Ординатура / Офтальмология / Английские материалы / Electrophysiology of Vision_Lam_2005

improvement may precede clinical recovery in cortical visual impairment and may serve as a prognostic indicator in disorders such as encephalopathy, hydrocephalus, basilar artery occlusion, and trauma (94–96). In children with cortical visual impairment, sweep VEP is a valid method for measuring grating acuity (97). However, caution should be exercised in making a diagnosis of cortical visual impairment in infants with a reduced flash VEP because of the possibility of delayed visual pathway maturation. In addition, children with central nervous system diseases but normal vision may demonstrate abnormal flash VEP responses (98). On the other hand, in some cases of complete cortical blindness, a residual flash VEP response may still be present (99,100).

Spinocerebellar Ataxia, Olivopontocerebellar

Atrophy, and Friedreich Ataxia

Spinocerebellar ataxia may occur sporadically or as an autosomal dominant disorder. Autosomal dominant spinocerebellar ataxia is genetically heterogenous and is associated with genetic expansion of repeat trinucleotide CAG. For example, SCA1 is due to increased CAG repeats of the ataxin-1 gene on chromosome 6p23; SCA2 is associated with CAG repeats of the ataxin-2 on chromosome 12p24; SCA6 is related to CAG repeats of the alpha-1A calcium channel subunit gene on chromosome 19p13; and SCA12 is caused by CAG repeats of the gene encoding a subunit of the protein phosphatase PP2A on chromosome 5. SCA1 is also known as olivopontocerebellar atrophy 1. Aside from signs of progressive cerebellar dysfunction such as gait ataxia and dysarthria, patients may also have optic atrophy, progressive retinal degeneration, and decreased corneal endothelial density (101–104). Symptoms and signs of the disease are highly variable with the number of CAG repeats being inversely correlated with age of disease onset. Abe et al. (101) found reduced full-field ERG b-wave and oscillatory potentials in patients with SCA1 (101). The same investigation group also demonstrated macular degeneration with reduced central multifocal ERG responses and rare impaired full-field cone ERG responses

in patients with SCA7 (105). In addition, generalized impairment of the full-field ERG including the a-wave and b-wave is found in many patients with olivopontocerebellar atrophy type II (106). Other forms of olivopontocerebellar atrophies distinct from spinocerebellar ataxia have also been described. Taken together, progressive macular or generalized retinal dysfunction may occur in this group of patients as demonstrated by ERG responses. Further, impaired VEP responses have been reported in SCA1 and SCA2 patients with normal retinal appearance, but whether these abnormal responses are due to early retinal dysfunction or central visual pathway dysfunction has not been clarified (107).

Friedreich ataxia is an autosomal recessive disorder characterized by degeneration of the spinocerebellar tracts, dorsal columns, pyramidal traits, cerebellum, and medulla. Clinical manifestations include progressive cerebellar dysfunction, hypoactive deep tendon reflexes, dysarthria, and nystagmus. Impaired VEP responses implying central visual pathway dysfunction are found in many affected patients (108,109).

Alzheimer Disease

Described in 1907 by Alzheimer (110), Alzheimer disease is the most common form of dementia. The disorder may be sporadic or inherited as an autosomal dominant trait. Progressive dementia and histologic finding of neurofibrillary tangles of the central nervous system are some of the features of Alzheimer disease. Ocular findings may include impaired visual acuity, visual field, color perception, contrast sensitivity, and eye movement (111).

Despite numerous studies, the clinical utility of visual electrophysiologic testing in Alzheimer disease is uncertain. Focal and full-field ERG responses are normal (112,113). Loss of retinal ganglion cells with axonal degeneration of the optic nerve is found on postmortem studies of patients with Alzheimer disease (114). Although some of these changes may be attributable to normal aging (115), retinal nerve fiber layer thickness as measured by optical coherence tomography has

been found to be reduced in patients with Alzheimer disease when compared to age-matched control subjects (116). However, studies of pattern ERG, a measure of ganglion cell function, have revealed mixed results. Some studies showed normal pattern ERG responses in Alzheimer patients (112,117); while other studies demonstrated abnormal pattern ERG responses (116,118). These conflicting results are likely due to differences in patient population and methodology as well as the possible effect of defocusing in Alzheimer patients as compared to normal subjects (119,120).

Likewise, VEP studies in Alzheimer disease are equally conflicting. While some studies reported delayed pattern VEP in Alzheimer patients and demonstrated a correlation between delayed flash VEP and dementia (121–123), no correlation between pattern or flash VEP and the degree of dementia was shown in one study (124) and another study noted normal VEP responses (113). Of interest, in one study, impairment of the visual association cortices was found (125).

