Search PubMed⌕ Search

Biomedical subjects

C Strauss

Publications and source records attributed to C Strauss.

At least 37 records · Page 2Linked to original sources
PubMed2000

Continuous electromyography monitoring of motor cranial nerves during cerebellopontine angle surgery.

OBJECT: Electromyography (EMG) monitoring is expected to reduce the incidence of motor cranial nerve deficits in cerebellopontine angle surgery. The aim of this study was to provide a detailed analysis of intraoperative EMG phenomena with respect to their surgical significance. METHODS: Using a system that continuously records facial and lower cranial nerve EMG signals during the entire operative procedure, the authors examined 30 patients undergoing surgery on acoustic neuroma (24 patients) or meningioma (six patients). Free-running EMG signals were recorded from muscles targeted by the facial, trigeminal, and lower cranial nerves, and were analyzed off-line with respect to waveform characteristics, frequencies, and amplitudes. Intraoperative measurements were correlated with typical surgical maneuvers and postoperative outcomes. Characteristic EMG discharges were obtained: spikes and bursts were recorded immediately following the direct manipulation of a dissecting instrument near the cranial nerve, but also during periods when the nerve had not yet been exposed. Bursts could be precisely attributed to contact activity. Three distinct types of trains were identified: A, B, and C trains. Whereas B and C trains are irrelevant with respect to postoperative outcome, the A train--a sinusoidal, symmetrical sequence of high-frequency and low-amplitude signals--was observed in 19 patients and could be well correlated with additional postoperative facial nerve paresis (in 18 patients). CONCLUSIONS: It could be demonstrated that the occurrence of A trains is a highly reliable predictor for postoperative facial palsy. Although some degree of functional worsening is to be expected postoperatively, there is a good chance of avoiding major deficits by warning the surgeon early. Continuous EMG monitoring is superior to electrical nerve stimulation or acoustic loudspeaker monitoring alone. The detailed analysis of EMG-waveform characteristics is able to provide more accurate warning criteria during surgery.

Adult↗
PubMed1999

The prognostic value of intraoperative BAEP patterns in acoustic neurinoma surgery.

Based on a consecutive series of 70 hearing patients with unilateral acoustic neurinomas and intraoperative monitoring of brain-stem auditory evoked potentials (BAEP), 4 dynamic BAEP patterns could be characterized. These patterns correspond with early and late postoperative hearing outcome. All patients with stable wave V (pattern 1) showed definite hearing preservation, all patients with irreversible abrupt loss of BAEP (pattern 2) lost their hearing, despite early hearing preservation in two cases. All patients with irreversible progressive loss of either wave I or wave V (pattern 3) eventually suffered from definite postoperative hearing loss, despite early hearing preservation in two cases. Those cases with intraoperative reversible loss of BAEP (pattern 4) showed variable short and long term hearing outcome. In 34% hearing was preserved, 44% suffered from postoperative hearing loss, the remaining 22% showed postoperative hearing fluctuation, either as a delayed hearing loss or as reversible hearing loss. Postoperative hearing fluctuation indicates anatomical and functional preservation of the cochlear nerve during surgery and is suggestive of a pathophysiological mechanism initiated during the surgical procedure and continuing thereafter. Patients at risk for delayed hearing loss can be identified during surgery by a characteristic BAEP pattern and may benefit from vasoactive treatment.

Audiometry, Pure-Tone↗
PubMed1999

Pericollicular approaches to the rhomboid fossa. Part II. Neurophysiological basis.

OBJECT: The authors describe their technique of electrophysiological mapping to assist pericollicular approaches into the rhomboid fossa. METHODS: Surgical approaches to the rhomboid fossa can be optimized by direct electrical stimulation of superficially located nuclei and fibers. Electrophysiological mapping allows identification of facial nerve fibers, nuclei of the abducent and hypoglossal nerves, motor nucleus of the trigeminal nerve, and the ambiguous nucleus. Stimulation at the surface of the rhomboid fossa performed using the threshold technique allows localization above the area that is located closest to the surface. Simultaneous bilateral electromyographic (EMG) recordings from cranial motor nerves obtained during stimulation document the selectivity of evoked EMG responses. With respect to stimulation parameters and based on morphometric measurements, the site of stimulation can be assumed to be the postsynaptic fibers at the axonal cone. Strict limitation to 10 Hz with a maximum stimulation intensity not exceeding 2 mA can be considered safe. Direct side effects of electrical stimulation were not observed. CONCLUSIONS: Electrical stimulation based on morphometric data obtained on superficial brainstem anatomy defines two safe paramedian supra- and infracollicular approaches to the rhomboid fossa and is particularly helpful in treating intrinsic brainstem lesions that displace normal anatomical structures.

