Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HNNS > HNS19 Motor System II > Flashcards

HNS19 Motor System II Flashcards

1
Q

Vertebral column

A 
Cervical: 7
Thoracic: 12
Lumbar: 5
Sacral: 5 (fused)
Coccyx: 4 (fused)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Within vertebral column

A
  • Spinal cord covered by Dura, Arachnoid, Pia mater
  • dorsal/ventral **rootlets
    —> dorsal/ventral spinal **    nerve roots
    —> joined to form ***spinal nerves (formed outside of vertebral column)
  • Dorsal root: Sensory (∴ have dorsal root ganglion: pseudounipolar neuron)
  • Ventral root: Motor (carries LMN)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

“Ascent” of spinal cord during development

A

Vertebral column grows faster than spinal cord

Results:

  1. Conus medullaris: terminal end of spinal cord, ~T12/L1 level
  2. Cauda equina: spinal nerve roots form a bundle —> descend and form spinal nerves —> exit at respective levels of spine lower down
  3. Filum terminale (~S2, end of dura): residual extension of spinal cord ***pia mater (modification of pia mater) running from conus to coccyx —> no function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Spinal nerves

A
  • Total 31 pairs (8, 12, 5, 5, 1)

Cervical:

  • 8 pairs
  • C1 exit above C1 vertebra
  • C8 exit between C7, T1 vertebrae

Thoracic, Lumbar:

  • T1 exit below T1 vertebra
  • L5 exit between L5, S1 vertebrae

Below T12, L1:
- Cauda equina of spinal nerve roots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Vertebral level vs Cord segmental level

A

Vertebral level =/ Cord segmental level

∵ spinal cord is much shorter than vertebral column
—> e.g. sacral spinal cord segment will be situated at a higher position within vertebral column (e.g. lumbar vertebral level)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Lumbar puncture

A

CSF withdrawn from Cauda equina region (usually L4/5 vertebral level) (Subarachnoid space)
—> needle will not hit spinal cord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Epidural and Spinal anaesthesia

A

Epidural: outside of Dura (between dura and ligament)

Spinal / Subdural: within Arachnoid mater

—> provide regional anaesthesia at + below the level
—> patient remains conscious!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Spinal cord cross-sectional anatomy

A
  1. Anterior / Posterior horn
    - main nuclei / interneurons of spinal cord
  2. Anterior / Lateral funiculus (funiculus group together —> fasciculus)
    - long fibre tracts
  3. Anterior / Posterior root of spinal nerve
    (4. Spinal nerve)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Grey matter of spinal cord classification

A

Based on nuclei:

  1. Sensory nuclei (Dorsal)
  2. Autonomic function nuclei (Lateral + Medial)
  3. Motor nuclei (Ventral)

Based on laminae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

***White matter of spinal cord

A

Motor and descending (efferent) pathways
1. Pyramidal tracts
—> Anterior corticospinal tract
—> Lateral corticospinal tract

  1. Extrapyramidal tracts
    —> Rubrospinal tract (red nucleus: UL flexor predominant)
    —> Reticulospinal tract (reticular nuclei: medial pontine —> stimulate extensor; lateral medullary —> inhibit extensor)
    —> Olivospinal tract
    —> Vestibulospinal tract (vestibular nuclei: extensor predominant)
    —> Tectospinal tract

Sensory and ascending (afferent) pathways
1. Dorsal column-medial lemniscus pathway
—> Gracile fasciculus
—> Cuneate fasciculus

  1. Spinocerebellar pathway
    —> Anterior spinocerebellar tract
    —> Posterior spinocerebellar tract
    (—> Cuneocerebellar tract (neurons originate from external cuneate nucleus at medulla))
  2. Anterolateral system
    —> Spinothalamic tract (Anterior + Posterior)
    —> Spinoreticular tract
    —> Spinomesencephalic tract
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Functional anatomy of descending and ascending tracts

