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Limb Weakness

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📖 Introduction

Limb weakness is a common but broad clinical presentation, arising from neurological, muscular, spinal, metabolic, or systemic causes. A systematic approach is vital: ⚡ onset (sudden vs gradual), ⏳ duration, pattern (proximal vs distal), and associated features (sensory loss, pain, systemic illness). Early recognition of emergencies such as stroke, spinal cord compression, or Guillain-Barré syndrome can be life-saving.

📝 History

Onset: ⚡ Sudden (stroke, spinal cord infarct), ⏳ gradual (MND, muscular dystrophy), 🌀 episodic (myasthenia gravis).
Duration: Acute vs chronic → important diagnostic clue.
Associated Symptoms:
- 🌡️ Fever, weight loss → infection, malignancy.
- 🔌 Sensory disturbance → neuropathy/spinal lesion.
- 🔥 Pain → radiculopathy, inflammatory myopathy.
Pattern: Proximal 🦵 weakness → myopathy/metabolic. Distal ✋ weakness → neuropathy/MND.
Precipitating Events: Recent infection (GBS), drugs (statins, steroids), toxins (alcohol, chemotherapy).
Family History: Neuromuscular disorders, muscular dystrophy, inherited neuropathies.

🩺 Examination

Strength: Grade using MRC scale 0–5.
Reflexes: ↑ = UMN lesion; ↓/absent = LMN lesion.
Muscle bulk & tone: Wasting, fasciculations (MND), spasticity (UMN).
Coordination: Ataxia, dysmetria → cerebellar involvement.
Gait:
- Foot drop 👣 → peroneal neuropathy/MS.
- Waddling gait 🐧 → proximal myopathy.
- Spastic gait 🧍‍♂️ → UMN lesion.

🧾 Common Causes

Neurological: Stroke, multiple sclerosis, MND, peripheral neuropathy, GBS.
Muscular: Muscular dystrophies, myositis, metabolic myopathies.
Spinal cord: Compression, trauma, transverse myelitis.
Autoimmune: Myasthenia gravis, SLE, dermatomyositis.
Metabolic/Endocrine: Hypokalaemia, thyroid disorders, diabetes, Cushing’s.
Toxins/Drugs: Alcohol, statins, steroids, chemotherapy (vincristine).

🔎 Investigations

Bloods: CBC, U&E, CK, thyroid function, autoimmune screen, glucose, B12.
Neuroimaging: CT/MRI brain/spine for stroke, compression, demyelination.
Electrophysiology: Nerve conduction studies, EMG.
CSF: Oligoclonal bands (MS), albuminocytologic dissociation (GBS).
Muscle Biopsy: For myopathies and dystrophies.

📊 Causes of Limb Weakness

Cause	Description	Clinical Features	Key Tests	Management
Stroke (CVA) ⚡	Acute ischaemia or haemorrhage in the brain.	Sudden hemiparesis, facial droop, dysphasia, visual loss.	CT/MRI brain, carotid Doppler, ECG (AF).	Thrombolysis/thrombectomy, antiplatelets, BP control, rehab.
Multiple Sclerosis 🧩	Autoimmune demyelination of CNS.	Episodic weakness, optic neuritis, sensory loss, ataxia.	MRI brain/spine, CSF oligoclonal bands.	Immunomodulators, steroids for relapse, physio.
Guillain-Barré Syndrome 🌀	Acute post-infectious demyelinating polyneuropathy.	Ascending symmetrical weakness, areflexia, ± resp failure.	NCS/EMG, LP (↑ protein, normal cells).	IVIG or plasmapheresis, ITU if severe.
Myasthenia Gravis 🎯	Autoimmune blockade at neuromuscular junction.	Fluctuating weakness, ptosis, diplopia, bulbar symptoms.	AChR antibodies, EMG, CT chest (thymoma).	Pyridostigmine, immunosuppression, thymectomy.
Peripheral Neuropathy 🔌	Axonal or demyelinating damage, often diabetic.	Stocking–glove weakness, numbness, pain, areflexia.	NCS/EMG, B12, glucose, TFTs.	Control cause (e.g. diabetes), neuropathic pain meds, physio.
Amyotrophic Lateral Sclerosis (ALS) 🧠	Degenerative UMN + LMN disease.	Progressive weakness, fasciculations, dysarthria, no sensory loss.	EMG (denervation), MRI to exclude mimics.	Riluzole, supportive care, ventilatory support.
Spinal Cord Compression 🦴	Compression from tumour, abscess, disc, or trauma.	Weakness below lesion, sensory level, sphincter dysfunction.	MRI spine, CT if contraindicated.	Steroids, urgent neurosurgery/oncology.
Myopathies (e.g. polymyositis, dystrophy) 💪	Muscle fibre damage, autoimmune or inherited.	Proximal weakness, rash (dermatomyositis), raised CK.	CK, EMG, biopsy, autoantibodies.	Steroids, immunosuppression, physio.
Metabolic/Endocrine ⚖️	Electrolyte or hormonal disorders.	Hypokalaemia → flaccid weakness; thyroid disease; Cushing’s.	Electrolytes, TFTs, cortisol.	Correct underlying imbalance; hormone therapy.

💡 Clinical Pearls

⚡ Sudden unilateral weakness = stroke until proven otherwise.
🌀 Ascending symmetrical weakness = Guillain-Barré.
🎯 Fluctuating fatigable weakness = myasthenia gravis.
🧠 No sensory involvement = suspect motor neuron disease.
🦴 Back pain + weakness + sphincter issues = spinal cord compression → neurosurgical emergency.

PLEASE NOTE LEGAL ADVICE: The contents are under continuing development and improvements and may contain errors of omission or fact. Feedback vital and always welcome at drokane at gmail.com. This is not to be used for the assessment, diagnosis or management of patients. It should not be regarded as medical advice. It is only for educational purposes. Please adhere to your local protocols. If you are unwell please seek healthcare advice from your doctor. This does not replace senior or specialist advice. If you do not accept this then please do not use the website. If you need medical advice, please consult a doctor or other appropriate medical professional. If you are a medical professional and you need advice then speak to your senior or colleagues.

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