CMT and fatigue: Why are we so tired?
by Greg Carter, M.D., Medical Director, Providence Rehabilitation Hospital, Chehalis, WA, U.S.A.

Skeletal muscle weakness and loss of sensation are the ultimate causes of the majority of clinical problems associated with CMT. Fatigue in CMT is likely multifactorial and due, in part, to impaired muscular activation. Other contributing factors include generalized deconditioning from immobility and imposed sedentary lifestyle. Besides diffuse muscle weakness, atrophy and fatigue, there is also a reduced functional exercise capacity. Although these are common problems in CMT they have not been well quantified. We did one limited study about 10 years ago. We took 12 adult subjects with CMT type I, and 10 subjects without CMT and measured pulmonary (breathing) function, including tidal volume (VT), respiratory rate (RR), minute ventilation (Ve), oxygen uptake (VO2), oxygen saturation (SaO2), carbon dioxide production (VCO2), inspiratory flow (VT/Vi), and heart rate (HR). We then administered the Lee Fatigue Scale, the Lareau Functional Status Scale, Borg Perceived Exertion Scale, and the Profile of Mood States (POMS) measured before and after unsupported arm exercise (UAE). Results showed fatigue was moderate to severe and functional state was reduced compared to subjects without CMT. This was true both before and after exercise, with significant increases in fatigue reported post exercise. Our findings indicated that people with CMT have elevated fatigue intensity and distress before and after exercise. Functional state is also much lower in CMT.

Pain, and occasionally, depression, can also contribute to fatigue or the sense thereof. Some reactive clinical depression is expected in CMT if there is significant loss of function. Good family, social, and religious support systems are helpful in this regard. Anti-depressant medicine should be considered since it may provide assistance with energy levels, mood-elevation, appetite stimulation and sleep. Aerobic exercise not only improves physical functioning but is beneficial in fighting depression and improving pain tolerance, two things that are critical in CMT. There have been few well-controlled studies looking at exercise induced strength gains in CMT. My colleague Dr. Dave Kilmer had CMT subjects do a 12 week moderate resistance (30% of maximum isometric force) exercise program which resulted in strength gains ranging from 4% to 20% without any notable deleterious effects. However, in the same population, a 12 week high resistance (training at the maximum weight a subject could lift 12 times) exercise program showed no further added beneficial effect compared to the moderate resistance program and there was evidence of overwork weakness in some of the subjects. The risk for overwork weakness is great in CMT and exercise should be prescribed cautiously and with a common sense approach. People with CMT should be advised not to exercise to exhaustion, which can produce more muscle damage and dysfunction. The warning signs of overwork weakness include feeling weaker rather than stronger within 30 minutes post exercise or excessive muscle soreness 24-48 hours following exercise. Other warning signs include severe muscle cramping, heaviness in the extremities, and prolonged shortness of breath. Nonetheless, gentle, low impact aerobic exercise like walking, swimming, and stationary bicycling will improve cardiovascular performance and increase muscle efficiency, and thus help fight fatigue.

Up until a few years ago, pain was not frequently characterized as a major component of CMT. However a study sponsored, and funded in part by CMT International, showed that the majority of people with CMT do experience significant pain. The pain is due largely to damaged nerves causing "neuropathic pain" (stinging, burning). However, immobility, which can cause adhesive capsulitis, mechanical back pain, and pressure areas on the skin also likely contribute. Chronic pain can be immensely fatiguing and it would be helpful for those with chronic pain to have it treated aggressively. Pharmacological management of pain in CMT includes the use of non-steroidal anti-inflammatory (NSAID) medication, particularly if there is evidence of active inflammatory process like tenosynovitis or arthritis. Regular dosing of acetaminophen (1000 mg every 6 hours) may be used along with an NSAID or alone if NSAIDs are not tolerated. Anti-depressants and anti-convulsants (neurontin) are particularly helpful for neuropathic pain. Narcotic medicine should also be considered for refractory pain. If narcotics have helped, then taking the total dose of immediate release (short acting) narcotic required to alleviate pain and giving half of that every 12 hours in a controlled-release preparation such as OxyContin may be helpful.

Proper equipment is crucial to maintaining energy. Braces (ankle-foot orthoses, etc) should fit well and be in good repair. Wheelchairs should have adequate lumbar support and good cushioning (gel-foam). The chair should be properly fitted (generally done by occupational therapist) to avoid pressure ulcers and inadequate support for the spine. Wheeled walkers (Gran Tour in particular) or quad (four point) canes may also help, depending on the pattern of weakness. Some may benefit from Canadian style forearm crutches to steady them. Other useful equipment includes hand-held showers, bathtub benches, to shower and toilet grab bars (Versa frame), raised toilet seat, automatic toileting device, hospital bed, commode chair, ADL aids (sock aid, grabbers, etc), and wheelchair ramps. An occupational therapist will help define which, if any, of these devices will be useful to the patient. They can also go over pacing and energy conservation techniques.

Respiratory failure occasionally will develop in CMT, due to weakness of the diaphragm, chest wall, and abdominal musculature. This is usually manifested by hypoventilation, which leads to elevated carbon dioxide levels in the blood. This will cause fatigue. A thorough review of systems by your physician will help define any problems. Patients that are hypoventilating will often complain of a morning headache, restlessness or nightmares, and poor quality sleep. This may cause daytime somnolence and fatigue. Dr. John Bach has shown significant success with the use of intermittent positive pressure ventilation by mouth (IPPV). This type of ventilation does not require a tracheostomy and may markedly improve quality of life. IPPV can be done easily in the home and should be considered in people with CMT and respiratory failure or sleep apnea. Patients may benefit initially from using IPPV mainly at night. (See also under the heading Breathing)

Note from Linda Crabtree: - Dr. Carter didn't mention grief. We can be constantly grieving for our physical losses mobility and grief can cause depression. Both grief and depression can cause fatigue. Grief counselling can often help get you back to a full happy life.

Stress can also make you very tired. Living with constant stress from family, stress in the workplace or just pressure to perform beyond your limits (like working two jobs) can take its toll. Constantly pushing ourselves to perform every day can mean that our bodies are always exhausted. Being exhausted all the time means we never give our nerves time to try to repair themselves and our muscles will atrophy as we push ourselves. Over time a pattern of prolonged abuse and overuse can see muscles permanently atrophied although they can atrophy with normal use as well.
Nervous exhaustion can also take place. Some of us have exceptionally low tolerances to noise and odor, taste and touch as well as chemicals. Knowing what you cannot tolerate and avoiding it as much as possible will help you stay on an even keel. Knowing what makes you tired and learning to pace yourself is the key to living with CMT.