Medical Mystery of the Week

Because of the COVID19 pandemic, you are practicing telemedicine. You are asked to interpret the significance of a test being performed on a 78-year-old man (see video below). What is your diagnosis, what additional tests would you do to confirm your suspicions, and what treatment, if any, do you recommend?

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DIAGNOSIS: Positive snout reflex, a puckering or protrusion of the lips elicited by tapping the midline of the upper lip as shown in the video.

The snout reflex is one of many nociceptive primitive reflexes (npr) normally present in newborn infants; these include, but are not limited to the snout, suck, glabellar, palmomental, grasp, gegenhalten (an oppositional involuntary paratonia), and startle (Moro) reflexes. The presence of these automatisms in the newborn infant is attributable to a lack of complete myelination of the central nerrvous system, most particularly the cerebrum, brainstem, and corticospinal tracts; myelination of these areas is not complete until the second year of life. Hence the presence of primitive reflexes in newborn infants is normal whereas their presence in late childhood and adults is abnormal. Camarda and associates studied the prevalence and significance of three npr - the glabellar tap, snout reflex and palmomental reflex - in 1,246 neurologically and cognitively healthy aging subjects (age range 41-95 years) each of whom had undergone a brain MRI. Npr were present in 33.5% of subjects (snout > glabellar > palmomental) and increased with age. Subjects with npr performed less well than subjects without npr on tests evaluating global cognition, executive functions, attention, and language. A positive glabellar tap was associated with parieto-temporal white matter hyperintensities (WMH), abnormal bicaudate ratios (BCr) and lateral ventricles to brain ratios (LVBr). The snout reflex - as seen in the presented case - was associated with frontal lacunes (small infarcts), temporal WMH, BCr, and LVBr, and the palmomental reflex was associated with parieto-occipital WMH, basal gangion lacunes, BCr, and LVBr. The authors conclude that any patient with npr should manage their vascular risks/vascular diseases rigorously in order to prevent/delay progression of small vessel disease and future cognitive and neurological disabilities [1]. This study is of paramount importance, since many clinical studies unaccompanied by brain imaging imply that npr can be a normal finding in aging subjects.

[1]. Camarda C, Torelli P, Pipia C, Azzarello D, Battaglini I, Sottile G, et. al. Nociceptor primitive reflexes in neurologically and cognitively healthy aging subjects. Can J Neurol Sci. 2019;46(2):199-208.