- Determine if patient has actual neuromuscular weakness (suggesting CNS dysfunction) or non-neuromuscular weakness.
- True motor weakness (neuromuscular weakness)? Bilateral or unilateral (distribution of weakness)?
- Bilateral weakness:
- Symmetric ascending paralysis? Guillain-Barre Syndrome
- Weakness involving both central and peripheral nervous system? Inflammatory/Autoimmune or toxic/metabolic
- Discrete sensory level and/or bladder dysfunction? Spinal Cord Lesion
- Involvement of proximal > distal musculature? Myopathy, Polymyalgia Rheumatica
- Involvement of distal > proximal musculature? Neuropathy
- Unilateral weakness: CVA, TIA
- Bilateral weakness:
- If non-neuromuscular weakness then BROAD differential, obtain:
- Onset of weakness sudden or gradual?
- Significant event surrounding onset of weakness?
- Temporal pattern to weakness? Fluctuating or fixed weakness?
- Weakness with repetitive motions? Neuromuscular junction pathology like Myasthenia Gravis
- Associated symptoms?
- Headache: SAH, epidural/SDH, complicated migraines (young females), not usually stroke/TIA (unless high intracranial pressure)
- Vision changes: Posterior circulation stroke, Myasthenia Gravis
- Shortness of breath: cardiovascular etiology
- Chest pain or neck pain: Acute carotid/vertebral/aortic dissection, AMI
- Abdominal or back pain:
- with alteration of bowel habits? Botulism, organophosphate poisoning, toxins, Guillain-Barre Syndrome, Electrolyte Imbalance.
- with lower extremity weakness? AAA with spinal cord infarction
- Back pain with unilateral weakness? Herniated disk with nerve impingement
- Bilateral weakness with sensory level s/p trauma? SCI, Cauda Equina Syndrome
- Nausea/vomiting: sign of ↑ ICP, can lead to electrolyte imbalances
- Rash: Dermatomyositis
Focus on clarifying if patient 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||Ocular, 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:
- Neuromuscular junction 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 patients:
- CBC (anemia)
- Chem 10 (electrolyte disturbance, hypoglycemia, uremia, cardiac enzymes)
- ECG (Ischemia, hypo/hyperkalemia)
- CK (myopathies)
- Thyroid studies
- CXR and UA (if infectious symptoms or elderly)
- FVC (if evidence of respiratory compromise, i.e. Myasthenia, GBS)
- CT head (if focal findings, altered mental status, history of cancer, history of any trauma in patient on anticoagulation)
- MRI or CT with contrast (if a structural cord lesion is suspected)
- LP (CNS infection, GBS)
- Severe fatigue
- Inability to protect airway
- Rapidly increasing PaCO2
- Hypoxemia despite O2
- FVC <12 mL/kg
- Neg Insp Force <20 cm H2O
- Depends on process
- If normal initial workup, make sure has no respiratory compromise