Journal of Neuro-Ophthalmology, June 2000, Volume 20, Issue 2

Homonymous Visual Field Defects in Patients without Corresponding Structural Lesions on Neuroimaging

Homonymous visual field defects usually occur with structural processes affecting retrochiasmal visual pathways. The responsible lesion is usually evident on magnetic resonance imaging or on other neuroimaging studies. When results of neuroimaging are normal, functional illness is often suspected. The authors report four patients with homonymous visual field defects who presented with no evident corresponding lesion on magnetic resonance or computed tomography imaging. Etiologies for the visual field defects included the Heidenhain variant of Creutzfeldt-Jacob disease, degenerative dementia, subtle occipital ischemia demonstrated only on positron-emission tomography scanning, and nonketotic hyperglycemia. Clinicians should be aware of the alternative etiologies of organic homonymous visual field loss in patients with normal neuroimaging.

Journal of Neuro- Ophthalmology 20( 2): 92- 96, 2000. © 2000 Lippincott Williams & Wilkins, Inc., Philadelphia Homonymous Visual Field Defects in Patients Without Corresponding Structural Lesions on Neuroimaging Paul W. Brazis, MD, Andrew G. Lee, MD, Neil Graff- Radford, MD, Nayan P. Desai, MD, and Eric R. Eggenberger, DO Homonymous visual field defects usually occur with structural processes affecting retrochiasmal visual pathways. The respon­sible lesion is usually evident on magnetic resonance imaging or on other neuroimaging studies. When results of neuroimag­ing are normal, functional illness is often suspected. The au­thors report four patients with homonymous visual field defects who presented with no evident corresponding lesion on mag­netic resonance or computed tomography imaging. Etiologies for the visual field defects included the Heidenhain variant of Creutzfeldt- Jacob disease, degenerative dementia, subtle oc­cipital ischemia demonstrated only on positron- emission to­mography scanning, and nonketotic hyperglycemia. Clinicians should be aware of the alternative etiologies of organic hom­onymous visual field loss in patients with normal neuroimag­ing. Key Words: Heidenhain variant of Creutzfeldt- Jacob dis­ease- Homonymous hemianopia- Neuroimaging- Nonke­totic hyperglycemia. Homonymous visual field defects usually occur with structural processes affecting retrochiasmal visual path­ways. The responsible lesion is usually evident on mag­netic resonance imaging ( MRI) or on other neuroimaging studies. When results of the MRI are normal, physicians often consider functional illness to be the cause of the field impairment. We report four patients with homony­mous visual field defects who presented with no evident corresponding structural lesion on MRI or computed to­mography ( CT) imaging. All MRI examinations were performed with 5- mm thick sections ( 1- mm gap), with and without gadolinium. Manuscript received February 24, 1999; accepted March 23, 2000. From the Department of Neurology ( PWB, NRG), Mayo Clinic- Jacksonville, Jacksonville, Florida; the Departments of Ophthalmol­ogy, Neurology, and Neurosurgery ( AGL), Baylor College of Medi­cine, Houston, Texas; and the Center for Clinical Neurosciences and Ophthalmology ( NPD, ERE), Michigan State University, East Lansing, Michigan. Address correspondence and reprint requests to Paul W. Brazis, MD, c/ o Mayo Clinic- Jacksonville, 4500 San Pablo Road, Jacksonville, FL 32224. CASE REPORTS Case 1 A 63- year- old woman started noticing blind spots and impairment in her peripheral vision OU in November 1997. She had a history of multiple abdominal and pelvic surgeries and hypothyroidism, but she did not have oph­thalmologic or neurologic problems, except for recent depression and anxiety. Visual acuity in October 1997 was 20/ 20 OD and 20/ 25 OS, and automated perimetry ( Humphrey 30- 2) revealed a dense right homonymous hemianopia. An MRI of the head showed only nonspe­cific ( presumed ischemic) periventricular white- matter changes. Because of progressive and drastic visual dete­rioration, the patient was referred for neuro- ophthal-mologic evaluation. A neuro- ophthalmologic examination on November 5, 1997 revealed a visual acuity of 20/ 80 bilaterally. Pupils measured 4 mm bilaterally and were briskly reactive to light and near. There was no relative afferent pupillary defect. Kinetic visual fields on the Goldmann perimeter showed a dense right homonymous hemianopia that was more prominent superiorly, with some paracentral scoto­mas on the left. Motility examination revealed slow and inaccurate saccades and pursuit eye movements in all planes. Results of a funduscopic examination were nor­mal. Multiple laboratory studies, including serology for syphilis, vitamin B12, serum folate, sedimentation rate, and anti double- stranded DNA antibodies were normal. An electroencephalogram ( EEG) showed periodic dis­charges from the temporal lobe, which raised the possi­bility of Creutzfeldt- Jacob disease. The patient's vision declined, and there were associ­ated marked- mentation impairment and myoclonic jerk­ing of the extremities. The patient died approximately 3 months after the neuro- ophthalmologic examination, and results of the autopsy confirmed the spongiform enceph­alopathy of Creutzfeldt- Jacob disease. Case 2 A 75- year- old man with a history of progressive cog­nitive impairment for several years, attributed to a de- 92 HOMONYMOUS VISUAL FIELD DEFECTS 93 generative dementia ( thought to be Alzheimer disease), was referred on October 21, 1998 for visual impairment with a tendency to ignore objects in his left visual field. His medical history was significant for gastric ulcer and hypothyroidism. Neuro- ophthalmologic examination revealed a visual acuity of 20/ 40 bilaterally. Automated visual fields on the Humphrey perimeter showed a dense, complete, right homonymous hemianopia ( Fig. 1). Pupils measured 4 mm, were briskly reactive to light and near, and there was no relative afferent pupillary defect. Ocular motility showed slow saccades in all planes. Results of a slit- lamp examination revealed bilateral nuclear sclerotic cataracts consistent with 20/ 40 acuity. Results of a funduscopic examination were normal. An MRI of the head on October 21, 1998 showed severe diffuse cerebral atrophy with commensurate ven-triculomegaly. The atrophy was more prominent over the left than the right side of the brain, but no other structural lesion was evident. Case 3 A 63- year- old woman was referred for bilateral visual field loss and persistent stereotyped visual phenomena OU. She had a history of migraine headaches, asthma, several pelvic and abdominal surgeries, and iron defi­ciency anemia. She had no stroke risk factors, and family history was significant for migraine headaches. Approximately 2.5 months before evaluation, she noted the acute onset of yellow, black, and white circles OU in the central part of her vision. After a few minutes, these circles converted to black and white zigzag lines, and a blank spot was noted in her visual fields bilaterally. The visual phenomena persisted and was not associated with headache. Results of a neuro- ophthalmologic examination re­vealed visual acuity to be 20/ 20 bilaterally. Automated visual fields on the Humphrey perimeter showed a left inferior homonymous visual field defect ( Fig. 2). Pupils bilaterally measured 4 mm and were reactive to light and near with no relative afferent pupillary defect. Results of motility and slit- lamp examinations were normal. Results of funduscopy were normal. An MRI of the head showed no abnormalities. Be­cause of persistent problems, the patient underwent a positron- emission tomography ( PET) study of the brain, which revealed moderate decreased metabolism in the right primary visual cortex that was consistent with isch­emia. The infarction may have been related to her mi­graine. Case 4 A 75- year- old man reported a 1- week history of posi­tive visual phenomena, described as constant, colored, circular, whirring objects that occurred in both hemi-fields. This was associated with polyopia characterized by three or more vertical images seen monocularly or binocularly. There was no palinopia or perseveration of these multiple images in time. The patient's medical his­tory was significant for hypertension, congestive heart failure, and atrioventricular block ( status postpacemaker implant). Results of a neuro- ophthalmologic examination re­vealed a visual acuity 20/ 40 bilaterally. The polyopia did not resolve with the use of a pinhole. He did not recog­nize any Hardy- Rand- Rittler ( HRR) pseudoisochromatic color plates in either eye. Pupils measured 4 mm and were briskly reactive to light and near, and there was no relative afferent pupillary defect. Kinetic visual fields on the Goldmann perimeter revealed a complete left hom­onymous hemianopia and a right superior field defect ( Fig. 3A). Results of ocular motility and funduscopic examination were normal. Results of a general neurologic examination were nor­mal except for moderate short- term memory difficulty. Results of a CT scan of the brain were