Determine if pt has actual neuromuscular weakness (suggesting CNS dysfuction) or non-neuromuscular weakness.
- True motor weakness (neuromuscular weakness)? Bilateral or unilateral (distribution of weakness)?
- Bilateral weakness:
- Unilateral weakness: CVA, TIA
- If non-neuromuscular weakness then BROAD Ddx obtain:
- ECG, CBC, Chem10, LFTs, blood cx, UA/UCx, drug levels, CXR, Consider Head CT (focal deficit, AMS, h/o CA, anticoagulation w/minor trauma)
- Onset of weakness sudden or gradual?
- Significant event surrounding onset of weakness?
- Temporal pattern to weakness? Fluctuating or fixed weakness?
- Weakness w/repetitive motions? NMJ pathology like Myasthenia Gravis
- Associated Sx?
- HA: SAH, epidural/SDH, complicated migraines (young females), not usually stroke/TIA (unless high ICP)
- Vision changes: Posterior circulation stroke, Myasthenia Gravis
- SOB: CV etiology
- CP or neck pain: Acute arterial dissection, AMI
- Abdominal or back pain:
- w/alteration of bowel habits? Botulism, organophosphate poisoning, toxins, Guillain-Barre Syndrome, Electrolyte Imbalance.
- w/LE weakness? AAA with spinal cord infarction
- Back pain with unilateral weakness? Herniated disk w/nerve impingement
- BLE weakness w/sensory level s/p trauma? SCI, Cauda Equina Syndrome
- N/V: sign of ↑ ICP, can lead to electrolyte imbalances
- Rash: Dermatomyositis
Focus on clarifying if pt has true loss of strength and determining distribution of deficits. Check for trauma, carotid bruits, thyroid enlargement, irregular rhythm, unequal pulses, rashes or ticks.
|Upper motor neuron|
|Brainstem||"crossed" findings - ipsilateral cranial nerve weakness and contralateral hemiparesis|
|Lower motor neuron|
|Nerve||Distal > proximal and ascends||No||Diminished||Nl/parethesias||No|
|Motor end plate||Ooccular,bulbar and descends, fatigable||No||Nl/diminished||Nl/parethesias||No|
|Muscle||Proximal > distal||No||Nl/diminished||Normal||+/-|
- Neuromuscular weakness
- Upper motor neuron:
- Lower motor neuron:
- Spinal and bulbar muscular atrophy (Kennedy's syndrome)
- Spinal cord disease:
- Peripheral nerve disease:
- NMJ disease:
- Muscle disease:
- Non-neuromuscular weakness
- Can't miss diagnoses:
- Emergent Diagnoses:
- Other causes of weakness and paralysis
- Acute intermittent porphyria (ascending weakness)
On all pts:
- CBC (anemia)
- Chem 10 (electrolyte disturbance,hypoglycemia, uremia)
- ECG (Ischemia,hypo/hyperkalemia)
- CK (mypoathies)
- CXR and UA (pt w/infectious sx and elderly)
- FVC (if e/o resp compromise, i.e. Myasthenia, GBS)
- CT head (if focal findings, AMS, h/o cancer, h/o any trauma in pt on anticoagulation)
- LP (CNS infection, GBS)
- Severe fatigue
- Inability protect airway
- Rapidly increasing PaCO2
- Hypoxemia despite O2
- FVC <12 mL/kg
- Neg Insp Force <20 cm H2O