SUPERIOR OBLIQUE = MUSCLE PALSY (PARESIS)

SUPERIOR OBLIQUE MUSCLE = PALSY=20 (PARESIS)

Dr.Mrs.Magdalene=20 Israel

Associate=20 Consultant

Head of the=20 Dept. Of Paediatric Ophthalmology

and Strabismus and Contact=20 Lenses

Sri=20 Sankaradeva Nethralaya

Beltola

Guwahati.

INTRODUCTION

Trochlear (IV Cranial = nerve)=20 palsy is the most common isolated cyclovertical muscle palsy encountered = by the=20 ophthalmologist.

ETIOLOGY

Usually it is = congenital (39.5%)=20 in nature resulting from a defect in the nucleus or the motor portion of = cranial=20 nerve IV, or acquired most commonly as a result of closed head trauma = (34%),=20 idiopathic (23.2%) or rarely central nervous system (2.9%) - vascular = diseases=20 with brain stem lacunar infarcts, multiple sclerosis, herpes zoster=20 ophthalmicus, brain tumors, diabetes and iatrogenic after superior = oblique=20 tenotomy.

CLINICAL=20 FEATURES

In unilateral cases = the patient=20 may present with hypertropia. Either the normal or the affected eye can = be=20 preferred for fixation. Abnormal head positions are common, and usually = a head=20 tilt towards the shoulder opposite the side of the paresis. -70%. = Paradoxical=20 head tilt towards paralyzed side can also occur. Intermittent and = unstable=20 fusion was present when head is tilted toward normal side, but = alternating=20 suppression and diplopia occurred when holding the head toward the = paralyzed=20 side- these patients preferred a head position that disrupted fusion = caused a=20 wide separation of the double images and thus eliminated the discomfort = that may=20 have been associated with the constant effort to maintain BSV.

Amblyopia is uncommon = in acquired=20 paresis but may be present in congenital ones. Extorsion and a complaint = of=20 apparent tilting of objects are common in acquired cases.

DIAGNOSIS:

OBJECTIVE=20 TESTS

BIELSCHOWSKY HEAD = TILT=20 TEST

Tilting the head = stimulates the=20 utricular reflex and invokes torsional eye movements to correct and = maintain the=20 appropriate retinal orientation. A tilt right for example, invokes = intorsion of=20 the right eye and Extorsion of the left eye. The intortors are the = superior=20 oblique and the superior rectus muscles and extorters are the inferior = oblique=20 and the inferior rectus muscles. The figure below demonstrates the = concept for a=20 right superior oblique paresis. As the head tilts to the right, the = right=20 superior oblique and right superior rectus contract to intort the right = eye.=20 Because the superior oblique is paretic the superior rectus has = unopposed=20 vertical force and elevates the eye, creating an increasing right = hyperdeviation=20 on head tilt to the right. When a patient presents with a vertical = deviation=20 first perform the head tilt test. If the head tilt is positive (>5PD=20 difference in right Vs left head tilt) then determine which muscle is = paretic by=20 the three-step test described next.

PARKS THREE STEP=20 TEST

Marshall Parks in = 1958 published=20 the =93Three Step Test=94 for the diagnosis of cyclovertical muscle = palsies. The=20 three steps are to determine

(1) Which paretic muscle might = be causing=20 the hyperdeviation in primary position? A right hyperdeviation for = example might=20 be caused by a weak depressor muscle of the right eye (i.e. right = inferior=20 rectus or right superior oblique) or a weak elevator muscle of the left = eye=20 (i.e. left superior rectus or left inferior oblique).

