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Papilledema -  

Causes of Papilledema and Disc Edema
Lecture 6 of 7  NEXT»

Hypertension

The disc edema caused by group 4 hypertension and that caused by increasing intracranial pressure appear essentially the same. The problem arises in trying to differentiate increased intracranial pressure with secondary hypertension from group 4 hypertension with papilledema and hypertensive encephalopathy. The papilledema secondary to increased intracranial pressure is limited to the posterior pole, whereas that caused by hypertension is accompanied by marked hypertensive changes that extend to the peripheral retina (Plate 2.IIC).

Subarachnoid Hemorrhage

A small group of patients with papilledema have preretinal hemorrhages that may be located in front of the disc or the macula (Fig. 2.1). This type of hemorrhage in adults almost always indicates subarachnoid hemorrhage. In infants, it suggests subdural hemorrhage. If the hemorrhage is located in front of the macula, it causes a severe decrease in vision. Unless it breaks into the vitreous humor, however, it will be absorbed, and previous vision will return. I have also seen these hemorrhages with posterior vitreous detachment.

Intraocular hemorrhages secondary to subarachnoid hemorrhage occur in about 20% of patients. The presence of these hemorrhages is highly significant in predicting the mortality rate from ruptured aneurysms. The mortality rate is about 60% when fundus hemorrhages are present but only 27% when they are absent according to Manschot, Richardson and Hyland, and Fahmy.

fig. 2.6

• Figure 2.6.
Evaluation of true nerve edema.

Mechanisms for the production of fundus and optic nerve sheath hemorrhages have been put forward by Ballantyne, Walsh and I ledges, and Muller and Deck. Some authors, like Ballantyne, believe these hemorrhages are caused by venous obstruction owing to increased intracranial pressure on Intracranial venous structures draining the rye and orbit. Walsh and Hedges believe
the cause is intracranial pressure transmitted to orbital structures. Muller and Deck evaluated 46 eyes and their orbits and optic canals in patients with increased intracranial pressure; 87% had optic nerve sheath hemorrhage, and 37% had intraocular hemorrhages. These authors concluded that orbital hemorrhages came from optic nerve sheath vessels. These hemorrhages probably do not result from increased intracranial pressure being transmitted to the orbital venous structures. Also, any increased orbital venous pressure can be dissipated by alternate venous drainage into the facial and pterygoicl vessels. These two facts militate against optic nerve sheath hemorrhages resulting from intracranial subarachnoid blood being pushed into the optic nerve sheath. Hemorrhages can be found on the optic nerve sheath in cases of increased intracranial pressure without subarachnoicl hemorrhage. These hemorrhages in the nerve sheath occur predominantly in the subdural rather than the subarachnoid space. Muller and Deck believe that the hemorrhages in the sheath may be caused by the rupture of pial vessels when the sheath is rapidly expanded during a sudden severe rise of intracranial pressure.

Muller and Deck stated that intraocular hemorrhages have a different mechanism. These hemorrhages result from sudden increases in venous ocular pressure at a level in the nerve that precludes its dissipation by alternate drainage into the facial and pterygoid vessel systems.

Vitreous hemorrhages in subarachnoid hemorrhage were first described by Terson. Vitreous hemorrhages in this clinical setting are rare. They may occur initially as large hemorrhages breaking out into the vitreous or secondarily from a subhyaloid hemorrhage that subsequently breaks the posterior vitreous face and invades the vitreous body. Hemorrhages of this magnitude represent even more serious consequences from the intracranial disease than just preretinal hemorrhages. If the patient survives, the vitreous hemorrhage will clear, which may take up to a year.

Subhyaloid hemorrhage may occur from neovascularization of the retina, as in diabetes, or from the neovascularization following a central retinal vein occlusion. The retinal diagnostic clues in diabetes, such as the exudates, are readily seen. In an old central retinal vein occlusion, the vein looks white, with vessels sprouting from the site of the obstruction.

Central Retinal Vein Occlusion

The predominant picture in central retinal vein occlusion (Plate 2.IID) is one of blood, not edema or exudate. The branch retinal vein occlusions are more readily diagnosed by those unfamiliar with the fundus picture, because the hemorrhages are limited to one quadrant of the retina.

The decrease in visual acuity associated with central retinal vein occlusion is usually marked and rapid in onset. This decrease in acuity is not seen with increased intracranial pressure, except over a long period of time and with a gradual onset. The disc in central retinal vein occlusion is plethoric. The disc in papilledema with vision loss shows a gliotic grayish appearance with white sheathing of the vessels. Papillophlebitis as initially described by Lyle and Wybar and subsequently by Lonn and Hoyt should not be confused with papilledema secondary to increased intracranial pressure. Papillophlebitis occurs unilaterally in young healthy adults. The fundus picture is usually much worse than the patient's complaints of minimal blurriness. The edema and hemorrhages on the disc and in the retina are more consistent with a vein occlusion than with papilledema. Unlike vein 4 occlusions in adults, this entity has a good prognosis. Like vein occlusion in adults, however, there is no effective treatment unless some systemic cause is revealed.

