Diagnostics

Acute Blindness

RICHARD L. GORMAN, MD, BRIAN AHLSTROM, MD,

Complaints that concern the eye, such as conjuncti- vitis, cornea1 abrasions, or foreign bodies, are common in the emergency department. More serious but less frequent complaints such as loss of visual acuity or intense eye pain raise the level of concern of the emergency physician. To overlook a potentially correctable cause of life-long reduction in visual acuity is one of the more serious errors an emergency physician can commit. Acute non-traumatic acquired blindness demands immediate attention to both the differential diagnosis and appropriate diagnostic workup. A recent case in the emergency department of an adolescent female with acute non-traumatic ac- quired blindness is presented.

CASEREPORTHISTORY

An 18-year-old woman presented to the emergency de- partment, three-weeks post par-turn, with a chief complaint of progressive blurring of vision since delivery. The preg- nancy and spontaneous vaginal delivery had been uncompli- cated. Less than a week after discharge from the hospital, the patient began experiencing blurred vision, with the left eye being more affected than the right. She complained of stumbling into walls and seeing only shapes with faint colors. The patient denied diplopia, photophobia, did not wear corrective lenses, and had no prior history of visual disturbances. Her appetite and activity level were un- changed. She admitted smoking cigarettes and marijuana, but other drug use was denied. There was no history of head or neck trauma, nausea, vomiting, syncope, seizures, changes in mental status, or hypertension. Past medical his- tory was remarkable for occasional occipital headaches, which were not associated with aura, nausea, vomiting, or

From the Department of Pediatrics, University of Maryland

School of Medicine, Baltimore.

Manuscript received January 17, 1988; accepted February 1,

1986.

Address reprint requests to Dr. Gorman: University of Maryland Hospital, N5E12, 22 S. Greene St., Baltimore, MD 21201.

Key Words: Acute blindness, craniopharyngioma, emergency care, visual acuity.

0735-6757186 $00.00 + .25

DAWN KOBRIN-MERRITTS, MD

visual changes, and which resolved spontaneously with rest. Family history was negative for migraine, seizures, brain tumors, diabetes, sickle-cell hemoglobinopathy, or heart, kidney, or liver disease. Prior to the patient’s three week course of progressive visual loss, she had been in good health.

Physical examination revealed an 18-year-old black fe- male who was well-developed, well-nourished, and in no ap- parent distress. She was alert and oriented to time, place, and person; memory was intact. Vital signs revealed a tem- perature of 37°C a pulse rate 70/min, a respiratory rate of 18/min, and a blood pressure of 108/68 mm Hg. The head was normocephalic and atraumatic. Pupils were 7 mm in size, equal, round, and slow but equal in their reaction to light and accommodation. Extraocular movements were in- tact and conjugate. The conjunctivae were pink, and the sclerae were non-icteric. Fundi were flat, and the disk margins were sharp. Visual perception was limited to light and color in the right eye and perception of motion in the left eye. The tympanic membranes were unremarkable. The nares were patent without discharge, and the throat was normal. Teeth showed good dental hygiene. The neck was supple with negative Kernig and Brudzinski sign, and the thyroid gland was not enlarged. No carotid bruit was ap- preciated. Lungs were clear. Cardiac examination revealed a regular rate and rhythm without murmur and good periph- eral pulses. Breast examination showed no masses or en- gorgement. The abdomen was soft with bowel sounds present. Genital examination revealed Tanner stage 5 pubic hair. There were no neurocutaneous stigmata or rashes. Ex- tremities were without cyanosis, clubbing, or edema.

The neurological examination revealed the patient to be alert and oriented to time, place, and person. Her memory was intact. Cranial nerves 3 through 12 were intact, with the examination of cranial nerve 2 as previously described. The motor examination revealed equal power and tone. Sensory examination results were intact to pinprick, position, vibra- tion, and fine touch.

Deep tendon reflexes were equal and symmetric with flexor plantar response. Clonus was not present. Heel to shin movement was fluid. Finger to nose movement demon- strated past pointing. The gait was narrow-based with the patient able to balance with minimal unsteadiness. On am- bulation, she collided with the wall. She was unable to walk heel to toe in any straight line fashion, usually leaning to the left. Results of the Romberg were negative.

Admission laboratory work revealed a hemoglobin of 15.6

459

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GORMAN ET AL W ACUTE BLINDNESS

g/d& a hematocrit of 45.1%, a leukocyte count of 5,400/mm3, and platelet count of 306,000/mm3. Electrolytes were: Na, 142 mEq/l; Cl, 111 mEq/l; K, 4.2 mEq/l; Cot, 22 mEqf1, blood urea nitrogen (BUN), 10 mg/dl; and glucose, 74 mg/dl. Urinalysis results were normal. Toxicology screen was nega- tive. Computerized tomography (CT) of the head showed a large calcium-containing suprasellar tumor markedly en- hanced with contrast. The patient was admitted to the hos- pital.

