Diseases of the Nervous System

Diseases of CNS: Brain

• Trauma

• Idiopathic vestibular disease

• Neoplasia

• Idiopathic epilepsy

• Status epilepticus

Diseases of CNS: Spinal Cord

• Intervertebral disc disease

• Trauma

• Atlantoaxial subluxation

• Cervical spondylomyelopathy

• Degenerative myelopathy

• Discospondylitis

• Ischemic myelopathy

Disease of PNS

• Deafness

• Metabolic neuropathy

• Laryngeal paralysis

• Megaesophagus

• Tick paralysis

• Facial nerve paralysis

Brain Trauma

• Acute clinical onset from traumatic experience (HBC, Falling)

• Injury to brain from:

  • Primary Event: Direct injury to nervous tissues

  • Secondary Event: Occur as result of primary trauma

    • Increased Cranial Pressure

    • Edema

    • Hypoxia

    • Seizures

• Primary events may cause irreversible disruption of fiber tracts or reversible cell damage

• Secondary events may cause herniation of Nervous Tissue through Foramen Magnum

What happens in the Primary Event of Brain Trauma

Direct injury to nervous tissues

What is the Secondary Event of Brain Tauma?

Occurs as a result of primary trauma

Secondary Event Brain Trauma happens because of

• Increased intracranial pressure

• Edema

• Hypoxia

• Seizures

Primary Events may cause

Irreversible disruption of fiber tracts or reversible cell damage

Secondary Events may cause

Herniation of nervous tissues through foramen magnum

CS of Brain Trauma

• Hx of trauma to head

• Seizures

• Blood in ears, nose, oral cavity

• Ocular hemorrhage

• Loss of consciousness/ decrease in response to external stimuli

• Signs of shock (Cardia Arrhythmias, Altered Resp. Patterns, Coma)

Dx of Brain Trauma

• Hx & PE

• Rads

• CT or MRI

Tx of Brain Trauma

• Aimed @ preventing/decreasing secondary effects of trauma

• Correct any metabolic derangements

• Provide oxygen

• Elevate head

• Admin osmotic agents to decrease cerebral edema:

  • Mannitol

  • Furosemide

• Ain’t-seizure medication if needed

• Corticosteroids for shock

Idiopathic Vestibular Disease

• “Old Dog Vestibular Disease”

• Abnormality of vestibular system due to unknown reason

• Acute disorder of older aged (mean 12 years) dogs & cats

• CS usually resolve in 3-6wks

CS of IVD

• Loss of balance (incapacitating)

• head tilt

• Nystagmus

• Disorientation

• Ataxia

• Circling/falling over

• Anorexia

Dx of IVD

• CS

• Otic exam to rule out inner ear problem

• BW to rule out other dz involving nervous system

Tx of IVD

• Supportive Therapy

  • Anti-emetics

  • Motion sickness meds

  • IV fluids

• Keep in confined padded area

• Spontaneously resolves****

  • Head tilt may persist

Brain Neoplasia

• Enlarging tumor in brain

• Causes tissue compression &/ replaces healthy neuronal tissue

• May be primary or metastatic

• Most common in OLDER animals

• CS progressive

Brian Neoplasia: Primary vs Metastatic

Primary: Typically Singular

Metastatic: May be singular or multiple

CS Brain Neoplasia

• Reflect location

• Progresses as tumor grows

• Seizures

• Endocrine derangements

• +/- Vestibular signs

• Tremors, Ataxia

Dx of Brian Trauma

• Systemic screening for primary tumors in other organs

  • BW, Rads, Ultrasound

• CSF tap

  • Increased pressure + albumin, Normal WBC count

• Ophthalmic Exam:

  • Optic Nerve Edema

• ****CT or MRI****

Tx of Brain Neoplasia

• Tumor

  • Sx removal

  • Radiation

  • Chemotherapy

• CS:

  • Anti-seizure meds

  • Corticosteroids

Idiopathic Epilepsy

• Repeated episodes of seizures with no cause

• Seizures usually begins b/t 1-6 years

• INCURABLE dz

CS of Idiopathic Epilepsy

• Seizures, often at regular intervals

• Young animals typically affected

• Normal behavior b/t seizures

Dx of Idiopathic Epilepsy

• 1 of exclusion

• BW to rule out Hypocalcemia, Hypoglycemia, Infection, Hepatic Encephalopathy, Lead Poisoning

• Rads to rule out head trauma or hydrocephalus

• CT or MRI to rule out space-occupying lesion

Tx of Idiopathic Epilespy

• Initiated if seizure freq. more than once per month

• Anti-seizure Meds:

  • Phenobarbital

  • Potassium Bromide

  • Zonisamide

  • Gabapentin

  • Keppra

Status Epilepticus

• Continual seizures for prolonged period ( over 5-10 mins)

• Medical EMERGENCY:

  • Can lead to irreversible coma and death!

