05 vestibular system and cranial nerves of dogs and cats

Describe the anatomic component of the vestibular system • Recognize typical clinical signs of vestibular disease • Differentiate between central versus peripheral vestibular disease • Recognize paradoxical and bilateral vestibular disease • Discuss causes of peripheral vestibular disease in dogs and cats: – Describe clinical features of Canine Idiopathic Geriatric Vestibular disease • Discuss causes of central vestibular disease in dogs and cats • Recognize and describe clinical signs of diseases affecting the cranial nerves • Discuss causes of cranial nerves disease in dogs and cats – Describe clinical features of Idiopathic Trigeminal Neuritis and Idiopathic Facial Nerve Paralysis

Vestibular System • Responsible for

maintaining balance regulating the position of eyes, trunk and limbs in relation to changes in position of the head

Maintaining balance depends on

Vestibular receptors (main contributor)

Vision

Proprioceptive receptors in joints and tendons

Anatomy of Vestibular System: Peripheral Vestibular System

• receptor located at

• nerve innervation

• utricle and saccule, and semicircular canals

• Vestibular nerve (CN VIII)

Anatomy of Vestibular System: Central Vestibular System

• 2 main part

• name 1 for brainstem and 1 fro cerebellum

Vestibular nuclei – Brainstem

Cerebellum

• Caudal cerebellar peduncle • Fastigial nucleus • Flocculonodular lobe

Clinical Signs of Vestibular Disease

add later exhaus list

Head tilt

Nystagmus

Vestibular ataxia (“off balance”

Vomiting and nausea

Ventral or ventrolateral positional (not static) strabismus

head tilt

Nystagmus:

• define nustagus side depend on ____ phase.

• fast face is ____ to leision

involuntary rhythmic oscillation of the eyes (jerk eye movement with slow and fast phase)

• Physiologic nystagmus (vestibulo-ocular)

• Pathological (spontaneous or positional):

  • Horizontal or Rotatory

  • Vertical indicated central disaese (RARE)

  • ast phase CONTRALATERAL to the lesion

Vestibular ataxia:

Falling – Rolling – Drifting – Tight circles toward the side of the lesion (cats)

Decreased extensor tone ipsilateral limbs, increased extensor tone contralateral limbs

Vomiting and nausea

Acute vestibular disease – Projections to the emetic center within medullary reticular formation

Ventral or ventrolateral strabismus

eye stays in position when lift head

Differentiation of Peripheral versus Central Vestibular Diseas

the following indicate central diseae=se

1. Hemiparesis and postural reaction deficits IPSILATERAL to the lesion

2. Vertical nystagmus (rare)

3. Nystagmus changing direction with changes in head position

4. Cranial nerve deficits (other than CN VII and sympathetic innervation to the eye)

5. Cerebellar signs

6. Decreased level of consciousness

7. Paradoxical vestibular syndrome

Hemiparesis and conscious proprioceptive deficits in vestibular disease

• Ipsilateral to the lesion

central leision

Clinical Signs of Vestibular Disease: Cranial nerve deficits

Deficits of other cranial nerves besides CN VII and Horner = central lesion

Horner syndrome— sym[athetic innervationof eye causes 4

Ptosis

Enophtalmus

Miosis

3rd eyelid protrusion

Paradoxical vestibular syndrome (rare)

contradictory vestibular sign contralateral to leision at cerebelum

Caused by loss of cerebellar inhibition of the vestibular output

pug L side head tilt actually have an infart leision at R cerebellum. right postural reaction deficit.

Bilateral Vestibular Disease

Absent physiologic and/or pathologic nystagmus

Absent head tilt

Side-to-side swaying of the head

Broad-base stance

Falling to either side

Diagnostic Procedures for Vestibular Disease

Physical, neurological, otoscopic examination (could may well be otitis externa/media!)

• Hematology and biochemistry

Skull radiographs

CT scan or MR

what wlse could u do?for Vestibular Disease dx procedure

Ear cytology • Ear culture and sensitivity • Myringotomy • CSF analysis • Infectious diseases titers on serum and/or CSF • Biopsy/histopathology

Differential diagnoses

Vascular • Infectious/Inflammatory • Traumatic • Toxic • Anomaly • Metabolic • Idiopathic • Iatrogenic • Neoplastic • Nutritional • Degenerative

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Anomalous ddx

– Bilateral congenital vestibular disease: • Akitas • Beagles

Congenital peripheral vestibular disease: • German Shepherds • Doberman pinchers • English cocker spaniel • Siamese cat • Burmese cat

Metabolic: ddx Hypothyroidism (dog)

Associated with various neurological signs from seizures to mega esophagus, laryngeal and facial nerve paralysis – Mucinous deposits in and around facial and vestibular nerve may cause compression of the axons as they pass through the internal acoustic meatus of the temporal bone

Neoplastic ddx

Squamous cell carcinoma (cat) – Ceruminous gland adenoma (dog) and adenocarcinoma (cat) – Papillary adenoma (dog) – Others: lymphosarcoma, osteosarcoma, chondrosarcoma, fibrosarcoma.

Iatrogenic: ddx

chlorhexidine, aminoglycosides – Streptomycin and gentamycin vestibular receptors – Neomycin, kanamycin and amikacin  auditory receptors

ototoxicity to ruptured eadrum; irreversible

Infectious ddx • Otitis media-interna

Otoscopic examination is required for dogs or cats presented with peripheral vestibular disease

clinical history of previously diagnosed otitis externa

Medical treatment (ear flush and/or myringotomy) or surgical

another infetious in cat

• Inflammatory polyps (cats)

infectious ddx: Idiopathic vestibular disease:

both cat and dog

• Peracute onset and improving progression (in cats a deterioration can be seen) • Usually, older patients • Peripheral vestibular disease – Vomiting, nausea, and severe vestibular deficits • Spontaneous improvement in 2-3 days • Normal in 7-10 days - in some cases up to 2-3 weeks and sometimes there is a residual deficits (head tilt or mild ataxia) • Recurrence is possible • No specific treatment –anti-emetic (maropitant) and anti-nausea (ondansetron) medication

CENTRAL PREV IS PERI

Degenerative: centtral vestibular ddx

Lysosomal storage diseases

Anomalous ddx Central Vestibular Disease

Arachnoid cyst – Cerebellar cyst – Hydrocephalus

Nutritional: ddx central

Thiamine deficiency – Bilateral symmetrical central vestibular signs

esp cat w fish

dog wtih cooked meat? (dc)

neoplastic: central ddx

Thiamine deficiency – Bilateral symmetrical central vestibular signs

Central Vestibular Infectious Diseases

main cat: FIP, leisteria in ruminant

Central Vestibular Inflammatory Diseases most common

Granulomatous Meningoencephalomyelitis (GME)

Granulomatous Meningoencephalomyelitis (GME)

Subacute to chronic sterile inflammation, suspected immunemediated disorder • Middle age small breed dogs • Disseminated, focal and ocular (optic neuritis) form • Prognosis guarded to poor • Definitive diagnosis: histopathology • Traditional treatment: immunosuppressive doses of corticosteroids • Prolonged survival time with other immunosuppressive agents in addition to prednisolone such as cytarabine, cyclosporine, lomustine, procarbazine

toxic ddx: Central Vestibular Disease

– Metronidazole intoxication

• Characterized by anorexia, vestibular ataxia and vertical nystagmus • Recovery may be enhanced by administration of diazepam at 0.4 mg/kg TID for 3 days. • Diazepam competitively displacing metronidazole from GABA receptors

Lead poisoning

Central Vestibular Disease what other ddx

Traumatic • Vascular

Diseases of the cranial nerves of dogs and cats: Cranial Nerve I - Olfactory

rare to be singular injury

Loss of appetite, anosmia – difficult to assess • Nasal discharge, nasal obstruction

DD: – Viral, bacterial or fungal rhinitis – Nasal adenocarcinoma, meningioma, neuroblastoma

Diseases of the cranial nerves of dogs and cats Cranial nerve II - Optic

optic nerve is an extension of the CNS— any dx affecting CNS will effect ON

Neuroepithelial cells (rods & cones), bipolar and ganglion cells 2. Optic nerve 3. Optic chiasm 4. Optic tract

