Neuro: 3.06 - Localization Of Motor Disease

Front 1

What is the least number of neurons it takes to transmit an impulse from motor cortex to muscle fiber? Which are

Back 1

Two - UMN traveling via LCST and an LMN (α motor neuron) that exits spinal cord

Front 2

What controls contralateral muscle movement?

Back 2

Lateral Corticospinal Tract

Front 3

Where can you localize a muscle weakness to?

Back 3

- Lesion in cortex
- Lesion in brainstem
- Lesion in spinal cord

Front 4

What are some signs of a lesion to the lateral corticospinal tract in the cortex?

Back 4

- Contralateral weakness and aphasia (inability to understand or express language)
- Apraxia (inability to do a learned movement, e.g., brushing teeth)
- Neglect (ignore stimuli on one side of body)

Front 5

What are some signs of a lesion to the lateral corticospinal tract in the brainstem?

Back 5

Ipsilateral CN findings and contralateral body weakness

Front 6

What are some signs of a lesion to the lateral corticospinal tract in the spinal cord?

Back 6

Weakness below a certain spinal cord level

Front 7

What is a Hemicord lesion? Name?

Back 7

- Weakness on one side and sensory loss on other
- Begins at a certain spinal cord level and below
- AKA: Brown-Sequard Syndrome

Front 8

What is the function of the Corticobulbar Tract?

Back 8

Controls contralateral facial movement

Front 9

If you lesion the UMN of the corticobulbar tract, what are the symptoms?

Back 9

- Contralateral weakness of lower face (mouth droop; flat nasolabial fold)
- Intact forehead wrinkle

Front 10

If you lesion the LMN of the corticobulbar tract, what are the symptoms?

Back 10

- CN VII lesion
- Ipsilateral upper and lower facial weakness
- Bell's Palsy

Front 11

What is the function of the Reticulospinal tracts?

Back 11

- Unconscious motor control
- Give muscles "tone"
- Inhibits the LMN, which is tonically active

Front 12

Which muscles/LMNs have more tone?

Back 12

- Antigravity muscles/LMNs - muscles that help you walk/move against gravity
- E.g., quadriceps, tibialis anterior, biceps, etc.
- Arms - flexors
- Legs - extensors

Front 13

If you increase activity of the UMN, what happens to the LMN and muscle?

Back 13

- Inhibit LMN
- Muscle relaxes

Front 14

If you decrease activity of the UMN, what happens to the LMN and muscle?

Back 14

- Lose inhibition of LMN
- Muscle contracts

Front 15

What happens if there is a lesion to the Reticulospinal Tract?

Back 15

- Acute lesion (e.g., acute stroke) - contralateral hypotonia (system is in shock so no tone)
- Chronic lesion (e.g., chronic stroke) - contralateral hypertonia (because decreased inhibition of LMN)

Front 16

What causes hyperreflexia?

Back 16

UMN to the α-MN is lesioned

Front 17

What causes hyporeflexia?

Back 17

LMN is lesioned; or lesion of afferent or efferent limb

Front 18

What are the deep tendon reflexes?

Back 18

- Biceps
- Brachioradialis
- Triceps
- Pateller
- Achilles

Front 19

What nerve is involved in the biceps reflex? At what level?

Back 19

- Musculocutaneous N.
- C5

Front 20

What nerve is involved in the brachioradialis reflex? At what level?

Back 20

- Radial n.
- C6

Front 21

What nerve is involved in the triceps reflex? At what level?

Back 21

- Radial n.
- C7

Front 22

What nerve is involved in the Patellar reflex? At what level?

Back 22

- Femoral n.
- L2/3

Front 23

What nerve is involved in the Achilles reflex? At what level?

Back 23

- Sciatic n.
- S1

Front 24

How does an UMN lesion affect:
- Tone
- Reflexes
- Atrophy
- Fasciculations
- Weakness

Back 24

- Spasticity (high tone)
- Hyperreflexia
- No/mild atrophy
- No fasciculations
- Spastic paresis (weak, slow movement)

Front 25

How does an LMN lesion affect:
- Tone
- Reflexes
- Atrophy
- Fasciculations
- Weakness

Back 25

- Decreased tone
- Hyporeflexia
- Significant atrophy
- Fasciculations
- Flaccid paresis

Front 26

What are the symptoms of an anterior horn cell lesion?

Back 26

* LMN lesion: aka α-MN
- Flaccid paralysis
- Severe atrophy
- Fasciculations - spontaneous firing of motor neuron (twitching under skin, not painful)
- Cramping - firing of multiple motor neurons or entire muscle, entire muscle contracts (painful)
- Loss of reflexes

Front 27

What are some examples of Anterior Horn Cell Lesion?

Back 27

ALS, polio

Front 28

What are the symptoms of a root lesion?

Back 28

- Shooting pain in a root dermatomal distribution
- Loss of reflexes that correspond to root
- Little or no weakness and atrophy (would need to have all roots lesioned)

Front 29

What can cause a root lesion?

Back 29

Disc herniation

Front 30

What are the symptoms of a plexus lesion?

