Management of Myotonic Dystrophy

This information is from the 11th annual conference of the English Myotonic Dystrophy

“Myotonic Dystrophy Incurable but not Unmanageable”

The incidence of Myotonic Dystrophy is 1 in 8000. Most general practioners have about 2000 patients in their practice. So by simple mathematics only one in four general practioners will see a patient with DM. Most will not know much about it. So it is necessary to have specialized centers for treatment. (Webmaster note: By implication the congenital form is about 1 in 100,000 so that only 1 in 50 pediatricians will have a patient with CMyD in their practice)

Most other muscular dystrophies will only affect the muscles. DM is different in that other systems are affected as well. Another difference is that with most other genetic diseases you either have the gene and the disease or you don’t. DM is a variable genetic disease. It severity differs with the age of onset and the number of repeats. There is not a distinct expression of the disease based on an on or off view. Thus, many medical practioners will have a harder time understanding the disease. The other implication is that you can not generalize the condition of one patient with the disease to another, it is variable

Skeletal Muscle: The skeletal muscle is defined by Myotonia of muscular stiffness, in particular hand stiffness. Also certain other muscles are weak especially facial, scapula and humorous muscles are mostly affected. However, this stiffness is generally not he problems that patients report more, it is the weakness of the hand and other muscles that comes into play. This is more the day to day problems that weaker muscles may cause. Weakness of the grip seems to be the most problematic. A normal male should be able to squeeze about an equivalent of 50Kg. A patient with DM may only be able to squeeze the equivalent of 10-1Kg for example. Also weakness of the ankle muscles causes the characteristic gait of DM. Dr. Jones mentioned that a patient of his was unable to blow into a breathalyzer machine So Dr. Jones felt it was more the practical issues of weakness more than the myotonia that affect DM patients

Smooth Muscles: One of the primary effects of DM on smooth muscle is that swallowing and feeding are much more difficult. What is generally recommended is that food should be cut into small pieces and drink used to wash this down. Care must be taken to avoid aspiration pneumonia, that is food going down into the lungs and causing pneumonia. Dr, Jones mentioned a drug Cysotia?? (Margaret can we get clarification here) or surgery that might be needed to assist. Also a video Fluoroscopy will help diagnosis any feeding problems.

The smooth muscles also affects the bowel and notably irritable bowel syndrome is very common in patients with DM. This is failure of coordination of muscles. Constipation is also a complication because of muscle problems plus immobility of patients not moving. Surgery is not recommend and Dr. Jones has heard reports of patient deaths with surgery. The Uterus is also affected and problems in childbirth may result.

The heart is affected in other dystrophies but in DM it is not the heart muscle itself that is affected. Rather, it is problems with the electrical signals not working properly and the heart either working to fast or too slowly. Atrial fibrillation is when part of the heart is not working efficiently, pumping to fast and not coordinated) and this can cause dizzy spells and blackouts, can be treated. The heart can also pump too slow causing the same symptoms. Heart changes are slow to respond to changes in the body. Dr. Jones recommended an EKG every year to look for problems.

Eyes and Ears: Cataracts can be the first evidence of myotonic dystrophy disease. Generally, if cataracts are seen in patients under 50 DM should be considered. There is nothing special about the mature form of cataracts. However, in the early stages there is a characteristic pattern that can be seen that is unique to DM. A mild degree of deafness is due to DM but not serious.

Brain. On average IQ is a little lower. In the congenital form IQ is reduced and most children will have learning disabilities. The mental problems are pretty static with little change over time.

Excessive Daytime Sleeping: 75% of DM patients have excessive sleepiness. In a survey they conducted 120 responses were received and 40% of patients had a pathological sleeping problem. There is a new drug Modafinil (Brand name Provigil in USA) that might help. Make sure to take it in the morning!

Breathing: The lungs are affected as well as the heart. The anesthesiologist should be informed as well as the surgeon prior to any surgery. Certain precautions must be taken. DM suffers should wear a bracelet as well as cards in case of an accident. The group had a handout on anesthesia that was in some of there earlier newsletters.

Endocrine System: There is reduced fertility in patients with DM. There is also diabetes. Dr. Jones didn’t feel that DM diabetes falls into the classical sense of Diabetes. Feels that all patients with DM have problems with sugar levels. (My note: Might possibly have a different Mechanism of action?). Would be nice to get some more information on this.

Dr. Jones feels that the age of onset is a more potent predictor of outcome versus the number of repeats. There is the anticipation factor where in each generation the outcome becomes progressively worse.

Genetic counseling: Family needs to be screened especially women to prevent them from unknowingly having an infant with CMyD. When an individual is identified strong efforts should be considered to have other family members tested to avoid them having CMyD. For example Dr. Jones considered an example of a 28 year old male who was confirmed diagnosis with DM. He had 2 sisters one 25 and one 21. The 21 year old sister went on to have a child with CMyD because she was not informed or tested.

