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Click on any of the headings or subheadings to rapidly navigate to the relevant section of the guidemap
History of the present illness
Examination Medical decision-making- Cover-uncover test
- Duction testing
- Forced duction testing
- Abbreviated red glass lens testing
- Parks-Bielchowsky three-step testing
- 3rd cranial nerve palsy
- 4th cranial nerve palsy
- 6th cranial nerve palsy
- Bilateral EOM palsies
- definitions
- actions of extraocular muscles
- Hering's law
- single cover and uncover tests
- differential diagnosis of painful opthalmoplegia
- likely causes of extraocular nerve pathology
- likely cranial nerve involvement based on site of the pathology
| Introduction |
- this guidemap will hopefully help an ED physician solve the clinical dilemma of "double vision" in an ED setting, without requiring any specialized equipment other than a red glass lens
- if an ED physician cannot effectively follow the sequenced approach described in the medical decision-making section of the guidemap => he should simply refer patients with monocular diplopia semi-urgently to an opthalmologist, and refer patients with binocular diplopia emergently to a neurologist
| History of the present illness |
- determine when the patient first became aware of the "double vision" and determine whether the diplopia is constant in its time course or whether it only occurs after prolonged reading or extended near-work
(* myasthenia gravis may produce diplopia, which fluctuates in intensity and increases in severity with fatigue; associated episodic neurological symptoms are also likely present eg. droopy eyelids, dyspahgia, dysarthria, dyspnea, proximal muscle weakness)
- ask the patient whether there has been any recent change in prescription lenses (particularly first time use of bifocal prescription lenses or reading glasses), or whether the patient has been using a jeweler's loupe or whether the patient has been performing extended near-work eg. embroidery, or whether the patient has used a video camera outdoors in bright light for a prolonged period - they are all associated with transient diplopia
(* sudden use of convex lenses for near work => may induce a convergence insufficiency => eyes tends to wander outwards => transient diplopia, which may be bilateral)
- a history of strabismus in the past suggests that a patient with a previous heterophoria (a latent deviation of the eye which is unmasked when binocular vision is interrupted) could have suddenly started to use the other eye for visual fixation causing sudden diplopia (fixation switch diplopia)
- determine whether the patient knows if the diplopia is monocular or binocular, and if monocular => which eye is causing the double vision
(* monocular diplopia is usually caused by eye pathology, while binocular diplopia is usually caused by neuromuscular pathology)
- ask the patient whether the ghost image is horizontally situated alongside the other image or obliquely related to the other image or vertically related to the other image
(* horizontal diplopia is caused by weakness of the medial or lateral rectus muscles, while oblique/vertical diplopia is caused by weakness of any of the other EOM's)
- ask the patient whether tilting the head worsens or improves the diplopia
(* vertical-oblique diplopia that improves with contra-lateral head tilt and worsens with ipsilateral head tilt suggests a 4th cranial nerve lesion; the diplopia is also worse when reading a book, going down stairs or watching TV between the legs while lying horizintally in bed)
- ask the patient whether the diplopia (degree of seperation of the images) is worse in any particular direction of gaze
(* the diplopia is usually at its worst when conjugate gaze is in the direction requiring maximal involvement of the paretic eye muscle eg. horizontal diplopia that is worse on right lateral gaze suggests weakness of the right lateral rectus muscle or left medial rectus muscle)
- ask the patient if the diplopia is worse with distant or near vision
(* lateral rectus muscle weakness usually produces diplopia that is worse on distant gaze, while weakness of the obliques and medial rectus muscle produce diplopia that is worse during adduction and near-vision)
- inquire about any associated visual field impairment or loss of vision
(* optic nerve dysfunction + diplopia suggests intra-orbital or parasellar pathology)
- ask the patient about symptoms of other cranial nerve dysfunction or other abnormal neurological symptoms (dysarthria, dysphagia, face weakness or numbness or hyperalgesia, decreased hearing, ataxia, sensorimotor deficits of the limbs)
(* helps localize the probable site of the pathology - by the "company it keeps")
- ask the patient about recent headaches or peri-orbital pain
(* suggests serious pathology requiring emergent neuro-imaging)
- inquire about symptoms of specific underlying diseases (myasthenia gravis, thyroid disease, diabetes, hypertension, multiple sclerosis)
- inquire about recent face or head injury
(* orbital fractures => EOM entrapment => restrictive diplopia, and/or
basal skull fractures => EOM cranial nerve injury)
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Diplopia
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| Examination |
- first note whether the patient's ocular alignment is normal or whether there is any overt depression (hypotropia) or elevation (hypertropia) of one eye, or any horizontal deviation of one eye, and whether there is any associated intorsion/extorsion (cyclotorsion) of the eyeball
(* ocular misalignment could be due to palsies of the cranial nerves innervating the EOM's, weakness of the EOM muscles, intra-orbital compressive/restrictive processes interfering with EOM function, or skew deviations secondary to brain stem pathology)
- minor degrees of ocular misalignment in primary gaze can be detected by asking the patient to look at a bright penlight held ~ 14" in front of his face => look for the pinpoint light reflex on the cornea
- if the light reflex is decentered nasally, it implies that the eye is deviated laterally (exotropia) => suggests that the muscle (medial rectus) moving the eye medially may be weak
- if the light reflex is decentered temporally, it implies that the eye is deviated medially (esotropia) => suggests that the muscle (lateral rectus) moving the eye laterally may be weak
- if the light reflex is decentered superiorly, it implies that the eye is deviated downwards (hypotropia) => suggests that the muscles (inferior oblique or superior rectus) moving the eye upwards are weak
- if the light reflex is decentered inferiorly, it implies that the eye is deviated upwards (hypertropia) => suggests that the muscles (superior oblique or inferior rectus) moving the eye downwards are weak
(* the corneal light reflex test is a very sensitive test of ocular misalignment and 1mm of decentration is equal to ~ 7 degrees of ocular deviation)
- determine whether there is any associated proptosis, ptosis, or anisocoria
(* proptosis implies intra-orbital pathology eg. thyroid orbitopathy or intra-orbital tumor/edema/bleeding or cavernous sinus thrombosis; ptosis may be suggestive of Horner's syndrome or oculomotor nerve dysfunction or a myopathy eg. myasthenia gravis; anisocoria could be secondary to a Horner's syndrome or oculomotor nerve dysfunction)
- determine whether the patient assumes a head tilting position to reduce the diplopia
(* implies a compensatory mechanism in patients with binocular vertical diplopia eg. 4th cranial nerve palsy => head is usually tilted angularly away from the involved side)
- ask the patient to cover one eye and determine whether the diplopia (in the 9 cardinal directions of gaze) is related to only one eye (monocular diplopia), or whether the diplopia is only present when both eyes are open (binocular diplopia)
(* checking for diplopia should be done in primary forward gaze and then grossly in all the other 8 cardinal directions of gaze - left, right, up, down, left-and-up, left-and-down, right-and-up, right-and-down)
- if the diplopia is monocular => determine whether the diplopia is improved or eliminated by using a multiple pinhole device
- a multiple pinhole device usually corrects monocular diplopia unless the ocular pathology is extensive; monocular diplopia that persists despite closing either eye, but improves with pinhole suggests one of the following:-
- monocular diplopia from uncorrected refractive error
- optical aberrations of the ocular media
- retinal disorders that distort the fovea
(* on right and left lateral gaze => the sclerae should disappear into the canthus completely; on upward gaze => one half of the cornea should disappear behind the upper eyelid; on downward gaze => two-thirds of the cornea should disappear behind the lower eyelid)
- if the patient has binocular diplopia, specifically determine whether the diplopia is the same in all directions of gaze (comitant diplopia), or whether it is markedly increased in a particular direction of gaze (incomitant diplopia)
- if the patient has incomitant binocular diplopia => determine in which direction of gaze the diplopia is maximal and inquire whether the false ghost image is situated horizontally alongside the true image or whether it is situated obliquely/vertically with respect to the true image
(* the false image is usually less distinct than the true image and is always situated more peripherally)
- check the visual acuity and confrontational visual fields
- perform a complete neurological examination and ensure that you thoroughly check the function of cranial nerves 3, 4, 5, 6, 7 and 8 for any subtle deficits in patients with incomitant binocular diplopia
(* carefully check the corneal reflex and light touch in areas supplied by V1 and V2 if superior orbital fissure syndrome, orbital apex syndrome or cavernous sinus syndrome is suspected)
- perform a slit lap examination and check the cornea and anterior
chamber for any pathology in the visual axis of the eye; and then check
the lens and posterior chamber and retina of the eye using a direct
opthalmoscope
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Ocular alignment
Ptosis, proptosis, anisocoria Version testing - 9 directions of gaze Duction testing - 9 directions of gaze Check for the presence of diplopia
Pupil size and reactivity Confrontational visual field testing Eye examination and fundoscopy Neurological examination
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| Medical decision-making |
- first determine whether the patient has monocular or binocular diplopia
- monocular diplopia implies that the defect lies within the affected eye and not the neuromuscular pathways involved in eye movements => concentrate your search on the eye examination => refer the patient semi-urgently to an opthalmologist if an obvious eye abnormality cannot be detected
- monocular diplopia may also be a common presentation of a hysterical conversion syndrome, which is a diagnosis of exclusion after local eye pathology has been excluded
- common causes of monocular diplopia include (from anterior-to-posterior):-
- eyelid lesions distorting the corneal surface
- corneal astigmatism, corneal defects or foreign bodies within the cornea
- anterior chamber opacities eg. iritis
- lens subluxation or lens opacities
- vitreous opacities or retractions
- retinal distortions eg. subretinal edema, retinal detachments or macular cysts
- binocular diplopia may be comitant (diplopia, and any accompanying ocular deviation, does not increase in any particular direction of gaze) or incomitant (diplopia, and any accompanying ocular deviation, increases in certain directions of gaze)
- comitant binocular dipopia is usually not due to acquired neurological disease and the patient can be referred to an opthalmologist for further analysis and treatment
- incomitant binocular diplopia implies a defect in conjugate eye movements and is secondary to pathology of the extra-ocular eye muscles or the neurological system controlling conjugate eye movements
- if the patient has gross dysfunction of the cranial nerves responsible for conjugate eye movements => the specific diagnosis may become readily apparent during the gross physical examination and during version testing
