Diplopia

Medicine > Neurosciences

Differential Diagnosis Schema 🧠

Neurological Causes

Cranial nerve palsies: Most common, particularly CN III, IV, and VI. CN III palsy presents with ptosis, ‘down and out’ eye, and mydriasis.
Multiple sclerosis: Internuclear ophthalmoplegia, often with other neurological symptoms
Myasthenia gravis: Fatigable weakness, fluctuating diplopia, ptosis
Brainstem lesions: Associated with other neurological signs (e.g., hemiparesis)
Intracranial mass: Progressive symptoms, often with other signs of raised intracranial pressure

Ophthalmic Causes

Refractive errors: Astigmatism or uncorrected refractive error, particularly when looking at distant objects
Cataracts: Causes monocular diplopia, more pronounced in low light conditions
Corneal abnormalities: Keratoconus or scarring, leading to distortion of images
Retinal disorders: Macular degeneration or retinal detachment leading to distorted vision

Systemic Causes

Thyroid eye disease: Often with proptosis, lid lag, and restricted eye movements
Diabetes mellitus: Can cause microvascular cranial nerve palsies, typically affecting CN III, IV, or VI
Hypertension: Can cause cranial nerve palsies via microvascular ischemia
Stroke: Diplopia often occurs with other neurological deficits such as hemiplegia or dysphagia
Giant cell arteritis: Sudden onset in elderly, associated with headache and jaw claudication, can cause blindness if untreated

Trauma-Related Causes

Orbital fracture: Restriction of eye movement, particularly in upward gaze, with enophthalmos
Head injury: Can cause cranial nerve palsies or orbital damage, often with other neurological signs
Ocular surgery: Post-operative complications such as scarring or muscle damage leading to diplopia

Key Points in History 🥼

Onset and Duration

Acute onset: Suggests vascular cause (stroke, GCA) or trauma
Chronic/progressive: More likely to be due to a mass lesion, thyroid eye disease, or degenerative neurological condition
Intermittent: Consider myasthenia gravis or MS, especially if fatigable

Character of Diplopia

Monocular vs binocular: Monocular suggests a problem in the eye itself (e.g., cataract), binocular suggests an alignment issue or cranial nerve palsy
Horizontal vs vertical diplopia: Horizontal diplopia often involves CN VI (lateral rectus), vertical diplopia often involves CN IV (superior oblique)
Variation with gaze direction: May indicate specific cranial nerve involvement or restrictive myopathy

Associated Symptoms

Headache: Consider GCA, raised ICP, or migraine
Eyelid drooping: Suggests CN III palsy or myasthenia gravis
Pain: Orbital pain with eye movement may suggest optic neuritis or orbital cellulitis
Systemic symptoms: Fever, weight loss, fatigue may suggest an underlying systemic condition (e.g., GCA, malignancy)

Background

Past medical history: Key conditions include diabetes, hypertension, thyroid disease, and previous neurological conditions
Medication history: Some medications can cause diplopia (e.g., phenytoin, alcohol)
Family history: Important for hereditary conditions like multiple sclerosis or myasthenia gravis
Social history: Occupation, driving, and activities impacted by diplopia

Possible Investigations 🌡️

Blood Tests

Full blood count: To check for anemia or infection
ESR and CRP: Raised in GCA or other inflammatory conditions
Thyroid function tests: To assess for thyroid eye disease
Acetylcholine receptor antibodies: For myasthenia gravis

Imaging

MRI brain and orbits: To identify structural lesions, demyelination, or inflammation
CT scan: Useful in acute settings, particularly in trauma or to exclude hemorrhage
Orbital ultrasound: Can assess for orbital masses or thyroid eye disease
Carotid Doppler: Consider in GCA or to assess for carotid artery dissection

Specialist Tests

Tensilon test: For suspected myasthenia gravis
Visual field testing: To identify defects related to optic neuropathies or stroke
Electromyography (EMG): To assess for neuromuscular junction disorders like myasthenia gravis
Lumbar puncture: If inflammatory or infectious CNS disease is suspected

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