The diseases to be considered in determining the cause of central retinal vein occlusion are glaucoma, diabetes, dysproteinemias, multiple myeloma, and polycythemia vera. The evaluation of diabetes requires a formal glucose tolerance test rather than a postprandial blood glucose determination. The dysproteinemias, such as Waldenstrom's macroglobulinemia, are best diagnosed by an electrophoresis of the patient's blood serum.

Leukemia and Septic Chorioretinitis

These disorders are discussed together because of the sign they have in common Roth's spots (hemorrhages with white centers) (Plate 2.IC). In leukemia the white centers are tumor cells, whereas in septic chorioretinitis they are inflammatory white cells. Both diseases may cause disc edema. Many hemorrhages are present but usually only a few Roth's spots. When Roth's spots are present, they are located at the posterior pole and need not be looked for at the equator or beyond. The white centers in Roth's spots frequently are transient, and when they are looked for the next day, they may be filled in with blood and look like an ordinary retinal hemorrhage. Roth's spots lire seen in other diseases, including subacute bacterial endocarditis, pernicious anemia, scurvy, lupus erythematosus, and sickle cell anemia. Usually, these conditions do not cause disc edema.

Optic Neuritis

As a rule, disc edema with a decrease in visual acuity suggests optic neuritis. The appearance of the papillitis is not diagnostic; some patients with optic neuritis have good visual acuity. In these, the field defect may he so subtle that the patient is not aware of it; it must be looked for carefully.

A useful diagnostic test for evaluating papillitis with good visual acuity is the afferent pupillary defect, which indicates unilateral optic nerve disease. This phenomenon may be seen when damage to the nerve oc-curs for any reason, causing a conduction defect, even in cases of neuritis with good visual acuity. The test is performed in the following way. The physician shines a light in the affected eye, and the pupil in that eye responds, as expected, by constricting. A consensual response also occurs. The light is then moved quickly from the affected eye to the other eye—and the degree of pupillary constriction in both eyes comes down more. The light is then moved quickly back to the
affected eye, whereupon the pupil of the affected eye dilates significantly, as does the pupil in the fellow eye. The light must be moved rapidly from one eye to the other so as not to lose the constrictor effect from the normal eye. The test should be done several limes to differentiate the condition from a dilatation of the pupil owing to hippus.

Cells in the vitreous humor in front of the dime are an inconstant sign of papillitis or a relrobulbar optic neuritis. They can be seen only with the fundus contact lens, and they are not seen grossly with the ophthalmoscope. Cells in the vitreous humor can be seen in a variety of conditions—pars planitis, chorioretinitis, and cyclitis. In all these disorders, the cells cause a visible haze or debris in the vitreous humor and are not localized to the disc area.

The Hardy, Rand, Ritter (HRR) color plates are a useful screening device. Even in optic neuritis with good visual acuity, the ability to recognize the plates may be markedly different in each eye. This finding can be carried over into the field examination, in which a field defect may be more easily detected with colored test objects than with small white ones.

Infiltration of the Optic Nerve

Infiltration of the optic nerve head may give the appearance of papilledema on casual inspection. Fortunately, infiltration of the disc is rare and usually occurs unilaterally, which should alert one to an alternative diagnosis to true papilledema. Infiltration or masses on the nerve head can be seen with several disorders, such as tuberous sclerosis, sarcoid, and lymphoma (Plate 13.ID).

The eye and orbit are affected in about 25% of cases of systemic sarcoid. The perivenous candle wax dripping appearance of the retinal vasculitis is well known.

The four different manifestations of optic nerve involvement in sarcoid are optic atrophy, optic neuritis, optic nerve granuloma invasion of the nerve, and papilledema.

The papilledema may occur secondary to infiltration of the perioptic meninges or as papillitis. It may also occur secondary to true increased intracranial pressure from a mass effect or, more rarely, from direct infiltration of the disc. A patient reported by Jampol, Woodfin, and McLean and seen by us responded dramatically to systemic steroids (Plate 13.IB).

Intracranial involvement occurs in about 5% of cases of systemic sarcoid. These cases may present as cranial nerve involvement, of which seventh nerve paresis is the most common, or with hypothalamic involvement and symptoms of diabetes insipidus. Walsh and Smith have reported a case of a suprasellar tumor causing a mass effect. This mass produced diabetes insipidus, bitemporal hernianopia, and papilledema. The mass was biopsied and showed a typical non-caseating granuloma. The mass responded to steroids, and all of the symptoms and signs were relieved or markedly improved.

A firm diagnosis is difficult to establish without a biopsy. A computed tomogram is said to show a characteristic appearance. This has not held up in a series of cases reviewed by Powers and Miller. An increase in the serum angiotensin-converting enzyme has also shown promise as a laboratory aid in the diagnosis, but it is not universally elevated in all cases of sarcoid.

Other infiltrations of the optic nerve can be seen, as in lymphoid reticulum cell sarcoma. We have seen lymphoma produce this ocular presentation on several occasions; however, these patients were well known to us as patients with lymphoma and did not have optic infiltration as their initial systemic complaint. The optic nerve masses resolved under therapy but left an infarcted nerve from the infiltration (Plate 13.ID).