- gross dysfunction of the 3rd cranial nerve => the patient has vertical and horizontal diplopia; the involved eye faces down and outwards on primary forward gaze and the patient cannot adduct or elevate the involved eye (medial rectus, superior rectus, inferior rectus and inferior oblique muscles involved => failure of adduction and elevation of the eye); ptosis and mydriasis are usually also present
- gross dysfunction of the 4th cranial nerve => the patient has vertical/oblique diplopia; there may be elevation (hypertropia) of the involved eye and the involved eye cannot look look down and medially (superior oblique muscle involved => failure of intorsion and depression of the eye)
(* the patient usually complains of diploplia especially when walking down stairs, watching TV between his legs when lying horizonally on a bed, or when doing "near work" that requires adduction and intorsion of the eye)
- gross dysfunction of the 6th cranial nerve => the patient has horizontal uncrossed diplopia, which is worse on distant vision; the involved eye may be deviated nasally on primary gaze (esotropia) and the involved eye cannot abduct laterally to the ipsilateral side (lateral rectus muscle involved => failure of abduction)
- if the patient has gross dysfunction of EOM eye movements that are not characteristic of a specific cranial nerve 3, 4 or 6 pathology => consider multiple EOM cranial nerve(s) pathology, or EOM polymyopathy or restrictive intra-orbital processes interfering with extraocular muscle movements
(* the likely pathology depends on the associated clinical features eg. bilateral exopthalomos with bilateral lid retractions and bilaterally impaired EOM movements in a patient with an enlarged thyroid gland => thyroid orbitopathy)
- if the patient does not have overt dysfunction of EOM movements during version testing => you have to use more sophisticated testing techniques (cover-uncover testing, red glass testing, duction testing, and the Parks-Bielschowsky three-step test) to detect a more subtle defect in EOM movements, which cannot readily be detected by simply observing the gross eye movements during version testing
- although it is difficult and time-consuming to perform these sophisticated tests, it is critically important to correctly diagnose an acute (new-onset) EOM cranial nerve palsy => immediate neuro-imaging may be required to diagnose a life-threatening problem
- start the sophisticated testing series by performing version testing to determine in which direction of gaze the greatest degree of diplopia exists, and then use the cover-uncover test in that same direction of gaze to determine whether you can unmask any objective evidence of ocular misalignment
- ask the patient to look at your finger held ~ 14" in front of his face and ask the patient to follow your finger into the 9 cardinal gaze positions => look for any indication that one eye is not moving completely in a particular direction of gaze by observing that the diplopia is maximal in a particular direction of gaze => then cover the 'presumed non-paretic' eye when the patient is gazing in the direction of weakness of the 'presumed-paretic' eye and insist that the patient pick up fixation with the 'presumed-paretic' eye => check to see how fast and how smoothly the patient fixates on your finger with the 'presumed-paretic' eye and estimate how much the 'presumed paretic' eye deviated to get into the position of fixation => then quickly uncover the 'presumed non-paretic' eye and allow the non-paretic eye to resume fixation => check how fast and how smoothly the non-paretic eye re-fixates on the target and estimate how much the non-paretic eye deviated to resume re-fixation
(* the test is based on Hering's law of equal innervation to yoked muscles - see appendix for further details)
- the test is deemed positive if the 'presumed-paretic' eye moves slowly to pick up fixation and the degree of primary deviation (the amount of movement required by the 'presumed-paretic' eye to pick up fixation) is less than the degree of secondary deviation (the degree of movement that the non-paretic eye had to deviate to resume fixation), which usually occurs faster and smoother and without any time-delay
(* the test can be non-diagnostic if the patient cannot take up fixation with the 'presumed paretic' eye, or if the patient maintains fixation with the 'presumed' paretic eye after uncovering the non-paretic eye, or if decreased visual acuity in the non-paretic eye interferes with fixation by the non-paretic eye => see the appendix for a description of how to perform the single-cover and cover-uncover tests - an alternative method of determing the degree of primary deviation and secondary deviation)
- if the test is positive => you have objective evidence that there is misalignment of eye movements in a particular direction of gaze and you have also identified the involved eye
(* the test is very sensitive and you can readily notice even minor deviations of the paretic eye as it moves to fixate on the target)
- if the test is negative => you have probably chosen the incorrect eye => repeat the test covering the opposite eye
(* if you cover the paretic eye => the non-paretic eye will not move as it continues to fixate on your finger, and when you uncover the paretic eye => it too will not move to fixate on your finger because the patient is still fixating on the visual target with the non-paretic eye)
- if the test still remains negative (and the patient's eyes do not deviate during the cover and uncover maneuvers), then you can reasonably conclude that the eyes are conjugately aligned and that there may be no objective evidence of diplopia in the tested direction of gaze
(* objective evidence of diplopia may still be detectable using specialized opthalmological equipment in a neuro-opthalmologist's office and these patients still require further opthalmological evaluation)
- the next question to answer if there is objective evidence of ocular misalignment in a particular direction of gaze => ? whether the ocular misalignment is due to a paretic EOM, or whether it is due to a restriction of the opposing EOM
- you can usually answer that question by performing duction testing and/or forced duction testing
