Difference between revisions of "Monocular Elevation Deficit"

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{{DISPLAYTITLE:Monocular Elevation Deficit}}
 
 
{{Article
 
{{Article
 
|Authors=Gunjan.Saluja
 
|Authors=Gunjan.Saluja
 
|Category=Pediatric Ophthalmology/Strabismus
 
|Category=Pediatric Ophthalmology/Strabismus
|Reviewer=Gunjan.Saluja
+
|Assigned editor=Kara.Cavuoto
|Date reviewed=December 13, 2018
+
|Reviewer=Kara.Cavuoto
 +
|Date reviewed=March 7, 2021
 +
|Article status=Up to Date
 +
|Meta description=Monocular elevation deficit (MED), or double elevator palsy, is the limitation of elevation of the affected eye that is similar in both adduction and abduction.
 
}}
 
}}
 
 
= Disease Entity  =
 
= Disease Entity  =
Monocular elevation deficit ( Double elevator palsy)
+
Monocular elevation deficit or double elevator palsy
  
 
== Disease  ==
 
== Disease  ==
 
+
Monocular Elevation Deficiency (MED) is the limitation of elevation of the affected eye that is similar in both adduction and abduction. MED is one of the causes of hypotropia and can be associated with ptosis/pseudoptosis.  
Monocular Elevation Deficiency (MED) is the limitation of elevation of the affected eye from any position of gaze with normal ductions in all other gazes. MED is a frequent cause of hypotropia and can be associated with ptosis/pseudoptosis. Superior rectus palsy, inferior rectus restriction and supranuclear lesions have been found to be contributory to MED.
 
 
  
 
== Etiology  ==
 
== Etiology  ==
MED can be congenital or acquired . Congenital cases of MED occur sporadically.<ref name="bagheri1">Bagheri A, Sahebghalam R and Abrishami M. Double Elevator Palsy, Subtypes and Outcomes of Surgery. Journal of Ophthalmic &amp; Vision Research 3.2 (2008): 108.</ref>     
+
MED can be congenital or acquired. Congenital cases of MED occur sporadically.<ref name="bagheri1">Bagheri A, Sahebghalam R and Abrishami M. Double Elevator Palsy, Subtypes and Outcomes of Surgery. Journal of Ophthalmic &amp; Vision Research 3.2 (2008): 108.</ref>    The causes include supranuclear palsy, primary superior rectus paresis and primary inferior rectus restriction.<ref name="jampel2">Jampel RS, Fell P: Monocular elevation paresis caused by a central nervous system lesion. Arch Ophthalmol 1968: 80:4.</ref> Acquired cases are usually caused by  trauma, cerebrovascular diseases like hypertension, thromboembolism, sarcoidosis and syphilis or tumors such as pineocytomas, acoustic neuromas and metastases.<ref name="rosenbaum3">Rosenbaum AL. Clinical strabismus management. 1st ed. Philadelphia: WB Saunders; 1999.</ref>
 
 
Congenital causes of MED include, supranuclear palsy, primary superior rectus (SR) paresis and primary inferior rectus(IR) restriction as in cases of congenital fibrosis of inferior rectus.<ref name="jampel2">Jampel RS, Fell P: Monocular elevation paresis caused by a central nervous system lesion. Arch Ophthalmol 1968: 80:4.</ref>
 
 
 
Acquired MED is usually caused by  trauma, cerebrovascular diseases like hypertension, thromboembolism, sarcoidosis, syphilis, and midbrain tumors like pineocytomas, acoustic neuromas and metastatic tumors affecting supranuclear pathways.<ref name="rosenbaum3">Rosenbaum AL. Clinical strabismus management. 1st ed. Philadelphia: WB Saunders; 1999.</ref>
 
 
 
  
 
== General Pathology  ==
 
== General Pathology  ==
 +
There are generally thought to be three forms of this motility disorder: inferior rectus restriction; deficient innervation of the elevator muscles; or a combination of restriction and elevator deficit. <ref name="ziffer4">Ziffer AJ, Rosenbaum AL, Demer JL, Yee RD. Congenital double elevator palsy: vertical saccadic velocity utilizing the scleral search coil technique. J Pediatr Ophthalmol Strabismus. 1992; 29:142–9.</ref>
  
