VETcpd - Ophthalmology Peer Reviewed Roser Tetas DVM MSc DipECVO MRCVS In 2006, Roser Neuro-ophthalmology: received her veterinary The approach to Horner’s syndrome degree from the University of Barcelona, Spain. Horner’s syndrome presents with several clinical signs (miosis, enophthalmos, Following which upper eyelid ptosis and protrusion of the third eyelid) secondary to the loss she undertook a of sympathetic innervation to the eye. Horner’s syndrome is classified as Masters of Science first, second or third order, according to where the lesion is located within and a rotating the neurological pathway. This article reviews the neurological pathway, the internship in Small Animal Medicine clinical signs and causes, as well as, the different steps needed for the and Surgery at the same university. diagnosis of Horner’s syndrome. After some time in general practice, Roser completed an ophthalmology Key words: Horner’s syndrome, neuro-ophthalmology, anisocoria, internship in 2012 at the Animal Health sympathetic innervation Trust, followed by a European College Veterinary Ophthalmology approved residency in the same institution. Roser Introduction is now a lecturer in ophthalmology at the Horner’s syndrome is a term used to nerve and terminates at the cranial cervical Royal Veterinary College, and an RCVS define a group of clinical signs related ganglion where the pregangionic neurons and European Recognised Specialist in to the loss of sympathetic innervation to synapse on the postganglionic neurons. Veterinary Ophthalmology. She is also the eye. Understanding the sympathetic The cranial cervical ganglion is located secretary of the British Association of supply to the eye, as well as the ventromedial to the tympanic bulla (De Veterinary Ophthalmologists. Roser is neurological pathway, is paramount if Lahunta and Kent 2015a). interested in all aspects of veterinary the clinician is to recognise the clinical It is important to consider that the brachial ophthalmology, but has a particular signs, plan an appropriate diagnostic plexus is made up of contributions from interest in corneal disease, all aspects approach and treat cases with Horner’s nerve roots arising from C6 to T1 spinal of neuro-ophthalmology and equine syndrome. Moreover, it is also important segments. Therefore, part of the sympa- ophthalmology. In 2018, Roser gained to consider the variability of the clinical thetic supply to the eye is closely associated the PGCert in veterinary education and is signs associated with Horner’s syndrome with the innervation to the thoracic limb. a Fellow of the Higher Education Academy. depending on where the lesion is located. Therefore, Horner’s syndrome may be seen associated with monoparesis of the thoracic Sympathetic supply to the eye Jesus Diaz Bujan MRCVS limb (Penderis 2013). There are three groups of neurons Jesus Diaz involved in the sympathetic innervation Third order neurons: The pathway received his of the eye: first, second and third order from the cranial cervical ganglion to the veterinary degree neurons (Penderis 2013) (Figure 1). ocular structures is poorly described. Third from the University order neurons (or postganglionic fibres), of León in 2010, First order neurons: The cell bodies of arise from the cranial cervical ganglion and following three the first order neurons are located within run close to the middle ear cavity to enter years in small the hypothalamus and the rostral midbrain. the calvarium via the tympano-occipital animal practice; Their axons run caudally within the lateral fissure. At the level of the middle cranial he undertook a tectotegmentospinal tract to the T1 to T3 fossa, the postganglionic fibres join the rotating internship spinal cord segments, where they synapse ophthalmic branch of the trigeminal nerve at the Animal Health Trust in 2016, on the second order neurons. The second as it enters the orbit through the orbital fis- followed by an ophthalmology internship order neuronal cell bodies are located in sure (De Lahunta and Kent 2015a). Togeth- at a private referral centre. In 2018, the lateral grey column of the spinal cord er with fibres of the ophthalmic nerve, the he started an ECVO ophthalmology (De Lahunta and Kent 2015a). postganglionic fibres course rostrally in residency programme at the Royal the periorbita as the nasociliary nerve and Veterinary College. Jesus holds a PGCert Second order neurons: The second enter the globe via the long ciliary nerves in veterinary ophthalmology. He is order neurons (or preganglionic fibres), interested in all aspects of veterinary leave the spinal cord to join the thoracic (Christensen 1936). ophthalmology, but has a particular sympathetic trunk. This courses rostrally Therefore, the long ciliary nerves provide interest in intraocular surgery, neuro- inside the thorax alongside the vertebral both sympathetic efferent fibres and ophthalmology and glaucoma. bodies. The preganglionic neuronal axons somatosensory afferent fibres to the continue cranially in the trunk, pass eye (Christensen 1936). The pupillary through the cervicothoracic and middle sympathetic fibres run within the SUBSCRIBE TO VETCPD JOURNAL cervical ganglia, and course rostrally within suprachoroidal space towards the ciliary the neck in the cervical sympathetic trunk, body, iris dilator and iris sphincter muscles. Call us on 01225 445561 which is located in the carotid sheath. Moreover, the sympathetic fibres also or visit www.vetcpd.co.uk At the level of the head, the cervical innervate the smooth muscles of the sympathetic trunk separates from the vagus periorbita, including the orbitalis muscle Page 34 - VETcpd - Vol 6 - Issue 4 VETcpd - Ophthalmology (Ofri 2013). Cats have smooth muscle fibres Second order Horner’s syndrome in the third eyelid which are also innervated appears secondarily to lesions in the by the sympathetic system (Nuyttens and T1-T3 spinal cord segments, or in the Simoens 1995). The innervation of all these cranial thoracic sympathetic trunk muscles will be compromised in cases with towards the cranial cervical ganglion Horner’s syndrome. (De Lahunta and Kent 2015a). Signs associated with second order Horner’s Clinical signs and causes may include ipsilateral thoracic limb of Horner’s syndrome paresis/paralysis and loss of contraction In small animals, the lack of sympathetic of the ipsilateral trunci muscle (Wheeler innervation to the eye results in ipsilateral et al. 1986). Lesions within the thoracic miosis, enophthalmos, protrusion of the cavity (e.g. abscesses or neoplasia) third eyelid and upper eyelid ptosis (Figure (Ferreira et al. 2005; Ofri 2013) or neck (e.g. trauma, iatrogenic or neoplasia) Figure 5: Eight-year-old male neutered Maine Coon diagnosed with left sided Horner's syndrome and facial 2). This collection of clinical signs is paresis secondary to bilateral middle ear effusion, more marked on the left side. A, Notice the marked third commonly known as Horner’s syndrome. (Frye 1973; Kern et al. 1989; Boydell eyelid protrusion and miosis in the left eye. B, CT image of the head of the same patient (bone window). Both However, the clinical presentation may et al. 1997; Ofri 2013; Viscasillas et tympanic cavities are filled with material (white asterisks); however, the left side is more affected than the vary depending on where the underlying al. 2013) may also be associated with right. The left frontal sinus (not shown) was also affected. lesion is located. ipsilateral Horner’s syndrome (Figure 4). Third order Horner’s presents Figure 6: Eleven-year-old male neutered secondarily to lesions affecting the Boxer diagnosed with bilateral facial nerve sympathetic pathway from the cranial paralysis, left Horner's syndrome and left Figure 1: Neuroanatomic pathway for sympathetic innervation to the eye. (1) lateral tectotegmentospinal cervical ganglion to the orbit (Figure 5). neurogenic keratoconjunctivitis sicca, tract; (2) T1 to T3 spinal cord segments; (3) vagosympathetic trunk; (4) carotid sheath; (5) cranial Other clinical signs commonly seen in secondary to bilateral otitis media and cervical ganglion; (6) tympanic bulla; (7) tympano-occipital fissure; (8) orbital fissure interna. The patient presented with bilateral conjunction with third order Horner’s lip drooping, left xeromycteria (dry nose) and are those associated with ipsilateral otitis keratoconjunctivitis sicca (dry eye) as well media or interna, vestibular disease and/ as left Horner’s syndrome (with third eyelid or facial neuropathy (De Lahunta and protrusion, miosis, enophthalmos and upper eyelid ptosis). Notice the presence of mild Kent 2015b) (Figure 6). mucoid discharge in the left eye as well as the Middle ear inflammation can involve scattering of the light reflection on the ocular the facial nerve as it courses through surface, which are signs of ocular dryness. the facial canal located in the petrosal Figure 2: Five-year-old male neutered Domestic Short portion of the temporal bone. This Hair cat with left sided Horner's syndrome. Notice the third eyelid protrusion, miosis, enophthalmos and up- occurs because the facial canal runs in per eyelid ptosis in the left eye close proximity to the tympanic cavity where it lacks a bony wall. Subsequently, First order Horner’s syndrome may be the facial nerve is separated from associated with clinical signs related the tympanic cavity only by loose Idiopathic Horner’s syndrome affects within the iris: the constrictor pupil- to disease affecting the hypothalamus, connective tissue (De Lahunta and Kent both cats and