Adult↗
PubMed1998

Preservation of hearing in large acoustic neurinomas following removal via suboccipito-lateral approach.

A consecutive series of 61 patients with pre-operative hearing underwent surgical removal of a large acoustic neurinoma via the lateral suboccipital approach between 1984 and 1996. Brain-stem auditory evoked potentials (BAEP) were present in all cases before surgery and all patients underwent intra-operative monitoring of BAEP. The average tumour size including the portion within the meatus acusticus internus was 30, 5 mm (range 20 mm-49 mm). Complete tumour removal was achieved in all but three cases. In 43.1% of patients with complete tumour removal hearing was preserved initially after surgery. Delayed postoperative hearing loss was observed in 11 patients and hearing recovery in 2 patients leading to 27.5% definite hearing preservation. Hearing preservation was achieved in 37% of cases with tumour size between 20 mm-29 mm and in 23.5% of case with tumour size larger than 30 mm. These results indicate that even in large neurinoms hearing preservation should be attempted in all patients with documented pre-operative hearing and BAEP.

Adult↗
PubMed1998

The brave new world of quantum health care: some thoughts on the anatomy and physiology of a medical entity and the culture in which it is immersed. Part I.

In the absence of government intervention, the marketplace has taken over control of the health care sector in response to double-digit cost inflation. In the process, physician autonomy has waned. Health decisions are often made by corporate administrators; secretly hidden, less trained health personnel, and rigid protocols. Physician response as a profession has included dismay, anxiety, and depression. To return health care decisions back to physicians and to enhance the doctor/patient relationship, two suggestions are made. The first is the development of a task-oriented structure, energized by an implementation mechanism and information technology. This will allow for state-of-the-art, effective use of resources with care then judged by service, not by cost or access. The second is an introspective assessment of the physician's own personal psyche and the mission of the Profession. Redefining the mission and the motives behind it will allow the physician to "heal thyself" and move on to better and more satisfying patient care. The social contract with the Profession will then likely be reaffirmed, reestablished, and strengthened.

Delivery of Health Care↗
PubMed1997

Magnetic source imaging combined with image-guided frameless stereotaxy: a new method in surgery around the motor strip.

OBJECTIVE: In this study, information about the localization of the central sulcus obtained by magnetic source imaging (MSI) was intraoperatively translated to the brain, using frameless image-guided stereotaxy. In the past, the MSI results could be translated to the surgical space only by indirect methods (e.g., the comparison of the MSI results, displayed in surface renderings, with bony landmarks or blood vessels on the exposed brain surface). METHODS: Somatosensory evoked fields were recorded with a MAGNES II biomagnetometer (Biomagnetic Technologies Inc., San Diego, CA). Using the single equivalent current dipole model, the localization of the somatosensory cortex was superimposed on magnetic resonance imaging with a self-developed contour fit program. The magnetic resonance image set containing the magnetoencephalographic dipole was then transferred to a frameless image-guided stereotactic system. Intraoperatively, the gyrus containing the dipole was identified as the postcentral gyrus, using neuronavigation, and the next anterior sulcus was regarded as the central sulcus. With intraoperative cortical recording of somatosensory evoked potentials, this assumption was verified in each case. RESULTS: In all cases, the preoperatively assumed localization of the central sulcus and motor cortex with MSI agreed with the intraoperative identification of the central sulcus using the phase reversal technique. CONCLUSION: The combined use of MSI and a frameless stereotactic system allows a fast orientation of eloquent brain areas during surgery. This may contribute to a safer and more radical surgery in lesions adjacent to the motor cortex.

Aged↗
PubMed1997

Pericollicular surgical approaches to the rhomboid fossa. Part I. Anatomical basis.

