhage or hematoma. The diagnosis of BSF was confirmed. Due to the A 10-month-old Crossbred filly, approximately 400 kg body- poor prognosis and the absence of good clinical progression, weight, was referred with a history of a fall over backwards a the filly was euthanized. A complete post-mortem examina- few hours prior to admission. Since the fall, the filly remained tion was not performed. recumbent, unconscious and with continuous bilateral spon- taneous horizontal nystagmus. The referring veterinarian administered intravenously a dose of 4 ml/kg 7.5% hyper- DISCUSSION tonic saline solution, flunixin meglumine (0.5 mg/kg) and dexamethasone (0.1 mg/kg). The filly was referred under gen- In the present case report, both horses were diagnosed with eral anaesthesia with intravenous ketamine (1.1 mg/kg) and a basisphenoid fracture. Despite having similar fracture loca- diazepam (0.5 mg/kg). On admission, the animal was uncon- tions, clinical signs varied significantly, ranging from mod- scious and, when the effects of anaesthesia waned, the filly erate to profound neurological signs. The two cases showed remained stuporous with persistent bilateral continuous hor- deficits of the cranial nerves at some point of the clinical izontal, vertical and rotatory spontaneous nystagmus. Pupil- progression. Case 2 had apparent involvement of either cra- lary light reflexes were present but the pupils were anisocoric, nial nerve (CN) III or VIII, whereas case 1 developed atro- with mydriasis of the right pupil. No clear attempts to stand phy of the left masseter muscle consistent with a delayed onset or gain the sternal position were observed. lesion of the mandibular branch of the trigeminal nerve (CN Lateral and dorsoventral radiographs of the skull were taken V). There is a paucity of reports on the neurological signs using the equipment and techniques described above. On the associated with BSF in horses. Furthermore, cranial nerve Veterinary Record Case Reports  of  F I G U R E  Radiographic projections of the skull of case 1: (a) latero-lateral view in which two osseous fragments ventral to the basioccipital bone are observed (arrows); (b) dorsoventral view in which a bone fragment and a lack of alignment between the basisphenoid and the basioccipital bone is observed (arrow). Almost complete soft tissue opacification of the guttural pouches is also present F I G U R E  Slices of CT scan study of the head of case 1: (a) transverse views – on the left, the soft tissue algorithm andon the right, the osseous algorithm. The left side of the patient is on the right side of the images; (b) sagittal slice in the bone window. The two biggest fragments of the comminuted fracture of the basisphenoid-basioccipital physeal junction are evident in these images dysfunction is not described in most of the reports of BSF, due to the inherent difficulty in performing a full neurologi- cal examination in this subset of equine patients. There is one report of a horse with optic nerve damage and blindness sec- ondary to an anterior skull fracture confirmed by CT scan.6 Recently, a case of a horse with a posterior BSF with vagal nerve paralysis and suspected implication of the glossopha- ryngeal nerve has been described.12 Horses included in the present case report showed variable clinical signs, all poten- tially related to the skull fracture and intracranial inflamma- tion. Moreover, case 1 showed mild neurological signs and a good outcome, which differs from the common percep- tion of poor prognosis related to skull trauma. In particu- lar, this case showed a very exceptional clinical outcome. As mentioned, the colt showed left mandibular nerve deficits (i.e. neurogenic masseter atrophy) 9 months after the acute trauma. The delayed involvement of this particular nerve is uncommon. The mandibular nerve emerges from the fora- F I G U R E  Latero-lateral radiographic projection of the skull of case 1 men lacerum,13,14 a triangular hole in the base of the skull, after 1-month progression. Note the callus bone formation at the fracture located between the sphenoid, the apex of the petrous tempo- point. No obliteration of the guttural pouches or displacement of the dorsopharyngeal wall were observed ral and the basilar part of the occipital bones. Therefore, signs of mandibular nerve lesion might have been caused by bone remodelling observed on the radiologic follow-up in this area.  of  Veterinary Record Case Reports F I G U R E  Radiographic projections of the skull of case 2: (a) latero-lateral view; (b) dorsoventral view in which an osseous fragment is seen on the left side of the basisphenoid-basioccipital suture (arrow). Moreover, partial soft tissue opacification of the guttural pouches is also present F I G U R E  Slices of CT scan study of the head of case 2: (a) transverse views– on the left, the soft tissue algorithm andon the right, the osseous algorithm. The left side of the patient is on the right side of the images; (b) sagittal slice in the bone window. A severely comminuted fracture of the basisphenoid-basioccipital physeal junction is observed Trauma to the head, with