- duction testing is performed by repeating the version testing process and getting the patient to look as far as possible in the direction of greatest diplopia (and presumed EOM weakness) => then cover the non-paretic eye and insist that the patient fixate on your finger with the paretic eye (as performed in the cover-uncover test)
- if the paretic eye moves further in that direction to take up fixation, then it implies that duction is superior to version (for the affected eye), and you can conclude that the cause of the weakness is neurogenic or neuromuscular
- if the paretic eye cannot exhibit a greater range of motion with duction testing than with version testing, the cause is likely to be restriction of the opposing EOM
- restriction of the opposing extra-ocular muscle can be further verified by forced duction testing
- forced duction testing is performed by placing a Q tip on the surface of the topically anethetized eyeball alongside the limbus (use proparocaine eyedrops first and then use a cocaine-soaked Q tip to further anethetize the conjunctival area alongside the limbus) => try to push the globe in the direction of the apparent weakness eg. if the patient cannot fully abduct the eye and the lateral rectus muscle appears weak => place the Q tip on the medial side of the eyeball and push the Q tip so as to rotate the eyeball laterally (or one can grasp the surface of the anethetized globe just alongside the limbus with forceps and rotate the globe by pulling rather than pushing - this may have to performed under general anesthesia in children or uncooperative patients)
- if the eyeball can be further displaced in the direction of the apparent weakness => a restrictive defect is unlikely and the likely cause of the diplopia is neuromuscular weakness
Example of forced duction testing in a patient with failure of eye abduction on version testing
- after the eye has been anesthetised by proparacaine => the conjunctivae of the medial eye is grasped just posterior to the limbus (at a point opposite the direction of limitation) with fine forceps => an attempt is made to rotate the eye laterally in the direction of limitation => if mechanical limitations are present (eg. medial rectus contracture), the eye will resists attempts to rotate in the direction of limitation
- after performing version and duction testing, you can also confirm that a specific eye has EOM weakness in a particular direction of gaze by performing an abbreviated red glass lens test
- place a red glass lens over the right eye and check for diplopia in the direction of action of the 'presumed' weak muscle by asking the patient to look at a bright penlight held ~14" in front of his face, which is then moved in the direction of action of the weak muscle => ask the patient how far the images are displaced and whether they are situated horizontally or obliquely alongside each other and which color image (red or white) is the most peripheral image eg. if the left lateral rectus muscle is weak => the images will be maximally displaced when looking to the extreme left side, the images will be situated horizontally alongside each other and the most peripheral image will be the white image (uncrossed diplopia); if the right medial rectus muscle is weak => the red image will be the most peripheral image (crossed diplopia)
- if the diplopia is worse when looking up or down and the images are vertically or obliquely seperated => probable weakness of one-or-more of the eight cyclovertical EOM's moving the eye vertically
- you may be able to determine which cyclovertical muscle is weak by using the cover-uncover and red glass tests in the direction of greatest diplopia (and presumably the direction of action of the 'presumed paretic' extra-ocular eye muscle)
- by plotting the degree of diplopia (degree of seperation of images) and determining whether the false image lies horizontally alongside (or obliquely alongside) the true image in all 9 directions of gaze, certain pattern-combinations can suggest a specific extraocular nerve deficit => see image-table below
- note that in a 6th nerve palsy => diplopia is greatest when
looking to the affected side (abduction)
- note that in a 3rd nerve palsy => diplopia is greatest when
looking up and to the opposite side (adduction)
- note that in a 4th nerve palsy => diplopia is greatest when
looking down and to the opposite side (adduction)
- the three-step test may also be useful in determining that a single cyclovertical eye muscle is weak eg. trochlear nerve palsy => unilateral superior oblique muscle weakness; however, the three step test may be unreliable or inconsistent if more than one cyclovertical muscle is weak eg. complete 3rd cranial nerve external opthalmoplegia
Parks-Bielchowsky three-step testing
- the Parks-Bielchowsky three-step test is used in patients with vertical diplopia (possibly caused by weakness of the eight EOM's involved in vertical movements of the eyes) to determine which specific cyclovertical eye muscle is weak
Step 1: Position the patient's head in the neutral position (beware of head tilt) => determine which eye is higher (elevated) with the patient looking straight ahead
- if the right eye is higher (hypertropic) => then the weak muscle is either a right eye depressor (r. superior oblique or r. inferior rectus) or a left eye elevator (l. superior rectus or l. inferior oblique)
- if the left eye is higher (hypertropic) => then the weak muscle is either a left eye depressor (l. superior oblique or left inferior rectus) or a right eye elevator (r. superior rectus or r. inferior oblique)
Step 2: Check the degree of hyperdeviation with the patient gazing to the left and then to the right
- if the right hypertropia increases on gazing to the left => then either the r. superior oblique or l. superior rectus is weak
- if the right hypertropia increases on gazing to the right => then either the l. inferior oblique or r. inferior rectus is weak
- if the left hypertropia increases on gazing to the left => then either the l. inferior rectus or r. inferior oblique is weak
- if the left hypertropia increases on gazing to the right => then either the l. superior oblique or r. superior rectus is weak
Step 3: Is the hyperdeviation greater on tilt of the head to the left or right (with the patient fixating on an object straight ahead in primary forward gaze)?
