The Correlation Between Functional and Morphometric Small Fiber Assessment in Mixed Etiology Polyneuropathy

Area of Science:

• Neurology
• Ophthalmology
• Diagnostic Imaging

Background:

• Skin biopsies are the gold standard for diagnosing small fiber neuropathy.
• Corneal confocal microscopy (CCM) is an emerging alternative diagnostic tool.
• Comparing CCM and skin biopsy correlations with nerve function is crucial for diagnostic validation.

Purpose of the Study:

• To compare the diagnostic utility of CCM and skin biopsies in assessing peripheral nerve function.
• To evaluate the correlation between corneal nerve morphology and quantitative sensory testing (QST) results.
• To determine the relationship between intraepidermal nerve fiber density (IENFD) and QST in polyneuropathy.

Main Methods:

• Prospective cohort study of 244 patients undergoing polyneuropathy work-up.
• Corneal confocal microscopy (CCM) and skin biopsies were performed.
• Corneal nerve fiber density (CNFD), length (CNFL), branch density (CNBD), tortuosity (CNFT), and IENFD were measured and correlated with QST results.

Main Results:

• Corneal nerve parameters (CNFD, CNFL, CNBD, CNFT) showed negligible or no significant correlations with QST measures.
• Intraepidermal nerve fiber density (IENFD) demonstrated moderate correlations with warm detection threshold and mechanical pain threshold.
• IENFD also showed weak correlations with cold detection threshold, mechanical detection threshold, and vibration detection threshold.

Conclusions:

• Intraepidermal nerve fiber density (IENFD) correlates better with small and large fiber function than CCM measures in mixed etiology polyneuropathy.
• CCM parameters showed limited utility in reflecting peripheral nerve function compared to IENFD.
• Further longitudinal studies are required to establish the clinical utility of CCM for monitoring neuropathy progression.