A safe paramedian approach to the rhomboid fossa for surgical treatment of intrinsic brainstem lesions is based on detailed knowledge of the morphometric anatomy of superficially located motor structures. The morphometry of the rhomboid fossa is described in this report on the basis of histological studies conducted in six human brainstem specimens, with special emphasis on the colliculus facialis and the trigona nervi hypoglossi and vagi. Morphometric data include analysis of shrinkage factors in each specimen. The colliculus is a landmark for the nervus facialis, oculomotor nuclei, and the paramedian pontine reticular formation. In the surgeon's view from the posterior approach, the colliculus covers an area of 5.7 mm in the mediolateral and 6.8 mm in the craniocaudal direction and is located 0.6 mm lateral to the median sulcus. The fibers of the nervus facialis come as close as 0.2 mm to the surface of the fourth ventricle. The colliculus is located 15.7 mm above the obex. The trigona nervi hypoglossi and vagi cover a rectangular area measuring 3.1 by 6.5 mm and serve as a landmark for lower cranial nerve nuclei. These nuclei are located 0.3 mm lateral to the midline. An area with a maximum extension of 0.9 cm between the colliculus and trigona can be used for an infracollicular paramedian approach. The same applies to a supracollicular approach cranial to the colliculus and caudal to the fibers of the nervus trochlearis within the medullary velum, with a craniocaudal extension of 4 mm. Superficial motor nuclei and fibers can be identified by neurophysiological mapping, which helps to define safe surgical corridors into the rhomboid fossa, thus reducing functional morbidity caused by the operative approach in intrinsic pontine and pontomedullary lesions.

Abducens Nerve↗
PubMed1997

[Renal varices. X-ray computed tomographic diagnosis and treatment by embolization].

Two cases of recurrent macroscopic hematuria in which the diagnosis of left renal vein varices has suggested on CT are described. Bloody efflux was seen from the left ureteric orifice. On CT scans, tubulated contrast-enhanced densities in left perineal fat were seen. Selective renal angiography was normal. Selective left renal phlebography demonstrated intra and perirenal varices. In the two cases, embolization with metallic coli was successfully performed during left renal phlebography, to stop renal varices flux. Diagnostic and therapeutic modalities of renal varices are discussed with predominant place for CT and phlebography.

Adult↗
PubMed1997

Anatomical aspects for surgery within the floor of the IVth ventricle.

Successful removal of brainstem lesions is among other factors dependent on a safe surgical approach into the brainstem avoiding functional morbidity of superficially located nervous structures. Most midline pontine and pontomedullary lesions can be reached via a transvermian approach through the rhomboid fossa. This review describes the anatomical basis for the pericollicular paramedian surgical approaches into the rhomboid fossa with special emphasis on the microscopic anatomy.

Biopsy↗
PubMed1995

On the site of transcranial magnetic stimulation of the facial nerve: electrophysiological observations in two patients after transection of the facial nerve during neuroma removal.

The site of stimulation of the facial nerve after transcranial temporo-occipital magnetic stimulation is being controversially discussed, particularly whether the nerve is stimulated in the root exit zone in the cerebellopontine angle or whether stimulation originates within the bony canal of the facial nerve. In two case reports, the neurophysiological findings after the surgical transection of the facial nerve during the extirpation of a large acoustic and a facial nerve neuroma are presented. In both cases, transcranial magnetic stimulation of the facial nerve produced compound muscle action potential 4 and 2 days after the dissection of the facial nerve at the internal auditory canal and in the supralabyrinthine portion. These findings indicate that the site of stimulation in transcranial magnetic stimulation can be located to the course of the facial nerve within its bony petrosal canal distal to the external genu.

Action Potentials↗
PubMed1993

Parallel angioplasty dilatation catheter and guide wire: a new technique for the dilatation of calcified coronary arteries.

Percutaneous transluminal coronary angioplasty (PTCA) of heavily calcified rigid coronary arteries has decreased success and increased complication rates. Three cases are presented describing a new technique for the dilatation of severely calcified coronary arteries that were not dilatable by conventional angioplasty methods. This technique involves the use of a balloon dilatation catheter system parallel to a guide wire.

Aged↗
PubMed1993

Intraoperative identification of motor areas of the rhomboid fossa using direct stimulation.

Intraoperative electrical identification of motor areas within the floor of the fourth ventricle was successfully carried out in a series of 10 patients with intrinsic pontine lesions and lesions infiltrating the brain stem. Direct electrical stimulation was used to identify the facial colliculus and the hypoglossal triangle before the brain stem was entered. Multichannel electromyographic recordings documented selective stimulation effects. The surgical approach to the brain stem was varied according to the electrical localization of these structures. During removal of the lesion, functional integrity was monitored by intermittent stimulation. In lesions infiltrating the floor of the fourth ventricle, stimulation facilitated complete removal. Permanent postoperative morbidity of facial or hypoglossal nerve dysfunction was not observed. Mapping of the floor of the fourth ventricle identifies important surface structures and offers a safe corridor through intact nervous structures during surgery of brain-stem lesions. Reliable identification is particularly important in mass lesions with displacement of normal topographical anatomy.

Adult↗