To correlate or not to correlate that is the question

Aboulenein-Djamshidian F, Krššák M, Serbecic N, Rauschka H, Beutelspacher S, Kukurová IJ, Valkovič L, Khan A, Prayer D, Kristoferitsch W. CROP – The Clinico-Radiologico-Ophthalmological Paradox in Multiple Sclerosis: Are Patterns of Retinal and MRI Changes Heterogeneous and Thus Not Predictable? PLoS One. 2015 Nov 13;10(11):e0142272.

BACKGROUND:To date, no direct scientific evidence has been found linking tissue changes in multiple sclerosis (MS) patients, such as demyelination, axonal destruction or gliosis, with either steady progression and/or stepwise accumulation of focal CNS lesions. Tissue changes such as reduction of the retinal nerve fiber layer (RNFL) and the total macular volume (TMV), or brain- and spinal cord atrophy indicates an irreversible stage of tissue destruction. Whether these changes are found in all MS patients, and if there is a correlation with clinical disease state, remains controversial. The objective of our study was to determine, whether there was any correlation between the RNFL or TMV of patients with MS, and: (1) the lesion load along the visual pathways, (2) the ratios and absolute concentrations of metabolites in the normal-appearing white matter (NAWM), (3) standard brain atrophy indices, (4) disease activity or (5) disease duration.
METHODS:28 MS patients (RRMS, n = 23; secondary progressive MS (SPMS), n = 5) with moderately-high disease activity or long disease course were included in the study. We utilised: (1) magnetic resonance imaging (MRI) and (2) -spectroscopy (MRS), both operating at 3 Tesla, and (3) high-resolution spectral domain-OCT with locked reference images and eye tracking mode) to undertake the study.
RESULTS:There was no consistency in the pattern of CNS metabolites, brain atrophy indices and the RNFL/TMV between individuals, which ranged from normal to markedly-reduced levels. Furthermore, there was no strict correlation between CNS metabolites, lesions along the visual pathways, atrophy indices, RNFL, TMV, disease duration or disability.
CONCLUSIONS:Based on the findings of this study, we recommend that the concept of ‘clinico-radiologico paradox’ in multiple sclerosis be extended to CROP-‘clinico-radiologico-ophthalmological paradox’. Furthermore, OCT data of MS patients should be interpreted with caution.

There have been a number of reports looking at optic nerve damage and then correlating this with the degree of damage in the brain using MRI and it is said by some that they are correlated but in this study they do not find such correlates. 

Whilst one can understand that if you have more active MS then the chance of having an optic nerve lesion may be higher and so likewise having a brain lession maybe higher, but they are distinct regions of the CNS and to look at they eye and them think you know what is going on in the brain, is in my view not going to be a sensible approach. Optic neuritis is on of the early features of MS and can cause damage to the eye that may not be reflected in the brain. So this is yet another clinical correlation that is best left in the bin if you want to look for brain lesions do an MRI and if you want to look at eye problems do an OCT, but it is my view rather daft to do an OCT an then to think it tells you enough information about what is going on in the brain.

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