A

Descending motor tracts
—> activate + modulate LMN within ventral horn
—> LMN then travel within ventral root
—> spinal nerve activate skeletal muscles

Sensory input
—> travel through dorsal root
—> ascend through spinal cord
—> provide feedback

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

***Corticospinal tract (CST)

A
  • > 1 million of mostly myelinated axons
  • mainly from Primary motor cortex (M1 / Area 4)
  • Incompletely decussated at the pyramids of medulla
  1. 75-90% crossed
    —> Lateral corticospinal tract (in Lateral funiculus)
    —> synapse with interneurons + α motor neurons (at ventral horn)
    —> supply ***distal musculature (hand, foot)
  • Lateral CST
    —> Cervical: medial
    —> Sacral: lateral
    —> Clinical significance: disease from outside (compression) / from inside (tumour)
  1. Uncrossed at medulla (may cross eventually to supply contralateral side)
    —> Anterior corticospinal tract (in Anterior funiculus)
    —> modulates **axial + **proximal musculature
  • Uncrossed —> affect ***both side of Brainstem
  • Bilateral **Axial + **Proximal muscle for posture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

***Extrapyramidal tracts

A
  • Originates from Brainstem nuclei (Reticular formation)
  • Under influence of nigrostriatal system, cerebellum, sensory system etc.
  • Modulates ***reflexes, posture, CST activities

Functions:

  1. ***Process information from
    - Higher level special senses (smell, visual, auditory)
    - Spinal cord (peripheral mechanoreceptors)
  2. ***Modulate activities of:
    - Corticobulbar tract to cranial nerve nuclei
    - Corticospinal tract to spinal nerve nuclei
  3. Send descending fibres in addition to the pyramidal tracts (i.e. extrapyramidal tracts)
    - further ***modulate motor activities within spinal cord
    - sometimes even though pyramidal tracts are diseased
    —> can still have some degree of control on LMN
  4. Critical for **postural adjustments + control of **axial + ***proximal musculature

Examples:

  • Rubrospinal tract
  • Tectospinal tract
  • Pontine (medial) reticulospinal tract
  • Medullary (lateral) reticulospinal tract
  • Lateral vestibulospinal tract
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Evolution of CNS

A

Lower animals:

  • no distinct brain
  • non-bilateral system
  • net-like / radial system / ventral “spinal cord”

Higher animals:

  • enlarged brain
  • bilateral system
  • dorsally placed spinal cord
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Pyramidal and Extrapyramidal system

A

More “advanced” motor system

  • Lateral descending system: Lateral CST + Rubrospinal tract (extrapyramidal)
  • Crossed fibres (unknown reason)
  • Interact with anterior horn cells for ***Distal muscles —> more complex, fine, “advanced” movements

More “primitive” motor system

  • Ventral descending system —> Other extrapyramidal tracts
  • Mostly uncrossed fibres —> ***Axial muscle, posture, reflex
  • Interact with anterior horn cells for ***Proximal muscles —> more “basic” and for gross movement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Rubrospinal tract

A
  • From magnocellular neurons of ***Red nucleus in midbrain
  • ***Crossed fibres
  • in ***Lateral descending system
  • Control ***flexor muscles
  • Significance in human unclear
17
Q

Tectospinal tract

A
  • From ***Superior colliculus (Tectum of midbrain): Vision
  • ***Crossed fibres to contralateral cervical segments
  • ***Reflex movement in response to Visual stimuli (auditory?)
18
Q

Reticulospinal tract

A
  • From less clearly defined nuclei within ***Reticular formation (brainstem)
  • ***Uncrossed
  • ***Influence voluntary movement
  • Medial (Pontine) RST —> Excites ***extensors
  • Lateral (Medullary) RST —> Inhibits ***extensors
19
Q

Lateral Vestibulospinal tract

A
  • From ***Lateral Vestibular nucleus (medulla)
  • Input from Cerebellum and Vestibular apparatus
  • ***Uncrossed
  • Innervates ***ipsilateral trunk muscle (Extensor)
  • Maintain ***posture and balance (Labyrinthine Righting Reflex: integrates head position balance signal with truncal muscle)
20
Q

