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Managing neuro-ophthalmic emergencies

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Figure 1. A 63-year-old man with sudden onset head pain, diplopia, down-and-out position of the right eye, ptosis, and mid-dilated, unreactive right pupil from CN III palsy caused by an intracranial aneurysm  

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Dr Joseph Sowka
OD FAAO Diplomate

 

When thinking of ocular emergencies, retinal detachment, acute angle closure and chemical burns typically come to mind. While these conditions carry a high burden in potential visual loss, there exist several neuro-ophthalmic conditions that clinicians cannot afford to miss that carry an even higher risk of not only visual morbidity but even potential patient mortality.

Cranial nerve III palsy

A patient with acute cranial nerve (CN) III palsy will usually present with a sudden onset of unilateral ptosis and ophthalmoplegia, which is frequently accompanied by significant eye or head pain dependent on the cause.1-4 The patient often complains of double vision, though in some cases the diplopia may be masked by the ptosis which obscures the vision in the affected eye; however, if the lid is manually elevated, the patient will experience diplopia. (Figure 1)

CN III palsy produces a non-comitant exotropic, hypotropic eye position (down and out). There is limitation of elevation, depression and adduction. There is an underaction of the superior, inferior and medial recti muscles and inferior oblique muscle.1-3 In any case of CN III palsy, the pupil may be dilated and minimally reactive to light (pupillary involvement), or totally reactive and normal (pupillary non-involvement) or may be sluggishly responsive (partial pupillary involvement).3,4,7-10

The main concern in an isolated CN III palsy occurring within the subarachnoid space is compression of the nerve by an expanding aneurysm of the posterior communicating artery. Additionally, aneurysmal compression can occur from the internal carotid, basilar, anterior communicating or temporal arteries.8,9 Aneurysmal compression is marked by head or retro-orbital pain and anisocoria with ipsilateral pupil dilation as the expanding aneurysm compresses the pupillomotor fibres within CN III as well as pain sensitive dura and other such structures.

Approximately 15 per cent of isolated CN III palsies occurring secondary to damage within the subarachnoid area are due to aneurysms.11 In these cases, there is a high risk of morbidity or mortality from aneurysm rupture and subsequent subarachnoid haemorrhage. Approximately 20 per cent of patients with aneurysmal CN III palsy will die within 48 hours from rupture and intracranial haemorrhage. In cases of CN III palsy caused by subarachnoid aneurysm, immediate neurosurgical intervention is necessary. Common endovascular treatment involves direct clipping of the aneurysm or embolisation with detachable coils. These patients need to be sent immediately to the hospital emergency department, by ambulance, if necessary, with detailed notes on the suspected diagnosis.

Vision loss from giant cell arteritis

Giant cell arteritis (GCA) is a granulomatous inflammation of medium and large-sized arteries.12 There is cellular infiltration of the muscular wall of these vessels by T lymphocytes, macrophages, histiocytes, plasma cells and multinucleate giant cells.13,14

The inflammatory cells produce matrix metalloproteinases that digest the arterial walls, fragmenting the elastic lamina and causing tissue destruction. Vascular endothelial growth factor (VEGF) produced by multinucleate giant cells causes smooth muscle proliferation and migration towards the vessel lumen. This in combination with neoangiogenesis causes intimal hyperplasia with obliteration and occlusion of the vessel lumen.13,14

The patient suffering from giant cell arteritis (GCA) is invariably elderly, with the mean age of 71 years at presentation. There is an increasing incidence with advancing age.1 This condition is generally considered only after the age of 50 years. There is a 2:1 female to male ratio and a higher incidence in Caucasian patients.15

There is a multitude of systemic manifestations that can accompany and signal the presence of GCA, including malaise, weight loss and anorexia, headache about the temporal or occipital region, pulseless and indurated temporal arteries, night sweats, tongue necrosis and oral ulceration, dental abscess, scalp pain, scalp necrosis, jaw claudication when eating, head and neck swelling, anaemia, depression, mental disturbance, neck pain, low grade fever, transient ischaemic attack and stroke, proximal myalgia, breast masses, gynecological disorders, malignant disease, persistent flu-like illness, chronic pharyngitis, vertigo, muscle aches, cardiac arrhythmia, congestive heart failure and myocardial infarction.16,17

Too often, patients with GCA are diagnosed following sudden, devastating vision loss in one or both eyes. The cause typically is arteritic anterior ischaemic optic neuropathy (AAION). (Figure 2) In approximately 10 per cent of GCA cases, central retinal artery occlusion (CRAO) is the underlying cause of vision loss.17 Sudden, permanent vision loss is preceded by the ominous warning sign of bouts of amaurosis fugax in approximately 30 per cent of cases.13 Progression to bilateral vision loss has been known to occur with a time interval of 1-14 days between involvement of the two eyes; hence, the emergency nature of this disease.

