The association between Duchenne muscular dystrophy and intellectual impairment has long been recognized. Many studies have shown that the mean intelligence scores have generally averaged about 85, one standard deviation below the mean of the general population. Investigators usually agreed that this decreased intellectual functioning is related to the influence of some physiologic parameter of the disease rather than secondary to psychosocial factors.

However there is no consistent findings with regard to the existence of intellectual impairment in muscular dystrophic patient and the course and type of intellectual dysfunction.

The purpose of this study is to know over-all level of intellectual function of muscular dystrophic patients, particular pattern of intellectual functioning and changes of above feature according to age and degree of severity.

The results of these studies were as follows;

1) The mean intelligence scores of Duchenne, facioscapulohumeral, limb-girdle and myotonic muscular dystrophy were 81.6±17.0, 111.0±4.0, 106.8±10.5 and 85.4±21.0 respectively.

2) Verbal intelligence score was significantly lowered than performance score in Duchenne muscular dystrophy.

3) The frequency of mental retardation was 24% in Duchenne type.

4) Patients with family history tended to score better than those without family history in Duchenne type.

5) Verbal intelligence score was not changed with age but performance intelligence decreased in the older group in Duchenne type. This suggest that impairment of verbal intelligence was early and non-progressive, where as performance intelligence decreased as the disease progress.