By:Noor Munirah binti Awang Abu Bakar

Optometrist (Moc: O-0869)

Introduction Anatomy Sixth Nerve Palsy

o Incidenceo Etiology o Differential Diagnosiso Clinical Signs & Symptomso Optometric Assessment & Investigationo Other Clinical Assessment & Investigationo Optometric Managemento Other Managementso Prognosis

The sixth cranial nerve is a somatic efferent nerve that innervates ipsilateral lateral rectus (LR) muscle to elicit eye abduction.o Effector organ : LR muscle o Action: Eye abduction

Also called as abducens nerve or abducent nerve or CNVI.

Function: o Solely to innervate the lateral rectus muscle and abduct the

eye.

(Goodwin, 2006)

The sixth nerve nucleus is located in the pons.[Just ventral to the floor of the fourth ventricle and just lateral to the medial longitudinal fasciculus (MLF)]

The sixth nerve contains only somatic efferent fibers.

Runs a long course from the brainstem to the lateral rectus muscle, through the superior orbital fissure and into the orbit through the annular ligament (annulus of Zin) then to the lateral rectus. Functioning to abduct the eyes.

6th nerve- The longest subarachnoid course of all the cranial nerve

The long course of the 6th nerve between the brainstem and the eye makes it vulnerable to injury at many levels.

Close association between 6th nerve and 7th nerve (facial) in the midbrain Facial muscle also been involved in

some 6th nerve palsies.

Sixth nerve palsy

What?: o Limited ability of the affected eye to turn out (abduct) due to 6th

nerve lesion.

Why?:

Classified under neurogenic-cause of incomitant strabimus It can be congenital (rare) or acquired (common). Can be unilateral or bilateral 6th nerve palsy.

Right gaze: Complete RE lateral rectus palsy Left gaze: Complete LE lateral rectus palsy

Primary gaze: Mild bilateral esotropia

Bilateral 6th nerve palsy

(Adapted from Hamidon et al. 2012)

Sixth nerve palsy

Total palsy (paralysis)

Partial palsy

(paresis)

Presence of abduction past the

midline

Failure of abduction past the midline

Sclera is visible on L

gaze  HOW TO DIFFERENTIATE????

The sixth cranial nerve is the most commonly affected of the ocular motor nerves based on some studies.

But ranking second following fourth nerve palsy according to other reports.

Most patients who develop acute CN VI palsy are older than 50 years of age. This group often has a concurrent history of hypertension and/or diabetes.

(Acaroglu et al., 2008 & Richards et al., 1992)

Children are also prone to develop CN VI palsy. The causes may range from benign (e.g., viral illness or trauma) to malignant etiologies.

(Janssen et al. 2008)

Young adults aged 20 to 50 years also can have CN VI palsy due to neurologically complicated CN VI palsies involving additional cranial nerves (such as III and IV) or other neurological signs (such as ataxia or intention tremors).

(Brinar et al., 2007)

Lesions can affect any part of the nerve’s pathway.o Usually due to direct damage of the sixth cranial nerve,

encephalon nuclei or less frequently diffuse axonal damage. (Hamidon et al.

2012)

It can be congenital (rare) or acquired (common).

Identifying the causative factor is important for further management.

The four most common causes were idiopathic (26%), hypertension alone (19%), coexistent diabetes and hypertension (12%), and trauma (12%).

(Patel et al., 2004)

(Patel SV, Mutyala S, Leske DA, et al. Incidence, associations, and evaluation of sixth nerve palsy using a population-based method. Ophthalmology. 2004 Feb;111(2):369-75) 

More common Less common Idiopathic Multiple sclerosis

Vasculopathic (diabetes, hypertension, atheroscl

erosis)Increased intracranial pressure

Trauma Sarcoidosis/vasculitisStroke (usually not isolated)

Lumbar punctureMyasthenia GravisGiant cell arteritis

o Acquired

o Acquired• Traumatic • Tumour• Idiopathic• Infection

o Congenital• Very rare• If occurs as an isolated finding in the first week, usually

resolves spontaneously. (Reisner et al. 1971)• May represent one of following: Duane syndrome, infantile

esotropia, nystagmus blockage syndrome (Ansons & Davis, 2014)

DIFFERENTIAL DIAGNOSIS

WHY

Duane’s retraction syndrome

Difficulty on ABD & ADD with eyelid retraction

Grave’s orbitopathy (TED)

Proptosis + decreased ability of eye movement + diplopia

Orbital trauma Orbital fracture + Muscle swelling + eye restriction ABD & ADD + diplopia

