Stethopedia | Approach

Approach to

Weakness

Confirm true weakness, act first on sudden focal deficits, cord or cauda equina signs and failing breathing, then localize: brain, cord, horn/root/nerve, or junction and muscle by tempo, pattern, reflexes and sensation.

  1. Weakness: true loss of power, not fatigue or pain-limited effort
  2. Tempo, last known well; UMN vs LMN signs, pattern, sensory level, bulbar signs11
  3. Glucose, K, Ca, Mg, PO4, CK, ECG; serial VC and NIF if LMN, NMJ or bulbar5,11
  4. Stroke, cord or breathing threat?

Emergency: code stroke, spine MRI or ICU2,10,11

  • Sudden face, arm, speech deficit1
  • Sensory level, saddle loss, retention
  • VC <20 mL/kg or weak NIF5
  • Bulbar signs, dyspnea, weak cough
  • Rapid ascending weakness
  • Flaccid; peaked T or U waves

→ Stroke: glucose, CT + CTA; cord: stat MRI spine; failing VC: ICU2,10

If not: where is the lesion?

CausesCluesWorkupManagement

Brain (UMN)

  • Ischemic stroke
  • Intracerebral hemorrhage
  • Tumour, abscess, MS; Todd paresis
  • Face, arm or speech: any one, LR 5.51
  • Aphasia, neglect, field cut
  • Hemiparesis; brisk reflexes, Babinski
  • Glucose; CT rules out bleed; CTA for LVO2
  • MRI brain if CT unrevealing
  • ≤4.5 h: TNK 0.25 mg/kg (max 25 mg) or tPA2,3
  • LVO: thrombectomy ≤24 h by imaging2,12
  • BP ≤185/110 pre-lysis; ICH: reverse anticoag2,11

Spinal cord, cauda equina

  • Compression: tumour, abscess, bleed
  • Cauda equina syndrome
  • Myelitis, infarct, B12/copper, spondylosis
  • Sensory level or saddle loss; retention11
  • Back pain worse lying down; cancer10
  • Fever, injection drug use: abscess
  • Stat MRI whole spine with contrast10
  • B12, copper, HIV, syphilis; LP if myelitis
  • Tumour: dexamethasone; RT ± surgery10
  • Abscess: drainage, IV antibiotics
  • Neurosurgery or spine surgery now

Horn, root and nerve

  • Guillain-Barré syndrome
  • Polyneuropathy: DM, alcohol, B12
  • Radiculopathy, CIDP; ALS (UMN + LMN)
  • Ascending, areflexic after infection7
  • Atrophy, fasciculations, low tone
  • Radiating pain; distal sensory loss
  • LP: ↑protein; may be normal in wk 17
  • NCS/EMG; MRI if radicular; A1c, B12, SPEP11
  • mEGRIS: ventilation risk6,7
  • Can't walk ≤4 wk: IVIG 0.4 g/kg ×5 d or PLEX7
  • No corticosteroids for GBS7
  • Intubate: VC <20 mL/kg or >30% fall5

Junction and muscle

  • Myasthenic crisis, botulism
  • Hypo- or hyperkalemia; rhabdomyolysis
  • Myositis; statin or steroid myopathy
  • Fatigable ptosis, diplopia, dysphagia
  • Proximal, symmetric; sensation normal
  • Better with effort, dry mouth: LEMS
  • AChR, then MuSK Ab; CT chest8,11
  • EMG with repetitive stimulation
  • CK, K, TSH; review drugs
  • MG crisis: IVIG or PLEX, ICU; avoid FQs, AGs8,11
  • High K: Ca gluconate if ECG change; shift K9
  • Low K: replace on monitor; rhabdo: fluids

Can't-miss cause Superscripts link to the references below.

References

  1. Goldstein LB, Simel DL. Is this patient having a stroke? JAMA. 2005;293:2391–2402. PubMed 15900010
  2. Heran M, Lindsay P, Gubitz G, et al. Canadian Stroke Best Practice Recommendations: acute stroke management, 7th edition practice guidelines update, 2022. Can J Neurol Sci. 2024;51:1–31. PubMed 36529857
  3. Menon BK, Buck BH, Singh N, et al. Intravenous tenecteplase compared with alteplase for acute ischaemic stroke in Canada (AcT): a pragmatic, multicentre, open-label, registry-linked, randomised, controlled, non-inferiority trial. Lancet. 2022;400:161–169. PubMed 35779553
  4. Goyal M, Menon BK, van Zwam WH, et al. Endovascular thrombectomy after large-vessel ischaemic stroke: a meta-analysis of individual patient data from five randomised trials. Lancet. 2016;387:1723–1731. PubMed 26898852
  5. Lawn ND, Fletcher DD, Henderson RD, Wolter TD, Wijdicks EF. Anticipating mechanical ventilation in Guillain-Barré syndrome. Arch Neurol. 2001;58:893–898. PubMed 11405803
  6. Luijten LWG, Doets AY, Arends S, et al. Modified Erasmus GBS Respiratory Insufficiency Score: a simplified clinical tool to predict the risk of mechanical ventilation in Guillain-Barré syndrome. J Neurol Neurosurg Psychiatry. 2023;94:300–308. PubMed 36428088
  7. van Doorn PA, Van den Bergh PYK, Hadden RDM, et al. European Academy of Neurology/Peripheral Nerve Society guideline on diagnosis and treatment of Guillain-Barré syndrome. Eur J Neurol. 2023;30:3646–3674. PubMed 37814552
  8. Sanders DB, Wolfe GI, Benatar M, et al. International consensus guidance for management of myasthenia gravis: executive summary. Neurology. 2016;87:419–425. PubMed 27358333
  9. Lindner G, Burdmann EA, Clase CM, et al. Acute hyperkalemia in the emergency department: a summary from a Kidney Disease: Improving Global Outcomes conference. Eur J Emerg Med. 2020;27:329–337. PubMed 32852924
  10. Lawton AJ, Lee KA, Cheville AL, et al. Assessment and management of patients with metastatic spinal cord compression: a multidisciplinary review. J Clin Oncol. 2019;37:61–71. PubMed 30395488
  11. Gay E, Levy N, eds. Stroke & TIA; CNS Emergencies; Weakness & Neuromuscular Disease. In: Department of Medicine Housestaff Manual, 30th ed. 2024:196–198, 200.
  12. Heran MKS, Volders D, Lindsay MP, et al. Canadian Stroke Best Practice Recommendations: endovascular thrombectomy for acute ischemic stroke, interim update 2025. Can J Neurol Sci. 2025 Dec 4:1–6. doi:10.1017/cjn.2025.10444. PubMed 41340372

For education only; not a substitute for clinical judgment or local protocols. Where sources differ, the flowchart follows the current guideline.

Download slide (.pptx) Download PDF