Lumbosacral disease and neurological bladder dysfunction Flashcards
Name 2 signs of LMN dysfunction
- decreased reflexes
- decreased mm tone
Name 2 signs of UMN dysfunction
- normal/increased reflexes
- normal/ increased mm tone
What is cauda equina syndrma?
- dysfunction of tail, urinary and anal sphincters. Bladder and pelvic limbs affects (sciatic signs)
- L7 caudal nn roots are affected
What is a ddx for cauda equina syndrome?
L4-S3 myelopathy
Ddx - chronic (acute exacerbation), progressive, asymmetrical but not markedly painful L4-S3 myelopathy
- DLSS
- IVDD (another site)
- discospondylitis
- myelitis
- neoplasia
- illiopoas mm injury
- …
What is DLSS?
= Degenerative Lumbosacral stenosis
- multifactoral disorder (combination of soft tissue and/or bony changes causing LS vertebral canal stenosis)
- RESULT = cauda equina +/- L7 nn root compression (pain)
What is discospondylitis?
bacterial infection of the disc space - often febrile
List some soft tissue and bony changes that can cause LS vertebral stenosis?
- intervertebral disk protrusion
- ligamentous hypertrophy
- articular process hypertrophy
- osteophyte formation
- vertebral misalignment
- telescopy dorsal lamina
- transitional vertebra
- lumbosacral osteochondrosis (OCD)
Which animals are affected by DLSS?
- typically adult/ older large breeds
- PREDISPOSITIONS: GSD, active/ working dogs, LS malformations
CS - DLSS
- lumbosacral pain
- pelvic limb lameness (root signature)
- reluctance to jump, run stairs, jump into car
- paraparesis/ ataxia
- low tail carriage, flaccid tail
- urinary and faecal incontinence
- ORTHOPAEDIC EXAM: pain on direct lumbar spinal palpation, pain on hip extension
Where does the pudendal nerve originate?
comes off the sacral nn
How can you differentiate OA/ stifle disease from DLSS/ neuro conditions?
PAW POSITIONING REFLEXES: likely present with OA/ stifle disease and very reduced or absent with neuro disease
Dx - DLSS
IMAGING AND CS (consistent) +/- electrodiagnostics
What does a lumboscaral transitional vertebra in the dog predispose?
8 x increased risk of developing cauda equina syndrome
How useful is myelography?
rarely useful
Method - myelography
- injection of radioopaque contrast into subarachnoid space
- thecal sac generally narrows and ends near LS
- may see attenuation of contrast over LS if severe midline compression
What is the thecal sac?
membrane of dura mater that surrounds SC and cauda equina, filled with CSF
What does CT show as surrounding the cauda equina nerve and thecal sac? How does this change in DLSS
epidural fat surrounds the cauda equina nn and thecal sac, providing a natural source of tissue contrast. In DLSS epidural fat is displaced: confuses differentiation compressive soft tissue and adjacent neural structures.
What does intravenous contrast-enhanced CT show?
discrimination of compressive soft tissues within the vertebral canal
What is the diagnostic imaging modality of choice for DLSS?
MRI (as a T1w image)
- shows displacement of epidural fat around the spinal cord and nn root compression as they come off the cauda equina
Overview - tx of DLSS
Medical or surgical
Medical tx - DLSS
- activity restriction
- +/- anti-inflammatories (NSAIDs)
+/- analgesics
+/- neuromodulatory drugs (gabapentin) - topical corticosteroids (epidural injection)
Sx tx - DLSS
- decompressive laminectomy \+/- discectomy - foraminotomy - stabilisation - distraction + stabilisation
How do electrodiagnostics help in diagnosing DLSS?
MAY assist in determining clinical significance of radigraphic lesions
What do CT findings for DLSS suggest?
that some lumbosacral CT abnormalities may be clinically insignificant, especially in older dogs.
What is discectomy?
excision of protruding annulus fibrosus
How succesful is decompressive laminectomy?
Good to excellent outcome in 78% dogs. Significant correlation b/w presence of urinary incontinence prior to sx and poor outcome.
What is gabapentin?
neuromodulator to control nn root pain
CS - cauda equina syndrome - horses
- tail paralysis
- dilated anus
- loss of perineal sensation
- faecal retention
Ddx - Equine cauda equina syndrome - 3
- TRAUMA: sacral fracture (common)
- INFECTIOUS: EHV-1 myeloencephalopathy (highly infectious and fatal)
- INFLAMMATORY: polyneuritis equi
Why might you have an absent cutaneous trunci lesion on RHS lumbar region?
Right brachial plexus lesion
Describe the cutaneous trunic reflex pathway
= 3 neuron pathway:
- peripheral/sensory
- second order neuron - both sides of SC
- motor neuron
What drug toxicity can cause Schiff-Scherrington posture?
