Free Tissue Transfer in Head and Neck Reconstruction: A Multidisciplinary 15-Year Experience

BACKGROUND

Free tissue transfer is considered the gold standard in reconstruction of extensive defects in head and neck surgery. The aim of this 15-year retrospective study is to analyze the outcomes of free tissue transfers in the head and neck area in a tertiary referral university hospital.

MATERIALS AND METHODS

A retrospective, single-center study of all patients undergoing free tissue transfers for head and neck reconstruction between 2006 and 2020 was performed. Patient demographics, comorbidities, flap characteristics, outcomes and complications were assessed.

RESULTS

A total of 353 free flaps were performed. The most common defect etiology was synchronous oncologic resection (74.2%). The majority of patients had at least one comorbidity (70.3%), with smoking recorded in 46.2% of the cases and alcohol consumption in 31.7%. The anterolateral thigh flap was the most commonly used flap (37.7%), followed by the osteoseptocutaneous fibula flap (26.9%). Our overall flap success rate was 97.7%, while the overall complication rate was 45.9%.

CONCLUSIONS

Free tissue transfer in head and neck reconstruction is reliable. However, complication rates remain high due to the complexity of such cases and frequent presence of comorbidities. Nonetheless, when effectively managed within a multidisciplinary team, complications rarely jeopardize the overall reconstruction outcome.

Risk of Osteonecrosis of the Jaw Under Denosumab Compared to Bisphosphonates in Patients With Osteoporosis

Osteonecrosis of the jaw (ONJ) is a rare but serious adverse event associated with antiresorptive treatment. There is little evidence regarding the incidence of ONJ among patients with osteoporosis who are treated with denosumab versus bisphosphonates (BPs). The aim of this study was to determine the risk of ONJ in a real-world population. Subjects who underwent at least one dual-energy X-ray absorptiometry (DXA) examination were included in the osteoporosis register of the Swiss Society of Rheumatology between January 1, 2015, and September 30, 2019. Statistical analyses included incidence rates, rate ratios, and hazard ratios for ONJ, considering sequential therapies and drug holidays as covariates. Among 9956 registered patients, 3068 (89% female, median age 69 years [63 to 76]) were treated with BPs or denosumab for a cumulative duration of 11,101 and 4236 patient-years, respectively. Seventeen cases of ONJ were identified: 12 in patients receiving denosumab at the time of ONJ diagnosis and 5 in patients receiving oral or intravenous BP therapy. The diagnosis of ONJ was confirmed by independent and blinded maxillofacial surgeons, using the American Association of Oral and Maxillofacial Surgeons case definition of ONJ. The incidence of ONJ per 10,000 observed patient-years was 28.3 in patients receiving denosumab and 4.5 in patients with BP-associated ONJ, yielding a rate ratio of 6.3 (95% confidence interval [CI] 2.1 to 22.8), p < 0.001. Nine of 12 patients who developed ONJ during denosumab treatment had been pretreated with BPs, but none of the 5 patients with BP-related ONJ had previously received denosumab. The risk of ONJ was higher in patients receiving denosumab therapy compared with BPs (hazard ratio 3.49, 95% CI 1.16 to 10.47, p = 0.026). Previous BP therapy before switching to denosumab may be an additional risk factor for ONJ development. © 2021 American Society for Bone and Mineral Research (ASBMR).

Delayed Decline of Cognitive Function by Antihypertensive Agents: A Cohort Study Linked with Genotype Data

BACKGROUND

Arterial hypertension is among factors with the potential for increasing the risk of cognitive impairment in elderly subjects. However, studies investigating the effects of antihypertensives on cognitive function have reported mixed results.

METHODS

We have used the National Alzheimer's Coordinating Center (NACC) Uniform Data Set (UDS) to investigate the effect of each class of antihypertensives, both as single and combined, in reducing the rate of conversion from normal to mild cognitive impairment (MCI).

RESULTS

The use of antihypertensive drugs was associated with 21% (Hazard ratio: 0.79, p<01001) delay in the rate of conversion to MCI. This effect was modulated by age, gender, and genotypic APOE4 allele. Among different antihypertensive subclasses, calcium channel blockers (CCBs) (24%, HR: 0.76, P=0.004), diuretics (21%, HR: 0.79, P=0.006), and α1-adrenergic blockers (α1-ABs) (23%, HR: 0.77, P=0.034) significantly delayed the rate of MCI conversion. A significant effect was observed with the selective L-type voltage-gated CCBs, dihydropyridines, amlodipine (47%, HR=0.53, P<0.001) and nifedipine (49%, HR=0.51, P=0.012), whereas non-DHPs showed insignificant effect. Loop diuretics, potassium sparing diuretics, and thiazides all significantly reduced the rate of MCI conversion. Combination of α1-AB and diuretics led to synergistic effects; combination of vasodilators plus β-blockers (βBs), and α1-AB plus βBs led to additive effect in delaying the rate of MCI conversion, when compared to a single drug.

