Interpreting the multifocal visual evoked potential: the effects of refractive errors, cataracts, and fixation errors.

AIM: To understand how refractive errors, cataracts, and fixation errors affect multifocal visual evoked potential (mfVEP) responses. METHODS: Monocular mfVEP responses were obtained using a pattern reversal dartboard display. For the control condition, visual acuity was corrected to > or =20/20 and foveal fixation was maintained. The right eye was tested under the following conditions: simulated refractive error, simulated cataract, steady eccentric fixation, and unsteady fixation. RESULTS: No subject demonstrated significant abnormalities under control conditions. For the simulated refractive error condition, significant centrally located abnormalities were seen for all subjects. For the simulated cataract condition, significant abnormalities were found for three subjects. The steady eccentric fixation condition yielded abnormalities in both eyes for all subjects while the unsteady fixation condition yielded significant central abnormalities in the tested eye. With eccentric and unsteady fixation conditions, all subjects had at least one sector with a waveform polarity reversal. CONCLUSIONS: While the mfVEP is a useful tool for identifying local optic nerve damage or ruling out non-organic aetiology of visual field defects, factors such as uncorrected refractive errors, cataract, eccentric fixation, and unsteady fixation can produce apparent field defects on the mfVEP. With care, these problems can be correctly identified.

Tracking the recovery of local optic nerve function after optic neuritis: a multifocal VEP study.

PURPOSE: To explore the multifocal visual evoked potential (mVEP) as a technique for tracking local optic nerve damage after unilateral optic neuritis (ON). METHODS: Humphrey visual fields and mVEP recordings were obtained from three patients within 7 days of an episode of ON. Patients were retested during the recovery phase, approximately 4 to 7 weeks later. The multi-input procedure of Sutter was used to obtain 60 local VEP responses (the mVEP) to a scaled checkerboard pattern. The mVEPs were recorded separately for monocular stimulation of both eyes. RESULTS: Initially, all three patients had extensive visual field defects, reduced visual acuity, and depressed mVEP amplitude in regions of poor visual field sensitivity. By 4 to 7 weeks, the fields recovered to near normal sensitivity in most locations, and visual acuity returned to 20/20. The mVEP recovered to nearly full amplitude in all regions, but substantial delays were present in many locations. The delayed responses were associated with regions of visual field loss documented during the acute phase. CONCLUSIONS: The mVEP can be used to track local optic nerve damage after unilateral ON. This technique should be useful in observing the effects of treatments as well as in testing hypotheses about the mechanisms underlying both the acute loss of vision and the subsequent recovery.

Functional bitemporal quadrantopia and the multifocal visual evoked potential.

Cases of functional bitemporal hemianopia rarely have been reported. The authors describe the case of a patient with dense bilateral inferotemporal quadrantic field defects on a functional basis that was confirmed by multifocal visual evoked potential. The normality of the multifocal visual evoked potential provides evidence of the functional basis of the field defects.

An attempt to detect glaucomatous damage to the inner retina with the multifocal ERG.

PURPOSE: To detect glaucomatous damage to the inner retina using the multifocal electroretinogram (mERG). METHODS: The stimulus array consisted of 103 hexagons with a mean luminance of 100 cd/m2 and a contrast of 50%. The mERG was recorded from 13 control subjects, 18 patients with open-angle glaucoma (OAG), 4 glaucoma suspects, and one patient with ischemic optic neuropathy (ION). Individual responses, as well as responses summed within quadrants or across the entire array, were measured in a number of ways. Humphrey visual fields were obtained for all patients, and the mean total deviation (MD) values for the 18 patients with OAG ranged from -2.2 to -18.2 with a mean (SD) of -7.3 (4.5). RESULTS: The mERG measure that best discriminated between the patients and the control subjects was the ratio of the amplitude at 8 msec after the peak response to the amplitude at the peak. Although the value of this ratio fell below the median of the control group for 16 of the 18 OAG patients, only 6 of these patients had ratios that fell below the normal range. Other measures of first- and second-order kernels did not do as well. Both within and across patients, the correlation between local field loss and the mERG ratio measure was poor. Furthermore, although in some patients the mERG waveform is clearly different from normal, in other patients (including the patient with ION) the waveform approximates the normal even in visual field areas with substantial sensitivity loss. CONCLUSIONS: Because glaucomatous damage is known to affect the ganglion cell axon, these data suggest that damage to ganglion cell axons is not a sufficient condition to produce changes in the mERG as measured here and that in patients with clear changes in mERG waveforms, these changes do not appear to be well localized and local waveforms are poorly correlated with local changes in field sensitivity.