MED has been classified into three types by Ziffer et al. <ref name="ziffer4">Ziffer AJ, Rosenbaum AL, Demer JL, Yee RD. Congenital double elevator palsy: vertical saccadic velocity utilizing the scleral search coil technique. J Pediatr Ophthalmol Strabismus. 1992; 29:142–9.</ref>
+
In Type 1, the etiology is inferior rectus restriction, and thus includes patients with primary inferior rectus restriction or fibrosis. Forced duction test (FDT) demonstrates a tight inferior rectus. The upward saccades are usually normal until the tight inferior rectus limits upgaze. Bell's phenomenon is usually poor.  
 
 
Type 1 includes patients with primary IR restriction or fibrosis.  
 
 
 
Forced duction test (FDT) demonstrates a tight IR. The upward saccades are usually normal until stopped by tight IR , preventing further upgaze. Bells phenomenon is usually poor.  
 
  
In Type 2 MED, cases of primary SR palsy are included. FDT is free and upward saccades are slow both below and above midline. Bell’s phenomenon is usually absent.  
+
In Type 2, the etiology is deficient innervation of the elevator muscles, and thus includes primary superior rectus palsy. FDT is free and upward saccades are slow both below and above midline. Bell’s phenomenon is usually absent.  
  
Type 3 MED is supranuclear type and is usually congenital. It is characterized by intact or mildly reduced vertical saccadic velocity below midline but abnormal or absent velocity above midline and FDT is free.
+
In Type 3, the etiology is the supranuclear type and is usually congenital. It is characterized by intact or mildly reduced vertical saccadic velocity below midline but abnormal or absent velocity above midline. FDT is unlimited.
  
 
== Pathophysiology  ==
 
== Pathophysiology  ==
 
+
Efferent tracts for upgaze leave the rostral interstitial nucleus of the medial longitudinal fasciculus, cross the midline in the posterior commissure, course through the pretectum and enter the superior rectus subnucleus of the oculomotor nucleus, leave the subnucleus, and cross the midline again. As a result of double decussation, the superior rectus receives innervation from ipsilateral rostral interstitial nucleus of the medial longitudinal fasciculus  as well as contralateral pretectum and superior rectus subnucleus. In cases of MED, it is presumed that supranuclear input from the rostral interstitial nucleus of the medial longitudinal fasciculus into third cranial nerve nucleus is interrupted. Supranuclear deficiency affects upgaze, therefore causing deficient elevation.
There are different school of thoughts regarding the pathogenesis of MED. It has been established that superior rectus is the main muscle responsible for elevation of the eye, be it in abduction, adduction or primary position. Thus, the defective elevation can  be explained by presence of a superior rectus palsy alone, inferior rectus  restriction can also be considered as a cause of MED in  presence of a normal superior rectus. 
 
 
 
Efferent tracts for upgaze leave the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), cross the midline in the posterior commissure, course through the pretectum and enter the superior rectus (SR) subnucleus of the oculomotor nucleus, leaving the subnucleus, upgaze fibres to the SR immediately cross the midline again. As a result of double decussation of upgaze fibers, the SR receives innervation from ipsilateral riMLF as well as contralateral pretectum and SR subnucleus. In cases of MED, it is presumed that supranuclear input from riMLF into third cranial nerve nucleus is interrupted. Supranuclear deficiency affects upgaze, therefore causes  monocular elevation deficiency.
 
 
 
 
 
== Clinical features  ==
 
[[File:20181213 213725.jpg|thumb|A patient of Monocular Elevation Deficit showing ptosis and hypotropia]]
 
* Age: Average age of presentation is 14 years as reported in previous studies.<ref name="bandyopadhyay5">Bandyopadhyay R, Shetty S, Vijayalakshmi P. Surgical outcome in monocular elevation deficit: A retrospective interventional study. Ind J Ophthalmol 2008; 56:127-33.</ref>
 
* Gender: No gender predisposition
 
  
 
=== Chief Complaints ===
 
=== Chief Complaints ===
 
+
Patients can present with the following complaints:
Patients usually present with the following complaints:
 
