Basics
Description
- Defined as a decrease in physical strength or energy
- Often multifactorial
- Distinguish neuromuscular disorder vs. non-neuromuscular disorder
- Categories of neuromuscular disorders:
- Upper motor neuron (UMN) lesions:
- Deep tendon reflexes (DTR) increased
- Plantar reflexes upgoing
- Increased muscle tone
- Muscle atrophy absent
- Lower motor neuron (LMN) lesions:
- DTRs decreased to absent
- Plantar reflexes absent or normal
- Decreased muscle tone
- Muscle atrophy present
- Fasciculations
- Neuromuscular junction (NMJ) lesions:
- DTRs normal
- Plantar reflexes normal or absent
- Decreased muscle tone
- Categories of non-neuromuscular disorders:
- Infectious
- Endocrine
- Metabolic
- Cardiac
- Rheumatologic
- Toxic
- Psychiatric
Etiology
- Neuromuscular disorders:
- UMN lesions:
- Multiple sclerosis
- Amyotrophic lateral sclerosis (mixed)
- Transverse myelitis
- Poliomyelitis
- LMN lesions:
- Guillain " “Barre syndrome
- Toxic neuropathies
- Impingement syndromes
- Diphtheria
- Porphyria
- Seafood toxins
- NMJ lesions/others:
- Myasthenia gravis
- Lambert " “Eaton syndrome
- Botulism
- Periodic paralysis
- Tick paralysis
- Non-neuromuscular disorders:
- Dehydration
- Anemia
- Electrolyte imbalances
- Malignancy
- Cerebrovascular accident
- Head or neck trauma
- Myocardial ischemia
- Infection/sepsis:
- UTI
- Pneumonia
- Meningitis
- Mononucleosis
- HIV
- Arborviruses
- Endocrine abnormalities:
- Hypothyroidism
- Adrenal crisis
- Periodic paralyses
- Rheumatologic disorders:
- Systemic lupus erythematosus
- Polymyalgia rheumatica
- Toxins:
- Medications
- Environmental
- Carbon monoxide poisoning
- Cocaine
- Alcohol
Diagnosis
Signs and Symptoms
- Altered physical strength:
- Assessment of strength:
- 1: No contraction
- 2: Active movement with gravity eliminated
- 3: Active movement against gravity
- 4: Active movement against gravity and resistance
- 5: Normal power
- Change in muscle tone:
- Flaccidity
- Spasticity
- Rigidity
- Abnormal DTRs
- Abnormal plantar reflexes
- Muscle atrophy:
- Difference of >1 cm in the leg and thigh and >0.5 cm in the forearm and arm
- Systemic findings:
- Weakness
- Fatigue
- Dizziness
- Paresis
- Paresthesias
- Hoarse voice
- Dysphagia
- Visual changes
- Confusion
- Associated symptoms:
- Fever
- Chest pain
- Dyspnea
- Cough
- Weight loss
- Rash
- Dysuria
- Upper respiratory infection symptoms
Essential Workup
- Review of medications
- Clinical suspicion gathered through history and physical exam guides further testing:
- Generalized vs. focal
- Acute vs. chronic
- Proximal vs. distal
- Ascending vs. descending
- Symmetric vs. asymmetric
- Improved vs. worsened with activity
Diagnosis Tests & Interpretation
Diagnostic testing should be broad unless history and physical exam identify the cause of weakness. ‚
Lab
- Serum glucose
- CBC
- Electrolytes
- BUN/creatinine
- Toxin screen
- Urinalysis
- Thyroid function tests (rule out hypothyroidism)
- ESR (rule out rheumatologic cause)
- Carboxyhemoglobin (rule out CO poisoning)
- Troponin/CK-MB (rule out cardiac ischemia)
- Digoxin level (rule out digoxin toxicity)
Imaging
- EKG (rule out acute coronary syndrome [ACS]/arrhythmia)
- CXR (rule out pneumonia)
- CT/MRI head (rule out intracranial pathology)
Diagnostic Procedures/Surgery
- Bedside spirometry:
- Forced vital capacity, negative inspiratory force, peak expiratory flow rate
- May identify those with impending ventilatory failure
- Lumbar puncture:
- In suspected Guillain " “Barre syndrome:
- Albumin-cytologic dissociation in CSF (protein >400, WBC <10) is virtually diagnostic.
