Weakness

Background

Acute/Generalized

Workup

1. cbc
2. chem 10 (esp. K, Mg, Ca, Phos)
3. ecg
4. +/- CK (r/o myopathy)
5. +/- FVC (eval impending resp failure, i.e. Myasthenia)
6. +/- ABG/CT/LP/TSH/UA (rhabdo)

Diagnosis

Upper Motor Neuron

• BRAIN
  • Weakness - variable
  • Bowel/Bladder - 
  • Reflexes - increased
  • Sens - diminished
  • Pain - no
  • Asymmetric/unilateral
    
• BRAINSTEM
  
  •  "crossed" findings - ipsilateral cranial nerve weakness and contralateral hemiparesis 
• CORD
  • Weakness - fixed level
  • Bowel/Bladder - YES
  • Reflexes - increased
  • Sens - diminished
  • Pain - +/-

Lower Motor Neuron

• NERVE
  • Weakness - distal > proximal and ascends
  • Bowel/Bladder - NO
  • Reflexes - diminished
  • Sens - nl/paresthesias
  • Pain - no

End-Plate/Muscle

• MOTOR END PLATE
  • Weakness - occular,bulbar and descends, fatigable
  • Bowel/Bladder - NO
  • Reflexes - nl/diminished
  • Sens - nl
  • Pain - no
• MUSCLE
  • Weakness - proximal > distal
  • Bowel/Bladder - NO
  • Reflexes - nl/diminished
  • Sens - nl
  • Pain - +/-

DDX

1. UPPER
   1. Multiple Sclerosis
   2. Poliomyelitis
   3. ALS (upper & lower motor)
2. CORD
   1. Painful
      1. Cord compression
   2. Painless
      1. Transverse Myelitis
      2. Spinal cord infarct
      3. Intramedullary tumor
3. NERVE
   1. Guillian-Barre
   2. Toxic neuropthy (Ciguatera)
   3. Tick paralysis
   4. Diabetic neuropathy
   5. Porphyria
4. MOTOR END PLATE
   1. Myasthenia Gravis
   2. Botulism (descending)
   3. Organophosphate Poisoning
   4. Lambert-Eaton
5. MUSCLE
   1. Painful
      1. Rhabdo
      2. Alcoholic
      3. Myopathy
      4. Polymyositis
      5. Dermatomyositis
      6. Toxins
      7. Hypophos
      8. Hypokalemia - post prandial/ family hx/ thyroid
      9. Polymyalgia rheum
   2. Painless
      1. Familial periodic paralysis
      2. Endocrine
6. MIXED
   1. Upper & Lower Motor Neuron
      1. ALS
   2. Sensory & Motor
      1. Peripheral neuropathy
7. NON-NEUROMUSCULAR
   1. MI
   2. Resp failure
   3. Sepsis
   4. Dehydration
   5. Anxiety
   6. Fibromyalgia/chronic fatigue
   7. Malignancy

Emergent Threat/ED Workup

1. CORD
   1. paralysis
   2. MRI, neurologist
   3. consdier steroids in high suspicion
2. NERVE
   1. resp failure
   2. FEV1, airway mgt, ticks?, neurologist
3. MOTOR END PLATE
   1. resp failure
   2. FEV1, airway mgt, Tensilon Test?
4. MUSCLE
   1. Rhabdo
   2. urine myoglobin, serum CK, BUN/Cr
   3. serum K+

Intubation Indications

1. Severe fatigue
2. Inability protect airway
3. Rapidly increasing PaCO2
4. Hypoxemia despite O2
5. FVC <12 mL/kg
6. Neg Insp Force <20 cm H2O

Source

2/26/06 DONALDSON (adapted from Rosen, Lampe, Birnbaumer)

adapted from Hockberger