 
* Vertical misalignment of the eyes
 
* Vertical misalignment of the eyes
 
* Diplopia
 
* Diplopia
Line 55: Line 36:
 
* Inability to elevate the affected eye
 
* Inability to elevate the affected eye
 
* Drooping of eyelid
 
* Drooping of eyelid
* Decrease vision
+
* Decreased vision
  
 
== Signs  ==
 
== Signs  ==
[[File:Monocular elevation deficit .jpg|thumb|Extraocular movements in nine gazes in a patient of monocualr elevation deficit]]
+
[[File:Monocular elevation deficit .jpg|thumb|Extraocular movements in nine gazes in a patient of monocular elevation deficit]]
[[File:20181213 213839.jpg|thumb|Figure 2: Showing pseudoptosis in a patient with Monocular Elvation Deficit, note that ptosis improves on fixing with the affected eye]]
+
* Ptosis/Pseudoptosis: Ptosis can be associated with hypotropia because of fascial attachments between the levator palpebrae superioris and superior rectus muscle.  Pseudoptosis can be present in primary gaze when fixating with the contralateral eye, however improves when the hypotropic eye takes up fixation. Both pseudoptosis and true ptosis can be present in the patient.  
* '''Ptosis/Pseudoptosis''': Ptosis can be associated with hypotropia because of fascial attachments between levator palpebrae superioris and superior rectus muscle.  Pseudoptosis can be present that disappears when hypotropic eye takes up fixation in primary position. Pseudoptosis disappears after the successful vertical alignment of the globe .  Pseudoptosis and true ptosis both the components can be present in the patient. In these cases when the patient is made to fix with the affected eye, ptosis partly recovers. True ptosis when present is usually complex type and is associated with Marcus Gunn Jaw Winking phenomenon (MGJWP).
+
* Strabismus: There is hypotropia of the affected eye when the normal eye is fixing and hypertropia of the contralateral eye when fixating with the affected eye.  
* '''Deviation''': There is hypotropia of the affected eye when the normal eye is fixing , but as the affected eye takes up fixation there is  hypertropia of the normal eye. MED cases may also have co-existent horizontal deviations.
+
* Bell’s phenomenon: The phenomenon is typically absent in cases of inferior rectus restriction and superior rectus palsy, but is usually present in cases of MED resulting from supranuclear defects.
* '''Bell’s phenomenon''' is usually absent in cases of IR restriction and SR palsy as they limit the upward rotation of globe, but Bell's  is usually present in cases of MED resulting from supranuclear defects.
+
* Amblyopia: Asymmetric vision may be present if there is a constant deviation of affected eye, ptosis, or anisometropia.
* Amblyopia may be present if there is a constant deviation of affected eye or associated ptosis, or anisometropia.
+
* Abnormal Head Posture : Most commonly the patient has a chin elevation if binocular fusion is present. Abnormal head posture may not be present if the affected eye is amblyopic.
* '''Abnormal Head Posture''' : Most commonly patient has a chin elevation if binocular fusion is present. Abnormal head posture may not be present if the affected eye is amblyopic.
+
* Saccades: Upward saccades are slow in cases of superior rectus palsy, absent above the midline in supranuclear palsy, and intact but stop abruptly in cases associated with inferior rectus restriction.
* '''Upward Saccades''': Upward saccades are slow/floating in cases of SR palsy, absent above the midline in supranuclear palsy , and intact (coming to an abrupt halt) in cases associated with IR restriction.
 
 
 
 
 
== Diagnostic procedures  ==
 
 
 
===Forced duction test ===
 
Forced duction test is a clinical test which should be done pre-operatively to reveal any restriction. The test is typically performed under topical anaesthesia, conjunctiva is held at limbus with Pierce Hoskin forceps or globe holding forceps, and patient is asked to look in opposite direction of testing muscle to relax the concerned muscle. A positive Forced Duction Test (FDT) is seen in patients of IR restriction.  
 
  
 +
== Diagnostic Procedures  ==
 +
===Forced Duction Test ===
 +
Forced duction test is a clinical test to evaluate for restriction. The test is performed under topical or general anesthesia. The conjunctiva is held at limbus with forceps and the globe is rotated by the examiner.
 
