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The Brainstem & Cranial Nerves Relevant Exam Techniques

Rob MacKayAlec P. and Louise H. Courtelis Equine Teaching Hospital University of Florida

Anatomy

I

II III VI

V VII

VIII

IX X XII XI

Cerebrum Thalamus

Hypothalamus Midbrain Pons Medulla oblongata

Cerebellum IV

Midbrain Mesencephalon Midbrain

Pons Metencephalon

Hindbrain Cerebellum

Medulla Myelencepahlon

2

  Obtundation  Blindness/strabismus  Limb weakness  Atrophy, jaw weakness  Hypalgesia  Facial paralysis  Ataxia  Dysphagia  Tongue atrophy

  Blindness/strabismus  Alertness  Vision/eye control  Motor to limbs  Chewing  Facial sensation  Facial movement  Proprioception  Swallowing  Tongue movement

  Vision/eye control

Functions of the brainstem & cranial nerves

Function Cardinal Sign

  Limb weakness  Motor to limbs  Atrophy, jaw weakness  Chewing  Hypalgesia  Facial sensation  Facial paralysis  Facial movement  Ataxia  Proprioception  Dysphagia  Swallowing  Tongue atrophy  Tongue movement

Functions of the brainstem & cranial nerves

  Alertness  Vision/eye control  Motor to limbs  Chewing  Facial sensation  Facial movement  Proprioception  Swallowing  Tongue movement

  Obtundation  Blindness/strabismus  Limb weakness  Atrophy, jaw weakness  Hypalgesia  Facial paralysis  Ataxia  Dysphagia  Tongue atrophy

Function Cardinal Sign

  Obtundation  Alertness

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Obtundation: Reticular activating system

Reticular activating system I II

V VIII

Spinal cord somatosensory pathways

Severe!!

Reticular activating system I II

V VIII

Spinal cord somatosensory pathways

Less Less

Obtundation

Obtundation: Reticular activating system

Diffuse/major injury

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  Obtundation  Blindness/strabismus  Limb weakness  Atrophy, jaw weakness  Hypalgesia  Facial paralysis  Ataxia  Dysphagia  Tongue atrophy

  Blindness/strabismus  Alertness  Vision/eye control  Motor to limbs  Chewing  Facial sensation  Facial movement  Proprioception  Swallowing  Tongue movement

  Vision/eye control

Functions of the brainstem & cranial nerves

Function Cardinal Sign

Vision/Eye control  Pupillary light reflex  Traumatic optic nerve injury

  Eye position  Eye retraction  Sympathetic supply to the eye  Horner’s syndrome

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Vision - Pupillary light reflex

2-yo QH coltAsymmetric optic neuropathy

Optic nerve (II)

Oculomotor nerve (III)

Traumatic optic nerve injury

Martin et al. Equine vet J 1986;18:133-7

OD OS

M

C

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Eye position (VIII, III, IV, VI)  True strabismus

(III, IV, VI)

  Vestibular strabismus (VIII)

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Eye retraction (VI)

1-yo Paso Fino colt Tetanus

Sympathetic supply to the eye

9-yo TB geldingLower cervical trauma

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Horner’s syndrome

right left

  Obtundation  Blindness/strabismus  Limb weakness  Atrophy, jaw weakness  Hypalgesia  Facial paralysis  Ataxia  Dysphagia  Tongue atrophy

  Blindness/strabismus  Alertness  Vision/eye control  Motor to limbs  Chewing  Facial sensation  Facial movement  Proprioception  Swallowing  Tongue movement

  Vision/eye control

Functions of the brainstem & cranial nerves

Function Cardinal Sign

  Limb weakness  Motor to limbs

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Spinocerebellar tracts

I

V VII IX X XII XI

Limb weakness (UMN)

II III VI

VIII

IV

Upper motor neurons

Brainstem: Limb weakness/ataxia

22-yo Arabian stallion Extramedullary melanoma

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  Obtundation  Blindness/strabismus  Limb weakness  Atrophy, jaw weakness  Hypalgesia  Facial paralysis  Ataxia  Dysphagia  Tongue atrophy

  Blindness/strabismus  Alertness  Vision/eye control  Motor to limbs  Chewing  Facial sensation  Facial movement  Proprioception  Swallowing  Tongue movement

  Vision/eye control

Functions of the brainstem & cranial nerves

Function Cardinal Sign

  Limb weakness  Motor to limbs  Atrophy, jaw weakness  Chewing

I

V VII IX X XII XI

Mastication, facial sensation (V)

II III VI

VIII

IV

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Unilateral cranial nerve Vm

12-yo TB mareEquine protozoal myeloencephalitis

Cranial nerve Vm - trismus

9-yo QH geldingTetanus

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  Obtundation  Blindness/strabismus  Limb weakness  Atrophy, jaw weakness  Hypalgesia  Facial paralysis  Ataxia  Dysphagia  Tongue atrophy

  Blindness/strabismus  Alertness  Vision/eye control  Motor to limbs  Chewing  Facial sensation  Facial movement  Proprioception  Swallowing  Tongue movement

  Vision/eye control

Functions of the brainstem & cranial nerves - guideFunction Cardinal Sign

  Limb weakness  Motor to limbs  Atrophy, jaw weakness  Chewing  Hypalgesia  Facial sensation