Infantile esotropia Esotropia + limit in ABD (improve after doll’s head maneuver) + IO overaction + nystagmus + vertical deviation

Spasm of the near reflex

Triad of intermittent : conv. strabismus + acc. Spasm + miosis

Myasthenia Gravis Muscle restriction, diplopia & ptosisHigh myopia Can lead to progressive loss of abduction

(Ansons & Davis, 2014)

** ABD: abduct & ADD: adduct

Patient adopt face turn towards the affected eye (Right side)

Control diplopia

Maintaining BSV

Diplopia with ET : 5 uncrossed dots seen in 6th nerve palsy

Abduct to R gaze

Abduct to L gaze

LE sixth nerve palsy

Source: Kirtpatrick, C. Cranial Nerve 6 (Abducens Nerve) Palsy Secondary to Schwannoma

Abduct to R gaze

Abduct to L gaze

Bilateral sixth nerve palsy

Source: Kirtpatrick, C. Bilateral Cranial Nerve VI (Abducens Nerve) Palsies Secondary to Retroclival Hematoma

Diagnosis: RE 6th nerve palsy

•The constricted RE field demonstrates LR underaction.

•Contralateral MR overaction.

•The central point is shifted in both eyes indicating diplopia in primary gaze.

Diagnosis: LE Duane syndrome

WHY?:The field compressed vertically mechanical palsy

LE 6th nerve palsyDiagnosis:

Muscle function test + How to differentiate total or partial sixth nerve palsy

(Azarmina, 2013)

Binasal occlusiono Type of sector occlusiono Not as a permanent treatmento Indication: Esotropia, amblyopia, diplopia, CE, DIo Why recommended :

• Reduce double vision and direct patients to use their peripheral system, helping them to locate objects and judge distances more accurately

o Material : Translucent material (opaque) , clear nail polish, black tape

o Sector size measurement:• Pt wear the glasses, focus at distant target• Binasal occluder (determine the degree of nasal occlusion

needed to eliminate or reduce symptoms ) is put at the centre until diplopia disapppear

Monocular occlusionoMethod of full patch

covering affected eye.o Purpose: Remove

diplopia in lateral gazeoMaterial: Occluder with

different grades (Bangerter foils)

(Azarmina, 2013)

Detach-Remove-Reattach

Move –Reattach

posteriorly

Approximately half of all 6th nerve palsies recover spontaneously approx. 3 months after onset. (Goodwin, 2006)

Patient with vasculopathic 6th nerve palsy have a better chance of recovery (69% to 86%) & recover more rapidly (4 to 6 weeks) than pt with 6th nerve palsy from other causes. (Goodwin, 2006)

A report of over 2000 patients with 6th nerve palsy of unknown etiology found that 36% recovered in 8 weeks (2 months) and 84% recovered in 4 months. (King et al. 1995)

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2. Azarmina, M., & Azarmina, H. (2013). The Six Syndromes of the Sixth Cranial Nerve.  Journal of Ophthalmic & Vision Research, 8(2), 160–171.

3. Bagheri, A., Babsharif, B., Abrishami, M., Salour, H., & Aletaha, M. (2010). Outcomes of Surgical and Non-Surgical Treatment for Sixth Nerve Palsy.Journal of Ophthalmic & Vision Research, 5(1), 32–37.

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5. Goodwin, D. (2006). Differential Diagnosis and Management of Acquired Sixth Cranial Nerve Palsy. Optometry. 2006 Nov;77(11):534-9.PMID: 17145564

6. Holmes JM, Leske DA, Christiansen SP: Initial treatment outcomes in chronic sixth nerve palsy. J AAPOS 5:370–376, 2001

7. Janssen K, Wojciechowski M, Poot S, et al. Isolated abducens nerve palsy after closed head trauma: a pediatric case report. Pediatr Emerg Care. 2008 Sep;24(9):621-3. 

8. Patel SV, Mutyala S, Leske DA, et al. Incidence, associations, and evaluation of sixth nerve palsy using a population-based method. Ophthalmology. 2004 Feb;111(2):369-75. 

9. Richards BW, Jones FR Jr, Younge BR. Causes and prognosis in 4,278 cases of paralysis of the oculomotor, trochlear, and abducens cranial nerves. Am J Ophthalmol. 1992 May;113(5):489-96. 

10. Von Noorden GK, Campos EC. Paralytic strabismus. In: Von Noorden GK, Campos EC (eds). Binocular vision and ocular motility. 6th ed. New York: CV Mosby; 2002: 414-457.

Thank you