Reticulum sarcoma usually presents as a uveitis associated with subretinal and choroidal infiltrates and, occasionally, with disc hyperemia mimicking early papilledema.

Tumors

Orbital and optic nerve tumors can cause disc edema through obstruction of ocular venous drainage. They may also cause decrease in visual acuity, field defects, decrease in motility, and proptosis. The exophthalmos may be subtle, and exophthalmometer measurements should be part of the evaluation of unilateral papilledema or loss of acuity.

Digital exploration of the periorbital area may reveal a mass accessible to biopsy. Tumors that are truly retroorbital or are in the muscle cone are the most difficult to diagnose, but they can be diagnosed by the ultrasound technique or CT. CT or MRI with and without contrast and with coronal views are necessary.

Thyroid disease may cause unilateral loss of vision, exophthalmos, disc edema, and horizontal striae in the macular area. Although these conditions also suggest orbital tumor, a positive forced duction test and lid retraction point toward thyroid disease as the primary cause.

Intracranial tumors, particularly those along the sphenoid ridge, can cause changes that are more marked in one eye than in the other. In disc edema caused by venous compression in the superior orbital fissure, the veins appear to be disproportionately larger than in papilledema caused by increased intracranial pressure. This venous stasis may also be seen as a caput medusa (dilated veins) on the globe. As the tumor enlarges and the intracranial pressure increases, the relationship of papilledema and venous engorgement is more typical of true papilledema. A variation of this condition is the Foster Kennedy syndrome, in which the tumor, usually a frontal lobe glioma or an olfactory groove meningioma, compresses the optic nerve, causing optic atrophy. The atrophy occurs before the tumor takes up a significant amount of intracranial space. Then as the tumor grows, increased intracranial pressure develops, and the other nerve shows papilledema while the atrophic side does not. When the Foster Kennedy syndrome occurs in persons 65 years of age or older, however, it is commonly caused by vascular disease.

Longstanding increased intracranial pressure from any cause and tumor of the chiasm both bring about a bilateral decrease in acuity. Bilateral papilledema with a decrease in acuity can be confused with bilateral optic neuritis, a mistake that is likely to occur when the CT and MRI of the sphenoid ridge and sella turcica are reported as normal. Slow progressive loss of acuity is not caused by optic neuritis, however, so a compressive lesion must he considered. Suprasellar masses, such as meningioma, craniopharyngioma, or aneurysm, may cause compression of the nerves without evidence of bony changes, even with adequate tomograms of the sella turcica. A CT examination with a contrast medium should be used to rule out a suprasellar mass. Careful inspection of the plain roentgenograms may reveal subtle calcification in some cases of meningioma and aneurysm. Suprasellar calcification can be seen in more than 85% of childhood craniopharyngiomas, but it is uncommon in the adult variety. If the Foster Kennedy syndrome is caused by an olfactory groove meningioma, anosmia ipsilateral with the optic atrophy also occurs.

The association of a spinal cord tumor and increased intracranial pressure is well known but occurs uncommonly. The mechanism is also poorly understood. When no intracranial reason for the papilledema can be found and before pseudotumor cerebri is accepted as the diagnosis, investigation for a spinal cord tumor should be considered. The usual lower extremity symptoms should dismiss serious consideration of pseudotumor cerebri. MRI with contrast of the lumbosacral region may show atrophy and widening of the interpedicular distance. This, then, suggests a more definitive evaluation by myelography. The cause of the papilledema is not necessarily mechanical obstruction of cerebrospinal fluid flow as has been shown by myelography. Since increased cerebrospinal fluid protein is a constant finding in these cases, the protein may obstruct the turnover of cerebrospinal fluid as occurs in the Guillain-Barre syndrome.

Brain Abscess

Brain abscess usually causes focal neurologic deficit, but occasionally it produces papilledema.

Juxtapapillary Choroiditis

A focal chorioretinitis next to the disc may be hard to see because of overlying inflammatory exudates. The focal nature of the changes suggests the diagnosis, since the rest of the nerve looks normal. Since juxta-papillary choroiditis most frequently occurs on the temporal side of the disc, it is unlikely to be papilledema, which occurs first on the nasal side.

Posterior Scleritis

Posterior scleritis, usually referred to as brawny scleritis, causes retinal edema with horizontal striae in the macula as well as low-grade disc edema. The best way to see the thickened choroid is with the fundus contact lens. Brawny scleritis is usually idiopathic, but it can be associated with thyroid disease.

Ocular Hypotension Secondary to Intraocular Operation

Cataract operation, even when it is uncomplicated and when the depth of the anterior chamber is normal, may be associated with a low intraocular pressure—in the range of 2 to 4 mm. The low pressure causes mild swelling of the disc and macula, with chronic loss of vision caused by macular disease. A dilated fundus examination using the indirect ophthalmoscope is necessary. A detailed view of the ciliary body may reveal ciliary body detachment, with secondary decrease in aqueous production. Seidel's test with fluorescein should be done, and the physician should look for a leak of the wound if an ob-vious filtering bleb is not present.

