The Three Nociceptive Responses of the Orbicularis Oculi Reflex in Alzheimer’s Disease: State of the Evidence and Meta-analysis

There is an emerging belief that electrically elicited blink reflexes (BR) may distinguish Alzheimer’s disease (AD) from other disorders characterized by memory dysfunction. To qualitatively and quantitatively distinguish the effects that electrical stimulation has over the blink reflex (eBR) recorded from patients with AD and healthy controls (HCs), we did a systematic review of the literature, and conducted a meta-analysis. Following our selected criteria, 94 AD patients and 97 HCs were identified from articles published in English between 1950 and 2017. Although the 3 responses (R1, R2 and R3) of the eBR were studied in a number of patients, only the R2 response was quantified in all studies. Thresholds and stimulation intensities parameters were found to be used in a miscellaneous form, and the majority of times, such parameters deviated from validated guidelines. The stimulation frequencies used to elicit the BR responses ranged between 0.14 and 0.2 Hz. These frequencies favored HCs compared with AD patients (odds ratio = 1.08; 95% CI = 0.30-1.85), I2 = 0% [ P = .99]; Q = 271.89 [ df = 7, P < .000]). Egger’s regression test suggested publication bias (intercept = 32.38; 95% CI = −8.98 to −3.2; P = .001). Our results unveiled key shortcomings in the data reported; such shortcomings need to be corrected in future AD research looking for obtaining more reliable and reproducible eBR studies; otherwise, interventions may be misleading.

Neurinoma of the Trigeminal Root Presenting as Atypical Trigeminal Neuralgia: Diagnostic Values of Orbicularis Oculi Reflex and Magnetic Resonance Imaging

A case of trigeminal root neurinoma presenting as atypical trigeminal neuralgia was reported. The orbicularis oculi reflex was absent on the affected side, but reappeared after operation. The demonstration of the tumor was much clearer on magnetic resonance imaging. The usefulness of these electrophysiological and radiological studies in differentiating varied entities of trigeminal neuralgia is stressed. (Neurosurgery 21:733-736, 1987)

Contralateral Trigeminal Nerve Dysfunction as a False Localizing Sign in Acoustic Neuroma: A Clinical and Electrophysiological Study

A 49-year-old woman presented with right facial sensory impairment due to trigeminal nerve dysfunction caused by a contralateral acoustic neuroma. The mechanism of the falsely localizing trigeminal involvement is probably displacement and distortion of the brain stem by the large mass lesion and not increased intracranial pressure. A preoperative orbicularis oculi reflex study was abnormal and indicative of right trigeminal nerve dysfunction; after surgical removal of the tumor, the orbicularis oculi reflex study was normal. We conclude that a false localizing sign of trigeminal nerve dysfunction can occur rarely on the contralateral side in patients with large posterior fossa tumors, especially tumors arising from the cerebellopontine angle, and should be considered in the differential diagnosis of hemifacial sensory disturbance.