Neuro Lesion - Lesion 1 Flashcards
Efferent system analogy
Brain is light switch
Nerves are wires
Effector organ is lightbulb
Break in wire = no lightbulb on
Localization in brain
Forebrain
Brainstem
Cerebellum
Vestibular system
Localization of spinal cord
C1-5
C6-t2
T3-L3
L4-S3
Localizing within forebrain
Cerebrum - telencephalon
Thalamus - diencephalon
Localization within brainstem
Mid brain - Mesencephalon
Pons - ventral metencephalon
Medulla - myelencephalon
Localization within cerebellum
Dorsal metencephalon
Localization within vestibular system
Central - cerebellum, myelencephalon
Peripheral - vestibular apparatus and CNVII
Decusation
Idea that everything in the forebrain crosses over or descusates before making its way to the rest of the body
Brainstem and spinal cord are ipsilateral
Central vs PNS lesions
CNS lesions are often mixed motor or sensory deficits
PNS lesions are often sensory or motor
Encephalopathy
Lesions of the brain
Myelopathy
Lesions of spinal cord
Myopathy
Disease of muscle
Not to be confused with myelopathy
ANS
Originates from hypothalamus & ventral diencephalon
Two main divisions - SNS & PsNS
Branches of SNS and PsNS in spinal cord
Symp - branches from c7-L4
Parasympathetic - branches from CN 3,7,9,10 & sacral plexus - minus vagus nerve (doesn’t run in spinal cord)
Horner syndrome
Lack of sympathize innervation to head and head specifically in horses
Lesion location: hypothalamus, cervical myelopathy, cervical thoracic cavity lesion, trauma to neck, middle ear or guttural pouch = pupil dilation
Upper vs lower motor neuron
UMN - cells that arise from forebrain, brainstem & cerebellum
LMN - arise from spinal cord segment
Ventral nerve roots are form by axons of LMN
Nerve roots combine w other nerve roots to form named nerves
Lower are more hyperexcitable /spastic
Assessing lesions upper vs lower
Reflex, tone, atrophy
Reflexes
Reflexes intact - LMN are not affected
Decreased or absent reflex - LMN affected
UMN lesion
Normal to increased reflexes in affected limb
Normal to increased tone in affected limbs
LMN lesion
Decreased to absent reflexes in affected limb
Decreased to absent tone in the affected limbs
One purpose of UMN
Is to decrease spasticity of LMN, without influence of UMN the LMN become more spastic
C1-5 myelopathy
Thoracic limb reflex - normal to increased
Thoracic limb tone - normal to increased
Pelvic limb reflex - normal to increased
Pelvic limb tone - normal to increased
C6-t2 myelopathy
TLF and TLT - decreased to absent
PLR & PLT - normal to increased
T3-l3 myelopathy
TLR - normal
TLT - normal to increased
PLR & PLT - normal to increased
L4-s3 myelopathy
TLR & TLR - normal
PLR & PLT - decreased to absent
Spinal cord segments vs vertebra
Don’t always correlate (C8 spinal cord segments but 7 Cv)
Wherever there’s a nerve root = spinal cord segments
Exits for nerves in cervical regions
Nerve roots exit cranial to the respective vertebra
Exits for nerves in thoracic and lumbar region
Nerve roots exit caudally
**thoracic and cranial lumbar region
Spinal cord segments and vertebra line up with corresponding numbers
Observation and tools fro neurological exam
Behavior, mentation, gait, posture
Traction, plexor, hemostats, light, exam lens, cotton balls
Which nerve is actually visual ?
Cranial nerve 2
Behavior changes
Common behaviors for forebrain lesions
Pacing
Head pressing
Circling
Aggressive
Blind
Obsessive
Incontinent
Distant
Seizures
Source of head pressing
Red nucleus in mid brain = gait generator
Forebrain lesions = inhibitory effects of forebrain
Lack of higher cognition from forebrain = head pressing to wall bc input from red nucleus = go
Source of circling
Circling with occur towards the side of the lesion due to hemineglect = ignoring one side of world /doesn’t exist
Source of mentation
Level of consciousness in patient
3 degrees of abnormal mentation
Dull, depressed,lethargy could be secondary to intercranial or systemic disease
3 degrees of abnormal mentation
Obtunded - abnormal response to stimulus & not fully aroused (vague)
Stuporous - patient only responsive to strong/noxious stim
Comatose - patient has a heart beat, +/- breathing, not responsive to stim
Sources for mentation changes
Obtunded - could be secondary to diffuse forebrain lesion or from brainstem lesion
Stuporous & comatose - secondary to brainstem lesion affecting ARAS
ARAS
Ascending reticular activating system - responsible for keeping patient alert. Located in brainstem
Modified Glasgow coma scale
Specifically for encephalopathy esp when secondary to head trauma
6 point scale, higher score = better prognosis
Categories for modified Glasgow coma scale
Motor activity
Brainstem reflexes
Level of consciousness
Gait abnormalities
Ataxia
Paresis - weakness
Paralysis - absence of movement
Ambulatory vs nonabulatory - 10 unassisted steps
Tetra or quad
Para - pelvic limbs only
Hemi - only one side of the body
Mono - only one limb
3 types of ataxia
Proprioception
Vestibular
Cerebellar ataxia
Proprioceptive ataxia
Spinal or sensory ataxia
Cross limbs, scuff/knuckle
UMN component w proprioceptive ataxia
Vestibular ataxia
Drift towards one side
Head tilt
Cerebellar ataxia
Diametria or hypermetria
Over flexion or over extension of one limb
Lameness vs ataxia
Lameness is predictable with every step - localized pain to limb
Ataxia is irregular - neurological deficits
Posture
Decerebrate
Decerebellate
Head turn/tilt
Torticollis
Opisthotonus
Schiff Sherrington
Risus sardonicus
Spastic
Flaccid
Neck guarded
Kyphosis
Decerebrate
Rigid in all limbs - opisthotonus
Lesion within brainstem (midbrain)
Patient is Stuporous or comatose
Decerebellate
Rigid in thoracic limb, flexed pelvic limbs
Lesion to cerebellum or cerebellar peduncles
Alert to obtunded
Head turn
Secondary to forebrain lesion
Head outside longitudinal axis
Head tilt
Secondary to vestibular disease
Head is out of horizontal axis
Torticollis
Secondary to cervical lesion causing flexion of neck or malformation
Contracture or flexion of cervical muscles
Opisthotonus
Head in Dorso extension, often referred as star gazing
Secondary to intracranial lesion or cranial cervical lesion
Risus sardonicus
Due to lack of inhibition to facial nerve causing contracture of the facial muscles
Secondary to tetanus infection
Schiff Sherrington
Secondary to T3-L3 myelopathy
Thoracic limbs have increased extensor tone (spasticity), pelvic limbs are paretic to plegic
Spasticity
Secondary to UMN lesion (except for Schiff Sherrington)
All 4 limbs are spastic, C1-5 myelopathy is suspected
If pelvic limbs the T3-L3 lesion is suspected
Flaccid
Secondary to LMN lesion
Lesion can be diffuse or at intumescense of spinal cord
Neck guarded
Secondary to cervical pain
Kyphosis
Secondary to thoracolumbar pain, abdominal pain or malformation
C1-5 myelopathy
Respiratory depression
C6-T2 myelopathy
Horner syndrome
Nerve root signature
Absent cutaneous trunci
T3-L3 myelopathy
Schiff Sherrington
Spinal shock
Cutaneous trunci cutoff
L4-S3
Abnormal anal tone
Flaccid tail