The Head Retraction Reflex in Niemann-Pick Type C: A Novel Diagnostic Clue.

Background: The head retraction reflex (HRR) is characterized by the extension of the neck after percussion stimulation of the central facial region. It is either absent or habituates in normal individuals and can become exaggerated and persistent in certain pathological conditions, having been most commonly reported in hyperekplexia and stiff-person syndrome disorders. It has not, however, been reported in Niemann-Pick type C (NPC), a lipid storage disorder with a variety of neurologic and systemic manifestations. The diagnosis of NPC is often delayed because of the rarity of the condition and the subtlety of clinical signs.

Cases: We present 3 consecutive cases of genetically confirmed NPC with a pathological HRR, which was not present in controls. Neurophysiological analysis showed findings suggestive of myoclonus of brainstem origin.

Conclusion: We propose that the presence of a pathological HRR, an easily performed clinical test, may provide a clue to the diagnosis of NPC.