You have an elderly man with gait disturbance, discover B12 deficiency which fits the clinical picture of afferent ataxia, substitute it, he gets better. Then your attending comes along, thrusts his Rydel-Seiffer-fork at the malleoli, comes up with 5/8 and wonders whether your diagnosis is correct. How can that be?
We discuss the peculiar neuroanatomy of vibration sense (as opposed to proprioception) as described in
- Brazis Localization in Clinical Neurology
- this publication in JNNP 2002 refers.
We also mention the best way to measure pallesthesia (repeatedly, over skin vs. bone – the former being more sensitive), the bad interobserver reliability of Rydel-Seiffer-fork measurements and indications for doing pallesthesia in your average ER patient. Quite similarly we debate the various ways to examine joint position sense and why it is different from kinesthesia.