===Active Force Generation Test===
 
===Active Force Generation Test===
Active force generation test is done under topical anaesthesia by asking the patient to look in the  direction of muscle being tested, presence of a tug is suggestive of residual SR action.  
+
Active force generation test is done under topical anesthesia by asking the patient to look in the  direction of the muscle being tested.  
 
+
=== Diplopia ===
=== Diplopia Charting ===
+
Worth Four Dot testing is done with red and green glasses (red over the right eye) to dissociate the images from each eye. The test is performed at distance and near.
Red and green glasses over right and left eyes respectively,  dissociate the two images and would be seen double. Test can be done both for distance and near, with the help of illuminated slit target. The slit is used vertically for charting horizontal deviations and horizontally for charting vertical deviations. The seperation between two images is recorded and is useful in diagnosis and follow-up.
 
  
=== Hess Screen And Lees Screen ===
 
Hess Screen and Lees Screen is used to document relative incomitance and underactions and is based on haploscopic principle. Two test objects are shown to the patient which is seen  as one localisation.
 
 
Hess Screen consist of a three and a half feet black cloth marked with a series of red lines forming a square of 5 degree each. From the central zero point three squares 15 degree marks the inner square and outer square has excursion of 30 degree. The outer square is used for mild incomitances not detected on inner square charting. Patient  wears a red green glass, with red glass in front of right eye and green glass in front of left eye, patient is given a green pointer which he aligns on the red dots and the observer records the points.
 
[[File:MED Hess chart.jpg|thumb|Hess chart showing elevation deficit]]
 
Lees Screen is also similar but does not require red green glass instead uses a mirror septa to cause dissociation of two eye.
 
 
== Differential diagnosis  ==
 
== Differential diagnosis  ==
 
+
The main differential diagnosis of MED includes:
The main differential diagnosis of monocular elevation deficit includes-
+
*Brown syndrome - characterized by limitation of elevation in adduction with Y pattern exotropia
 
+
*Duane syndrome - diagnosed by the presence of globe retraction in downgaze along with limitation of elevation in upgaze
* Brown’s Syndrome is characterised by limitation of elevation in adduction, with divergence in upgaze caused by slippage of globe resulting in characterstic Y pattern
+
*Congenital fibrosis of the extra ocular muscles -may initially affect the inferior rectus muscles and thus be misdiagnosed as MED. Bilateral presentation and involvement of other extraocular muscles help distinguish it.
* Vertical Duane Syndrome can be diagnosed by the presence of globe retraction in downgaze along with limitation of elevation in upgaze.
+
*Partial third nerve palsy - particularly if involving the superior division of oculomotor nerve   
* Congenital fibrosis of extra ocular muscles initially affecting inferior recti can be misdiagnosed as MED. Bilateral presentation and involvement of other extraocular muscles are features that help distinguish it.
+
*Progressive external ophthalmoplegia  - differentiated as it involves multiple extraocular muscles
* Partial third nerve palsy involving the superior division of oculomotor nerve  may simulate the findings of MED.
+
*Orbital inflammatory disease  
* Progressive external ophthalmoplegia  involves multiple extra ocular muscles.
+
*Orbital cellulitis
* Orbital inflammatory disease and orbital cellulitis present with a tender inflamed globe.
 
  
 
= Management  =
 
= Management  =
 
Management of MED includes both non-surgical and surgical components.   
 
Management of MED includes both non-surgical and surgical components.   
  
=== Non-surgical management ===
+
=== Non-Surgical Management ===
The correction of underlying refractive error is to be done and amblyopia therapy is given if needed, followed by surgery whenever indicated.  
+
It is important to correct any underlying refractive error and treat amblyopia.  
  
 
=== Surgery  ===
 
=== Surgery  ===
 
[[File:Knapps procedure.jpeg|thumb|Diagrammatic representation of Knapp’s procedure]]
 
[[File:Knapps procedure.jpeg|thumb|Diagrammatic representation of Knapp’s procedure]]
 
[[File:Modified Knapps.jpeg|thumb|Diagrammatic representation of Modified Knapp’s procedure]]
 
[[File:Modified Knapps.jpeg|thumb|Diagrammatic representation of Modified Knapp’s procedure]]
Indications for surgery include
 
* Significant vertical deviation in primary gaze
 
* Significant abnormal head posture
 
* Deviation-induced amblyopia
 
* Diplopia in primary gaze, and restricted binocular fields.
 