CS of Status Epilepticus

Prolonged, uninterrupted seizure activity

Tx of Status Epilepticus

• IMMEDIATE

  • Diazepam IV

• Maintenance:

  • Anti-Seizure meds

Intervertebral Disc Disease

• Disc protrusion/extrusion

• Most common in cervical, caudal thoracic & lumbar spine

IDD Severity Depends On:

• Speed @ which disc material is deposited into spinal canal

• Degree & Duration: of compression

• 2 types of herniation

Type I: IDD

Acute rupture of annulus fibrosis & extrusion of nucleus pulposus in into spina canal

Common in YOUNGER dogs

Type II: IDD

• Extrusion over longer period, prod. less acute & less severe CS

• Common in OLDER (over 5 years) LARGE breed dogs

CS of IDD

• Depends on location & type

• Apparent pain

• Presence/Absence of motor/sensory deficits

• Paresis/Paralysis: May be unilateral or bilateral

• Decreased panniculus reflex 1-2 vertebral spaces caudal to actual lesio

• Altered deep pain response

Dx of IDD

• Age, breed, CS, Hx

• Compete Neurologic exam

• Rads: Narrowed disc spaces @ location of lesion

• Myelogram

• MRI

Tx of IDD: Type I

• Medical Tx:

  • Strict confinement for min. 2 wks

  • Corticosteroids

• Intensive Nursing Care:

  • Soft padding in cage

  • Indwelling urinary catheter if necessary

• Surgical Tx:

  • Fenestration, Hemilaminectomy

  • Reversed for animals w multiple episodes, ataxia, paresis/paralysis & absence of deep pain

Tx of IDD: Type II

Corticosteroids

Spinal Cord Trauma

• Acute injury to spinal cord causing tissue injury

• Direct & Indirect effects

• Commonly resulting from: HBC, Gunshot wounds, Fights

• Auto-dissolution of cord may be seen as early as 24hr after injure

Spinal Cord Trauma: Direct Effects

Due to primary disruption of neural pathways in cord

Spinal Cord Trauma: Indirect Effects

• Triggered by direct effect

• Edema, hemorrhage, ischemia, inflammation

Ischemia

Vesibular

CS of Spinal Cord Trauma

• Hx of trauma

• Presence of Schiff-Sherrington sign****

• Lack of panniculus reflex causal to lesion

• Paresis/Paralysis

Paresis

Paralysis

Schiff-Sherrington Sign

• Rigid HYPERtonicity of front legs

• HYPOtonicity of rear legs

• Normal reflexes

• Normal pain perception

Dx of Spinal Cord Trauma

• Complete neuro exam to localize region

• Rads

• Myelogram

• MRI

Myelogram

Tx of Spinal Cord Trauma

• Medical:

  • Corticosteroids

  • Strict confinement for 6-8weeks

• Surgical:

  • Initiate within 2hr if possible

  • Considered in severe paresis/paralysis cases or evidence of continuing cord compressing/worsening CS

  • Laminectomy @ all sites of cord compression

  • Removal of all bone frags/ disc material from spinal cord

  • Strict confinement: 2wks

Atlantoaxial Subluxation

• Trauma when cranial portion of axis is displaced into spinal column

• Displacement may be a result of:

  • Congenital/Development abnormalities

  • Trauma

  • Combo of both

• Most common in YOUNG (Under 1 yr) TOY & MINI breeds of DOGS

CS of AAS

• Reluctance to head pats

• Neck pain

• + /- Tetra-paresis/ Tetraplegia

• Sudden death! Due to respiratory paralysis

Tetra-paresis

Tetraplegia

Dx of AAS

• Rads:

  • Lateral projection with neck in slight ventriflexion

  • Care must be taken to avoid further spina cord damage***

  • No anesthesia

TX of AAS

• Medical:

  • Splint neck in EXTENSION

  • Strict cage confinement: 6 wks

• Sx:

