Why these emergencies matter
Neuromuscular emergencies can progress quickly to respiratory failure, and the Neurology SCE often tests whether you recognise the warning signs and know the correct monitoring and treatment. Myasthenic crisis and Guillain-Barré syndrome are the two conditions you are most likely to meet.
Monitoring breathing: the key principle
In both conditions, oxygen saturation and blood gases can remain normal until very late. Serial forced vital capacity measurements, alongside assessment of bulbar function, cough and neck flexion strength, give earlier warning of respiratory muscle weakness. A falling vital capacity should prompt early discussion with critical care. In the exam, an option that relies on pulse oximetry alone to monitor these patients is usually wrong.
Myasthenia gravis and myasthenic crisis
Myasthenia gravis causes fatigable weakness, often starting with ptosis and diplopia. Most patients with generalised disease have antibodies to the acetylcholine receptor, and a smaller group have antibodies to muscle-specific kinase. CT of the chest is needed to look for a thymoma, and thymectomy is considered for selected patients with generalised disease.
A myasthenic crisis is respiratory or bulbar weakness severe enough to need ventilatory support. Common triggers include infection, surgery and certain medicines. Many drugs can worsen myasthenia, including aminoglycosides, fluoroquinolones, macrolides, magnesium, beta blockers and some anaesthetic agents. Treatment of a crisis includes airway and ventilatory support, treating the trigger, and intravenous immunoglobulin or plasma exchange, with longer-term immunosuppression guided by the specialist team.
Guillain-Barré syndrome
Guillain-Barré syndrome typically causes progressive, relatively symmetrical weakness with reduced or absent reflexes, often after a respiratory or gastrointestinal infection. Sensory symptoms, back pain and autonomic instability are common. Nerve conduction studies and cerebrospinal fluid examination, which often shows raised protein with a normal cell count, support the diagnosis. Treatment is intravenous immunoglobulin or plasma exchange. Corticosteroids are not effective and should not be chosen in exam questions about treatment.
Autonomic and supportive care
Patients with Guillain-Barré syndrome can develop arrhythmias and blood pressure instability, so cardiac monitoring is important. Thromboprophylaxis, pain management, swallowing assessment and early rehabilitation all form part of good care, and these practical points often appear in answer options.
Exam tips
Look for a recently prescribed antibiotic in a patient with known myasthenia who deteriorates. Choose vital capacity over saturations for monitoring. For Guillain-Barré syndrome, remember that immunoglobulin or plasma exchange works and steroids do not.
Practise with License Medical
The License Medical Neurology SCE question bank includes exam-style Best of Five questions on this topic and across the curriculum, each with a guideline-based explanation. Start revising at license-medical.com/question-bank-details/neurology-sce/.