  
 +
The goal of surgery is to improve the position of the affected eye in primary gaze and to increase binocular field of vision.
  
The goal of surgery is to improve the position of the affected eye in primary gaze and to increase binocular field of vision.
+
Indications for surgery include:
 +
*Significant vertical deviation in primary gaze
 +
*Significant abnormal head posture
 +
*Deviation-induced amblyopia
 +
*Diplopia in primary gaze
 +
*Restricted binocular fields
  
The surgery of choice in the management of monocular elevation deficit depends on results of forced duction test. In patients with positive forced duction test, inferior rectus recession is the first choice of management.
 
  
In patients with negative forced duction test but a positive active force generation test, superior rectus resection can be done.
+
In general, the surgery of choice in the management of MED depends on results of the forced duction test. In patients with a positive forced duction test, inferior rectus recession is the first choice of management. If there is no restriction, transposition of the medial and lateral rectus muscles to the superior rectus muscle can be performed (Knapp procedure). Other options include resection of the ipsilateral superior rectus muscle or recession of the contralateral superior rectus muscle.
  
In patients with negative forced duction test and a negative active force generation test Knapp's procedure is preferred.
+
In greater detail:
 
* Knapp's procedure <ref name="knapp6">Knapp P. The surgical treatment of double elevator paralysis. Trans Am Ophthalmol Soc. 1969; 67:304–23</ref>
 
* Knapp's procedure <ref name="knapp6">Knapp P. The surgical treatment of double elevator paralysis. Trans Am Ophthalmol Soc. 1969; 67:304–23</ref>
Knapp’s procedure is commonly practiced and is now a well-established treatment for monocular elevation deficiency. In the Knapp’s procedure, the tendons of the medial and lateral rectus muscles are transposed to the insertion of the superior rectus muscle.  Knapp’s in his work studied 15 patients over a period of eight years. The procedure showed marked variability correcting 21-55 PD (average 38 PD) hypotropia.
+
The medial and lateral rectus muscles are transposed to the insertion of the superior rectus muscle.  In Knapp’s own study, the procedure showed marked variability correcting 21-55 PD (average 38 PD) hypotropia.
 
* Modifications of Knapp's procedure<ref name="kamlesh7">Kamlesh, Dadeya S. Surgical management of unilateral elevator deficiency associated with horizontal deviation using a modified Knapp’s procedure. Ophthalmic Surg Lasers Imaging. 2003; 34:230–5.</ref>
 
* Modifications of Knapp's procedure<ref name="kamlesh7">Kamlesh, Dadeya S. Surgical management of unilateral elevator deficiency associated with horizontal deviation using a modified Knapp’s procedure. Ophthalmic Surg Lasers Imaging. 2003; 34:230–5.</ref>
For management of MED cases with associated horizontal deviation partial tendon Knapp’s (Modifed Knapp’s) procedure has been described, in which the superior part of equally divided horizontal muscles is placed near the superior rectus muscle insertion, allowing the correction of horizontal deviation with the untouched inferior half.
+
For cases with an associated horizontal deviation, a partial tendon Knapp’s procedure has been described. In this procedure, the superior halves of the equally divided horizontal muscles are placed near the superior rectus muscle insertion, which allows for correction of the horizontal deviation with the inferior halves.
* Augmented Knapp's procedure, Knapp's procedure can be combined with posterior fixation sutures on the horizontal recti, known as Augmented Knapp's.
+
* Augmented Knapp's procedure
Following the surgical correction of  hypotropia, and improvement in  Bell’s phenomenon, associated ptosis and/or Marcus Gunn phenomenon be addressed.  
+
Augmented Knapp's procedure utilizes Knapp's procedure combined with posterior fixation sutures on the horizontal recti to increase its effect.
 
