Myasthenia Gravis: The Clinical Pattern Every Healthcare Professional Needs to Recognise

By Dr Will Bierrum, Neurology Registrar and Founder of Medxstart

Myasthenia gravis gets missed. Not because it is rare, but because its presentation is subtle, fluctuating and easy to attribute to something else. Fatigue. Stress. Poor sleep. By the time the diagnosis is made, patients have often been symptomatic for months or longer. The good news is that once you know the pattern, it becomes much more recognisable.

The Look

Picture a patient who looks exhausted. Both eyelids are drooping, though one side may be worse than the other. They tell you they keep seeing two of things, especially when they’re watching the TV towards the end of the day. That fatiguable nature is your first clue.

The Pattern

Myasthenia gravis causes fatigable, fluctuating weakness. The hallmark features are bilateral ptosis, which can be asymmetrical, and diplopia. But the finding that should immediately direct your pattern recognition is that the pupils are normal.

Normal pupils in the presence of ptosis and diplopia should make you think of myasthenia. A compressive third nerve palsy will almost always involve the pupil. If the pupil is spared, you need a different diagnosis.

One bedside test that is easy to overlook is neck flexion strength. Always test it. Neck flexor weakness is a surrogate marker for diaphragmatic weakness in neuromuscular conditions and gives you valuable early information about respiratory reserve before the patient becomes breathless.

The Bulbar Signs You Need to Ask About

Patients with bulbar involvement rarely volunteer these symptoms. You have to ask directly.

Ask about a nasal quality to the voice. Ask whether their voice fades during a long conversation or phone call. Ask whether they struggle to chew through a full meal. Ask whether liquid has ever come out of their nose when drinking.

That last symptom, nasal regurgitation, is a sign of significant soft palate weakness and should prompt urgent assessment. For practical information and support for patients, Myaware is the leading UK myasthenia charity and an excellent resource.

The Steroid Trap

Corticosteroids are effective in myasthenia gravis but initiating them carries a recognised risk. Starting steroids can make myasthenia worse before it gets better. This phenomenon, known as the steroid dip, can occur in the first one to three weeks after starting treatment.

High dose steroids are often initiated in hospital where the patient can be monitored for respiratory deterioration or worsening bulbar symptoms. If starting as an outpatient, the principle is to start low and go slow. If your patient deteriorates shortly after starting steroids, consider this diagnosis.

The Drugs That Make It Worse

Before prescribing any new medication to a patient with known myasthenia gravis, review the list of exacerbating drugs.

High risk classes include:

• Antibiotics: Macrolides, fluoroquinolones and aminoglycosides.

• Cardiovascular: Beta blockers and calcium channel blockers.

• More broadly: Statins, magnesium and immune checkpoint inhibitors.

If your patient with myasthenia deteriorates, always review their drug chart and recent medication history.

Managing the Crisis

A myasthenic crisis is life threatening. The key monitoring mistake is relying on oxygen saturations. In neuromuscular respiratory failure, saturations drop late, often when the clinical situation is already critical.

Monitor forced vital capacity sitting and lying. An FVC below 20ml per kg or a downtrending FVC is an indication to consider early ITU referral. Practice varies between centres so discuss early with your senior and critical care colleagues. Acute crises are treated with intravenous immunoglobulin or plasma exchange.

The Pattern That Matters

Myasthenia gravis requires a systematic approach and the signs can be subtle. Bilateral fatigable ptosis. Normal pupils. Neck flexor weakness as a window into respiratory function. Bulbar symptoms that patients may not tell you about unless you ask.

If you want to develop this kind of systematic approach to neurology, my Neurology Pattern Recognition Guide is available now at medxstart.co.uk. It is designed for all healthcare professionals who want to feel more confident seeing neurology patients in their clinical practice.

Dr Will Bierrum is a neurology registrar and founder of Medxstart, the success platform for modern doctors. medxstart.co.uk

This post is for educational purposes only. It does not constitute clinical guidelines or medical advice. Always refer to local guidelines and senior colleagues when making clinical decisions.