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Biomedical subjects

R Heermann

Publications and source records attributed to R Heermann.

At least 37 records · Page 2Linked to original sources
PubMed2001

Navigation with the StealthStationtrade mark in Skull Base Surgery: An Otolaryngological Perspective.

The introduction of computer-assisted navigation systems has played a significant role in assuring the integration and consistent intraoperative use of radiological information. We used a frameless stereotactic navigation system to treat 62 patients with a variety of skull base pathologies. The optoelectric appliance uses digital imaging information to locate surgical instruments in the operative area. The aim of this study was to evaluate the clinical accuracy, practicality, and impact of this navigation system on otolaryngological procedures. In conjunction with rigid head fixation and bone-anchored registration markers, the precision of registration was 0.8 mm and the accuracy of clinical measurements was less than 2 mm. With conventional fiducials and flexible head positioning, deviations were as large as 4.5 mm. The additional use of surface registration increased the precision of registration. Preoperative preparations took 15 to 35 minutes, depending on the complexity of the planning. Intraoperative computer support is an important aid to a surgeon's orientation, especially when a patient's anatomy is atypical. Navigation systems will likely improve the quality of surgery and facilitate training.

Journal Article↗
PubMed2001

Image-guided surgery of the anterior skull base.

Minimally invasive surgical procedures have revolutionized surgery of the paranasal sinuses. The endonasal procedure has become standard practice due to a better understanding of pathological physiology. However, malformations, previous operations and bleeding can interfere greatly with intraoperative orientation. Together with microscopy and endoscopy, image-guided surgery has the potential to be of significant assistance to the surgeon. We evaluated the electromagnetic navigation system InstaTrak 2000 (Visualization Technologies Inc., Lawrence, MA) in 168 patients with various disorders of the paranasal sinuses who underwent endonasal surgery. The system consists of a headset attached to an electronic transmitter which is fitted on the dorsum of the nose and in the external auditory canal. With the aid of low-frequency magnetic fields the position of the instrument equipped with an electromagnetic receiver is calculated on the basis of the reaction of ferromagnetic components in the magnetic field; the location is displayed in orthogonal sections on a high resolution screen. The intraoperative accuracy of the system was estimated to be 1.2-2.8 mm. The preparation time amounted to < 10 min. No system failures were observed. The InstaTrak 2000 navigation system is only suitable for endonasal surgery. The placement of the electromagnetic transmitter and receiver allows flexible head positioning through the use of a headset. This system is a valuable aid for the surgeon under anatomically complex conditions. The technology also lends itself well to training purposes, as visualization in different sectional planes augments the understanding of anatomy and pathological anatomy.

Adult↗
PubMed2000

The hydrophilic N-terminal domain complements the membrane-anchored C-terminal domain of the sensor kinase KdpD of Escherichia coli.

The putative turgor sensor KdpD is characterized by a large, N-terminal domain of about 400 amino acids, which is not found in any other known sensor kinase. Comparison of 12 KdpD sequences from various microorganisms reveals that this part of the kinase is highly conserved and includes two motifs (Walker A and Walker B) that are very similar to the classical ATP-binding sites of ATP-requiring enzymes. By means of photoaffinity labeling with 8-azido-[alpha-(32)P]ATP, direct evidence was obtained for the existence of an ATP-binding site located in the N-terminal domain of KdpD. The N-terminal domain, KdpD/1-395, was overproduced and purified. Although predicted to be hydrophilic, it was found to be membrane-associated and could be solubilized either by treatment with buffer of low ionic strength or detergent. The membrane-associated form, but not the solubilized one, retained the ability to bind 8-azido-[alpha-(32)P]ATP. Previously, it was shown that the phosphatase activity of a truncated KdpD, KdpD/Delta12-395, is deregulated in vitro (Jung, K., and Altendorf, K. (1998) J. Biol. Chem. 273, 17406-17410). Here, we demonstrated that this effect was reversed in vesicles containing both the truncated KdpD and the N-terminal domain. Furthermore, coexpression of kdpD/Delta12-395 and kdpD/1-395 restored signal transduction in vivo. These results highlight the importance of the N-terminal domain for the function of KdpD and provide evidence for an interaction of this domain and the transmitter domain of the sensor kinase.

Adenosine Triphosphate↗
PubMed2000

[Drug and psychological therapies in chronic subjective tinnitus. Meta-analysis of therapeutic effectiveness].

A metaanalysis on pharmacological and psychological treatment reports was conducted in order to evaluate the overall effectiveness of these treatment conditions in chronic tinnitus. A totality of 109 treatment studies published between 1976 and 3/1995 and meeting minimal inclusion criteria was located, but only 24 studies reporting sufficient information could be analyzed. The methodological quality of the studies was evaluated by a coding scheme, and the resulting index of effectiveness has been weighted by this standard as well as by sample size. Effect sizes of pharmacological studies were ES = 1.27 and by this higher than the ones for psychological studies with ES = 0.88. This finding is attenuated by high (unspecific) placebo effects of ES = 0.65 in pharmacological studies compared to ES = 0.10 in psychological studies. In general, patients from psychological studies further improve after treatment in cases where catamnestic measurements have been conducted.

