Acute Non-Traumatic Weakness
Reviewed and revised 13 April 2016
OVERVIEW
Acute non-traumatic weakness may occur as a result of a wide variety of underlying etiologies, many of which are life-threatening
- Key considerations include:
- assessment of the need for intubation and respiratory support
- identification of time-critical emergencies
- determination of the underlying cause, based on clinical assessment and investigations, including a careful physical examination to facilitate neurological localisation and diagnosis
FACTORS TO CONSIDER IN THE DECISION TO INTUBATE
General
- Increasing generalized muscle weakness
- Dysphagia
- Dysphonia
- Dyspnea on exertion and at rest
Subjective
- Rapid shallow breathing
- Tachycardia
- Weak cough
- Interrupted speech (gasping for air)
- Use of accessory muscles
- Abdominal paradoxical breathing
- Orthopnea
- Weakness of trapezius and neck muscles: inability to lift head from bed
- Inability to perform single-breath count: count from 1 to 10 in single exhalation (roughly equal to FVC <1.0 L)
- Cough after swallowing
Objective
- Decreased level of consciousness (have a lower threshold to control the airway if patient requires transfer or movement to unmonitored areas)
- Hypoxemia
- Vital capacity <1 L or 20 mL/kg, or 50 % decrease in VC in a day
- Maximum inspiratory pressure >-30 cm H2O
- Maximum expiratory pressure <40 cm H2O
- Hypercapnia (occurs late)
Base the decision to intubate on a global overview of the above factors – not any single parameter – and take into account the time course and anticipated trajectory of illness
- reassess the patient frequently
- intervene before the onset of hypercapnia if possible
IMMEDIATELY LIFE-THREATENING CAUSES
These include:
- stroke syndromes
- aortic dissection
- CNS infections
- spinal cord syndromes
- seizure disorders
- envenoming (e.g. snake)
- acute toxicity e.g. organophosphates, heavy metals
- electrolyte/ metabolic disorders
DIFFERENTIAL DIAGNOSIS
Overview
- Myopathic – rhabdomyolysis, ischaemic, congenital, CIW
- NMJ – myasthenia gravis, botulism
- Neuropathic – GBS, CIW, polio
- Spinal Cord – infarct, infection, tumour
- Brain stem – haemorrhage, infarct, infection, mass lesion
- Brain – haemorrhage, infarct, infection, tumour
- Systemic – organ failures, electrolytes, sepsis, toxins
Hemiparesis
- Acute stroke: ischemic, hemorrhagic, or subarachnoid hemorrhage
- Intracranial mass
- Meningitis/encephalitis
- Hypoglycemia/hyperglycemia
- Postictal Todd’s paresis
- Hemiplegic migraine
- Brown-Sequard syndrome
Quadriparesis/Paraparesis ± Sensory Level
- Spinal cord compression
- Spinal cord infarction
- Transverse myelitis
Proximal Weakness
- Acute myopathy
- Guillain–Barré syndrome (GBS)
- Diabetic lumbosacral radiculoplexus neuropathy (DLRN)
- Myasthenia gravis
- Lambert-Eaton myasthenic syndrome (LEMS)
Distal Weakness
- Vasculitic neuropathy
- Toxin induced peripheral neuropathy
- Nerve compression syndromes
Any severe medical illness may have weakness as a presenting symptom, and psychiatric diagnoses may also mimic neuromuscular disorders
ASSESSMENT
Clinical assessment
- Relevant history
- Examination
- systemic features
- neurological examination (see neurological localisation, below)
Investigations
- Laboratory
- glucose, electrolytes, Ca, Mg, PO4, UEC, LFTs, and coags
- TFTs, CK, ESR
- others according to suspected etiology: e.g. CSF, vasculitis screen
- Imaging (according to suspected etiology)
- CTB, CTB +/- contrast +/- angiogram +/- venogram
- MRI brain +/- angiography
- CT or MRI spine
NEUROLOGICAL LOCALISATION BASED ON PHYSICAL EXAMINATION
1 | 2 | 3 | 4 | 5 |
---|---|---|---|---|
Localisation | Pattern of weakness | Sensory loss | Reflexes | Acute causes |
Cerebral cortex, brainstem, or spinal cord | Distal > proximal, extensors > flexors, hemiparesis or single limb | May be present depending on whether sensory tracts or cortex are involved | Increased (may be decreased initially) | Acute stroke, SAH, seizure, hypertensive encephalopathy |
Spinal cord | Distal > proximal, extensors > flexors, paraparesis, quadriparesis, rarely hemiparesis | Increased (may be decreased initially) | Epidural abscess, tumor, spinal cord infarct | |
Anterior horn cell | Proximal and distal, fasciculations are prominent | absent | Decreased if muscle bulk is severely decreased; increased in ALS | ALS, polio |
Peripheral nerve | In the distribution of the nerve, or diffusely present as stocking/glove weakness | Present | Decreased | Guillain-Barre Syndrome |
Neuromuscular junction | First in eye muscles, neck extensors, pharynx, diaphragm, followed by more generalized weakness | Absent | Normal, decreased if muscle is paralyzed | Botulism, tick bite, organophosphates |
