Neuro-Ophthalmology

Robert M. Mallery

Sashank Prasad

VISUAL LOSS SEEN BY THE NEUROLOGIST

Retinal Causes

Amaurosis Fugax

Background

Amaurosis fugax refers to transient monocular blindness of vascular origin due to retinal or optic nerve ischemia. It commonly occurs secondary to an embolus to the central retinal artery or its branches, but it also may precede permanent visual loss from giant cell arteritis (GCA). Amaurosis fugax typically lasts seconds to minutes. The classic description is of a dark shade progressing downward or upward, although other variations may occur.

Pathophysiology

Emboli to the retinal circulation may be of three major types: cholesterol (which has a yellow, shiny appearance), calcium (which appears chalky white), and platelet fibrin. If the embolus has lysed spontaneously, then the visual loss is transient and no retinal abnormalities are apparent on examination. If not, then either a central retinal artery occlusion (CRAO) or branch retinal artery occlusion occurs, with edema and pallor of the affected territory in the acute phase.

Amaurosis fugax frequently heralds CRAO or arteritic ischemic optic neuropathy (ION) due to GCA, and clinical suspicion must be high as 15% of patients with visual loss due to GCA have no systemic symptoms of arteritis.

Some forms of transient monocular blindness are not caused by emboli or GCA. These include retinal migraine and vasospasm, which presents with recurrent, self-limited bouts of decreased perfusion to the retinal arterioles.

Prognosis

Transient monocular blindness owing to embolic disease carries a risk of subsequent retinal occlusion, parenchymal ischemic stroke, or transient ischemic attack. Arteritic CRAO or ION with invariably occurs without rapid corticosteroid treatment in patients presenting with amaurosis fugax.

Diagnosis

Careful attention must be paid to the duration of the attacks, associated symptoms at the time of the attacks, frequency of the attacks, extent of visual loss, and precipitating factors. In most cases, an ophthalmologist should also be involved in the patient’s care because a dilated fundus examination is essential to look for signs of retinal ischemia or emboli in the retinal arterioles. Diagnostic evaluation should include carotid imaging, echocardiogram, long-term telemetry monitoring, and a lipid panel. In young patients, a search for causes of hypercoagulability may be warranted. ESR and CRP levels should be checked in all patients more than 50 years old.

Treatment

1. If symptomatic severe carotid stenosis is found, then either endarterectomy or stenting may be considered.
2. If atrial fibrillation, a cardiac thrombus, or a hypercoagulable state is revealed, anticoagulation is indicated. Elevated cholesterol may be managed with statin therapy.
3. Retinal migraine, relating to recurrent attacks of vasospasm, may respond to the use of calcium channel blockers.
4. When no clear cause is identified but the patient has other vascular risk factors such as hypertension or diabetes, the treating physician may recommend antiplatelet therapy such as aspirin or clopidogrel.

Optic Neuropathies

Optic nerve injury often presents with impaired acuity and color vision because of the high proportion of optic nerve retinal ganglion cells and axons serving the central macular vision. Patients with optic neuropathy may present with varied patterns of visual loss including central or cecocentral (stretching from the physiologic blind spot to fixation) scotoma, arcuate scotomas (following the arc-like trajectory of retinal nerve fibers), or altitudinal defects (although the latter may occur with superior or inferior branch retinal artery occlusion as well). An optic neuropathy is suggested by a relative afferent pupillary defect, which manifests as a dilation of both pupils when a light source is swung from the intact eye to the one with the optic neuropathy (the swinging flashlight test), although this sign may also occur with severe retinal disease such as a CRAO.

Anterior Ischemic Optic Neuropathy

Anterior ischemic optic neuropathy (AION) may be divided into two forms: arteritic (due to GCA or other vasculitides) and nonarteritic.

Giant Cell Arteritis

Background

The incidence of GCA correlates with age, and it is exceedingly rare for it to occur prior to 50 years of age. Patients with polymyalgia rheumatica carry an increased risk. Headache, especially scalp tenderness, is a regular feature, and other symptoms include jaw claudication, myalgias, fever, and weight loss.