—>Lesion: blindness and pupillary light reflex (PLR) deficit

5 Lateral geniculate nucleus 6. Optic radiation 7. Occipital lobe

—>Lesion: central blindness

7a. Pretectal nuclei 8. Edinger-Westphal nucleus 9. CN III – Oculomotor nerve 10. Ciliary ganglion 11. Ciliary nerves 12. Sphincter pupillae muscle

• Lesion: mydriasis, lack of response to light stimulus

Blindness and PLRs Step by step evaluation

Menace response  CN II, complete visual pathway to occipital cortex, and CN VII 2. Blinking reflex  CN V and VII 3. Obstacle course/cotton ball test  CN II 4. PLR (direct and consensual)  CN II, complete PLR pathway to CN III and sympathetic innervation 5. Ophthalmoscopic exam  Retina and CN II

pre chiasmatic (ON, eye itself) (peripheral); post chiasmatic(

Blindness and PLRs Diagnostic procedures

Physical, neurological and ophthalmological examination • Hematology, biochemistry, blood pressure measurements • ERG – electroretinogram (tretinal activity) • Ultrasonography • MRI or CT head • CSF analysis • Infectious disease titers on serum and/or CSF

Blindness without PLRs Differential diagnoses

• Degenerative: SARD (sudden aquired retinal degeneration

• Anomalous: bilateral hypoplasia of the optic nerve in dog, cat, horse

• Neoplastic: pituitary macroadenoma, meningioma, lymphoma

• Nutritional: vitamin A deficiency in young growing cattle with stenosis of optic canals

• Infectious/inflammatory: optic neuritis with GME, CDV, Toxoplasmosis, Cryptococcosis, Blastomycosis, bacterial infections, FIP

• Traumatic: craniofacial trauma

• Toxic: fluoroquinolone (cats)

• Vascular: feline ischemic encephalopathy (optic tracts)

Blindness with intact PLRs Differential diagnoses (more central)

Degenerative: storage diseases • Anomalous: obstructive hydrocephalus, hydranencephaly in ruminants • Neoplastic: primary and metastatic tumors • Nutritional: polioencephalomalacia in cattle and sheep secondary to thiamine deficiency • Infectious/inflammatory: CDV, Neospora, Toxoplasma • Toxic: lead poisoning • Traumatic: head trauma • Vascular: cerebral ischemia following prolonged seizures, anesthetic accident

Anisocoria mechanism

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Lack of sympathetic or parasympathetic

Horner syndrome – Miosis – Ptosis – Enophthalmus – Protrusion third eyelid

parasymth: Mydriasis – ± Ptosis – ± Ventrolateral strabismus

Diseases of the cranial nerves of dogs and cats: Cranial nerve III – Oculomotor

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Diseases of the cranial nerves of dogs and cats: Cranial nerve IV - Trochlear

Motor - Innervates the dorsal oblique extraocular muscle • CN IV deficit: lateral rotation of the eye • Ophthalmoscopic exam for animals with round pupil will reveal tilting of the dorsal retinal vein

Diseases of the cranial nerves of dogs and cats: Cranial nerve VI - Abducent

Motor - Innervates the lateral rectus extraocular muscle and the retractor bulbi muscle • CN VI deficit: – Medial strabismus – Inability to retract the globe • Corneal reflex – Ophthalmic branch CN V – CN VI and VII

Cranial nerves III, IV and VI

Diseases affecting motor components causes an absence of eye movements - external ophtalmoplegia • Diseases affecting the parasympathetic innervation of the pupil - internal ophtalmoplegia (mydriasis and ptosis) • Idiopathic oculomotor neuropathy – Good prognosis – improvement with no treatment

Diseases of the cranial nerves of dogs and cats

except mandibular branch has motor of mastication fucn

Mandibular branch: – Motor - muscles of mastication – Sensory - lower jaw • Ophthalmic branch: – Sensory - dorsal eyelid and cornea • Maxillary branch: – Sensory - ventral eyelid and nasal area.

