ophthalmologic manifestations of myasthenia gravis

8/20/2019 Ophthalmologic Manifestations of Myasthenia Gravis

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Ophthalmologic Manifestations of

Myasthenia Gravis

• Author: Shady Awwad, MD; Chief Editor: Hampton Roy Sr, MD more...

Overview

Ninety percent of patients with myasthenia ra!is "M#$ de!e%op ophtha%mo%oic manifestations

of the disease, a disorder of neuromuscu%ar transmission characteri&ed 'y wea(ness and

fatia'i%ity of s(e%eta% musc%es. )he 'asic patho%oy of M# is a reduced num'er of acety%cho%ine

receptors "AChR$ at the postsynaptic musc%e mem'rane 'rouht a'out 'y an ac*uired

autoimmune reaction producin anti+AChR anti'odies.

)wo maor c%inica% forms of M# are distinuished: ocu%ar M#, in which the patient has strict%yocu%ar symptoms, and enera%i&ed M#, in which the patient de!e%ops enera%i&ed wea(ness. -ne

study found that, o!er a mean fo%%ow+up period of / years, appro0imate%y 1+/2 of patients

with M# had strict%y ocu%ar symptoms.

Some e!idence shows that steroids or a&athioprine miht pre!ent the con!ersion to enera%i&ed

M# in /12 of patients with ocu%ar M#.34

5e!er and cowor(ers reported that 672 of patients who %ater de!e%oped enera%i&ed wea(ness

did so in the first 7 years after dianosis.374 Hence, patients who (eep ha!in strict%y ocu%ar

symptoms for 8 or more years are un%i(e%y to re!ert to the enera%i&ed aspect of the disease.

)he u!eni%e form of the disease usua%%y has a much more fa!ora'%e pronosis than the adu%t

form, with a 'etter chance of spontaneous remission.

Patient History

Ophthalmic symptoms

Amon patients with myasthenia ra!is "M#$, /12 initia%%y comp%ain of ocu%ar distur'ance,

main%y ptosis and dip%opia. E!entua%%y, 92 of patients with M# de!e%op ocu%ar symptoms.

A'out 12 of patients wi%% present so%e%y with ocu%ar symptoms, and a'out 1+2 of these patients wi%% proress to de!e%op enera%i&ed disease. <tosis may 'e uni%atera% or 'i%atera%, and it

may shift from eye to eye.

Nonophthalmic symptoms

-ropharynea% musc%e distur'ances come second in presentation, with 12 of patients first

e0periencin difficu%ty in swa%%owin, ta%(in, and chewin. =im' and trun( wea(ness is the

http://emedicine.medscape.com/article/1171206-overview





initia% comp%aint of 2 of patients, and 612 of patients with M# de!e%op a enera%i&ed

wea(ness a%so affectin the %im' musc%es.

M# can in!o%!e the respiratory musc%es and %ead to respiratory fai%ure. )his can sometimes 'e

the first presentation of the disease. >ureshi et a% showed that out of 1 patients with M# and

respiratory fai%ure, / "?2$ had no pre!ious dianosis of M#.384

hysical Examination

Ptosis

As pre!ious%y stated, ptosis can 'e uni%atera% or 'i%atera%. )he ptosis is usua%%y most prominent on

sustained upward a&e, as shown in the imae 'e%ow, or on repeated eye%id c%osure. A su't%e %id

f%utter is occasiona%%y encountered.

Increasing left ptosis developing upon sustained upward

gaze in a patient with myasthenia gravis (A through F). Note the limited elevation of

the left eye denoting superior rectus palsy (A). A initially, C after around ! seconds,

F after " minute.

@n cases of uni%atera% ptosis, the contra%atera% %id may assume a ptotic position upon occ%udin the

eye with the ptosis or %iftin the ptotic %id with a finer "Herrin phenomenon$.

)he %id twitch sin descri'ed 'y Coan can 'e e%icited 'y ha!in the patient chane a&e from

the downward position to the primary position.3?4 )he %id wi%% 'e seen to o!ershoot in a twitch

'efore ainin its initia% ptotic position; this is shown in the imae 'e%ow. A study, howe!er,

*uestioned the !a%idity of such a sin, as its sensiti!ity and specificity were shown to 'e

re%ati!e%y %ow.314

Cogan sign. #he patient changes gaze from the

downward position (A) to the primary position ($). $oth lids are seen to overshoot in

a twitch ($) %efore gaining their initial ptotic position (&). In this case, the Cogan

sign is seen more o%viously on the right, whereas the left lid is more ptotic.



Extraocular muscle involvement

E0traocu%ar musc%e in!o%!ement does not fo%%ow a certain pattern. Howe!er, the superior rectus

andor the media% rectus are common%y in!o%!ed. @so%ated inferior rectus pa%sy is rare, 'ut when

it is present, it raises the suspicion of myasthenia ra!is "M#$, since it is e0treme%y rare to 'e

encountered otherwise.

)he spectrum of e0traocu%ar musc%e conditions stretches from iso%ated musc%e pa%sies to tota%

e0terna% ophtha%mop%eia. Any ac*uired ocu%ar moti%ity distur'ance, with or without ptosis 'ut

with norma%%y reactin pupi%s, shou%d raise the c%inica% suspicion of M#.

Orbicularis involvement

-r'icu%aris in!o%!ement consistent%y is present when ocu%ar symptoms are reported. Bea(ness in

forcefu% c%osure of the eyes aainst resistance is present.

Pupils and ciliary muscles

)raditiona%%y, pupi%s and ci%iary musc%es were 'e%ie!ed not to 'e in!o%!ed, a%thouh studies now

suest the contrary, nota'%y in a case ana%ysis 'y Cooper and cowor(ers.34

Treatment of Ophthalmic Manifestations

A wide armamentarium of medica% therapy e0ists for patients with myasthenia ra!is "M#$. No

enera% consensus e0ists a'out which to start first or which to com'ine. Medica% treatment is

administered 'est 'y a neuro%oist. )he ro%e of the ophtha%mo%oist is to fo%%ow up on the

ophtha%mic symptoms, nota'%y dip%opia and ptosis. )he neuro%oist orchestrates the

pharmaco%oic treatment.

<tosis, when it 'ecomes 'othersome, is treated 'est 'y %id crutches, since surery is

contraindicated 'ecause of the f%uctuation of the disease, producin %aophtha%mus with a%% of its

comp%ications. Dip%opia is e%iminated 'y resne% prisms un%ess the de!iation is %are and

!aria'%e, in which case an opa*ue %ens in front of the in!o%!ed eye is preferred.

Strabismus surgery

Successfu% musc%e surery for se%ected patients with a sta'%e course of M# and persistent

dip%opia has 'een reported.3/, 64

lepharoptosis surgery

<tosis surery for patients with a sta'%e ptosis that has fai%ed to respond to medica% therapy for

M# has ained popu%arity. )he surica% techni*ue can inc%ude e0terna% %e!ator ad!ancement,

fronta%is suspension s%in, or tarsomyectomy.39, 4

!onsultations and follow"up

Consu%t neuro%oists after dianosin patients with ocu%ar M#. )reatment is initiated 'est 'y

them rather than 'y the ophtha%mo%oist. o%%ow+up care of the patient with M# is conducted



main%y 'y the neuro%oist, who wi%% orchestrate the treatment. )he ophtha%mo%oist is consu%ted

accordin%y.

ophthalmologic manifestations of myasthenia gravis

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