- Tensilon test:
- Distinguishes myasthenic crisis from cholinergic crisis in myasthenia gravis
Differential Diagnosis
- Physiologic causes of weakness:
- Simple fatigue:
- Excessive physical activity
- Inadequate rest
- Excessive or inadequate diet
- Pregnancy
- Psychiatric causes of weakness:
- Anxiety/depression
- Dependent personality
- Hypochondriasis
- Chronic fatigue syndrome
- Fibromyalgia
- Malingering
Treatment
Treatment is geared to the underlying cause of weakness. ‚
Pre-Hospital
- Supplemental oxygen
- IV access
- Finger-stick glucose determination
- Consider endotracheal intubation in patients with severe respiratory distress.
Initial Stabilization/Therapy
- Supplemental oxygen
- IV access
- Endotracheal intubation for impending ventilatory failure
Ed Treatment/Procedures
- Neurology consult if needed
- When the diagnosis is determined, specific therapies can be applied:
- TPA for CVAs meeting criteria
- Plasma exchange and/or IV immunoglobulin (IVIG) for Guillain " “Barre syndrome
- Hydrocortisone for adrenal insufficiency
- Potassium supplementation for hypokalemia
- Dextrose for hypoglycemia
- Antibiotics for infectious etiologies
- Specific antidotes for botulism and diphtheria
- Digibind for digoxin toxicity
Follow-Up
Disposition
Admission Criteria
- All patients with new-onset neuromuscular disorders should be admitted for definitive diagnosis.
- Any evidence of impending ventilatory or circulatory compromise warrants ICU admission.
Discharge Criteria
- Resolution of symptoms
- Stable vital signs
- Definitive diagnosis and correction of abnormality
Follow-Up Recommendations
- Discharged patients with non-neurologic etiologies should have follow-up with their PCP.
- Discharged patients with neurologic etiologies should have urgent neurology follow-up.
Pearls and Pitfalls
- Identify early and aggressively treat patients at risk for respiratory compromise due to Guillain " “Barre, botulism, myasthenia gravis.
- Identify elderly patients with ACS or infection presenting as weakness.
- Consider endocrine causes of weakness, including adrenal insufficiency and hypothyroidism.
Additional Reading
- Anderson ‚ RS Jr, Hallen ‚ SA. Generalized weakness in the geriatric emergency department patient: An approach to initial management. Clin Geriatr Med. 2013;29(1):91 " “100.
- Chew ‚ WM, Birnbaumer ‚ DM. Evaluation of the elderly patient with weakness: An evidence based approach. Emerg Med Clin North Am. 1999;17(1):265 " “278.
- Losman ‚ E. Weakness. In: Marx ‚ J, ed. Rosens Emergency Medicine: Concepts and Clinical Practice. 7th ed. St. Louis, MO: Mosby; 2009:87 " “92.
- LoVecchio ‚ F, Jacobson ‚ S. Approach to generalized weakness and peripheral neuromuscular disease. Emerg Med Clin North Am. 1997;15(3):605 " “623.
Codes
ICD9
- 728.2 Muscular wasting and disuse atrophy, not elsewhere classified
- 728.87 Muscle weakness (generalized)
- 780.79 Other malaise and fatigue
- 340 Multiple sclerosis
- 335.20 Amyotrophic lateral sclerosis
- 357.0 Acute infective polyneuritis
ICD10
- M62.50 Muscle wasting and atrophy, NEC, unsp site
- M62.81 Muscle weakness (generalized)
- R53.1 Weakness
- G35 Multiple sclerosis
- G12.21 Amyotrophic lateral sclerosis
- G61.0 Guillain-Barre syndrome
SNOMED
- 13791008 Asthenia (finding)
- 26544005 Muscle weakness (finding)
- 88092000 Muscle atrophy (disorder)
- 24700007 Multiple sclerosis (disorder)
- 40956001 Guillain-Barre syndrome (disorder)
- 86044005 Amyotrophic lateral sclerosis (disorder)