Pathophysiology

Inflammation of the media of extracranial medium-sized arteries narrows the lumen and leads to thrombosis and ischemia. GCA may cause anterior ION, with optic disc swelling, as well as CRAO. ION may also affect the retrobulbar optic nerve, producing an ION with no changes in the appearance of the optic nerve head (posterior ischemic optic neuropathy).

Prognosis

GCA is an acute illness and neuro-ophthalmic emergency. Early clinical diagnosis and treatment are required to mitigate the risk of severe bilateral visual loss. In rare cases, GCA may be complicated by posterior circulation stroke, myocardial infarction, or aortic dissection.

Diagnosis

1. Arteritic AION presents with sudden vision loss in one eye, sometimes preceded by amaurosis fugax. Pallid optic disc swelling is characteristic, often with peripapillary splinter hemorrhages.
2. If untreated most patients with unilateral arteritic AION would develop fellow eye involvement within weeks. Bilateral simultaneous arteritic ION may also occur.
3. The finding of AION with cilioretinal artery occlusion is virtually pathognomonic of GCA.
4. Associated symptoms result from involvement of branches of the external carotid artery and include headache, scalp tenderness, and jaw claudication. Systemic symptoms that often accompany the disease include fatigue, fever, and myalgias. Important signs include a distended and tender temporal artery.
5. Approximately 15% of cases of arteritic ION have no associated systemic features, so-called “occult GCA.”
6. When suspected, GCA should prompt an immediate search for associated laboratory abnormalities including an elevated erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and thrombocytosis. Treatment with corticosteroids should not be delayed while awaiting these results. ESR elevation is 95% sensitive, and CRP elevation is 97% sensitive, but in rare cases both may be normal.
7. A definitive diagnosis may be made with a temporal artery biopsy revealing a lymphocytic infiltrate with or without giant cells. The window for obtaining the biopsy is within 7 days after starting the prednisone, although it should be performed as soon after starting therapy as possible.
8. Ultrasound of the temporal and other cranial arteries may aid in the diagnosis of GCA by demonstrating the “halo sign” in affected arteries. Ultrasound may also aid in identifying a segment of temporal artery for biopsy. Sensitivity of ultrasound also decreases with steroid treatment.

Treatment

1. High doses of intravenous (IV) corticosteroids are indicated when the patient with suspected GCA is experiencing transient or persistent visual loss.
- a. A typical regimen is 3 days of 1 g/d of methylprednisolone followed by high doses (at least 1 mg/kg) of oral prednisone or oral methylprednisolone.
2. In cases without imminent threat of visual loss or stroke, high-dose oral prednisone can be started. There are no good data to definitively establish an appropriate dosage, but 1 mg/kg of body weight of prednisone per day is usually adequate.
- a. Despite having many side effects, prednisone therapy must be prolonged for most patients with GCA. After high doses are used for approximately 2 months, the dose can be slowly weaned. As a rule of thumb, the typical course may extend between 9 and 12 months, but individual cases vary.
3. The addition of other immune-modulating drugs, particularly tocilizumab (IL-6 inhibitor), allows a more rapid taper of prednisone and may aid in steroid-resistant disease.

Nonarteritic Anterior Ischemic Optic Neuropathy

Background

Nonarteritic anterior ischemic optic neuropathy (NAION) is typically seen in older patients with vascular risk factors, especially hypertension and diabetes. Most patients have a “crowded” optic disc, with a congenitally small or absent optic nerve cup. Severe blood loss, coronary bypass surgery, and prolonged surgical procedures with the patient prone are other causes.

Pathophysiology

The best evidence at this time suggests that there is an occlusion or reduction of blood flow in the posterior ciliary arteries, which supply the optic nerve head. The ensuing
ischemia seems to start a pathologic cascade of edema that further compromises perfusion and leads to additional ischemia and swelling. Associations have been made with diabetes, hypertension, smoking, obstructive sleep apnea, hyperlipidemia, nocturnal hypotension, and the use of phosphodiesterase inhibitors.