Summary of descending system

A

Lateral CST (crossed): executes conscious voluntary movement (distal musculature)

Ventral CST (uncrossed): controls balance + posture (axial + proximal musculature)

Extrapyramidal tracts serve ***additional roles:

  • provide background condition and “readiness” for CST to act
  • execute “unconscious” response to external stimuli (brainstem integration of sensory input) and sensory feedback from the body
  • maintains a balance between flexion and extension motor activities as well as posture and balance

—> Diseases at different levels —> different clinical pictures + recovery potential

21
Q

Clinical relevance of Extrapyramidal tracts

A

In unconscious patients, disease at different levels
—> different extents of loss of descending motor influence
—> different postures

  1. Decorticate (cortex cut off) posture:
    Lesion above red nucleus
    —> Rubrospinal tract intact
    —> UL flexion remains
  2. Decerebrate (cerebrum cut off) posture:
    Lesion between Red nucleus (midbrain) and Vestibular nucleus (medulla) (More extensive involvement of brainstem)
    —> Rubrospinal tract cut off
    —> Un-opposed extensor activities of Reticular and Vestibular nuclei
    —> UL extension (worse prognosis)
  3. Post-stroke recovery:
    E.g. Internal capsule infarction
  • Lateral CST gone
    —> poor recovery of fine movement
  • Extrapyramidal tracts intact (∵ infarction above brainstem)
    —> some recovery of proximal muscles (trunk muscles, thigh) and gross movement (walking)
    —> imbalance of flexion and extension influences to LMN
    —> results in abnormal limb posturing (e.g. UL flexed and LL extended)
22
Q

Disease of spine

A

Etiology:

  1. Trauma
    - spinal fracture
    - spinal epidural haematoma
    - penetrating injury
  2. Degeneration
    - spondylosis
  3. Tumour
    - spinal tumour
  4. Bleeding
    - Inflammation —> multiple sclerosis
  5. Loss of blood supply
  6. Congenital

Can affect:

  • Spinal cord
  • Cauda equina
  • Individual nerve roots
  • Combination of above
23
Q

***UMN lesion vs LMN lesion

A

UMN lesion:

  1. Location
    - CNS only
  2. Structures involved
    - Cortex
    - CST / CBT
  3. Distribution
    - Groups of muscle
  4. Paralysis
    - **Spastic paralysis (esp. anti-gravity muscle)
    - **    Clasp-knife rigidity / spasticity
  5. Reflexes
    - ***Hyperactive
  6. Muscle bulk
    - ***Mild disuse atrophy
  7. Classical signs
    - ***Babinski’s response / Positive Babinski sign
    - Clonus
  8. Examples
    - Stroke, head injury, spinal cord injury (e.g. CTS)

LMN lesion:

  1. Location
    - PNS + CNS as well (Anterior horn cells: count as LMN but within spinal cord: CNS)
  2. Structures involved
    - α-motor neuron
    - Motor fibres in spinal / cranial nerves
  3. Distribution
    - Segmental
  4. Paralysis
    - ***Flaccid paralysis
  5. Reflexes
    - ***Decreased / Absent
  6. Muscle bulk
    - ***Pronounced atrophy
  7. Classical sign
    - None
  8. Examples
    - Poliomyelitis affecting anterior horn cells
    - nerve roots / spinal nerve / peripheral nerves (PNS)
24
Q

Myelopathy vs Radiculopathy

A 
Myelopathy
- Spinal cord
E.g. Central IV disc herniation
- LMN lesion at that level (anterior horn cells)
- UMN lesion below
Radiculopathy
- Nerve root
E.g. Lateral IV disc herniation
- LMN lesion only
- Cord itself unaffected
25
Q

