Weakness

Approach

Determine if pt has actual neuromuscular weakness (suggesting CNS dysfuction) or non-neuromuscular weakness.

DDX

1. Neuromuscular weakness involves derangement of CNS (UMN), PNS (LMN), the motor endplate, or the muscle:
   1. Can't miss dx:
      1. UMN: CVA, Intracerebral Hemorrhage (ICH), Multiple Sclerosis, ALS (UMN & LMN).
      2. Spinal cord disease: Infection (Epidural Abscess (Spinal)), infarction/ischemia, trauma (Spinal Cord Syndromes), inflammation (Transverse Myelitis), tumor.
      3. Peripheral nerve disease: Guillain-Barre Syndrome, toxins (Ciguatera), Tick Paralysis, DM neuropathy (non-emergent).
      4. NMJ disease: Myasthenia Gravis crisis, Botulism, Organophosphate Toxicity, Lambert-Eaton Myasthenic Syndrome.
      5. Muscle disease: dermatomyositis, polymyositis, alcoholic myopathy, Rhabdomyolysis.

1. Non-neuromuscular weakness can be infectious, cardiovascular, metabolic, toxicologic:
   1. Can't miss dx:
      1. ACS/MI
      2. Arrhythmia/Syncope
      3. severe infection/Sepsis
      4. Hypoglycemia
      5. Periodic paralysis (electrolyte disturbance, K, Mg, Ca)
      6. Respiratory failure
   2. Emergent Dx:
      1. Symptomatic Anemia
      2. Severe dehydration
      3. Hypothyroidism
      4. Polypharmacy
      5. Malignancy

Workup

On all pts:

1. CBC (anemia)
2. Chem 10 (electrolyte disturbance,hypoglycemia, uremia)
3. ECG (Ischemia,hypo/hyperkalemia)

Consider:

1. CK (mypoathies)
2. ESR
3. CXR and UA (pt w/infectious sx and elderly)
4. FVC (if e/o resp compromise, i.e. Myasthenia, GBS)
5. CT head (if focal findings, AMS, h/o cancer, h/o any trauma in pt on anticoagulation)
6. LP (CNS infection, GBS)

HPI

1. True motor weakness (neuromuscular weakness)? Bilateral or unilateral (distribution of weakness)?
   1. Bilateral weakness:
      1. With symmetric ascending paralysis? GBS (MCC of symmetric paralysis).
      2. With motor weakness involving both CN and peripheral nerves? Inflammatory/Autoimmune (MS, transverse myelitis, MG), toxic/metabolic (botulism).
      3. With discrete sensory level and/or bladder dysfxn? Spinal cord lesion.
      4. With involvement of proximal > distal musculature? Myopathy (poly/dermatomyositis).
      5. Unilateral: Hemiparesis (unilateral weakness), hemiplegia (unilateral paralysis) is more likely in CVA, TIA.
2. 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).
   1. In adults >50, especially women, generalized weakness complaint should prompt consideration for cardiac ischemia.
   2. In adults >65 weakness may be only Sx of serious infection, electrolyte disturbance, or CV compromise.
3. Onset of weakness sudden or gradual?
   1. Sudden onset suggests vaso-occlusive etiology (CVA, TIA). Difficult to assess time of onset given pt may be unaware (sleeping).
   2. Gradual onset likely non-vascular. Think inflammatory CNS (MS, transverse myelitis), inflammatory MSK (myositis), compression neuropathy (CTS), autoimmune (MG, GBS), or toxins/metabolic process.
4. Significant event surrounding onset of weakness?
   1. SZ prior to weakness? Todd’s paralysis.
   2. Migraine HA? Complicated migraine.
   3. Sudden onset of severe HA? SAH.
   4. Trauma? Epidural or SDH.
   5. Severe migratory neck or chest pain? Arterial dissection syndromes.
5. Temporal pattern to weakness? Fluctuating or fixed weakness?
   1. Weakness with repetitive motions? NMJ pathology like MG (difficulty chewing, typing, eyelid droop, diplopia, etc).
6. Associated Sx?
   1. HA: think SAH, epidural/SDH, complicated migraines (young females), not usually associated with stroke/TIA unless having ↑ICP.
   2. Vision changes: diplopia think posterior circulation stroke (CN III problem), visual field loss, MG.
   3. SOB: think CV etiology.

CP or neck pain: think acute arterial dissection (thoracic aorta vs carotid/vert arteries), AMI.

1. 1. Abdominal or back pain:
      1. Abd pain with alteration of bowel habits, melena/hematochezia? Botulism, organophosphate poisoning, toxins, GBS, electrolyte imbalance.
      2. with LE weakness? could be AAA with spinal cord infarction.
      3. Back pain with unilateral weakness? Herniated disk with nerve impingement.
      4. BLE weakness with sensory level, priapism, in setting of trauma? think SCI, cauda equina syndrome, primary spinal cord lesion, compressive spinal cord lesions (epidural abscess/hematoma).
   2. N/V: sign of ↑ ICP, can lead to electrolyte imbalances.
   3. Rash: dermatomyositis.
2. Ask about recent infectious illness, trauma, toxin exposure, alcohol, drug use (cocaine leading to TIA, SAH, stroke). Review meds for bblocker, diuretics, psychotropic meds that may alter electrolytes or cause side effects.

Physical Exam

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.

Neuro Exam Findings

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 - +/-

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

8/15/13 CELEDON (adapted from Rosen, Tintinalli, Intro to Clincal EM, Lampe, Birnbaumer, Donaldson)