- if the deviation is greater on tilting the head to the left => then either the l. superior oblique or l. superior rectus (incyclotortors) or r. inferior oblique or r. inferior rectus (excyclotortors) are weak
- if the deviation is greater on tilting the head to the right => then either the r. superior oblique or r. superior rectus (incylclotortors) or the l. inferior oblique or l. inferior rectus (excylotortors) are weak
The only muscle affected in all three steps = The weak muscle
- if the superior oblique muscle is weak => either a localised muscle dysfunction or a 4th cranial nerve palsy
- if the superior rectus muscle is weak => either a localised muscle dysfunction or a superior division of the 3rd cranial nerve palsy (patient usually has associated ptosis)
- if the medial rectus, inferior rectus or inferior oblique muscles are weak => either a localized muscle dysfunction or a partial oculomotor nerve palsy
- if the eyes are not vertically misaligned, or if the three-step test is inconclusive with complex results that defy easy interpretation => ? 3rd nerve palsy, ? multiple EOM cranial nerve palsies, ? weakness of multiple EOM's
- if multiple EOM's are involved => the etiology is either a complete 3rd nerve palsy or multiple EOM cranial nerve involvement (cavernous sinus syndrome or posterior orbit syndrome or parasellar area pathology or skull base pathology or a secondary cranial nerve polyneuropathy - Miller-Fisher variant of Guillane-Barre syndrome, diptheria or neurotoxins [alcohol, lead, arsenic, carbon tetrachlodide, phenytoin, gold salts, isoniazid]) or EOM polymyopathy (myasthenia gravis, botulism) or intra-orbital pathology interfering with multiple EOM movements (thyroid orbitopathy)
- if the pattern of diplopia suggests a particular extraocular cranial nerve palsy, you can further determine the possible site of the lesion by using the following sub-analysis
- a 3rd nerve palsy presents with a history of horizontal and/or vertical diplopia, ptosis, or complaints of an enlarged pupil or difficulty in focusing; diplopia may be absent because ptosis effectively occludes the eye
- when the 3rd nerve palsy is complete, the eye may be deviated down and out; when the motility defect is more subtle, an exotropia on adduction, a hypotropia on elevation, and a hypertropia on depression occurs in the involved eye
- the affected (pupil-dilated) right eye is abducted and tilted downwards (under the unopposed influence of the 6th and 4th extraocular nerves) under the ptotic upper eyelid on forward gaze
- the major differential diagnosis in an adult who has an isolated 3rd nerve palsy are vasculopathic infarction, a compressive lesion (usually from an aneurysm), trauma, meningeal inflammation, tumor, or ophthalmoplegic migraine
- bilateral 3rd nerve palsies +/- bilateral ptosis, or ipsilateral 3rd nerve palsy + contra-lateral superior rectus palsy => oculomotor nucleus lesion in the mid-brain
(* the pupils may or may not be involved)
- complete/incomplete 3rd cranial nerve palsy + ipsilateral cerebellar-type ataxia => mid-brain (dorso-lateral) lesion affecting the brachium conjunctivum and the oculomotor nerve fasicles (Nothnangel's syndrome)
- complete/incomplete 3rd cranial nerve palsy + contralateral cerebellar type-ataxia + ipsilateral flapping tremor => mid-brain (paramedian) lesion affecting the red nucleus and the oculomotor nerve fasicles (Benedikt's syndrome)
- complete/incomplete 3rd cranial nerve palsy + bilateral ataxia + contralateral asynergia, dysmetria and dysdiadokinesia => midbrain lesion affecting the red nucleus, brachium conjunctivum and the oculomotor nerve fasicles (Claude's syndrome)
- complete/incomplete 3rd cranial nerve palsy + contralateral hemiplegia, including the lower face and tongue => midbrain (basal) lesion affecting the cerebral peduncle and the oculomotor nerve fasicles (Weber's syndrome)
(* the commonest causes of mid-brain pathology are vascular ischemia, vascular hemorrhages or tumors)
- 3rd cranial nerve palsy + 4th cranial nerve palsy, and/or 5th cranial nerve palsy (opthalmic division +/- maxillary division), and/or 6th cranial nerve palsy => cavernous sinus pathology or superior orbital fissure pathology or orbital apex pathology or base of skull pathology
(* Tolosa- Hunt syndrome is an idiopathic inflammatory condition involving the cranial nerves in the cavernous sinus, and it responds dramatically to steroids; however, it is a diagnosis of exclusion and a MRI +/- LP is required to first exclude tumors/aneurysms/infections causing a cavernous sinus syndrome)
- 3rd cranial nerve palsy + optic nerve visual loss +/- proptosis => posterior orbit pathology
- isolated superior division of 3rd cranial nerve palsy (causing only superior rectus weakness and ptosis) => intra-orbital or anterior cavernous sinus pathology affecting the superior division of the oculomotor nerve
- certain types of 3rd cranial nerve palsy defy localization - syphilis, sarcoidosis, Lyme disease, giant cell arteritis, tuberculosis, opthalmoplegic migraine
- an isolated 3rd cranial nerve palsy is most commonly due to lesions of the oculomotor nerve in the subarachnoid space
