Reply to "Sleep disorders in Charcot-Marie-Tooth disease type 1".
We read with great interest the paper by Boentert et al.  regarding the prevalence of sleep disorders in Charcot-Marie-Tooth (CMT) 1A patients. The Authors found the presence of Restless Leg Syndrome (RLS) in about 50% of patients with different forms of CMT, including CMT1A, CMT1B and CMTX. Considering these results the Authors conclude that RLS is highly prevalent not only in axonal subtypes of CMT but also in primarily demyelinating subforms of CMT . Our experience confirms a significant association of RLS with demyelinating neuropathies including inflammatory neuropathies, as chronic inflammatory demyelinating neuropathy (CIDP), or inherited neuropathy, as CMT1A. We found the presence of RLS in 6/26 (23%) patients with CIDP and 4/14 (28%) patients with CMT1A (Luigetti et al., in press http://www.aasmnet.org/jcsm/AcceptedPapers.aspx ). Interestingly, we have not noted any significant association between RLS and hereditary neuropathy with liability to pressure palsy (HNPP) that is another form of demyelinating inherited neuropathy that shares a common genetic origin with CMT1A, being caused by the deletion of the same region of chromosome 17 that is duplicated in CMT1A. Probably in HNPP, where peripheral nerves are only more susceptible to external noxious stimuli, the somato-sensory pathway is generally preserved, thus explaining the absence of an increased prevalence of RLS in this condition. One major issue in evaluating the prevalence of RLS in neuropathies is the tool used for the diagnosis. In their paper, Boentert et al.  applied the criteria proposed by Allen et al. , even though the Authors do not specify how many of the four requested criteria should be met to confirm the diagnosis. In a previous paper, addressing the association between RLS and neuropathies, different criteria were applied: i.e. Hattan et al.  "considered any subject who responded positively to three of the four questions to be screen-positive for RLS." The decision to assess RLS by the presence of three rather than all four criteria can lead to over esteem the prevalence of RLS in a cohort of neuropathic patients. Larger multicenter studies, based on widely accepted diagnostic criteria, are needed to evaluate the strength of the association between RLS and neuropathies.
Marco Luigetti and Giacomo Della Marca. Institute of Neurology, Catholic University of Sacred Heart, Rome-Italy
1) Boentert M, Knop K, Schuhmacher C, et al. Sleep disorders in charcot-marie-tooth disease type 1. J Neurol Neurosurg Psychiatry 2013
2) Gemignani F, Marbini A, Di Giovanni G, et al. Charcot-marie-tooth disease type 2 with restless legs syndrome. Neurology 1999;52:1064-6.
3) Luigetti M, Del Grande A, Testani E, et al. Restless leg syndrome in different types of demyelinating neuropathies: A single-centre pilot study. Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine in press
4) Allen RP, Picchietti D, Hening WA, et al. Restless legs syndrome: Diagnostic criteria, special considerations, and epidemiology. A report from the restless legs syndrome diagnosis and epidemiology workshop at the national institutes of health. Sleep Med 2003;4:101-19.
5) Hattan E, Chalk C, Postuma RB. Is there a higher risk of restless legs syndrome in peripheral neuropathy? Neurology 2009;72:955-60.
Conflict of Interest: