Vestibular and cerebellum Flashcards
Development of the ear structures?
Inner ear: receptors for the auditory and vestibular system are derived from ectoderm but are contained in a mesodermally derived structure (from the otic placode > otic pit > otic vesicle adjacant to the rhombencephalon.
The membranous and bony labyrinths are formed adjacent to the first and second branchial arches and their corresponding first pharyngeal pouch and first branchial groove. The first branchial groove gives rise to the external ear canal. The first pharyngeal pouch forms the auditory tube and the mucosa of the middle ear cavity. The intervening tissue forms the tympanum. The ear ossicles are derived from the neural crest of branchial arches 1 (malleus and incus) and 2 (stapes). These ossicles become components of the middle ear associated laterally with the tympanum (malleus) and medially with the vestibular window of the bony labyrinth of the inner ear (stapes).
What are perilymph and endolymph derived from?
Perilymph -> CSF
Endolymph -> blood vessels along the wall of the cochlear duct.
Name the 3 semicircular canals
- anterior (vertical),
- posterior (vertical),
- lateral (horizontal).
Each semicircular duct is oriented at right angles to the others.
Layers of the cochlea?
1) Scala vestibuli in outer bony labyrinth
(perilymph, oval window)
2) Scala media/cochlear duct (enodlymph) in inner membranous labyrinth (hair cells and spiral organ of Corti)
3) Scala tympani (perilymph, round window) in the outer bony labyrinth
What is the end of the cochlear duct called?
Helicotrema!
Scala tympani and scala vestibuli perilymph meet and mix
Which structures are located within the vesibule of the inner ear?
Vestibule (contains perilymph, is in the outer bony labyrinth)
1) Utricle
2) Saccule
both contain endolymph and are in the inner membranous labyrinth, both contain hair cells, both have maculae (static equilibrium)
Where are the cristae ampularis located?
Ampullae of the semicircular canals
The cristae ampularis are important for dynamic equilibrium.
Anatomy of the crista ampularis (dynamic equilibrium)
Amuplla - dilation in each membranous semicircular canal
Crista - proliferation of connective tissue on one side of the membranous ampula
Cupula - gelatinous structure on the surface of the crista (protein-polysaccharide material)
Hair cells (connected to the dendritic zones of the neurons of the vestibular portion of the vestibulocochlear nerve) have
1) stereocillia (40-80 hairs)
2) kinocilium (only 1)
which project into the cupula
What happens to the activity of the vestibular neurons with movement, for example, when you move the head to the right?
The vestibular neurons are tonically active, and their activity is excited or inhibited by deflection of the cupula in different directions. Each semicircular duct on one side is paired with a semicircular duct on the opposite side by their common position in a parallel plane. These synergistic pairs are the left and right lateral ducts, the left anterior and right posterior ducts, and the left posterior and right anterior ducts. When movement in the direction of one of these three planes stimulates the vestibular neurons of the crista of one duct, they are inhibited in the opposite duct of the synergistic pair. For example, rotation of the head to the right causes the endolymph to flow in the right lateral duct such that the cupula is deflected toward the utriculus and the cupula of the left lateral duct is deflected away from the utriculus. This action causes increased activity of vestibular neurons on the right side and decreased activity on the left side, resulting in a jerk nystagmus to the right side, which is an involuntary rhythmic oscillation of the eyes.
What are maculae?
Structures found in the saccule and utriculus, important in static equilibrium.
The surface has columnar neuroepithelial cells (hair cells) covered by a gelatinous material - statoconiorum (otolithic) membrane which contains calcareous crystalline bodies known as statoconia (otoliths).
The hair cells also have 1) stereocilia and 2) kinocilia.
The hair cells are synapsing with the dendritic zones of the vestibular neurons of CN VIII.
The macula in the saccule is oriented vertically (sagittal plane), whereas the macula of the utriculus is oriented horizontally (dorsal plane).
