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Biomedical subjects

C Strauss

Publications and source records attributed to C Strauss.

At least 19 recordsLinked to original sources
PubMed2003

[Multidetector CT and MRI in pancreatic diseases].

Multidetector CT and MRI are the most efficient non invasive techniques in the assessment of pancreatic diseases. As with MRI, multidetector CT has now become an all in one examination using 2 D and 3 D multiplanar reformations with the ability to perform with high accuracy: a) vascular assessment using MIP reconstruction and b) biliary and pancreatic ducts assessment using minIP reconstruction. This review compares and illustrates the respective advantages of MRI and multidetector CT in the assessment of pancreatic diseases.

Acute Disease↗
PubMed2002

Localisation of the sensorimotor cortex during surgery for brain tumours: feasibility and waveform patterns of somatosensory evoked potentials.

OBJECTIVE: Intraoperative localisation of the sensorimotor cortex using the phase reversal of somatosensory evoked potentials (SEPs) is an essential tool for surgery in and around the perirolandic gyri, but unsuccessful and perplexing results have been reported. This study examines the effect of tumour masses on the waveform characteristics and feasibility of SEP compared with functional neuronavigation and electrical motor cortex mapping. METHODS: In 230 patients with tumours of the sensorimotor region the SEP phase reversal of N20-P20 was recorded from the exposed cortex using a subdural grid or strip electrode. In one subgroup of 80 patients functional neuronavigation was performed with motor and sensory magnetic source imaging and in one subgroup of 40 patients the motor cortex hand area was localised by electrical stimulation mapping. RESULTS: The intraoperative SEP method was successful in 92% of all patients, it could be shown that the success rate rather depended on the location of the lesion than on preoperative neurological deficits. In 13% of the patients with postcentral tumours no N20-P20 phase reversal was recorded but characteristic polyphasic and high amplitude waves at 25 ms and later made the identification of the postcentral gyrus possible nevertheless. Electrical mapping of the motor cortex took up to 30 minutes until a clear result was obtained. It was successful in 37 patients, but failed in three patients with precentral and central lesions. Functional neuronavigation indicating the tumour margins and the motor and sensory evoked fields was possible in all patients. CONCLUSION: The SEP phase reversal of N20-P20 is a simple and reliable technique, but the success rate is much lower in large central and postcentral tumours. With the use of polyphasic late waveforms the sensorimotor cortex may be localised. By contrast with motor electrical mapping it is less time consuming. Functional neuronavigation is a desirable tool for both preoperative surgical planning and intraoperative use during surgery on perirolandic tumours, but compensation for brain shift, accuracy, and cost effectiveness are still a matter for discussion.

Adolescent↗
PubMed2001

Prospects for ab initio protein structural genomics.

We present the results of a large-scale testing of the ROSETTA method for ab initio protein structure prediction. Models were generated for two independently generated lists of small proteins (up to 150 amino acid residues), and the results were evaluated using traditional rmsd based measures and a novel measure based on the structure-based comparison of the models to the structures in the PDB using DALI. For 111 of 136 all alpha and alpha/beta proteins 50 to 150 residues in length, the method produced at least one model within 7 A rmsd of the native structure in 1000 attempts. For 60 of these proteins, the closest structure match in the PDB to at least one of the ten most frequently generated conformations was found to be structurally related (four standard deviations above background) to the native protein. These results suggest that ab initio structure prediction approaches may soon be useful for generating low resolution models and identifying distantly related proteins with similar structures and perhaps functions for these classes of proteins on the genome scale.

Computer Simulation↗
PubMed2001

Clinical and neurophysiological observations after superior petrosal vein obstruction during surgery of the cerebellopontine angle: case report.

IMPORTANCE: Preservation of venous drainage during surgery of the cerebellopontine angle has received little attention. CLINICAL PRESENTATION: We describe changes in brainstem auditory evoked potentials after temporary obstruction of the superior petrosal vein during surgical resection of a small meningioma at the petrous apex via a standard suboccipital-lateral approach. Temporary clipping of the petrosal vein resulted in deterioration of the brainstem auditory evoked potentials. The tumor was removed with preservation of the superior petrosal vein. CONCLUSION: A transient postoperative cochlear nerve deficit emphasizes the importance of venous drainage and its preservation during surgery for small lesions of the cerebellopontine angle that do not distort normal anatomic structures.

Cerebellopontine Angle↗
PubMed2001

Vasoactive treatment for hearing preservation in acoustic neuroma surgery.

OBJECT: Delayed hearing loss following surgery for acoustic neuroma indicates anatomical and functional preservation of the cochlear nerve and implies that a pathophysiological mechanism is initiated during surgery and continues thereafter. Intraoperative brainstem auditory evoked potentials (BAEPs) typically demonstrate gradual reversible loss of components in these patients. METHODS: Based on this BAEP pattern, a consecutive series of 41 patients with unilateral acoustic neuromas was recruited into a prospective randomized study to investigate hearing outcomes following the natural postoperative course and recuperation after vasoactive medication. Both groups were comparable in patient age, tumor size, and preoperative hearing level. Twenty patients did not receive postoperative medical treatment. In 70% of these patients anacusis was documented and in 30% hearing was preserved. Twenty-one patients were treated with hydroxyethyl starch and nimodipine for an average of 9 days. In 66.6% of these patients hearing was preserved and in 33.3% anacusis occurred. CONCLUSIONS: These results are statistically significant (p < 0.05, chi2 = 5.51) and provide evidence that these surgically treated patients suffer from a disturbed microcirculation that causes delayed hearing loss following removal of acoustic neuromas.