Anesthetics, Local↗
PubMed1999

Contribution of low-dose CT-scan protocols to the total positioning error in computer-assisted surgery.

PURPOSE: To quantify the contribution of a computed tomography (CT) scan to navigation accuracy in computer-assisted surgery. METHODS: Eighty-eight patients undergoing computer-assisted facial or skull-base surgery were fitted preoperatively with 4 to 12 markers, either attached to the skin (n = 20) or fixed in the osseous skull (micro-screws; n = 68). Low-dose high-resolution spiral CT was achieved with 25-cm field of view (FoV), 1-mm slice thickness, 2-mm table increment, 1-mm reconstruction interval, 140 kV, 40 mA, bony reconstruction algorithm, and 180 degrees reconstruction profile (effective slice thickness = 1.8 mm). During surgery, navigation accuracy was evaluated using two navigation systems. RESULTS: Mean error was 0.66 mm for osseous markers and 1.58 mm for cutaneous markers. Both values are markedly smaller than the effective slice thickness of the scan protocol used. Radiation exposure of the patient for the entire examination never exceeded that necessary for one single 10-mm slice in a standard brain examination. Despite the reduced dose, landmarks and fiducials were precisely identified in all cases. CONCLUSIONS: The CT-induced positioning error in the Z-axis is considerably reduced by overlapping raw data reconstruction. For 1-mm slices and a 25-cm FoV, the average scan-induced positioning error is about 0.3 mm. Spatial resolution is not affected by the low dose applied. For MRI-based navigation, a 1 mm3 voxel size is the best compromise between signal-to-noise ratio, spatial resolution and scan time.

Algorithms↗
PubMed1999

[Sonographic diagnosis of metastatic renal cell carcinoma to the head and neck region].

In the area of the head and neck metastases from distant primary tumours are rare in comparison to the common squamous cell carcinomas of the upper respiratory and digestive tract. Thus correct preoperative diagnosis may be difficult. Two cases with distant metastases of renal cell carcinoma to the head and neck region are presented in this report. In a 60-year-old male patient, diagnostic evaluation of unilateral epistaxis revealed a radioopacity of the maxillary sinus, six months after removal of a renal cell carcinoma. In the second case a slowly progressive indolent swelling of the left neck developed in a 56-year-old man six years after resection of a renal cell carcinoma and two years after surgical treatment of a pancreatic carcinoma. Following clinical examination, modern imaging techniques with special emphasis on colour Doppler sonography with a Siemens Quantum 2000 were used for diagnostic evaluation in both patients. Sonography of metastatic renal cell carcinoma to the maxillary sinus revealed complete opacity of the antrum. The cervical mass proved to the inhomogeneous and hypoechogenic and was difficult to distinguish from the lower parotid lobe and the vessel sheath. A common feature of both tumours was a high degree of perfusion which could be confirmed by superselective angiography. The histological examination of the surgical specimen showed an isolated metastasis of a renal cell carcinoma in both cases. In patients with a history of renal cell carcinoma the possibility of distant spread to the head and neck region should be taken into account even after a long period of complete remission. Colour Doppler sonography facilitates the distinction between the normally well perfused secondary tumours and squamous cell carcinomas which usually only have a minimal blood supply. Because of the high risk of profuse bleeding a biopsy should only be performed in the operating theatre.

Carcinoma, Renal Cell↗
PubMed1999

[Ultrasound evaluation of characteristics of cervical lymph nodes with special reference to color Doppler ultrasound. A contribution to differentiating reactive from metastatic lymph node involvement in the neck].

