MAR 29, 2012
Comprehensive Ophthalmology, Neuro-Ophthalmology/Orbit
Two recently published studies examine the role that diffusion tensor imaging (DTI) may play in the management of patients with optic neuritis due to multiple sclerosis. The studies' results suggest that DTI might be used in the future to stratify risk for incomplete recovery from optic neuritis, identify patients who may benefit from early therapeutic intervention with medications to treat multiple sclerosis and investigate whether transsynaptic neuronal degeneration is a mechanism for cerebral injury in multiple sclerosis, in addition to direct nerve damage due to inflammation.
The authors of one of the papers, which was published online in the journal, Human Brain Mapping, used DTI to assess optic radiations in 15 patients with previous optic nerve inflammation and nine healthy volunteers. Their results demonstrate that increased deviation and reduced magnitude of the principal directions of diffusion measured by DTI of the optic radiations of patients with prior optic neuritis episodes correlated with loss of amplitude in multifocal visual evoked potentials. The authors hypothesize that the association between DTI abnormalities in the optic radiations of patients and loss of afferent electrical activity in the optic nerves from optic neuritis could be evidence for the anterograde transsynaptic degeneration in the visual pathway that occurs following optic neuritis.
The authors of the other study, which was published in January in the Archives of Neurology, used DTI to evaluate optic nerves to determine whether diffusivity can be correlated with visual outcome six months after an acute episode of optic neuritis. They followed for at least six months 25 individuals who presented within 31 days after experiencing acute visual symptoms consistent with optic neuritis.
They demonstrated that decreased diffusivity in acute optic neuritis was associated with worse six-month visual outcome and correlated with visual evoked potential and retinal nerve fiber layer measures of axon and myelin injury. The authors conclude that axial diffusivity may serve as a marker of axon injury in acute white matter injury.