Atormac
brintellex
Neurology India
menu-bar5 Open access journal indexed with Index Medicus
  Users online: 438  
 Home | Login 
About Editorial board Articlesmenu-bullet NSI Publicationsmenu-bullet Search Instructions Online Submission Subscribe Videos Etcetera Contact
  Navigate Here 
 Search
 
  
 Resource Links
  »  Similar in PUBMED
 »  Search Pubmed for
 »  Search in Google Scholar for
 »Related articles
  »  Article in PDF (975 KB)
  »  Citation Manager
  »  Access Statistics
  »  Reader Comments
  »  Email Alert *
  »  Add to My List *
* Registration required (free)  

 
  In this Article
 »  Abstract
 »  Materials and Me...
 » Results/observation
 » Discussion
 » Conclusions
 »  References
 »  Article Figures
 »  Article Tables

 Article Access Statistics
    Viewed155    
    Printed0    
    Emailed0    
    PDF Downloaded12    
    Comments [Add]    

Recommend this journal

 


 
Table of Contents    
ORIGINAL ARTICLE
Year : 2020  |  Volume : 68  |  Issue : 4  |  Page : 840-842

Convergence Weakness with Intact Medial Rectus Function in Proptosis due to Orbital Tumors


1 Department of Neurosurgery, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
2 Department of Opthalmology, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
3 Department of Neurology, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India

Date of Web Publication26-Aug-2020

Correspondence Address:
Dr. Madhivanan Karthigeyan
Department of Neurosurgery, PGIMER, Sector 12, Chandigarh - 160 012
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.293479

Rights and Permissions

 » Abstract 


Background: The pathway underlying ocular convergence is less clear. Convergence weakness is usually a clinical sign of dorsal midbrain pathology. An orbital tumor causing such phenomenon is unknown. We describe its occurrence in patients with proptosis due to orbital tumors.
Materials and Methods: Series of six patients with axial proptosis secondary to orbital tumors that demonstrated varying forms of convergence weakness (deficiency to complete failure).
Results: Three had weakness of convergence with drifting away of proptosed eyeball on attempted near vision, while the other three had failure. One of these had convergence weakness in nonproptosed eye. MRI excluded a central etiology in all.
Conclusions: The article highlights an interesting phenomenon of deficient convergence in the presence of intact medial rectus function in patients with proptosis. The symmetry of orbital contents possibly plays a significant role in the process of convergence.


Keywords: Convergence, convergence insufficiency, convergence weakness, orbital tumor, proptosis
Key Messages: Patients with proptosis secondary to orbital mass lesions can have convergence deficiency in spite of an intact medial rectus function.


How to cite this article:
Salunke P, Karthigeyan M, Praneeth K, Kaur S, Takkar A. Convergence Weakness with Intact Medial Rectus Function in Proptosis due to Orbital Tumors. Neurol India 2020;68:840-2

How to cite this URL:
Salunke P, Karthigeyan M, Praneeth K, Kaur S, Takkar A. Convergence Weakness with Intact Medial Rectus Function in Proptosis due to Orbital Tumors. Neurol India [serial online] 2020 [cited 2020 Sep 30];68:840-2. Available from: http://www.neurologyindia.com/text.asp?2020/68/4/840/293479




The pathways regulating ocular convergence are less understood.[1],[2] Convergence weakness is considered as a central phenomenon and usually a feature of dorsal midbrain lesions.[2],[3] On the other hand, convergence insufficiency (CI) that clinically manifests as eye strain after near work is possibly due to insufficient accommodation.[4] The etiopathological factors causing CI is multiple and less understood.[4]

Orbital tumors usually present with proptosis.[5] The lesions may involve muscles causing impaired ocular movements. However, in the presence of intact movements with proptosis, convergence weakness is unexpected. The literature addressing convergence weakness/insufficiency in proptosis due to orbital tumors is sparse. In the present report, we describe a short series of six patients with proptosis that showed clinical signs of convergence weakness/insufficiency.


 » Materials and Methods Top


The study was carried out after obtaining informed consent from the patients. Six patients presenting with unilateral proptosis were studied. The proptosis was gradual in onset, painless, progressive, and axial in nature. Other than proptosis, two patients had history of decrease in visual acuity. None complained of diplopia. There was no extraocular muscle paresis in any of the patient. Corneal sensations were normal. A heterophoria was excluded by performing cover-uncover test. Fundoscopy revealed no abnormalities.

