Continuum Field Theory for the Deformations of Planar Kirigami.

Mechanical metamaterials exhibit exotic properties that emerge from the interactions of many nearly rigid building blocks. Determining these properties theoretically has remained an open challenge outside a few select examples. Here, for a large class of periodic and planar kirigami, we provide a coarse-graining rule linking the design of the panels and slits to the kirigami's macroscale deformations. The procedure gives a system of nonlinear partial differential equations expressing geometric compatibility of angle functions related to the motion of individual slits. Leveraging known solutions of the partial differential equations, we present an illuminating agreement between theory and experiment across kirigami designs. The results reveal a dichotomy of designs that deform with persistent versus decaying slit actuation, which we explain using the Poisson's ratio of the unit cell.

The detection matrix as a model-agnostic tool to estimate the number of degrees of freedom in mechanical systems and engineering structures.

Estimating the number of degrees of freedom of a mechanical system or an engineering structure from the time-series of a small set of sensors is a basic problem in diagnostics, which, however, is often overlooked when monitoring health and integrity. In this work, we demonstrate the applicability of the network-theoretic concept of detection matrix as a tool to solve this problem. From this estimation, we illustrate the possibility to identify damage. The detection matrix, recently introduced by Haehne et al. [Phys. Rev. Lett. 122, 158301 (2019)] in the context of network theory, is assembled from the transient response of a few nodes as a result of non-zero initial conditions: its rank offers an estimate of the number of nodes in the network itself. The use of the detection matrix is completely model-agnostic, whereby it does not require any knowledge of the system dynamics. Here, we show that, with a few modifications, this same principle applies to discrete systems, such as spring-mass lattices and trusses. Moreover, we discuss how damage in one or more members causes the appearance of distinct jumps in the singular values of this matrix, thereby opening the door to structural health monitoring applications, without the need for a complete model reconstruction.

Shape-morphing architected sheets with non-periodic cut patterns.

We investigate the out-of-plane shape morphing capability of single-material elastic sheets with architected cut patterns that result in arrays of tiles connected by flexible hinges. We demonstrate that a non-periodic cut pattern can cause a sheet to buckle into three-dimensional shapes, such as domes or patterns of wrinkles, when pulled at specific boundary points. These global buckling modes are observed in experiments and rationalized by an in-plane kinematic analysis that highlights the role of the geometric frustration arising from non-periodicity. The study focuses on elastic sheets, and is later extended to elastic-plastic materials to achieve shape retention. Our work illustrates a scalable route towards the fabrication of three-dimensional objects with nonzero Gaussian curvature from initially-flat sheets.

Neural stem cells and glioblastoma.

Glioblastoma multiforme represents one of the most common brain cancers with a rather heterogeneous cellular composition, as indicated by the term "multiforme". Recent reports have described the isolation and identification of cancer neural stem cells from human adult glioblastoma multiforme, which possess the capacity to establish, sustain, and expand these tumours, even under the challenging settings posed by serial transplantation experiments. Our study focused on the distribution of neural cancer stem cells inside the tumour. The study is divided into three phases: removal of tumoral specimens in different areas of the tumour (centre, periphery, marginal zone) in an operative room equipped with a 1.5 T scanner; isolation and characterization of neural cancer stem cells from human adult glioblastoma multiforme; identification of neural cancer stem cell distribution inside the tumour.

Papillary glioneuronal tumor. Case report and literature review.

OBJECTIVE AND IMPORTANCE: Papillary glioneuronal tumor is a recently described neoplasm composed of gliovascular pseudopapillae associated with intervening neuronal cells ranging from neurocytes to ganglion cells. This tumor is not currently included in the WHO classification of tumors of the central nervous system. We describe a new case of papillary glioneuronal tumor and analyze the data for a series of further 15 patients from international literature. CLINICAL PRESENTATION: A 27-year-old man presented to us for generalized seizure. CT and MRI showed a cystic tumor with mural nodule in the left frontal lobe. INTERVENTION: Frontal craniotomy with gross total removal of the tumor was performed. Histopathological examination was positive for papillary glioneuronal tumor. CONCLUSION: The clinical, radiologic, and pathological features of our case are strikingly similar to those of the previous reported cases. A review of the literature disclosed only 15 other cases of these tumors. It is important that every new case of PGNT is reported to allow its recognition and classification.

Activating PTPN11 mutations play a minor role in pediatric and adult solid tumors.

