Case Report ABSTRACTS

Ocular myasthenia gravis mimicking brainstem stroke
Karol Biegus
Wycombe General Hospital
Amulya Misra
Case Report
This 82 year old lady was referred urgently to the high risk TIA clinic by her Ophthalmologist after she
presented to him with a two week history of acute deterioration in vision in her left eye, diplopia and left
sided ptosis. She had previously seen him for left eye Age-related Macular Degeneration and her vision
impairment was attributed to this. Her other past medical history included hypertension, peripheral vascular
disease, abdominal aortic aneurysm and hypothyroidism.
On examination in the TIA clinic this patient had diplopia on upward, left and downward gaze with
normalisation of the image on covering her left eye. She also had marked ptosis and decreased visual
acuity in the left eye. Examination of the right eye was normal. Both pupils were equal and reactive to light.
The remainder of the cranial nerve examination was normal. She also had normal power and sensation in all
limbs.
Routine blood tests were unremarkable. MRI brain showed no restricted diffusion to indicate recent infarct.
There was only mild generalised involutional and periventricular white matter change. A CT of the orbits
showed no abnormality. Anti-acetylcholine receptor antibodies came back significantly raised.
This patient has ocular myasthenia gravis but remains at risk of the generalised form. Myasthenia gravis is a
under-recognised condition, especially in the elderly. In the context of sudden onset unilateral signs and
the absence of a clear history of fatigability it can easily be misdiagnosed as a stroke, especially in the acute
setting. Considering this important differential diagnosis in your patients with suspected brainstem stroke
could save them from significant morbidity.