964 Neuro _Emergencies 03 F

Figure 2. Pale, swollen optic disc from arteritic anterior ischaemic optic neuropathy in a patient with giant cell arteritis

Management begins with the recognition that GCA may be a potential cause of the aforementioned findings in an elderly patient. Any unexplained ocular findings, involvement of multiple vessels, or idiopathic systemic deterioration in an elderly patient should immediately raise suspicions. Once GCA is recognised as a potential cause, immediate referral to a hospital emergency department for testing to include erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) must be undertaken.

The ESR, a non-specific index of illness, is typically elevated in cases of GCA; however, there will be a small percentage of cases that will not manifest an elevated ESR. In these cases, supplemental confirmatory evidence provided by the CRP (a marker of inflammatory activity) is helpful. Additionally in these cases, the ophthalmic findings and systemic history become diagnostically more important. If the ESR or CRP is elevated, or if there are obvious constitutional symptoms, a temporal artery biopsy must be performed to conclusively diagnose GCA.18,19 Again, patients suspected of having vision loss from GCA should be sent immediately to the emergency department with detailed notes on the presumptive diagnosis and recommended management.

Unquestionably, systemic steroids are needed to preserve vision and reduce morbidity and mortality;18,19 however, steroids should not be withheld pending biopsy results. If history, examination findings and serology indicate GCA, steroids must be started without delay. Biopsy results will not be immediately affected after initiation of steroid therapy.

Unquestionably, GCA is an ocular and systemic emergency. Untreated, progression involving the fellow eye occurs in a high number of cases within hours to days. Frequently, vision loss in GCA is devastating and irreversible, and may progress despite seemingly adequate treatment. Giant cell arteritis may present insidiously without vision loss. Headache arising de novo in elderly patients is uncommon and a reason to suspect GCA. It is not unreasonable to recommend that a patient’s general practitioner obtain ESR and CRP testing on elderly patients complaining of headache despite a normal ophthalmic examination.

Horner syndrome

Horner syndrome is characterised by an interruption of the oculosympathetic nerve supply somewhere between its origin (in the hypothalamus) and the eye. The classic clinical findings associated with Horner syndrome are ptosis, pupillary miosis, facial anhidrosis, apparent enophthalmos, increased amplitude of accommodation, heterochromia of the irides (if congenital or occurring before the age of two years), paradoxical contralateral eyelid retraction, transient decrease in intraocular pressure and changes in tear viscosity.20 (Figure 3)

964 Neuro _Emergencies 02 F

Figure 3. Left ptosis and miosis in a patient with new onset Horner Syndrome

Apraclonidine 1% and 0.5% (Iopidine, Alcon Laboratories, Ft Worth, TX) can be used effectively to diagnose Horner syndrome.21-23 The theory is that the Horner syndrome pupil undergoes denervation hypersensitivity with upregulation of both the number and sensitivity of available receptors. When a very weak alpha-1 adrenergic agonist is applied, the hypersensitive pupil dilates while the normal pupil has no effect. In most cases, there will be a reversal of the anisocoria.

The common aetiologies of acquired Horner syndrome include but are not limited to: trauma, aortic dissection, carotid dissection, tuberculosis, and Pancoast syndrome.24-25

If the patient reports recent ipsilateral neck trauma, neck and face pain, ipsilateral transient monocular visual loss, or contralateral transient weakness or numbness, acute cervical carotid dissection must be immediately suspected. Cervical carotid dissection is a relatively common cause of acute onset Horner syndrome.26 In this case, there is a substantial risk of hemispheric (middle cerebral artery distribution) stroke within the first two weeks of onset. Patients presenting with Horner syndrome suspected to be caused by carotid dissection should be considered to be in an emergency situation and referred promptly to the emergency department for diagnosis and treatment to prevent cerebrovascular stroke.

In general, the treatment for Horner syndrome depends on the cause. In many cases, there is no treatment that improves or reverses the condition. Treatment in acquired cases is directed toward eradicating the cause. Recognising the signs and symptoms is tantamount to early diagnosis, as is making expedient referrals to appropriate medical specialists.

 

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