Parkinson Disease

After Alzheimer disease, Parkinson disease is the second most common neurodegenerative disorder. The condition is due to loss of dopaminergic neurons particularly in the basal ganglia and substantia nigra. Clinical features include tremor, rigidity, bradykinesia, and dementia. Full-field ERG responses are generally mildly to moderately impaired in Parkinson patients with improved responses after oral or intravenous levodopa administration (126,127). The EOG abnormalities such as delay in reaching the light-peak as well as reduced light-peak have also been reported (128). Pattern ERG and VEP responses are also delayed even in the early tage of Parkinson disease with pattern ERG being more delayed and more reversible with levodopa treatment than VEP (129). Visual processing deficits in Parkinson disease are also evident on onset=offset pattern VEP and chromatic VEP (130,131). Utility of intraoperative VEP monitoring during pallidotomy on Parkinson patients has been demonstrated (132,133). The procedure is performed on patients who are

not responding adequately to medical treatment and involves making a lesion in the globus pallidus internus near the optic tract. Intracranial recording of VEP with electrode stimu lation determines the location of the optic tract and allows accurate targeting of the globus pallidus internus.

Leukodystrophies

Leukodystrophies is a group of genetically heterogeneous disorders characterized by degeneration of the white matter of the central nervous system. Examples of leukodystrophy include adrenoleukodystrophy (X-linked), metachromatic leukodystrophy (recessive), and various lyposomal disorders (recessive). The VEP responses may be impaired due to demyelination and white matter degeneration (134–138). For instance, in adrenoleukodystrophy, Kaplan et al. (139) using pattern VEP, magnetic resonance imaging, and clinical examination, found 63% of patients had visual pathway abnormalities involving the optic nerve head, optic nerves, lateral geniculate bodies, optic radiations, and parietal-occipi- tal cortex (139). The same authors noted that 17% of the affected males had abnormal pattern VEP which did not improve with medical treatment that reduced very-long-chain fatty acid levels (140).

REFERENCES

1.Kass MA, Heuer DK, Higginbotham EJ, Johnson CA, Keltner JL, Miller JP, Parrish RK, II, Wilson MR, Gordon MO. The ocular hypertension treatment study. A randomized trial determines that topical ocular hypertensive medication delays or prevents the onset of primary open-angle glaucoma. Arch Ophthalmol 2002; 120:701–713.

2.Papst N, Bopp M, Schnaudigel OE. Pattern electroretinogram and visual evoked cortical potentials in glaucoma. Graefes Arch Clin Exp Ophthalmol 1984; 222:29–33.

3.Ringens PJ, Vijfvinkel-Bruinenga S, van Lith GH. The pat- tern-elicited electroretinogram, I. A tool in the early detection of glaucoma? Ophthalmologica 1986; 182:171–175.

4.van den Berg TJ, Riemslag FC, de Vos GW, Verduyn Lunel HF. Pattern ERG and glaucomatous visual field defects. Doc Ophthalmol 1986; 62:335–341.

5.Howe JW, Mitchell KW. Simultaneous recording of the pattern electroretinogram and visual evoked cortical potentials in a group of patients with chronic glaucoma. Doc Ophthalmol Proc Ser 1984; 40:101–107.

6.Ohta H, Tamura T, Kawasaki K. [Negative wave in human pattern ERG and its suppression in glaucoma]. Nippon Ganka Gakkai Zasshi 1986; 90:882–887.

7.Weinstein GW, Arden GB, Hitchings RA, Ryan S, Calthorpe CM, Odom JV. The pattern electroretinogram (PERG) in ocular hypertension and glaucoma. Arch Ophthalmol 1988; 106:923–928.

8.Bo¨mer TG, Meyer JH, Bach M, Funk J. Pattern electroretinogram and computerized optic nerve-head analysis in ocular hypertension—interim results after 2.5 years. Ger J Ophthalmol 1996; 5:26–30.

9.Graham SL, Drance SM, Chauhan BC, Swindale NV, Hnik P, Mikelberg FS, Douglas GR. Comparison of psychophysical and electrophysiological testing in early glaucoma. Invest Ophthalmol Vis Sci 1996; 37:2651–2662.

10.Martus P, Korth M, Horn F, Junemann A, Wisse M, Jonas JB. A multivariate sensory model in glaucoma diagnosis. Invest Ophthalmol Vis Sci 1998; 39:1567–1574.

11.Ruben ST, Hitchings RA, Fitzke F, Arden GB. Electrophysiology and psychophysics in ocular hypertension and glaucoma: evidence for different pathomechanisms in early glaucoma. Eye 1994; 8:516–520.

