[Central nervous system disorders in patients with myotonic dystrophy--in relation to respiratory dysfunction]

Although central nervous system (CNS) involvement, such as intellectual impairment simulating dementia, in myotonic dystrophy (MyD) has been well documented, the cause of this condition remains unclear. In has been reported that the progressive cases of MyD are often accompanied with respiratory disturbance and sleep apnea syndrome (SAS). We studied the relation between CNS involvement and respiratory disorders in 15 MyD patients. They consisted of 10 males and 5 females with ages ranging from 21 to 58 years (average 46 +/- 8.4 years old). Arterial blood gas (ABG) analysis, respiratory function test, and monitoring of arterial oxygen saturation (SaO2) during sleep were carried out. In some cases abnormal respiration during sleep was analyzed with polysomnography. For an assessment of CNS involvement the following examinations were performed; intelligence quotient (WAIS-IQ); electroencephalography (EEG); brain computed tomography (CT); and cerebrospinal fluid (CSF) levels of neuron-specific enolase (NSE), S-100b and creatine kinase BB isoenzyme (CK-BB) which were estimated by using enzyme immunoassay. ABG analysis demonstrated the presence of hypercapnia (PaCO2 > 45 torr) during wakefulness in MyD patients. During sleep 14 of the 15 patients showed frequent desaturation phenomenon (SaO2 < 90%), indicating the episodic hypoxemia. Polysomnographic study revealed the occurrence of SAS of both obstructive and central types in all the cases examined. IQ test disclosed intellectual impairment in 80% of the 15 patients, and EEG showed slowing of basic rhythm in the majority of the cases. On brain CT both enlarged ventricles and dilated sulci were commonly observed.(ABSTRACT TRUNCATED AT 250 WORDS)