Prognosis

1. The visual loss in the affected eye usually remains static, but a minority of patients has a partial recovery.
2. The lifetime incidence of involvement of the other eye is approximately 30%.

Diagnosis

1. NAION can mimic arteritic ION except that the amount of vision loss may be less and the associated symptoms and signs of GCA are not present.
2. In the acute stage, the disc in NAION appears swollen and hyperemic, typically with splinter hemorrhages. The swelling may be sectoral, sparing a segment of the optic disc and corresponding with the area of visual field loss.
3. A finding of a small cup-to-disc ratio in the fellow eye aids the diagnosis.
4. Fluorescein angiogram shows normal filling of the choroidal circulation as fluorescein transits the retinal arterioles, and mid to late frames demonstrate leakage at the disc.
5. Occasionally, patients with risk factors present with sectoral optic disc swelling without visual field loss.
6. The phosphodiesterase inhibitor sildenafil has in some cases appeared to be associated with NAION. The same population of patients using this medication also has typical vascular risk factors for NAION, and it has been difficult to ascertain the exact proportion of case that can be definitively attributed to use of the medication.

Treatment

1. There is no convincing evidence that any therapy alters the natural history of this condition.
2. It is reasonable to recommend that patients avoid taking antihypertensive medications at bedtime because nocturnal hypotension is considered a possible provoking factor.
3. If the patient has an elevated intraocular pressure, topical medications that normalize the pressure may be indicated.
4. A large randomized trial showed that optic nerve sheath decompression is not helpful.
5. Untreated obstructive sleep apnea may be a risk factor for AION, possibly because of nocturnal hypoxia. Patients with symptoms suggestive of OSA should be referred for a sleep study and treatment if confirmed.
6. Treatment with prednisone until the optic disc swelling resolves is occasionally offered in monocular patients or patients with involvement of the second eye, although the efficacy is uncertain and appropriate dosing is based on limited evidence.

Diabetic Papillitis

Background

Diabetic patients may present with optic disc swelling with no or minimal visual loss.

Prognosis

Some patients with diabetic papillopathy progress to develop significant vision loss related to NAION, but in others, the optic disc swelling remits without visual loss.

Idiopathic Demyelinating Optic Neuritis

Background

This is a common cause of monocular loss of vision in a young person, especially females, and often occurs in association with multiple sclerosis (MS).

Prognosis

As demonstrated in the Optic Neuritis Treatment Trial, 95% of patients generally recover to 20/40 or better by a year. Most of the improvement occurs by 6 months. Although most cases improve without treatment, baseline vision may not return. Permanent impairment of low contrast visual acuity and color vision is common.

Diagnosis

1. A clinical diagnosis of optic neuritis can be made in a patient presenting with typical symptoms of subacute vision loss, a relative afferent pupillary defect, pain with eye movement, and fundus exam showing either mild optic disc edema or normal optic nerve head in the case of retrobulbar optic neuritis.
2. Contrast-enhanced magnetic resonance imaging (MRI) of the orbits and brain supports the diagnosis, which usually reveals enhancement of the optic nerve. The finding of asymptomatic T2 hyperintensities or enhancing T1 lesions may contribute to an early diagnosis of MS.

Treatment

1. Based on the Optic Neuritis Treatment Trial, optic neuritis treated first with 3 days of IV methylprednisolone at a dose of 1 g/d, followed by oral steroids at a dose of 1 mg/kg for 11 days with a 4-day taper (20, 10, 0, and 10 mg), resolves more rapidly than when not treated. However, there will be no significant effect on visual acuity at a year. The use of IV steroids for optic neuritis is not absolutely indicated unless it is bilateral or the patient has poor vision in the unaffected eye.
2. Patients treated with IV steroids are less likely to be diagnosed with clinically definite MS within the next 2 years. After 2 years, however, the incidence of MS in the treated and nontreated groups becomes equivalent.
3. In patients with optic neuritis and evidence of subclinical demyelination on brain MRI, disease-modifying treatment should be considered.