Name the vestibular nuclei
Rostral
medial
lateral
caudal
Located on either side of the dorsal part of the pons and medulla adjacent to the lateral wall of the fourth ventricle
Which tracts exit the vestibular nuclei?
1) Lateral vestibulospinal tract - arises from the cell bodies of the lateral vest. nucleus -> ipsilateral ventral funiculus to interneurons of the ventral grey columns of entire spinal cord > + to ipsilateral extensor muscles (- to ispilateral flexor and - to contralateral extensor muscles)
2) Medial vestibulospinal tract- arises from the cell bodies of the rostral, medial and caudal vest. nuclei > ipsilateral ventral funiculus of cervical and cranial thoracic SC!!! > interneurons of ventral grey column > innervation of neck muscles
3) Axons coursing in the medial longitudinal faciculus (MLF) to terminate in motor nuclei of CN III, IV, VI
4) Axons to reticular formation (vomiting center)
5) Axons to contralateral medial geniculate nucleus of the thalamus (synapse) > internal capsule > corona radiata > temporal cortex
6) Axons to cerebellum thru caudal cerebellar peduncle > cortex of flocconodular lobe and fastigial nucleus
Which time of year does idiopathic bening vestibular disease occur most commonly in cats?
Summer (still unknown why)
Afferent and efferent arm of the physiologic nystagmus?
- Afferent: CN VIII
- Medial longitudinal fasciculus
- Efferent: CN VI (abducens) for the lat. Rectus muscle (abduction of eye) and CN III (oculomotorius) for the med. Rectus muscle (adduction of eye)
Why do some dogs have rythmic movements of the eyelids along with the pathologic nystagmus?
A simultaneous eyelid movement may be seen concomitant with the nystagmus that presumably is a reflex action. We presume that this occurs because of a direct pathway from the vestibular nuclei to the facial nuclei. The movement of the superior eyelid is likely through the action of the levator anguli oculi medialis muscle.
Why do some dogs have rythmic movements of the eyelids along with the pathologic nystagmus?
A simultaneous eyelid movement may be seen concomitant with the nystagmus that presumably is a reflex action. We presume that this occurs because of a direct pathway from the vestibular nuclei to the facial nuclei. The movement of the superior eyelid is likely through the action of the levator anguli oculi medialis muscle.
Neuro signs in bilateral vestibular disease? (Peripheral)
1) crouched posture closer to the ground surface
2) may often walk well but are often slow and cautious to avoid falling, especially when they move their heads suddenly
3) wide head excursions
4) loss of physiologic or pathologic nystagmus
5) head rebound phenomenon (If the head and neck are extended in these patients and the support is suddenly withdrawn, the head may rapidly descend ventrally beyond the normal neutral position) -> DD cerebellar disease
How long does the recovery in cats with idiopathic bening vestibular disease last?
Usually slower than in dogs,
7-10 days for ataxia,
2-4 weeks for head tilt (may persist)
Name some breeds of dogs and cats with congential peripheral vestibular disease
German shepherd dog, doberman pinscher, Akita, beagle, English cocker spaniel
Burmese and Siamese cats.
Typical clinical picture of thiamin deficiency in small animals?
Short phase of vestibular ataxia followed by:
mydriasis
seizures
(common in cats that eat a fish diet, as it contains thianimase)
MRI signs of thiamin deficiency encephalopathy?
bilateral symmetric lesions in the:
1) vestibular nuclei,
2) caudal colliculi,
3) nuclei of the oculomotor nerve,
4) lateral geniculate nuclei (cat)
5) red nuclei
Which disease entity commonly follows otitis media/interna in horses (commonly concurent with ispilateral CN VII deficits)?
temporohyoid osteopathy + temporal bone fracture
Which infectious agent in horses is commonly associated with central vestibular disease?
Sarcocystis neurona
(rabies and EEV usualy also have prosencephalic signs, EHV-1 and WNV usually doesnt affect the central vestibular system)
The most common caudal brainstem disorder of adult cattle?