CONCLUSION

Our results could have implications for the more effective treatment of hypertensive elderly adults who are likely to be at high risk of cognitive decline and dementia. The choice of combination of antihypertensive therapy should also consider the combination which would lead to an optimum benefit on cognitive function.

Proposed Prediction Model and Nomogram for Systemic Complications in Patients Undergoing Free Flap Head and Neck Reconstruction

Postoperative complications in head and neck surgery are well-known, but a predictive model to guide clinicians in free flap reconstructions has not been established. This retrospective single-center observational study assessed 131 patients who underwent ablative surgery and received free flap reconstruction. Primary endpoint was the occurrence of systemic complications (PSC). Secondary endpoint was the generation of a nomogram of complications according to the CDC classification. In the ordinal regression model, postoperative administration of furosemide [1.36 (0.63–2.11), p < 0.0001], blood loss [0.001 (0.0004–0.0020), p = 0.004], postoperative nadir hemoglobin [−0.03 (−0.07–0.01), p = 0.108], smoking [0.72 (0.02–1.44), p = 0.043], and type of flap reconstruction [1.01 (0.21–1.84), p = 0.014] as predictors. A nomogram with acceptable discrimination was proposed (Somer's delta: 0.52). Application of this nomogram in clinical practice could help identify potentially modifiable risk factors and thus reduce the incidence of postoperative complications in patients undergoing microvascular reconstruction of the head and neck.

[Pentoxifylline and tocopherol - The importance in the treatment of osteoradionecrosis - Literature review and case report]

Osteoradionecrosis (ORN) is a serious complication after radiotherapy for head and neck cancer and is a challenging condition for both the therapist and the patient because of its difficult treatment. Different non-invasive approaches have been published for the treatment of low-grade ORN cases without establishing a standard regimen for treatment. Based on the approach of ORN pathogenesis, the so-called radiatio-induced fibroathrophic process (RIF), a new treatment concept with pentoxifylline and tocopherol (PENTO) has been published. The results of PENTO therapy seem promising as a conservative treatment approach for mild ORN or as an alternative when surgical intervention is not possible or desired. The present study summarizes the current state of the literature and shows the effectiveness of PENTO therapy based on a case report.

Osteoinductive potential of recombinant BMP-9 in bone defects of mice treated with antiresorptive agents

The aim of the present study was to investigate the effects of recombinant human (rh)BMP-9 on bone regenerative potential in a mouse model of antibody-mediated antiresorptive therapy (AMART). A monoclonal anti-murine receptor activator of nuclear factor-kappa B ligand (RANKL) antibody (mAb) was used to create an AMART model in mice. rhBMP-9 combined with collagen membrane was implanted in calvarial defects in mAb-treated mice. After 4 weeks, the bone formative potential in the defects was evaluated by micro-computed tomography and histological approaches. The groups implanted with rhBMP-9-containing collagen membranes demonstrated substantial osteopromotive potential, with significantly greater new bone volume (Sham + BMP-9 group; 0.86 ± 0.29 mm³ and mAb + BMP-9 group; 0.64 ± 0.16 mm³) than control PBS-membranes (Sham + PBS group; 0.44 ± 0.29 mm³ and mAb + PBS group; 0.24 ± 0.12 mm³) in both sham and mAb-treated mice. In line with in vivo study, bone marrow cells isolated from both sham and mAb-treated mice confirmed greater osteogenic potential upon stimulation with rhBMP-9 in vitro. These findings suggest for the first time that local rhBMP-9 administration might be a strategy to accelerate bone regeneration in the context of AMART.

Perioperative predictors of early surgical revision and flap-related complications after microvascular free tissue transfer in head and neck reconstructions: a retrospective observational series

Objectives

The aim of this study was to determine the influence of perioperative fluid management and administration of vasopressors on early surgical revision and flap-related complications in free tissue transfer.

Materials and methods

Intraoperative amount of fluid and of vasopressors, relevant perioperative parameters, and comorbidities were recorded in 131 patients undergoing head and neck microvascular reconstruction and compared with early surgical complications, defined as interventions requiring surgery after a flap-related complication, and/or other surgical problems in the operating room within 30 days after initial surgery. The relationship between perioperative variables for each revision category was determined using an optimized multiple logistic regression.

Results

The administration of diuretics (p=0.001) as a treatment for perioperative fluid overload and the type of flap (p=0.019) was associated with a higher risk of early surgical revisions. Perioperative fluid overload (p=0.039) is significantly related to flap-related complications. We found no effect of intraoperative administration of vasopressors on early surgical revisions (p=0.8) or on flap-related complications (norepinephrine p=0.6, dobutamine p=0.5).