Neuromyelitis Optica

Background

NMO was described by Devic as a concomitant optic neuritis with transverse myelitis. It is now understood that years may separate one event from the other and that episodes may recur.

Prognosis

Visual loss in NMO tends to be of greater severity than that of MS-related optic neuritis, with less recovery.

Diagnosis

The 2015 criteria outline the diagnosis of NMO spectrum disorders, stratified according to the presence or absence of the aquaporin-4 antibody. Seronegative patients must have either optic neuritis, longitudinally extensive myelitis, or the area postrema syndrome. For seropositive patients, the criteria are relaxed, and the clinical syndrome may include any of those listed earlier, or a diencephalic syndrome, other brainstem syndrome, or other cerebral syndrome. The revised criteria reflect growing recognition of the high specificity of the aquaporin 4-IgG test using evolving methods such as the cell-based assay.

Treatment

The optic neuritis of NMO may be treated with high-dose IV steroids, but in cases with severe deficits, strong consideration should be given to treatment with plasmapheresis. Among maintenance therapies, rituximab has been particularly promising. Other treatment options include mycophenolate mofetil and azathioprine. Accurate diagnosis is critical because agents used to treat MS, such as interferon β, natalizumab, and fingolimod, have been shown to worsen the disease course in patients with NMO spectrum disorder.

Myelin Oligodendrocyte Glycoprotein Antibody Disease

Background

Myelin oligodendrocyte glycoprotein antibody disease is recently recognized as distinct autoimmune demyelinating disorder from NMO or MS and is associated with an antibody to myelin oligodendrocyte glycoprotein a cell surface protein on oligodendrocytes. Optic neuritis is the most common clinical manifestation (more than 50%), and transverse myelitis, acute disseminated encephalomyelitis (in children), and brainstem encephalitis are other common manifestations.

Prognosis

MOG-IgG optic neuritis typically causes severe visual loss at onset (median acuity of counting fingers), but prognosis for recovery is good with approximately 10% of patients having poor visual outcomes (visual acuity worse than 20/200).

Diagnosis

Diagnosis is confirmed with a positive MOG IgG cell-based assay. Certain clinical features also distinguish MOG IgG optic neuritis from NMO and MS. MOG IgG optic neuritis is frequently bilateral with severe visual loss at onset. There is a greater tendency for recurrence or steroid dependence. Fundus examination characteristically shows bilateral optic disc edema with associated hemorrhages unlike other forms of optic neuritis. MRI frequently shows longitudinal optic nerve enhancement with perineuritis.

Treatment

Patients typically have a rapid response to 1 g/d of IV methylprednisolone given for 3 to 5 days followed by high-dose oral prednisone (1 mg/kg). Oral prednisone is tapered over 1 to 2 months to prevent relapse. Fifty percent of patients with MOG IgG optic neuritis have a future relapse, so long-term immunosuppression is reserved for those with relapsing disease or with more severe disability (NMO-like presentation with myelitis and optic neuritis). Rituximab, azathioprine, mycophenolate mofetil, and IVIG have shown a reduction in relapse rate, with IVIG being the most effective.

Papilledema

Background

Papilledema refers to swollen, elevated optic discs resulting from increased intracranial pressure (ICP). Unlike other optic neuropathies, early papilledema tends to spare visual acuity, color vision, and the central field because the papillomacular bundle is relatively spared. Instead, papilledema commonly manifests with blinds spot enlargement and peripheral visual field loss, often of the inferior nasal quadrant. Left untreated, however, acuity can eventually be severely affected.