BACKGROUND: Cervical mass due to lymphadenopathy is a common cause for consultation of an ENT specialist by patients. In many cases exact differentiation without biopsy between reactive and metastatic lymphnodes is difficult but crucial and necessary for each patient. Ultrasound is the imaging system with the highest sensitivity for the evaluation of pathological lymph nodes. However, differentiating benign and malignant lesions remains a problem. PATIENTS: In a prospective study, 138 cervical lymph nodes of 62 patients were evaluated according to conventional ultrasound criteria such as size, shape, brightness, demarcation, etc., and according to parameters of color doppler sonography such as intensity and localization of perfusion. The so called Pourcelot or resistance index, an objective parameter, was measured in order to examine a possible improvement of specificity in differential diagnosis of both entities. All lymph nodes were surgically removed and histologically examined after ultrasonography. RESULTS: 133 lymph nodes were evaluated in the study. Lymphadenitis was demonstrated in 72 cases, whereas 61 of the lumps showed metastases of squamous cell carcinoma of the head and neck region. Three patients with primary malignant lymphoma were excluded from the study. The conventional ultrasound parameters such as size, homogenity, shape and brightness did not reveal any substantial difference between the two groups. However, lymph node metastases significantly showed higher Doppler signals than the reactive ones. Most of the metastases were perfused in the periphery or had a diffuse spread of blood flow. The most valuable parameter from the prognostical point of view proved to be the Pourcelot Index with a threshold value less than 0.6 for metastases, which increased the specificity to 92% with a probability of p = 0.001. CONCLUSIONS: The results of this study demonstrate an increase of the ultrasound specificity in differentiation of pathological cervical lymph nodes using color flow imaging. Unfortunately, this method does not enable the physician to correctly diagnose the findings in all patients. Therefore histological evaluation is mandatory in all doubtful cases.

Adolescent↗
PubMed1999

Adenoid cystic carcinoma of the skull base.

Adenoid cystic carcinoma (ACC) is a slowly growing tumor with a particular tendency to infiltrate the surrounding tissue by perineural spread. The clinical diagnosis may prove difficult due to the submucons extension of the tumor, especially at the skull base. This article outlines the clinical characteristics, diagnostics, and treatment modalities in a series of 56 patients with an ACC in the head and neck diagnosed between 1970 and 1998 in 32 females and 24 males. The youngest patient was aged 24 years, the oldest 77 years. The average age was 54 years. In 16 patients the tumor originated in the paranasal sinuses or the nasopharynx and involved the skull base. As a rule, several months passed between the manifestation of the first symptoms such as pain, blocked nose, epistaxis, or diplopia and the initial clinical diagnosis. All patients received surgical treatment, however, complete microscopical resection could only be achieved in approximately one third of the cases. Therefore, nine patients were postoperatively treated with radiotherapy. The average survival rates of the patients with an ACC of the skull base were only 99 months as compared to 144 months in the patients without skull base involvement.

Journal Article↗
PubMed1998

The turgor sensor KdpD of Escherichia coli is a homodimer.

Escherichia coli responds to K+-limitation or high osmolarity by induction of the kdpFABC operon coding for the high affinity K+-translocating KdpFABC complex. Expression of the corresponding operon is controlled by the membrane-bound sensor kinase KdpD and the cytoplasmic response regulator KdpE. Here, we examine the oligomeric state of KdpD. KdpD-His673-->Gln and KdpD-Asn788-->Asp are kinase inactive. When the corresponding genes are coexpressed, the resulting KdpD protein regains kinase activity in vitro, suggesting that the functional state of KdpD is at least a dimer and that the kinase reaction is a result of a trans-phosphorylation between two monomers. Furthermore, coexpression of kdpD-6His and kdpD-(Delta128-391) leads to stable heterooligomers that can bind to Ni-NTA agarose and that are coeluted. Purified and solubilized KdpD-6His has been electrophoresed in blue native polyacrylamide gels (BN-PAGE), and unphosphorylated and phosphorylated KdpD resulted in the same band pattern suggesting that the oligomeric state of KdpD does not change upon phosphorylation. In addition, determination of the molecular masses of KdpD-6His and KdpD-6His approximately 32P by gel filtration reveals a value of 245 kDa for both forms of the protein. The Stokes radius is determined to be 5.4 nm. Sucrose gradient sedimentation analysis of KdpD-6His results in a molecular mass of 289 kDa. The calculated molecular mass of a KdpD-6His monomer is 99.6 kDa. Considering the detergent bound to KdpD the obtained data reveal that KdpD is a homodimer and there is no change in the oligomeric state upon activation. Crosslinking experiments with single Cys KdpD molecules indicate that there is a close contact between the monomers in the transmitter as well as in transmembrane domain 1. BN-PAGE of solubilized and purified KdpD-6His devoid of Cys residues demonstrates that Cys residues do not contribute to the stabilization of the dimer.

Bacterial Proteins↗
PubMed1998

Effect of cysteine replacements on the properties of the turgor sensor KdpD of Escherichia coli.