Listeriosis
(ddx: rabies, abscess, suppurative meningitis, thrombotic meningoencephalitis)
How old are most cattle that develop listeriosis?
> 1 year of age
Typical neurological clinical signs of listeriosis in cattle?
“Circling disease”
Rhombencephalitis
-obtundation,
-facial paralysis,
-tongue paresis,
-dysphagia,
-jaw paresis,
-dysfunction of the central components of the vestibular system,
-UMN and GP system dysfunction,
-loss of their normal sensorium,
-circling
Route of entry of Listeria monocytogenes in cattle?
through abrasions and lacerations of the oral mucosa and gains access to the dendritic zones of GSA of CN V.
The bacterium travels retrograde over these axons through the trigeminal ganglion and into the pons, where the fifth cranial nerve attaches to the brainstem.
Inflammation occurs in these trigeminal nerve branches and in the caudal brainstem.
Prognosis in listeriosis?
Rigorous treatment with penicillin will usually improve or resolve the clinical signs in cattle that are still standing.
The prognosis is less favorable in small ruminants.
Recumbent animals have a poor prognosis regardless of the species.
Which agent causes thrombotic meningoencephalitis of cattle?
bacterium Histophilus somni (Hemophilus somnus)
DDx for a goat with central vestibular signs?
- Listeriosis,
- caprine arthritis encephalitis (CAE),
- viral encephalitis,
- Parelaphostrongylus tenuis myiasis,
- abscess,
- neoplasm
Which pathology is associated with congenital pendular nystagmus of belgian shepherd dogs?
agenesis of optic chiasm - the optic fibers continued into the ipsilateral optic tract uninterrupted and with no deccusation.
Which pathology is associated with congenital pendular nystagmus in cats?
1) ocular albinism,
2) an abnormality in the retinogeniculate projections and the neuronal organization of the lateral geniculate nucleus has been observed in the Siamese cat and the white Persian tiger.
3) more retinal ganglion neurons project their axons contralaterally in Siamese cats than the normally pigmented feline breeds. No obvious impairment of vision is noted. Many of these cats also have a mild strabismus.
4) in some cats and cattle with the Chédiak-Higashi syndrome, in which pigmentation and melanin granules are abnormal.
We have also studied a 13-week-old mixed-breed dog with bilateral retinal dysplasia that had pendular nystagmus without visible structural abnormalities of the brain on MRI.
De Lahunta
Which structure does the cerebellum develop from?
the alar plate of the metencephalon - rhombic lip
Its first appearance is a dorsal bulge of the alar plate, which extends the alar plate tissue dorsally and medially in the roof plate, where the growths from each side eventually join each other. The first growth of each alar plate is called the rhombic lip, which arises from the side of the rhomboid fossa of the fourth ventricle. This rhombic lip consists of proliferating cells from the germinal layer adjacent to the fourth ventricle.
Name the main parts of the cerebellum
1) body (vermis and 2 hemispheres)
2) small floconodular lobe (vestibular cerebellum)
Name the cerebellar peduncles and which fibers pass thru them?
1) Rostral peduncle - cerebellum to mesencephalon (mostly efferents)
2) Middle peduncle - transverse fibers of the pons with cerebellum (afferents from pons)
3) Caudal peduncle - medulla and SC to cerebellum (mostly afferents)
from lateral to medial: Middle Caudal Rostral (MCR)
Name the cerebellar nuclei
From lateral to medial:
L(D)IF
Lateral (dentate)
Interposital
Fastigial
Two mayor types of afferents fibers to the cerebellum based on the morphology of their telodendrons?
1) mossy fibers
2) climbing fibers
1) more abundant, origin in the brainstem and SC, synapse on neurons of the cerebllar nuclei and granule cells, Golgi cells, and basket cells
2) axons of the olivary neurons (enter thru the caudal peduncle) and synapse on the neurons of the cerebellar nuclei and Purkinje cells
Are the mossy and climbin fibers facilitatory or inhibitory at their synapse and which neurotransmitter is released?
facilitatory at their synapse with neurons of the cerebellar nuclei and the granule cell and Purkinje neurons, respectively.