Spinal cord lesion

A
  • At / above conus medullaris
  • LMN lesion at that level
  • UMN lesion below
  • Lateral CST gone
    —> no voluntary movement
  • Extrapyramidal tracts also gone
    —> no descending modulation
    —> hyperactive reflex arc (late)
  • Overall recovery poor: may not be even able to walk (worse than internal capsule infarct)
26
Q

Levels of injury and extent of paralysis

A

C4 injury
—> Brachial plexus involved (C5-T1 spinal nerves to UL)
—> Quadriplegia

C6 injury
—> C5 of brachial plexus may be spared
—> still Quadriplegia (but some areas e.g. shoulders may be spared)

T6 / L1 injury
—> brachial plexus spared
—> Paraplegia

27
Q

Hemitransection - Brown-Sequard syndrome

A
  • **Ipsilateral motor symptoms
    1. LMN lesion at the level
  • Flaccid paralysis
    2. UMN lesion at level below
  • Spastic paralysis
  • pyramidal weakness

Ipsilateral impaired joint position, sense and accurate touch localisation

Contralateral impaired pain and temperature sensation

28
Q

Patterns of Radiculopathy

A
  • Clinical assessment can locate / pinpoint the lesion
  • Disease of specific nerve root —> specific pain distribution, weakness, sensory loss + reflex loss
  • Peripheral nerves (distal to spine, several spinal nerves joined together) =/ Spinal nerves
  • Peripheral nerve lesions —> can involve several spinal nerve roots
29
Q

Conus medullaris and Cauda equina lesions

A

Cord: UMN lesion (except anterior horn cells)

Conus medullaris: Mixed LMN and UMN lesions

Cauda equina: LMN lesion

30
Q

Cauda equina syndrome

A
  • LMN lesions
  • affect Lumbosacral nerves
  • acute / subacute onset

Symptoms:
1. LL weakness

  1. Sensory loss
    - e.g. Saddle anaesthesia (+/- sensory loss in one of both lower limbs)
  2. Sphincter dysfunction (bladder, urethral sphincter, anal sphincter supplied by complex system of sensorimotor nerves for emptying and maintaining continence)
    —> Bladder: painless acute urinary retention
    —> Bowel: lax anal tone on PR exam, but constipation
    —> BOTH irreversible unless very early intervention!
  3. Sexual dysfunction
  4. Back pain
31
Q

Case study 1

  • Complaint: Weak right arm
  • RLL weak
  • Speech deficit
  • Facial weakness
A

Left cerebral hemisphere stroke

32
Q

Case study 2

  • Complaint: Weak right arm
  • RLL weak
  • Right limbs hyperactive reflexes
  • Left limbs normal motor function
  • Cranial nerves normal
A

Tumour affecting mainly right side of cervical spinal cord

Cranial nerves normal —> Brain normal

33
Q

Case study 3

  • Complaint: Weak right arm
  • Weakness and numbness in proximal UL
  • Distal UL normal
A

Problem mainly at proximal UL
Compatible with C5/6 degeneration on MRI scan
—> rmb myotome
—> more proximal joint innervated by higher centres in spinal cord (C5-6)

34
Q

Case study 4

  • Complaint: Weak right arm
  • Weakness in wrist extension
  • Wrist flexion ok
  • Proximal UL normal
A

Problem mainly at distal UL
NOT compatible with C5/6 degeneration on MRI scan
—> rmb myotome
—> more distal joint innervated by lower centres in spinal cord (C6-T1)

35
Q

Summary

A

Spinal cord: final common pathway for limb and trunk motor function

Lateral CST: fine + complex movement

Extrapyramidal tracts: trunk + proximal movement

UMN vs LMN lesions: clinically distinct

Myelopathy vs Radiculopathy

Spinal cord lesions and Cauda equina syndromes have different clinical presentations

Clinical relevance:
Apply neuroanatomy to:
1. Locate the disease
- brain / spine
- where
- which side 
2. Assess severity and urgency
3. Order the right investigation
4. Interpret investigation
- culprit / incidental findings
5. Decide on treatment

HNNS (58 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions