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Weakness & Fatigue

Focal or diffuse? UMN or LMN? Hours or months?

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Your objective: explain the approach, recognize important warning signs, then test your recall.

Abbreviations explained
ACS
Acute coronary syndrome
OMI
Occlusion myocardial infarction
ECG
Electrocardiogram
PE
Pulmonary embolism
POCUS
Point-of-care ultrasound
QTc
QT interval corrected for heart rate
LBBB
Left bundle branch block
RBBB
Right bundle branch block
hs-cTn
High-sensitivity cardiac troponin
CTA
Computed tomography angiography
ICU
Intensive care unit
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The jobFocal or diffuse? UMN or LMN? Hours or months?

  1. Decide true motor weakness vs fatigue vs functional limit.
  2. Map the pattern: brain, cord, root, nerve, NMJ, muscle — reflexes are the discriminator.
  3. Watch NIF/VC in GBS and myasthenia.
  4. Cord/cauda: MRI now. Dexamethasone is for MSCC, not routine discogenic CES.

First decide: true motor weakness, generalized fatigue, or functional limitation.

True acute weakness is a neurologic emergency — map the pattern (brain, cord, root, nerve, NMJ, muscle), watch respiratory reserve, and move fast on cord compression and GBS.

Acute stroke / TIA Critical

Key: Sudden focal weakness — last-known-well, glucose, non-contrast CT. IV TNK/alteplase ≤4.5 h if eligible; EVT ≤24 h in selected patients using current vessel/imaging criteria, including some large-core infarcts (2026 AHA/ASA). Do not exclude EVT solely because 6 hours have passed.

Guillain-Barré syndrome Critical

Key: Ascending (or variant) weakness, areflexia; monitor NIF/VC — intubate before the crash. CSF may be normal in the first week.

Cauda equina / cord compression Critical

Key: Back pain + leg weakness ± saddle anesthesia, urinary retention — emergency MRI + spine surgery. Dexamethasone is for metastatic cord compression (NICE NG234), not routine for discogenic CES.

Myasthenic crisis Critical

Key: Fatigable weakness (ptosis, diplopia worse late in the day); NIF monitoring; avoid macrolides, fluoroquinolones, aminoglycosides.

Transverse myelitis Critical

Key: Sensory level, bladder dysfunction — MRI + steroids after infection is addressed.

Botulism / tick paralysis Emergent

Key: Descending weakness with poorly reactive pupils (botulism); find and remove the tick.

Rhabdomyolysis / dyskalemic paralysis Emergent

Key: Pigmented urine or extreme K⁺ shifts — ECG and treat the potassium.

Anemia, hypothyroid, depression, OSA, deconditioning Common

Key: The chronic-fatigue cohort — screen systematically.

Tick what your patient has — the banner updates as you go.

Tempo and pattern

sudden focal (vascular), ascending over days (GBS), fatigability through the day (MG)

Sensory level, back pain, bowel/bladder function, cancer history (MSCC)

Tick exposure, recent infections (Campylobacter), medications

Family history (periodic paralysis, dystrophy)

Fatigue screen

sleep, mood, weight change, bleeding, fevers

Map the pattern

proximal vs distal, symmetric vs focal, UMN (brisk reflexes, spasticity) vs LMN (flaccid, areflexia)

Reflexes — the single best discriminator (absent in GBS, brisk in cord/brain)

Perianal sensation and rectal tone when cauda equina is possible

Fatigability

sustained upgaze for ptosis (MG)

Respiratory

single-breath count, cough strength

Bedside

  • Glucose; NIHSS if focal
  • NIF / vital capacity in suspected GBS or MG
  • Urine color for myoglobin; tick search
  • Post-void residual if CES is possible

Labs

  • K⁺, phosphate, magnesium, CK, TFTs, CBC, B12, glucose/HbA1c
  • CSF (albuminocytologic dissociation) for GBS — may be normal early; AChR/MuSK antibodies for MG

Imaging

  • Urgent MRI spine for cord/cauda/MSCC suspicion — do not delay for plain films
  • CT/MRI brain for focal weakness
Medication safety reminder

Use this as a first-pass prompt; verify all medications, doses, concentrations, contraindications, weight, pregnancy status, and local protocols before administration.

Check indication, allergy, route, renal/hepatic risk, interactions, monitoring, and local formulary.

Discharge

  • Chronic fatigue with a clear treated cause and safe follow-up; benign post-viral fatigue with red-flag education.

Admit

  • GBS/MG under monitoring (even if ambulating), electrolyte derangements, moderate rhabdo on IV fluids, progressive unclear cases.

ICU / emergency intervention

  • Impending respiratory failure (NIF weaker than −30 cmH₂O, e.g. −20; VC <15–20 mL/kg; or 20/30/40 rule), cord compression, severe hyperkalemia, stroke needing intervention.

Use objective reassessment and the local pathway.

Before the next decision · reassess and hand over

Use these learning prompts with the presentation’s pathway. They are not discharge criteria.

  1. Reassess: compare symptoms, observations and examination with the initial assessment and response to treatment.
  2. Warning signs for Weakness & Fatigue:
    • Progressive ascending weakness or falling NIF/VC
    • Back pain with weakness or urinary retention (cauda equina / MSCC)
    • Sudden focal deficit (stroke pathway)
    • Respiratory symptoms in neuromuscular disease
    • Dark urine with muscle pain (rhabdo)
    • Bilateral leg weakness with a sensory level
    • Known cancer + new spinal pain or neurology (MSCC)
  3. Reconsider: check unresolved findings and alternative explanations, including the pitfalls below.
  4. Escalate: communicate deterioration, uncertainty or needs beyond the current setting.
  5. Plan the transition: identify outstanding results, responsibility for follow-up, patient understanding and specific return advice.
Review this presentation’s disposition pathway →Practice a handover →

Clinical Pearls

  • First decide true weakness vs fatigue, then map the pattern with reflexes.
  • Watch NIF/VC in GBS and myasthenia — intubate before the crash.
  • Dexamethasone is for metastatic cord compression, not routine discogenic cauda equina.
  • Do not wait for a “complete” CES picture before MRI.

Pitfalls

  • GBS presenting as back pain or with preserved reflexes early — serial exams and NIFs. CSF protein often rises only after the first week.
  • Myasthenia worsens with macrolides, fluoroquinolones, and aminoglycosides.
  • Do not wait for a “complete” CES picture (full saddle anesthesia) before MRI.
  • Dexamethasone is indicated for suspected MSCC, not as routine therapy for discogenic cauda equina.
  • Periodic paralysis after a heavy carbohydrate meal or exercise — check K⁺ and family history.
  • Elderly “weakness” may hide a hip fracture, pneumonia, or sepsis.
PRACTICE REFRESHER

Rapid recall

Test your first action and the dangerous diagnoses before revealing the answer.

01 · First move

Before you scroll, what needs to happen first?

02 · Immediate threats

Name at least two diagnoses that cannot wait.

PRIVATE TO THIS DEVICE

Your learning note

Capture a weak point, a teaching pearl, or a question to take to your next shift.

Review schedule starts when marked reviewed
Low Back PainSeizuresAltered Mental StatusDiplopiaECG Guide

Selected guidance · source check 2026-09-07. These 1 source links support selected teaching points, not a complete review of this topic. Check population, setting and local protocol before applying a recommendation.

  • Rosen’s Emergency Medicine, 10th ed. (2023) — weakness & neuromuscular disease
  • EAN/PNS 2023 Guillain-Barré syndrome guideline
  • NICE NG234 (2023) metastatic spinal cord compression — dexamethasone 16 mg for MSCC with neurology
  • AAN guidance on myasthenic crisis
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