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| ==Introduktion== | | ==Introduktion== |
| Abducens parese eller parese af den 6. kranienerve medfører reduceret eller manglende funktion af m. rectus lateralis og der med problemer med at abducerer øjet - hvilket medfører dobbeltsyn kigger mod den paretiske side. Det vil være horisontalt dobbeltsyn hvor de to billeder er placeret ved siden af hinanden. | | Abducens parese eller parese af den 6. kranienerve medfører reduceret eller manglende funktion af m. rectus lateralis og der med problemer med at abducerer øjet - hvilket medfører dobbeltsyn kigger mod den paretiske side. Det vil være horisontalt dobbeltsyn hvor de to billeder er placeret ved siden af hinanden. |
| Abducens pareser er i almindelighed oftetst ensidige men blandt neurokirurgiske patienter er bilaterale abducenspareser ikke sjældne, da begge abducens nerver kan bliver strukket ved forhøjet intrakranielt tryk i det supratentorielle rum, som skubber hjernestammen kaudalt hvor ved n.abducens bliver strukket fra dens udløb af hjernestammens forside ti dens indløb i Dorellos kanal i dura på Clivus. | | Abducens pareser er i almindelighed oftetst ensidige men blandt neurokirurgiske patienter er bilaterale abducenspareser ikke sjældne, da begge abducens nerver kan bliver strukket ved forhøjet intrakranielt tryk i det supratentorielle rum, som skubber hjernestammen kaudalt hvor ved n.abducens bliver strukket fra dens udløb af hjernestammens forside (ponto-medullære overgang) til dens indløb i Dorellos kanal i dura på Clivus. |
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| ==Karakteristika== | | ==Karakteristika== |
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| I subarachnoidalrummet fra hjernestammen til indgangen i Dorellos kanal kan abducens nerven både blive strukket (forhøjet ICP) eller komprimeret mod Clivus, eksempelvis af aneurysme fra a. Basilaris eller a. cerebelli inferior. | | I subarachnoidalrummet fra hjernestammen til indgangen i Dorellos kanal kan abducens nerven både blive strukket (forhøjet ICP) eller komprimeret mod Clivus, eksempelvis af aneurysme fra a. Basilaris eller a. cerebelli inferior. |
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| '''3. Petrous apex''' | | '''3. Peks pars petrosa''' |
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| N.Abducens løber tæt forbi sinus mastoideus og kan blive påvirket ved mastoiditis med meningeal inflammation, ses da ofte sammen med reduceret hørelse på samme side, ansigts smerte, facialis parese /paralyse og fotofobi (Gradenigo's syndrome). Lignende symptomer kan ses ved frakturer af pars petrosa og nasofaryngs tumorer. | | N.Abducens løber tæt forbi sinus mastoideus og kan blive påvirket ved mastoiditis med meningeal inflammation, ses da ofte sammen med reduceret hørelse på samme side, ansigts smerte, facialis parese /paralyse og fotofobi (Gradenigo's syndrome). Lignende symptomer kan ses ved frakturer af pars petrosa og nasofaryngs tumorer. |
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| N.Abducens har et kort forløb i øjenhulen og det er sjældent at abducens parese stammer fra denne region | | N.Abducens har et kort forløb i øjenhulen og det er sjældent at abducens parese stammer fra denne region |
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| ==Differential diagnoser==
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| Differential diagnosis is rarely difficult in adults. Onset is typically sudden with symptoms of horizontal diplopia. Limitations of eye movements are confined to abduction of the affected eye (or abduction of both eyes if bilateral) and the size of the resulting convergent squint or esotropia is always larger on distance fixation - where the lateral rectii are more active - than on near fixation - where the medial rectii are dominant. Abduction limitations which mimic VIth nerve palsy may result secondary to surgery, to trauma or as a result of other conditions such as [[myasthenia gravis]] or [[thyroid eye disease]].
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| In children, differential diagnosis is more difficult because of the problems inherent in getting infants to cooperate with a full eye movement investigation. Possible alternative diagnosis for an abduction deficit would include:
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| 1. [[Mobius syndrome]] - a rare congenital disorder in which both VIth and VIIth nerves are bilaterally affected giving rise to a typically 'expressionless' face.
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| 2. [[Duane's syndrome]] - A condition in which both abduction and adduction are affected arising as a result of partial innervation of the lateral rectus by branches from the IIIrd oculomotor cranial nerve.
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| 3. Cross fixation which develops in the presence of [[infantile esotropia]] or [[nystagmus blockage syndrome]] and results in habitual weakness of lateral rectii.