Prognosis

1. This depends on the duration and severity of the papilledema.
2. Certain associated findings indicate a poor prognosis for vision loss in cases of papilledema. The major one is systemic hypertension. Others are high-grade disc edema, peripapillary subretinal hemorrhages, visual acuity loss at presentation, old age, myopia, retinochoroidal collateral vessels, and glaucoma.

Diagnosis

1. Imaging with a contrast-enhanced MRI or computed tomography (CT) should be the first diagnostic step in the evaluation of papilledema to evaluate for a mass lesion as the cause.
2. MR or CT venogram (MRV or CTV) should also be acquired to rule out a cerebral venous sinus thrombosis.
3. Lumbar puncture (LP) confirms elevated pressure but should only be performed once imaging has ruled out a mass lesion that could result in herniation. The opening pressure should be evaluated with the patient in the lateral decubitus position, as relaxed as possible with his or her legs extended.
4. LP is required to detect inflammatory, infectious, or neoplastic infiltration of the CSF that has caused elevated ICP.
5. In the face of a negative MRI/MRV, elevated ICP, and normal CSF constituents, a diagnosis of idiopathic intracranial hypertension (IIH, pseudotumor cerebri) is confirmed. This typically occurs in young, obese women who present with headache, pulsatile tinnitus, and papilledema. Horizontal diplopia from sixth nerve dysfunction may be present. The condition may remit after a year or two but in some patients appears to be a chronic condition.
6. A common but often overlooked cause of bilateral optic disc swelling is malignant hypertension. Blood pressure should be measured, and the fundus should be examined for signs of retinal damage.

Treatment

1. Mass lesions responsible for elevated ICP should be treated appropriately.
2. If the occurrence of raised ICP can be attributed to a medication such as tetracycline, vitamin A, nalidixic acid, nitrofurantoin, or lithium, these drugs should be discontinued.
3. Inflammatory causes such as sarcoidosis may be treated with steroids.
4. Infectious causes should be treated with the appropriate antibiotics.
5. The treatment of leptomeningeal neoplasm depends on the type of tumor but may involve radiation and/or chemotherapy or immunotherapy.
6. Acetazolamide may be used to lower ICP and is the first-line treatment for patients with IIH. Some physicians use up to 4 g/d. Furosemide or topiramate are other treatment options to inhibit spinal fluid production. Both acetazolamide and topiramate may precipitate renal stones
7. Weight reduction is a critical aspect of the management of patients with IIH.
8. If medical therapy is not effective and visual deficits are progressing, then ICP may be lowered with either a ventriculoperitoneal or lumboperitoneal shunt. Patients may be admitted for a lumbar drain while awaiting definitive surgical treatment.
9. Optic nerve sheath decompression is an alternative method, particularly for patients with progressive visual loss in the absence of refractory headache.
10. A single LP does not have lasting benefit, but repeated LP can be effective, although impractical.
11. Placement of a stent in the transverse venous sinus is an investigational therapy to be considered in the setting of venous sinus stenosis with an abnormal trans-stenosis pressure gradient of greater than ˜8 mm Hg. Eliminations of the stenosis lowers the venous pressures in the transverse and sagittal venous sinuses, promoting better absorption of CSF.
12. In cases in which there is coexistent systemic hypertension and raised ICP, caution must be used in lowering the systemic blood pressure, as a sudden drop in blood pressure may precipitate further vision loss.
13. Complications of surgical treatments for IIH are reviewed in Table 16-1.

Table 16-1 Complications and Risks of Surgical Treatments of Refractory Idiopathic Intracranial Hypertension

Ventriculoperitoneal Shunt (VPS)	Lumboperitoneal Shunt (LPS)	Optic Nerve Sheath Fenestration	Venous Stenting
Requires craniotomy and associated risks of hemorrhage, infection, and seizure Low-pressure headaches, treatable with programmable shunt	Requires more revisions than VPS Increased risk of shunt obstruction compared with VPS Abdominal pain Migration of shunt Acquired Chiari malformation	Late failures may occur May not control headaches Ocular motility disorders (often temporary) Conjunctival blebs Orbital hemorrhage Optic nerve trauma Orbital apex syndrome Intraoperative angle closure glaucoma Deterioration of visual function, transient blindness Central or branch retinal artery occlusion	Risk for in stent thrombosis and venous stroke Patients need dual anti-platelet therapy for at least 6 wk, followed by aspirin monotherapy, increasing bleeding risk if other surgical procedures are needed.