Acetylcholine - mossy fibers
Aspartate - climbing fibers
Name the types of neurons in the cerebellar cortex and their role
Molecular layer:
1) stellate neurons (outer)
2) basket neurons
both inhibitory to the Purkinje neurons
Purkinje neurons - efferents, either to the cerebellar or vestibular nuclei
Granule cell layer
1) granular neurons - facilitatory to the Purkinje neurons - glutamate
2) large stellate neurons (Golgi) - inhibitory to granule cell neurons
Efferent axons from the cerebellar cortex?
Only from the Purkinje cells!!!
1) majority terminate on the cerebellar nuclei neurons
2) small proportion from the floconodular lobe exit thru the caudal peduncle and synapse on the vestibular nuclei
always GABA as neurotransmitter at telodendria
Cerebellar afferents?
1) General proprioception (GP) - spinocerebellar tracts thru caudal peduncle
2) Special proprioception (SP) - vestibulocerebellar axons from the CN VIII or from vestibular nuclei thru caudal peduncle
3) Special somatic afferent (SSA) - vision and auditory - tectocerebellar axons thru rostral peduncle and pontine fibers thru middle peduncle
4) UMN - red, pontine and olivary nuclei and the reticular formation
- rubrocerebellar axons thru rostral peduncle
- reticulocerebellar axons thru caudal peduncle
- extrapyramidal system thru olivary nucleus - climbing fibers
- pontine nucleus - relay for projection axons from cerebral cortex to cerebellum (cerebropontocerebellar parhway)
Cerebellar efferents?
1) Cerebellar cortex - Purkinje neurons from floconodular lobe thru caudal peduncle to vestibular nuclei
2) Cerebellar nuclei
- Fastigial nucleus - to vestibular nuclei and reticular formation thru caudal cerebellar peduncle
- Interposital nucleus - to red nucleus and reticular formation thru rostral peduncle
- Lateral (dentate) nucleus to red nucleus, reticular formation, pallidum and ventral lateral nucleus of the thalamus thru rostral peduncle
Schema of the cerebro-cerebellar circuit
The motor cortex of the frontoparietal lobe > corona radiata > centrum semiovale > internal capsule > crus cerebri > longitudinal fibers of the pons > pontine nucleus cross in the transverse fibers of the pons > middle cerebellar peduncle > cerebellar medulla > folial white lamina > granular layer neurons > Purkinje neurons > folial white lamina > cerebellar medulla > lateral cerebellar nucleus > rostral cerebellar peduncle > cross in ventral tegmental decussation > ventral lateral nucleus of thalamus> thalamocortical fibers> internal capsule> centrum semiovale> corona radiata, > motor cortex of frontoparietal lobe
Phylogenetic division of the cerebellum?
1) Archicerebellum - flocconodular lobe (vestibular activity)
2) Paleocerebellum - vermis of the rostral lobe and adjacent hemisphere (SC function and postural tonus)
3) Neocerebellum - vermis of the caudal lobe and most of the cerebellar hemispheres (skilled movement)
Division of cerebellum into longitudinal zones of the cortex and nuclei?
1) Medial zone: vermis + fastigial nucleus (tone for posture and locomotion and equilibrium of the entire body)
2) Intermediate zone: paravermal cortex and interposital nuclei (adjusting motor tone and posture to regulate skilled movements)
3) Lateral zone: lateral nuclei and lateral portion of the hemisphere (regulating skilled movements of the limbs - highly developed in primates)
- rostral portion of the cerebellum - inhibition of LMNs that innervate antigravity extensor muscles of the neck and thoracic limbs. It thus participates with the UMN in the support of the body against gravity.
