Weakness
(Redirected from Muscle weakness)
Background
- Determine if patient has actual neuromuscular weakness (suggesting CNS dysfunction) or non-neuromuscular weakness.
Clinical Features
History
- 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:
- ECG, CBC, Chem10, LFTs, blood cultures, UA/urine culture, drug levels, CXR, Consider Head CT (focal deficit, altered, history of cancer, anticoagulation with minor trauma)
- Onset of weakness sudden or gradual?
- Significant event surrounding onset of weakness?
- Seizure prior to weakness? Todd’s paralysis
- Migraine headache? Complicated migraine
- Sudden onset of severe headache? SAH
- Trauma? Epidural or Subdural Hematoma
- Severe migratory neck or chest pain? Arterial dissection syndromes
- 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
Physical Exam
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.
Location | Weakness | Bowel/Bladder | Reflexes | Sensory | Pain |
Upper motor neuron | |||||
Brain | Variable | Increased | Diminished | No | |
Brainstem | "crossed" findings - ipsilateral cranial nerve weakness and contralateral hemiparesis | ||||
Cord | Fixed level | Yes | Increased | Diminished | +/- |
Lower motor neuron | |||||
Nerve | Distal > proximal and ascends | No | Diminished | Nl/parethesias | No |
End-plate/muscle | |||||
Motor end plate | Ocular, bulbar and descends, fatigable | No | Nl/diminished | Nl/parethesias | No |
Muscle | Proximal > distal | No | Nl/diminished | Normal | +/- |
Differential Diagnosis
Weakness
- Neuromuscular weakness
- Upper motor neuron:
- CVA
- Hemorrhagic stroke
- Multiple sclerosis
- Amyotrophic Lateral Sclerosis (ALS) (upper and lower motor neuron)
- Lower motor neuron:
- Spinal and bulbar muscular atrophy (Kennedy's syndrome)
- Spinal cord disease:
- Infection (Epidural abscess)
- Infarction/ischemia
- Trauma (Spinal Cord Syndromes)
- Inflammation (Transverse Myelitis)
- Degenerative (Spinal muscular atrophy)
- Tumor
- Peripheral nerve disease:
- Neuromuscular junction disease:
- Muscle disease:
- Rhabdomyolysis
- Dermatomyositis
- Polymyositis
- Alcoholic myopathy
- Upper motor neuron:
- Non-neuromuscular weakness
- Can't miss diagnoses:
- ACS
- Arrhythmia/Syncope
- Severe infection/Sepsis
- Hypoglycemia
- Periodic paralysis (electrolyte disturbance, K, Mg, Ca)
- Respiratory failure
- Emergent Diagnoses:
- Symptomatic Anemia
- Severe dehydration
- Hypothyroidism
- Polypharmacy
- Malignancy
- Aortic disease - occlusion, stenosis, dissection
- Other causes of weakness and paralysis
- Acute intermittent porphyria (ascending weakness)
- Can't miss diagnoses:
Evaluation
Workup
On all patients:
- CBC (anemia)
- Chem 10 (electrolyte disturbance, hypoglycemia, uremia, cardiac enzymes)
- ECG (Ischemia, hypo/hyperkalemia)
Consider:
- CK (myopathies)
- Thyroid studies
- ESR
- 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)
Management
Intubation Indications
- Severe fatigue
- Inability to protect airway
- Rapidly increasing PaCO2
- Hypoxemia despite O2
- FVC <12 mL/kg
- Neg Insp Force <20 cm H2O
Disposition
- Depends on process
- If normal initial workup, make sure has no respiratory compromise