- pupil-involving 3rd cranial nerve palsy => cerebral artery aneursym until proved otherwise (emergent MRI angiography required - especially if headache or peri-orbital pain present)
- pupil-sparing 3rd cranial nerve palsy in a patient > 50 years is commonly due to hypertension or diabetes => expectant management is acceptable, because recovery usually occurs within 3 months => refer to a neurologist +/- early MRI of the brain (if the pupil becomes involved during the first week of followup, because it suggests an aneurysm)
- if a pupil-sparing 3rd nerve paresis does not resolve within the expected 3 month period, further workup is indicated, which includes a MRI scan, vasculitis workup, and, if no diagnosis can be made, a CSF examination
(* the commonest cause of a pupil-sparing 3rd nerve palsy is vascular infarction of the 3rd nerve in a diabetic patient - the infarction affects the core of the nerve and spares the pupillary fibres, which are located in the periphery of the nerve; other less common causes of a pupil-sparing 3rd nerve palsy include hypertension, atherosclerosis, lupus, giant cell arteritis, ipsilateral temporal lobe tumors, ipsilateral acute subdurals and migraine)
- pupil-sparing 3rd cranial nerve palsy in a patient < 50 years => emergent MRI of the brain is advisable prior to neurology referral to r/o structural disease
(* compression of the 3rd nerve by a cerebral artery aneurysm initially spares the pupil in 20% of cases => mydriasis may be delayed by one week)
- in adults below the vasculopathic age, all 3rd nerve palsies should be worked up with MRI, blood tests (sed rate, RPR, FTA, Lyme titer, glucose, ANA) to r/o vasculitis or infection, and CSF examination if no other cause is found
- if clinical testing suggests a possible 3rd nerve dysfunction => check for signs of abberrant regeneration of the nerve (upper eyelid retraction on adduction and depression of the eye, retraction of the globe on attempted vertical gaze, or pupillary constriction with adduction - pseudo-Argyll Robertson pupil)
- signs of abberant regeneration of the 3rd nerve + associated signs of 3rd nerve palsy implies subacute/chronic pathology eg. nerve compression by a slowly enlarging aneurysm or tumor, and does not occur secondary to sudden vascular infarction
- primary abberant regeneration refers to the findings above, but with no antecedent 3rd nerve palsy => suggests a slowly evolving compressive lesion with ongoing recovery to produce abberant regeneration of the nerve eg. internal carotid artery aneurysms in the cavernous sinus, intracavernous meningiomas or neurinomas
- a 4th nerve palsy presents with an isolated, vertical, diagonal, or incyclotorsional diplopia
- a 4th nerve palsy is the most common cause of vertical diplopia
- the diplopia is usually worse close up and down, as in reading, and is worse when looking to the side opposite the lesion
- in addition, the head may be turned down, with the chin depressed, the eyes up, and the face turned to the side opposite the paresis, to diminish the diplopia
- the signature motility dysfunction is a hyperdeviation that increases on opposite gaze and ipsilateral head tilt
A = involved (right) eye is elevated on forward gaze
B = extent of elevation is increased with adduction
C= extent of elevation is decreased with abduction
D = Elevation is increased with head tilting to the affected side
E = Elevation is decreased with head tilting in the opposite direction
- commonest etiological cause (after idiopathic) is blunt head trauma, which can produce bilateral 4th nerve palsies
(* however, the blunt head trauma may unmask a 4th cranial nerve palsy secondary to a basal intracranial tumor => always perform neuroimaging of the base of the skull to exclude an underlying tumor)
- other common causes include micro-vascular infarction secondary to diabetes or neoplasms, and skull basilar inflammation or infection
- less common causes include tumor that involves the midbrain or cerebellum, aneurysm, or herpes zoster ophthalmicus
- tumor is a more common cause in children and young adults, compared to older adults => therefore always order a MRI in pediatric patients with new-onset, isolated 6th nerve palsy => search for vasculitis if MRI negative => CSF exam if studies are negative
- in an elderly person, with or without a history of diabetes or hypertension, a sed rate to r/o giant cell arteritis, blood glucose, antinuclear antibodies, fluorescent treponemal antiboides, and a Lyme titer are indicated => followed with expectant improvement over a few months => MRI if no improvement occurs over a few months
- unilateral 4th cranial nerve palsy + 3rd, 5th, 6th cranial nerve palsies => cavernous sinus or superior orbital fissure or orbital apex pathology
- unilateral 4th cranial nerve palsy due to brain stem disease is often associated with Parinaud's syndrome (pinealoma, aqueductal stenosis, hydrocephalus) or a central Horner's syndrome
- the signature motility dysfunction is a failure of eye abduction
- note in (A) that the affected (right) eye is adducted at rest