12.Ruben ST, Arden GB, O’Sullivan F, Hitchings RA. Pattern electroretinogram and peripheral colour contrast thresholds in ocular hypertension and glaucoma: comparison and correlation of results. Br J Ophthalmol 1995; 79:326–331.

13.Parisi V, Manni G, Centofanti M, Gandolfi SA, Olzi D, Bucci MG. Correlation between optical coherence tomography, pattern electroretinogram, and visual evoked potentials in openangle glaucoma patients. Ophthalmology 2001; 108:905–912.

14.Martus P, Junemann A, Wisse M, Budde WM, Horn F, Korth M, Jonas JB. Multivariate approach for quantification of morphologic and functional damage in glaucoma. Invest Ophthalmol Vis Sci 2000; 41:1099–1110.

15.Bayer AU, Maag KP, Erb C. Detection of optic neuropathy in glaucomatous eyes with normal standard visual fields using a test battery of short-wavelength automated perimetry and pattern electroretinography. Ophthalmology 2002; 109: 1350–1361.

16.Bayer AU, Erb C. Short wavelength automated perimetry, frequency doubling technology perimetry, and pattern electroretinography for prediction of progressive glaucomatous standard visual field defects. Ophthalmology 2002; 109:1009–1017.

17.Bach M, Speidel-Faux A. Pattern electroretinogram in glaucoma and ocular hypertension. Doc Ophthalmol 1989; 73: 173–181.

18.Pfeiffer N, Bach M. The pattern-electroretinogram in glaucoma and ocular hypertension: a cross-sectional and longitudinal study. Ger J Ophthalmol 1992; 1:35–40.

19.Pfeiffer N, Tillmon B, Bach M. Predictive value of the pattern electroretinogram in high-risk ocular hypertension. Invest Ophthalmol Vis Sci 1993; 34:1710–1715.

20.Porciatti V, Falsini B, Brunori S, Colotto A, Moretti G. Pattern electroretinogram as a function of spatial frequency in ocular hypertension and early glaucoma. Doc Ophthalmol 1987; 65:349–355.

21.Graham SL, Wong VA, Drance SM, Mikelberg FS. Pattern electroretinograms from hemifields in normal subjects and patients with glaucoma. Invest Ophthalmol Vis Sci 1994; 35:3347–3356.

22.Bach M, Sulimma F, Gerling J. Little correlation of the pattern electroretinogram (PERG) and visual field measures in early glaucoma. Doc Ophthalmol 1997; 94:253–263.

23.Neoh C, Kaye SB, Brown MS, Ansons AM, Wishart P. Pattern electroretinogram and automated perimetry in patients with

glaucoma and ocular hypertension. Br J Ophthalmol 1994; 78:359–362.

24.O’Donaghue E, Arden GB, O’Sullivan F, Falcao-Reis F, Moriarty B, Hitchings RA, Spilleers W, Hogg CR, Weinstein G. The pattern electroretinogram in glaucoma and ocular hypertension. Br J Ophthalmol 1992; 76:387–394.

25.Trick GL, Bickler–Bluth M, Cooper DG, Kolker AE, Nesher R. Pattern reversal electroretinogram (PRERG) abnormalities in ocular hypertension: correlation with glaucoma risk factors. Curr Eye Res 1988; 7:201–206.

26.Salgarello T, Colotto A, Falsini B, Buzzonetti L, Cesari L, Iarossi G, Scullica L. Correlation of pattern electroretinogram with optic disc cup shape in ocular hypertension. Invest Ophthalmol Vis Sci 1999; 40:1989–1997.

27.Hood DC, Zhang X. Multifocal ERG and VEP responses and visual fields: comparing disease-related changes. Doc Ophthalmol 2000; 100:115–137.

28.Hood DC, Zhang X, Greenstein VC, Kangovi S, Odel JG, Liebmann JM, Ritch R. An interocular comparison of the multifocal VEP; a possible technique for detecting local damage to the optic nerve. Invest Ophthalmol Vis Sci 2000; 41:1580– 1587.

29.Hood DC, Greenstein VC, Holopigian K, Bauer R, Firoz B, Liebmann JM, Odel JG, Ritch R. An attempt to detect glaucomatous damage to the inner retina with the multifocal ERG. Invest Ophthalmol Vis Sci 2000; 41:1570–1579.

30.Klistorner AI, Graham SL, Martins A. Multifocal pattern electroretinogram does not demonstrate localised field defects in glaucoma. Doc Ophthalmol 2000; 100:155–165.

31.Holopigian K, Greenstein VC, Seiple W, Hood DC, Ritch R. Electrophysiologic assessment of photoreceptor function in patients with primary open-angle glaucoma. J Glaucoma 2000; 9:163–168.

