Differential control of the scapulothoracic muscles in humans.

The control of the scapulothoracic muscles trapezius (Tr) and serratus anterior (SA) has been examined in normal human subjects. Electromyographic recordings were made from the SA and Tr muscles (upper trapezius UTr, lower trapezius LTr) using surface electrodes placed bilaterally. Magnetic stimulation of the motor cortex and electrical stimulation of peripheral nerves were used to examine their descending and reflex control. The average optimal site of cortical stimulation was found to be the same for SA, UTr and LTr (an approximate centre of gravity of -0.6 cm, 3.7 cm where the centre of gravity is expressed as the mean anterio-posterior position, the mean medio-lateral position). Some asymmetry in the cortical representation of UTr was found in each individual tested. Magnetic stimulation evoked bilateral MEPs in Tr (latency contralateral (c) UTr 8.5 +/- 1.6 ms, ipsilateral (i) UTr 19.0 +/- 2.7 ms) but only contralateral responses were evoked in SA (11.2 +/- 2.6 ms). Electrical stimulation of the long thoracic nerve at two sites was used to examine homonymous and heteronymous reflexes of SA, while electrical stimulation of cervical nerve of C3/4 was used to examine the heteronymous reflexes of Tr. Ipsilateral SA H reflexes were evoked at a latency of 9.9 +/- 0.8 ms (proximal site) and 10.8 +/- 1.2 ms (distal site). No group I reflexes were evoked from SA to its contralateral homologue. No group I reflexes were evoked between Tr and SA. Finally, cross-correlation of activity from the Tr muscle pairs and the SA muscle pair revealed that the motoneurones of the Tr muscles share some common presynaptic input whereas there was no detectable common presynaptic input to the SA muscle pair. This study extends and consolidates knowledge regarding the neural control of trapezius and for the first time explores the neural control of SA. The study demonstrates a contrasting bilateral control of Tr and SA. These patterns of connections are discussed in relation to the contrasting bilateral functional roles of these muscles.

Functional modulation of shoulder girdle stability.

We have previously reported that electrical stimulation of the ulnar nerve at group I strength evokes reflex excitation of the trapezius muscle in normal human subjects. In the present study this reflex has been evoked while subjects were performing a number of different tasks. When subjects performed a task involving a high degree of manual dexterity, the reflex was larger. On the other hand, when subjects performed a task that can be achieved with virtually no movement of the hand or wrist musculature, the reflex does not appear to show any task dependency. These results support the view that in delicate tasks of the hand, such compensatory reflexes are more important than in basic mechanisms such as lifting an object. The functional consequences of these findings and their significance in relation to the possibility that these task-related reflex gain changes produce intention tremor is discussed.

Survival in patients undergoing tracheal sleeve pneumonectomy for bronchogenic carcinoma.

Thirty-four patients underwent tracheal sleeve pneumonectomy during the years 1964 through 1981. In 30 patients, simultaneous resection of the right lung and carina was performed with an anastomosis established between the left main bronchus and trachea. In four patients a previous pneumonectomy had been performed (two right and two left) and, because of recurrence in the stump, resection of the stump and carina was carried out with either right or left bronchotracheal anastomosis. Preoperative irradiation was given in 28 of the patients in the group, and tumor sterilization occurred in six of those so treated. Four of 30 patients are long-term survivors: Two are still alive and free of cancer at 7 and more than 11 years postoperatively. One patient in the group of four with stump recurrence is alive more than 11 years postoperatively. All long-term survivors had epidermoid carcinoma and all received preoperative irradiation. The most frequent complications were fistula formation and pneumonia, resulting in 10 deaths in the perioperative period for a mortality of 29%. The 5 year survival rate of the entire group was 15%, and the survival rate by life-table analysis in the 30 patients with lung and carinal resection was 13.3% at 5 and 8.8% at 10 years.