- note in (B) that the affected (right) eye cannot abduct
- trauma, micro-vascular disease and basal intracranial neoplasms are the commonest causes
- in elderly patients, microvascular infarction secondary to diabetes is the most common cause of an isolated 6th nerve palsy
- tumor, trauma or an aneursym usually produces a non-isolated 6th nerve palsy
- tumor is a more common cause in children and young adults, compared to older adults => therefore always order a MRI in pediatric patients with new-onset, isolated 6th nerve palsy
- in an elderly person, with or without a history of diabetes or hypertension, a sed rate to r/o giant cell arteritis, blood glucose, antinuclear antibodies, fluorescent treponemal antiboides, and a Lyme titer are indicated => followed with expectant improvement over a few months => MRI if no improvement occurs over a few months
- bilateral 6th cranial nerve palsy => increased intracranial pressure until proved otherwise (can also be caused by basal meningitis, clivus lesions and posterior fossa lesions)
- 6th cranial nerve palsy + Horner' syndrome + 3rd cranial nerve palsy + 4th cranial nerve palsy => cavernous sinus syndrome
- 6th cranial nerve palsy + facial weakness +/- ipsilateral Horner's syndrome, ipsilateral face hypoalgesia, ipsilateral deafness +/- ipsilateral gaze palsy to the side of the lesion => pons (ventro-lateral) lesion (Foville syndrome)
- 6th cranial nerve palsy + 7th cranial nerve palsy +/- contralateral loss of touch and proprioception + internuclear opthalmoplegia with gaze palsy to the side of the 6th nerve palsy due to interruption of connecting fibres to the opposite third nerve nucleus => pons (paramedian) lesion
- 6th nerve cranial palsy + 7th nerve cranial palsy + contra-lateral hemiplegia => pons (basal) lesion (Millard-Gubler syndrome)
- 6th cranial nerve palsy + 5th cranial nerve palsy + 8th cranial nerve palsy => apex of petrous bone pathology (Gradenigo's syndrome)
- note that lesions of the abducens nucleus in the brainstem => often produce a conjugate gaze palsy to the ipsilateral side (and not always true abduction weakness)
- bilateral, multiple EOM palsies => extra-ocular muscle myopathy eg. myasthenia gravis, botulism, or cranial nerve polyneuropathy eg. Miller-Fisher variant of Guillane-Barre syndrome, or restrictive EOM disorder eg. thyroid orbitopathy, or central gaze palsy eg.brainstem stroke
- skew deviation is a vertical misalignment of the eyes due to brainstem disease, which disrupts the prenuclear inputs - suspected when:-
- the vertical diplopia is pure without any degree of tilting
- the hyperdeviation of the eye is present on primary forward gaze
- the hypertropia does not vary in different directions of gaze (comitant) or alternates when looking from one-side to the other-side
- the vertical misalignment is paroxysmal
- any associated limitation of vertical eye movements can be overcome by Bell's phenomenon (eyes roll up when the patient closes his eyes against resistance) or a vertical Doll's head maneuver
- other associated brain stem signs are present - other cranial nerve palsies, crossed hemiparesis, spinothalamic signs, unilateral internuclear opthalmoplegia with weakness of ipsilateral adduction and associated intorsion of the hypertropic eye
- bilateral, multiple EOM palsy +/- gait ataxia +/- confusion/confabulation +/- horizontal nystagmus => suggests Wernicke's disease
| Appendix |
Vergence = Voluntarily fixating the eyes on a single fixed point in space
Vergence testing = Testing eye movements by asking the patient to follow the movement of a single fixed object in space - both eyes must be open as the patient fixates on the target object
Duction testing = Testing the movement of only one eye for range of motion
Esotropia = Deviation of the eye inwards, towards the nose
Exotropia = Deviation of the eye outwards, away from the nose
Strabismus = Heterotropia = Misalignment of the eyes
Hypertropia = Misalignment of the eyes so that one eye appears higher than the other
Cyclotorsion = An extra-ocular eye movement that causes rotation of the globe around the visual axis
Incyclotorsion = The 12 o'clock position of the cornea rotates medially
Excyclotorsion = The 12 o'clock position of the cornea rotates laterally
Actions of extra-ocular muscles
Medial rectus => adduction
Lateral rectus => abduction
Superior rectus => elevation (greatest in abduction) and intorsion
Inferior rectus => depression (greatest in abduction) and extorsion
Superior oblique => intorsion and depression (greatest in adduction)
Inferior oblique => extorsion and elevation (greatest in adduction)
Hering's law of equal innervation of yoked extra-ocular muscles
When a patient looks in a particular direction of gaze, the extra-ocular muscles moving the two eyes are yoked together so that the two eyes move equally in the direction of conjugate gaze eg. when looking horizontally to the right, the right lateral rectus muscle and the left medial rectus receive an equal degree of innervation, so that they move the left and right eye equally in the direction of right lateral gaze - the muscle pairs are yoked together in conjugate gaze.