* Modified Nishida's for monocular elevation deficit<ref name="sowmya8">Sowmya Ravendra Murthy, Mithuna Pappuru,Modified Nishida's procedure for monocular elevation deficiency JAAPOS, 2018 August;327-329</ref>
 
* Modified Nishida's for monocular elevation deficit<ref name="sowmya8">Sowmya Ravendra Murthy, Mithuna Pappuru,Modified Nishida's procedure for monocular elevation deficiency JAAPOS, 2018 August;327-329</ref>
No split no tenotomy technique by Nishida et al has originally been described for abducen nerve palsy, the procedure has been found to be useful in the management of monocular  elevation deficit by Murthy et al and can help in correction of upto 30 pd of vertical deviation with low risk of anterior segment ischemia.  
+
A technique by Nishida et al that was originally described for abducen nerve palsies can be used to correct up to 30 PD of vertical deviation with low risk of anterior segment ischemia.  
 
* Contralateral superior rectus recession <ref name="ocak9">Ocak OB, InalA et al  Surgical Management in Type 1 Monocular Elevation Deficiency J Pediatr Ophthalmol Strabismus. 2018 Nov 19;55(6):369-374.</ref>  
 
* Contralateral superior rectus recession <ref name="ocak9">Ocak OB, InalA et al  Surgical Management in Type 1 Monocular Elevation Deficiency J Pediatr Ophthalmol Strabismus. 2018 Nov 19;55(6):369-374.</ref>  
Contralateral superior rectus recession can be an option of management in the patients with residual hypotropia after inferior rectus recession.   
+
Contralateral superior rectus recession may be an option in patients with residual hypotropia after inferior rectus recession.   
 +
 
 +
Ptosis can be addressed after the vertical deviation has been corrected to ensure the pseudoptosis element has been eliminated. 
  
 
=== Management of  Acquired MED ===
 
=== Management of  Acquired MED ===
As there are wide variety of causes of acquired MED, thorough investigations (general, ophthalmologic, neurologic, neuro-ophthalmologic and orthoptic (ocular motility work up) should be undertaken, and management varies according to the underlying cause.
+
As there are wide variety of causes of acquired MED, a thorough workup should be performed. The management varies according to the underlying cause.
  
 
== Complications ==
 
== Complications ==
Ptosis can lead to refractive error and amblyopia, also if ptosis surgery is done before the strabismus surgery it can lead to exposure keratopathy as most of the patients have poor Bell's phenomenon.
+
Surgical complications that may occur when treating MED include:
 
+
* Overcorrections and undercorrections
Surgical complications seen commonly in a case of monocular elevation deficit include:
+
* Tenon's prolapse
* Anterior segment ischemia, is a serious complication presenting with corneal edema, thinning, non pigmented keratin precipitates, iris atrophy and anterior chamber flare. Anterior segment ischemia can result if three or more adjacent recti surgery has been done in one eye, adults with atherosclerosis, previous radiation therapy, and retinal detachment surgery are more vulnerable. The complication can be avoided if two vertical recti along with one horizontal recti are not operated in the same sitting. Management includes, systemic and local corticosteroids
+
* Conjunctival cyst   
* Overcorrections and undercorrections.
+
* Corneal dellen formation  
* Tenon's prolapse and conjunctival cyst  can result due to improper apposition of the conjunctiva which allows Tenon's to prolapse, and interferes with healing process.
+
* Anterior segment ischemia
* Corneal dellen formation can occur due to disruption of tear film and local dehydration.
 
* Other intraoperative complications like surgery on wrong eye, wrong muscle, hemorrhages, scleral perforation,slipped muscle, bradycardia, infections may also occur in patients undergoing surgery.
 
 
 
== Prognosis ==
 
[[File:MED effectiveness.png|thumb|Table1: Average correction obtained with various surgical procedures]]
 
The average correction resulting from various surgical procedures vary, and has been summarised in Table 1.
 
  
 
= References  =
 
= References  =

Latest revision as of 19:31, March 11, 2021


Disease Entity

Monocular elevation deficit or double elevator palsy

Disease

Monocular Elevation Deficiency (MED) is the limitation of elevation of the affected eye that is similar in both adduction and abduction. MED is one of the causes of hypotropia and can be associated with ptosis/pseudoptosis.