(2) Where the = hypertropia is=20 greatest, in right gaze or left gaze, if the hypertropia increases on = gaze away=20 from the hypertropic eye the paretic muscle is the ipsilateral oblique = or the=20 contralateral vertical rectus. A hypertropia that increases to the side = of=20 hypertropia is caused by a paretic vertical muscle on the side of the=20 hypertropia or the contralateral vertical rectus muscle that is the = paretic=20 muscle is a vertical rectus muscle of the abducting eye or an oblique = muscle of=20 the adducting eye. For example a right hyperdeviation that increases in = left=20 gaze could only be caused by a paretic left superior rectus muscle or a = paretic=20 right superior oblique muscle.

=20

&nbs= p; =20 Right gaze &nbs= p; = ; = =20 Left gaze

(3) On head tilt, which side = the=20 hypertropia is greatest: tilt right or tilt left.

The thirds step is = based on the=20 Bielschowsky head tilt test as previously described.

Wright=92s = rule-if=20 the hyperdeviation increases on head tilt to the same side of the = hyperdeviation=20 then an oblique muscle is paretic. If the hyperdeviation increases to = the=20 opposite side of the hyperdeviation, then a vertical rectus muscle is = paretic.=20 For example, if the right hyper increases on head tilt to the right = (same side=20 as the hyper) then the oblique muscle is paretic, namely the right = superior=20 oblique (SO) or left inferior oblique (IO) muscle. If the right hyper = increases=20 on left head tilt (opposite side of the hyper) then it is the vertical = rectus=20 muscle that is weak: namely the left superior rectus (SR) or right = inferior=20 rectus (IR) muscle.

OPHTHALMOSCOPY

Objective retinal = torsion is used=20 to estimate the relationship of the fovea to the optic disc. In normal = patients=20 the fovea is located between the midpoint and the lower border of the = optic=20 nerve. Patients with torsion will have a shift in the position of the = fovea=20 relative to the optic disc. With extorsion which occurs in SO paresis = the fovea=20 is shifted below the inferior border of the optic disc (Direct = Ophthalmoscope).=20 In actuality it is the disc that rotates around the fovea. A difference = of 0.25=20 or more of a disc diameter in the vertical position between the two eyes = is=20 considered abnormal.

SUBJECTIVE = TESTS

DOUBLE MADDOX ROD=20 TEST

Red and white Maddox = rods are=20 placed in right and left eyes respectively

The direction of the = rods are=20 aligned with the 90deg marks of the trial frame

The two lines are = asked to be=20 made parallel by rotating either rod. The number of degrees indicates = the=20 Excyclotropia =96if the line is slanted toward the nose.

The line will tilt in = the=20 direction in which the offending muscle would rotate the eye if it were = acting.=20 For example SO intorts the image to appear lower and slanted toward the = nose-=20 Excyclotropia.

DIPLOPIA=20 TEST

Subjective = localization of a=20 single object point imaged on the fovea of the fixating eye and extra = foveal=20 retinal area in the other eye. Patient wears a red green glass, red in = front of=20 right and is seated at 50-75cm. Streak ophthalmoscope light is used. The = patient=20 is asked whether the red and green images are fused, separated or tilted = in the=20 9 diagnostic positions and the image is drawn as the patient sees. There = is an=20 uncrossed diplopia in a case of superior oblique palsy and there is = maximum=20 separation in the lower inferior quadrant (for e.g. in a right superior = oblique=20 there is maximum separation the left lower inferior quadrant).

SYNOPTOPHORE WITH = TORSION=20 SLIDES

The synoptophore is = good=20 instrument to measure cyclodeviations, the slides can be tilted to make = the=20 patient appreciate straightening of the torsion in the slides. The = slides used=20 should have vertical features or one can use the after image slides.

FIELD CHARTING = (noting the=20 vertical displacement of the blind spot)-rarely done.

The possibility of = bilaterality=20 should always be considered. To differentiate unilateral from bilateral = the=20 following criteria are used.