Compressive and Intrinsic Optic Neuropathies

Pathophysiology

Most of the visual deficits caused by these entities are because of direct compression of axons, but in some cases, interruption of blood supply plays a part. The unifying feature is that visual loss tends to be progressive. Tumors that tend to compress the optic nerve include meningiomas of the sphenoid wing, optic nerve sheath meningiomas, pituitary tumors with anterior extension, and metastases to the orbit. Aneurysms of the ophthalmic segment of the internal carotid artery (ICA) may also compress the optic nerve. Gliomas may arise within the optic nerve during childhood, in which
case the pathology is that of a benign pilocytic astrocytoma. These tumors typically arise in association with neurofibromatosis type 1. Optic nerve gliomas in adults are exceedingly rare but are typically malignant (glioblastoma multiforme) and carry a very poor prognosis.

Prognosis

Duration of the insult and age of the patient are important variables.

Treatment

1. For compressive lesions, the main therapeutic approach is to resect the lesion and decompress the optic nerve.
- a. When a meningioma extrinsically compressing the nerve is causing visual loss, surgical excision is often the first-line therapy. If the meningioma has aggressive features, or residual tumor shows growth, then adjuvant radiation therapy may also be beneficial.
- b. For meningioma of the optic nerve sheath, the decision to operate can be more challenging because surgery may often be complicated by vision loss from disruption of blood supply to the optic nerve. Radiation of optic nerve sheath meningiomas has some benefit, but the effect is often temporary. As long as visual loss from an optic nerve sheath meningioma is minimal, observation with serial examinations is often the most reasonable option. When the clinical presentation and radiologic findings are characteristic, tissue diagnosis is often unnecessary.
- c. Malignant adult optic nerve gliomas have a relatively poor prognosis and are treated as would glioblastoma multiformes in other locations, with a combination of resection, radiation, and chemotherapy.

Neoplastic Optic Neuropathies

Background

The optic nerve may rarely be affected by malignant infiltration through the leptomeningeal space or at the optic nerve head. The most common scenario is of leukemic infiltration, which is an emergency, because permanent visual loss may result without prompt treatment. In addition, paraneoplastic optic neuropathies may very rarely occur in association with the anti-CRMP5 protein.

Prognosis and Treatment

Urgent radiation to the optic nerve head or chemotherapy may lead to quick resolution of the optic neuropathy.

Radiation-Induced Optic Neuropathy

Background

1. Radiation necrosis of the optic nerves can occur in patients previously treated with radiation for tumor near the optic nerves.
2. The concomitant use of some chemotherapeutic agents appears to accelerate the process.

Prognosis

Although prognosis is generally poor, there are exceptions.

Treatment

1. This condition, which may occur a year or more after radiation to the optic nerve, is virtually untreatable.
2. There are advocates for the following treatments:
- a. Hyperbaric oxygen for at least 20 sessions for 90 minutes at 2.4 atmospheric pressure.
- b. IV Solu Medrol 1 g/d for 3 days followed by a 2-week oral taper may be used at the same time.
- c. The addition of pentoxifylline 400 mg two or three times a day has also been recommended.
- d. Bevacizumab has shown some benefit in anecdotal reports.

Leber Hereditary Optic Neuropathy

Background

This mitochondrial disease presents with acute to subacute severe, painless visual loss in one eye, typically followed within weeks to months by a similar occurrence in the fellow eye. It usually occurs in young males but may occur in females and has been reported in older patients as well.