Etiology

MED can be congenital or acquired. Congenital cases of MED occur sporadically.[1] The causes include supranuclear palsy, primary superior rectus paresis and primary inferior rectus restriction.[2] Acquired cases are usually caused by trauma, cerebrovascular diseases like hypertension, thromboembolism, sarcoidosis and syphilis or tumors such as pineocytomas, acoustic neuromas and metastases.[3]

General Pathology

There are generally thought to be three forms of this motility disorder: inferior rectus restriction; deficient innervation of the elevator muscles; or a combination of restriction and elevator deficit. [4]

In Type 1, the etiology is inferior rectus restriction, and thus includes patients with primary inferior rectus restriction or fibrosis. Forced duction test (FDT) demonstrates a tight inferior rectus. The upward saccades are usually normal until the tight inferior rectus limits upgaze. Bell's phenomenon is usually poor.

In Type 2, the etiology is deficient innervation of the elevator muscles, and thus includes primary superior rectus palsy. FDT is free and upward saccades are slow both below and above midline. Bell’s phenomenon is usually absent.

In Type 3, the etiology is the supranuclear type and is usually congenital. It is characterized by intact or mildly reduced vertical saccadic velocity below midline but abnormal or absent velocity above midline. FDT is unlimited.

Pathophysiology

Efferent tracts for upgaze leave the rostral interstitial nucleus of the medial longitudinal fasciculus, cross the midline in the posterior commissure, course through the pretectum and enter the superior rectus subnucleus of the oculomotor nucleus, leave the subnucleus, and cross the midline again. As a result of double decussation, the superior rectus receives innervation from ipsilateral rostral interstitial nucleus of the medial longitudinal fasciculus as well as contralateral pretectum and superior rectus subnucleus. In cases of MED, it is presumed that supranuclear input from the rostral interstitial nucleus of the medial longitudinal fasciculus into third cranial nerve nucleus is interrupted. Supranuclear deficiency affects upgaze, therefore causing deficient elevation.

Chief Complaints

Patients can present with the following complaints:

  • Vertical misalignment of the eyes
  • Diplopia
  • Abnormal head posture
  • Inability to elevate the affected eye
  • Drooping of eyelid
  • Decreased vision

Signs

Extraocular movements in nine gazes in a patient of monocular elevation deficit
  • Ptosis/Pseudoptosis: Ptosis can be associated with hypotropia because of fascial attachments between the levator palpebrae superioris and superior rectus muscle. Pseudoptosis can be present in primary gaze when fixating with the contralateral eye, however improves when the hypotropic eye takes up fixation. Both pseudoptosis and true ptosis can be present in the patient.
  • Strabismus: There is hypotropia of the affected eye when the normal eye is fixing and hypertropia of the contralateral eye when fixating with the affected eye.
  • Bell’s phenomenon: The phenomenon is typically absent in cases of inferior rectus restriction and superior rectus palsy, but is usually present in cases of MED resulting from supranuclear defects.
  • Amblyopia: Asymmetric vision may be present if there is a constant deviation of affected eye, ptosis, or anisometropia.
  • Abnormal Head Posture : Most commonly the patient has a chin elevation if binocular fusion is present. Abnormal head posture may not be present if the affected eye is amblyopic.
  • Saccades: Upward saccades are slow in cases of superior rectus palsy, absent above the midline in supranuclear palsy, and intact but stop abruptly in cases associated with inferior rectus restriction.

Diagnostic Procedures

Forced Duction Test

Forced duction test is a clinical test to evaluate for restriction. The test is performed under topical or general anesthesia. The conjunctiva is held at limbus with forceps and the globe is rotated by the examiner.

Active Force Generation Test

Active force generation test is done under topical anesthesia by asking the patient to look in the direction of the muscle being tested.

Diplopia

Worth Four Dot testing is done with red and green glasses (red over the right eye) to dissociate the images from each eye. The test is performed at distance and near.

Differential diagnosis

The main differential diagnosis of MED includes:

  • Brown syndrome - characterized by limitation of elevation in adduction with Y pattern exotropia
  • Duane syndrome - diagnosed by the presence of globe retraction in downgaze along with limitation of elevation in upgaze
  • Congenital fibrosis of the extra ocular muscles -may initially affect the inferior rectus muscles and thus be misdiagnosed as MED. Bilateral presentation and involvement of other extraocular muscles help distinguish it.
  • Partial third nerve palsy - particularly if involving the superior division of oculomotor nerve
  • Progressive external ophthalmoplegia - differentiated as it involves multiple extraocular muscles
  • Orbital inflammatory disease
  • Orbital cellulitis

Management

Management of MED includes both non-surgical and surgical components.