Escherichia coli responds rapidly to K+-limitation or high osmolarity by induction of the kdpFABC operon coding for the high affinity K+-translocating Kdp-ATPase. This process is controlled by the membrane-bound histidine kinase KdpD and the response regulator KdpE. Here, it is demonstrated that replacements of the native Cys residues at positions 409, 852, and 874 influence distinct activities of KdpD, whereas replacements of Cys residues at positions 32, 256, and 402 have no effect. Replacements of Cys409 in KdpD reveal that transmembrane domain I is important for perception and/or propagation of the stimulus. When Cys409 is replaced with Ala, kdpFABC expression becomes constitutive regardless of the external stimuli. In contrast, when Cys409 is replaced with Val or Tyr, induction of kdpFABC expression in response to different stimuli is drastically reduced. KdpD with Ser at position 409 supports levels of kdpFABC expression comparable to those seen in wild-type. Since neither the kinase nor phosphatase activity of these proteins is affected, it is proposed that different amino acid side-chains at position 409 alter the switch between the inactive and active forms of the kinase. When Cys852 or Cys874 is replaced with Ala or Ser, kinase activity is reduced to 10% of the wild-type level. However, kinetic studies reveal that the apparent ATP binding affinity is not affected. Surprisingly, introduction of Cys852 and Cys874 into a KdpD protein devoid of Cys residues leads to full recovery of the kinase activity. Labeling studies support the idea that a disulfide bridge forms between these two residues.

Bacterial Proteins↗
PubMed1997

[Primary intra-meatal invasion of meningioma into the left meatus acusticus internal in a 49-year-old woman].

BACKGROUND: Meningiomas originating in the internal auditory meatus are rare and have been reported in only 12 cases. PATIENT: We report about another case, which showed primarily the symptoms of sudden hearing loss and diagnostic signs of an intrameatal acoustic neuroma. The ABR interpeak latency IV was prolonged. The tumor was detected by MRI scan with gadolinium contrast enhancement and resembled the features of an intrameatal acoustic neuroma. RESULTS: The tumor was removed via a middle fossa approach with preservation of hearing and facial nerve function. Histological examination however revealed a meningioma originating from the internal auditory meatus. CONCLUSIONS: Contrast enhancing intrameatal tumors are most often acoustic neuromas. However even despite subtile audiological and neurotological examination and sophisticated imaging techniques they cannot be differentiated clinically from meningiomas at this location. Removal of the intrameatal tumor via a middle fossa approach seems to be the best surgical approach to preserve hearing and facial nerve function.

Audiometry, Pure-Tone↗
PubMed1997

[Axillary metastases of oropharyngeal carcinoma after pectoralis major flap].

Reconstruction of defects after resection of advanced head and neck tumours with the pedicled myocutaneous pectoralis-major-flap is a well established method of regional plastic surgery. A 66 year old female patient with an oropharyngeal squamous cell carcinoma was treated by surgery and radiotherapy in curative intention. A few months later a local recurrence could be resected by a lateral pharyngotomy while the defect was reconstructed with a myocutaneous pectoralis-major-flap. Together with another local relapse at the pectoralis-major-flap in the oropharynx a painless tough swelling developed in the ipsilateral axilla which revealed histologically as a lymph node metastasis of a squamous cell carcinoma. Because no second malignoma as a source for this metastasis could be found, a lymphogenous spread of the oropharyngeal carcinoma along the pedicle of the flap could be the most probable explanation for this rare event. As a conclusion of this observation all patients with pedicled reconstructions after resection of head and neck cancer should not only be examined in the tributary lymph node levels of the neck but also in the axilla during oncological follow up.

Aged↗
PubMed1996

[Tooth discoloration as a rare complication of septorhinoplasty].

BACKGROUND: Surgeons should thoroughly consider the clinical implications of elective surgery such as septorhinoplasty for functional and cosmetic improvement of the appearance of the nose. Complications may jeopardize the intended result of this surgery. CASE REPORT: We report on the rare complication of devitalization of two incisors in the maxilla with disturbing discoloration after performing a septorhinoplasty in a 23-year-old woman. The patient underwent a serial hydrogen peroxide bleaching and a root canal procedure. CONCLUSION: The osteotomy of a huge basal crista that compromised neurovascular dental supply could be a possible mechanism of this event. Even though such a complication after septorhinoplasty is extremely rare, patients should be informed of this eventually prior to surgery, if only for legal reasons.

Adult↗
PubMed1996

[Distant metastasis of renal cell carcinomas to the head-neck area].

BACKGROUND: Metastases of hypernephroma to the head and neck, especially to the larynx, are rare occurrences. PATIENTS: We report on two cases with solitary spread in the head and neck. A 73-year-old woman who underwent nephrectomy because of a hypernephroma six years ago had a manifestation in the right false vocal cord, which was resected by laser surgery. The specimen of the strumectomy in the other patient revealed a metastasis of an asymptomatic hypernephroma to the thyroid gland and finally led to correct diagnosis of the primary tumor. RESULTS: The female patient refused any further treatment and died of cachexia with tumor dissemination four months later. The other patient is still living with a local recurrence after palliative irradiation and administration of interleukin-2 and alpha-interferon. CONCLUSIONS: In absence of other tumor manifestations, choosing an adequate therapy can be difficult because of the long survival rates in some patients even after hematogenous spread and the unpredictable behavior of this malignancy.

Aged↗