Certain ocular signs could signal mortality

Leonid Skorin Jr.

You may find yourself in a situation where a patient is experiencing a neurologic sign or symptom that could signal mortality, or you may be called upon to follow up such a patient with a thorough eye exam and appropriate testing. Conditions requiring this swift, specialized attention include amaurosis fugax, diplopia and disc edema.

Amaurosis fugax: transient monocular vision loss

Patients will describe an episode of amaurosis fugax as a curtain of darkness descending over one of their eyes. This painless vision loss will last from just a few minutes to 30 minutes. As the vision recovers, the curtain of darkness will rise or resolve like a clearing fog.

Amaurosis fugax is a form of transient monocular vision loss caused specifically by retinal ischemia and often found to have ipsilateral retinal microemboli from an ipsilateral atheromatous carotid artery obstruction. The condition can be considered a form of transient ischemic attack as seen in patients who may also experience temporary hemiparesis, hemisensory deficit, speech impediments, vertigo and ataxia.

All of these signs and symptoms are warning of a possible impending stroke. Stroke is one of the major causes of mortality and major morbidity worldwide. To emphasize the critical nature of stroke diagnosis and treatment, it has been equated with myocardial infarction (heart attack), and doctors and patients should now consider it a “brain attack,” remembering that “time is brain.”

Brain attack symptoms include sudden weakness or numbness usually on one side of the body. The patient may experience difficulty speaking, have difficulty walking or develop a sudden severe headache. Any patient who has experienced brain attack symptoms needs a quick diagnosis, and treatment.

Narrow treatment window

A 3-hour treatment window exists, with very strict guidelines for patients who have had an acute ischemic stroke. Intravenous tissue plasminogen activator (tPA) is the only Food and Drug Administration-approved treatment for such an ischemic attack. It must be administered by a stroke expert, usually a neurologist. This treatment increases the chance of a good recovery by 30% to 50%. The most serious complication of this type of treatment is a symptomatic intracranial hemorrhage. Of course, hemorrhagic strokes should not be treated with tPA.

One non-FDA approved treatment is intra-arterial thrombolysis with urokinase, which is administered by an interventional neuroradiologist. This therapy actually increases the treatment window to up to 6 hours. The symptomatic intracranial hemorrhage rate is greater with this treatment as compared to tPA. Other acute treatments include aspirin therapy (160 to 325 mg/day), fast-acting antiplatelet agents administered intravenously and anticoagulation therapy.

All patients who have had amaurosis fugax need a thorough eye exam with emphasis on the fundus evaluation. Care should be taken to identify any cholesterol or calcium microemboli. The optometrist should auscultate for any bruits. If a bruits is heard, do not palpate the arteries to avoid loosening an embolus. Otherwise, gently palpate the carotid arteries to assess for symmetry of strength and patency. Ophthalmodynamometry can be done in the office to compare ocular blood flow between both eyes.

A referral to the patient’s internist, neurologist or vascular surgeon is also essential for further carotid and cardiac workup. This additional workup may include testing for temporal arteritis (sedimentation rate, C-reactive protein), because it may first present as amaurosis fugax; carotid duplex ultrasonography, echocardiography to evaluate the heart; and, possibly, conventional carotid angiography if carotid artery endarterectomy surgery is being considered.

In patients who have experienced a recent brain attack, the optometrist should call 911 or the local “stroke number” if he or she is near a major medical center. This will activate the stroke team who will confirm the diagnosis, stabilize the patient, perform any imaging that is indicated and administer treatment (tPA or thrombolysis).

Diplopia: misalignment due to cranial nerve insult

The cranial nerves, which control the extraocular muscles, are vulnerable to damage from potentially fatal brain aneurysms, stroke, brain tumors, trauma, infection, myasthenia gravis and temporal arteritis. Brain aneurysms in particular can rupture, killing the patient within hours of the onset of diplopia.

Diplopia occurs when the eyes are misaligned secondary to insult of the third (oculomotor), fourth (trochlear) or sixth (abducens) cranial nerve. Other causes of diplopia include disease of the orbit, damage of the extraocular muscles or neuromuscular junction disease.

Having the patient explain what he or she means by “seeing double” and having him or her provide some basic details will help the optometrist correctly differentiate the diplopia. Ask if the diplopia is present when only one eye is open; ask if the diplopia is horizontal, vertical or on an angle; ask if the diplopia worsens in a particular direction of gaze; and, finally, ask if the diplopia is greater at distance or at near.

Diagnostic testing

Testing ductions, versions, saccades, cover-uncover testing, evaluating for proptosis and resistance to retropulsion, pupil evaluation and looking for any accompanying eyelid ptosis helps further localize the diagnosis. The Parks-Bielschowsky three-step test will help localize any weak muscle, especially if a vertical component exists.

Optic disc atrophy: This patient has nonarteritic ischemic optic neuropathy. Image: Skorin L

For patients younger than 50 who have a sixth or fourth nerve palsy, the optometrist should order an MRI of the brain following the course of the respective cranial nerve. Blood tests for diabetes and autoimmune disease should also be done. For patients older than 50 years, a workup for temporal arteritis should be performed.

