Neurological examination of the

horse

Aim of the neurological

examination

• Is there a neurological disease ?

• Anatomical location of the problem ?

• Diagnosis?

• Are there therapeutic options ?

• What is the prognosis ?

Nerve system anatomy

• CNS - brain, spinal cord

• PNS - peripheral nerves (motor,

sensitive)

• Autonomic nervous system -

sympathetic, parasympathetic

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

Brain

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

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)

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)

Loss of tone, no resistance to passive

mobilisation

Moderate and late muscular

atrophy, mainly due to inactivity

Early and severe neurogen

amyotrophy. Contracture and fibrous

metaplasia occurs for longstanding

lesions.

1. Step of examination

• History

• Clinical examination

• Basic laboratory examination – NH3, urea,

creatinin, liver enzymes, Na+, glucose,

muscle enzymes (CK, AST)

Is there a neurological disease ?

Neurological examination

• Behaviour, posture

• Head (cranial nerves)

• Neck, trunk, tail, anus

• Limbs

• Movement

• Record observation

• Repeat examination - re-evaluate the horse

Behavior and posture

• Mental status

• Change in behavior

• Yawning

• Abnormal posture (limbs crossing)

• Circling, head pressing

• Head tilt, head turn, opistotonus

Head pressing (encephalitis)

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

Differential diagnosis of visual

deficitsLocation of

damageBlindness 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

hemispheresContralateral or

bilateral

present present present present

n. oculomotorius

• Nucleus: mesencephalon (brainstem)

• Motor fibres

Globe position (lateral strabismus)

m. levator palpebrae – ptosis of the eyelid

• Parasympathetic fibres - pupillary reflex

• 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)

n. trigeminus

• Nucleus - pons

• Motor nerve - masticatory muscles

• Sensitive nerve - face

• Perception of the nasal septum and ears

• Palpebral reflex (+ n. facialis)

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)

n. facialis

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)

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

n. vestibulocochlearis

• Horizontal nystagmus (video)

n. vestibulocochlearis

• Ventral strabismus

• Head tilt (x head turn)

• Asymmetrical ataxia (extensor tone)

• (Pendular nystagmus) - cerebellum

n. vestibulocochlearis

• Ventral strabismus • Head tilt

• 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

muscles, cervical muscles

Neck, trunk, tail, anus

• Cervico-facial reflex

• Panniculus reflex

• Tail tone

• Anal reflex

Neck, trunk, tail, anus

• Hypesthesia, anaesthesia, paresthesia,

hyperesthesia

• Neck movement – tuber coxae

• Symmetry (atrophy)

• Localized sweating - x sympathetic (Horner

syndrome, spinal cord trauma, …)

Horner syndrome- eyelid ptosis,

miosis, enophtalmus, sweating

Horner`s syndrom

• Sympathetic lesions

– Miosis

– Eyelids ptosis

– Enophtalmus

– Third eyelids protrusion

– Sweating (head, neck to C2)

• Paravenious injection, neck trauma, guttural

pouch mycosis,…

Gait deficits

• Ataxia - incoordination

Sensory

Cerebellar - truncal ataxia

Vestibular

• Dysmetria: hypermetria x hypometria

• Spasticity

• Paresis (paralysis) – hoof dragging

Limbs and movement

• Walk, trot - straight line

• Conscious proprioreception (limb crossing)

• Tight circles - circumduction, pivoting

• Back

• Slope – up and down

Limbs and movement

• Elevated head

• Blindfolding - vestibular ataxia

• Tight turns, abrupt stopping - conscious

proprioreception

Limbs and movement

• Sway test (tail or halter pulling) - standing

(LMN) x walking (UMN)

• Free in the paddock - gallop, turns

• Hopping test - weakness

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

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

CSF collection

• Atlanto-occipital site - GA

• Lumbosacral site – standing horse

• Colour, total protein, TNCC, differential

cell count….

Zoonoses!!!

• Rabies

• West Nile Virus encephalitis

• Borna disease

• (Hendra virus)

So just be careful.