The best magazine
In the paper by Boentert et al the authors report an increased incidence of obstructive sleep apnoea (OSA), restless leg syndrome (RLS) and periodic limb movements in sleep (PLMS) in a study of 61 patients with Charcot-Marie-Tooth disease type 1 (CMT1) (mostly CMT1A) compared to a control group of insomnic patients. OSA was reported in almost 38% of patients (5% controls) with a male preponderance and RLS in 41% (16% controls) with a female preponderance. Although PLMS was common (41% of CMT1 patients), it did not reduce sleep quality. The severity of OSA is measured by the apnoea–hypopnoea index (AHI), the number of apnoea spells per hour, and in this study, the AHI was significantly related to the score used to measure neurological disability, the functional disability scale (FDS). The use of a control group of insomnic patients was interesting as this group, not surprisingly, had reduced sleep quality as did the CMT1 patients, but the proportion of CMT1 patients with excessive daytime sleepiness and fatigue was higher. It is important to note that the prevalence of sleep apnoea in patients with CMT1 in this study exceeds previously reported prevalence figures in the normal population. The authors in this study and in a previous study suggest that the increase in OSA due to CMT1 may be due to the pharyngeal neuropathy. The correlation of the AHI with the FDS lends support to this theory as the disability in CMT1A is inversely related to the size of the motor amplitudes.
The major interest of this paper is in how much the OSA in particular and the RLS contribute to fatigue, which is a major complaint of CMT patients. The complaint of fatigue includes a general lack of energy and a tendency to become easily exhausted. Although there are many potential explanations for this, none are entirely satisfactory and the answer is likely to be multifactorial. Patients clearly require more energy and concentration to walk safely due to leg weakness, and in some cases, proprioceptive loss, and consequently, need to be constantly alert to impediments that make falling more likely. Patients also tend to be less aerobically fit, which again is likely to impact on fatigue. The relevance of determining how much of the fatigue is due to OSA is that this is treatable with continuous positive airway pressure (CPAP). It will be important going forward to specifically study the effect of CPAP treatment for OSA in CMT1 patients on fatigue as this has the potential to help a large number of patients.
RLS can also respond to symptomatic treatment with dopaminergic agents and since the current study showed an association of RLS with worse sleep quality and fatigue, it needs to be determined whether patients with CMT1 and RLS also respond to dopaminergic agents and whether this helps their fatigue.
The clear message from this paper is that clinicians caring for patients with CMT1 need to regularly assess patients for symptoms of sleep apnoea and RLS.
Source: ...