Neuro signs with cerebellar disease?
** NO loss of strenght
** NO diffuse, whole body tremor
1) cerebellar ataxia
2) spasticity
3) dysmetria (inability to control the rate, range and force of movement)
4) broad based stance
5) titubation - truncal ataxia/truncal sway
6) fine head and neck tremor (intention tremor) - dysmetria of the head/neck
7) opisthotonus
8) delayed and exaggerated postural reactions (ispilateral)
9) abnormal positional nystagmus (diffuse disorders, no consistency in the direction of the nystagmus)
10) head rebound phenomenon: if the head and neck are extended, and then the support is suddenly withdrawn, the head may rapidly descend ventrally beyond the normal neutral position (may also be seen with bilateral vestibular disease)
11) decerebellate posture (with rostral cerebellar lesion - inhibitory to limb extensor muscles)
12) contralateral head tilt (paradoxic vestibular disease)
13) anisocoria (fastigial and interposital nucleus)
14) menace response deficits with normal vision (diffuse lesions, especially lateral and interposital nuclei) (ipsilateral)
Dysfunction of which structures of the cerebellum causes vestibular signs?
Floconodular lobe,
fastigial nucles,
Caudal pedunculi
(loss of equilibrium, abnormal nystagmus, bizarre postures, and a broad-based staggering gait with jerky movements and a tendency to fall to either side or backward)
Canine in-utero infections causing cerebellar hypoplasia?
Very rare, clinical signs present at birth,
- potentially parvovirus,
- herpersvirus during first week of life.
(cortical abiotrophy usually after 1 week of age, with some cases onset > 1 year of age)
Gene in children responsible for cerebellar hypoplasia/dysplasia and lissencephaly.
Which dog breed is affected with cerebellar hypoplasia? (Same gene defect)
RELN (codes reelin - a protein important in neuronal migration)
Swiss white shepherd
Dog breeds with cerebellar abiotrophy?
Border Collie
Lagotto Romagnolo
Labrador retriever
Brittany spaniel (Adult onset 5-11 years age of onset)
English bulldog
Old English sheepdog (adult onset)
Gordon setter (adult onset)
Finnish hound
Boxer (adult onset)
Australian working kelpie (AWK)
Beagle
Italian spinone
Scottish terrier
American Staffordshire terrier (18 months to 9 years)
Which cells are usually affected in cerebellar abiotrophy?
Purkinje cells
In most animals the granular layer neurons will also be depleted. This status is believed to be a retrograde form of degeneration because these neurons no longer have any dendritic zones for their synapses once the Purkinje neurons have degenerated
What are Bergman astrocytes?
In chronic cases of cerebellar abiotrtophy no Purkinje neurons may be present, and in their place (and in the molecular layer) there may be an accumulation of astrocytes that in humans are sometimes referred to as Bergman astrocytes.
The expression “empty baskets” has been applied to the finding of these astrocytes surrounding the void left once the Purkinje neurons have been lost
DDs for cerebellar abiotrtophy?
Inflammation, cystic malformation, and neoplasia.
Patients with cerebellar abiotrophy usually have an onset of clinical signs at an age that is uncommon for neoplasia. Cerebellar medulloblastoma (primitive neurectodermal tumor) is a rare neoplasm seen in young dogs and cattle.
Epidermoid, dermoid, or neuroendodermal cysts are uncommon; the most common site for these cysts to occur is in the caudal cranial fossa, where the cerebellum may be affected by their progressive enlargement as a result of their secretory activity.
Inflammation is common at this young age, which is when many of the abiotrophies occur, but its limitation to the cerebellum is unexpected. However, an exception to this rule exists. Neosporosis in young adult dogs has a predilection for the cerebellum.
Which lobules are usually affected in Kerry Blue terriers with cerebellar abiotrophy?