For an isolated third nerve palsy with pupil involvement, the optometrist must rule out compression from an enlarging aneurysm at the junction of the carotid and posterior communicating arteries, which is a true neuro-ophthalmic emergency. The optometrist must order an MRI of the brain, MR angiography and, if necessary, conventional angiography in these cases.

If the pupil is spared in a patient of vasculopathic age, the patient should be monitored frequently for 1 week in case the pupil becomes involved later. A vasculitis workup including blood tests for temporal arteritis should be done. If the pupil-sparing third nerve palsy does not resolve on its own by 3 months, then an MRI of the brain should be obtained.

The neuromuscular junction disease of myasthenia is a relatively common cause of diplopia or ptosis in adults of all ages. Most patients with myasthenia say that their diplopia varies from day to day and is often worst at the end of the day. In generalized cases, patients may experience weakness of the extremities, dysarthria, dysphagia and breathing problems. At least half of the patients who start off with localized ocular myasthenia gravis will progress to the more dangerous generalized state.

Workup for suspected myasthenia

A workup of a patient who is suspected of having myasthenia includes measuring any extraocular muscle deviation or eyelid ptosis and identifying variability. The ice test and sleep test can be done in any optometric office. The edrophonium (Tensilon) test should only be done if appropriate rescue equipment and medications are readily available. Edrophonium can worsen the disease acutely and throw the patient into an immediate myasthenic crisis.

Because thymic tumors can occur in up to 10% of patients with myasthenia, a chest CT should be obtained. There is an overlap of myasthenia with thyroid disease. A thyroid evaluation needs to be done on all suspected cases. In addition to ordering a thyroid-stimulating hormone test and free T3 and T4 levels, acetylcholine receptor antibody testing should also be done. Special neuroelectrophysiologic testing, such as single fiber EMG, can further help diagnose the condition.

A simple way to differentiate between thyroid and myasthenia is to remember that myasthenia is painless, often presents with ptosis and has variable diplopia while thyroid disease exhibits proptosis and eyelid retraction with eye ache.

Disc edema common in temporal arteritis

A pallid “chalky white” swollen optic disc is a common finding in patients with arteritic ischemic optic neuropathy (temporal arteritis). This is a true neuro-ophthalmic emergency, and the clinician does not have the luxury of time when working with this patient. Permanent bilateral blindness is an all-too-common occurrence with temporal arteritis. In addition, patients with this disease have mortality rates of up to 20% if untreated.

Temporal arteritis is a chronic systemic disorder characterized by vasculitis affecting large and medium-sized vessels chiefly involving the head and neck. Constitutional symptoms include headache, scalp tenderness, jaw or tongue claudication, fever, chills, anorexia, weight loss, myalgias and arthralgias. In addition to the vision loss that can occur from the ischemic optic neuropathy, vision loss can occur from central or branch retinal artery occlusion, amaurosis fugax or cortical infarction.

Diagnostic steps

A typical evaluation for temporal arteritis includes emergent laboratory tests: erythrocyte sedimentation rate, C-reactive protein and complete blood count with platelets. If these values are all elevated in the presence of a high clinical suspicion for the disease, treatment with systemic corticosteroids must be initiated. A temporal artery biopsy provides a definitive tissue confirmation for the disease.

A negative clinical history with normal laboratory tests points the way to nonarteritic ischemic optic neuropathy (NAION). This is an ischemic process that affects the short posterior ciliary arteries at the anterior aspect of the optic nerve head. It is also the second most common optic neuropathy typically seen in patients older than 50 years. Patients with NAION often have underlying arteriosclerotic disease and may have undiagnosed hypertension, diabetes or hyperlipidemia. They need to be worked up by their family physician or internist for these conditions.

Recently, men who take one of the erectile dysfunction medications and have hypertension or a history of myocardial infarction have been found to have an increased risk of developing NAION.

Evaluating patients with papilledema

Papilledema is optic disc swelling and elevation secondary to increased intracranial pressure. While patients with papilledema frequently experience headache and minimal loss of central acuity, entities that cause this condition may lead to permanent visual loss if untreated.

Space-occupying intracranial lesions and venous sinus thrombosis must be excluded first. Pseudotumor cerebri may be diagnosed in patients of appropriate age and characteristics only when other entities have reasonably been excluded by neuroimaging and lumbar puncture. Other less common causes of papilledema include intracranial hemorrhage (subarachnoid, intra-parenchymal, subdural), hydrocephalus, meningitis, spinal cord tumor, Guillain-Barré syndrome and dural arteriovenous malformation.

Patients with malignant hypertension may experience bilateral optic disc swelling that mimics papilledema. Measuring the blood pressure in every patient with papilledema is a simple yet powerful clinical test that can be done in every optometric office.

For more information:

• Leonid Skorin Jr., OD, DO, FAAO, FAOCO, practices in Albert Lea, Minn., and writes and lectures on ocular disease and neuro-ophthalmic disorders. He underwent fellowship training in neuro-ophthalmology. He may be contacted at the Albert Lea Eye Clinic, Mayo Health System, 1206 W. Front St., Albert Lea, MN 56007; (507) 373-8214; fax: (507) 373-2819; e-mail: skorin.leonid@mayo.edu.