  • (IF neurological deficits/neck pain unresponsive to med tx)

  • Strabilization

  • Decompression

  • Combo of both

Cervical Spondylomyelopathy

• Wobbler Syndrome

• Cervical spinal cord compression as result of: CAUDAL VERTEBRAL (C5-C7) malformation/misarticulation

• LARGE BREED DOGS:

  • Dobermans, Great Danes

  • Onset before 1 year in Danes, 2 years in Dobermans**

• Progressive

CS of Cervical Spondylomyelopathy

• Hx of progressive pelvic limb ataxia

  • Legs may cross, abduct widely, tend to collapse

• Abnormal wearing of dorsal surface or back paws, nails, both

• Swingling/wobbly gait in back legs (worse on rising)

• Similar signs in front legs

• + /- Atrophy in front legs

• Riding flexion of neck but NO NECK PAIN

Dx of Cervical Spondylomyelopathy

• Rads, May Indicate:

  • Malalignment/ “Slipping” of vertebrae

  • Remodeling, new bone formation, narrowing of spinal canal

• Myelography

  • Essential in locating regions of compression

• CT & MRI

Tx of Cervical Spondylomyelopathy

• Medical:

  • Anti-inflammatory doses of Corticosteroids

  • Neck brace

  • Cage confinement

• Surgical:

  • Decompression:

    • Laminectomy/ Ventral Slot Procedures

• Stabilization

Degenerative Myelopathy

• Diffuse, irreversible degeneration of WHITE MATTER on ascending/descending tracts in ALL segments of spinal cord (Lesion most extensive in thoracic region)

• Exact cause unknown (may be from autoimmune response to antigen in NS)

• Seen mostly in GERMAN SHEPHERDS (over 5 years)

• Progressive, INCURABLE dz

CS of Degenerative Myelopathy

• Hx of progressive hind limb paresis & ataxia for 5-6 moths

• Muscle atrophy

Dx of Degenerative Myelopathy

• Neurological Exam:

  • Lesion in region *****T3-L3******

  • Decreased/Absent proprioception & placing reactions

  • Increased - Normal patellar reflexes

  • Lack of pain

  • Normal sphincter tone

  • Normal panniculus reflex

• Rads:

  • May show dural ossification/narrowed disc spaces

• CSF tap

  • May show increased protein concentration from lumbar subarachnoid space

Tx of Degenerative Myelopathy

• NONE

• Symptoms slowly progress until animal = nonambulatory

Discospondylitis

• “Vertebral Osteomyelitis”

• Bacteria/ Fungi implanted on bones of vertebral column

• Implantation may occur:

  • **Most Common: Hematogenous Route

  • Penetrating wound

  • Paravertebral abscess/infection

  • Sx of vertebral column

  • Migration grass awns

CS Discospondylitis

• Weight losss

• Fever of unknown origin

• Reluctance to excercise

• Spinal pain

• Hyperesthsia over lesion

• + /- Neurological signs

Dx of Discospondylitis

• Rads:

  • May show destruction or lysis of bony end plates adjacent to lesion, osteophyte formation, collapse of intervertebral disc space

• CBC: May show increased WBC count

• Aerobic, Anaerobic, Fungal cultures of Blood, CSF, Urine

• Sx biopsy & tissue culture

Tx of Discospondylitis

• Long-term antibiotic/antifungal therapy ( at least 6wks, may be up to 6months

  • C&S

• Pain Management

• Sx?

Ischemic Myelopathy

• Caused by fibrocartilagenous embolism

• Necrosis of spinal cord gray & white fiber tracts when FCE obstruct veins & arteries in both leptomeninges & cord parenchyma

  • Reduced blood flow

• Most common: LARGE & GIANT breed dogs

CS of Ischemic Myelopathy

• Hx of mild-to-moderate exercise before development of CS

• Acute onset of Neurologic signs:

  • May appear progressive @ first, but stabilize after first 24 hrs

• Lack of acute spinal pain associated with Neurologic sign

• Paresis or spastic paralysis of limb

• Reluctance to move, inability to rise

Dx of Ischemic Myelopathy

• Based on excursion:

  • Rads, CBC, CSF usually WNL

• MRI

Tx of Ischemic Myelopathy

• Corticosteroids

• Nursing Care: May take months to recover

Peripheral Neuropathies

• Represented clinically by a group of signs

  • Neuropathic Syndrome

• Signs Include:

