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Flashcards in Pathways Deck (98)
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UMN lesions

-hemiplegia: contralateral if lesion in cortex before deccusation; ipsilateral if lesion in spinal after deccustion
-spacitity (increase tone)
-upward going plantar reflex (babinski sign)
-no/not as much atrophy
-no fasiculations


LMN lesions
-6 signs

-ipsilateral weakness because after decussation **
-usually ind. muscles not grp
-flaccidity (decrease tone) or normal
**EXCEPT Trochlear (CN1V) nuclei because they cross at nucleus level! (but if lesion at the CN4 nerve, will be ipsilateral



-1ry neuron in motor pathway
-in CNS
-synapse to LMN



-cell body in brainstem (CNs) /spinal cord (ventral horns)
-axons in PNS
-synapse to muscles
-LMN pathway = "final common pathway"
-IPSILATERAL innervation


Describe the corticospinal tract pathway

-for skilled limb movements
-1ry neuron: 1ry motor cortex
> corona radiata
> post. limb internal capsule > cerebral peduncles > CST in ant pons > pyramids
> deccusate at spinomedullary junction (pyramids)
> descend in lateral corticospinal tract (LCST) in lateral column of spinal cord
> synapse 2ry neuron: cervical and lumbosacral enlargements
> distal limbs


Which side is affected if CNs are lesioned?

IPSI b/c LMN after deccusation


Which side is affected if CN nuceli are lesioned?

IPSI except for Trochlear nuclei = contralateral
CST tract


Describe Corticobulbar Tract

-cortex > brainstem
-motor path for cranial nerves (5,7,9,10,11,12)
-same as CST except through genu of internal capsule
(although 7,11,12 more complicated)


Which CN does CBTract not innervate?

-sensory CNs
-eye motors : 3,4,6


Which CNs are bilaterally innervated? what is the implication?

-CN 5,9,10
-redundancy - if lesioned on one side in CBTract (UMN), still ok!
-but lesion at nerve level (LMN) (after CBT > nuclei) > ipsilateral effects


Describe the UMN, LMN lesions involved with the Mastication Nucleus

-CNV3: chewing, jaw movements
-UMN lesion: bilaterally innervated > function preserved
-LMN lesion: IPSIlateral defecit:
opening mouth, chewing diff due to paresis/paralysis jaw drop to lesioned side, atrophy of muscles > asymmetrical face


Describe the UMN, LMN lesions involved with the Nucleus Ambiguus

-CN 9, 10: larynx (10), pharynx, speech, swallowing
-UMN lesion: bilaterally inn > func ok
-LMN lesion: IPSIlateral def
gag reflex loss
hoarse voice
sagging palate


Describe the UMN, LMN lesions involved with Hypoglossal nucleus

-CN 12: tongue movements
-UMN lesion: before decussation > no input to CONTRALateral tongue > tongue protrudes to contralateral side of cortex and paresis/paralysis
-LMN lesion: after decussatin > IPSIlateral to lesion
tongue protrudes
fasciculations then atrophy
*Tongue always goes to side of lesion


Describe the UMN, LMN lesions involved with Accessory nucleus

-CN 11: sterno, trap : shoulder shrug and head turn
-UMN lesion: IPSI for sterno (difficulty turning head to opposite side), CONTRA for trap weakness in should shrug (because UMN of trap crosses before synapsing in nuclei)

-LMN lesion: ipsilateral both muscles


Describe the UMN, LMN lesions involved with Facial nucleus

-CN 7 - facial expression, taste ant 2/3 tongue, all glands (except parotid)
-Facial Nucleus is different because it has 2 subnuclei controlled by different UMNs to forehead and face
-UMN lesion: rostal subnuclei (forehead) is bilaterally inn; caudal (face) is unilateral. Thus, lesion will only affect CONTRA lower face
-LMN lesion: IPSI face and forehead affected - paralysis


Describe STT

-Spinothalamic tract
-for pain, T, crude touch
1: periphery > DRG into dorsal roots then synapse
2: in dorsal horn > DECUSSATE > CONTRA STT (ventral-lateral white matter of cord) > travels in Spinal Lemniscus in brain stem > synapse at VP thalamus
3: thalamus > postcentral gyrus


Describe DCML

-Dorsal column - medial lemniscus
-for fine touch, vibration, conscious proprioception
1: periphery > DRG > dorsal horn > ascend via FASCICULUS GRACILIS (medial, leg) /FASCICULUS CUNEATUS (lateral, arm) > synapse in NUCLEUS GRACILIS/CUNEATUS
2: nuclei > deccusate @ medial lemniscus in brain stem > synapse in VP thalamus
3: thalamus > postcentral gyrus


What are the touch submodalities

nociception (tissue damage)
Temp (T)
crude touch
fine touch


Name the 5 sensory modalities and where in cortex they are perceived

1.smell - 1ry olfctory cortex - uncus, amygdala - 1ry visual cortex - alone calcarine fissure in occipital lobe
3.hearing - 1ary auditory cortex - transverse temporal gyri on superior temporal gyrus
4.touch - 1ry somatosensory cortex - postcentral gurus
5.taste - 1ry gustatory cortex - inf. postcentral gyrus


Describe Somatosensory pathway neurons

3 neurons:
1. pseudounipolar located in DRG or Trigeminal gangion (face)
2. in dorsal horn of spinal cord or brain stem
-CROSSES and goes to CONTRA VP thalamus (location of deccusation depends on tract)
3. thalamus to appropriate cortex


Describe clinical expression of an ventral intramedullary lesion
ex: tumour compression from within cord

-affect STT
-loss of pain, T at level of lesion, then appears to DESCEND if lesions grows
(distal dermatome further out)


Describe clinical expression of an ventral extramedullary lesion
ex: meninegoma, disc compression from outside cord

-affect STT
-loss of pain, T at level of lesion then appears to ASCEND
(proximl dermatomes more central on cord)


where is the border between running through fasciculus graciclis vs cuneatus

above T6: ascend through cuneatus (no FG)


Describe clinical expression of midline dorsal compression

Loss of conscious proprioception, fine touch, vibration sensation legs moving up


What is different about somatosensation of the face?

1ry neuron goes via CNV to trigeminal ganglion not DRG > synpase then deccusate > VP thalamus, synapse > cortex


Sensory Trigeminal Nuclei (3)

-posterior brainstem
1. Mesencephalic Nucleus (midbrain)
-1ry sensory neurons
-proprioception of jaw; reflex arc of masticator muscles
2. Chief Sensory Nucleus (pons)
-2ry neurons
-touch, vibration (like dorsal column for body)
3. Spinal Trigeminal Nucleus (medulla)
-2ry neurons
-pain, T, crude touch (like STT)
-fibres enter at pons, descend to medulla to reach nucleus, deccusate and joins SPINAL LEMNISCUS tract to go to thalamus with body signals


What is suspended sensory loss?

-loss of sensation at level of lesion but above and below is OK


What is dissociated sensory loss?

-one side loss STT modalities, while the other side loss DCML mods
ex: spinal cord unilateral lesion - affect contralateral STT because cross and can't ascend and ipsilatearl DCML because can't ascend. deficit below level of lesion


What are muscle spindles? How do they work

-stretch receptors for muscle - length
-located along striate muscles
-fire on 1a afferent axon
-when muscle contract, spindle get sggy so need intrfusal muscle to contrct to maintain spindle
< alpha-gamma co-activtion: ALPHA to contract muscle, GAMMA to contract intrafusal muscle of spindle


What are golgi tendon organs?

-receptor for muscle tension/contraction
-located along tendons
-fire on 1b afferent axons