Palmomental reflex

The palmomental reflex (PMR) is a primitive reflex consisting of a twitch of the chin muscle elicited by stroking a specific part of the palm. It is present in infancy and disappears as the brain matures during childhood but may reappear due to processes that disrupt the normal cortical inhibitory pathways. Therefore it is an example of a frontal release sign.

Research

Marinesco and Radovici in their seminal paper hypothesize that both the afferent (receptive) and efferent (motor) arms of the reflex are on the same side (ipsilateral) to the hand stimulated;[1] however this hypothesis remains unsubstantiated.[2]

The PMR has been found to be present more frequently in various neurological conditions both localized and diffuse. These include congenital conditions such as Down's syndrome where it is unclear whether the reflex persists throughout life or disappears and then re-appears in association with the onset of Alzheimer's disease pathology. The reflex is common in the elderly population and should not be taken as indicative of a dementing process.[2]

Eliciting and observing response

The thenar eminence is stroked briskly with a thin stick, from proximal (edge of wrist) to distal (base of thumb) using moderate pressure. A positive response is considered if there is a single visible twitch of the ipsilateral mentalis muscle (chin muscle on the same side as the hand tested).[2]

Localizing value

A study set in a neurosurgical in-patient population showed there is no significant association between the side of the reflex and the side of the hemispheric lesion in patients with unilateral (one-sided) reflexes and unilateral (one-sided) lesions.[3]

Primitive reflexes such as the PMR were classically viewed as signs of disorders that affect the frontal lobes, however this traditional view is questionable as the reflex has been noted for example in cases of one-sided temporal lobe pathology.[2][3]

A presentation at the 19th Meeting of the European Neurological Society suggests a possible link between presence of the PMR with stroke. Patients with the PMR present had a significantly higher incidence of silent ischemic strokes than matched patients who did not have the reflex present.[4][5]

References

  1. ↑ Marinesco G, Radovici A (1920). "Sur un reflexe cutane nouveau: reflexe palmo-mentonnier". Rev Neurol 27: 237–40.
  2. ↑ 2.0 2.1 2.2 2.3 Owen G, Mulley GP (2002). "The palmomental reflex: a useful clinical sign?". J. Neurol. Neurosurg. Psychiatr. 73 (2): 113–5. doi:10.1136/jnnp.73.2.113. PMC 1738000. PMID 12122165.
  3. ↑ 3.0 3.1 Gotkine M, Haggiag S, Abramsky O, Biran I (2005). "Lack of hemispheric localizing value of the palmomental reflex". Neurology 64 (9): 1656. doi:10.1212/01.WNL.0000160525.50482.C7. PMID 15883341.
  4. ↑ 19th Meeting of the European Neurological Society: Abstract P382. Presented June 23, 2009
  5. ↑ Gandey, Allison (June 2009). "ENS 2009: Palmomental Reflex May Signal Silent Stroke". MedScape Today. Retrieved May 2010.

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