  • Reduced/ Absent muscle tine

  • Weakness (paresis) / paralysis of limb / facial muscles

  • Followed by neurogenic muscle atrophy in 1-2 wks

• May involve a single nerve or multiple

Deafness

• Inability to hear

• May be central or peripheral origin

• Conductive deafness

• Hereditary or congenital, related to drug therapy, or normal aging

• Permanent / Irreverible

Deafness: Central Origin

From damage to CNS & auditory pathways

Deafness: Peripheral Origin

From cochlear abnormalities

Conductive Deafness

From chronic otitis, rupture of tympanic membrane, damage to middle ear

This medicine can cause deafness

Mometamax

CS of Deafness

• Lack of response to auditory stimuli

• Excessive sleeping

• Prone to deafness

  • Bull terriers, Dobermans, Dalmatians, Rotts, Pointers, Aussies, BLUE EYED WHITE CATS

Dx of Deafness

• Partial loss hearing & unilateral complete loss of hearing difficult to est. clinical exam

• Inability to abuse sleeping pt with loud noise

• Behavior evaluation

  • Stimulate with various sounds from diff. Directions

  • PE of external ear canal & tympanic membrane

Deafness: Electrodiagnosis

• At specialty clinic

• Tympanometry

• Acoustic reflex testing

• Auditory evoked responses (BAER)

Tx of Deafness

• None

• Hearing aids?

Laryngeal Paralysis

• may be hereditary, acquired, idiopathic

• *****Care must be taken when examining animal w suspected laryngeal paralysis

Hereditary: Laryngeal Paralysis

Bouvier does Flanders & Siberian Huskies

Acquired: Laryngeal Paralysis

From lead poisons, *RABIES, trauma, inflammatory infiltrates of vagus nerve

Idiopathic: Laryngeal Paralysis

In MIDDLE-TO-OLD aged LARGE to GIANT breed dogs

CS of Laryngeal Paralysis

• Inspiratory stridor

• Respiratory distress

• Loss of endurance

• Voice change

• Cyanosis

• Complete respiratory collapse

Stridor

Dx of Laryngeal Exam

• Laryngeal Exam

  • Laryngoscopy: shows Laryngeal Abductor Dysfunction

Tx of Laryngeal Paralysis

• Sx

  • Arytenoidectomy

  • Arytenoid lateralization

  • Removal of vocal chords

Megaesophagus

• Lack of effective esophageal peristalsis, resulting in dilation of esophagus, regurgitation of undigested food

• Congenital, Hereditary, Acquired

Congenital: Megaesophagus

• Great Danes, German Sheps, Irish Setters, Newfoundlands, Sharpeis, Greyhounds

• Usually becomes evident around WEANING

Hereditary: Megaesophagus

Wire-haired fox terriers & mini schnauzers

Acquired: Megaesophagus

May be due to metabolic neuromuscular dz, distemper, tick paralysis, lead poisoning, laryngeal paralysis -polyneuropathy complex, or polymyositis

CS of Megaesophagus

• Regurgitation of undigested food

• Respiratory Signs:

  • Cough, Dyspnea, Drooling, Pneumonia

• Lack of growth / Weight loss

Dx of Megaesophagus

• Rads: Dilated esophagus to level of diaphragm

Tx of Megaesophagus

• NO CURE: Prevent development of aspiration pneumonia

• Elevated feeding platform

• Liquid soft diet high in caloric density

• Several small feedings daily

• Treat any underlying metabolic disorders

Tick Paralysis

• Flaccid, Afebrile, Ascending motor paralysis

• Caused by common dog tick (Dermacentor Variablis) & Rocky Mt. Wood Tick (Dermacentor Andersoni)

  • Female tick = salivary neurotoxin that interferes w acetylcholine concentrations @ neuromuscular junction

• Cats RESISTANT

CS of Tick Paralysis

• Gradual development of hind limb in coordination → flaccid ascending paralysis

  • Within 24-72hr, may become recumbent

  • Reflexes lost while sensation remains

  • Death may occur due to respiratory paralysis

• Presence of ticks on dog

Dx of Tick Paralysis

• Based on exclusion

• Based on response to tick removal

Tx of Tick Paralysis

• Remove all ticks

• Supportive care

Facial Nerve Paralysis

• Idiopathic, acute paralysis of facial nerve

• Seen in adult dogs & cats (Over 5 years)

• Cause unknown