I

V VII IX X XII XI

Mastication, facial sensation (V)

II III VI

VIII

IV

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Sensory Vs - Reflex & central

22-yo Arabian stallionExtramedullary melanoma

CN Vs Trigeminal

  Obtundation  Blindness/strabismus  Limb weakness  Atrophy, jaw weakness  Hypalgesia  Facial paralysis  Ataxia  Dysphagia  Tongue atrophy

  Blindness/strabismus  Alertness  Vision/eye control  Motor to limbs  Chewing  Facial sensation  Facial movement  Proprioception  Swallowing  Tongue movement

  Vision/eye control

Functions of the brainstem & cranial nerves

Function Cardinal Sign

  Limb weakness  Motor to limbs  Atrophy, jaw weakness  Chewing  Hypalgesia  Facial sensation  Facial paralysis  Facial movement

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13-yo Thoroughbred geldingTHO

8-yo pony mare Equine protozoal myeloencephalitis

3-yo mixed breed geldingFractured stylohyoid

Peripheral – outside skull

T2-enhanced Transverse

Central Peripheral –skull

Facial paralysisSign – Localization

Stupor – RAS or forebrain L facial paralysis – VII L R lean/head tilt – VIII L/R

L hindbrain Jaw to right – Vm L

  Obtundation  Blindness/strabismus  Limb weakness  Atrophy, jaw weakness  Hypalgesia  Facial paralysis  Ataxia  Dysphagia  Tongue atrophy

  Blindness/strabismus  Alertness  Vision/eye control  Motor to limbs  Chewing  Facial sensation  Facial movement  Proprioception  Swallowing  Tongue movement

  Vision/eye control

Functions of the brainstem & cranial nerves

Function Cardinal Sign

  Limb weakness  Motor to limbs  Atrophy, jaw weakness  Chewing  Hypalgesia  Facial sensation  Facial paralysis  Facial movement  Ataxia  Proprioception

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I

II III VI

V VII

VIII

IX X XII XI

Proprioception – 3 components

IV

Spinocerebellar tracts

Proprioception – 3 components  Spinal cord proprioceptive tracts  Transmits position and movement of muscles and joints

  Vestibular  Orientation relative to gravity

  Cerebellar  “The great regulator of movement”  Coordinates and smooths out UMN activity

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Proprioception Spinocerebellar tracts

22-yo Arabian stallion Extramedullary melanoma

Proprioception: Vestibular

18-yo Clydesdale geldingOtitis media/interna

8-yo pony mareEquine protozoal myeloencephalitis

PeripheralCentral

22-yo Arabian stallionExtramedullary melanoma

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True strabismus

2-yo mixed breed fillyEEE

Other signs of vestibular dysfunction

8-yo QH geldingTemporohyoid osteoarthropathy

Vestibular strabismus Spontaneous nystagmus Vestibular strabismus

Proprioception: Cerebellar

7-mo Arabian coltCerebellar abiotrophy

22-yo Arabian stallionExtramedullary melanoma

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  Obtundation  Blindness/strabismus  Limb weakness  Atrophy, jaw weakness  Hypalgesia  Facial paralysis  Ataxia  Dysphagia  Tongue atrophy

  Blindness/strabismus  Alertness  Vision/eye control  Motor to limbs  Chewing  Facial sensation  Facial movement  Proprioception  Swallowing  Tongue movement

  Vision/eye control

Functions of the brainstem & cranial nerves - guideFunction Cardinal Sign

  Limb weakness  Motor to limbs  Atrophy, jaw weakness  Chewing  Hypalgesia  Facial sensation  Facial paralysis  Facial movement  Ataxia  Proprioception  Dysphagia  Swallowing

17-yo QH mareLeft guttural pouch mycosis

Dysphagia: CNs X, IX, XI

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Guttural pouch mycosis

17-yo QH mareLeft guttural pouch mycosis

Location: L. XII hypoglossal

L. X vagus, IX,XI

L. Sympathetic, CCG

stylohyoid ICA

ECA

XII

IX

Guttural pouch anatomy

Right guttural pouch Medial compartmentRight guttural pouch

Rectus capitis ventralis

Not shown: XI, CCG

X

20

Left

ICA

IX/XII

Guttural pouch mycosis

Right

Guttural pouch fibrosis

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  Obtundation  Blindness/strabismus  Limb weakness  Atrophy, jaw weakness  Hypalgesia  Facial paralysis  Ataxia  Dysphagia  Tongue atrophy

  Blindness/strabismus  Alertness  Vision/eye control  Motor to limbs  Chewing  Facial sensation  Facial movement  Proprioception  Swallowing  Tongue movement

  Vision/eye control

Functions of the brainstem & cranial nerves - guideFunction Cardinal Sign

  Limb weakness  Motor to limbs  Atrophy, jaw weakness  Chewing  Hypalgesia  Facial sensation  Facial paralysis  Facial movement  Ataxia  Proprioception  Dysphagia  Swallowing  Tongue atrophy  Tongue movement

Tongue weakness (XII)

3-yo QH geldingWest Nile encephalitis

13-yo Quarter horse mareGuttural pouch mycosis

Central - LMN Peripheral

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Tongue weakness

3-mo TB fillyJuvenile epilepsy

1-yo TB fillyBotulism

UMN Neuromuscular

THE END