Neurological examination of the horse

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Ross Stafford
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1 Neurological examination of the horse

2 Aim of the neurological examination Is there a neurological disease? Anatomical location of the problem? Diagnosis? Are there therapeutic options? What is the prognosis?

3 Nerve system anatomy CNS - brain, spinal cord PNS - peripheral nerves (motor, sensitive) Autonomic nervous system - sympathetic, parasympathetic

4 Brain Cerebral cortex Ascending reticular activating system Diencephalon- thalamus, hypothalamus Brainstem Mesencephalon (midbrain) - III., IV. CN Metencephalon- pons, cerebellum, V. CN Myelencephalon- VI.-XII. CN

5 Brain

6 Spinal cord segments C1 - C5: cervical cord C6 - T2: intumescentia cervicalis T3 - L3: thoracic and lumbar cord L4 - S2: intumescentia lumbalis S3 - S5: sacral segments (rectum, anus, urinary bladder) Co1 - Co5: coccygeal segments

7 UMN x LMN UMN - cerebral cortex, basal nuclei, brainstem LMN - ventral horns, cranial nerves nuclei (III.-VII., IX.-XII.) UMN is superior to LMN (UMN inhibit LMN)

8 UMN x LMN Clinical Signs UMN LMN Motor function Paresis - paralysis, loss of voluntary movements Flaccid paralysis, loss of muscular power Reflexes N or (myotatic reflex) to Muscles Spastic, normal or elevated tone (mostly for extensors) Moderate and late muscular atrophy, mainly due to inactivity Loss of tone, no resistance to passive mobilisation Early and severe neurogen amyotrophy. Contracture and fibrous metaplasia occurs for longstanding lesions.

9 1. Step of examination History Clinical examination Basic laboratory examination NH 3, urea, creatinin, liver enzymes, Na +, glucose, muscle enzymes (CK, AST) Is there a neurological disease?

10 Neurological examination Behaviour, posture Head (cranial nerves) Neck, trunk, tail, anus Limbs Movement Record observation Repeat examination - re-evaluate the horse

11 Behavior and posture Mental status Change in behavior Yawning Abnormal posture (limbs crossing) Circling, head pressing Head tilt, head turn, opistotonus

12 Head pressing (encephalitis)

13 n. opticus Menace response (+ n. facialis) Pupillary light reflex (+ n. oculomotorius) Swinging light test (decussation of optic nerve fibres) N. opticus Chiasma opticum Tractus opticus Occipital cortex

14 Differential diagnosis of visual deficits Location of damage Blindness Ipsilateral Eye Contralateral Eye Direct pupillar reflex Indirect pupillar reflex Direct pupillar reflex Indirect pupillar reflex No lesion No present present present present Retina or N. II Ispsilateral (mydriasis) absent present present absent N III * No absent absent present present Cerebral hemispheres Contralateral or bilateral present present present present

15 n. oculomotorius Nucleus: mesencephalon (brainstem) Motor fibres Globe position (lateral strabismus) m. levator palpebrae ptosis of the eyelid Parasympathetic fibres - pupillary reflex

16 n. trochlearis - motor nerve (eye movement), dorsomedial strabismus n. abducens- eye globe retraction, motor nerve (eye movement), medial strabismus HN III., IV., VI. exit the skull together damage of all (combination)

17 n. trigeminus Nucleus - pons Motor nerve - masticatory muscles Sensitive nerve - face Perception of the nasal septum and ears Palpebral reflex (+ n. facialis)

18 n. facialis Nucleus medulla oblongata Motor innervations of the mimic muscles Symmetry and movement of the ears, eyelids, lips Ptosis of the ears, eyelids, lips Muscle tone of the lips (in the mouth corners) Decreased lacrimation (Schimmer test, corneal ulcers)

19 n. facialis

20 n. vestibulocochlearis Head position Eye globe position Normal vestibular nystagmus Vestibular system peripheral receptors, VIII. CN central vest. nuclei, vestibular tracts in the brainstem (spinal cord, cerebellum)

21 n. vestibulocochlearis Normal vestibular nystagmus Spontaneous nystagmus Rapid component jerk (direction opposite to lesion) x slow component Horizontal, vertical and rotatory nystagmus Direction x head position

22 n. vestibulocochlearis Horizontal nystagmus (video)

23 n. vestibulocochlearis Ventral strabismus Head tilt (x head turn) Asymmetrical ataxia (extensor tone) (Pendular nystagmus) - cerebellum

24 n. vestibulocochlearis Ventral strabismus Head tilt

25 n. glossopharyngeus, n. vagus - motor and sensitive innervations of the pharynx (swallowing), wall of the guttural pouch n. hypoglossus - motor innervations of the tongue, tongue symmetry and movement n. accessorius pharyngeal, laryngeal

26 Neck, trunk, tail, anus Cervico-facial reflex Panniculus reflex Tail tone Anal reflex

27 Neck, trunk, tail, anus Hypesthesia, anaesthesia, paresthesia, hyperesthesia Neck movement tuber coxae Symmetry (atrophy) Localized sweating - x sympathetic (Horner syndrome, spinal cord trauma, )

28 Horner syndrome- eyelid ptosis, miosis, enophtalmus, sweating

29 Sympathetic lesions Miosis Eyelids ptosis Enophtalmus Horner`s syndrom Third eyelids protrusion Sweating (head, neck to C2) Paravenious injection, neck trauma, guttural pouch mycosis,

30 Gait deficits Ataxia - incoordination Sensory Cerebellar - truncal ataxia Vestibular Dysmetria: hypermetria x hypometria Spasticity Paresis (paralysis) hoof dragging

31 Limbs and movement Walk, trot - straight line Conscious proprioreception (limb crossing) Tight circles - circumduction, pivoting Back Slope up and down

32 Limbs and movement Elevated head Blindfolding - vestibular ataxia Tight turns, abrupt stopping - conscious proprioreception

33 Limbs and movement Sway test (tail or halter pulling) - standing (LMN) x walking (UMN) Free in the paddock - gallop, turns Hopping test - weakness

34 Localisation of the spinal cord lesion C1 - C5: front and hind limbs, UMN C6 - T2: front limbs LMN, hind limbs UMN T3 - L3: hind limbs UMN L4 - S2: hind limbs LMN S3 - S5: urinary bladder LMN, tail, anus Co1 - Co5: without gait deficit

35 Ataxia - classification Gr. 0: normal gait Gr. 1: ataxia visible in aggravate condition (subtle ataxia) Gr. 2: ataxia visible in walk (mild ataxia) Gr. 3: trend to fall in aggravate condition (moderate ataxia) Gr. 4: falling down in walk (severe ataxia) Gr. 5: recumbent horse

36 CSF collection Atlanto-occipital site - GA Lumbosacral site standing horse Colour, total protein, TNCC, differential cell count.

37 Zoonoses!!! Rabies West Nile Virus encephalitis Borna disease (Hendra virus) So just be careful.

The Deconstructed Neurological Examination

The Deconstructed Neurological Examination Marguerite Knipe, DVM, Diplomate ACVIM (Neurology) I. MENTATION: Normal, Quiet, Obtunded (mild, moderate, severe), Stuporous, Comatose Define stuporous and comatose.