Diseases of Cranial nerve V - Assessment

Palpebral reflex • Corneal reflex • Pinch upper lip and chin • Nasal stimulation • Open jaw • Observe/palpate skull to detect atrophy of masticatory muscles (MM)

Diseases of Cranial nerve V - Trigeminal

Bilateral lesion mandibular branch – Dropped jaw – Symmetric atrophy masticatory muscles – +/- decreased sensation chin • Unilateral lesion mandibular branch – Asymmetry masticatory muscles (atrophy) – +/- decreased sensation chin • Ophthalmic and maxillary branch – Ipsilateral sensory deficits

Cranial nerve V – Trigeminal ddx: Inflammatory/infectious Bilateral lesion of mandibular branch:

– Lymphoma • More common in cats • Guarded prognosis

– Idiopathic trigeminal neuritis • Acute bilateral paralysis of the masticatory muscles • Dogs and cats • Dropped jaw, drooling saliva, difficulty prehending food and drinking • Horner syndrome sometimes • Treatment - supportive care • Prognosis: Good, resolution within in 2-3 weeks

Cranial nerve V – Trigeminal Tumours ddx

Unilateral lesion of mandibular branch: – Trigeminal nerve sheath tumor • With or without sensory deficits • Unilateral muscle atrophy • Poor prognosis

Cranial nerve VII - Facial function

Motor – muscles facial expression – Sensory – inner surface pinna – Taste sensation rostral two thirds tongue – Parasympathetic function to lacrimal gland, nasal glands, mandibular and sublingual salivary glands

disease of Cranial nerve VII - Facial clnical sign

Facial asymmetry – Absent movements ear, eyelids, upper lip nostrils – Drooling saliva – Neurogenic keratoconjutivitis sicca (KCS) (cannot blink +lacrimal system deficit)

disease of Cranial nerve VII - Facial ddx

Otitis media-interna • Idiopathic facial nerve paralysis • Hypothyroidism • Polyneuropathy • Neoplasms of CN VII or medulla

disae of CN7 ddx: Idiopathic

Idiopathic facial nerve paralysis

Commonly unilateral, but can affect both sides • Unknown pathogenesis (possibly like “Bell’s palsy” in humans) • Middle age to older dogs • Cocker Spaniels are predisposed • Diagnosed excluding other causes of facial neuropathy • Prognosis for recovery of function is guarded • Symptomatic treatment (i.e. artificial tears to protect cornea)

desease of Cranial Nerve VIII Vestibulocochlear clincial sign and diag tests

Deafness • Otoscopic examination • BAER test

desease of Cranial Nerve VIII Vestibulocochlear ddx

Degeneration auditory receptors/ossicles

Congenital deafness

Otitis media-interna

Ototoxic compounds

Trauma

Cranial Nerve IX Glossopharyngeal function

Motor - muscles of pharynx

Sensory - pharyngeal mucosa and caudal third of tongue

Parasympathetic function – zygomatic and parotid salivary glands.

Gag and swallowing reflex

—> Dysphagia + vestibular sign indicated CN 9 leision

Cranial Nerve X - Vagus function

• Motor – muscles pharynx, larynx (recurrent laryngeal nerve) and palate

Motor parasympathetic – viscera in chest and cranial abdomen

Sensory – pharynx, larynx and viscera

diseae of Cranial Nerve X - Vagus clinical sign

Differential diagnoses for CN IX and X deficits

Degenerative: storage diseases. – Anomalous: congenital hereditary laryngeal paralysis in Bouvier des Flanders and Siberian Huskies. No treatment. – Metabolic: hypothyroidism (dog) – Neoplastic: brainstem tumors, paraneoplastic polyneuropathies. – Idiopathic: idiopathic laryngeal described in middleaged to older male large breed dogs = geriatric onset laryngeal paralysis polyneuropathy – Toxic: lead and organophosphate toxicity – Traumatic: post-surgical complication

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functionCranial nerve XI - Accessory

Motor – neck muscles (trapezius, sternocephalicus and brachiocephalicus) • Atrophy of neck muscles on palpation • Differential diagnoses - trauma

function of Cranial nerve XII – Hypoglossal

Motor – intrinsic and extrinsic muscles of the tongue

Deficits in tongue movements, atrophy, and deviation of the tongue (assymmetry)