Can Lamina Cribrosa Indicate Optic Neuritis in Multiple Sclerosis?

In a recent article published in Neurology India, Researchers in Turkey have found that the lamina cribrosa was thinner in Multiple Sclerosis patients with VEP pathology.

MS is a chronic, autoimmune, inflammatory demyelinating neurodegenerative disease of the central nervous system, which is usually characterised by variable clinical outcomes owing to recurrent episodes of immune-mediated demyelination, glial scar formation, and axonal loss. Optic neuritis (ON), an acute inflammatory demyelinating disorder of the optic nerve, is the first sign of MS in approximately 20% of MS patients. Approximately, half of MS patients develop ON during the course of the disease.

The intraocular part of the optic nerve is referred to as the optic nerve head; it is about 1 mm in length and is often described in terms of four parts: the lamina retinalis, lamina choroidalis, lamina cribrosa (LC), and retrolaminar layer. The LC consists of perforated hard connective tissue and elastic fibers. The glial tissue supporting the axons is most abundant in this layer. The LC is an essential web-like tissue layer, where abundant glia that support the axons of retinal ganglion cells are found; it allows the passage of nutrients and oxygen. Spectral domain optical coherence tomography (SD-OCT) is a noninvasive, safe, and easy imaging modality that is used to assess the thickness of retinal tissues and the retinal nerve fiber layer (RNFL) and the lamina cribrosa thickness (LCT).

The measurement of visual evoked potentials (VEPs) is the best way to reveal ON in MS patients. VEPs have been shown to detect ON even in silent cases that are clinically faint. However, although the specificity and sensitivity of VEPs are high in determining ON, they are not 100%. In spite recent advances in the treatment of MS, there is still no biomarker or method that can establish a definitive diagnosis. Although VEPs are currently considered the most sensitive and specific method for detecting ON in MS, abnormal VEP findings are detected in about 65% of MS patients without ON symptoms or history.

The authors divided the patients enrolled in this prospective, cross-sectional study into three groups. Group 1 consisted of 25 relapsing-remitting MS patients with VEP pathology in one or both eyes. In patients with VEP pathology in both eyes, one eye was chosen randomly. Group 2 comprised 25 relapsing-remitting MS patients with no VEP pathology or optic neuritis history. A randomly selected single eye of each patient was evaluated. Group 3 consisted of 25 age- and sex-matched healthy volunteers; a randomly selected single eye of these participants was examined. LCT, LCD, and retinal nerve fiber layer (RNFL) thickness measurements were determined in four quadrants (superior, inferior, nasal, and temporal) by SD-OCT.

They found that there was a statistically significant difference in LCT among the three groups. Posthoc analysis revealed a significant difference between Groups 1 and 3 but not between Groups 1 and 2 or between Groups 2 and 3.

There was a weak positive correlation between LCT and RNFL inferior, RNFL nasal, and RNFL temporal thickness measurements. There was no significant correlation between LCT and RNFL superior thickness measurements. There was a weak positive correlation between LCD and RNFL nasal thickness. They also found a significant decrease in RNFL thickness in MS patients with VEP pathology. There was also a significant relationship between RNFL and LCT.

They suggest that measurements of the LC, through which nutrients and oxygen pass, may be useful as a prognostic indicator of ON in MS patients.

Reference: Mehmet Hamamci, Bekir Küçük, Seray A Bayhan, Hasan A Bayhan, Levent E İnan Neurology India DOI:10.4103/0028-3886.364057