The dorsal lobules (unknown why)
Breeds of dogs with multple system degeneration? Name the causative gene
Chinese crested
Kerry Blue terrier
SERAC1 (serine active site containing 1): codes a protein found at the interface of mitochondria and endoplasmic reticula, where it mediates phospholipid exchange
Cerebellar cortical and extrapyramidal nuclear abiotrophy
What is specific in Scotish terriers with cerebellar abiotrophy (which pathologic feature besides Purkinje cell degeneration)?
- accumulation of polyglucosan bodies primarily in the molecular layer of the cerebellar cortex
Urkasemsin G, Linder KE, Bell JS, de Lahunta A, Olby NJ. Mapping of Purkinje Neuron Loss and Polyglucosan Body Accumulation in Hereditary Cerebellar Degeneration in Scottish Terriers. Veterinary Pathology. 2012;49(5):852-859. doi:10.1177/0300985811412622
Main DD for a Scotish terrier with abiotrophy (based on neuro signs) and how would you differentiate?
Dystonic movements in Scottie cramping syndrome (can be difficult to tell apart due to short legs)
Scottie cramp is an episodic disorder and abiotrophy has constatn progressive signs
Specific pathologic lesions besides Purkinje cell degeneration in Britany spaniels w/ cerebellar abiotrophy?
- neurofilament accumulation (bilateral lesions are present in the medullary GP nuclei and the spinal cord dorsal horn neurons)
- sporadic axonal degeneration is present in the spinal cord white matter
Figure. 1 Section from the cerebellum demonstrating the empty bas-ket cells associated with the segmental Purkinje cell loss. There is alsoan axonal torpedo in the granular cell layer. Bodian’s stain, ×230Fig. 2 Section of the molecular layer of a cerebellar folium withmultiple round to ovoid structures, some of which are withinprocesses of the dendritic arborization of Purkinje cells (arrows).Bodian’s stain, ×260Fig. 3 Individual neuronal chromatolysis (arrow) in the dorsalgray matter horn of the spinal cord. Bodian’s stain, ×180Fig. 4Wallerian-like degeneration in the ventro-lateral spinal cordwhite matter with random swollen axonal sheaths containing axonalspheroids or macrophages (arrows). There is also patchy chronicloss of myelinated axons and mild astrogliosis. H&E stain, ×70Fig. 5 Electron micrograph of an affected Purkinje cell whose cy-toplasm is distended with excessive neurofilaments, ×22 000
Higgins RJ, LeCouteur RA, Kornegay JN, Coates JR. Late-onset progressive spinocerebellar degeneration in Brittany Spaniel dogs. Acta Neuropathol. 1998 Jul;96(1):97-101. doi: 10.1007/s004010050865. PMID: 9678519.
Two specific cerebellar diseases of the Coton de Tulear breed
1) Neonatal ataxia of coton de Tulear puppies is an example of a functional disorder (no visible pathological changes). At birth, their ataxia may be so severe that they may not be able to stand to walk. Pedigree studies support this as an autosomal recessive inherited disorder. These puppies have a genetic mutation in the glutamate receptor expressed on Purkinje neuronal cell membranes associated with their dendritic zones in the molecular layer. This interferes with the synaptic activity between the telodendrons of the granule cell parallel fibers and the Purkinje neuronal dendritic zones. Ultrastructural studies have revealed morphologic abnormalities in the molecular layer of affected puppies with lack of presynaptic parallel fiber varicosities and decreased synaptic vesicle concentration.
2) Postnatal cerebellar ataxia described in the coton de Tulear breed associated with a loss of granule cells believed to be related to an autoimmune disorder
Main pathological findings in FPV cerebellar hypoplasia?
- granuloprival hypoplasia - destruction of the cerebellar external germinal layer. Destruction of this layer prevents the formation of the granular layer, hence the name granuloprival hypoplasia.
- in some kittens extensive destruction to the parenchyma occurs, with loss of all layers of the cerebellar cortex and much of the cerebellar medulla and nuclei. These severe lesions may be the result of an earlier in utero infection with this virus. The necrosis of neuronal tissue that has completed its development results in atrophy.