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| 4. Iatrogenic injury. Abducens nerve palsy is also known to occur with halo orthosis placement.The resultant palsy is identified through loss of lateral gaze after application of the orthosis and is the most common cranial nerve injury associated with this device.<ref>http://www.orthobullets.com/spine/2019/halo-orthosis-immobilization</ref>
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| ==Management==
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| The first aims of management should be to identify and treat the cause of the condition, where this is possible, and to relieve the patient's symptoms, where present. In children, who rarely appreciate [[diplopia]], the aim will be to maintain binocular vision and, thus, promote proper visual development.
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| Thereafter, a period of observation of around 9 to 12 months is appropriate before any further intervention, as some palsies will recover without the need for surgery.
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| ===Symptom relief and/or binocular vision maintenance===
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| This is most commonly achieved through the use of fresnel prisms. These slim flexible plastic prisms can be attached to the patient's glasses, or to plano glasses if the patient has no refractive error, and serve to compensate for the inward misalignment of the affected eye. Unfortunately, the prism only correct for a fixed degree of misalignment and, because the affected individual's degree of misalignment will vary depending upon their direction of gaze, they may still experience diplopia when looking to the affected side. The prisms are available in different strengths and the most appropriate one can be selected for each patient. However, in patients with large deviations, the thickness of the prism required may reduce vision so much that binocularity is not achievable. In such cases it may be more appropriate simply to occlude one eye temporarily. Occlusion would never be used in infants though both because of the risk of inducing stimulus deprivation [[amblyopia]] and because they do not experience [[diplopia]].
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| Other management options at this initial stage include the use of [[botulinum toxin]], which is injected into the ipsilateral medial rectus ([[botulinum toxin therapy of strabismus]]). The use of BT serves a number of purposes. Firstly, it helps to prevent the contracture of the medial rectus which might result from its acting unopposed for a long period. Secondly, by reducing the size of the deviation temporarily it might allow prismatic correction to be used where this was not previously possible, and, thirdly, by removing the pull of the medial rectus it may serve to reveal whether the palsy is partial or complete by allowing any residual movement capability of the lateral rectus to operate. Thus, the toxin works both therapeutically, by helping to reduce symptoms and enhancing the prospects for fuller ocular movements post-operatively, and diagnostically, by helping to determine the type of operation most appropriate for each patient.
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| ===Longer term management===
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| Where full recovery has not occurred after the 9 to 12 month 'watch and wait' period, management will take either a 'conservative' or a surgical course.
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| '''1. Conservative management'''
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| Where the residual esotropia is small and there is a risk of surgical overcorrection, or where the patient is unfit or unwilling to have surgery, prisms can be incorporated into their glasses to provide more permanent symptom relief. Where the deviation is too large for prismatic correction to be effective, permanent occlusion may be the only option for those unfit or unwilling to have surgery.
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| '''2. Surgery'''
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| The procedure chosen will depend upon the degree to which any function remains in the affected lateral rectus. Where there is complete paralysis, the preferred option is to perform vertical muscle transposition procedures such as Jensen's, Hummelheim's or whole muscle transposition, with the aim of using the functioning inferior and superior recti to gain some degree of abduction.<ref>Bansal S, Khan J, Marsh IB.Unaugmented vertical muscle transposition surgery for chronic sixth nerve paralysis.Strabismus. 2006 Dec;14(4):177-81</ref><ref>Britt MT, Velez FG, Thacker N, Alcorn D, Foster RS, Rosenbaum AL.Partial rectus muscle-augmented transpositions in abduction deficiency.J AAPOS. 2003 Oct;7(5):325-32.</ref><ref>Neugebauer A, Fricke J, Kirsch A, Rüssmann W. Modified transposition procedure of the vertical recti in sixth nerve palsy.
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| Am J Ophthalmol. 2001 Mar;131(3):359-63</ref> An alternative, and less satisfactory, approach is to operate on both the lateral and medial rectii of the affected eye, with the aim of stabilising it at the midline, thus giving single vision straight ahead but diplopia on both left and right gaze. This procedure is rarely used, but might be appropriate for those with total paralysis who, because of other health problems, are at increased risk of the anterior segment ischaemia associated with complex multi-muscle transposition procedures.
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| Where some function remains in the affected eye, the preferred procedure depends upon the degree of development of muscle sequlae. In a sixth nerve palsy one would expect that, over the 9 to 12 month observation period, most patients would show the following pattern of changes to their ocular muscle actions: firstly, an overaction of the medial rectus of the affected eye, then an overaction of the medial rectus of the contraletral eye and, finally, an underaction of the lateral rectus of the unaffected eye - something known as an inhibitional palsy. These changes serve to reduce the variation in the misalignment of the two eyes in different gaze positions (incomitance). Where this process has fully developed, the preferred option is a simple recession, or weakening, of the medial rectus of the affected eye, combined with a resection, or strengthening, of the lateral rectus of the same eye. However, where the inhibitional palsy of the contralateral lateral rectus has not developed, there will still be gross incomitance, with the disparity between the eye positions being markedly greater in the field of action of the affected muscle. In such cases recession of the medial rectus of the affected eye is accompanied by recession and/or fadenisation of the contraleral medial rectus.