Non-Surgical Management

It is important to correct any underlying refractive error and treat amblyopia.

Surgery

Diagrammatic representation of Knapp’s procedure
Diagrammatic representation of Modified Knapp’s procedure

The goal of surgery is to improve the position of the affected eye in primary gaze and to increase binocular field of vision.

Indications for surgery include:

  • Significant vertical deviation in primary gaze
  • Significant abnormal head posture
  • Deviation-induced amblyopia
  • Diplopia in primary gaze
  • Restricted binocular fields


In general, the surgery of choice in the management of MED depends on results of the forced duction test. In patients with a positive forced duction test, inferior rectus recession is the first choice of management. If there is no restriction, transposition of the medial and lateral rectus muscles to the superior rectus muscle can be performed (Knapp procedure). Other options include resection of the ipsilateral superior rectus muscle or recession of the contralateral superior rectus muscle.

In greater detail:

  • Knapp's procedure [5]

The medial and lateral rectus muscles are transposed to the insertion of the superior rectus muscle. In Knapp’s own study, the procedure showed marked variability correcting 21-55 PD (average 38 PD) hypotropia.

  • Modifications of Knapp's procedure[6]

For cases with an associated horizontal deviation, a partial tendon Knapp’s procedure has been described. In this procedure, the superior halves of the equally divided horizontal muscles are placed near the superior rectus muscle insertion, which allows for correction of the horizontal deviation with the inferior halves.

  • Augmented Knapp's procedure

Augmented Knapp's procedure utilizes Knapp's procedure combined with posterior fixation sutures on the horizontal recti to increase its effect.

  • Modified Nishida's for monocular elevation deficit[7]

A technique by Nishida et al that was originally described for abducen nerve palsies can be used to correct up to 30 PD of vertical deviation with low risk of anterior segment ischemia.

  • Contralateral superior rectus recession [8]

Contralateral superior rectus recession may be an option in patients with residual hypotropia after inferior rectus recession.

Ptosis can be addressed after the vertical deviation has been corrected to ensure the pseudoptosis element has been eliminated.

Management of Acquired MED

As there are wide variety of causes of acquired MED, a thorough workup should be performed. The management varies according to the underlying cause.

Complications

Surgical complications that may occur when treating MED include:

  • Overcorrections and undercorrections
  • Tenon's prolapse
  • Conjunctival cyst
  • Corneal dellen formation
  • Anterior segment ischemia

References

  1. Bagheri A, Sahebghalam R and Abrishami M. Double Elevator Palsy, Subtypes and Outcomes of Surgery. Journal of Ophthalmic & Vision Research 3.2 (2008): 108.
  2. Jampel RS, Fell P: Monocular elevation paresis caused by a central nervous system lesion. Arch Ophthalmol 1968: 80:4.
  3. Rosenbaum AL. Clinical strabismus management. 1st ed. Philadelphia: WB Saunders; 1999.
  4. Ziffer AJ, Rosenbaum AL, Demer JL, Yee RD. Congenital double elevator palsy: vertical saccadic velocity utilizing the scleral search coil technique. J Pediatr Ophthalmol Strabismus. 1992; 29:142–9.
  5. Knapp P. The surgical treatment of double elevator paralysis. Trans Am Ophthalmol Soc. 1969; 67:304–23
  6. Kamlesh, Dadeya S. Surgical management of unilateral elevator deficiency associated with horizontal deviation using a modified Knapp’s procedure. Ophthalmic Surg Lasers Imaging. 2003; 34:230–5.
  7. Sowmya Ravendra Murthy, Mithuna Pappuru,Modified Nishida's procedure for monocular elevation deficiency JAAPOS, 2018 August;327-329
  8. Ocak OB, InalA et al  Surgical Management in Type 1 Monocular Elevation Deficiency J Pediatr Ophthalmol Strabismus. 2018 Nov 19;55(6):369-374.
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