Ischemic Optic Neuropathy

TEMPORAL ARTERITIS (ARTERITIC). This condition is usually thought of as occurring in older people who show signs of headache and a temporal artery that is prominent, very tender, and noncompressible. The usual history is one of sudden loss of vision without warning or associated symptoms. If asked about any previous signs and symptoms, the patient may admit to them but dismiss them as "just old age" or "wearing out." Frequently, temporal arteritis causes disc edema, but it is of the pale and ischemic variety, with small vessels, rather than the plethoric type seen with increased intracranial pressure. The diagnosis of temporal arteritis should be considered in a patient over 55 years of age, particularly one over 65 years of age, when sudden loss of vision occurs in one or both eyes. Temporal arteritis has been reported and confirmed by biopsy in much younger people, but only rarely. The condition usually attacks one eye at a time, but since the other eye may be affected within days, a diagnosis should be made promptly, and therapy begun immediately. Temporal arteritis is a true ophthalmic emergency.

The physician should strongly suspect temporal arteritis whenever the blood sedimentation rate is elevated. The usual elevation is 45 mm or more, but even minimal elevations (in the range of 30 mm) warrant a temporal artery biopsy. In a positive biopsy, the typical multinucleated giant cells are present. If the condition is strongly suspected because of an elevated sedimentation rate, systemic steroid therapy should be started immediately, even if the biopsy cannot be done for as long as 48 hours. Such a brief course of steroid therapy does not affect the biopsy, and it may protect the other eye. Since temporal arteritis is a segmental disease, it is imperative to get serial sections done on the specimen because the pathologic area may be missed. It is important to get a positive biopsy early so that patients who do not require steroid therapy will not continue to receive it. Since they are in the age group that tolerates steroids poorly and is prone to such diseases as diabetes and hypertension, a positive biopsy also puts the treatment on a firmer basis. It has been suggested that doing a temporal artery arteriogram will show the occluded areas more precisely and thus increase chances of a positive biopsy. This has generally notworked out. When a sudden loss of vision with ischemic disc edema occurs, an important differential diagnosis is infarction of the nerve immediately behind the disc from emboli, particularly from an atheromatous condition of the carotid or aortic arch.

SMALL VESSEL OPTIC NEURITIS (ANTERIOR ISCHEMIC OPTIC NEUROPATHY) NONARTERITIC. Anterior ischemic optic neuropathy (AION) is associated with ischemic disc edema more often than is temporal arteritis. The loss of vision in patients with AION is gradual rather than cataclysmic; it tends to be a piecemeal loss of vision. In persons with AION, the other eye tends to be affected more consistently, although usually not simultaneously. AION is not associated with an increased sedimentation rate, and the temporal artery biopsy is negative.

The cause of this condition is considered to be small ciliary vessel occlusive disease, and the condition is not favorably affected by anticoagulant or steroid therapy. Although no effective specific therapy exists, associated conditions that decrease the vascular profusion ratio of the eye should be evaluated. These conditions are increased ocular pressure, decreased blood pressure, such as occurs in too sudden and too severe treatment for hypertension, and decreased carotid pressure owing to silent carotid occlusive disease, as evidenced by a decrease in ophthalmodynamometry.

ACUTE ANEMIA. Acute blood loss, such as occurs in gastrointestinal and uterine hemorrhages, does not commonly cause loss of vision or disc edema. When it does, the edema is of the pale ischemic variety, with attenuated vessels. About 25% of those who develop disc edema do so immediately, and the remainder develop it in the next few days or weeks. The loss of vision is usually unilateral, and it may be complete or partial or even present as a field defect, such as an attitudinal hemianopsia. The visual loss may be made worse by antecedent carotid occlusive disease or small vessel disease in the optic nerve or in the retina, which has already decreased the perfusion of the eye.

CHRONIC ANEMIA. Chronic anemia is also an infrequent but established cause of visual loss and disc edema. In the United States, it usually occurs in women who have begun a pregnancy with a low hemoglobin level and then compounded the problem with no prenatal care, thus making the hemoglobin level drop even lower. The edema is low grade and closer to the ischemic variety than the edema in increased intracranial pressure. The diagnosis is easily made by hemoglobin and hematocrit determinations. Whatever visual loss ensues can be made worse by an associated eclampsia or hypertension that causes further ischemia.

Idiopathic Intracranial Hypertension

The many causes of intracranial hypertension all have serious consequences for the visual system. At some point in the course of the disease, intracranial hypertension may require specific and aggressive treatment (e.g., surgery, shunting, or optic nerve decompression) to prevent those serious visual consequences. One such disease process that requires cautious and prolonged observations is idiopathic intracranial hypertension, also called pseudotumor cerebri. Despite its name, this disease can be anything but benign.