Back 30

- Multiple muscles in arm or leg involved
- Loss of reflexes (depends on localization)
- Sensory loss depending on localization
- Usually painful

Front 31

What are some examples of Plexus lesions? What do they affect?

Back 31

- Erb's Palsy - upper trunk of brachial plexus
- Klumpke's Palsy - lower trunk of brachial plexus
- Pancoast tumor - lower trunk of brachial plexus
- Diabetic lumbosacral plexopathy - lumbosacral plexus

Front 32

What are the characteristics of Erb's Palsy?

Back 32

- Arm held internally rotated, extended at elbow, flexed at side of body
- "Waiter's tip" pose
- Can fully move hand
- Can be caused in birthing process when neck is stretched
* Due to upper trunk of brachial plexus lesion *

Front 33

What are the characteristics of Klumpke's Palsy?

Back 33

- Opposite of Erb's
- Weakness in fingers, but no difficulty moving across shoulder and elbow
- Can be caused when hanging from tree
* Lesion of lower trunk of brachial plexus *

Front 34

What are the symptoms of a Pancoast tumor?

Back 34

- Tumor of apical part of lung (if your patient is a smoker and losing weight with these symptoms, worry about this)
- Lower trunk of brachial plexus lesion
- Similar symptoms as Klumke's (weakness in fingers but not across shoulder or elbow)

Front 35

What happens in a peripheral nerve lesion?

Back 35

- Muscles innervated by that nerve show profound atrophy
- Dense sensory loss
- Reflexes may be lost if muscle tested is innervated by lesioned nerve

Front 36

What is an example of a peripheral nerve lesion?

Back 36

Carpal Tunnel Syndrome

Front 37

What is compressed in Carpal Tunnel Syndrome? Cause?

Back 37

- Median nerve compression at wrist (neuropathy)
- Caused by overuse of finger flexors from repetitive tasks cause these muscles to hypertrophy
- Hypertrophied muscles and median nerve pass through tunnel, which is a confined space
- Muscles compress nerve as they grow

Front 38

What are the symptoms of Carpal Tunnel Syndrome?

Back 38

- Pain and tingling in median region of hand (thumb to lateral half of ring finger) - symptoms in thumb to middle finger common
- Especially bothersome at night because hand gets accidentally hyperflexed at wrist and patient wakes up and shakes out hand
- If chronic, can cause atrophy of median innervated hand muscles causing loss of bulk and thenar eminence

Front 39

What happens in a NMJ defect?

Back 39

- Fatigable weakness (worse later in day and after repetitive movements, improved after rest)
- Affects muscles that are constantly working (levator palpebrae, extraocular muscles, neck extensors, core muscles, swallowing muscles, intercostals/diaphragm)

Front 40

Symptoms of NMJ defect?

Back 40

- Occur later in the day and after repetitive movement
- Ptosis
- Diplopia (double vision)
- Dropped head
- Difficulty rising from chair, stairs
- Dysphagia (difficulty swallowing)
- Difficulty breathing (intercostals/diaphragm)

- No sensory loss
- Reflexes normal
- No muscle atrophy

Front 41

What are some causes of NMJ defects?

Back 41

- Myasthenia
- Lambert-Eaton myasthenic syndrome
- Botulism

Front 42

What are the symptoms of a muscle lesion?

Back 42

- Weakness in certain muscle groups
- Normal sensation
- Intact reflexes (unless there is profound muscle atrophy)

Front 43

What are some examples of muscle lesions?

Back 43

- Myositis (inflammation and degeneration)
- Muscular dystrophies (Duchenne's) - defect in enzymatic function or structural defects

Front 44

Case: 31 yo F developed sudden R f/a/l weakness 2 weeks ago
- Mild slurred speech 
- Falling
- No sensory loss, headache
- Exam: Vitals: normal
- Normal language; no neglect
- ↓R nasolabial fold
- ↑tone in R arm; R finger taps slow
- 4+/5 strength in R arm/leg
- Reflexes 3+ on R arm/leg
- Spastic gait

Localize??

Back 44

* L posterior limb of internal capsule
- L LCST/corticobulbar at internal capsule or L pons
- Stroke or MS

- No cortical signs & leg involved (so has to be 2 vascular territories)
- No spinal level --> not cord
- R pure motor problem with UMN signs --> LCST on L lesioned
- R UMN facial weakness --> L corticobulbar tract (before pons)

Front 45

- Case: 62 yo F with DM, HTN develops sudden aphasia and R face/arm weakness
- Exam: Speech is halting, effortful, agrammatic, few words
- L gaze preference
- R lower facial weakness
- R arm drift; leg normal
- R arm/face sensory deficit
- Ref lexes: absent in RUE; normal elsewhere; Babinski absent on L and mute on R

Localize (neural axis & vascular distribution)??

Back 45

L frontal cortex and parietal cortex
(MCA distribution)
- Stroke

- Broca’s aphasia --> L frontal cortexcortical sign
- L gaze preference --> R FEF working --> L FEF lesioned --> cortical sign
- R lower face & arm --> L frontal cortex
- R arm/face sensory deficit --> L parietal cortex
- Reflexes ↓ b/c acute