Conclusion

Perioperative fluid overload is associated with higher risks of early surgical revision and flap-related complications. In contrast, the administration of vasopressors seemed to have no effect on either surgical revision rate or flap-related complications.

Clinical relevance

In patients receiving microvascular reconstructions, a balanced fluid administration perioperatively and a targeted use of vasopressors should be the necessary strategy to reduce the complication rates in head and neck surgery.

Temporomandibular joint dislocation: a retrospective study from a Swiss urban emergency department

Purpose

Temporomandibular joint (TMJ) dislocation is an uncommon and debilitating condition of the facial skeleton. The condition may be traumatic or nontraumatic, in an acute or chronic form, and with bilateral or monolateral expression.

Patients and methods

In this study, conducted from May 2012 to July 2016, we retrospectively analyzed TMJ dislocations treated in the Department of Emergency Medicine, Inselspital, University Hospital Bern, University of Bern, by focusing on the following parameters: age, gender, reason, localization, frequency, and therapy.

Results

Thirty-two patients were included. The mean age was 42.06 years and there was no predominant gender. Most cases of TMJ dislocation were nontraumatic (93.7%). Dislocations were mostly bilateral (59.4%) and appeared in a chronic situation and with repetitive events (62.5%). Thirty-one patients received conservative treatment, which consists of reposition of the TMJ with (38.7%) or without (61.3%) analgosedation. Only one patient needed surgical reposition due to previous surgical treatment.

Conclusion

This is the first attempt to evaluate TMJ dislocations in Switzerland in an acute hospital setting. To our knowledge, there are no other studies that systematically analyze these injuries by focusing on the patients’ characteristics. Surgical reposition is only indicated in complicated and very rare situations. Conservative approaches are commonly used and should be exhausted before any surgery.

Fracture Healing and Bone Remodeling With Human Standard-Sized Magnesium Versus Polylactide-Co-Glycolide Plate and Screw Systems Using a Mini-Swine Craniomaxillofacial Osteotomy Fixation Model

PURPOSE

This study compared the degradation profile, safety, and efficacy of bioresorbable magnesium alloy and polylactide-co-glycolide (PLGA) polymer osteosynthesis systems for the treatment of fractures in a load-sharing maxillofacial environment using a new mini-swine fracture fixation model.

MATERIALS AND METHODS

Two types of clinically relevant situations were evaluated in 5 Yucatan miniature pigs. Defined porcine midface osteotomies of the supraorbital rim and zygoma were created and fixed with either a coated magnesium (test animals) or PLGA plate and screw osteosynthesis system (control animals). After surgery, the mini-pigs were able to recover for either 1 or 9 months with continuous in vivo post-implantation monitoring. Standardized computed tomography (CT) imaging was taken immediately postoperatively and at termination for all animals. The 9-month cohort also underwent CT at 2, 4, and 6 months after surgery. At necropsy, osteotomy sites and bone-implant units were harvested, and healing was evaluated by micro-CT, histopathology, and histomorphometry.

RESULTS

After clinical and radiologic follow-up examination, all fracture sites healed well for both the magnesium and polymer groups regardless of time point. Complete bone union and gradually disappearing osteotomy lines were observed across all implantation sites, with no major consistency change in periprosthetic soft tissue or in soft tissue calcification. Macroscopic and microscopic examination showed no negative influence of gas formation observed with magnesium during the healing process. Histopathologic analysis showed similar fracture healing outcomes for both plating systems with good biocompatibility as evidenced by a minimal or mild tissue reaction.

CONCLUSIONS

This study confirms that WE43 magnesium alloy exhibited excellent fracture healing properties before its full degradation without causing any substantial inflammatory reactions in a long-term porcine model. Compared with PLGA implants, magnesium represents a promising new biomaterial with reduced implant sizes and improved mechanical properties to support fracture healing in a load-sharing environment.

Electrospun API-loaded mixed matrix membranes for controlled release

The development of biocompatible membrane materials capable of delivering active pharmaceutical ingredients (APIs) over a fixed time period offers significant advantages to the pharmaceutical and biomedical industries alike.

Severity and pattern of injuries caused by the traditional Swiss team sport 'Hornussen': first retrospective study at a level I trauma centre in Switzerland

BACKGROUND

This article addresses typical injury patterns related to the traditional Swiss team sport of Hornussen. A small plastic disk is struck with a special elastic racket and then intercepted in the field. Severe injuries have occasionally been reported. We present a systematic review of all cases of Hornussen injuries treated in the University Hospital of Bern from 2000 to 2014.

METHODS

To assess the frequency, type and outcome of Hornussen injuries, we performed a database search of all inpatient and outpatient cases related to Hornussen and that were admitted to and/or treated in Bern University Hospital from 2000 to 2014.

RESULTS

A total of 28 such patients could be identified. Apart from 1 woman injured as a bystander and treated as an outpatient, all patients were male and active players. Typical injury patterns comprised midfacial fractures and severe ocular traumata, very often in combination. Almost all of these patients had to be hospitalised due to the severity of the trauma suffered and underwent surgery. 1 patient had to be admitted to the intensive care unit prior to the operation.

CONCLUSIONS

Eye and face injuries caused by Hornussen can be devastating. This resembles the potential risk of other bat-and-ball sports, such as cricket and baseball. Apart from the economic loss due to treatment costs and sick leave, these injuries can be disabling for life. It should therefore be mandatory for all players to wear protective gear, as is already the case for Hornussen players born in 1984 or later.

Thermal processing of bone: in vitro response of mesenchymal cells to bone-conditioned medium

The autoclaving, pasteurization, and freezing of bone grafts to remove bacteria and viruses, and for preservation, respectively, is considered to alter biological properties during graft consolidation. Fresh bone grafts release paracrine-like signals that are considered to support tissue regeneration. However, the impact of the autoclaving, pasteurization, and freezing of bone grafts on paracrine signals remains unknown. Therefore, conditioned medium was prepared from porcine cortical bone chips that had undergone thermal processing. The biological properties of the bone-conditioned medium were assessed by examining the changes in expression of target genes in oral fibroblasts. The data showed that conditioned medium obtained from bone chips that had undergone pasteurization and freezing changed the expression of adrenomedullin, pentraxin 3, BTB/POZ domain-containing protein 11, interleukin 11, NADPH oxidase 4, and proteoglycan 4 by at least five-fold in oral fibroblasts. Bone-conditioned medium obtained from autoclaved bone chips, however, failed to change the expression of the respective genes. Also, when bone-conditioned medium was prepared from fresh bone chips, autoclaving blocked the capacity of bone-conditioned medium to modulate gene expression. These in vitro results suggest that pasteurization and freezing of bone grafts preserve the release of biologically active paracrine signals, but autoclaving does not.

Trigeminal cardiac reflex: new thinking model about the definition based on a literature review

Trigeminocardiac reflex (TCR) is a brainstem reflex that manifests as sudden onset of hemodynamic perturbation in blood pressure (MABP) and heart rate (HR), as apnea and as gastric hypermotility during stimulation of any branches of the trigeminal nerve. The molecular and clinical knowledge about the TCR is in a constant growth since 1999, what implies a current need of a review about its definition in this changing context. Relevant literature was identified through searching in PubMed (MEDLINE) and Google scholar database for the terms TCR, oculocardiac reflex, diving reflex, vasovagale response. The definition of the TCR varies in clinical as well as in research studies. The main difference applies the required change of MABP and sometimes also HR, which most varies between 10% and 20%. Due to this definition problem, we defined, related to actual literature, 2 major (plausibility, reversibility) and 2 minor criteria (repetition, prevention) for a more proper identification of the TCR in a clinical or research setting. Latest research implies that there is a need for a more extended classification with 2 additional subgroups, considering also the diving reflex and the brainstem reflex. In this review, we highlighted criteria for proper definition and classification of the TCR in the light of increased knowledge and present a thinking model to overcome this complexity. Further we separately discussed the role of HR and MABP and their variation in this context. As another subtopic we gave attention to is the chronic TCR; a variant that is rarely seen in clinical medicine.

Are glutamate and lactate increases ubiquitous to physiological activation? A (1)H functional MR spectroscopy study during motor activation in human brain at 7Tesla

Recent studies at high field (7Tesla) have reported small metabolite changes, in particular lactate and glutamate (below 0.3μmol/g) during visual stimulation. These studies have been limited to the visual cortex because of its high energy metabolism and good magnetic resonance spectroscopy (MRS) sensitivity using surface coil. The aim of this study was to extend functional MRS (fMRS) to investigate for the first time the metabolite changes during motor activation at 7T. Small but sustained increases in lactate (0.17μmol/g±0.05μmol/g, p<0.001) and glutamate (0.17μmol/g±0.09μmol/g, p<0.005) were detected during motor activation followed by a return to the baseline after the end of activation. The present study demonstrates that increases in lactate and glutamate during motor stimulation are small, but similar to those observed during visual stimulation. From the observed glutamate and lactate increase, we inferred that these metabolite changes may be a general manifestation of the increased neuronal activity. In addition, we propose that the measured metabolite concentration increases imply an increase in ΔCMRO2 that is transiently below that of ΔCMRGlc during the first 1 to 2min of the stimulation.

Is the macromolecule signal tissue-specific in healthy human brain? A (1)H MRS study at 7 Tesla in the occipital lobe

PURPOSE

The macromolecule signal plays a key role in the precision and the accuracy of the metabolite quantification in short-TE (1) H MR spectroscopy. Macromolecules have been reported at 1.5 Tesla (T) to depend on the cerebral studied region and to be age specific. As metabolite concentrations vary locally, information about the profile of the macromolecule signal in different tissues may be of crucial importance.

METHODS

The aim of this study was to investigate, at 7T for healthy subjects, the neurochemical profile differences provided by macromolecule signal measured in two different tissues in the occipital lobe, predominantly composed of white matter tissue or of grey matter tissue.

RESULTS

White matter-rich macromolecule signal was relatively lower than the gray matter-rich macromolecule signal from 1.5 to 1.8 ppm and from 2.3 to 2.5 ppm with mean difference over these regions of 7% and 12% (relative to the reference peak at 0.9 ppm), respectively. The neurochemical profiles, when using either of the two macromolecule signals, were similar for 11 reliably quantified metabolites (CRLB < 20%) with relatively small concentration differences (< 0.3 μmol/g), except Glu (± 0.8 μmol/g).

CONCLUSION

Given the small quantification differences, we conclude that a general macromolecule baseline provides a sufficiently accurate neurochemical profile in occipital lobe at 7T in healthy human brain.

Quantification of the neurochemical profile using simulated macromolecule resonances at 3 T

The broad resonances underlying the entire (1) H NMR spectrum of the brain, ascribed to macromolecules, can influence metabolite quantification. At the intermediate field strength of 3 T, distinct approaches for the determination of the macromolecule signal, previously used at either 1.5 or 7 T and higher, may become equivalent. The aim of this study was to evaluate, at 3 T for healthy subjects using LCModel, the impact on the metabolite quantification of two different macromolecule approaches: (i) experimentally measured macromolecules; and (ii) mathematically estimated macromolecules. Although small, but significant, differences in metabolite quantification (up to 23% for glutamate) were noted for some metabolites, 10 metabolites were quantified reproducibly with both approaches with a Cramer-Rao lower bound below 20%, and the neurochemical profiles were therefore similar. We conclude that the mathematical approximation can provide sufficiently accurate and reproducible estimation of the macromolecule contribution to the (1) H spectrum at 3 T.

Net increase of lactate and glutamate concentration in activated human visual cortex detected with magnetic resonance spectroscopy at 7 tesla

After the landmark studies reporting changes in the cerebral metabolic rate of glucose (CMRGlc ) in excess of those in oxygen (CMRO2 ) during physiological stimulation, several studies have examined the fate of the extra carbon taken up by the brain, reporting a wide range of changes in brain lactate from 20% to 250%. The present study reports functional magnetic resonance spectroscopy measurements at 7 Tesla using the enhanced sensitivity to study a small cohort (n = 6). Small increases in lactate (19% ± 4%, P < 0.05) and glutamate (4% ± 1%, P < 0.001) were seen within the first 2 min of activation. With the exception of glucose (12% ± 5%, P < 0.001), no other metabolite concentration changes beyond experimental error were significantly observed. Therefore, the present study confirms that lactate and glutamate changes during physiological stimulation are small (i.e. below 20%) and shows that the increased sensitivity allows reproduction of previous results with fewer subjects. In addition, the initial rate of glutamate and lactate concentration increases implies an increase in CMRO2 that is slightly below that of CMRGlc during the first 1-2 min of activation.

[Oral health as the mirror of health: the primary care medicine's poor relative?]

Oral health (OH) is indivisible from general health. Several studies have established the link between morbi-mortality, especially cardiovascular, and bad OH, particularly in the case of edentation. Regrettably, part of the population choses dental care renunciation for financial reasons. The primary care physician (PCP), as the health professionnal with the most frequent and intense contacts with the patients, plays an important role to reinforce prevention measures, OH maintenance and to detect oral pathologies. To fulfill this mission, he has to be trained to endo-buccal examination. Furthermore, both the PCP and the dentist have to proactively build an interprofessional approach to promote patients' OH.

[Comparison of early retinal microvascular changes and microalbuminuria as indicators for increased cardioascular risk]

INTRODUCTION

Prevention of cardiovascular disease is an important goal in clinical medicine and public health. In the process, the diagnosis of early end-organ damage is a priority beside the treatment of classic cardiovascular risk factors. To achieve this, the ophthalmoscopic examination of the retinal vessels plays a prominent role. Alternatively, the quantification of low quantities of albumin in the urine (microalbuminuria) allows the detection of early vascular damage in the kidney. The question is addressed as to whether these two methods are interchangeable or are rather complementary.

PATIENTS AND METHODS

We examined 226 members of the staff of the University Hospital Erlangen who volunteered to participate in a preventive campaign. A comprehensive history was taken, and height, weight and blood pressure were measured. Analysis of serum lipids and determination of the urinary albumin/creatinine ratio were performed. Fotos of the central fundus were taken with a non-mydriatic camera and analysed by an experienced ophthalmologist in a standardised fashion. The risk for cardiovascular mortality within the next ten years was estimated from age, sex, blood pressure and serum cholesterol using the euroSCORE tables for Germany.