Adult↗
PubMed2000

[Detection of asymptomatic venous thrombosis after lower limb prosthetic surgery. Retrospective evaluation of a systematic approach using Doppler ultrasonography: 400 cases].

OBJECTIVES: The purpose of this study was to evaluate a pragmatic approach using duplex ultrasonography (US) for detecting deep vein thrombosis (DVT) after total hip (THA) and total knee (TKA) replacement. METHODS: Venous B-mode and color duplex US examination of both legs including a systematic evaluation of calf veins was performed twice during hospital stay (Between day 1 and day 4 for the first exam and between day 7 and day 11 for the second) in 400 consecutive patients. RESULTS: Deep vein thrombosis was diagnosed in 53 patients (13.5%) including 7 patients with proximal DVT. Thrombosis was asymptomatic in 46 patients (85%), and was bilateral or concerned the non-operated leg in 8 patients (14.5%). No clinical pulmonary embolism (PE) occurred during hospital stay (mean hospital stay: 12.3). Prior phlebitis and age over 70 were identified as a statistically significant risk-factor for post-operative DVT (p = 0.001 and p < 0.01 respectively) concerning the whole series and the THA series (p < 0.02 and p < 0.04 respectively). No statistically significant risk factor was founded for the TKA series (p < 0.2 and p < 0.2 respectively). All patients were seen at three months. Four patients (1.16%) developed DVT between hospital discharge and the 3-month follow-up visit. One patient with coronary disease died suddenly on post-operative day 24, without clinical signs or symptoms of PE or DVT. CONCLUSION: Venous US performed twice after total hip replacement detected asymptomatic DVT in 85% of patients. This approach might explain the absence of PE in our series and thus justify systematic ultrasonographic evaluation of lower limb veins after prosthetic replacement.

Adult↗
PubMed2000

[Langerhans-cell histiocytosis of the orbit; diagnosis, treatment and outcome in three patients -- children and adults].

BACKGROUND: Langerhans cell histiocytosis usually affects children. Systemic Langerhans cell histiocytosis may be present in 37% of affected children. Ten per cent of all children die of the disease. CASE REPORTS: Patient 1. A 9-year-old boy presented with painful upper lid swelling OD. Ultrasonography revealed a space-occupying lesion adjacent to a lytic defect of the frontal bone as shown on coronal CT. MRI showed marked contrast enhancement of the mass which came close to the intracranial fossa. The vascularized tumor was excised using an anterior orbitotomy with upper lid crease incision. No evidence of local or systemic recurrence was present three years postoperatively. Patient 2. A 19-year-old male presented with foreign body sensation, double vision OS and numbness of the left face of six weeks' duration. The ocular findings revealed a sixth nerve palsy OS. Otherwise, the eyes were unremarkable. Sensitivity of cranial nerve V2 was decreased. CT revealed an osteolytic process in the lateral orbital wall and sphenoid wing. MRI demonstrated a space-occupying lesion involving the temporalis muscle laterally, the pterygopalatine fossa medially with intracranial extension into the temporal lobe. Surgical excision was performed using a transcranial approach. Signs and symptoms had completely resolved six months after surgery with no evidence of local or systemic recurrence. Patient 3. A 30-year-old male presented with right-sided headache, painful upper lid swelling and vertical diplopia. Coronal CT scan revealed a lytic defect in the frontal bone laterally. Curettage and complete excision were performed using an infrabrow incision. Follow-up examination four years later revealed an intact ocular motility with no evidence of local or systemic recurrence. In all three cases the tumor showed characteristic light-microscopy and immunohistochemical features of Langerhans cell histiocytosis. CONCLUSION: Langerhans cell histiocytosis of the orbit is an important differential diagnosis of osteolytic and/or space-occupying lesions not only in children, but also in adults. A diagnostic biopsy followed by surgical excision and/or local and systemic corticoid- and chemotherapy are essential regarding the prognosis of local and systemic disease.

Adolescent↗
PubMed2000

Contralateral hearing loss as an effect of venous congestion at the ipsilateral inferior colliculus after microvascular decompression: report of a case.

Contralateral hearing loss after surgical procedures within the cerebellopontine angle is rarely seen and its pathophysiological background is not yet understood. A patient with contralateral hearing loss after microvascular decompression for trigeminal neuralgia is described. Ipsilateral brainstem auditory potential (BAEP) monitoring and facial nerve EMG did not show major abnormalities. During otherwise uneventful and successful surgery a branch of the petrosal vein was sacrificed to widen the access to the trigeminal root exit zone. On the third postoperative day the patient complained about contralateral hearing loss, which was verified by audiometry. Contralateral BAEPs showed low amplitudes and delayed interpeak latencies. Brain CT was normal. Brain MRI on the 8th postoperative day disclosed abnormal signals within the ipsilateral inferior colliculus. Intravenous heparinisation was performed and hearing slowly recovered over a 3 month period. Results from this patient offer a pathophysiological mechanism for contralateral hearing loss after cerebellopontine angle surgery, illustrate the importance of venous drainage preservation, gives evidence about the generation of BAEP components within the contralateral brainstem, and stresses the importance of intraoperative BAEP monitoring.

Acoustic Stimulation↗
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↗