DISCUSSION

Despite the urgency and high emotional impact of a patient with sudden blindness, only one recent journal article and one book have been written on this sub- ject.‘,*

This provided the motivation to research and present an approach to acute blindness. A list of the causes of acute or acquired blindness is presented in Table 1.3-26 The mere provision of a list, while helpful, does not address the physician’s concern of an appro- priate scheme for the approach to this medically ur- gent issue.

This patient presented with progressive visual loss. The differential diagnosis of blindness can be ap- proached in several ways. The neurological approach is one logical method. First, the lesion is localized by careful neurological examination, and then other ele- ments of the history and physical examination are used to determine etiology and appropriate diagnostic tests. As the visual pathway is traced from the cornea to the occipital lobe, clinical and historical evidence are used to guide the differential diagnosis. For the purpose of this case discussion, the visual pathway will be broken down into four parts: the eye, the optic. nerve, the chiasm, and post-chiasm. This patient’s age allows consideration of both pediatric and adult patho- logical processes.

The most common causes of acute visual loss are related to the eye itself. Penlight examination will re- veal lesions of the cornea, anterior chamber, and lens. Pain and foreign body sensation are common in keta- titis. “Steaminess” of the cornea is sometimes seen in acute closed-angle glaucoma. The meniscus of blood that is diagnostic of hyphema need only be seen for diagnosis to be made. Even small cataracts in the lens can cause significant visual loss if they impinge on the visual axis. Examination of the posterior chamber and retina require an ophthalmoscope. Lesions such as retinoblastoma, vitreous hemorrhage, retinal detach- ment, or thrombosis of the retinal vessel can be de- tected. Inflammation of the organ of sight, such as choroiditis, retinitis, and uveitis, are also easily diag- nosed in the emergency department. Hereditary dis- eases, such as retinitis pigmentosa or Refsum’s dis- ease, usually present in later life and can be diagnosed by careful inspection of the retina. Optic neuritis fre-

quently mimics papilledema on fundoscopy, but early papilledema is not commonly associated with visual loss. If papilledema is left untreated, it may lead to optic atrophy and profound irreversible loss of sight.

The clinician next evaluates the optic nerve as a site of pathology. Unilateral disease is the rule in primary optic nerve pathology. A patient may have long- standing visual impairment in one eye, which has been tolerated or ignored, and then presents with a second lesion on the previously healthy side producing a clin- ical picture that masquerades as acute bilateral dis- ease. Toxic agents and systemic disease can affect both nerves at once.

Of the primary tumors of the optic nerve, optic glioma is most common in the first decade of life. Compression of the optic nerve by meningioma, neu- rofibroma, or other extrinsic tumor is generally en- countered in older age groups. Proptosis is a com- monly associated sign of an extrinsic tumor or mass located within the orbital cavity.

The Marcus-Gunn pupillary reaction, also known as the swinging flashlight sign, is useful in the assess- ment of optic nerve diseases. When shining the light into the normal fundus, the “central integrator” in the Edinger-Westphal nucleus sends out bilateral pu- pillary constricting messages. When the same inten- sity light strikes on the damaged fundus, a weaker signal is generated. Thus, in rapid alternation from a healthy to diseased eye, the pupil will paradoxically continue to dilate while a light is shining into the “weak” eye.

Systemic diseases or toxins also affect the optic nerve. Toxins implicated in acute blindness include methanol, isoniazid, thallium, sulfa drugs, and ste- roids. Vascular thrombosis causing ischemic or anoxic optic neuropathy should trigger a search for cardiac abnormalities, atherosclerosis, or hemoglobinopathy. Transient visual loss or amaurosis fugax, is suggestive of organic disease secondary to embolization.

Optic neuritis, known for its high association with multiple sclerosis, can usually be suspected by painful eye movement and papillitis. In cases with a normal- appearing fundus, optic neuritis can be detected by a color desaturation test. This test is performed by comparing the perceived intensity of a red target from one eye to the other. Without signs of involvement of other parts of the central nervous system, it is impos- sible to conclude whether an episode of acute optic neuritis is an isolated parainfectious process or the first sign of a demyelinating disease. Follow-up studies of acute optic neuritis have found the inci- dence of multiple sclerosis to be between 10 and 60%.

Chiasmal lesions classically present with bitemporal hemianopsia. However, there is no simple relationship between field defect and visual acuity. The chiasm may be compressed by a pituitary tumor expanding

461

AMERICAN JOURNAL OF EMERGENCY MEDICINE W Volume 4, Number 5 m September 1986

upward or a craniopharyngioma expanding down- ward. Pregnancy causes physiological enlargement of the pituitary gland, and the temporal succession of giving birth and visual loss suggests postpartum pitui- tary apoplexy, or Sheehan’s Syndrome, although the absence of mental status changes and endocrine symptoms argue against this diagnosis.

The post-chiasmal pathway produces lesions of ho- momynous hemianopsia, which are increasingly con- gruent as one proceeds to the occipital pole. Temporal fossa tumors, abscesses, and arterio-venous malfor- mations may present as post-chiasmal blindness. Post-surgical blindness occurs after procedures that involve the occipital cortex or post chiasmic path- ways (e.g., middle ear surgery).

Cortical blindness is produced by lesions of the pri- mary visual cortex in the occipital lobe. This can be encountered in the post-concussion syndrome, the post-ictal period, and in basilar artery migraine. A permanent visual loss results from bilateral cerebral infarcts, hypotensive or hypoxic episodes, and post- herniation syndromes.

The mental status of the patient presenting with acute blindness must also be considered. When one encounters a patient with dramatic complaints and/or the onset of symptoms in an emotionally charged cir- cumstance, hysterical blindness as a type of conver- sion reaction must be considered. Inappropriate de- nial of concern about symptoms (la belle indifference) also raises the suspicion of blindness as a hysterical symptom.

Anatomical localization of the lesion should be pos- sible in the majority of the patients on the basis of the neurological examination. Localization and the differ- ential diagnosis should lead to a rapid and complete diagnostic process for the most likely causes. If the eye is involved, a slit lamp examination and determi- nation of the intraocular pressure by a skilled ophthal- mologist is in order. If results of the eye examination are normal except for the visual acuity, an emergent CT scan of the head and orbits is necessary to deter- mine whether there is a surgically correctable lesion. If there is no mass lesion, the diagnostic workup should pursue the diagnosis suggested by the history and physical examination. In all cases, a toxicology screen that includes methyl alcohol should be under- taken,

In this patient, the chiasm seemed the most likely location. The finding of a calcified suprasellar mass in this patient explained her symptoms and virtually es- tablished the diagnosis of craniopharyngioma.

On the night of admission, an emergent angiogram demonstrated an avascular suprasellar mass. The pa- tient was readied for surgery and was taken to the operating room less than 12 hours after admission. Repeat visual examination before surgery revealed a

462

rapid progression to total blindness. Less than 11 hours after her initial examination, the patient was found to have light perception only in the right eye and be blind in the left eye. The patient underwent a right frontal craniotomy with resection of the supra- sellar tumor. After careful dissection, the tumor was found to the left of the right optic nerve with the tumor mass displacing the internal carotid artery laterally. The tumor was bulging from the space between the right optic nerve and the right internal carotid artery and to the left of the right optic nerve. Laser surgery as well as meticulous blunt and sharp dissection was used during the procedure. There was gross total re- moval of the tumor. Pathology revealed a tumor mass consisting of an irregular fragment of gray soft tissue measuring 0.4 x 0.3 x 0.2 cm. The histologic diag- noses were compatible with craniopharyngioma. Post- operatively, the patient was admitted to the neuro- surgical intensive care unit in guarded condition and recovered uneventfully with progressive improvement of her vision.

On post-operative day one, she had color and light perception in both eyes. On the second post-operative day, the patient could discern faces, figures, and dark details. On the third post-operative day, she was able to read large print. Subsequently, the patient’s vision improved, and the post-operative course was eventful only for a transient period of diabetes insipidus. Vi- sion improved to 20120 in both eyes one week after surgery with a significant bitemporal hemianopsia. She was discharged home to receive a course of out- patient radiation of 5,000 rads to the tumor bed.

A three-month follow-up examination revealed no sign of recurrent tumor by computerized tomography or physical examination. The bitemporal hemianopsia defect persists with visual acuity in both eyes 20/20.

Craniopharyngioma, resulting from embryonic squamous cell rests of Rathke’s pouch, account for 6- 10% of all brain tumors in children and 3% of adult brain tumors. Abnormal vision and signs of increased intracranial pressure are the presenting signs, with the visual symptoms being by far the most common. Cur- rent therapy for the crainiopharyngioma is complete surgical excision where feasible, followed by radiation therapy. Five-year survival rates have been reported as greater than 80%.

CONCLUSION

Acute visual loss or sudden blindness requires an emergent, well-directed diagnostic workup. The neu- rological approach to localize the lesion is a rapid, log- ical diagnostic modality. Patients should receive a CT scan of the skull and orbits if intracranial lesions are suspected to determine whether the lesion is surgi- cally correctable.

GORMAN ET AL n ACUTE BLINDNESS

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