The PTPN11 gene encodes SHP-2, a widely expressed cytoplasmic protein tyrosine phosphatase functioning as a signaling transducer. Germ-line PTPN11 mutations cause Noonan syndrome (NS), a developmental disorder characterized by an increased risk of malignancies. Recently, a novel class of activating mutations in PTPN11 has been documented as a somatic event in a heterogeneous group of leukemias. Because of the relatively higher prevalence of certain solid tumors in children with NS and the positive modulatory function of SHP-2 in RAS signaling, a wider role for activating PTPN11 mutations in cancer has been hypothesized. Here, we screened a number of solid tumors, including those documented in NS or in which deregulated RAS signaling occurs at significant frequency, for PTPN11 mutations. No disease-associated mutation was identified in rhabdomyosarcoma (n = 13), neuroblastoma (n = 32), melanoma (n = 50), thyroid (n = 85), and colon (n = 48) tumors; a novel missense change, promoting an increased basal phosphatase activity of SHP-2, was observed in one glioma specimen. Our data document that deregulated SHP-2 function does not represent a major molecular event in pediatric and adult tumors, further supporting our previous evidence indicating that the oncogenic role of PTPN11 mutations is cell-context specific.

Extrathecal intraradicular nerve sheath tumor.

OBJECT: The purpose of this study was to analyze the clinical profile of patients harboring extrathecal and intraradicular nerve sheath tumors (NSTs), located inside the sleeve of an extrathecal nerve root and very often within the proximal portion of the spinal nerve, and to evaluate the incidence of long-term dysfunction of the tumor-affected roots if resected. These tumors have not received particular attention in the literature. METHODS: A single-institution series of 16 patients who had undergone surgery for intraradicular NSTs during a 50-year period was selected retrospectively. Data pertaining to clinical features, tumor characteristics, and results of surgery were analyzed. CONCLUSIONS: Extrathecal and intraradicular neurofibromas or schwannomas more frequently affect the lumbar and S-1 nerve roots, often producing root pain only. Selective en bloc enucleation sparing at least part of the motor rootlets is possible for small schwannomas of the extrathecal-preganglion segment of the radix, whereas total resection of the affected root is generally required for radical removal of neurofibromas and large schwannomas. In the authors' experience, neither deafferentation pain nor severe radicular weakness occurs after division of the nerve root harboring the tumor.

Spinal extradural schwannoma.

OBJECT: The authors endeavor to define the clinical and surgery-related profile of spinal nerve sheath tumors located in the extradural space outside both the dural sac and, apparently, the nerve roots' sleeve. METHODS: A series of 24 extradural schwannomas was retrospectively selected after reviewing the notes of spinal nerve sheath tumors surgically treated at La Sapienza University of Rome. Clinical data, tumor-related characteristics, and outcome were analyzed. Women predominantly harbored these tumors. On admission sensory nerve root dysfunction was infrequently reported, whereas pyramidal tract deficits were often present. The tumor, generally large, was most frequently located in the intermediate thoracic segments and high cervical region; only one was reported in the lumbosacral region. Considerable erosion of vertebral bodies was reported in almost one third of the cases. In four patients eloquent nerve roots, that of C-5 in three and that of S-1 in one, were involved with the tumor. Radical tumor resection, with preservation of the nerve roots, was possible in several cases, whereas in two patients manipulation and resection of the C-5 root produced transient and permanent, respectively, root palsy. At follow-up examination patients for whom walking was impossible before surgery were now able to walk. CONCLUSIONS: Extradural schwannomas can be distinguished from other nerve sheath tumors growing inside the spinal canal by their clinicoradiological features and unlikely nerve root origin. After surgery, recovery from pyramidal tract deficits, even severe, is noteworthy; in the authors' experience, however, resection of an involved appendicular root is more likely to result in a permanent and significant radicular deficit.

Idiopathic intracranial hypertrophic pachymeningitis: two case reports and review of the literature.

In 1949, Naffziger et al. first described idiopathic intracranial hypertrophic pachymeningitis (IIHP) as an aseptic, diffuse inflammatory disease that causes thickening of the dura mater and often headache and progressive multiple nerve palsies due to fibrous entrapment or ischemic damage of neurovascular structures. Pachymeningeal thickening can be diffuse or nodular. We report two cases of IIHP; one was affected by diffuse IIHP, while the other presented focal IIHP mimicking a convexity meningioma. We examine the differential diagnosis between IIHP and other known causes of hypertrophic pachymeningitis. We also discuss the clinical bases of treatment.

