TBL - Weakness and Stroke

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