Muscle | Proximal | Absent | Normal unless muscle severely weak | Rhabdomyolysis |
- However, in the acute phase, UMN lesions may be difficult to differentiate from a LMN lesion
- acute UMN lesions may result in flaccid paralysis, normal or reduced tone, and unreliable reflexes
- in acute LMN lesions there may be insufficient time for atrophy to be evident and fasciculations are rarely seen
MANAGEMENT
Airway and respiratory management
- Assess for intubation (see factors to consider, above)
- key life threats are:
- airway obstruction due to oropharyngeal collapse
- respiratory failure due to diaphragmatic weakness
- respiratory failure due to aspiration from inadequate airway protection
- key life threats are:
- Non-invasive ventilation
- Consider as a temporizing measure in a neurologically stable patient with a neuromuscular condition expected to have rapid resolution (e.g., myasthenia gravis exacerbation)
- Consider use for pre-oxygenation prior to intubation
- Avoid suxamethonium if there is evidence of underlying progressive neuromuscular disease (e.g., Guillain-Barre Syndrome, chronic muscular weakness, or prolonged immobility) — use rocuronium (1.2 mg/kg IV IBW) for rapid sequence intubation
- Myasthenia gravis
- Succinylcholine is relatively ineffective, double the standard dose if used (e.g. 3 mg/kg IV)
- Alternatively, use half-dose of non-depolarizing agents (e.g. rocuronium 0.6 mg/kg IV IBW)
- If autonomic instability is present or anticipated
- Prepare atropine/glycopyrrolate, fluids, and vasopressors prior to intubation
- anticipate swings and avoid overshoot (i.e. don’t chase hypotension too aggressively with vasopressors, as there may be a dramatic swing to severe hypertension as a result of autonomic instability)
Specific therapy
- according to underlying cause
Supportive care and monitoring
References and Links
CCC Neurocritical Care Series
Emergencies: Brain Herniation, Eclampsia, Elevated ICP, Status Epilepticus, Status Epilepticus in Paeds
DDx: Acute Non-Traumatic Weakness, Bulbar Dysfunction, Coma, Coma-like Syndromes, Delayed Awakening, Hearing Loss in ICU, ICU acquired Weakness, Post-Op Confusion, Pseudocoma, Pupillary Abnormalities
Neurology: Anti-NMDA Encephalitis, Basilar Artery Occlusion, Central Diabetes Insipidus, Cerebral Oedema, Cerebral Venous Sinus Thrombosis, Cervical (Carotid / Vertebral) Artery Dissections, Delirium, GBS vs CIP, GBS vs MG vs MND, Guillain-Barre Syndrome, Horner’s Syndrome, Hypoxic Brain Injury, Intracerebral Haemorrhage (ICH), Myasthenia Gravis, Non-convulsive Status Epilepticus, Post-Hypoxic Myoclonus, PRES, Stroke Thrombolysis, Transverse Myelitis, Watershed Infarcts, Wernicke’s Encephalopathy
Neurosurgery: Cerebral Salt Wasting, Decompressive Craniectomy, Decompressive Craniectomy for Malignant MCA Syndrome, Intracerebral Haemorrhage (ICH)
— SCI: Anatomy and Syndromes, Acute Traumatic Spinal Cord Injury, C-Spine Assessment, C-Spine Fractures, Spinal Cord Infarction, Syndomes,
— SAH: Acute management, Coiling vs Clipping, Complications, Grading Systems, Literature Summaries, ICU Management, Monitoring, Overview, Prognostication, Vasospasm
— TBI: Assessment, Base of skull fracture, Brain Impact Apnoea, Cerebral Perfusion Pressure (CPP), DI in TBI, Elevated ICP, Limitations of CT, Lund Concept, Management, Moderate Head Injury, Monitoring, Overview, Paediatric TBI, Polyuria incl. CSW, Prognosis, Seizures, Temperature
ID in NeuroCrit. Care: Aseptic Meningitis, Bacterial Meningitis, Botulism, Cryptococcosis, Encephalitis, HSV Encephalitis, Meningococcaemia, Spinal Epidural Abscess
Equipment/Investigations: BIS Monitoring, Codman ICP Monitor, Continuous EEG, CSF Analysis, CT Head, CT Head Interpretation, EEG, Extradural ICP Monitors, External Ventricular Drain (EVD), Evoked Potentials, Jugular Bulb Oxygen Saturation, MRI Head, MRI and the Critically Ill, Train of Four (TOF), Transcranial Doppler
Pharmacology: Desmopressin, Hypertonic Saline, Levetiracetam (Keppra), Mannitol, Midazolam, Sedation in ICU, Thiopentone
MISC: Brainstem Rules of 4, Cognitive Impairment in Critically Ill, Eye Movements in Coma, Examination of the Unconscious Patient, Glasgow Coma Scale (GCS), Hiccoughs, Myopathy vs Neuropathy, Neurology Literature Summaries, NSx Literature Summaries, Occulocephalic and occulovestibular reflexes, Prognosis after Cardiac Arrest, SIADH vs Cerebral Salt Wasting, Sleep in ICU
Journal articles
- Flower O, Bowles C, Wijdicks E, Weingart SD, Smith WS. Emergency neurological life support: acute non-traumatic weakness. Neurocrit Care. 2012 Sep;17 Suppl 1:S79-95. PMID: 22972018.
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
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