How to Spot a Neurologic Condition

The eye is a window to the brain and the rest of the central nervous system, enabling optometrists to identify telltale signs of neurologic conditions. Some of these disorders are sight-threatening and others can be life-threatening. The ability to recognize both the distinct and subtle symptoms and clinical signs of neuro-ophthalmic disease puts optometry in a position to positively affect a patient’s quality of life.

Prompt, appropriate examination and additional workup are critical in establishing an accurate diagnosis. Facilitating timely medical or surgical treatment, when necessary, is of utmost importance to ensure a positive ocular and systemic outcome. This article describes some of the “don’t miss” signs that every clinician should know about.

HISTORY AND BASELINE NEURO-OPHTHALMIC EXAMINATION

The neuro-ophthalmic examination always begins with a thorough history. This includes eliciting the patient’s chief complaint along with his or her specific medical history, ocular history, social history, review of systems, and list of present medications. The history should be followed by a comprehensive ophthalmic assessment of the afferent visual system.¹

Spatial resolution of vision (ie, BCVA) in each eye should be determined at distance and near (refraction, pinhole, or potential acuity images). Color vision via Ishihara pseudo-isochromatic plates or Hardy-Rand-Rittler plates, pupillary testing, visual field testing (confrontation field, static automated perimetry, Goldmann kinetic manual perimetry, or tangent screen), contrast sensitivity, brightness comparison, and photostress recovery testing should all be performed, along with a thorough examination of the fundus with direct and indirect ophthalmoscopy.

The neuro-ophthalmic examination should then concentrate on the efferent system. Disorders of this system usually include ocular misalignment or motility (comitant or incomitant) issues such as diplopia, head tilt, face turn, etc. The testing should be performed in a systematic way to efficiently identify a potential neuro-ophthalmic cause and potential life-threatening condition. Evaluation of the efferent system should include ductions and versions, saccades, pursuits, eyelid positioning and function, pupillary testing (symmetry, size, and reactivity), and nystagmus evaluation. Forced duction and doll’s head maneuver testing may be performed as needed. The optometrist may need to perform a quick exam to evaluate the patient’s mental status, motor reflexes, coordination/gait, and general sensory receptors.

TELLTALE SIGNS AND SYMPTOMS

The signs and symptoms discussed below, even though they may be intertwined at times, should make the eye care provider aware of a possible neurologic etiology. A discussion of the tests that would rule out a neurologic etiology is beyond the scope of this article, but in all cases of neurologic eye disease the clinician should use his or her professional judgement in deciding when to obtain consultation or make a referral. When in doubt, such consult or referral should be prompt, and the patient should be evaluated by a neuro-ophthalmologist, a neurologist, or an optometrist skilled in neuroeye disease.

Sudden Vision Loss

Frequent causes include arteritic and nonarteritic anterior ischemic optic neuropathy, branch or central retinal artery occlusion, ocular ischemia, optic neuritis, pituitary apoplexy, ischemic or hemorrhagic stroke, and acute meningitis.^2-4

Ptosis

An acquired ptosis may occur in conditions such as a third cranial nerve palsy, myasthenia gravis, and Horner syndrome (carotid artery dissection, intracranial malformations, and apical lung lesion).^2-4

Binocular Diplopia

This condition may be caused by cranial nerve paresis (due to aneurysm, arteritic anterior ischemic optic neuropathy, multiple sclerosis, stroke, tumors), myopathies (myasthenia gravis), and nutritional deficiency (Wernicke encephalopathy). Diplopia is the most common symptom of the efferent system. Cranial nerve 3, 4, and 6 palsies, myasthenia gravis, thyroid eye disease, skew deviation, internuclear ophthalmoplegia, chronic progressive external ophthalmoplegia, and dorsal midbrain syndrome (a.k.a. Parinaud syndrome) should all be ruled out.^2-4

Anisocoria

Nonphysiologic anisocoria may present in partial or complete third cranial nerve paresis (cerebral aneurysm/ischemia), Horner syndrome, and uncal (transtentorial) herniation.^2-4

An example of a true ocular emergency affecting the efferent system is a pupil-involved third cranial nerve palsy. The presenting signs and symptoms may signal an apparent aneurysm that could eventually rupture and lead to a subarachnoid hemorrhage. Also known as the oculomotor nerve, the third cranial nerve supplies several extraocular muscles, the levator muscle, the ciliary muscle, and the iris sphincter.⁵

Because of this nerve’s vast representation, a third nerve palsy has a varied presentation that can include ocular movement disturbances, ptosis, and pupillary abnormalities such as a sluggish or dilated fixed response. In this instance, time is of the essence to rule out a compressive lesion (aneurysm), giant cell arteritis, pituitary apoplexy, midbrain infarction, or demyelinating disease. Blood tests, along with certain neuroimaging techniques such as MR angiography or CT angiography, must be performed.⁵

Papilledema

True papilledema is defined as optic disc swelling due to high intracranial pressure (ICP).⁶ Its causative conditions can include hydrocephalus, spinal cord lesions, cerebral sinus drainage impairment, intracerebral mass, idiopathic intracranial hypertension (Figures 1–3), cerebral hemorrhage, and meningitis (see Differential Diagnosis of Bilateral Disc Edema).

A thorough neuro-ophthalmic workup helps the clinician sort through the many differential diagnoses. Visual function loss is the feared morbidity of papilledema. Treatment is directed at the underlying cause of the high ICP, and options include both medical and surgical modalities.

Nystagmus

Nystagmus is a spontaneous, repetitive, to-and-fro movement of the eyes. Acquired nystagmus may result from transient ischemic attack, stroke, intracranial hemorrhage, demyelinating disease, or tumor.⁷

The two main types of acquired adult nystagmus are jerk, named for its fast corrective phase, and pendular, which has slow, back-and-forth phases. Neoplastic disease presenting as an acquired nystagmus may involve brain stem and/or cerebellar-vestibular pathways from the otoliths to the cerebellum, and from the entire brainstem up to the thalamus.⁷

Head and Neck Trauma

Neuro-ophthalmic signs may include carotid-cavernous fistula (CCF), painful Horner syndrome (secondary to carotid artery dissection), and traumatic optic neuropathy. CCF is an abnormal connection between the cavernous sinus and the carotid artery and/or its branches.⁸ A CCF may be either direct (high-flow) or spontaneous (indirect or low-flow). CCF can develop because of either trauma or spontaneous causes. Traumatic CCF may occur after a head injury in which the intracavernous carotid artery is torn.⁸ Patients with CCF present with the classic triad of chemosis, pulsatile exophthalmos, and ocular bruit. Proptosis, diplopia, and visual loss may result from these fistulas.⁸

KNOW WHAT TO LOOK FOR

Sudden-onset ptosis, a dilated pupil, diplopia, and a sore scalp with jaw pain are among the signs and symptoms of a neuro-ophthalmic condition that can threaten sight and life. The optometrist is sometimes the first health care practitioner the patient sees. It is essential to know how to take a proper history, conduct a thorough examination, and order laboratory testing and imaging, and when to refer a patient to the appropriate subspecialist in order to ensure timely treatment and management.