An interocular comparison of the multifocal VEP: a possible technique for detecting local damage to the optic nerve.

PURPOSE: To develop a quantitative measure of local damage to the ganglion cells/optic nerve based on an interocular comparison of multifocal visual evoked potentials (mVEP). METHODS: Multifocal VEPs were recorded from both eyes of six normal subjects and four patients; each eye was stimulated separately. Two of the patients had glaucoma, one had ischemic optic neuropathy, and one had unilateral optic neuritis. All four patients had considerably more damage in one eye than in the other, as indicated by their Humphrey visual fields. The multi-input procedure of Sutter was used to obtain 60 VEP responses to a scaled checkerboard pattern. The amplitude in each response was obtained using a root mean square measure of response magnitude. For each of the 60 pairs of responses, a ratio between the amplitude of the responses from the two eyes was obtained as a measure of the relative health of one eye compared with the other. The mean and SD of this ratio measure for the control group were used to specify confidence intervals for each of the 60 locations. All patients had Humphrey 24-2 visual fields performed. To allow a comparison of the mVEPs to the visual fields, a procedure was developed for displaying the results of both tests on a common set of coordinates. RESULTS: Except for a small interocular difference in timing attributable to nasotemporal retinal differences, the pairs of mVEP responses from the two eyes of the control subjects were essentially identical. Many of the pairs of responses from the patients were significantly different. In general, there was reasonably good agreement with the Humphrey 24-2 visual field data. Although some regions with visual field defects were not detected in the mVEP due to small responses from the better eye, other abnormalities were detected that were hard to discern in the visual fields. CONCLUSIONS: Local monocular damage to the ganglion cell/optic nerve can be quantitatively measured by an interocular comparison of the mVEP.

Anterior ischemic optic neuropathy and activated protein C resistance. A case report and review of the literature.

Nonarteritic anterior ischemic optic neuropathy (AION) is a well-described entity that is believed to be caused by abnormal anatomy of the optic disc and to be precipitated by several stressors or disease states. Activated protein C resistance (APCR) is a recently described mutation of factor V (FV) gene that renders FV resistant to cleavage by activated protein C. APCR predisposes to thrombotic events. The case of a 61-year-old woman with AION and activated protein C resistance is presented, and the management is discussed. We thoroughly review the literature on these two conditions. We propose that a prospective analysis of the potential role of APCR in some cases of AION is needed and suggest that physicians consider this and other prothrombotic states when evaluating patients with AION.

Clinical course of a cohort in the Cuban epidemic optic and peripheral neuropathy.

Nearly 51,000 Cubans were afflicted during an outbreak of an optic neuropathy (ON) and peripheral neuropathy (PN) between 1991 and 1993. We re-examined 14 of 20 affected individuals 16 months after an initial evaluation. The optic features were painless symmetric vision loss with poor visual acuity, color vision loss, central or cecocentral scotoma, optic disc pallor, and nerve fiber layer drop-out. The neurologic symptoms included stocking-glove sensory changes, hearing loss, leg cramps, sensory ataxia, hyperactive or absent reflexes, and complaints of memory loss. Two of 11 ON probands tested harbored Leber's hereditary optic neuropathy (LHON)-associated mitochondrial DNA mutations. All patients had received multivitamin therapy. We performed comparisons using the paired two-tailed t test. On re-examination, 12 of 14 patients demonstrated improvement. One patient remained unchanged. One woman with the nt-3460 mtDNA mutation showed a decline in vision. In patients not harboring mtDNA mutations, overall visual acuity, color vision, and peripheral neuropathy manifestations improved significantly (p < 0.001 for each manifestation). Most of the patients with Cuban ON and PN improved on multivitamin therapy. The significance of the mtDNA mutations is unclear. In the 2 LHON patients, manifestation of the disease may have been precipitated by nutritional deficiency. Patients with poor recovery or further deterioration should be evaluated for other factors, including poor vitamin therapy compliance and alternative diagnoses.

Pituitary adenoma revealed by paracentral junctional scotoma of traquair.