PATHOLOGY

Increased intracranial pressure results from only a limited combination of factors: an increase in cerebral mass, an increase in vascular volume, or an increase in fluid in the subarachnoid space. Sahs and Joynt did brain biopsies on 10 patients and found an increase in intracellular edema. Other investigators have identified the microvasculature as the source of the problem with secondary tissue swelling. The role of increased fluid in the subarachnoid space was suggested by Bercaw and Greer. They injected 131T RISA in two patients and found a decrease in absorption from the spinal fluid compartment into the intravascular compartment. In view of the varied disease processes that have been associated with idiopathic intracranial hypertension, there may well not be one underlying pathologic picture for this disease.

ETIOLOGY

The disease initially called serous meningitis by Quicke and now referred to as idiopathic intracranial hypertension has many different associations with a varied group of disease processes that do not appear to have anything in common. It has been repeatedly reported in patients taking vitamin A, tetracycline, nalidixic acid, and penicillin. There is also an association in patients with plumbism, carbon dioxide retention, hypoparathyroidism, and lupus erythematosus. The disease is seen most commonly in obese young females with menstrual irregularities and in the first trimester of pregnancy. At one time it was also commonly seen in female patients on the pill, but this is a rare association now. Idiopathic intracranial hypertension is also seen as a consequence of cerebral sinus thrombosis either spontaneously, secondary to mastoid disease, or postpartum. Unless specific invasive diagnostic tests are performed, this particular finding is only inferential depending on the clinical setting (e.g., mastoid disease or post-partum). These patients have one symptom that may help in the diagnosis. In the presence of the venous flow disturbance in cerebral sinus thrombosis, these patients hear a noise; it is not a bruit, but rather is called a venous souffle. This noise cannot be heard by the physician with a stethoscope. It is only heard by patients and not all the time. Usually they will hear it when the surrounding environment is quiet. They report it as a blowing sound or whisper rather than the loud roaring sound of a bruit. It may even be dampened or enhanced depending on which side they are lying. As a result of this variability and apparent inconstancy, patients may not mention this symptom, and the astute clinical historian must seek it. The dural sinus thrombosis is best demonstrated by MRI (Fig. 2.7, A and B).

fig. 2.7a
fig. 2.7b

Figure 2.7.
A and B. Case of pseudotumor cerebri secondary to multiple sinus thrombosis.

The association of pseudotumor cerebri with vitamin A toxicity is not usually seen in adults. I have seen it in one 19-year-old girl who chronically ingested an excess of vitamin A to treat her acne. Vitamin, A toxicity can be acute or chronic. The acute variety occurs when the patient ingests food with a high vitamin A content such as polar bear meat or shark liver. The toxicity is manifested by headache, nausea and vomiting, a decreased sensorium, and irritability. Acute toxicity in children may be caused by an accidental overdose of vitamins that the infant had access to. Chronic intoxication is a more common presentation with the signs and symptoms of idiopathic intracranial hypertension.

Hydrocephalus and increased intracranial pressure have also occurred in vitamin A–deficient babies in association with other neurologic signs such as increased reflexes and a bulging fontanel. Administration of vitamin A in these patients quickly reverses the process. It is important to consider this entity in infants, who cannot speak and give a history.

DIAGNOSIS

The usual criteria for establishing the diagnosis of pseudotumor cerebri are signs of increased intracranial pressure confirmed by lumbar puncture. The spinal fluid, except for Increased pressure, should be entirely normal or show a slight decrease in spinal fluid proteins, a finding that has been reported in as many as 70% of cases. The ventricles are of normal size or small. In the past, invasive studies such as a pneumoencephalogram were required to demonstrate ventricular size. Now the CT scan has replaced the pneumoencephalogram. In the absence of neurologic signs and before the advent of CT examinations, the possibility of a posterior fossa tumor made lumbar spinal taps dangerous in the face of increased intracranlal pressure. However, a CT examination can rule out a posterior fossa tumor or aqueduct stenosis with secondary enlargement of the ventricles. This allows a safe spinal tap from below to establish the diagnosis of pseudotumor cerebri.

A negative neurologic examination is also essential except for signs and symptoms secondary to the increased intracranial pressure (e.g., sixth-nerve paresis, headache, and transient loss of vision). The headache is generalized, nonlocalizing, and made worse by increasing the intracranial pressure such as during a Valsalva maneuver. Headache is usually present in benign intracranial hypertension and frequently is the reason patients seek medical consultation. However, headache is not always present despite the increased intracranial pressure and may come and go despite constant increased intracranial pressure. The lack of or cessation of a headache, therefore, does not always mean a decrease in intracranial pressure and is not a reason for complacency. It is during the neurologic examination that papilledema is discovered and the rest of the diagnosis is considered.
Another type of pain less commonly seen is facial pain or paresthesia. The mechanism for this is not known. One theory is that a swollen brain with displacement causes trigeminal nerve stretching over the petrous bone or compression of the nerve root at the petrous apex as it is about to enter the trigeminal cistern and become the gasserian ganglion. Macular pigmentary changes have been reported in papilledema secondary to pseudotumor cerebri. The reason for these pigmentary changes is probably secondary to retinal edema.