unremarkable ( an MRI was not performed because of his pacemaker). Laboratory studies revealed a serum glucose of 38.95 mmol/ L, a serum sodium of 120 mmol/ L, and a serum chloride of 85 mmol/ L. The patient was treated with intravenous insulin and fluids. By the next day, confrontation visual fields were normal. The positive visual phenomena and polyopia re­solved 2 days after presentation. An EEG performed on the third day after presentation revealed diffuse slowing without epileptiform activity. A neuro- ophthalmologic examination 1 week later re­vealed visual acuity 20/ 25 bilaterally. Kinetic visual fields on the Goldmann perimeter ( Fig. 3B) revealed complete resolution of the homonymous hemianopia, FIG. 1. Automated visual fields on the Hum­phrey perimeter revealing dense right mom-onymopus hemianopia ( patient 2). J Neuro- Ophthalmol, Vol. 20. No. 2, 2000 94 P. W. BRAZIS ET AL. THRESHOLD CRDTTONE K- 13- 98 FULL THRESHOLD FOVEA: 35 OS HO: - 1.85 OB 82- 13- 9 THRESHOLD CRBYTOHE FULL THRESHOLD • • FOVEA: 33 OB Ml: - 8.3G DB FIG. 2. Automated visual fields on the Hum­phrey perimeter ( patient 3). • * - : . ' • tt>. V,-' '. 87- 81- 98 FULL THRESHOLD FOVER: OFF HD: - 2.44 87- 81- 98 FULL THRESHOLD FOVER: OFF HO: - 1.68 DB IIP and the patient now identified 8.5 of 10 HRR plates on the right and 9 of 10 on the left. Cognitive function returned to normal. DISCUSSION These cases illustrate the clinical situations in which neuroimaging may be normal in a patient with an organic homonymous hemianopia ( Table 1). Homonymous hemianopia or cortical blindness may be an early or initial finding in some patients with the Heidenhain variant of Creutzfeldt- Jacob disease, and in most of these patients, results of MR or CT imaging are normal ( 1- 4). Diffusion- weighted MRI sequences may, however, demonstrate signal abnormalities in the cere­bral cortex or basal ganglia in some patients ( 5- 7). Re­sults of the EEG are often initially normal in these pa­tients, although it usually eventually shows characteristic - -* liin? FIG. 3. A: Initial kinetic visual fields on the Goldmann perimeter demonstrating complete left homonymous hemianopia and a right superior quadrantic constriction ( patient 4). B: One week later, kinetic visual fields on the Goldmann perimeter demonstrate total resolution of the visual field defect. J Neuro- Ophthalmol, Vol. 20, No. 2, 2000 HOMONYMOUS VISUAL FIELD DEFECTS 95 TABLE 1. Etiologies of homonymous hemianopias without correlative structural lesions on neuroimaging Heidenhain variant of Creutzfeldt- Jacob disease Degenerative dementias ( Alzheimer disease, Pick disease, Lewy body disease) Subtle occipital ischemia or hypoxia Nonketotic hyperglycemia Functional illness periodic complexes. Affected individuals soon also de­velop mentation impairment, myoclonus, and other signs of Creutzfeldt- Jacob disease, but initially, the diagnosis may be quite difficult and made only by brain biopsy. Our first patient presented with visual impairment and homonymous hemianopsia due to the Heidenhain variant of pathologically confirmed Creutzfeldt- Jacob disease. Some patients with Alzheimer disease or with other degenerative dementias ( e. g., Lewy body disease) may develop a homonymous field defect ( 8,9). Visual field defects may be difficult to demonstrate on perimetry be­cause of impaired mental status and difficult patient co­operation. Results of MRI may be normal or show only diffuse atrophy, and results of EEGs may be normal or show only mild diffuse slowing. This diagnosis is sus­pected in patients with a slowly progressive dementia without other focal neurologic findings, and the dementia usually far outweighs the visual field impairment. Our second patient has significant dementia, thought second­ary to Alzheimer disease, with MRI results showing dif­fuse atrophy that is more prominent in the left hemi­sphere than in the right hemisphere. This patient was found to have a dense right homonymous hemianopia. Most patients with visual field defects from cerebral infarction or hypoxia demonstrate ischemia on MRI of the brain. Our third patient, however, developed persis­tent blank spots and positive visual phenomena in her visual fields bilaterally and was found to have a left inferior scotomatous quadrantanopia. Results of MRI of the head were normal, but a PET scan of the brain re­vealed a small ischemic infarct in the occipital cortex. Similarly, Moster et al. ( 10) described two patients, one with bilateral, homonymous, congruous, hemianopic, central scotomata after carbon monoxide poisoning and the other