Magnetic resonance imaging (MRI) of orbit revealed benign neoplasm in all except one who showed sphenoid dysplasia. Two patients had schwannoma and two had meningioma [Figure 1] and [Figure 2]. In one, the lesion was hemangioma. MRI of brain revealed no abnormalities. The clinical and radiological characteristics of patients are summarized in [Table 1].
Figure 1: (a and b) Magnetic resonance imaging (MRI), axial (a) and parasagittal (b) views showing left eye proptosis with intraconal contrast-enhancing lesion (schwannoma). (c) Axial T2 weighted MRI shows intact left medial rectus muscle, uninvolved by tumor

Click here to view
Figure 2: (a and b) Axial (a) and parasagittal (b) views of magnetic resonance imaging (MRI) showing sphenoid wing contrast-enhancing dural based lesion (meningioma) extending into right orbit causing proptosis. Note the intact medial rectus muscle. (c) Clinical photograph of the same patient with proptosed right eye

Click here to view
Table 1: Clinicoradiological data of patients with proptosis (n=6)

Click here to view



 » Results/observation Top


During routine ophthalmological evaluation, all were noted to have varying degrees of deficiency in convergence. In 2 patients, there was a failure of convergence despite intact adduction [Video 1]. In the remaining 4, the affected eye showed inadequate convergence. When the eyes are focused at a near point, initially convergence (adduction of bilateral medial recti) was seen. However, it was ill sustained and one of the eyeballs quickly drifted away to neutral position [Video 2]. In three patients, the proptosed eye ball drifted away, whereas, in one, this phenomenon was observed in the nonproptosed eye. The aforementioned findings were reproducible in all.





 » Discussion Top


The space-occupying lesions of orbit usually present with proptosis.[5] Proptosis can cause secondary restriction of extraocular muscle movements and ocular malalignment. However, associated findings of convergence deficiency/CI in patients with proptosis are unknown.

Orbital lesions may involve extraocular muscles or the nerve supplying them. In the event of medial rectus or the third nerve involvement, the extraocular movements would be affected and convergence cannot be tested in such patients. However, such neuromuscular involvement is uncommonly seen, and most of the patients have normal extraocular movements. Convergence weakness in these patients is unexpected.

Normally, the presence of intact adduction with convergence weakness points toward dorsal midbrain lesion.[2],[3] It can be a part of spectrum of ocular manifestations in lesions of dorsal midbrain (Parinaud's syndrome) that include upgaze paresis, light near dissociation, and convergence retraction nystagmus. In 3 of our patients, we observed obvious convergence failure and the rest had varying degrees of convergence weakness. MRI excluded any brainstem etiology in all.

Convergence weakness may not be obvious and may be brought about by prolonged near work, termed as convergence insufficiency. Working at a near point requires a fine balance between the convergence and accommodation. If this synchrony is lost, it can lead to muscular fatigue, eye strain, and CI. In CI, there is reduced or inability to maintain the required convergence on a near object and is characterized by exophoria at near point, remote near point of convergence, and reduced positive fusional convergence at near.[4] The possible causes include poor accommodation or convergence, wide interpupillary distance, and presbyopia.[4] Systemic disorders and anxiety neurosis have also been implicated. Weak eye muscles as a cause of CI is less evident.[4]

Near vision consists of three physiological components (near reflex triad) which include convergence, accommodation, and miosis. When an object is brought near in front of eye, the bilateral medial recti muscles contract to bring convergence of eyeball. There is an associated contraction of ciliary muscles (accommodation) that relaxes the zonular lens fibers to increase its convexity. At the same time, the pupils constrict to increase the depth of focus to adjust to near vision.

The exact mechanism of one of the near reflex components (convergence) is not well understood.[1],[2] It is implicated that the cortical neurons arise from area 19 and 22 of occipital cortex, descend down to decussate in thalamo tectal area (para median thalamus). In the midbrain, the vergence premotor neurons (near response cells) are located dorsal and dorsolateral to oculomotor nucleus. From midbrain, the near response cells neurons project to medial rectus muscles.

The patients we report had orbital tumors and showed convergence deficiency/weakness on examination. Brain imaging excluded a central cause in all. Normally, it requires a great effort of extraocular muscles to achieve convergence and more importantly to sustain it. The phenomenon observed in our patients is possibly due to the increased force and endurance that is required to maintain the convergence/adducted state of medial recti muscles in a proptosed eye. Interestingly, one of the patients showed deficient convergence in the contralateral nonproptosed eye. However, such an observation could not be explained.


 » Conclusions Top


The article reports an interesting observation of deficient convergence in the presence of intact medial rectus function in patients with proptosis. Currently, the mechanism (central or peripheral) underlying this phenomenon is unclear. The symmetry of orbital contents possibly plays a significant role in the convergence mechanism.

Compliance with Ethical Requirements

Informed consent was obtained from the patients.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
 » References Top

1.
Mays LE. Neural control of vergence eye movements: Convergence and divergence neurons in midbrain. J Neurophysiol 1984;51:1091-108.  Back to cited text no. 1
    
2.
Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 2007.  Back to cited text no. 2
    
3.
Ito S, Hattori T, Katayama K. Prominent unilateral convergence palsy in a patient with a tiny dorsal midbrain infarction. Eur Neurol 2005;54:163-4.  Back to cited text no. 3
    
4.
Cooper J, Jamal N. Convergence insufficiency-a major review. Optometry 2012;83:137-58.  Back to cited text no. 4
    
5.
Freeman JL, Davern MS, Oushy S, Sillau S, Ormond DR, Youssef AS, et al. Spheno-orbital meningiomas: A 16-year surgical experience. World Neurosurg 2017;99:369-80.  Back to cited text no. 5
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1]



 

Top
Print this article  Email this article
   
Online since 20th March '04
Published by Wolters Kluwer - Medknow