Corneal Confocal Microscopy Gauges Multiple Sclerosis Axonal Loss

The in vivo microscopy has been used in other peripheral neuropathies.

Corneal confocal microscopy may be a viable imaging biomarker in gauging axonal loss in multiple sclerosis (MS) patients, according to a study.

The microscopy — a non-invasive, in vivo imaging of corneal nerve fibers — has been previously used to identify axonal degeneration in several peripheral neuropathies. Researchers, led by Gulfidan Bitirgen, MD, questioned whether the assessment procedure would yield similar analysis in relapsing-remitting multiple sclerosis (RRMS) patients.

Axonal denegeration, along with demyelination, characterizes the progressive symptoms of MS. Researchers planned to observe it in a cross-sectional comparative study of 57 RRMS patients, and 30 healthy participants, conducted at a tertiary referral university hospital from May 27, 2016 — January 30, 2017.

Forty-two (74%) of the 57 RRMS patients were female, and the total RRMS population’s mean age was 35.4 years old. The comparative group’s characteristics were similar, with 19 out of 30 (63%) females, and a mean age of 34.8 years old.

Corneal subbasal nerve plexus morphologic features, corneal dendritic (CD) density, and peripapillary retinal nerve fiber layer (RNFL) thickness were assessed in the RRMS patients. The corneal subbasal nerve plexus measures and DC density was quantified in images acquired with the laser scanning microscope. Peripapillary RNFL thickness was measured with spectral-domain optical coherence tomography.

Researchers additionally assessed corneal nerve fiber and branch density, nerve fiber length, and association with the severity of neurologic disability as assessed by the Kurtzke Expanded Disability Status Scale (score range, 0-10, with higher scores indicating greater disability). Multiple Sclerosis Severity Scores (score range, 0.01-9.99, with higher scores indicating greater severity) were also graded.

The in vivo imaging revealed a reduced corneal nerve fiber density, nerve branch density, nerve fiber length, and mean peripapillary RNFL thickness reduction in RRMS patients versus healthy participants.

RRMS patients also showed an increased DC density versus healthy participants, vindependent of patients’ history of optic neuritis.

As opposed to previous studies, the corneal confocal microscopy showed that nerve fiber density and RNFL thickness in studied RRMS patients had inverse associations with both the Expanded Disability Status Scale (p= -0.295; P= .03 for nerve fiber density and p= -0.374; P= .004) for RNFL thickness) and the Multiple Sclerosis Severity Score (R= -0.354; P= .007 for nerve fiber density and R= -0.293; P= .03 for RNFL thickness).

The concluded data suggested to researchers that the corneal confocal microscopy procedure demonstrates axonal loss and increased DC density in MS patients. Researchers noted further longitudinal studies are needed to confirm the in vivo laser scanning microscopy’s utility as an imaging biomarker for MS patients.

The study, "Use of Corneal Confocal Microscopy to Detect Corneal Nerve Loss and Increased Dendritic Cells in Patients With Multiple Sclerosis," was posted online June 1 on the journal Jama Opthalmology.

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