The diagnosis of pseudotumor cerebri usually is suggested by a finding of papilledema corroborated by increased spinal fluid pressure on a spinal tap. Although these two findings would seem interchangeable—if you have one, you have the other—this does not hold in all cases. Many reports indicate that in idiopathic intracranial hypertension, there is wide fluctuation in intracranial pressure; thus, at any given moment, a tap may show normal, borderline, or elevated pressure. For example, in one series of patients whose spinal fluid pressure was monitored over 24 hours, the pressure
ranged from 186 to 520 mm of spinal fluid. A low tap in the face of papilledema creates a diagnostic dilemma; an elevated spinal fluid tap in the absence of papilledema is equally confusing. Both situations can exist and severely test the acumen of the most astute physician.

The situation of increased intracranial pressure without papilledema is particularly important in judging when the course of idiopathic intracranial hypertension is over. Even after the papilledema disappears, severe visual consequences may occur if the intracranial pressure is still elevated or the idiopathic intracranial hypertension recurs without the production of papilledema.

Pseudotumor that occurs in the young pediatric group differs from cases we see in teenagers and older persons. A review of Lessell's cases revealed no female sex predilection, nor was obesity a factor. The usual presentation in teens and older patients is headache. In the pediatric group, changes in personality like apathy, somnolence, irritability, dizziness, and ataxia were the usual presenting signs. In this group the fontanels are frequently open, and the sutures are not set; as a result papilledema is infrequent.

PROGNOSIS

Visual loss with this disease is quite com-mon. In several groups of patients, up to 49% have had some field or acuity loss. The problem has been to establish what factors predict those patients at risk for visual loss. Several decades ago, Walter Dandy, the famous neurosurgeon, had four criteria—all visual—for surgical intervention in this disease: decreasing visual acuity, progressive contraction of the field, gliosis of the disc, and increasing transient obscurations. These criteria are still valid today. My own experience and the reports by Corbett et al., by Orcutt, Page, and Sanders, and by Wall, Hart, and Burde provide additional information about prognostic factors in benign intracranial hypertension.

The degree of edema does not reflect the degree of the increased intracranial pressure. Therefore, we cannot assume that a minor amount of edema is less serious than 4 diopters of papilledema. Neither does the duration of the papilledema predict the final visual result. Visual loss can occur late or early in the course of the disease, although the amount of visual loss does increase with the duration of the disease. However, this finding is of little help in the management of an individual case. In more chronic cases, peripapillary subretinal hemorrhage sec-ondary to neovascularization occurs and is a bad prognostic sign for visual loss. Macular stars do not portend visual loss but only substantiate the chronicity of the process. Anemia of a significant degree appears to affect visual loss. There is diverse opinion about the significance of vascular hypertension. However, a combination of anemia and hypertension may increase the chances of visual loss because of the increased ischemic effect of the two together. High myopia appears to increase the patient's prognosis for visual loss.

TREATMENT

Many patients with idiopathic intracranial hypertension have mild symptoms and do not require treatment. However, they need to be followed just as closely as those who have severe complaints, because of possible visual system deficits. Repeated spinal fluid taps have been advocated but are not very pleasant for the patient. Since the spinal fluid pressure usually restores itself to the previous level in about 2 hours, I am not convinced of the rationale for its use in a chronic disease. There is also the risk of infection with multiple taps. Repeated taps may cause tears in the dura, with chronic leaking of spinal fluid and perhaps worsening of the headache.

The use of carbonic anhydrase inhibitors such as acetazolamide decreases the production of cerebral spinal fluid just as they reduce aqueous production in the eye. An intervenous bolus of 1 g has been shown to decrease cerebral spinal fluid secretion for 2 hours. The usual maximum dosage recommended by the manufacturers is far below what has been shown to be effective in reducing intracranial pressure, which has been projected at 4 g/day. Side effects at this dosage level or even less include gastrointestinal symptoms, disturbances in acid-base balance, and perioral and digital pares-thesias. Methazolamide theoretically may be preferable to acetazolamide because it crosses the blood-brain barrier better than acetazolamide. No studies have been performed to compare the two drugs. Diuretics in classes other than carbonic anhydrase inhibitors do not work as well.

Since Diamox belongs to the sulfonamide family, agranulocytopenia can occur, although rarely. It has also been reported to be teratogenic in pregnant females. However there are only two cases of this in the literature, and it appears to be a safe drug after the 20th week of pregnancy. Another feature of chronic use is the production of metabolic acidosis. This can predispose to calcium oxalate deposition and renal stones. However, furosemide has been reported as a fair substitute. I cannot speak from personal experience. An uncontrolled study also sug-gests chlorthalidone as another substitute.

Steroids are another therapeutic possibility. Steroids in themselves have serious side effects and have been implicated in causing benign intracranial hypertension in association with the nephrotic syndrome. Most physicians treating benign intracranial hypertension recommend only a short course of steroid treatment, usually lasting no more than several weeks.

