Alterations in blink and masseter reflex latencies in older adults with neurocognitive disorder and/or diabetes mellitus

Patterns of facial and blink reflex abnormalities in type 2 diabetes mellitus patients with short disease duration: a clue to subclinical cranial neuropathy

Background

Cranial neuropathies occur in 3 to 14% of diabetic patients. Motor conduction study of the facial nerve and blink reflex study are electrophysiologic techniques used to assess the facio-trigeminal pathway in diabetic patients. The patterns of facial and blink reflex abnormalities are inconsistent among studies. This study aimed to assess the subclinical facial nerve and blink reflex abnormalities patterns in short-duration type 2 diabetes mellitus patients. This cross-sectional study included 30 type 2 diabetic patients with disease duration ≤ 5 years. We included only patients with the Toronto clinical neuropathy score ≤ 5. We enrolled 30 age- and sex-matched healthy subjects as a control group. We performed facial nerve motor conduction and blink reflex studies. Patients with prior history of cranial nerve lesions, stroke, or any other disease-causing polyneuropathy or drug-induced neuropathy were excluded from the study.

Results

Thirty diabetic patients were included, 20 females (66.7%) and ten males (33.3%). Their mean age was 52.63 ± 8.94 years. None of the patients had clinical evidence of neuropathy. There were significant differences between patients and controls in the distal latencies and amplitudes of facial nerve compound muscle action potentials and contralateral R2 late response latencies of the blink reflex. We detected subclinical cranial abnormalities in 6 diabetic patients (20%). One of them (3.3%) had facial nerve conduction abnormalities, four of them (13.4%) had blink reflex abnormalities, and one of them (3.3%) had both facial nerve and blink reflex abnormalities.

Conclusion

Subclinical cranial neuropathy can occur in short-duration type 2 diabetes mellitus patients. We detected different blink reflex patterns and facial conduction study abnormalities. We recommend blink reflex and facial nerve conduction studies as simple tests for the early evaluation of neurological subclinical affection in patients with short disease duration of T2DM as they may appear in the absence of peripheral neuropathy.