A 38-year-old male presented initially with impaired
vision of 6 hours duration. He had been bumping into objects, had been unable
to see complete faces and had difficulty reading. No history of headache, neck
pain or trauma. He gave a history of attacks of migraine with aura and had
sensorineural deafness. His mother aged 65 has non-insulin dependent diabetes
mellitus and his father has ischaemic heart disease. He was not homosexual.
On examination the positive findings were he was shorter
than average, had sensorineural deafness and had a left homonymous hemianopia.
There was no abnormality on examination of the cardiovascular system. No other
positive findings.
Investigations showed normal haematology and
biochemistry, coagulation screen was normal, ECG, transthoracic
echocardiogram, chest x-ray were normal. CT scan of his head showed
low-density changes in the right parieto-occipital region.
His hemianopia resolved within 72 hours, he was treated
with aspirin and discharged.
8 months later he was re-admitted with a right-sided
weakness and right homonymous hemianopia. MRI showed ischaemic changes in the
both parieto-occipital regions and ischaemic changes in the left
tempero-parietal region.
Which of the following would confirm your diagnosis:
a)
Transoesophageal echocardiography
b)
Homocysteine levels in blood
c)
Visual evoked potentials
d)
Lumbar puncture
e)
Muscle biopsy
Answer: e)
The patient has MELAS (myopathy, encephalopathy, lactic
acidosis, stroke like episodes). Muscle biopsy showed ragged red, succinate
dehydrogenase positive and cytochrome oxidase positive and negative fibres.
The diagnosis was confirmed by genetic analysis.
MELAS is a mitochondrial disorder, which results in
defective oxidative phosphorylation. The features are short stature, limb
myopathy, seizures, episodes of lactic acidosis and stroke like episodes. The
strokes do not usually conform to vascular territories and the
parieto-occipital lobes are commonly affected. Patients have high
lactate/pyruvate levels in blood and CSF.
Other features are non-insulin dependent diabetes
mellitus and sensori-neural deafness. Migraine with aura is also a
feature
Revision Tip
Revise mitochondrial myopathies
ACES for PACES page 437