The term junctional scotoma of Traquair is used to describe a unilateral temporal visual field defect due to pathology of the ipsilateral optic nerve where it joins the chiasm. We report a 26-year-old woman who presented with blurred vision of her left eye. Examination revealed visual acuity of 20/20 OU, AO-HRR color plates 6/6 OD and 4.5/6 OS, and a 0.3 log unit relative afferent pupillary defect on the left side. Computer and Goldmann perimetry revealed a normal visual field OD and a paracentral temporal scotoma OS. Magnetic resonance imaging scan disclosed a sellar mass, expanding mainly into the left suprasellar area. Laboratory findings and pathological studies were consistent with a prolactin-secreting pituitary adenoma. While involvement of the temporal visual field in only one eye (junctional scotoma of Traquair) is found in about 10% of patients with pituitary adenoma, involvement of only the paracentral temporal visual field in one eye is rare (1-2%). Recognition of this rare syndrome is important because careful visual field analysis discloses a vertical step and helps to avoid misdiagnosing optic neuritis.

Magnetic resonance imaging of optic perineuritis.

Optic perineuritis, an uncommon variant of orbital pseudotumor, may be clinically indistinguishable from retrobulbar optic neuritis. Because treatment and prognosis for these two entities are different, early diagnosis is important. We report a case of a 47 year-old woman with clinical findings suggestive of retrobulbar optic neuritis, but whose magnetic resonance images suggested optic perineuritis. A dramatic clinical response to oral corticosteroids was observed. Optic perineuritis should be considered in cases of presumed retrobulbar optic neuritis. MRI may differentiate these two entities in the acute stage, and should be considered before treatment is decided.

Varicella-zoster virus retrobulbar optic neuritis in a patient with human immunodeficiency virus.

PURPOSE: To determine the cause of bilateral retrobulbar optic neuritis followed by progressive outer retinal necrosis in a patient with human immunodeficiency virus (HIV). METHODS: Extensive ophthalmologic, neurologic, infectious disease, rheumatologic, and radiologic examinations were performed. RESULTS: Cerebrospinal fluid samples taken after the onset of bilateral retrobulbar optic neuritis and before the development of clinical progressive outer retinal necrosis disclosed varicella-zoster virus from polymerase chain reaction and viral culture. CONCLUSION: Ophthalmologists and neurologists should consider varicella-zoster virus optic neuritis as a potential precursor of progressive outer retinal necrosis and as a cause of retrobulbar optic neuritis in patients infected with HIV.

Digitalis-induced visual disturbances with therapeutic serum digitalis concentrations.

OBJECTIVE: To assess the role of digitalis in the development of visual symptoms severe enough to warrant ophthalmologic consultation in patients who received digitalis and who had no other clinical or laboratory evidence of digitalis toxicity. DESIGN: Clinical case study. SETTING: Neuro-ophthalmology referral practice. PATIENTS: Six elderly patients (aged 66 to 85 years) who received digitalis were referred to ophthalmologists for evaluation of photopsia (five patients) or decreased visual acuity (one patient). No patient had chromatopsia or nonvisual clinical manifestations of digitalis intoxication at the time of examination. MEASUREMENTS: All patients had serum digitalis concentrations within or below the therapeutic range. In most patients, the electroretinographic cone b-wave implicit time was longer than normal. RESULTS: Discontinuation of digitalis therapy, which was possible in five patients, was followed by resolution of visual symptoms and by shortening of the b-wave implicit time. Characteristic features of digitalis-induced photopsia were its dependence on illumination and its tendency to be localized in peripheral visual fields. CONCLUSIONS: In an elderly patient receiving digitalis, the development of photopsia characterized by innumerable points of light in the peripheral visual fields or a decrease in visual acuity raises the possibility that the patient's visual disturbance may have been digitalis induced. Digitalis-induced visual disturbances other than chromatopsia or disturbances of color vision may occur in elderly patients who have no other clinical manifestations of digitalis intoxication and who have a serum digitalis concentration within or below the therapeutic range.

Microangiopathy of brain, retina, and inner ear.

Microangiopathy of brain, retina, and inner ear is a rare syndrome manifesting as arteriolar occlusions of the brain, retina, and inner ear, with resultant encephalopathy, visual, and hearing loss. Despite exhaustive laboratory examinations in these patients, no evidence of a systemic disease can be found. We treated and followed an adolescent with this disorder who initially presented with a branch retinal artery occlusion. A unique finding in this case was retinal vessel wall hyperfluorescence noted five days prior to retinal infarction. The patient developed recurrent branch artery occlusions, sensorineural hearing loss, and central nervous system infarctions despite anticoagulation and immunosuppressive treatment.

Mitochondrial DNA mutations in an outbreak of optic neuropathy in Cuba.