(1) = Positive=20 Bielschowsky=92s test with the head tilted to either side

(2) A = right=20 hypertropia in left gaze and left hypertropia in right gaze

(3) = Absence of the=20 2 does not exclude bilateral involvement

(4) = Excyclotropia=20 of 10 deg to 15 deg - bilateral SO paresis suspected

(5) = Bilateral=20 objective excyclotorsion of the globes on fundus examination

(6) A = significant=20 V pattern esotropia (arrow subtype) with chin depression-48% of = bilateral and 5=20 % of unilateral. In bilateral paralysis vertical deviation in primary = position=20 is smaller.

UNILATERAL VERSUS BILATERAL SUPERIOR = OBLIQUE=20 PARESIS

CLINICAL = SIGNS

UNILATERAL

BILATERAL

Superior = oblique=20 underaction

Ipsilateral=20 underaction

Bilateral=20 underaction

Inferior = oblique=20 overaction

Ipsilateral=20 overaction

Bilateral=20 overaction

V-pattern

Less than = 10PD

Greater than = 10PD=20 (convergence in down gaze)

Hypertropia =

Greater than = 5PD

Less than 5 = PD

Head tilt = test

Increasing = hyper on=20 ipsilateral head tilt

Positive head = tilt to both=20 sides (RHTon right tilt and LHT on left tilt)

Extorsion

Less than = 10=B0

Greater than=20 10=B0

FALLEN = EYE

Significant = underaction of the=20 superior oblique muscle and fixation with the paretic eye will produce = the=20 classic finding called the fallen eye. When a patient with a superior = oblique=20 paresis fixes with the paretic eye and tries to look into the field of = action of=20 the paretic superior oblique muscle the weak superior oblique muscle = requires a=20 large amount of innervation to make the eye move down and nasally. = Because of=20 Hering=92s law the yoke muscle (contralateral inferior rectus muscle) = receives an=20 equally large amount of innervation. Because the contralateral inferior = rectus=20 muscle has normal function, this increased innervation produces a large=20 secondary hypotropia or the fallen eye.

PRIMARY INFERIOR = OBLIQUE (IO)=20 OVERACTION VERSUS SUPERIOR OBLIQUE (SO) PALSY:

Primary inferior = oblique=20 overaction can be differentiated from superior oblique palsy by the head = tilt=20 test and type of V- pattern.

Clinical sign

Primary overaction

Superior oblique = paresis

Inferior = oblique=20 overaction

Yes

V- = pattern

Yes, = Y-pattern

Yes, arrow=20 pattern

Head tilt = test

Negative =

Positive

Subjective = torsion

Yes (except in=20 congenital

Superior = oblique=20 paresis)

Objective = Extorsion=20 (Fundus)

Yes

Yes =

Underaction of=20 ipsilateral

Superior = oblique=20 muscle

No (minimal if = any)

Yes=20

TRAUMATIC SUPERIOR = OBLIQUE=20 PARESIS

It is usually = associated with=20 severe closed head trauma, loss of consciousness and cerebral = concussion;=20 however even very mild head trauma without loss of consciousness can = cause a=20 superior oblique paresis. It occurs when the tentorium traumatizes the = Trochlear=20 nerves as they exit the posterior mid brain posteriorly. Since the two = Trochlear=20 nerves exit the midbrain together, only a few millimeters apart the = nerve trauma=20 is always bilateral, though asymmetrical. There is a positive head tilt = test.=20 Extorsion increasing in downgaze can be demonstrated by Maddox rod and = indirect=20 ophthalmoscopy. Patients complain of horizontal vertical torsional = diplopia that=20 is worse in down gaze. In most cases there is not much inferior oblique=20 overaction (+1 or less).

CONGENITAL = SUPERIOR OBLIQUE=20 PARESIS

The cause is unknown. = The paresis=20 may be associated with a lax superior oblique tendon or rarely an absent = tendon.=20 Most cases present as unilateral or a masked bilateral paresis

Clinical features are = large=20 hypertropia in primary position, significant inferior oblique = overaction, with=20 little superior oblique underaction. The most common presenting sign is = a head=20 tilt to the opposite side of the palsy. Normally vertical fusional = amplitudes=20 are weak and even small acquired hyperdeviation of 3 to 5 PD cannot be = fused and=20 cause diplopia but in congenital paresis the patients develop large = vertical=20 fusional amplitudes and can fuse large hypertropias upto 35PD. The = presence of=20 large vertical fusional amplitudes is an important clinical sign that = the=20 hyperdeviation is long standing. These patients also have good = stereopsis, they=20 do not demonstrate extorsion by Maddox rod testing as they adapt to the = retinal=20 extorsion.

Facial asymmetry is = seen in 75%=20 of patients with one side of the face being hypoplastic (side of the = head tilt)=20 and smaller. One theory for the facial asymmetry is that gravitational = pull on=20 the dependent side of the face causes changes in size of facial = structures.=20 Another theory is that facial asymmetry represents a mild form of = congenital=20 plageocephaly associated with the superior oblique palsy.

PECULARITIES OF THE = TROCHLEAR=20 NERVE

The IV nerve=20 is the only cranial nerve that exits at the dorsal aspect of the brain = stem.

It has the=20 longest intracranial course.

It is a=20 completely crossed nerve.

The nerve can=20 be affected any way along its course. The figure below describes the = same.

The features=20 of nuclear, fascicular and peripheral fourth nerve palsy are clinically=20 indistinguishable. At the level of the cavernous sinus (III&V = cranial=20 nerves) and superior orbital fissure (III, VI cranial nerves) are also = affected=20 along with the IV nerve.

3D"Text

TREATMENT OF = SUPERIOR OBLIQUE=20 PARESIS

The management has = been=20 systematized by Knapp=92s classification, modified by Von Noorden = (1986)

Stage -I = =96Maximum=20 deviation in the field of direct antagonist (IO) =96weaken IO

=20

Stage-II = Maximum deviation=20 in the field of the agonist (paretic SO) =96Tuck SO and recess yoke IR=20 adjustable)

Stage-III = Maximum=20 deviation in the field of both paretic and direct antagonist (weaken IO, = weaken=20 yoke IR, tuck SO if >25PD hypertropia)

Stage=20 =96IV Maximum deviation is in the field of action of the paretic = agonist,=20 direct antagonist and the yoke (contralateral inferior rectus) same as = class III=20 and recess ipsilateral SR recession/contralateral inferior rectus = recession

Stage=20 =96V Maximal deviation is in the field of action of the paretic = agonist and=20 the ipsilateral depressor (double depressor weakness) - Tuck SO, weaken = yoke=20 inferior rectus

Stage-VI- = Bilateral SO=20 palsy (bilateral surgery (as above)

Stage=20 VII- SO paresis from trauma in trochlear region with restricted = elevation in=20 adduction- explore trochlea.

Traumatic=20 superior oblique paresis should be observed for 6 months following = recovery of=20 muscle function. Patients who have partial recovery with extorsional = diplopia=20 worse in downgaze without significant oblique muscle dysfunction, in = these cases=20 extorsion can be improved by the Harada Ito procedure, which consists of = selectively tightening the anterior one fourth to one third of the = superior=20 oblique tendon fibers.

Patients with=20 bilateral superior oblique palsy and poor recovery of muscle function = show a=20 large esotropia in down gaze, extorsion greater in down gaze consider = either=20 bilateral Harada Ito procedures and bilateral medial rectus muscle = recessions=20 with infraplacement one half tendon width or bilateral superior oblique = tendon=20 tucks and bilateral medial rectus muscle recessions with infraplacement = one half=20 tendon width.

A = superior=20 oblique tuck however usually results in minimal or no improvement of = superior=20 oblique function and the tight tendon creates a restrictive leash of = elevation=20 in adduction (iatrogenic Brown=92s syndrome). The tuck has been = suggested for=20 patients with congenital superior oblique paresis secondary to a lax = superior=20 oblique tendon.