limb weakness / stroke
In the light of previous TBL, I have
realized that thinking about the MECHANISM of specific signs / symptoms helps
greatly in thinking about the differential diagnosis and patient evaluation
(and perhaps management as well)
what is limb weakness?
For us to discuss a particular topic, we
must first define or describe what it is.
Weakness is a word used to describe a
loss of power or control of voluntary muscle.
Some difficulty in movement may be
interpreted as “loss of dexterity” as well.
It should be distinguished from…
·
Increased fatiguability
o
Inability to sustain the
performance of an activity that should be normal for a person of that age,
gender, and size
·
Bradykinesia
o
Increased time is needed for
full power to be exerted
·
Apraxia
o
Loss / disorder of planning and
initiating a skilled or learned movement unrelated to a significant
motor/sensory deficit.
·
Loss of proprioception
o
May cause “weakness” due to
difficulty in coordination
Mechanism of limb weakness
How does limb weakness occur?
·
3 main causes of limb weakness
- derangement of;
o
Upper motor neuron disorder
§ Cerebral cortex
§ Descending tract
§ Internal capsule
§ Brainstem
§ Spinal cord
o
Lower motor neuron disorder
§ Ventral horn of spinal cord
§ Axons in spinal roots
§ Peripheral nerves
§ Neuromuscular junction
§ Skeletal muscle
o
Myopathic origin
§ Muscle fibre loss / disorder
§ Decrease in the number or contractile force of muscle fibres
activated within motor units
§ On EMG, size of each motor unit action potential decreased
§ A little different from diseases of the neuromuscular junction (MG)
o
Biochemical origin
§ Hypo / hyper kalemia
§ Hyper calcemia
§ Hypernatremia
§ Hyponatremia
§ Hypophosphatemia
§ hypermagnesemia
important questions to ask in weakness (Hx)
·
WHERE is the weakness?
o
Hemiparesis
o
Paraparesis
o
Quadriparesis
o
Monoparesis
o
Distal
o
Proximal
o
Restricted
·
HOW SEVERE is the weakness?
o
Total paralysis
o
Paresis
·
How long did it take to
develop?
o
Instant
o
Insidious
o
Episodic
·
Any associated symptoms?
o
Language deficit
o
Sensory disturbances
o
Cognitive abnormalities
o
seizures
more questions to ask in specific weakness (HX)
Hemiparesis
Hemiparesis results from an UMN lesion
above the midcervical spinal cord
Most such lesions above the foramen magnum
·
Presence of other neurological
symptoms? -
o
language, sensory, cognitive
abnormalities and seizures all point to cortical lesion.
o
If no associated symptoms, only
PURE motor deficit, it may point towards a small discrete lesion in the
posterior limb of the internal capsule cerebral peduncle or upper pons.
·
Combination with cranial nerve
signs
o
Is no cranial nerve signs -
§ may be due to lesion in the high cervical spinal cord
o
Ipsilateal cranial signs and
contralateral hemiparesis
§ Brainstem lesion
·
Combination with mixture of
neuro signs
o
Ipsilateral loss of
proprioception and contralateral loss of pain and temp. sense
§ Brown-sequard $ - (hemi-block of spine)
·
Acute / Chronic / episodic?
o
Acute / episodic onset
§ Usually from ischemic / hemorrhagic stroke
§ May also relate to hemorrhage from a SOM
§ Trauma
§ Inflammatory process as in
·
MS,
·
Abscess,
·
Sarcoidosis
o
Subacute onset (over days / weeks)
§ Extensive DD
·
Subdural hematoma
o
Elderly and anticoagulated more
common
·
Infectious causes
o
Cerebral abscess
o
Fungal granuloma
o
Meningitis
o
Parasitic infection
o
Toxoplasmosis
§ Esp. in AIDS
·
Neoplasms
·
Inflammatory
o
MS
o
Sarcoidosis
o
Chronic
§ Usually neoplasms or vascular malformation
§ Chronic subdural hematoma
§ Degenerative disease
physical examination of weakness
In PE, we usually try to find out
whether it is a
·
UMN /LMN
·
Involving cranial nerve or not
·
Purely motor, or mixed
Sign
|
UMN
|
LMN
|
Myopathic
|
Atrophy
|
None
|
severe
|
Mild
|
Fasciculations
|
None
|
common
|
None
|
tone
|
Spastic
|
decreased
|
Normal / decreased
|
Distribution of weakness
|
Pyramidal / regional
|
Distal / segmental
|
Proximal
|
Tendon reflexes
|
Hyperactive
|
hypoactive
|
Normal / hypo
|
Babinski’s sign
|
present
|
none
|
None
|
·
Is the patient alert and
conscious!?
Glasocow Coma Scale (GCS)
·
Comprises of 3 components
o Best verbal response (max 5)
§
1
·
No speech at all
§
2
·
Incomprehensive vocalization
(ohhh ahhh)
§
3
·
Inappropriate words (random
words, no conversation)
§
4
·
Conversing but disoriented and
confused
§
5
·
Conversing and oriented.
o Eye opening (max 4)
§
1
·
No eye opening at all
§
2
·
Open in response to painful
stimulus
§
3
·
Open to any verbal stimulus
only (don’t touch)
§
4
·
Spontaneously open
o Best Motor response (max 6)
§
1
·
No response at all
§
2
·
Abnormal extension to pain
(decerebrate posture)
§
3
·
Abnormal flexion to pain (decorticate
posture)
§
4
·
Withdrawal to pain (pull hand
away from pain)
§
5
·
Purposeful movement, Localizing
to pain (pushes source of pain away)
§
6
·
Obeying commands
o