Since October 1991, nearly 51,000 Cubans have been afflicted in an outbreak of optic and peripheral neuropathies. To begin an investigation of the possible role of mitochondrial DNA (mtDNA) mutations in the outbreak, we studied mtDNA from 14 affected and two unaffected Cubans for the 12 mutations associated with Leber's hereditary optic neuropathy. Eleven probands (12 patients) had optic neuropathy and two had peripheral neuropathy only. We also studied two unaffected relatives of one proband. We identified two mtDNA mutations, at nucleotides 11778 and 3460, in two of the 11 probands with optic neuropathy. Although this data set is too small to reach statistically valid conclusions, it does suggest that mtDNA mutations might be contributing to the outbreak of optic neuropathy in Cuba.

Orbital polymyositis and giant cell myocarditis.

BACKGROUND: Orbital polymyositis associated with giant cell myocarditis rarely has been reported in the literature. The authors report the clinical, neuroradiographic, and histopathologic features of the only patient to survive this usually fatal syndrome after cardiac transplantation. FINDINGS: This 22-year-old white woman presented in 1991 with periorbital redness, swelling, and pain in both eyes that was unresponsive to antibiotic therapy. Results of her examination were significant for limited extraocular movements, ptosis, erythema, edema, chemosis, and exophthalmos. Electrocardiogram and chest x-ray were normal. Orbital computed tomographic scan showed swelling of the extraocular muscles up to and including their insertions. The patient was given the diagnosis of orbital polymyositis and her condition improved clinically and radiographically while taking parenteral steroids. One month after discharge, the patient was in cardiogenic shock. Endomyocardial biopsy showed giant cell myocarditis, and the patient underwent emergent cardiac transplantation. Despite a complicated postoperative course, the patient has done remarkably well. CONCLUSION: Although this disorder is rare, this case suggests the need for a high index of suspicion for giant cell myocarditis in patients with inflammatory orbital polymyositis. In non-Graves orbital polymyositis the patient should be questioned and instructed concerning the signs and symptoms of congestive heart failure. Chest x-ray, Holter monitoring, and electrocardiogram also should be performed and be repeated with an echocardiogram if there are any cardiac symptoms. In addition, early endomyocardial biopsy should be considered in the proper clinical setting, allowing timely diagnosis and expeditious cardiac transplantation.

Neuro-ophthalmic complications of intracranial catheters.

We report four patients who sustained direct injury to the brain after insertion of intraventricular shunts and pressure monitoring lines, which resulted in permanent neuro-ophthalmic deficits. These included hemianopsia from an optic tract lesion, esotropia and residual bilateral facial paresis from dorsal pontine injury, unilateral blindness from damage to the optic nerve, and dorsal midbrain syndrome from catheter compression in the region of the posterior commissure. Although presumably rare, such injuries should be considered in diagnosing patients with neuro-ophthalmic complaints after insertion of such devices.

Wallenberg's lateral medullary syndrome. Clinical-magnetic resonance imaging correlations.

OBJECTIVE: To correlate clinical and radiologic findings in patients with lateral medullary infarction. DESIGN: Case series with "blinded" evaluation of brain imaging. SETTING: Hospitalized and ambulatory patients at the Neurological Institute of New York (NY). PATIENTS: Thirty-three consecutive patients with lateral medullary syndrome were evaluated by the Stroke Center between 1983 and 1989. RESULTS: Ataxia (70%), numbness either of the ipsilateral face or of the contralateral body (64%), vertigo (51%), and dysphagia (51%) were the most frequent symptoms at onset. Eleven patients had ocular symptoms (diplopia or blurred vision). Horner's syndrome was found in 91%, ipsilateral ataxia in 85%, and contralateral hypalgesia in 85%. Nystagmus (61%) and facial weakness (42%) were less frequent. Head computed tomography was abnormal only when a cerebellar infarction was present (three cases). Magnetic resonance imaging, obtained in 22 cases, was normal in two; a lateral medullary infarction alone was present in 12, and a lesion extending beyond the lateral medulla was found in eight. No correlation was noted between facial weakness or ocular symptoms and infarction extending beyond the lateral medullary region. Vertebral artery disease was confirmed by vascular imaging or insonation studies in 73% of patients. CONCLUSIONS: The triad of Horner's syndrome, ipsilateral ataxia, and contralateral hypalgesia will clinically identify patients with lateral medullary infarction. Facial weakness and ocular symptoms are frequent and do not necessarily imply that the infarction extends beyond the lateral medulla. Cerebellar infarcts only infrequently accompany lateral medullary syndrome, suggesting that most of the posterior inferior cerebellar artery territory is spared, despite the high frequency of vertebral artery occlusion.