Histology of the vertebral artery-dural junction: relevance to posterolateral approaches to the skull base

OBJECTIVE

The far-lateral and extreme-lateral infrajugular transcondylar-transtubercular exposure (ELITE) and extreme-lateral transcondylar transodontoid (ELTO) approaches provide access to lesions of the foramen magnum, inferolateral to mid-clivus, and ventral pons and medulla. A subset of pathologies in this region require manipulation of the vertebral artery (VA)-dural interface. Although a cuff of dura is commonly left on the VA to avoid vessel injury during these approaches, there are varying descriptions of the degree of VA-dural separation that is safely achievable. In this paper the authors provide a detailed histological analysis of the VA-dural junction to guide microsurgical technique for posterolateral skull base approaches.

METHODS

An ELITE approach was performed on 6 preserved adult cadaveric specimens. The VA-dural entry site was resected, processed for histological analysis, and qualitatively assessed by a neuropathologist.

RESULTS

Histological analysis demonstrated a clear delineation between the intima and media of the VA in all specimens. No clear plane was identified between the connective tissue of the dura and the connective tissue of the VA adventitia.

CONCLUSIONS

The VA forms a contiguous plane with the connective tissue of the dura at its dural entry site. When performing posterolateral skull base approaches requiring manipulation of the VA-dural interface, maintenance of a dural cuff on the VA is critical to minimize the risk of vascular injury.

Structural Variation Detection by Proximity Ligation from Formalin-Fixed, Paraffin-Embedded Tumor Tissue

The clinical management and therapy of many solid tumor malignancies depends on detection of medically actionable or diagnostically relevant genetic variation. However, a principal challenge for genetic assays from tumors is the fragmented and chemically damaged state of DNA in formalin-fixed, paraffin-embedded (FFPE) samples. From highly fragmented DNA and RNA there is no current technology for generating long-range DNA sequence data as is required to detect genomic structural variation or long-range genotype phasing. We have developed a high-throughput chromosome conformation capture approach for FFPE samples that we call Fix-C, which is similar in concept to Hi-C. Fix-C enables structural variation detection from archival FFPE samples. This method was applied to 15 clinical adenocarcinoma- and sarcoma-positive control specimens spanning a broad range of tumor purities. In this panel, Fix-C analysis achieves a 90% concordance rate with fluorescence in situ hybridization assays, the current clinical gold standard. In addition, novel structural variation undetected by other methods could be identified, and long-range chromatin configuration information recovered from these FFPE samples harboring highly degraded DNA. This powerful approach will enable detailed resolution of global genome rearrangement events during cancer progression from FFPE material and will inform the development of targeted molecular diagnostic assays for patient care.

Need for re-evaluation of current guidelines based on results from germline genetic testing in prostate cancer

5009

Background: Inherited risk for prostate cancer (PCa) is potentially associated with more aggressive disease. Recent data indicate that DNA repair gene abnormalities may be much more common than previously appreciated, especially BRCA2, ATM, CHEK2, BRCA1, RAD51D, and PALB2. Herein, we investigate the efficacy of a targeted gene panel in men with PCa and evaluate clinical factors in relationship to current guidelines for genetic screening. Methods: DNA sequencing and exon-level copy number analysis were performed in 1158 PCa patients (pts) between 2013 and 2016 at a commercial diagnostic laboratory. The genes requisitioned varied but consistently included 14 genes on a hereditary PCa panel, most of which were DNA repair genes. Evaluation included Gleason scores and eligibility for genetic screening based on any NCCN testing criteria in pts with positive findings (pathogenic, likely pathogenic, and risk allele). Results: Pathogenic findings were identified in 199 of 1158 (17.2%) pts, 13 pts (1.0%) had two variants. Roughly 75% of detected variants were in genes on the hereditary PCa panel, of which 34.4% were BRCA1/2. Positive variants in HOXB13, a gene associated only with PCa risk, were identified in eight (3.8%) pts. DNA mismatch repair variants, alterations with substantial known therapeutic implications, were detected in 1.7% of samples. A total of 12.4% of pts with Gleason scores of ≤6, compared with 15.4% of those with scores of ≥7 had a pathogenic variant. Within this cohort, 126 (63%) patients with positive results were eligible for genetic testing based on currently available NCCN guidelines, whereas 73 (37%) would not have qualified. Conclusions: Current NCCN guidelines and Gleason scores cannot be used to reliably stratify PCa pts for the presence/absence of pathogenic germline variants. Most positive results identified in this study have important management implications for pts and their families. The percentage of pts with germline variants who did not meet current genetic screening criteria underscores the need for revisiting current guidelines which cannot, at this time, reliably be used to predict pathologic findings on genetic testing.

Functional screening in Drosophila identifies Alzheimer's disease susceptibility genes and implicates Tau-mediated mechanisms

Using a Drosophila model of Alzheimer's disease (AD), we systematically evaluated 67 candidate genes based on AD-associated genomic loci (P < 10(-4)) from published human genome-wide association studies (GWAS). Genetic manipulation of 87 homologous fly genes was tested for modulation of neurotoxicity caused by human Tau, which forms neurofibrillary tangle pathology in AD. RNA interference (RNAi) targeting 9 genes enhanced Tau neurotoxicity, and in most cases reciprocal activation of gene expression suppressed Tau toxicity. Our screen implicates cindr, the fly ortholog of the human CD2AP AD susceptibility gene, as a modulator of Tau-mediated disease mechanisms. Importantly, we also identify the fly orthologs of FERMT2 and CELF1 as Tau modifiers, and these loci have been independently validated as AD susceptibility loci in the latest GWAS meta-analysis. Both CD2AP and FERMT2 have been previously implicated with roles in cell adhesion, and our screen additionally identifies a fly homolog of the human integrin adhesion receptors, ITGAM and ITGA9, as a modifier of Tau neurotoxicity. Our results highlight cell adhesion pathways as important in Tau toxicity and AD susceptibility and demonstrate the power of model organism genetic screens for the functional follow-up of human GWAS.

Myxoid liposarcoma: a case report of a sentinel metastasis to the parotid gland with molecular confirmation

Myxoid liposarcoma is a subtype of liposarcoma with a predilection for the deep soft tissues of the extremities that accounts approximately for 10% of all adult soft tissue sarcomas. We report a case of a metastatic myxoid liposarcoma to the parotid gland, with fine-needle aspiration cytology correlation and molecular characterization. The lesion was diagnosed in a 53-year-old Hispanic male who presented with a left posterior thigh mass. A core needle biopsy established the diagnosis of myxoid liposarcoma. The patient underwent limb-sparing, wide local excision of the malignancy and later presented with an initial metastatic lesion to the parotid gland. The diagnosis of metastatic myxoid liposarcoma was rendered by fine-needle aspiration cytology with cell block preparation, and molecular confirmation. Although myxoid/round cell liposarcomas are classically described as having minimal pleomorphism on cytologic material, we encountered significant pleomorphism in our case. Therefore, a diagnosis of myxoid/round cell liposarcoma should still be a diagnostic consideration even if markedly pleomorphic cells are seen in fine-needle aspiration biopsies.

KRAS mutation detection in colorectal cancer by a commercially available gene chip array compares well with Sanger sequencing

BACKGROUND

Binding of a ligand to the epidermal growth factor receptor (EGFR) stimulates various intracellular signaling pathways resulting in cell cycle progression, proliferation, angiogenesis and apoptosis inhibition. KRAS is involved in signaling pathways including RAF/MAPK and PI3K and mutations in this gene result in constitutive activation of these pathways, independent of EGFR activation. Seven mutations in codons 12 and 13 of KRAS comprise around 95% of the observed human mutations, rendering monoclonal antibodies against EGFR (e.g. cetuximab and panitumumab) useless in treatment of colorectal cancer.

METHODS

KRAS mutation testing by two different methodologies was compared; Sanger sequencing and AutoGenomics INFINITI® assay, on DNA extracted from colorectal cancers.

RESULTS

Out of 29 colorectal tumor samples tested, 28 were concordant between the two methodologies for the KRAS mutations that were detected in both assays with the INFINITI® assay detecting a mutation in one sample that was indeterminate by Sanger sequencing and a third methodology; single nucleotide primer extension.

CONCLUSIONS

This study indicates the utility of the AutoGenomics INFINITI® methodology in a clinical laboratory setting where technical expertise or access to equipment for DNA sequencing does not exist.

Polymorphisms in TGFbeta and TNFalpha are associated with the myelodysplastic syndrome phenotype

CONTEXT

Myelodysplastic syndromes (MDSs) are characterized by ineffective hematopoiesis, excessive apoptosis, and the aberrant expression of a number of cytokines. The genes encoding these cytokines are significantly polymorphic. It is unknown whether these cytokine polymorphisms are associated with, and may therefore be playing a role in the pathogenesis of, MDS.

OBJECTIVE

To determine if certain polymorphisms in the tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta) cytokines are overrepresented in a cohort of patients with MDSs.

DESIGN

DNA was isolated from the peripheral blood or bone marrow aspirate of 21 patients with MDS. The genotypes for 4 different polymorphisms, 2 in TNFalpha and 2 in TGFbeta1, were determined using single-specific-primer polymerase chain reaction. The allele and genotype frequencies were compared with similar populations in the National Cancer Institute SNP500 database.

RESULTS

In our MDS population, the -308A/A genotype of the TNFalpha gene and the TGFbeta1 allele +29T and genotype +29T/T, each associated with higher levels of expression, were overrepresented in our MDS population.

CONCLUSIONS

Polymorphisms associated with increased expression in the cytokines TNFalpha and TGFbeta1 are overrepresented in the MDS population suggesting that increased TNF-alpha and TGF-beta1 activity may contribute to the susceptibility and/or pathogenesis of MDS. Further studies with larger sample sizes are warranted to confirm our observation.

An assessment of extraction versus nonextraction orthodontic treatment using the peer assessment rating (PAR) index

The extraction of teeth for orthodontic purposes has always been a controversial subject in the specialty. The purpose of this study was to assess the outcome of orthodontic treatment in 100 patients treated with the extraction of four premolars and compare it with the outcome of 100 patients treated without extractions, using the peer assessment rating (PAR) index. Records were selected from 1,198 consecutively completed cases treated by a single provider (MGH) between 1981 and 1995. We chose the first 100 finished patients in each group (extraction and nonextraction) who were under the age of 16 and had no deciduous teeth at the start of treatment. The results of this study show that average treatment time for the extraction group was 29.7+/-6.1 months compared with 26.0+/-7.2 months for the nonextraction group. The extraction group had significantly higher initial PAR scores (T1-PAR ext = 30.01+/-8.20 vs. T1 PAR nonext = 25.21+/-8.55), with greater initial maxillary anterior crowding (PAR ext value = 6.05+/-3.85 vs. PAR nonext value = 4.21+/-2.90) and greater initial overjet (PAR ext value = 1.82+/-1.01 vs. PAR nonext value 1.28+/-1.04). All pretreatment differences were significant at the p < or = 0.0001 level. Although significantly different at the beginning of treatment, both groups were statistically identical at the end (PAR T2 ext = 6.18 + 3.04% reduction = 79.4% compared with PAR T2 nonext = 5.64 + 3.08% reduction = 77.6%). In conclusion, the results demonstrate that, given an additional 3 months of treatment, it is possible for an orthodontist to produce dento-occlusal relationships in extraction patients that are as good as those achieved in nonextraction cases.

Functional and cosmetic reconstruction of the facial lower third associated with placement of the transmandibular implant system

PURPOSE

Conventional preprosthetic procedures have typically focused on improvement of denture base stability and retention and have ignore patients' concerns about facial appearance and articulation difficulties. Soft tissue procedures have been developed, combined with insertion of the transmandibular implant (TMI) system through a submental incision, for functional and cosmetic reconstruction of the lower face to improve speech and facial esthetics, and prevent gingival hyperplasia along the lateral posts of the implant.

PATIENTS

The surgical procedure was evaluated in 146 patients with slight, moderate, severe, and extreme mandibular atrophy classified according to the proportion of muscle origin loss on the edentulous mandible. Preoperative, 3-month, and 1-year postoperative full-face and profile photographs were taken. Patients also were questioned about their satisfaction with their facial appearance and speech at these intervals. Gingival hyperplasia along the TMI posts was scored as present or absent.

RESULTS

Satisfaction with the soft tissue reconstruction in 146 patients treated according to this protocol was high, with almost every patient describing the positive comments they had received from their friends and relatives. Postoperatively, none of the patients requested a temporary denture to use during the 12-week incorporation period, although this was a common cosmetic and speech concern preoperatively. Gingival hyperplasia secondary to muscle pull was controlled satisfactorily.

CONCLUSIONS

With the described technique for placement of the TMI system, not only is masticatory function improved, but also the lower third soft tissues of the face are functionally and cosmetically reconstructed to the satisfaction of the patients.

The transmandibular implant: from progressive bone loss to controlled bone growth

PURPOSE

In a prospective study, 146 consecutive transmandibular implant (TMI) patients were treated according to revised surgical and prosthetic protocols to induce and control bone growth. Revisions included 1) placement of transosseous posts and cortical screws between the mental foramina so that two threads extended beyond the alveolar crest of the mandible without protruding through the mucosa and 2) fabrication of an implant-borne prosthesis that rested on the retromolar pads with a gap of 2 mm between the denture base and the mucosal tissues in the saddle areas.

PATIENTS AND METHODS

Measurements of the height of the mandible were made using a digital millimeter calliper and panoramic radiographs, with the enlargement calculated for each radiograph. The follow-up period ranged from 18 to 51 months.

RESULTS

Bone growth was present in 131 of the 146 patients whereas the bone resorption was arrested in the remaining patients. Increase in bony apposition varied from 9 mm in patients with severe mandibular atrophy to 2 mm in patients with mild atrophy.

CONCLUSION

The revised surgical and prosthetic protocols for TMI insertion and rehabilitation are advocated to prevent further alveolar resorption and to promote bone growth in patients with mandibular atrophy.

Osseous changes following placement of the transmandibular implant system in edentulous mandibles

The transmandibular implant system is designed for the reconstruction and rehabilitation of the endentulous mandible utilizing an extraoral approach. Transmandibular implants were placed in 19 patients and mandibular bony changes were followed using standardized panoramic radiography. Eleven sites were identified on each postoperative radiograph and the percentage of radiographic enlargement was calculated for each site. The true bony changes were then computed for both short-term (9.4 months) and long-term (53.4 months) follow-up. Patients with an average mandibular height in the saddle areas of 3.5 to 8.9 mm showed bilateral bony regeneration in the saddle areas and over the most distal cortical screws of the implants. Most of these bony changes were seen in the first year, but continued beyond that time. Patients with residual bone height of 9.0 to 12.9 mm had little bone change, while patients with bone height of 13.0 to 20.5 mm demonstrated slight resorption. Theories for the observed changes are presented. The transmandibular implant is especially indicated for the severely atrophic mandible because its position within the mandible and the rigid box frame design of the implant promote bilateral bone regeneration distal to the framework of the implant.

Prosthodontic considerations for the transmandibular implant

The transmandibular implant has been designed to provide the patient with a severely atrophic mandible an implant that will bear the masticatory load. Thirteen edentulous patients treated with maxillary complete dentures and mandibular overdentures retained by the transmandibular implant were examined biannually for 2 years. Prosthodontic complications included the development of parafunctional habits, "combination syndrome," and epulis in association with the mandibular denture. Surgery was necessary to control chronic mucosal irritation related to muscle pull in one patient. Among the soft tissue parameters, plaque index, gingival index, and sulcus depth demonstrated statistically significant correlations (Spearman). All patients reported an absence of discomfort and those with previous functional complaints reported the ability to masticate all foods. Patient response to overdenture reconstruction with the transmandibular implant seems to be similar to that observed with the combination case. Oral hygiene appears to be directly related to the soft tissue response.

The transmandibular implant: a 2-year prospective study

Thirteen consecutive patients with complaints of dysfunction and pain associated with a mandibular denture were treated with the transmandibular implant. The implant was placed from a submental approach with an atraumatic surgical technique. No load was placed on the implant for 12 weeks. Patients were evaluated for pain, paresthesia, healing of the submental wound, soft tissue response, radiographic change, and mobility of the implant for a period of 2 years. Patient satisfaction was recorded at the 1- and 2-year examinations. The results demonstrate the reliability and reparability of the transmandibular implant system.