Link to Article by Dr. Carter on Management of Neuromuscular Diseases

THE DIFFERENT TYPES OF MYOTONIC DYSTROPHY

Summary of the lecture by Christine E.M. De Die- Smulders MD of the University of Maastricht at the yearly meeting organised in October 1996 by the “Werkgroep Dystrophia Myotonica” for patients and other people involved in myotonic dystrophy. This lecture was meant for the new participants of this annual meeting.

Introduction

Myotonic Dystrophy (DM) is a relatively frequently occurring, hereditary muscular disorder. Characteristic symptoms are myotonia (muscle stiffness due to muscles failing to relax properly) and slowly progressive muscle weakness, especially of the face-muscles, the throat- and neck-muscles and the muscles in the fore-arm and lower part of the legs. Other organs may also be affected. This manifests itself in symptoms as cataract, irregular heart-beat, slowness, loss of initiative and infertility in males. There may be a considerable variation in the severeness among patients. The age at onset of the disorder and the character of the symptoms are highly depending upon the length of the expansion of the CTG repeat in the DM-gene.

Classification in four types according to age and main symptoms

1 Mild type

2 Adult (= classic) type

3 Childhood type

4 Congenital type

Adult type (2)

Age at onset: 12 – 50 years

Initial symptoms:

Muscle weakness

Myotonia
Later symptoms:

Increasing muscle weakness

Cataract

Slowness, loss of initiative

Defects in several organs

The adult (classic) type is the most frequently occurring type. Myotonia and muscle weakness develop from puberty till the age of 50. Myotonia is a painless muscle stiffness, notably affecting the hands after a firm grip. Complaints are: difficulties with letting loose a door-handle and after shaking hands or cramp when wringing out a cloth, especially in wintertime. The stiffness disappears spontaneously after a short time. Cold can evoke or stimulate this stiffness. Most patients are slightly troubled by myotonia and will not complain spontaneously about it.

The muscle weakness starts gradually and it may last for years before a patient consults a doctor. Weakness of face-muscles appears at an early stage: The eyelids hang down and when the patient is asleep part of the white of the eye stays visible. It is no longer possible to laugh broadly. Speech gets indistinct and it looks like the patient speaks “through his nose”. The temples shrink by the jaw-muscles getting thinner. The weakness of the bending muscles of the neck is often pronounced. Patients cannot raise their heads when lying down. The loss of power in the muscles of the fore-arm and hands makes together with the myotonia the hands clumsy. Regarding the muscles the lower part of the legs especially the raising of the feet is reduced: The patients start shuffling, stumble over minor roughness’ and fall more frequently. Sometimes next to these there are less specific complaints such as fatigue, lack of spirit, stomach-complaints or swallowing problems.

In a later stage of the disease the muscle weakness will increase and the muscles of the upper-arm and upper-part of the leg will be affected. Most patients however stay mobile if their radius of action is reduced till in and around their homes. Seldomly patients get bound to a wheelchair.

Mild type (1)

Age at onset: over 50 years

Initial symptom:

Cataract

Later symptoms:

Muscle weakness

Myotonia

The mild type starts after the age of 50. Most patients only get cataract. In a later stage mild muscle weakness and myotonia may appear. If the illness is unknown in the family it is seldom recognised that the cataract is part of a muscle-disease.

Congenital type (4)

During pregnancy:

Much amniotic fluid

Reduced fetal movements

At birth:

Muscle weakness

Problems with breathing and swallowing

Clubfeet

Weak face-muscles

First year of life:

Muscle weakness decreases

Baby learns breathing and drinking by him/herself

Slower development
After the first year of life:

Learn to walk (2 – 5 years of age)

Learn to speak (sometimes indistinctly)

Get cleanly

Problems with learning

Squinting

Inflammation of the ears

Problems with bowels

The congenital type shows severe muscle weakness and decreased muscle strength at birth which leads to problems with breathing and swallowing. During pregnancy there is much amniotic fluid (because the baby does not swallow) and the mother feels less stirring of the baby. A number of babies die because of breathing problems. If they survive they recover considerably from the muscle weakness during the first years of life, because of growth of the muscles. Indeed these children often have the characteristic tent-shaped mouth. The patients show a retarded motor development, which needs treatment by a physiotherapist. A majority of the children learns to walk between the age of 2 and 5 years. Bowel cramping and constipation often occur, just like inflammation of the inner ears. Besides there are problems with speaking, among others due to weakness of the palate. At adult age muscle stiffness and muscle weakness occur.

The mental retardation with this type is often mild to moderate. The children learn to speak and learn to take care of themselves, but mostly they do not learn to read and write. It is important to test the child in time and to choose the right type of school based on the testresults. Most children need special education. Take care that the child is not underestimated. Factors which may influence underestimation are the facial muscle weakness, the problems with speaking, poor hearing and slowness.

The congenital type is almost always passed on by an affected mother, seldom by an affected father.

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