32.Viswanathan S, Frishman LJ, Robson JG, Walters JW. The photopic negative response of the flash electroretinogram in primary open angle glaucoma. Invest Ophthalmol Vis Sci 2001; 42:514–522.

33.Hasegawa S, Takagi M, Usui T, Takada R, Abe H. Waveform changes of the first-order multifocal electroretinogram in patients with glaucoma. Invest Ophthalmol Vis Sci 2000; 41:1597–1603.

34.Galloway NR, Barber C. The pattern evoked response in disorders of the optic nerve. Doc Ophthalmol 1986; 63:31–36.

35.Halliday AM, McDonald WI, Mushin J. Delayed visual evoked response in optic neuritis. Lancet 1972; 1:982–985.

36.Plant GT, Hess RF, Thomas SJ. The pattern evoked electroretinogram in optic neuritis: a combined psychophysical and electrophysiological study. Brain 1986; 109:469–490.

37.Porciatti V, Sartucci F. Retinal and cortical evoked responses to chromatic contrast stimuli: specific losses in both eyes of patients with multiple sclerosis and unilateral optic neuritis. Brain 1996; 119:723–740.

38.Frederiksen JL, Petrera J. Serial visual evoked potentials in 90 untreated patients with acute optic neuritis. Surv Ophthalmol 1999; 44(suppl 1):S54–S62.

39.Trauzettel-Klosinski S, Diener H-C, Dietz K, Zrenner E. The effect of oral prednisolone on visual-evoked potential latencies in acute optic neuritis monitored in a prospective, randomized, controlled study. Doc Ophthalmol 1996; 91:165–179.

40.Leys MJ, Candaele CM, de Rouck AF, Odom JV. Detection of hidden visual loss in multiple sclerosis: a comparison of pattern-reversal visual evoked potentials and contrast sensitivity. Doc Ophthalmol 1991; 77:255–264.

41.Halliday AM, McDonald WI, Mushin J. Delayed patternevoked responses in optic neuritis in relation to visual acuity. Trans Ophthalmol Soc UK 1973; 93:315–324.

42.Celesia GG, Kaufman DI, Brigell M, Toleikis S, Kokinakis D, Lorance T, Lizano B. Optic neuritis: a prospective study. Neurology 1990; 40:919–923.

43.Asselman P, Chadwick DW, Marsden DC. Visual evoked responses in the diagnosis and management of patients suspected of multiple sclerosis. Brain 1975; 98:261–282.

44.Fillipini G, Comi G, Cosi V, Bevilacqua L, Ferrarini M, Martinelli V, Bergamaschi R, Filippi M, Citterio A, D’Incerti L. Sensitivities and predictive values of paraclinical tests for diagnosing multiple sclerosis. J Neurol 1994; 241:132–137.

45.Hume AL, Waxman SG. Evoked potentials in suspected multiple sclerosis: diagnostic value and prediction of clinical course. J Neurol Sci 1988; 83:191–210.

46.Lee KH, Hashimoto SA, Hooge JP, Kastrukoff LF, Oger JJ, Li DK, Paty DW. Magnetic resonance imaging of the head in the diagnosis of multiple sclerosis: a prospective 2-year follow-up with comparison of clinical evaluation, evoked potentials, oligoclonal banding, and CT. Neurology 1991; 41:657–660.

47.Matthews WB, R W-BJ, Pountney E. Evoked potentials in the diagnosis of multiple sclerosis: a follow up study. J Neurol Neurosurg Psychiatry 1982; 45:303–307.

48.Gronseth GS, Ashman EJ. Practice parameter: the usefulness of evoked potentials in identifying clinically silent lesions in patients with suspected multiple sclerosis (an evi- dence-based review). Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology 2000; 54:1720–1725.

49.McDonald WI, Compston A, Edan G, Goodkin D, Hartung HP, Lublin FD, McFarland HF, Paty DW, Polman CH, Reingold SC, Sandberg-Wollheim M, Sibley W, Thompson A, van den Noort S, Weinshenker BY, Wolinsky JS. Recommended diagnostic criteria for multiple sclerosis: guidelines from the International Panel on the diagnosis of multiple sclerosis. Ann Neurol 2001; 50:121–127.

50.Kaufman DI, Lorance RW, Woods M, Wray SH. The pattern electroretinogram: a long-term study in acute optic neuropathy. Neurology 1988; 38:1767–1774.

51.Seiple W, Price MJ, Kupersmith M, Siegel IM, Carr RE. The pattern electroretinogram in optic nerve disease. Ophthalmology 1983; 90:1127–1132.

52.Holder GE. The pattern electroretinogram in anterior visual pathway dysfunction and its relationship to the pattern visual evoked potentials: a personal clinical review of 743 eyes. Eye 1997; 11:924–934.