Neurological Weakness Primer Flashcards
What is weakness and what are some ways to differentiate types?
Loss of skeletal muscle strength
- May be a few or many muscles anywhere in the body
- May develop suddenly or gradually
- May be symmetrical or asymmetrical/bilateral or unilateral
What are the overall causes of neurological weakness?
- Damage in the motor system
- Cortical neurons (UMN)
- Pyramidal tracts (corticobulbar + corticospinal)
- Spinal motor neurons (LMN)
- Nerve roots
- Plexus (cervical and lumbosacral)
- Nerves
- NMJ
- Muscles - Dysfunction in the motor system
- Hemiplegic migraine
- Todd’s paresis (post-ictal)
- Functional limb weakness
What does the corticobulbar tract supply?
Head
What does the corticospinal tract/pyramidal tract do?
Arm/hand, trunk, leg/foot
Decussates in the medulla
- Anterior corticospinal tract
- Lateral corticospinal tract
What are the 5 patterns of muscular weakness?
- UMN (corticospinal and corticobulbar)
- LMN (spinal motor neurons/roots/plexus/nerves)
- NMJ
- Muscle
- Functional
History: what are some associated symptoms you should ask about?
Headache
Numbness/tingling
Decreased consciousness
Sphincter problems
Neck/back pain
Dysphasia/dysarthria/dysphagia
Systemic: fever, rash, vomiting
Visual field defect
What are causes of hyperacute (<1min) muscle weakness?
Vascular: stroke
Trauma: spinal cord compression
What are causes of acute (<24hr) muscle weakness?
Inflammation: myelitis, vasculitis
Infection: cerebral abscess
Trauma: subdural haematoma
What are causes of subacute (days-weeks) muscle weakness?
Inflammation: GBS, MS demyelination, myositis
Neoplasia: brain/spine/nerve
Metabolic: myelopathy, neuropathy
What are causes of chronic (months-yrs) muscle weakness?
Genetic:
- Hereditary neuropathy
- Hereditary myopathy
Neurodegeneration:
- MND
- Inclusion body myositis
What PMHx should you ask?
Vascular RFs
Metabolic conditions
Cancer
Injury
Irradiation
Surgeries
What drug history should you ask?
Steroids- myopathy
Chemo
Toxic drugs
Diabetic drugs
Vaccinations- GBS
What is the characteristic pattern of UMN weakness?
No muscle wasting or fasciculations
Increased tone
Decreased power in pyramidal pattern (weakness of arm extensors and leg flexors)
Increased reflexes
Plantar response increased
What is the characteristic pattern of LMN weakness?
Muscle wasting + fasciculations
N/Decreased tone
Decreased power
Decreased reflexes
N/mute plantar response
How is muscle power assessed using the MRC scale?
0 no muscle contraction visible
1 flicker or trace of contraction but no movement
2 active joint movement when effect of gravity is eliminated
3 active movement against gravity
4 active movement against gravity and resistance but weaker than normal
5 normal power`
Monoplegia is
weakness of 1 limb
A brainstem lesion does what pattern of weakness
Face and opposite side of body
Paresis vs plegia
Paresis is weakness
Plegia is paralysis
What are cortical signs that happen with hemiparesis?
Sensory deficit
Hemianopia
Gaze paresis
Dysphasia
Neglect
What is pure hemimotor syndrome?
When you have a subcortical stroke, you will have pure motor hemiparesis/hemiplegia.
Usually from a lacunar infarct in the internal capsule
May have:
+/- dysarthira
+/- ataxia
No sensory loss
No cortical signs
What could cause monoplegia of an arm?
(unilateral arm weakness)
Infarct of a small art of cortex
Cervical cord
Where would a lesion causing hemiplegia that spares the face be?
Small part of corex or the pyramidal tract beyond corticobulbar
Where would a lesion causing unilateral face and arm weakness be?
Cortex area that’s arm and face
Where would a lesion causing unilateral leg weakness be?
Just leg cortex area
Lumbosacral plexus
Lumbar cord
What is Bell’s Palsy?
An ipsilateral LMN facial weakness. Often viral (herpes zoster) complication affecting the facial nerve
What causes unilateral facial weakness?
What causes bilateral arm weakness?
A lesion in the cervical cord/spine
What causes bilateral leg weakness?
Paraparesis
Medical emergency
Mostly from SC lesions in thoracic or lumbar
What causes tetraparesis?
Basically just like scramble the top of your brain
What is the presentation of a radial nerve injury?
Wrist drop
What is the presentation of a peroneal nerve injury?
Foot drop
Is ALS (amytrophic lateral sclerosis) UMN or LMN?
Both
Is PLS (primary lateral sclerosis) UMN or LMN?
UMN
Is PMA (progressive muscular atrophy) UMN or LMN?
LMN
What are some features of myasthenia gravis?
Often starts in eyes
The last slide seems like it might be relevant but I’m mad because I did all the rest and they’ll probably do a Q from this so have a squiz I guess
Nvm I changed my mind there are cards on it but still read it
Where is the lesion for hemiplegia + cortical signs
cerebral hemisphere
Where is a pure hemiplegia lesion
cerebral or brainstem subcortical white matter
If you have hemiplegia and cranial nerve palsies where is the lesion
brainstem
If you have tetraparesis where is the lesion
scrambled top of head, brainstem, cervical cord, MND, GBS, NMJ
if you have global weakness what is the lesion
GBS
NMJ
myopathy
if you have paraparesis where is the lesion
mid frontal lobes
spinal cord
L5 radiculoplexus
If you have monoplegia where is the leison
cerebral hemisphere
hemicord
plexus
nerves
If you have no sensory involvement where is the problem most likely
muscle, nmj and MND