Which breed of cat has a described cerebellar abiotrophy?
- DSH (onset > 1 yr)
- Siamese (> 1 yr)
- Persian (> 7ysr)
- mix-breed 6-8 weeks
Which breed of horses is has a reported cerebellar abiotrophy?
Arabian and Arabian-mix breeds (autosomal recessive)
target of EGR1 (TOE1) variant
Neuro signs in Arabian foals with cerebellar abiotrophy
- spastic gait (rarely hypermetric): mimics UMN paresis
- marked swaying of the head and neck from side to side during running
- head and neck tremor (may be the earliest clinical sign observed)
- rearing up, losing its balance, and falling over backward.
- reduced/absent menace response
Although the gait may somewhat mimic a UMN and GP system dysfunction in the cervical spinal cord, the intentional head tremor and the tendency to rear up with the thoracic limbs in full extension when stimulated excludes this consideration.
Causative agent for calves with cerebellar hypoplasia/atrophy and patho-mechanism?
BVDV most likely (does not cause arthrogruphosis, can cause hydranencephaly but to a lesser extent than cerebellar hypoplasia)
DD: Shmallenberg, Akabane and Bluetongue (cause also hydranencephaly and arthrogryposis)
- DeLahunta note: This malformation should not be summarily diagnosed as cerebellar hypoplasia. Only the absence of granular layer neurons represents hypoplasia because BVDV infection destroyed the external germinal layer, which is the origin of this neuronal layer. The massive destruction of the already differentiated Purkinje neurons, the folial white matter laminae and, in some calves, the cerebellar medulla and nuclei is a degeneration of parenchyma caused by the necrotizing action of the virus and the resulting inflammation. This degeneration results in atrophy. Thus the malformation observed at birth is a combination of hypoplasia and atrophy. The degree of cerebellar lesion in newborn calves varies from a slight gross deformity to almost complete absence of any cerebellar tissue. In the latter case, only a small band of smooth parenchyma may remain over the fourth ventricle, where the cerebellum should normally be located. Where folia are present, the cortex is often depleted of varying amounts of its neuronal layers, and the area of the folial white matter lamina is replaced by a cavity. Mild astrogliosis may be the only indication of where a previous cortex existed.
Which aditional pathological findings are observed (besides the cerebellar lesions) in calves infected in-utero with BVDV?
- hydranencephaly
- ocular lesions (retinal atrophy, cataracts, microphthalmia, retinal dysplasia, and optic neuritis)
Three DDs for a young non-ambulatory calf with opistotonus?
How would you differentiate based on the neuro exam?
- Cerebellar abiotrophy
- thiamin defficiency polioencephalomalacia
- bacterial meningitis
Their alert sensorium and intact vision, despite a lack of a menace response, helps differentiate abiotrophy from a thiamin deficiency–induced polioencephalomalacia and bacterial meningitis.
Two forms of cererbellar cotical degeneration (CCD)?
1) primary Purkinje cell degeneration (most common)
2) primary granule cell or “granuloprival” degeneration.
Name te breeds with identified genetic variants and regions of interest with canine cerebellar cortical degeneration as well as the gene
Genetic variants have so far only been associated with Purkinje cell degenerations:
Beagle,
Finnish Hound,
Gordon Setter,
Old English Sheepdog,
Viszla.
Regions of interest have been identified in the Scottish Terrier (primary Purkinje cell degeneration) and
Australian Kelpie (granuloprival degeneration)
Name the breeds for different spinocerebellar degenerations
SAMS = spinocerebellar ataxia with (or without) myokymia, seizures, or both;
SDCA = spongy degeneration and cerebellar ataxia
Breeds without a known genetic variant in cerebellar cortical degeneration (abiotrophy)
Breeds with spinocerebellar degeneration without known gene variant
Which type of hereditary ataxia is usually acompanied by miokimia and what are the predisposing factors?
