A preliminary report on the use of laser-Doppler flowmetry during tethered spinal cord release.

Neurological deterioration in the tethered cord syndrome has been postulated to result from a compromise of blood flow in the distal spinal cord. In order to evaluate vascular perfusion in human subjects, a new technique of laser-Doppler flowmetry was used to monitor continuously the microcirculation of the distal spinal cord during surgery for tethered cord release in 10 children. For further comparison, five children undergoing selective dorsal rhizotomy were also monitored. In the tethered cord syndrome group, spinal cord blood flow before untethering was a mean of 12.6 ml/min per 100 g of tissue and increased in all cases after release to a mean of 29.4 ml/min per 100 g of tissue. All patients improved neurologically. The selective dorsal rhizotomy group had a preoperative mean spinal cord blood flow of 30.8 ml/min per 100 g of tissue, which was not altered by the operative procedure. Significant improvement occurs in distal spinal cord blood flow after tethered cord release, which may be representative of an important mechanism in the pathophysiology of the tethered cord syndrome.

Evaluation of intraoperative somatosensory-evoked potential monitoring during 100 cervical operations.

Continuous intraoperative somatosensory-evoked potential monitoring during scoliosis surgery, along with improved instrumentation techniques, has contributed to the reduction of neurologic injury from 4-6.9% to 0-0.7%. To assess whether somatosensory-evoked potential monitoring might play a similar role in cervical surgery, the authors compared the morbidity and mortality rates associated with 218 patients who were not monitored and were operated on between 1985-1989 with those found in 100 consecutive somatosensory-evoked potential monitored procedures done from 1989-1991. The cervical procedures were conducted for disc disease, stenosis, spondylosis, and ossification of the posterior longitudinal ligament. Eight of 218 unmonitored patients became quadriplegic (3.7%) and 1 died (0.5%); no instances of quadriplegia and no deaths were encountered among the 100 monitored patients. The reduction of neurologic deficit was attributed in part to early somatosensory-evoked potential detection of vascular or mechanical compromise of the spinal cord or nerve roots and to the immediate alteration of anesthetic or surgical technique in response to somatosensory-evoked potential changes, i.e., reversal of systemic or "relative" hypotension, adjustment of operative position, release of distraction, and cessation of manipulation. Continuous intraoperative somatosensory-evoked potential monitoring also was a practical tool in monitoring cervical surgery.

Making a difference: the osteopathic approach lecture series.

The Osteopathic Approach Lecture Series (Osteopathic AppLeS) was created in response to both the current need in the osteopathic medical profession for a distinctive osteopathic identity and lack of readily available information regarding an osteopathic approach. The series consisted of 16 lectures given to interns, externs, residents, and attendings at a community-based osteopathic hospital during a 10-month time span which emphasized and inculcated an osteopathic approach to patients with a variety of illnesses. Emphasis was placed on osteopathic manipulative treatment training throughout the series. Data were collected at individual presentations using a survey of participants and studied retrospectively. The results of the surveys indicated that using this type of presentation series may substantially increase confidence and knowledge in an osteopathic approach and osteopathic manipulative treatment skills.

Auditory effects of noise on infant and adult guinea pigs.

This pilot study compared the susceptibility of the infant (48 hr) and adult (120 days) guinea pig to the effects of noise. Subjects were exposed to a narrow band of noise (center frequency 4 kHz) at an intensity of 115 dB sound pressure level (SPL) for 1 hr. Postexposure thresholds were obtained by a conditioned suppression technique. Results indicated that the infant animals displayed a mean hearing threshold of 25 dB SPL that significantly differed from the adult mean threshold of 7.5 dB SPL.

A new technique using somatosensory evoked potential guidance during descending and thoracoabdominal aortic repairs.

Recent work in our laboratory has demonstrated the effectiveness of somatosensory evoked potentials (SEPs) in identifying the critical intercostal arteries (CICAs) for preserving spinal cord integrity during simulated aortic aneurysm repairs in the pig. Further studies have also demonstrated increased preservation of neurological function during prolonged aortic clamping if CICAs are perfused until ligation or clipping, as opposed to transaortic identification of back-bleeding intercostals and their subsequent ligation. We have developed a technique of repair of descending thoracic and thoracoabdominal aortic aneurysms and dissections that uses these principles. Since January 1993, 26 patients have undergone repair of their aortas using this new technique and SEP directed intercostal artery ablation. There were 22 (85%) long-term survivors among 10 thoracoabdominal and 16 descending aortic repairs. All patients with uncorrected abnormal SEP recordings developed paralysis; one patient who required reimplantation of an intercostal artery island into the aortic graft had normal neurological function postoperatively. Paraplegia was seen in only one of the surviving patients, but this patient had normal intra- and postoperative SEPs (4% false negative). Our experience suggests that SEP-guided obliteration of intercostal arteries while maintaining perfusion may be a useful approach to the surgical repair of descending and thoracoabdominal aortic disease.