Basic Principles Of Locatization Flashcards
What are the diff functions of diff lobes?
Frontal lobe = executive funcitoning
Parietal lobe = awareness of somatic sensation, processing somatic sensation, proprioception
Temporal lobe = auditory
Occipital lobe = visual cortex
What is the pathway of the UMN?
Primary motor cortex (BA4) -> subcortical (corona radiata) & internal capsule & basal ganglia -> brainstem until spinal cord -> above the anterior horn cell
What is the pathway of LMN?
Below anterior horn cell -> nerve root/peripheral nerves -> NM junction & muscles
What aer the 2 ascending pathways seen in sensory exma?
Spinothalamic = light touch, temperature, and pain
DCT = joint position, vibratory & tactile discrimination
What part of the brain is responsible for Gait & coordination?
Vestibulocerebellum
Spinocerebellum = station, walking, and tandem gait
Cerebrocerebellum = rapid alternatine movements, finger to nose, heel to shin, rebound check reflex, speech and nystagmus
What are the basic principles of localization?
- Accurately defining signs & sx
- Pattern recognitiion
- Levels of confidence
- Longitudinal & transverse localization
- Know ur decussations
Where is the level of decussation in the CST & how does it present if lesions are below medulla and above medulla?
Point: pyramidal decussation in the medulla
Lesion above medulla = CL weakness
Lesion below medulla = IL weakness
*remember ascending path neto
What is the point of decussation of the DC pathway and presenting signs of lesions above and below medulla?
Pt of decussation: ascends & crosses in the lower end of the medulla
Lesions below medulla: IL sensory loss
Lesions above medulla: CL sensory loss
What is the pathway of spinothalamic tract ? lesions above and below spinal level will cause what?
Enters posterior spinal cord -> ascends to spinal nerve root segments -> crosses in ventral white commissue -> ascends to sensory cortex
Lesions at given spinal level: CL pain
Lesion below 1-2 spinal levels = temperature loss
What aer the signs of LMN lesion?
Decreased tone (flaccid)
Decreased reflexes
- Babinski sign
+ Atrophy
+ Fasciculations
UMN lesion
+ Babinski sign
INC tone (spastic)
INC reflexes
No atrophy
No fasciculations
What are the diff betw Central & Peripheral facial weaknessx?
Central facial palsy
- spares the forehead
- seen when a lesion interrupts the Corticobulbar fibers
- CL to the lesion
Peripheral facial palsy
- both forehead and lower face are weak
- lesions affect peripheral CN VII or its nucleus
- IL to the lesion
What is the cause of tongue weakness?
CN XII nucleus => CL innervated
Tongue deviattes towards the side of the weakness
What are the patterns of motor loss?
Cortex, Corona radiata, internal capsule = CL hemiparesis, Central faciall palsy
Brain stem = CL hemiparesis & IL CN deficits, Quadriparesis & bilateral CN deficits
Spinal cord = Quadriparesis or Parapersis
Anterior horn cell = localized or generalized
Nerve root = root distribution
Nerve plexus = >1 nerve root
Polyneuropathy = feet & legs, hands & arms
Mononeuropathy = single peripheral nerve
NMJ = fatigable pattern on weakness on repeated testing
Muscle = weakness involving proximal muscles > distal muscles
What happens in the CN system at the spinal cord level?
Separation of modalities as it reaches the spinal cord
-> Posterior column ascends IL -> up to medulla
-> Spinothalamic ascends in the CL spinal cord -> decussates at the level of its entry
What happens in the CN system at the CN V?
Central sensory nucleus of CN V -> extends within the brainstem from the pons to the spinal cord
Central lesions -> IL facial numbness
What are the patterns of sensory loss?
Peripheral nerve
Sensory loss Single nerves = Nerve distribution All PNS =. Glove and stocking Spinal nerve roots = Dermatomal Cauda equina. =. Both legs & perineum
What is the presentation of complete transection, hemitransection, central cord distribution in diff lvels of the spinal cord?
Complete transection
- sensory loss occurs everything below the level of the lesion
Hemitransection
- Brown-Sequard syndrome: lesion on the spinal cord characterized by weakness or paralysis in one side of the body & loss of sensation in the opposite side
Central cord distrbution
- loss of pain/temp in band-like fashion over segments occupied by the lesion
- “cape-like” distribution
- commonly seen in Syringomyelia
What are the sensory loss in complete transection, hemisection, central cord?
complete transection
-> all below the level of the lesion
Hemisection
-> IL: joint position, vibration, light touch
-> CL: temp & pain
Central cord
-> loss of pain/temp in band-like fashion over segments occupied by lesion
What aer the diff patterns of sensory loss in the brain?
Brainstem
-> Loss of IL face of sensation
-> CL limb sensation
Thalamus
-> loss of all CL modalities, usually spares trunk
Parietal lobe
-> loss of CL modalities
-> numbness, agnosia, loss of 2-point discrimination, astereognosis, agraphestesia, hemisensory neglect
What aer the diff patterns of sensory loss in teh visual system?
Prechiasmal = Monocular sensory loss
CHiasmal = Bitemporal hemiapnopsia
Optic tract/LGB/Optic radiation = CL homonymous hemianopsia
Temporal lobe = superior CL homonymous hemianopsia
Parietal lobe = Inferior CL homonympus hemianopsia
Occipital cortex = CL homonymous with macular sparing
What are the 2 structures involved in horizontal gaze?
Frontal eye field (supratentorial)
Paramedian pontine reticular formation (pons)
In preferential gaze, what does a cortical lesion & brainstem lesion look like?
Cortical lesion
-> preferential gaze towards teh lesions and away from the weakness
Brainstem lesion
-> preferential gaze away from the lesion & towards the weakness
What is the term known to describe unequal pupils?
Anisocoria
What are the 2 most common pupillary problems?
Anisocoria
Decreased pupil contriction to light
How do u know in anisocoria if the large puil or small pupil is the abnormal one?
Small pupil = abnormal if anisocoria is greater in the dark than in the light
Larger pupil = abnormal if anisocoria > in light than in the dark
What are the diff presentation of cerebellar symptoms?
Lateral lobes
->limb ataxia and hypotonia
Flocculonodula lobe
-> disturbed equilibrium: truncal ataxia,drunken gait, titubation of head and trunk
Anterior lobe
-> gait ataxia, inability ot do tandem walking
What is the presentation of aphasia in cerebral cortex?
Frontal lobe = expressive dysphasia/aphasia (dominant)
Parietal lobe - receptive dysphasia/aphasia (dominant)
Temporal lobe = receptive dysphasia/aphasia (dominant)
Occipital lobe = CL homonymous hemianopia
What are the steps on localization?
- Get a good detailed history
- Perform PE and Neuro exam
- List down abn findings on neuro exam & correl each deficit with possible tracts or pathways involved
- Find intersection
- Localize
