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New England Eye Center, Tufts Medical Center, Boston, MassachusettsDysautonomia Center, Department of Neurology, New York University School of Medicine, New York, New YorkOphthalmology Department, Pontifical Catholic University of Chile, Santiago de Chile, Chile
Electrophysiology studies have documented changes in visual evoked potential (VEP), multifocal electroretinography (mfERG), and pattern electroretinography (pERG) in symptomatic patients. In acute LHON, decreased amplitude and increased latency in the VEP P100 wave have been documented.
We observed a 19-year-old male with the 3460 mutation who developed sequential vision loss in both eyes. We also evaluated his brother, a carrier of the same mutation who had not developed vision loss. We documented the simultaneous progression of structural (RNFL, GCC, and funduscopic examination) and functional (VEP, pERG, and mfERG) disease manifestations in the symptomatic brother both before and after symptom onset and compared these findings with those of the asymptomatic carrier brother. All patients herein have provided written consent in accordance with the guidelines of Tufts Medical Center.
A 19-year-old male student-athlete with a history of migraine presented to the neuro-ophthalmology clinic with 5 weeks of worsening central vision OD (20/200). Vision was limited to counting fingers with a central scotoma detected on automated visual fields (30-2 strategy, Humphrey Field Analyzer, Carl Zeiss Meditec, Dublin, Calif.). The patient noted photophobia of his left eye, which had a visual acuity of 20/15 and no visual field defect. There was no relative afferent pupillary defect. Peripapillary telangiectasias were present in both eyes. Genetic testing revealed LHON mitochondrial DNA mutation 3460G>A (Athena Diagnostics, Marlboro, Mass.). The patient was prescribed idebenone and memantine and re-evaluated at 4 weeks, 6 weeks, and 1 year. Two weeks after vision loss in the right eye, the patient noted mild loss of vision in his left eye (20/25 with a mild central scotoma).
High-definition OCT (Cirrus HD-OCT Model 4000, Carl Zeiss Meditec, Dublin, Calif.) was used to quantify the thickness of the RNFL and GCC at each visit. Two weeks before symptom onset in the left eye, RNFL swelling was detected (average thickness 132 µm, normal thickness 87–100 µm
), followed by degeneration of both the RNFL and GCC over the course of 1 year. RNFL and GCC followed a similar course in the right eye over 1 year, consistent with documented progression of LHON (Fig. 1).
VEP P100 signal amplitudes (RETI-Port/scan, Roland Consult, Brandenburg, Germany) were mildly decreased in the right (affected) eye and normal in the left (unaffected) eye (4 µV OD, 7 µV OS at 60 minutes) at presentation. P100 latency was unaffected (80 ms OD, 106 ms OS at 60 minutes). On pERG, there was slightly decreased amplitude of the N95 component with normal latency. mfERG 1 year after symptom onset showed mildly decreased amplitude of signals bilaterally (Fig. 2).
The patient’s younger brother, an 18-year-old carrier of the same mutation, did not develop vision loss or peripapillary telangiectasias over the course of 1 year. Visual acuities and visual fields remained normal. At 2 visits 6 months apart, OCT did not reveal swelling or degeneration in either RNFL or GCC. pERG showed no abnormalities of the N95 component (Fig. 3).
We have demonstrated structural changes consistent with functional visual decline and electrophysiological deficits in a patient with LHON. At our first evaluation 2 weeks before vision loss, the RNFL and GCC were thickened, suggesting possible pathologic changes of both axons and ganglion cells at this early stage. It is unknown when the swelling began. The GCC began to thin slightly at the time of vision loss, after which GCC thinning took place at a rate of about 0.6 µm/wk. The RNFL remained swollen through about 6 weeks after vision loss, which was followed by rapid thinning over the course of the 1-year study period. These results suggest that thickening of RNFL or GCC may be a precursor of acute vision loss in LHON, as previously suggested.
VEP signals were normal in the presymptomatic period; P100 amplitudes decreased only after vision loss. One year after symptom onset, pERG showed mildly decreased amplitude of the N95 component, suggesting loss of ganglion cell function. We have noted this finding in other cases of LHON, and thus the phenomenon should be subject to further study. mfERG amplitudes were mildly decreased in both affected eyes, indicating possible outer retinal involvement, as previously reported.
The patient’s unaffected brother, a carrier of the same mutation, did not demonstrate structural abnormalities on fundoscopy or OCT. Although there has been evidence of RNFL thickening in unaffected male carriers, the finding was not significant for patients with the 3460 mutation.