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| The same approaches are adopted bilaterally where both eyes have been affected.
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| ==See also==
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| * [[Congenital fourth nerve palsy]]
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| ==References==
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| {{reflist}}
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| * "Cranial Mononeuropathy VI", Medline Plus Medical Encyclopedia.[http://www.nlm.nih.gov/medlineplus/ency/article/000690.htm]
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| * "Cranial Nerve VI Palsy", ''Handbook of Ocular Disease Management'', 2000 - 2001 Jobson Publishing L.L.C. (2000–2001).[http://www.revoptom.com/handbook/sect6e.htm]
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| * ''The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease'', J.B. Lippincott, 1994.
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| ==External links== | | ==External links== |
| * [http://www.mrcophth.com/eyeclipartchua/6nervepalsy.html Animation] at mrcophth.com | | * [http://www.mrcophth.com/eyeclipartchua/6nervepalsy.html Animation] at mrcophth.com |
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| {{#ev:youtube|rVNuF6-aH_s|700}} | | {{#ev:youtube|rVNuF6-aH_s|700}} |
Introduktion
Abducens parese eller parese af den 6. kranienerve medfører reduceret eller manglende funktion af m. rectus lateralis og der med problemer med at abducerer øjet - hvilket medfører dobbeltsyn kigger mod den paretiske side. Det vil være horisontalt dobbeltsyn hvor de to billeder er placeret ved siden af hinanden.
Abducens pareser er i almindelighed oftetst ensidige men blandt neurokirurgiske patienter er bilaterale abducenspareser ikke sjældne, da begge abducens nerver kan bliver strukket ved forhøjet intrakranielt tryk i det supratentorielle rum, som skubber hjernestammen kaudalt hvor ved n.abducens bliver strukket fra dens udløb af hjernestammens forside (ponto-medullære overgang) til dens indløb i Dorellos kanal i dura på Clivus.
Karakteristika
Patienten vil oftest roteret hovedet mod den paretiske side så de kigger lidt væk fra den paretiske side, for der ved at undgå dobbeltsyn
Børn oplever ikke altid dobbeltsyn da de undertrykker synsindtryk fra det ene øje.
Årsager
De mest almindelige årsager til abducens parese hos voksne:
- Vasculopati (diabetisk, hypertensiv, arteroskerose
- Traume
- Øget ICP
- Tumor i sinus cavernosus
- Gigant celle arteritis
- Aneurysme
- Tumor i hjernestamme
- Multiple sklerose
- Sarcoidose
- Carcinomatosis
- Chiari malformation
Lokaliserende tegn
1. Hjernestamme
Hjernestamme læsioner vil ikke give anledning til solitær abducens parese, der vil typisk også være en n. facialis parese og en modsidig hemiparese.
2. Subarachnoidal rummet
I subarachnoidalrummet fra hjernestammen til indgangen i Dorellos kanal kan abducens nerven både blive strukket (forhøjet ICP) eller komprimeret mod Clivus, eksempelvis af aneurysme fra a. Basilaris eller a. cerebelli inferior.
3. Peks pars petrosa
N.Abducens løber tæt forbi sinus mastoideus og kan blive påvirket ved mastoiditis med meningeal inflammation, ses da ofte sammen med reduceret hørelse på samme side, ansigts smerte, facialis parese /paralyse og fotofobi (Gradenigo's syndrome). Lignende symptomer kan ses ved frakturer af pars petrosa og nasofaryngs tumorer.
4. Sinus Cavernosus sinus/Fissura Orbitalis Superior
N.Abducens løber ved siden af a. carotis interna i sinus cavernosus og der med ved siden af den sympatiske fibre der kommer fra grænsestrengen. Skader i denne region kan derfor være associeret med pupilær dysfunktion
Horners syndrom, ligesom de andre kranienerver i sinus cavernosus kan være påvirket (III, IV, V1, and V2). Abducens påvirkning i dette område kan skyldes aneusyme, sinus trombose, inflammation, tumor (meningeom, metastase).
5. Orbit
N.Abducens har et kort forløb i øjenhulen og det er sjældent at abducens parese stammer fra denne region
External links
{{#ev:youtube|rVNuF6-aH_s|700}}
--Jannick Brennum 28. dec 2015, 11:41 (UTC)