Autonomic cardiac regulation during spontaneous nocturnal hypoglycemia in patients with type 1 diabetes.

OBJECTIVE: Experimental clamp studies have suggested that hypoglycemia evokes a reduction of cardiac vagal control in patients with type 1 diabetes. However, there are limited data on the influence of spontaneous nocturnal hypoglycemia on cardiac autonomic regulation. RESEARCH DESIGN AND METHODS: Adults with type 1 diabetes (n = 37) underwent continuous glucose monitoring via a subcutaneous sensor as well as recording of R-R interval or electrocardiogram for 3 nights. Heart rate (HR) variability was analyzed during periods of hypoglycemia (glucose <3.5 mmol/L) (minimum length of 20 min) and a control nonhypoglycemic period (glucose >3.9 mmol/L) of equal duration and at the same time of night. RESULTS: The duration of hypoglycemic and control episodes (n = 18) ranged from 20 to 190 min (mean 71 min). HR (62 ± 7 vs. 63 ± 9 beats per min; P = 0.30) or the high-frequency component of HR power spectrum (2,002 ± 1,965 vs. 1,336 ± 1,506 ms(2); P = 0.26) did not change during hypoglycemia. Hypoglycemia resulted in a significant decrease in the low-frequency component of HR variability (2,134 ± 1,635 vs. 1,169 ± 1,029 ms(2), respectively; P = 0.006). The decline in the glucose concentration displayed a significant positive correlation with the decrease of the low-frequency component of HR variability (r = 0.48; P = 0.04). The latter was closely related to an increase in muscle sympathetic nerve activity recorded in 10 subjects during controlled sympathetic activation. CONCLUSIONS: Spontaneous nocturnal hypoglycemia in patients with type 1 diabetes results in a reduction of the low-frequency component of HR, which is best explained by excessive sympathetic activation without a concomitant withdrawal of vagal outflow.

Shoulder pain and an isolated teres minor nerve lesion.

The finding of isolated teres minor denervation during examination of the shoulders using MRI occurs in 3% to 5.5% of examinations. We describe eight patients with shoulder pain, in whom electromyography revealed an isolated lesion in the motor branch of the axillary nerve to the teres minor muscle. This nerve lesion is clinically impossible to diagnose, the lack of a clear diagnosis often resulting in inappropriate treatment and therefore potentially prolonged disability. Hence, when encountering shoulder problems, neurophysiologists should examine the teres minor muscle as a matter of routine. In the MRI and ultrasound examinations of patients with shoulder problems, therefore, not only routine tendon and joint structure but also muscles should be evaluated.