If the disease process does not abate and the medical treatment is not effective in stopping visual loss, then surgical intervention must be considered. The surgical treatment falls into two groups. The first is the lumboperitoneal shunt, which has the advantage of rapidly normalizing the intracranial pressure and reducing the papilledema. Although any competent neurosurgeon can do this surgery, the operation, like all operations, is not perfect. The shunt may fail with return of increased intracranial pressure; at the other extreme, it may filter excessively and lead to increased headache due to shifting of the intracranial contents and stretching of the nerves.

The second surgical choice is an optic nerve decompression (Fig. 2.8). This technique has been effective in reversing visual loss from increased intracranial pressure, although the exact mechanism of its effect is not well understood. Some workers contend that opening up the optic nerve sheath reduces pressure in the nerve and allows for better vascular profusion of the nerve. Others contend that the dural window in the optic nerve sheath acts as a draining point for cerebrospinal fluid and, therefore, helps reduce the intracranial pressure. The report of Kaye, Galbraith, and King on a 51-year-old female with a 14-month history of papilledema and pseudotumor cerebri addresses this controversy. Hayreh's fenestration experiments revealed fibrous adhesions to the nerve as a late finding. This scarring appears to shift the pressure away from the low pressure vascular system at the laminar cribrosa. This would explain the ipsilateral eye but not cases with contralateral improvement from unilateral fenestration. However, multiple explanations may be needed to explain all the cases. Because of worsening symptoms, increasing papilledema, and increasing transient obscurations, bilateral optic nerve sheath decompression was performed. Intracranial pressure was measured continuously postoperatively, and no significant lowering of the intracranial pressure was recorded. However, the papilledema and symptoms decreased, and the patient was normal 2 months postoperatively. Therefore, optic nerve sheath decompression appears to preserve optic nerve function but does not apparently treat the underlying cause of the increased intracranial pressure by draining the subarachnoid fluid. The treatment of increased intracranial pressure is discussed further below.

The surgical procedure is fairly standard, with some small individual variations that each surgeon has learned from experience.

fig. 2.8

Figure 2.8.
A. Conjunctiva peritomy over medial rectus muscle. 6-0 Vicryl suture in medial rectus muscle insertion in reflected medial rectus. B. Hole cut in optic nerve sheath with Beaver surgical blade M.V.R., Unitome 5560. Incision extended with Beaver sickeledge blade. C. Optic nerve sheath window is produced that allows the egress of fluid. (From Walsh TJ. Papilledema. In: Roy FH, Master Techniques in Ophthalmic Surgery. Baltimore: Williams & Wilkins, 1995:825.)

There is no preoperative pupil dilatation, since intraoperative monitoring of pupil function is vital for surgical safety. Some surgeons prefer local, and others like myself prefer general anesthesia. Local anesthesia may interfere with pupil functions, and there is always the problem of a retrobulbar hemorrhage, which could make a marginally functioning nerve worse as well as postpone surgery beyond an optimal time. The degree of globe manipulation and compression of orbital contents are easier under general anesthesia. However, the disadvantage of general anesthesia is that too much compression can be used in an attempt to increase visualization. To reduce orbital pressure the patient is placed in slight reverse Trendelenburg position. I do this for cataract surgery as well. The anesthesiologist must be told to not let the patients blood pressure drop at all during the procedure. A drop in blood pressure may add to any lack of nerve perfusion from the previous problem and the operative manipulations.

A medial orbital approach is used to facilitate the temporal retraction of the globe. A generous lateral canthotomy is preferred. A wire speculum is used because it creates less pressure on the orbital contents. The larger blade-type speculum can force the lids wider apart but may create more orbital pressure. Pupillary size must be monitored during the entire procedure. If the pupil dilates more than 2 mm, relax all pressure points. A conjunctival peritomy is then performed beginning 4 mm from the limbus over the medial rectus muscle'. It is impor-tant to start the peritomy 4 mm back rather than at the limbus so the conjunctival repair at the end of the procedure can be tight and nonleaking. The peritomy extends from over the medial rectus to beyond the superior and inferior rectus 'muscles. The medial rectus is now isolated as in any standard disinsertion of the muscle with 6-0 Vicryl sutures placed in the lateral aspects of the muscle in a locking configuration. The superior and inferior rectus muscles are isolated, and 4-0 silk sutures are used as traction sutures. A 6-0 Vicryl suture is inserted in the scleral stump of the medial rectus muscle insertion in a baseball-type stitch. Be sure it encompasses the entire stump; any asymmetric attachment may cause torsion of the globe and make the nerve harder to visualize. At this point, bring in the microscope and focus it in the most advantageous position for observation. As you go deeper into the orbit, look for the ridge on the sclera that identifies the long ciliary artery. Use this as a landmark and keep it in the center of the field. The conjunctiva and tenons capsule are now dissected up by blunt dissection to reduce bleeding. Keep the dissection between the cortex veins. Farther on, you encounter orbital fat, and this is retracted by either a small blunt malleable retractor or a cotton-tip applicator. When the optic nerve is isolated, gently displace the posterior ciliary artery to prevent injuring it. Locate an avas-cular area on the nerve. Also locate a dilated area which is most likely to have a fluid level between the sheath and optic nerve. Pick up the sheath with fine neurosurgical microforceps. Cut a hole in the sheath using a Beaver surgical blade M.V.R. Unitome 5560. Then extend the incision with a Beaver sickeledge blade. This blade is easier to use than scissors because of the limited space. As you cut dura, some of the arachnoid can be seen and needs to be incised to release the perineural fluid. Don't incise the pia on the nerve. Any bleeding is usually slight and handled by tamponade. At this point some surgeons prefer multiple longitudinal slits and others a window as generous as surgically possible. I prefer the window technique. A Fisher tenotomy hook is moved carefully without pressure longitudinally along the nerve to free up any adhesions. At this point, if there is no bleeding, then reinsert the medial rectus muscle and remove the sutures on the vertical recti. The conjunctiva is then closed watertight with 6-0 plain catgut. Antibiotic ointment and a nonpressure dressing is applied.