If one of the pair of yoked muscles is weak, then an equal degree of
innervation will move the paretic eye less in that direction of gaze =>
the eye will appear to be deviated compared to the normal eye, because
it does not move as far as the normal eye in its direction of weakness
eg. if the right lateral rectus muscle is weak => the right eye will not
move as far towards the right as the left eye and it will seem to lag behind
the left eye and be deviated medially (the degree of esotropic deviation
= degree of primary deviation). If you then prevent fixation by
the left non-paretic eye (by covering the left eye during version testing),
and ask the patient to keep looking at the target finger => a greater degree
of innervation will be required to move the right paretic eye in its direction
of weakness so as to enable the patient to visually fixate on the target
finger. While the patient is fixating with the paretic eye (which requires
an additional amount of innervation) => the same amount of additional innervation
is going to the medial rectus muscle of the non-paretic left eye => that
additional amount of innervation will cause a greater degree of
movement of the left eye (because it is not weak) - which is why
the degree of
secondary deviation of the non-paretic eye is always
greater than the degree of primary deviation of the paretic eye
The best test to demonstrate the presence, and degree, of a primary
and secondary deviation is the single-cover and cover-uncover tests
(in both tests, one eye is covered at a time; however, in the single-cover
test, one eye is covered and the other eye is observed; in the cover-uncover
test, one eye is covered, and the behaviour of that eye is observed when
the cover is removed)
A = Initially, with both eyes viewing, the left (unaffected) eye is viewing the target, and the right (affected) eye is esotropic
B = When the right eye is covered, no movement of the left (uncovered) eye is observed
C = Nor is movement of the right eye observed when the cover is removed
D = When the left (unaffected) eye is covered, the right (affected) eye moves outwards to take up fixation
E and F = When the cover is removed, either (E) the left eye moves to again take up fixation, or (F) the paretic right eye continues to fixate
Note that the deviation of the normal eye under cover (secondary deviation = a) is greater than the paretic eye under cover (primary deviation = b)
Differential
diagnosis of painful opthalmoplegia
| Diagnostic category | Diagnostic possibilities |
| Orbital causes | |
| Infectious - orbital cellulitis | Bacterial
|
| Inflammatory (non-infectious) |
|
| Vascular |
|
| Neoplasm at orbital apex |
|
| Non-orbital causes | |
| Neoplastic - primary intracranial |
|
| Neoplastic - cranial |
|
| Neoplastic - secondary metastatic |
|
| Infectious |
|
| Inflammatory |
|
| Vascular |
|
| Traumatic |
|
| Other |
|
Likely
causes of extraocular nerve pathology
| Cause | Nerve III | Nerve IV | Nerve VI |
| Unknown | 23% | 29% | 26% |
| Vasculopathy | 20% | 21% | 17% |
| Aneurysm | 19% | 1% | 3% |
| Trauma | 14% | 32% | 14% |
| Neoplasm | 12% | 7% | 20% |
| Syphilis | 2% | < 1% | 1% |
| Multiple sclerosis | - | - | 6% |
| Other | 10% | 10% | 13% |
Likely
cranial nerve involvement based on site of the pathology
| Cranial nerve | Cavernous sinus | Superior orbital fissure | Orbital apex |
| II | - | - | + |
| III | + | + | + |
| IV | + | + | + |
| V1 | + | + | + |
| V2 | + | - | - |
| V3 | - | - | - |
Disclaimer:
My EM guidemaps reflect my personal approach to problem-solving/managing
clinical cases in an ED setting and they should not be regarded as the
standard of care. They merely represent the personal opinions of the author
and they should only be used in clinical practice if the reader-user has
substantial reason to believe that the clinical advice contained in the
guidemaps is valid and accurate. The guidemaps are not meant to be "authoritative"
and the reader-user should consult standard medical textbooks and expert
opinion articles/guidelines for more authoritative advice. The reader-user
should particularly confirm all drug doses, their indications and contra-indications,
prior to their use.