Abstract
Background: The onset of vision loss in Leber’s Hereditary Optic Neuropathy (LHON) is often mistaken for other types of optic neuritis. This study compares the prevalence of brain imaging findings at time of onset in affected LHON patients and other types of optic neuritis; namely Clinically Isolated Syndrome, Multiple Sclerosis, Myelin Oligodendrocyte antibody, and Neuromyelitis Optica.
Methods: A masked analysis of MRIs from a group of genetically confirmed LHON patients was compared to MRIs from the sex and age-matched Optic Neuritis group. Brain imaging obtained within 12 months of the onset of visual loss were used.
Results: We identified 23 LHON patients with a total of 46 affected eyes. The average age at time of diagnosis was 45 ± 13.3 years old. Retrospective analysis of previously interpreted MRIs was completed and revealed that the most affected optic nerve segment was the optic chiasm (39.1%) followed by the orbital segment and optic tract each with 34.8% patient involvement. Canalicular involvement was observed in 29.2% of patients and intracranial segment involvement was observed in 17.2% of patients.
Ten of the 23 LHON identified patients were matched to their optic neuritis group based on age and sex. Eight males and two females with a total of 20 affected eyes were included. All patients had a confirmed genetic mutation with a median age of 33 (IQR 26 – 39) years (range 22 – 62 years) at time of diagnosis. The time interval from vision loss to MRI (TIVM) ranged from 1 to 12 months in all 20 affected eyes. The median TIVM was 1 (IQR 1 – 4) month. The ON group consisted of four patient groups based on diagnosis. We included ten patients with clinically isolated syndrome with thirteen affected eyes with a median age of 34.5 (IQR 25 – 44) years (range 15 – 57 ) at time of diagnosis, ten multiple sclerosis patients with eleven affected eyes and a median age of 32.5 (IQR 30 – 37) years (range, 22 – 65 years), ten myelin oligodendrocyte antibody patients with fourteen affected eyes and median age of 32.5 (IQR 30 – 41) years (range, 24 – 61 years) at time of diagnosis, and three neuromyelitis optica patients (2 males and 1 female) with four affected eyes; median age of 30 (IQR 25 – 45) years (range 25 – 45 years) at time of diagnosis.
Conclusion: Our results illustrate that chiasmal involvement is more common in LHON patients than in ON patients (specifically in the myeline oligodendrocyte antibody group) during the first year of vision loss p=0.057. Optic tract involvement was also more common in the LHON cohort compared to the optic neuritis cohort (specifically when compared the clinically isolated syndrome and multiple sclerosis groups) p=0.087 in both groups. White matter involvement was only seen in one LHON patient (in the periventricular region). When compared to the optic neuritis cohort, brain white matter involvement was seen in 70%, 80%, and 80% (p=0.02, p=0.006, and p=0.006) in each of the clinically isolated syndrome, multiple sclerosis and myeline oligodendrocyte antibody groups respectively. Brain white matter involvement was not observed in any of the neuromyelitis optica patients. Regression analysis revealed a slight trend that higher involvement might be associated with slightly worse visual acuity, but this trend is not statistically significant p = 0.246. Only one patient with an involvement along the optic chiasm presented with normal visual acuity of 20/30 and 20/40, right eye and left eye respectively.