Metronidazole.Tx is simply to stop giving the animal this drug. Usually a higher than recommended dose is being used (usually 30mg/kg +)
T/F: don’t give animals a poor prognosis based on severity of CS
True. Don’t always impulse euthanase if your case has severe neuro signs.
What is decompressive laminectomy?
sx to relieve pressure on nn roots. It removes part of vertebrae and/or thick tissue that is narrowing sinal cord and squeezing spinal roots
Where will proprioceptive deficits be seen if lesion is in forebrain/ thalamus?
contralateral side
Where will proprioceptive deficits be seen if lesion is in the brainstem?
ipsilateral side
How do you differentiate a lesion in optic chiasm versus bilateral occulomotor paralysis?
menace reflex - present with occulomotor paralysis (turning head/neck/trunk away, blinking may be absent). Will be absent with optic chiasm lesion.
T/F: if the limbs aren’t working, the bladder may not be either
True
Name the bladder mm
Detrusor mm (SMC)
What are the mm in the urethra?
- Internal urethral sphincter (SMC)
- External urethral sphincter (skeletal mm)
Location of micturition centre
pons
Origin - hypogastric nn
L1-L4
Origin - pelvic nn
S1-3
Origin - pudendal nn
S1-3
Describe bladder in storage phase
- sympathetic dominance
- bladder relaxes with stimulation of B-receptors
- urethral sphincter contracts with stimulation of A-receptors
- parasympathetic tone inhibited
Describe the bladder in the voiding phase
- parasympathetic dominance
- bladder contracts with stimulation of muscarinic Ach-Rs
- urethral sphincter relaxes
- sympathetic tone inhibited
Where does input come from for sympathetic dominance in storage phase?
- cerebral cortex
- cerebellum
Outline the somatic component of bladder storage phase
- somatic control (voluntary motor control)
- under the influence of pudendal nn –> Ach –> urethral sphincter mm contraction (nicotinergic cholinergic receptors)
- pudendal nn arises from S1-S3
Outline parasympathetic component of voiding phase
- pelvic nn controls this
- from S1-S3
- causes bladder to contract by release of Ach onto muscarinic cholinergic receptors on bladder
What is a UMN bladder?
- lesion between pons and L7
- L1-4 affected (hypogastric)
- hallmark: increased bladder tone
- turgid easily palpable bladder, increased urinary sphincter tone
- EXPRESSION: difficult
What is a ‘LMN bladder’?
- lesion b/w sacral spinal cord or sacral nn
- this is a potential finding of cauda equina syndroma
- S1-3 affected (pelvic and pudendal nn)
- HALLMARK: decreased bladder tone
- other: flaccid, difficult to palpate bladder, difficult to express/ hard to palpate, decreased urinary sphincter tone
Problems associated with neurogenic bladder dysfunction
- incontinence
- urine scalding
- urine stasis
- UTI
- detrusor atony (more and UMN problem)
- pain/discomfort (if bladder stretches +/- UTI but is unable to void, pain receptors continue to be stimulated)
T:F both UMN and LMN bladder can dribble urine (incontinence)
True
- UMN because high internal pressure
- LMN because external bladder pressure and uncontracted outlow tract tone.
- differentiate by palpating bladder
How can neurogenic bladder dysfunction be managed?
- AIM: help bladder empty
- physical management
- pharmacological management (physical managment usually still required)
Physical management - neurogenic bladder dysfunction
- manual expression
- urethral catheterisation (indwelling or intermittent)
- cystostomy tube placement (more long term)
Diazepam - control of bladder function
- ACTION: centrally acting skeletal mm relaxant
- AIM: decrease external urethral sphincter tone
- USE: 1hr before manual expression
Bethanechol - control of bladder function
- ACTION: muscarinic cholinergic agonist (parasympathomimetic)
- AIM: facilitate detrusor mm contractility
- USE: less popular, may be off market, care when high urethral sphincter tone as may increase risk of bladder rupture
Phenoxybenzamine - control of bladder function
- ACTION: alpha-adrenergic antagonist
- AIM: decrease internal urethral sphincter tone
- SIMILAR DRUG: prazosin
Prazosin - control of bladder function
- ACTION: alpha-adrenergic antagonist
- AIM: decrease internal urethral sphincter tone
- SIMILAR DRUG: phenoxybenzamine
Phenylpropanolamine (PPA) - control of bladder function
- ACTION: mixed (alpha and beta) adrenergic agonist
- AIM: increase internal urethral sphincter tone
- USE: treating incontinence rather than urine retention
Of the urethral sphincter, which one holds the most pressure?
internal urethral sphincter
Name 5 drugs used in bladder pharmacological manipulation
- diazepam
- bethanechol
- phenoxybenzamine
- prazosin
- phenylpropanolamine (PPA)
What is a very plantigrade stance in cats characteristic of?
sciatic involvement (lesion)
What is the commonest feline spinal cord neoplasm?
lymphosarcoma
