Ocular myashenia gravis (OMG) occurs less then generalized myasthenia (in 80 % all cases).. Weakness may be limited to the muscles of the eye. The most common symptoms are ptosis (eyelid drooping ) or diplopia (double vision).Do you feel comfortable to stare at the girls eyes in the picture on the right? Patients with diplopia have similar difficulties. OMG is characteristically variable in course, worsen with emotional and physical factors such as bright sunlight, stress, viral illness, menstruation, pregnancy, etc. The symptoms often get worse in the evening while with rest and closed eyes, the patient's condition gets better.
OMG develops very unobtrusively, symptoms occur for a few days, then disappear and then appear again a few month or year later but with smaller chance to spontaneous remission. About 80% of MG patients eventually have eye involvement (50% as very first symptom). Within 2 years, 80% of patients with ocular onset of MG will progress to involve other muscle groups, thereby developing generalized MG. The other 20% of patients continue to have purely ocular MG. If MG is confined to the ocular muscles for more than 3 years, there is a 94% likelihood that the symptoms will not worsen or generalize.Diagnostics is based on clinical examination. Each fluctuating extraocular disorder, which also does not fit the classic image of a disability oculomotors nerves is suspected of OMG. Diseases rather imitates internuclear palsy, which is a disorder of the brain stem. Ptosis is usually asymmetrical, even initially unilateral, diplopia may also be initially only in pohedu one direction. Pupils and their responses to light are normal.
Clinical examination in pictures
1/ Examinatin in idle state
2 / mobility testing bulbs at eye views in all directions
Passive lifting eyelids. In view of the right shows the patient diagonal diplopia, indicated a slight right globe pouring down
Looking to the left. The patient shows a horizontal diplopia. Left bulbus in paretic slightly medial (inside).
Looking up, the patient does not indicate diplopia, symmetric movement bulbs.
3/ Clinical Test:
a/ Simpson´s test
Provocation ptosis looking up (activating m. frontalis
A / patient is barely noticeable ptosis on the left. B / After 20 sec. ptosis left already evident, C / After 30 sec.
D / After 40 sec. ptosis left pupil is almost obscured, E / 50 sec. pupil is no longer visible, F / 60 sec. eye slit almost expired.
b / Gorelick´s test
Passive lift lid with greater ptosis (right) almost as soon as the lid falls on the other hand (left)
c/ Cogan lid twitch test
Patient with almost complete ptosis with hard looks down 20 sec (A). Followed by improvement of ptosis, right upper eyelid pseudoretrakce (B). Status after 20 sec. (C) and 60 sec (D).
d/ Ice pack test"
After the application of ice cubes wrapped in gauze in the lid ptosis occurs after 60 to 120 sec to lift it.
e/ Tension test
f/ Sleep test
Laboratory test and their sensitivity
|
Examination |
OcuLAR form |
Generalised form |
|
Antibodies antiAChr |
85% |
50% |
|
Repetitive stimulation |
45% |
94% |
|
SF EMG |
96% |
99% |
|
Thymoma |
5% -8% |
15% |
Treatment
Patients with OMG are usually treated initially with oral anticholinesterase agents, Mestinon. This treatment is often unsuccessful in 70-80% patients, therefor is considered immunosupressive treatment (initially 10mg for 5days, then 30-40mg alternate days for 6-8weeks and then again decrease dose to 5-10mg alternate days).There is necessary to consider risk of treatment in older patients with isolated ptosis.Plasmapheresis or IVIG are not effective.There is not prove that the thymectomy is effective in patients with OMG. The already-long ptosis without impairing fluctuations blefaroplastic recommend that you perform, provided that no diplopia (animation). Lighter form of diplopia can be solved prismatickymi glasses. Glasses with unilateral occlusion are usually well tolerated for the loss of spatial vision.