Diplopia – A Common Complaint in Neurology Practice

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hypertension diplopia

Diplopia is an all too often presented complaint in neurology clinical practice. Usually its source lies within medication or medical conditions that influence vision.

First step to diagnosis is identifying whether diplopia is binocular or monocular; this helps identify its source and set priorities for assessment. Next, examiners must note the direction of gaze-dependent diplopia (eg, vertical vs horizontal). And lastly, ocular motility testing must also take place.

Causes

Diplopia can be challenging to diagnose in the clinic and often requires prompt investigation. An ophthalmologist must first ascertain if the diplopia is monocular or binocular before considering possible causes; one easy way of testing this would be asking patients to cover one eye at a time and observe if their diplopia resolves; otherwise it would indicate binocularity which must be evaluated for potential orbital pathologies or neuromuscular aetiologies.

The Veteran presented to our clinic with complaints of right monocular diplopia and headache, along with prior service-connected diabetes and hypertension. He had corrected visual acuity of 20/20 in his right eye and 20/400 in the left, without improvement on pinhole, color plates or Amsler grid testing. His pupils were equal and reactive to light with no signs of an afferent pupillary defect; and denied weakness, loss of reflexes or ataxia. An examiner performed an ocular motility evaluation by placing his finger in the center of his field of vision and moving it in various directions – upward, downward, diagonally to either side, inward toward nose (convergence) etc. There was mild paresis of ocular movement with right eye showing slight deviation on all tests performed.

Isolated single cranial nerve palsies with normal pupillary light responses often resolve spontaneously. Patients displaying red flag symptoms, such as progressive deficit or failure to recover, should be further investigated with an MRI scan of orbital and cranial nerves; CT may be used if necessary or unavailable.

Diplopia is a common symptom in brain diseases and disorders, often appearing due to intraocular disease; however, it may also occur with lesions of the cerebellum, frontal eye fields, Brodmann’s area 19 or midbrain stroke with subsequent oculomotor neoplasms or compression of macular nerve fibers; monocular diplopia may also arise – although less frequently seen – but should still be promptly evaluated for cerebral causes if observed; one Veteran in particular was found with right midbrain ischemic stroke with monocular diplopia and right midbrain ischemic stroke as its source.

Diagnosis

Diplopia is a perceptual condition in which two distinct images of an object are perceived by the brain as separate objects, due to a malfunction in combining data from each eye into a single image. Diplopia may affect either one eye, both eyes, or both eyes at once and is classified by being horizontal vs vertical (the direction of gaze). When diagnosing diplopia, a detailed history should be obtained from the patient, including any potential trauma (ie: orbital fracture, head trauma or cranial nerve palsies) that might have contributed. Furthermore, whether manifest diplopia (tropia) only occurs with both eyes open (manifest diplopia, tropia) or also occurs when one eye is closed (latent diplopia, esotropia).

At any stage of suspected intracranial hypertension, visual field and optic fundus exams should be performed on patients to distinguish between sixth nerve palsy and normal neurological strabismus. If present, abducting saccade velocities will be slower compared with when functioning normally; the examiner should then ask the patient to cover his or her eye so as to observe for any refixation movements that would indicate correction of manifest esotropia or tropia; otherwise this would indicate latent sixth nerve palsy being present and should observe for it as this would indicate sixth nerve palsy being present and diagnose accordingly.

Examiners can also utilize a cover test to ascertain whether strabismus exists when both eyes are open, or only when one eye is covered (latent esotropia or esotropia). Patients should fixate on an object with both eyes; after covering one, observe its movements to see if either one re-fixates itself; if so, this indicates either lateral rectus muscle palsy or neurological strabismus is likely the source of diplopia and should be referred for further evaluation.

Presumptive diagnosis of microvascular disease should be made for any patients presenting with unilateral, isolated sixth nerve palsy who also show evidence of high blood pressure or diabetes mellitus. Such individuals should be closely monitored for symptoms while imaging studies using MRI may also be considered.

Treatment

Diplopia typically resolves once its source has been diagnosed and treated; diplopia not related to any medical condition typically improves with time or treatment (for instance correcting myopia or nearsightedness that caused it).

As part of a patient assessment, it’s crucial to identify when their diplopia began. Acute diplopia should be more alarming; gradual or insidious-onset diplopia often comes on gradually and shouldn’t cause as much alarm.

Cleft palsies that affect only pupils sparing cranial nerves should likely resolve spontaneously; however, any red flag findings on neurological examination or imaging warrant further evaluation to identify possible aetiologies for them.

Neuro-ophthalmologic examination of the affected eye is usually undertaken first, before moving on to conduct a comprehensive neurologic exam that includes all areas of the head and neck (palpation of jugular vein in neck for potential sphenoidal tumor; inspection of shins for pretibial myxedema; examination of muscles that control movement of neck and head; palpation of jugular vein for palpation for possible sphenoidal tumor; palpation of jugular vein in neck for possible sphenoidal tumor; inspection of pretibial myxedema; examination of muscles controlling movement). Diplopia can result from compression of any one or more cranial nerves so it’s important that all cranial nerves be tested (eg, examiner should move head between extremes of right/left gaze while simultaneously diagonally on either side and then test for parsing, adduction, infraduction deficits etc).

As per its results, lumbar puncture with cerebrospinal fluid (CSF) analysis may be performed if not contraindicated. An elevated opening pressure in the transverse sinus combined with normal CSF composition suggest idiopathic intracranial hypertension which may be confirmed via magnetic resonance venography imaging of the brain.

Clients experiencing episodic diplopia should undergo neurological testing, including for myasthenia gravis or multiple sclerosis. Patients who have a history of Graves disease should also be subjected to thyroid tests that involve measuring serum thyroxine levels and TSH. If these investigations are negative, further evaluation of diplopia may not be necessary. If symptoms do not improve over time, surgery may be considered. Optic nerve sheath fenestration (ONSF), a minimally invasive procedure performed outpatient, often leads to excellent short-term results; best corrected logMAR visual acuities often match or surpass preoperative values in many instances.

Prevention

Diplopia is a common condition found in general practice and may be related to orbital pathology, neuromuscular conditions or neurological disease processes. Knowledge of differential diagnoses is vital to ensure this condition is quickly recognized and investigated; many cases can be managed through simple examination and investigation. John Murtagh’s seven masquerades can serve as a useful framework to address diplopia by reminding clinicians about common issues often missed but which can be easily diagnosed through careful history and exam. A 42-year-old female presented with gradually worsening headache, nausea and vomiting and rightward gaze deviation that resolved with antihypertensives; further investigations were referred to.

About the Author:
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Alexander Suprun

Alex started his first web marketing campaign in 1997 and continues harvesting this fruitful field today. He helped many startups and well-established companies to grow to the next level by applying innovative inbound marketing strategies. For the past 26 years, Alex has served over a hundred clients worldwide in all aspects of digital marketing and communications. Additionally, Alex is an expert researcher in healthcare, vision, macular degeneration, natural therapy, and microcurrent devices. His passion lies in developing medical devices to combat various ailments, showcasing his commitment to innovation in healthcare.

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