Weakness - Causes, Focal vs. Generalized Weakness, Emergency Evaluation, Diagnosis & Treatment

“Weakness” is a very non-specific complaint. It can indicate benign fatigue or life-threatening neurologic, hematologic, metabolic, endocrine, or toxic conditions.
Because the differential is wide, the key to diagnosis is:

1. Get a detailed history

2. Check vital signs and glucose immediately

3. Determine whether weakness is focal or generalized

Your uploaded chart provides a structured framework, expanded here for learner clarity.

The Emergency Approach to Weakness

Weakness requires rapid but organized evaluation:

Step 1: Immediate EKG & Fingerstick Glucose

Never miss:

• Hypoglycemia
• Cardiac ischemia or arrhythmia

Step 2: Assess Vital Signs

Abnormalities provide valuable clues:

Vital Sign Change	Possible Cause
↓ O₂	Respiratory or cardiac disease
↓ Glucose	Hypoglycemia
↑ Temp	Infection or heat stroke
↓ Temp	Hypothyroidism, exposure

Step 3: Decide — Is Weakness Focal or Generalized?

This decision dramatically narrows the differential.

Focal Weakness (Neurologic Localization)

Focal weakness is almost always neurologic and requires urgent evaluation.

A. Stroke / Intracranial Hemorrhage (CVA/ICH)

Clues:

• Sudden onset
• Atrial fibrillation
• Anticoagulant use
• Asymmetry, facial droop, speech difficulty

Workup:

CT head (STAT)

Treatment:

• Emergent neurology
• Consider tPA if criteria met

B. Guillain-Barré Syndrome (GBS)

Clues:

• Ascending paralysis
• Decreased reflexes
• Recent viral infection
• Symmetric weakness

Workup:

• Clinical diagnosis
• LP if needed

Treatment:

• Admit
• Consider intubation (respiratory failure risk)
• Neurology consult
• IVIG or plasmapheresis

C. Multiple Sclerosis (MS)

Clues:

• Young patient
• Visual changes (optic neuritis)
• APD (afferent pupillary defect)

Workup:

MRI

Treatment:

• Neurology follow-up
• Steroids for acute flares

D. Myasthenia Gravis

Clues:

• Blurry vision
• Diplopia
• Ptosis
• Fatigability with use

Workup:

• Edrophonium test (historical)
• EMG, antibodies

Treatment:

• Pyridostigmine
• Neurology consultation
• Possible steroids or IVIG

E. Transverse Myelitis

Clues:

• Rapid onset weakness
• Sensory level
• Rectal tone abnormal
• Reflex changes

Workup:

MRI spine

Treatment:

• Neurology
• Steroids (depending on cause)

Generalized Weakness

Generalized weakness is often systemic, not neurologic.
Common causes include metabolic abnormalities, infection, anemia, endocrine disease, dehydration, or medication effects.

Common Causes of Generalized Weakness

A. Anemia

Clues:

• Pallor
• Fatigue
• Melena/dark stools

Workup:

• CBC
• FOBT
• Type & Screen

Treatment:

• Treat source
• Consider transfusion

B. Cardiac Causes

Clues:

• Elderly patient
• SOB, chest pain, palpitations

Workup:

• EKG
• Troponins

Treatment:

• ASA
• Admission

C. Depression

Often presents as weakness or fatigue.

Clues:

• Low mood
• ↓ motivation
• Medication effects
• SI/HI screening required

Workup:

Clinical, exclusion of medical causes

Treatment:

• Psych support
• Follow-up

D. Electrolyte Abnormalities

Common in dialysis patients or those on diuretics.

Clues:

• Weakness with cramping
• Arrhythmias
• Recent dialysis

Workup:

• BMP
• EKG

Treatment:

Replace electrolytes (especially K⁺)

E. Hypothyroidism

Clues:

• Weight gain
• Cold intolerance
• Bradycardia
• Edema

Workup:

TSH

Treatment:

• Endocrine follow-up
• Thyroid hormone therapy

F. Hypovolemia / Dehydration

Clues:

• Dry mucous membranes
• Orthostatic symptoms

Workup:

• BUN/Cr
• Clinical exam

Treatment:

IV fluids

G. Infection

Clues:

• Fever
• Cough, dysuria, abdominal pain, etc.
• Systemic symptoms

Workup:

• UA
• Blood cultures
• CXR
• LP if indicated

Treatment:

• Antibiotics
• Fluids
• Source control

H. Medications

Diuretics, antihypertensives, psych meds, and pain medications commonly cause weakness.

Workup:

Medication review

Treatment:

• Adjust medication
• Supportive care

I. Rheumatologic Conditions

e.g., SLE, Polymyalgia Rheumatica (PMR)

Clues:

• Joint pain
• Stiffness
• Systemic symptoms

Workup:

ESR/CRP

Treatment:

Rheumatology referral

J. Toxidrome

Toxins/medications causing weakness.

Clues:

• Drug ingestion
• Pupils, skin, mental status changes

Workup:

Clinical

Treatment:

• Antidote if available
• Poison control consultation

Pearls & Pitfalls (From Chart)

✔ Weakness is vague — get a detailed story

Determine:

• Onset
• Progression
• Focal vs. generalized
• Associated symptoms

✔ Always check the basics

Low O₂, low glucose, electrolyte disorders can mimic serious neurologic disease.

✔ “Focal” always trumps “generalized” in importance

Focal weakness → think stroke first.

✔ Consider Guillain-Barré in rapidly ascending weakness

✔ Don’t miss medication-induced weakness

Especially diuretics, antipsychotics, sedatives.

Documentation Essentials

Vital Signs

• NAD (no acute distress)
• Fever status

HEENT

• Conjunctival pallor
• Pupils equal/reactive
• EOMI

Lungs

Any crackles or wheeze

Neuro

• Full neurologic exam
• Cranial nerves
• Reflexes
• 5/5 strength in all extremities

Rectal (if GI bleed suspected)

• Tone
• FOBT result

High-Yield Summary Table

Type	Condition	Key Clues	Workup	Treatment
Focal	Stroke	Sudden, AFib	CT	tPA/neuro
	GBS	Ascending, ↓ reflexes	Clinical	Admit, IVIG
	MS	Vision loss	MRI	Steroids
	MG	Ptosis, diplopia	Edrophonium	Pyridostigmine
	Transverse Myelitis	Sensory level	MRI	Steroids
General	Anemia	Pallor	CBC	Transfuse?
	Cardiac	CP/SOB	EKG, trops	ASA, admit
	Depression	Low mood	Exclusion	Psych
	Electrolytes	Dialysis, cramps	BMP	Replace K⁺
	Hypothyroid	Cold, brady	TSH	Thyroid meds
	Hypovolemia	Dry	Clinical	IVFs
	Infection	Fever	UA/BCX/CXR	ABx
	Toxo/Drugs	Med use	Clinical	Antidote

FAQs About Weakness

1. What’s the most dangerous cause of weakness?

Stroke or Guillain-Barré with respiratory compromise.

2. When should a CT scan be used?

Whenever focal neurologic deficits are present.

3. How do I differentiate true weakness from fatigue?

Ask the patient to perform movements against resistance — fatigue improves with effort; weakness worsens.

4. What if labs and imaging are normal?

Consider:

• Depression
• Fibromyalgia
• Medication effects
• Chronic fatigue syndrome

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