The patient should be relatively quiet for 24 hours to reduce chances of bleeding in the orbit or sheath, which can compromise optic nerve function and or the surgical result. The most serious complication of this procedure is further damage to the optic nerve. Diplopia and pupillary abnormalities have also been noted but appear to be more common in the lateral surgical approach.

Carotid Cavernous Sinus Fistula

Among younger patients, carotid cavernous sinus fistula is more often seen in men and after trauma. Among older patients, it is more often seen in women and secondary to arteriosclerotic rupture of an in-tracavernous aneurysm. The increased venous flow to the eye, as well as the increased venous pressure, may cause only edema of the disc and fullness of the retinal veins without dilated veins on the conjunctiva, sclera, and lids. If the fistula is present long enough, the edema may become bilateral. Rarely, disc edema may even begin in the contralateral eye if a superior ophthalmic vein thrombosis occurs ipsilateral with the fistula. The associated signs of ocular bruits and ophthalmoplegia should be evaluated.

Pulsations, unless marked, may be missed. They are best seen by looking at the eye from the side rather than straight ahead. The more subtle pulsations are diagnosed when the physician uses direct ophthalmoscopy, noting that the fundus is going in and out of focus synchronously with the pulse at the wrist. If the applanation technique is used, the tonometer sign may be missed. The variation of the tonometer reading may be interpreted as unsteadiness of the patient in the headrest of the slit lamp. With the Schiotz tonometer, however, the arm has wide rhythmic swings in the range of six scale readings rather than the usual two to three scale readings.

Peripheral Ocular Disease

Peripheral uveitis or pars planitis may cause a vitreitis that, in turn, causes disc edema and macular edema. Examination of the far periphery of the fundus with the indirect ophthalmoscope is indispensable. Fundus contact lens examination of the vitreous humor reveals cells. The cellular reaction is more generalized than that seen in papillitis located just in front of the disc.

Unilateral Neck Dissection and Lung Disease

In radical neck dissection, a procedure for extensive carcinoma, the possibility that a particular dissection is incomplete with later metastasis to the brain is of real concern. If the patient later has a mild disc edema and engorged veins, the question of cerebral metastasis with increased intracranial pressure is raised. The physician may not consider the possibility of decreased venous drainage from the head and presume that the other jugular system is able to drain the head adequately. The other system is not always competent, however, and disc edema may result.

The theory behind ligation of the internal jugular vein or in removing it totally in a radical neck dissection is that the rich collateral venous system draining the head will compensate. These collaterals include the orbital, occipital, pharyngeal, pterygoid, and emissary venous systems, to name only a few. However, these systems may not always work adequately on demand. They may also work to different degrees. For instance, left jugular compression usually causes a more pronounced rise in cerebral spinal fluid pressure than does right jugular compression. This type of response probably explains the increase in intracranial pressure that follows radial neck dissections and the increased cerebral venous pressure from chronic chest pathology.

With such patients, the usual studies—skull roentgenograms, brain scan, CT, MRI, neurologic examination, complete ophthalmologic examination including field examination—must be performed. If the other signs of increased intracranial pressure are present, contrast studies must be considered. Disc edema caused by severe pulmonary disease, such as emphysema, can also be seen. It may be caused by decreased venous drainage from the head into the chest, or it may be secondary to an increase in blood Pco2.

Chronic lung disease is a well-known cause of increased intracranial pressure. Despite the large numbers of people whom we see with various grades of chronic obstructive pulmonary disease (COPD), the occurrence of papilledema is rare. The cause is believed to be the increased CO2 that results from the COPD. Kety showed that by raising the level of CO2 in the blood, secondary vascular dilatation occurs, resulting in increased intracranial pressure. The secondary anoxia these patients suffer over a long period rarely causes optic nerve ischemia and decreased vision. If another complicating factor occurs, such as a reduction in optic nerve perfusion pressure, then decrease in vision can occur. The chronic anoxia increases erythropoiesis, and a secondary type of polycythemia occurs. This hyperviscosity of the blood may cause sludging and vascular congestion at the nerve head, with the appearance of papilledema. The increased volume of the blood also causes an increase in the intravascular space in the cranial vault, further increasing the intracranial pressure.

Papilledema can also occur with other causes of respiratory compromise such as the Pickwickian syndrome.






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