Diagnosis

A family history compatible with mitochondrial inheritance may aid the diagnosis, but frequently patients have no family history of optic neuropathy due to Leber hereditary optic neuropathy’s (LHON’s) low penetrance. The metabolic nature of the disease leads to papillomacular bundle injury producing cecocentral scotomas. Mild edema in the retinal nerve fiber layer surrounding the optic nerve and telangiectatic blood vessels on and near the disc in the early phases are characteristic.

Dominant Optic Atrophy (Kjer Disease)

Background

Patients with this condition present with chronic progressive bilateral optic neuropathies, usually in childhood although the diagnosis can also be made in adults.

Prognosis

Vision generally stabilizes at no worse than 20/200 but may also be significantly better.

Nutritional and Toxic Optic Neuropathies

Background

Certain toxins and medications may produce damage to the optic nerve as may chronic nutritional deficiencies.

Prognosis

Prognosis depends on etiology. In the case of ethambutol toxicity, there may be improvement with cessation of therapy.

Traumatic Optic Neuropathies

Background

This entity is considered when vision loss after head injury is not explained by direct trauma to structures of the globe.

Prognosis

Some cases improve spontaneously, whereas others require surgical decompression. In other cases, the prognosis can be poor, without effective treatment.

DISORDERS OF THE SELLA AND CHIASM

Background

Compression of the optic chiasm typically causes a bitemporal hemianopia because of compromise of decussating fibers subserving the temporal field of each eye. The most common cause of chiasmal injury is compression by a tumor, most commonly by a pituitary adenoma. If the adenoma is prolactin-secreting, the patient may have loss of libido, amenorrhea, and galactorrhea from the hormonal imbalance. Acute bitemporal field defects may occur from sudden hemorrhage within a pituitary tumor (pituitary apoplexy) that may also cause acute ophthalmoplegia as the expanding tumor and hematoma extends laterally into the cavernous sinus. Craniopharyngiomas, which are more frequent in children and typically include cystic spaces and calcium deposits, may compress the chiasm from above. Other causes of chiasmal injury include Rathke cleft cysts, meningiomas, and trauma, whereas intrinsic disease may take the form of demyelination or a hypothalamic/optic pathway glioma.

Presentation

Early compression from below (ie, pituitary adenomas) may lead to superior bitemporal defects, whereas compression from above (eg, craniopharyngioma) may lead to inferior bitemporal defects. If the chiasm is fixed anteriorly, optic tract compression may lead to homonymous hemianopia, whereas a posteriorly fixed chiasm may result in optic nerve compression by the tumor. If an optic nerve is affected posteriorly at its junction with the optic chiasm, then an ipsilateral central or complete scotoma may be accompanied by a superotemporal defect in the contralateral eye, together known as a junctional scotoma (a summary of various visual complications of sellar tumors may be found in Table 16-2).

Table 16-2 Visual Symptoms of Sellar Lesions

Defect	Location	Illustration
Bitemporal hemianopia	Optic chiasm
Superior bitemporal defects	Chiasm from below
Inferior bitemporal defects	Chiasm from above
Central, cecocentral, arcuate, or altitudinal defects	Optic nerve (postfixed chiasm)
Central in ipsilateral eye and superior temporal in contralateral eye	Junction of optic nerve and chiasm
Hemifield slide: Bitemporal hemianopia reduces the area of overlapping visual field, making it harder to align the eyes in cases of latent strabismus.	Horizontal diplopia (nonparalytic)
See-saw nystagmus: One eye extorts and depresses, whereas the other intorts and elevates.	Chiasm or junction of midbrain—diencephalon

Treatment

1. Surgical resection is the first-line treatment for most pituitary adenomas leading to visual loss. An endoscopic transnasal transsphenoidal approach is typically used. An open craniotomy may also be necessary, especially for meningiomas.
2. Prolactinomas may shrink in response to dopamine agonists such as cabergoline and bromocriptine.
3. Growth hormone-secreting tumors may respond to somatostatin analogues such as octreotide in conjunction with surgery.

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