Sleep disturbances in chronic progressive external ophthalmoplegia

CPEO
Chronic progressive external ophthalmoplegia (CPEO) is a rare mitochondrial
disorder primarily affecting extraocular muscles (1). This results in drooping
of the eyelids and limited ocular mobility. Since intracellular energy
production is decreased in mitochondrial disorders, involvement of multiple
other organ systems (cerebrum, cerebellum, skeletal muscles, cochlea, retina,
peripheral nerves and heart) is common. CPEO often causes severe limitations in
all day activities. An earlier (unpublished) study conducted by our department
revealed, that these limitations are mainly caused by severe fatigue: two third
of all CPEO patients met the criteria for severe fatigue.

Fatigue
The cause of this fatigue is not completely understood. One can speculate, that
fatigue is a direct consequence of intracellular energy depletion. On the other
hand, fatigue could be the result of impaired nighttime sleep. To test this
hypothesis, we used a set of questionnaires to assess the quality of sleep in
33 CPEO patients currently under treatment in our department. 8 patients (24%)
had excessive daytime sleepiness, 26 patients (76%) regularly struggled to stay
awake. Furthermore, we screened for common sleep disturbances: restless leg
syndrome (RLS) was present in 10 patients (29%) and 8 patients (24%) had
complaints of obstructive sleep apnea syndrome (OSAS).

Sleep disturbances
This questionnaire study suggests, that sleep disturbances are common in CPEO.
However, quantification of these disturbances requires nighttime sleep
monitoring. Since RLS and OSAS are both treatable conditions, the ultimate goal
of this study is to reduce daytime fatigue by optimizing nighttime sleep.

Using a nighttime sleep recorder, we want to answer the following questions:
1. description of sleep quality (duration, efficiency and structure of various
stages of sleep)
2. quantification of specific sleep disturbances (RLS, OSAS and periodic limb
movement disorder)

Nighttime sleep will be monitored using a compact, portable recorder. All
patients are visited at home and the recorder will be connected though
electrodes on the head and a number of muscles. Respiration is monitored using
flexible belts around the chest and abdomen and through a sensor placed near
the nose. After they are connected to the recorder, patients can move without
limitations. There are no invasive procedures.
After one night of recording, results are analyzed using specific software.
Sleep stages are ranked according to the Rechtschaffen en Kales criteria (2).
In addition, we quantify apnea/hypopneas as well as periodic limp movements.
Endpoints are sleep latency, sleep efficiency and number of arousals,
apnea/hypopnea-index and number of desaturations.

This study does not carry any risks for its participants. Connecting the
monitor as well as recording nighttime sleep is generally not considered
uncomfortable.