RESULTS

There was no signficant correlation between the arteriovenous ratio of the retinal vessels and the urinary albumin/creatinine ratio. Neither parameter correlated with the euroSCORE Germany. Arteriovenous crossings and focal narrowing of the retinal vessels were associated signficantly with an elevated euroSCORE risk.

CONCLUSIONS

In large population-based studies, the arteriovenous ratio and the urinary albumin/creatinine ratio have been confirmed as markers of cardiovascular risk. In our study, there was no correlation between these two parameters. Thus, they seem to present independent risk markers. The presence of arteriovenous crossings and focal narrowing seems to be linked more closely to the classic cardiovascular risk factors from which the euroSCORE is calculated. The ophathlmolscopic examination of retinal vessels and the analysis of urinary albumin/creatinine ratio seem to complement rather than replace each other.

New molecular knowledge towards the trigemino-cardiac reflex as a cerebral oxygen-conserving reflex

The trigemino-cardiac reflex (TCR) represents the most powerful of the autonomous reflexes and is a subphenomenon in the group of the so-called “oxygen-conserving reflexes”. Within seconds after the initiation of such a reflex, there is a powerful and differentiated activation of the sympathetic system with subsequent elevation in regional cerebral blood flow (CBF), with no changes in the cerebral metabolic rate of oxygen (CMRO₂) or in the cerebral metabolic rate of glucose (CMR_glc). Such an increase in regional CBF without a change of CMRO₂ or CMR_glc provides the brain with oxygen rapidly and efficiently. Features of the reflex have been discovered during skull base surgery, mediating reflex protection projects via currently undefined pathways from the rostral ventrolateral medulla oblongata to the upper brainstem and/or thalamus, which finally engage a small population of neurons in the cortex. This cortical center appears to be dedicated to transduce a neuronal signal reflexively into cerebral vasodilatation and synchronization of electrocortical activity; a fact that seems to be unique among autonomous reflexes. Sympathetic excitation is mediated by cortical-spinal projection to spinal preganglionic sympathetic neurons, whereas bradycardia is mediated via projections to cardiovagal motor medullary neurons. The integrated reflex response serves to redistribute blood from viscera to the brain in response to a challenge to cerebral metabolism, but seems also to initiate a preconditioning mechanism. Previous studies showed a great variability in the human TCR response, in special to external stimuli and individual factors. The TCR gives, therefore, not only new insights into novel therapeutic options for a range of disorders characterized by neuronal death, but also into the cortical and molecular organization of the brain.

Oxygen-conserving reflexes of the brain: the current molecular knowledge

The trigemino-cardiac reflex (TCR) may be classified as a sub-phenomenon in the group of the so-called 'oxygen-conserving reflexes'. Within seconds after the initiation of such a reflex, there is neither a powerful and differentiated activation of the sympathetic system with subsequent elevation in regional cerebral blood flow (CBF) with no changes in the cerebral metabolic rate of oxygen (CMRO(2)) or in the cerebral metabolic rate of glucose (CMRglc). Such an increase in regional CBF without a change of CMRO(2) or CMRglc provides the brain with oxygen rapidly and efficiently and gives substantial evidence that the TCR is an oxygen-conserving reflex. This system, which mediates reflex protection projects via currently undefined pathways from the rostral ventrolateral medulla oblongata to the upper brainstem and/or thalamus which finally engage a small population of neurons in the cortex. This cortical centre appears to be dedicated to reflexively transduce a neuronal signal into cerebral vasodilatation and synchronization of electrocortical activity. Sympathetic excitation is mediated by cortical-spinal projection to spinal pre-ganglionic sympathetic neurons whereas bradycardia is mediated via projections to cardiovagal motor medullary neurons. The integrated reflex response serves to redistribute blood from viscera to brain in response to a challenge to cerebral metabolism, but seems also to initiate a preconditioning mechanism. Better and more detailed knowledge of the cascades, transmitters and molecules engaged in such endogenous (neuro) protection may provide new insights into novel therapeutic options for a range of disorders characterized by neuronal death and into cortical organization of the brain.

[Trigeminocardiac reflex in pituitary surgery. A prospective pilot study]

BACKGROUND

The trigeminocardiac reflex (TCR) is a relatively recently described brainstem reflex in the fields of neurosurgery which leads to a simultaneous drop in mean arterial pressure (MAP) and heart rate of at least 20% from baseline levels after stimulation of a sensible branch of the trigeminal nerve.

PATIENTS AND METHODS

The purpose of this study was to register prospectively for the first time the rate of TCR during trans-sphenoidal surgery and to describe possible predispositional factors. This was examined by determining selected biomarkers thought to correlate with possible intraoperative ischemic events after occurrence of TCR and furthermore with neuroprotective mechanisms ("ischemic tolerance").

RESULTS

Three of the 40 patients included (7.5%) demonstrated intraoperative occurrence of TCR after exposure of the cavernous sinus. One (2.5%) demonstrated a TCR during preparation of the nasal mucosa. Permanent cardiovascular damage or unfavorable postoperative outcome through the appearance of TCR was not found. There was a trend to lower C-reactive protein levels after occurrence of TCR (32 mg/dl vs 14 mg/dl) following normal values before operations in all cases. Considering that no clinical clue of ischemia was detected, this could mean that some neuroprotective cascades are initiated. There was a correlation between tumor necrosis factor A and noradrenalin levels with the size (invasivity) of the pituitary adenoma. The administration of atropine was necessary in only one patient with intraoperative occurrence of TCR.

CONCLUSION

On the basis of this study, it cannot be said to what extent neuroprotective mechanisms after TCR are activated, but a trend is still apparent. Considering the adverse effects and the reflex arc, prophylactic or therapeutic treatment with atropine is not justified.

Different compartments of intracranial pressure and its relationship to cerebral blood flow

BACKGROUND

The classical "Kellie-Monroe" doctrine considering the intracranial volume to be a closed system that is confined within the nearly rigid skull, conserves different mass, and has equal vascular inflow and outflow. Several experimental and clinical studies have given evidence that this is not entirely true from the (patho)physiologic point of view, even so our understanding of this phenomenon is incomplete.

METHODS

Review from the literature.

RESULTS

The present literature review revokes this classical doctrine and suggests a more differentiated description for the dynamic of intracranial pressure (ICP): instead of the previously suggested lumped-parameter models, the authors describe different intracranial compartments that are related to different brain regions.

CONCLUSION

This has the advantage of great practical use on the one hand and allows the demonstration of relevant intercompartimental intracranial pressure differences. In addition, these ICP differences can be revealed to different ICP compartments and to its relationship to CBF. Special reference is given to determine appropriate forms for the nonconstant resistance and compliance parameters.

GDNF family ligands display distinct action profiles on cultured GABAergic and serotonergic neurons of rat ventral mesencephalon

Glial-cell-line-derived neurotrophic factor (GDNF), neurturin (NRTN), artemin (ARTN) and persephin (PSPN), known as the GDNF family ligands (GFLs), influence the development, survival and differentiation of cultured dopaminergic neurons from ventral mesencephalon (VM). Detailed knowledge about the effects of GFLs on other neuronal populations in the VM is essential for their potential application as therapeutic molecules for Parkinson's disease. Hence, in a comparative study, we investigated the effects of GFLs on cell densities and morphological differentiation of gamma-aminobutyric acid-immunoreactive (GABA-ir) and serotonin-ir (5-HT-ir) neurons in primary cultures of E14 rat VM. We observed that all GFLs [10 ng/ml] significantly increased GABA-ir cell densities (1.6-fold) as well as neurite length/neuron. However, only GDNF significantly increased the number of primary neurites/neuron, and none of the GFLs affected soma size of GABA-ir neurons. In contrast, only NRTN treatment significantly increased 5-HT-ir cells densities at 10 ng/ml (1.3-fold), while an augmentation was seen for GDNF and PSPN at 100 ng/ml (2.4-fold and 1.7-fold, respectively). ARTN had no effect on 5-HT-ir cell densities. Morphological analysis of 5-HT-ir neurons revealed a significant increase of soma size, number of primary neurites/neuron and neurite length/neuron after GDNF exposure, while PSPN only affected soma size, and NRTN and ARTN failed to exert any effect. In conclusion, we identified GFLs as effective neurotrophic factors for VM GABAergic and serotonergic neurons, demonstrating characteristic individual action profiles emphasizing their important and distinct roles during brain development.

Effect of GDNF on differentiation of cultured ventral mesencephalic dopaminergic and non-dopaminergic calretinin-expressing neurons

Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor for ventral mesencephalic (VM) dopaminergic neurons. Subpopulations of dopaminergic and non-dopaminergic VM neurons express the calcium-binding proteins calbindin (CB) and calretinin (CR). Characterization of the actions of GDNF on distinct subpopulations of VM cells is of great importance for its potential use as a therapeutic molecule and for understanding its role in neuronal development. The present study investigated the effects of GDNF on the survival and morphological differentiation of dopaminergic and non-dopaminergic neurons in primary cultures of embryonic day (E) 18 rat VM. As expected from our results obtained using E14 VM cells, GDNF significantly increased the morphological complexity of E18 CB-immunoreractive (CB-ir), tyrosine hydroxylase (TH)-ir, and CR-ir neurons and also the densities of CB-ir and TH-ir neurons. Interestingly, densities of E18 CR-ir neurons, contrarily to our previous observations on E14 CR-ir neurons, were significantly higher after GDNF treatment (by 1.5-fold). Colocalization analyses demonstrated that GDNF increased the densitiy of dopaminergic neurons expressing CR (TH+/CR+/CB-), while no significant effects were observed for TH-/CR+/CB- cell densities. In contrast, we found that GDNF significantly increased the total fiber length (2-fold), number of primary neurites (1.4-fold), number of branching points (2.5-fold), and the size of neurite field per neuron (1.8-fold) of the non-dopaminergic CR-expressing neurons (TH-/CR+/CB-). These cells were identified as GABA-expressing neurons. In conclusion, our findings recognize GDNF as a potent differentiation factor for the development of VM dopaminergic and non-dopaminergic CR-expressing neurons.

Subcranial approach in the surgical treatment of anterior skull base trauma

Fractures of the anterior skull base, because of the region's anatomical relationships, are readily complicated by neurological damage to the brain or cranial nerves. This review highlights the use of a subcranial approach in the operative treatment of injuries of the anterior skull base and compares it to the more traditional neurosurgical transcranial approach. The extended anterior subcranial approach takes advantage of the specific features of injuries in this region and allows direct access to the central anterior cranial base in order to repair fractures, close CSF fistulae and relieve of optic nerve compression. It avoids extensive frontal lobe manipulation. The success of the approach in achieving the aims of surgery with low morbidity is reviewed.

Influences of brain tumor-associated pH changes and hypoxia on epileptogenesis

OBJECTIVE

The pathophysiological changes related to epileptic activity in peri- and intra-tumoral tissue are complex and have been only partly understood until now; possible mechanisms involve different structural, biochemical and histological tumor-related alterations.

METHODS

Medical databases were searched for evidence on influence of brain tumor-associated pH changes and hypoxia on epileptogenesis.

RESULTS

During the perioperative period, tumor-related hypoxia and acidity related to tumor neovascularization by vascular endothelial growth factor (VEGF) in combination with angiopoietins 1/2 (ang 1/2), may be a major factor contributing to outcomes involving epileptic activity after surgical tumor removal. Because anaerobic fermentation produces far less ATP than oxidative phosphorlyation per molecule of glucose, increased activity of the glycolytic pathway is necessary to maintain free ATP levels in the hypoxic cell. In mammalian cells, this metabolic switch is regulated by the transcription factor hypoxia-inducible factor-1.

CONCLUSIONS

From the molecular point of view, therapeutic implications for the perioperative period may have relevance for the future.

Positronenemissionstomographie in den Neurowissenschaften

The role of molecular neuroimaging techniques is increasing in the understanding of pathophysiological mechanism of diseases. To date, positron emission tomography is the most powerful tool for the non-invasive study of biochemical and molecular processes in humans and animals in vivo. With the development in radiochemistry and tracer technology, a variety of endogenously expressed and exogenously introduced genes can be analyzed by PET. This opens up the exciting and rapidly field of molecular imaging, aiming at the non-invasive localisation of a biological process of interest in normal and diseased cells in animal models and humans in vivo. Besides its usefulness for basic research positron emission tomography has been proven to be superior to conventional diagnostic methods in several clinical indications. This is illustrated by detection of biological or anatomic changes that cannot be demonstrated by computed tomography or magnetic resonance imaging, as well as even before symptoms are expressed. The present review summarizes the clinical use of positron emission tomography in neuroscience that has helped elucidate the pathophysiology of a number of diseases and has suggested strategies in the treatment of these patients. Special reference is given to the neurovascular, neurodegenerative and neurooncological disease.

The GDNF family members neurturin, artemin and persephin promote the morphological differentiation of cultured ventral mesencephalic dopaminergic neurons

Neurturin (NRTN), artemin (ARTN), persephin (PSPN) and glial cell line-derived neurotrophic factor (GDNF) form a group of neurotrophic factors, also known as the GDNF family ligands (GFLs). They signal through a receptor complex composed of a high-affinity ligand binding subunit, postulated ligand specific, and a common membrane-bound tyrosine kinase RET. Recently, also NCAM has been identified as an alternative signaling receptor. GFLs have been reported to promote survival of cultured dopaminergic neurons. In addition, GDNF treatments have been shown to increase morphological differentiation of tyrosine hydroxylase immunoreactive (TH-ir) neurons. The present comparative study investigated the dose-dependent effects of GFLs on survival and morphological differentiation of TH-ir neurons in primary cultures of E14 rat ventral mesencephalon. Both NRTN and ARTN chronically administered for 5 days significantly increased survival and morphological differentiation of TH-ir cells at all doses investigated [0.1-100 ng/ml], whereas PSPN was found to be slightly less potent with effects on TH-ir cell numbers and morphology at 1.6-100 ng/ml and 6.3-100 ng/ml, respectively. In conclusion, our findings identify NRTN, ARTN and PSPN as potent neurotrophic factors that may play an important role in the structural development and plasticity of ventral mesencephalic dopaminergic neurons.