Diplopia Flashcards
Discuss the difference between mono-ocular and binocular diplopia
Monocular diplopia is double vision that persists when one eye is closed – it is due to an ophthalmologist condition related to light distortion
Binocular diplopia is not present with one eye closed and is the result of a misalignment in the visual axis and has a range of cuases. Can be organised from progression from the optic nerve to the brainstem
- oculmotor dysfunction
- cranial nerve dysfucntion
- intranuclear or supra nuclear lesions in the brain stem or above
- restrictive orbitopathy (myositis, trauma, infection, craniofacial masses)
Secondary causes of binocular diplopia account for 36% of cases of binocular dipolar and include from most frequent to least
- stroke
- MS
- Brain tumors
- cerebral aneurysms
Discuss orbitopathies
Orbitopathies cause inflammation and expansion of retro-orbtial soft tissue Characteristic signs and symptoms without other neurology
Often only affecting a single extraocular muscle orbital myositis can be caused by most steroid resoponsive conditions syhc as wegeners, GCA, SLE, dermatomyositis, sarcoidosis can cause restrictive orbitopathies
Graves orbitoapthy is the most common cause of ocular myopathy in older adults
Discuss palsys cranial nerves involved in oculomotor function
CN 6 is the most commonly affected follwed by 3 and 4
An isolated simple mononeuropathy in CN 3,4,6 may be from a demyelinating process (MS), HTN or diabetic vasculopathy or compression
CN 3 is usually affected by HTN and diabetic complication. Aneuryms in the posterior communicating , basilar, superior cerebella, posterior cerebral and cavernous internal carotid arteries are a close second
Cn 4 Usually affected by trauma from abutting the tentorium
CN 6 due to its lenght is the most commonly affected by tumors, elevated ICP and micro vascular ischemia
Discuss causes that affect cranial nerves 3,4,6 similtaneously
Cavernous sinus infection, mass or vasculitis may affect all three cranial nerves however 6 is affect first as transverses the sinus instead of the walls like the other two. Causes include -carotid cavernous fistula -inflammatory vasculitiides such as GCA -Tolosa hunt syndrome -tumor or infiltration
More diffuse process involving the brainstem or CN 3,4,6 include
- infections
- – basillar menigitis
- autoimmune conditions
- –miller fisher, GB, wernickes encpeh
- –Myasthenia gravis
- neurotox
- – snake and tick paralysis
- metabolic
Discuss pivotal points in history to establish diagnosis
1: Timing and onset
- Truly sudden onset suggest an ischemic cause, cerebrovascular or micro vascular especially if intensity and degree of diplopia was maximal at onset
- fluctuation in symptoms may be due to TIA and may precede a stroke but more generally implies neuromusuclar disease
2: Direction and oreintation
- direction of gaze that elicit or wrosen the diplopia and the genreial orientation of the that diplopia should be determined (horizontal, vertical, torsional)
3: presence of pain
- The presence of pain suggest inflammatory or invective process and narrows DDX significantly
4: presence of other symptoms
Discuss symptoms and signs of mechanical orbitopathy
SYMPTOMS
A structural restriction of motion of a single eye
Typically gradual in onset
May cause diplopia in a single or multiple directions of gaze depending on the type and extent of msucular involvement
Patient may have a sensation of mass effect, discomfort or pain in the culprit eye
If due to an infection may be a history of fever
If diplopia is worse in the morning this is a symptom of Graves myopathy
SIGNS
- propotosis
- periorbital swelling
- oedema
- conjunctival or scleral hyperema
- palpebral swelling involving a single eye
Ocular myositis can be distinguished from a neurogenic palsy in that it abruptly restricts eye movement away from the muscle whereas a CN palsy smoothly and progressively impaired movement toward the weakened muscle.
Stigmata of Graves
- lid lag
- diffuse conjuncgival oedema
- vasculr injection
- typically affect the inferior and medial recti muscles first
Discuss symptoms of CN palsy
SYMPTOMS
- CN 3 reports diplopia in all fields except in lateral gaze
- CN 4 results in rotationla double vision making descending stairs, reading and watching TV in bed difficult.
- Diplopia worse on lateral gaze suggest CN 6
CN palsy asscoaited with orbital discomfort with sudden onset in a patient with chronic diabetes or HTN strongly suggest microvascular ischaemia is the cause.
-Caveat being that headache often preent with aneurysmal compression of CN 3
The diploia from a problem involving the cavernous sinus or orbital apex unlike a mononeuroapthy may manifest as a combination of the gaze abnormalities noted above. As CN5 passes the sinus ipsilateral periorbital facial numbness od dysthesia may be present
Discuss signs of CN palsies
SIGNS
CN3 - innervates the levator palpebrae superiors muscles which lifer the upper eyelid and provides parasympathetic innervation to two occular muscles the ciliary and constrictor pupillae muscles which constrict the pupil
-presents with diplopia in all direction of gaze except lateral and an eye that is deviated down and out with a dilated pupil and ptosis
-ischaemic cause of palsy often spares the pupil wheras compressive causes do not
CN 4- extorsion on downward gase - SO 4 - rotational nystgamus worse on downward gaze
CN 6 lateral gaze palsy - horizontal diplopia on gaze toward the affected side.
