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Year : 2021  |  Volume : 59  |  Issue : 2  |  Page : 226-227

Head Canting – A Motor Adaptation

Department of Paediatric ophthalmology and Strabismus, Aravind Eye Hospital, Puducherry, India

Date of Submission13-Aug-2020
Date of Acceptance30-Aug-2020
Date of Web Publication24-Jun-2021

Correspondence Address:
Dr. Bharat Gurnani
Aravind Eye Hospital, Cuddalore Main Road, Thavalakuppam, Puducherry - 605 007
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/tjosr.tjosr_111_20

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How to cite this article:
Kaur K, Mouttapa F, Gurnani B. Head Canting – A Motor Adaptation. TNOA J Ophthalmic Sci Res 2021;59:226-7

How to cite this URL:
Kaur K, Mouttapa F, Gurnani B. Head Canting – A Motor Adaptation. TNOA J Ophthalmic Sci Res [serial online] 2021 [cited 2021 Aug 5];59:226-7. Available from: https://www.tnoajosr.com/text.asp?2021/59/2/226/319261

A 21-year-old boy presented with the complaints of difficulty in reading for the past 3 months. Snellen's visual acuity was 20/20 in both the eyes. Anterior segment examination was normal, except abnormal eye movements and a V-pattern exotropia [Figure 1]. Fundoscopy revealed an extortion of the macula in the right eye [Figure 2]. The patient had a 10° left-sided head tilt. Binocular single vision was intact, and a stereopsis of 120° was present. Squint evaluation revealed right eye 10 prism diopters (PDs) of exotropia and 12 PDs of hypertropia, and the hypertropia increased on left gaze and right head tilt. Vertical fusional amplitude test revealed 12 PDs of fusional amplitudes.
Figure 1: Clinical image of the patient showing 9 gaze ocular movements showing an underacting right superior oblique, an overacting left inferior rectus, and right inferior oblique muscle

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Figure 2: Fundus image of the right eye showing extortion of the macula and fundus image of the left eye showing normal position of the macula in relation to the optic disc

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  1. What is the most probable diagnosis?

    1. Inferior oblique overaction
    2. Recent-onset fourth nerve palsy
    3. Congenital fourth nerve palsy
    4. Habitual head tilt.

  2. Choose the correct muscle sequelae in long-standing cases?

    1. Overaction of ipsilateral inferior rectus muscle (Herring's law)
    2. Overaction of contralateral inferior rectus muscle (Herring's law)
    3. Underaction of ipsilateral inferior oblique (Sherington's law)
    4. Overaction of ipsilateral inferior oblique (Herring's law).

  3. How will you manage this patient?

    1. Observation as this condition might resolve over course of time
    2. Weaken/recess the left inferior oblique muscle
    3. Strengthen/tuck the yoke contralateral inferior rectus muscle
    4. Strengthen/tuck the right superior oblique.

  4. What differentiates bilateral from unilateral palsy?

    1. Positive Bielschowsky head tilt test on tilting head toward either shoulder
    2. V pattern of 15 PD
    3. More obvious head tilt toward one side
    4. Double Maddox rod revealing an excyclotorsion of 5°.


A. c; B. b; C. d; D. a.

  Discussion Top

Fourth nerve palsy is the most common congenital cranial nerve palsy.[1] It is physically slender, has the longest intracranial course, and is subject to traumatic damage. Fourth nerve palsy results in characteristic motility patterns including elevation in adduction, V-pattern related to reduced abduction force in downgaze, and excyclotorsion. Patients often acquire a contralateral head tilt for unilateral palsy and chin down head posture for bilateral palsy.[2] The common muscle sequelae following long-standing cases include overaction of the contralateral inferior rectus (Herring's law), overaction of the ipsilateral inferior oblique (Sherrington's law), and secondary inhibitional palsy of the contralateral superior rectus.

The characteristic findings of a decompensated congenital fourth nerve palsy include a long-standing head tilt, overaction of the ipsilateral inferior oblique in adduction, and a large vertical fusional amplitude of 10–15 PDs (normal vertical fusional amplitude is between 2 and 3 PDs).[3] Because in this patient there is only a mild head tilt, and no diplopia in primary and downgaze, observation can be planned. If needed, the surgical options include strengthening the affected superior oblique muscle, weakening the antagonist ipsilateral inferior oblique muscle, or weakening the yoke contralateral inferior rectus muscle.[4] Bilateral fourth nerve palsy presents with a crossed hypertropia, excyclotorsion of 10° or greater, and a large (≥25 PD) V-pattern of strabismus.[5]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/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.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Holmes JM, Mutyala S, Maus TL, Grill R, Hodge DO, Gray DT. Pediatric third, fourth, and sixth nerve palsies: A population-based study. Am J Ophthalmol 1999;127:388-92.  Back to cited text no. 1
Lyons CJ, Godoy F, ALQahtani E. Cranial nerve palsies in childhood. Eye (Lond) 2015;29:246-51.  Back to cited text no. 2
Astle WF, Rosenbaum AL. Familial congenital fourth cranial nerve palsy. Arch Ophthalmol 1985;103:532-5.  Back to cited text no. 3
Knapp P. Classification and treatment of superior oblique palsy. Am Orthopt J 1974;24:18-22.  Back to cited text no. 4
Lee AG. Seven Easy Steps in Evaluation of Fourth-Nerve Palsy in Adults. Ophthalmol Times; 2004. Available from: https://www.ophthalmologytimes.com/article/seven-easy-steps-evaluation-fourth-nerve-palsy-adults. [Last accessed on 2020 Aug 09].  Back to cited text no. 5


  [Figure 1], [Figure 2]


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