Makindo Medical Notes.com

Typically a descending paralysis from eyes and bulbar muscles to proximal to distal limbs with dilated pupils due to blockage of Ach release at motor endplate

About

• Infectious disease leading to weakness and paralysis
• There is a lack of Ach at the neuromuscular junction
• Affects smooth and skeletal muscles

Aetiology

• Exotoxin produced by anaerobic gram-positive spore-forming Clostridium tetani
• Organism found in the environment e.g. soil
• Toxin binds irreversibly to presynaptic terminal
• Toxin is internalised and cleaves neuroexocytosis of Ach
• This prevents Ach release

Methods of getting botulism

• Poorly preserved or canned food
• Honey ingestion in children. Spores enter the gut and colonise due to lack of normal flora
• Wound - spores in air germinate in the wound under anaerobic conditions and release toxins. IV Drug users with infected abscesses
• Adult botulism - seen in those with GI surgery or other abnormalities

Clinical

• Rapid onset weakness 2-36 hours after ingestion
• Weakness from top to bottom and proximal to distal
• Bulbar symptoms - Diplopia (III,IV,VI), dysarthria, dysphagia
• Autonomic involvement - hypotension, nausea, diarrhoea or constipation, dilated pupils
• Progressive weakness from cranial nerves to upper limbs, respiratory and then lower limbs
• Paediatrics - floppy baby with constipation

Differential

• Myasthenia Gravis is the most difficult differential (pupils unaffected in MG)
• Guillain-Barré syndrome - consider GBS if the sensory loss
• LEMS, Diphtheria, Miller - Fisher syndrome, Shell fish
• Organophosphate poisoning

Investigations

• FBC, U&E, Arterial Blood gases, Toxicology screen, CXR
• Botulinum toxin in stool and blood
• Nerve conduction studies - reduced amplitude and increased amplitude with repeated stimulation

Management

• Give Botulinum Antitoxin stat reduces mortality from 46% to 10%
• Respiratory weakness requires intubation and ventilation
• Supportive intensive care. Gastric lavage of ingested food can be considered
• Enema - avoid Magnesium based as can enhance toxin
• Antibiotics

Prognosis

• Worse with Type A toxin - more severe course and higher mortality
• Recovery takes months - grow new presynaptic endplates and NM Junctions
• Eventual recovery should be complete