resultant damage to intracra- tion of the nasopharynx. However, the degree of detail of the nial structures, is not uncommon in the horse.3 The avail- haemorrhage on CT in case 2 allowed for better characterisa- able literature is limited but indicates that the prognosis is tion of the soft tissue swelling and haemorrhage. guarded.3,5,8,9 Subdural haemorrhage, epistaxis, severe neu- Radiographs of the basisphenoid and basioccipital bones in rological signs and compression of the laryngeal and pha- young horses are particularly hard to evaluate and easily mis- ryngeal area leading to asphyxiation are all potential seque- interpreted because the suture line between these two bones lae of a BSF.15 Bilateral mydriasis has also been reported as remains open until 5 years of age.1,5,8,9,16 Even when the suture a sign of severe midbrain injury and as an indicator of poor line has closed, it may appear irregular in both shape and prognosis.4 BSF usually occurs at the weakest point, which in width. This makes it very hard to visualize a fracture, espe- the case of foals, is the point of junction of the basisphenoid cially if it is not displaced.8 Some authors have concluded that and the basioccipital bones.3,7 This is the area in which frac- survey radiography can help define skeletal trauma involving ture occurred in the two cases herein reported. the basilar region of the head, but superimposition of skull Haemorrhage at the level of the pharynx and guttural structures combined with the clinician’s inherent inabil- pouches can be secondary to either rupture of the rectus and ity to discriminate small differences in tissue density limit longus capitis muscles and their associated vasculature,15 or the use of radiography.8,17 Thus, CT should be considered can also originate from the vasculature and venous sinuses the optimal imaging technique for a rapid and straightfor- associated with the roof of the guttural pouches.8 In case 2, a ward diagnosis.18,19 Disadvantages of the CT technique are soft tissue attenuating structure was detected on the CT scan related to the financial cost, need of adequate facilities and within the left guttural pouch, compatible with haemorrhage trained personnel and general anaesthesia of an already or hematoma formation. Partial soft tissue opacification of compromised patient unless standing CT is available. The the guttural pouches on radiographic examination was also advantages include the provision of detailed images without present in case 1. An endoscopic examination can aid in the superimposition of anatomical structures and the ability to diagnosis of haemorrhage associated with BSF.15 During the provide a high degree of soft-tissue contrast resolution.13,14,18 endoscopy examination of case 1, it was not possible to enter Here are described two cases with a basisphenoid fracture the guttural pouches due to soft tissue oedema and deforma- with differing clinical signs. Lack of neurological signs caused Veterinary Record Case Reports  of  by a BSF may be due to absent or minimal compression of 9. Beccati F, Angeli G, Secco I, Contini A, Gialletti R, Pepe M. Comminuted the CNS. Case 1 showed only upper airway obstruction signs basilar skull fracture in a colt: use of computed tomography to aid the diagnosis. Equine Vet Educ. 2010;23(7):327–32. and the imaging findings confirmed extensive haemorrhage 10. Jose-Cunilleras E, Piercy RJ. Advanced diagnostic imaging options in and soft tissue swelling of the guttural pouches and pharyn- horses with neurological disease that localises to the head. Equine Vet geal area. The location and topographical anatomy of the frac- Educ. 2007;19(4):179–81. ture as well as the severity of the injury and secondary brain 11. Crijns CP, Baeumlin Y, de Rycke L, Broeckx BJG, Vlaminck L, Bergman damage, all contributed to the myriad of clinical signs mani- EHJ, et al. Intra-arterial versus intra venous contrast-enhanced com- puted tomography of the equine head. BMC Veterinary Research. 2016;12 fested in the cases described here. If the injury is located most (6):1–13. ventrally to the basisphenoid-basioccipital suture the preva- 12. Martin-Giménez T, Cruz AM, Barragán A, Montero E, Sanchez PG, lent signs will be epistaxis and asphyxia, while if the cerebral Caballero G, et al. Delayed onset vagus nerve paralysis after occipital parenchyma is injured neurological signs will be prevalent.8,9 condyle fracture in a horse. J Vet Intern Med. 2019;33:2780–5. 13. Levine JM, Levine GJ, Hoffman AG, Bratton G. Comparative anatomy of the horse, ox, and dog: the brain and associated vessels. Compendium ORCID Equine. 2008;3(3):153–63. Valentina Vitale https://orcid.org/0000-0003-2273-5377 14. Gonçalves R, Malalana F, McConnell JF, Maddox T. Anatomical study of cranial nerve emergence and skull foramina in the horse using magnetic Eduard Gascón https://orcid.org/0000-0002-8532-4236 resonance imaging and computed tomography. Vet Radiol Ultrasound. Ignacio Corradini https://orcid.org/0000-0002-4053-8863 2015;56(4):391–7. Lara Armengou https://orcid.org/0000-0003-4715-7323 15. 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