Ipsilateral palsies of CN 3,4 and 6 from an orbital apex or cavernous sinus process will tupically presnet with additional finding called orbital apex syndrome
- exopthalmos
- chemosis
- injection
Discuss symptoms of neuro-axial process involving the brainstem and related cranial nerves.
Focal brainstem lesions e.g MS may result in isolated diplopia.
However localised brainstem lesions such as those from mass effect or ischaemia typically also result in so-called neighbourhood symptoms and sign from anatomically contiguous involvement
Additional symptoms of nausea, vertigo, or slurred speech are concerning for an impengin basilar artery occlusion.
Diplopia from a more diffuse neurological syndrome that happens to involve the brainstem and cranial nerves is usually gradual in onset and manifest with various other discordant symptoms
Gradual onset with associated slurred speech and problems swallowing suggest botulism.
Discuss symtpoms of neuromuscular disorders
Diplopia that is variably triggered in multiple directions and without a distinct structural or neuropathic cause evident implies a neuromuscular cause such as myasthenia gravis.
Diplopia will generally fluctuate over time and in MG worsens with fatigue and improves with rest
Discuss ancillary testing
In patients with suspected or evident mechanical orbitopathy a MRI scan of the orbits with gaolinium can allow and assessment for enlargement or enhancement in extra-occular muscles and orbital structures.
MRI also imaging of choice for process in the cavernous sinus or orbital apex.
For isolated neuroapthy in CN4-6 optimal study is MRI with gadolinium
Aneruysmal cause CTA or MRA
IF MG - bedside test is the ice test
- an ice filled glove or bag is applied to the patients closed eye or eyes and held there for about 5 minutes and withdrawn.
- any improvement in ptosis or diplopia is noted
- cold temperature mitigate the effect of myasthenia related acetylcholine receptor blockade by decreasing cholinesterase activity and promiting the efficacy of ach at the endplate.
Discuss approach to diagnosis of diplopia
1) is the diplopia mono-ocular
2) is the diplopia due to a restrictive mechanical orbitopathy If due to a single eye consider: -inflammatory -traumatic -neoplastic -infectious If due to restriction in both eyes consider -Graves
3) is the diplopia due to a palsy of the oculomotor CN in a single eye
- Palsy in CN3,4,6
- compression vs ischaemia
- apex syndrome (cavernous sinus thromobosis)
4) is the diplopia due to neuroaxial process involvling the brainstem and related CN A) focal lesions MS B) more diffuse but still localised to the brain stem -tumor, -brainstem lacunar stroke - impending basilar artery thrombosis -vertebral artery dissection -ophthalmoplegic migraine C) more diffus neuo syndrome involving the brainstem or CN 34,6 -Basilar meningoencephalitis -foodborne botulism -miller fisher or GBS -Wernickes
5) is the diplopia due to NMD
- Myasthenia gravis
- tick paralysis
Discuss DDX via critical, emergent and urgent causes
CRITCAL
1) Basilar artery thrombosis
- impending thrombosis of the basilar artery with brainstem ischaemia
- distinguishing features : vertigo, dysarthrai, other CN involvement risk factors for stroke
2) Botulism
- Toxin inhibit ach at junction
- distinguishing features: Dysarthria, dysphagia, autonomic dysreflexia, pupillary dysfunction
3) basilar menngitis
- infection
- distinguishing features: headache, meningism, fever
4) Aneurysm
- enlarging aneurysm directly compressing CN
- CN 3 palsy with pupillary involvement
EMERGENT
1) Vertebral dissection
- disscetion causes vertebrobasilar ischaemia
- distinguishing features neck pain, risk factors for dissection
2) MG
- Autoantibodies against Ach
- distinguishing features - Fluctuating muscle wekaness, ptosis, and diplopia worsen with activity improve with rest
3) Wernickes
- thiamine dependant metabilic failure and tissue injury
- distinguishing features Nystagmus, ataxia, altered mental status, opthalmoplegia, alcoholism
4) orbital apex syndrome, cavernous sinus process
- inflammation, or infection in the orbital apeax or cavernous sinus directley affect CN
- distinguishing featuresCN 3,4,6 features, with exopathalmus, conjunctival injection and reto-oribtal pain
URGENT
1) brainstem tumor
- tumor involvement at the supranuclear level
- distinguishing features: skew deviation - vertical diplopia, internuclear opthalmoplegia
2) Miller Fisher Syndrome -
distinguishing features opthalmoplegia , ataxia, areflexia
3) Thyroid myopatju
- distinguishing features - proprotis, restriction of elevation and abudction of the eye, signs of graves
4) MS
