Differential Diagnosis for Flaccid Quadriparesis

Primary Diagnostic Categories

• Guillain-Barré syndrome (GBS) is the most common cause of acute flaccid quadriparesis, characterized by ascending bilateral symmetric weakness progressing from legs to arms to cranial nerves, with areflexia or hyporeflexia in affected limbs 1, 2
• GBS subtypes include acute inflammatory demyelinating polyneuropathy (AIDP), acute motor axonal neuropathy (AMAN), and acute motor-sensory axonal neuropathy (AMSAN) 3
• Chronic inflammatory demyelinating polyneuropathy (CIDP) with acute onset can mimic GBS 4, 3
• Diphtheria-associated polyneuropathy and Lyme borreliosis can cause polyradiculoneuritis 4
• Botulism presents with descending flaccid paralysis starting with cranial nerves, then trunk, then extremities, with preserved or normal reflexes and no sensory involvement 1, 2
• Lambert-Eaton myasthenic syndrome should be considered in the differential 4
• Hypokalemic periodic paralysis (including thyrotoxic variant) presents with jaw-opening weakness in a significant proportion of cases and is more common in low-income settings 4
• Acute rhabdomyolysis and drug-induced toxic myopathy (from colchicine, chloroquine, emetine, or statins) can cause flaccid quadriparesis 4, 3
• Critical illness polyneuropathy or myopathy is a consideration in critically ill patients 4
• Acute transverse myelitis from infectious causes can cause flaccid quadriparesis 4
• Acute flaccid myelitis associated with enteroviruses (D68, A71), arthropod-borne viruses (Zika, chikungunya, West Nile), rabies, or polio can present with flaccid weakness 5, 4
• CMV polyradiculomyelopathy in HIV patients causes Guillain-Barré-like syndrome with urinary retention, progressive bilateral leg weakness, flaccid paraplegia, and CSF neutrophilic pleocytosis 6
• Spinal cord compression or cauda equina syndrome can cause flaccid quadriparesis 4
• Electrolyte disorders, such as hypokalaemia, hypophosphataemia, and hypermagnesaemia, can cause weakness 4, 3
• Vitamin deficiencies, including B1 (beriberi, Wernicke encephalopathy), B12 (subacute combined degeneration), and vitamin E, can cause neurological symptoms 4, 3
• Organophosphate poisoning, heavy metal toxicity (lead, thallium, arsenic), and porphyria are potential causes of flaccid quadriparesis 4
• Tetanus (Clostridium tetani) and botulism (C. botulinum) can cause flaccid paralysis 4
• Polio in regions where it has not been eradicated (sub-Saharan Africa, Pakistan) is a consideration 4
• Rabies in endemic areas can cause flaccid paralysis 4
• Brainstem or meningoencephalitis can present with flaccid weakness 5, 4
• Brainstem stroke or vasculitis can cause flaccid quadriparesis 4, 3
• Leptomeningeal metastases or neurolymphomatosis can cause neurological symptoms 4, 3
• Mitochondrial disease can cause a range of neurological symptoms, including weakness 4, 3
• Functional or conversion disorder can present with weakness or paralysis 4

Critical Distinguishing Features

• Ascending pattern of weakness (legs → arms → cranial nerves) suggests GBS 1, 2
• Descending pattern of weakness (cranial nerves → trunk → extremities) suggests botulism 1, 2
• Areflexia or hyporeflexia strongly suggests GBS, though reflexes can be normal initially 1, 2
• Normal or preserved reflexes indicates botulism or myasthenia gravis 1
• Distal paresthesias or sensory loss is typical in GBS but absent in botulism 2
• No sensory symptoms suggests botulism, myasthenia gravis, or pure motor disorders 2
• Alert and oriented mental status is characteristic of botulism despite appearing intoxicated from ptosis and dysarthria 2
• Altered consciousness suggests encephalitis, stroke, or metabolic encephalopathy rather than peripheral causes 5

Geographic and Demographic Variations

• Organophosphate intoxication, botulism, rabies, polio, and tetanus occur more frequently in low- and middle-income countries 4
• Hypokalaemic thyrotoxic periodic paralysis is more common in certain geographic regions 4
• Infections with HIV, HTLV-1, and arthropod-borne viruses (Zika, chikungunya, West Nile) are frequently reported in several low-income countries 4

Common Pitfalls to Avoid

• Do not dismiss GBS based on normal initial electrodiagnostic studies, as changes may not appear until 10-14 days after symptom onset 1
• Do not wait for CSF protein elevation before initiating treatment for suspected GBS 2
• Botulism is frequently misdiagnosed as myasthenia gravis, stroke, or psychiatric disorders, with 34% presenting with only 1-2 cranial nerve palsies initially 2
• Facial paralysis in botulism can mask respiratory distress by producing a placid expression and preventing nasal flaring 2