Breathing and CMT

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Breathing Problems in CMT

by K.N. Chan MD, FRCPC

Diaphragms are the most important muscles for breathing. The function

of diaphragms requires stimulation by the phrenic nerves. Phrenic

nerve impairment leading to diaphragm weakness or paralysis is an

uncommon but severe, and potentially fatal condition if not

recognized. The key to making the right diagnosis is a high index of

suspicion for the presence of this condition. Of the hereditary

neuropathies, CMT disease or hereditary motor and sensory neuropathy

is undoubtedly the most common. CMT disease is characterized by

chronic degeneration of peripheral nerves and roots, resulting in

muscle wasting, beginning in the feet and legs and subsequently

involving the hands. The association of CMT disease with diaphragm

weakness resulting in major breathing difficulty was first reported

by us in 1985.

In 1985, my colleagues and I at Yale diagnosed a paralysed diaphragm

in a 72-year-old woman who had CMT for about 60 years. Looking back,

this patient had major difficulties with her breathing for about 10

years. Unfortunately, physicians caring for her did not appreciate

the possible link of CMT with phrenic nerve impairment and thus

diaphragm weakness or paralysis because it was not previously

reported. As a result of the paralysed diaphragm, this patient

suffered major complications in her heart and lungs and had impaired

mental function. Even when the diaphragms are not working, most

patients breathe reasonably well in the upright position with the

help of gravity and the other breathing (accessory) muscles in their

necks and chests. However, when they lie down the benefit of gravity

is lost and the work of breathing required of these accessory

breathing muscles increases. This is the reason why the very first

indication of diaphragm weakness is difficulty breathing lying down.

Over a period of time, months to years, the overworked breathing

muscles become tired. The consequence of that is inadequate breaths

which leads to a long-term deprivation of oxygen.

The effects of poor breaths and lack of oxygen can be summarized in

the following categories: (1) The major impairment in breathing and

oxygen intake is obviously at night during sleep when patients are

lying flat, and since the brain needs a good supply of oxygen, any

major drop in the oxygen supply will alert the brain. The response is

awakening of patients from sleep so they can sit up to breathe deeper

in order to get some oxygen into the blood. When these episodes occur

repeatedly during the course of 7-8 hours sleep, major deprivation of

sleep and rest follows. Because of these events during the night

time, patients with these sort of problems typically complain of

morning headaches, daytime sleepiness and poor mental function.

A long-term lack of oxygen means strains on the heart and lungs and

will lead to major impairment of the heart and lung functions. The

results are heart failure, presenting as swelling of the ankles, poor

exercise tolerance, generalized weakness, and in severe

cases, death.

Our patient experienced most of the adverse outcomes mentioned. over

a period of years, her breathing muscles became so weak that she was

found at home almost dead with major breathing difficulty on her own.

She was then put on a breathing machine and was transferred to a

chronic ventilator hospital because it was felt that she would never

come off the breathing machine and thus requires nstitutionalization.

However, after the diagnosis of a paralysed diaphragm was made, we

were able to remove the breathing machine from her during the day and

put her in an upright position to maximize the benefit of gravity. At

night time, she is maintained on a simple breathing machine, which

she learned to operate on her own in a short period of time.

Currently, I am delighted to report that our patient is living on her

own at home, functioning independently and can finally breathe after

10 years of agony.

Since there was nothing in the medical literature on diaphragm

impairment or breathing problems in CMT, we decided in the fall of

1985 to conduct a series of lung and diaphragm tests on the brother

of our patient. He also has had CMT for about 45 to 50 years. To our

surprise, even though he has minor difficulty with his breathing, his

diaphragm turned out to be substantially weaker than most healthy

individuals in his age group. That is why we became concerned that

diaphragm weakness leading to breathing difficulties may actually be

a late and perhaps rare complication in people with CMT. And

especially in those individuals who have other medical problems that

may affect the phrenic nerves and/or the diaphragm, such as diabetes.

With the collaboration of Mrs. Carol Barker of Connecticut, we have

assessed two additional people with CMT in the State of Connecticut,

one of these also had significant weakness of her diaphragm although

it was much less severe compared to our index

patient. After presenting these observations at the American College

of Chest Physicians annual scientific meeting in September of 1986,

we are pleased to report that similar patients were seen by some of

our Chest colleagues in the United States.

References:

1. Chan CK, Mohsenin V, Ferranti R, Virgulto J, Loke J. Diaphragmatic

dysfunction in association with Charcot-Marie-Tooth disease and

diabetes mellitus. Chest 1986, 89: 454S.

2. Chan CK, Mohsenin, V, Loke J, Virgulto J, Sipski ML, Ferranti R.

Diaphragmatic dysfunction in siblings with hereditary motor and

sensory neuropathy (Charcot-Marie-Tooth disease). Chest 1987, in

press.