patient with bilateral, congruous, inferior, vi­sual scotomata after global hypoxia, who were initially diagnosed with functional visual loss. Neither CT nor MR imaging adequately demonstrated the source of the visual dysfunction, but single- photon emission tomogra­phy ( SPECT) and PET imaging, respectively, confirmed the organic substrate of the visual impairment. Func­tional imaging techniques, such as SPECT or PET, or diffusion/ perfusion MRI should therefore be considered in patients with suspected cortical visual loss and normal results on CT or MR studies. Our third patient presented with positive visual phe­nomena associated with polyopia, mentation impairment, achromatopsia, and a dense visual field defect. Prompt treatment of his nonketotic hyperglycemia resulted in complete resolution of his subjective symptoms and a return of his visual fields, color vision, and mentation to normal. Results of a CT scan were normal. An MRI was not performed, but it is unlikely that results of such a study would have been abnormal. Although an EEG was not obtained during the patient's initial evaluation, it is possible that the patient experienced visual seizures in­duced by the nonketotic hyperglycemia, and that his tran­sient homonymous hemianopia was either an ictal phe­nomenon or a postictal inhibition, similar to a Todd phe­nomena. A small occipital infarct also could have been responsible for the presentation and cannot be com­pletely excluded. Harden et al. ( 11) described three patients with hyper­glycemia presenting with occipital seizures. In two of their patients, positive visual phenomena were associated with a homonymous hemianopia. In these two cases, similar to our cases, the visual phenomena and visual field defects cleared with treatment of the hyperglyce­mia, and results of CT scans did not show correlative abnormalities. Transient homonymous hemianopia in nonketotic hyperglycemia has been reported by other au­thors ( 12); however, perimetry was not performed in pre­viously reported cases. Therefore, nonketotic hypergly­cemia may present with positive visual phenomena as­sociated with a homonymous field defect and normal neuroimaging. Nonorganic hemianopia is associated with normal im­aging studies ( 13- 15). One method of determining if a field defect is nonorganic is to test saccadic eye move­ments into the supposedly absent portion of the field, with the patient assuming that eye movements and not the visual fields are being tested. Another method is to place a 30- prism diopter Fresnel prism into the upper quadrants of a trial frame ( 16). After visual fields are obtained without the prism, the prism is placed first base-out and then base- in, and with each change, the fields are repeated. Patients with pathologic hemianopsias shift their superior field 15 degrees to the right or to the left of the central vertical meridian with the prism base in or out, respectively, while patients with suspected func­tional hemifield defect do not shift their superior sectors in a similar fashion. In summary, although patients with a homonymous visual field defect and normal MRI results of the brain should be suspected of a nonorganic basis for the visual field loss, in the appropriate clinical setting, other disease processes, such as Creutzfeldt- Jacob disease, degenera­tive dementias, subtle cerebral ischemic or hypoxic le­sions, and nonketotic hyperglycemia, should also be con­sidered. Electroencephalography may be helpful in cases of possible Creutzfeldt- Jacob disease and nonketototic hyperglycemia. If the history is compatible with acute onset or ischemic disease, SPECT or PET imaging may help to demonstrate the structural brain injury. Clinicians should be aware of the alternative etiologies of organic homonymous visual field loss in patients with normal neuroimaging results. J Neuro- Ophlhalmol, Vol. 20, No. 2, 2000 P. W. BRAZIS ETAL. 7. REFERENCES Kovanen J, Erkinjuntii T, Ilivanainen M, et al. Cerebral MRI and CT imaging in Creutzfeldt- Jakob disease. J Comput Assist Tomogr 1985; 9: 125- 8. Purvin V, Bonnin J, Goodman J. Palinopsia as a presenting mani­festation of Creutzfeldt- Jacob disease. J Clin Neuroophthalmol 1989; 9: 242- 6. Aguglia U, Gambarelli D, Farnarier G, Quattrone A. Different susceptibilities of the geniculate and extrageniculate visual path­ways to human Creutzfeldt- Jacob disease ( a combined neurophysi-ological- neuropathological study). Etectroencephalogr Clin Neu-rophysiol 1991; 78: 413- 23. Vargas ME, Kupersmith MJ, Savino PJ, et al. 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