Myokymia is seen in up to 70% to 75% of affected Jack and Parson Russell Terriers, Patterdale Terriers
but is much less frequent in Smooth Haired Fox Terriers, Malinois Shepherds and Bouviers des Ardennes with SAMS (Spinocerebellar ataxia with/without myokimia and seizures)
Exercise, excitement, and hot weather are predisposing factors
What is neuromyotonia?
Myokymia and neuromyotonia are often discussed together as most dogs suffering from myokymia develop neuromyotonic episodes (about 80% of dogs).
Neuromyotonia is characterized by muscle stiffness leading to a collapse into lateral recumbency without loss of consciousness, lasting from several minutes to several hours. Potentially lifethreatening hyperthermia (>43C) and tachypnea are frequent during those neuromyotonic episodes, causing spontaneous death of some dogs. In about half of the dogs, myokymia, muscle stiffness, and collapse are preceded by intense facial rubbing.
In a minority of dogs, neuromyotonia can precede myokymia.
Electromyography of muscles clinically affected by myokymia shows myokymic or neuromyotonic discharges.
BAER changes in dogs with hereditary spinocerebellar ataxia?
Brainstem auditory evoked recordings of these dogs show loss of waves III, IV, and V, as well as in most cases mildly increased latencies for waves I and II
Pathohystological changes in dogs with hereditary spinocerebellar ataxia?
- bilateral symmetrical myelopathy
- severe degenerative changes in the CNS auditory pathways.
The myelopathy is characterized by a predominant axonopathy with myelin swelling, vacuolization, and astrogliosis (most severe in the dorsolateral and ventromedial funiculi of the cervical spinal cord). A common feature is loss of myelinated axons and diffuse gliosis in the central auditory pathways most
severely affecting the dorsal nucleus of the trapezoid body, but also involving the trapezoid body, cochlear nuclei, and lateral lemniscus.
These degenerative CNS auditory pathway changes are not described in Smooth Haired Fox Terrier, where the lesions appear limited to the spinal cord.
Variants of which gene are most commonly associated with canine spinocerebellar ataxia with myokimia/seizures?
KCNJ10,
encodes for the potassium inwardly rectifying channel subfamily J member 10 (KCNJ10), a voltage-gated potassium channel (VGKC) that is mainly expressed in the brain, spinal cord, inner ear, and kidneys.
Name 3 breeds with a hereditary cerebellar ataxia without structural neurodegenerative changes (functional diseases)
Coton de Tulear (neonatal cerebellar ataxia)
Italian Spinone (Spinocerebellar ataxia)
Norwegian Buhund (Hereditary ataxia)
Two breeds with multiple system degeneration?
- Kerry Blue Terrier
- Chinese Crested dogs
Two dog breeds with late onset of cerebellar abiotrophy?
- American Stafordshire Terrier (13 mo - 9 yrs)
- Brittany Spaniel (7-13 yrs)
Two dog breeds with late onset of cerebellar abiotrophy?
- American Stafordshire Terrier (13 mo - 9 yrs)
- Brittany Spaniel (7-13 yrs)
Dog breed with congential vestibular disease caused by lymphocytic labyrinthitis?
Doberman pintscher
Forbes S, Cook J.R. Congenital peripheral vestibular disease attributed to
lymphocytic labyrinthitis in two related litters of Doberman Pinscher
pups. J Am Vet Med Assoc. 1991;198:447–449.
Dog and cat breeds with unilateral congenital vestibular disease
German Shepherd Dog, Doberman, Smooth Haired Fox Terrier, English Cocker Spaniel
Siamese, Burmese, Tonkinese
Ettinger (Veronika Stein)
Bilateral congenital vestibular disease has been described in which dog breeds?
Akitas and Beagles
The disease is thought to be due to progressive loss of the sensory hair cells of the vestibular and hearing system
Ettinger (Veronika Stein)