Intradural lumbar disc herniations: the role of MRI in preoperative diagnosis and review of the literature.

The goal of this article is to report our experience on intradural lumbar disc herniation, consider the causes of this pathology, and analyze it from clinical, diagnostic, and therapeutic perspectives with a particular emphasis on the role of MRI in preoperative diagnosis. We analyzed nine patients treated surgically for intradural lumbar disc hernia. All of them underwent surgery, and hemilaminectomy was performed. In six cases, the diagnosis of intradural herniation was definitive and, in the three remaining, it was confirmed at surgery. In five cases, CT (with no contrast medium) of the lumbar area revealed disc herniation, but none could it confirm its intradural location. Myelography was performed in two cases but also could not prove intradural extrusion. Magnetic resonance imaging study was used in four cases. In five, the postoperative outcome has been excellent. Patients 6 and 9 recovered anal function postoperatively; patient 6 suffered from occasional and mild micturition urgency. The three patients previously operated (1, 2, 7) showed good outcome. Presently, we believe that radiologic diagnosis of intradural herniation is possible in carefully selected patients, thanks to MRI with gadolinium.

Treatment of relevant nerve roots involved in nerve sheath tumors: removal or preservation?

OBJECTIVE: Surgery for the treatment of patients with spinal nerve sheath tumors can require complete resection of the nerve roots involved in the tumor. The purpose of the present study is to analyze the risks of resection of eloquent roots as compared with the risks of incomplete tumor removal. METHODS: The pertinent literature on spinal nerve sheath tumors was reviewed. A single-institution series of 26 patients who underwent operations for 27 spinal schwannomas or neurofibromas, which were removed together with functionally relevant nerve roots (C5-C8 or L3-S1), was studied. RESULTS: Worsening of preoperative radicular motor function was observed at follow-up in 4 (14.8%) of the 27 divided nerve roots, but the motor deficit was permanent and disabling in only 2 cases (7.4%). In the four patients who experienced worsened radicular motor function, the roots were cervical, and histological analysis revealed that the tumor was a schwannoma. Three of these patients were neurologically negative before surgery. Of the two patients with severe radicular weakness, the location of the tumor was extradural and extraradicular in one patient, who had normal preoperative root function, and the tumor was intraextradural in the other patient, who had a preoperative root deficit. CONCLUSION: After resection of a single eloquent nerve root involved in a nerve sheath tumor, the incidence of radicular dysfunction is low but severe weakness is possible. The main risk factors seem to be the pathological pattern (schwannoma versus neurofibroma) of tumor, the preoperative status (with versus without deficit) of the root, and, for extradural nerve sheath tumors, the location (cervical and extraradicular versus lumbosacral and intraradicular) of growth. Deafferentation pain does not occur. Unlike schwannomas with neurofibromatosis Type 2 and neurofibromas, the radicality of removal seems to be the main factor with regard to the recurrence of solitary schwannomas, although recurrent tumors often appear later in follow-up.

Cyst of the medullary conus: malformative persistence of terminal ventricle or compressive dilatation?

The ventriculus terminalis is a cavity situated at the level of the conus medullaris, enclosed by ependymal tissue and normally present as a virtual cavity or as a mere ependymal residue. In rare cases, and almost exclusively in pediatric age, the ventriculus terminalis may be visualized by radiological investigations, either by sonography or MRI, and represents a transient finding in children under 5 years of age. In pathological conditions, a cyst of the conus medullaris is probably the result of a persistent ventriculus terminalis and is usually described in children in association with a tethered cord; in a very limited number of cases, it has been described in adults whose clinical symptoms consist of neurological and/or sphincter disturbances not associated with other pathologies. The authors describe the case of a 42-year-old female with a cyst of the conus whose only symptom was imperious minction; she had been suffering from these urinary disorders for many years. The patient was not operated on because the clinical situation remained stable, without modifications of the MRI in follow-up over a 6-year period. The authors therefore suggest that in adult patients, a cyst of the conus medullaris is probably an expression of malformative persistence of the fifth ventricle and does not necessarily have a progressive evolution.

Surgical treatment of pituitary tumors in the elderly: clinical outcome and long-term follow-up.

Pituitary adenomas in the elderly represent an increasing proportion of pituitary tumors, making the surgical management of these patients of special importance. We therefore decided to review our experience with transsphenoidal surgery (TSS) in this age group, in order to better evaluate its efficacy, safety and outcome. A retrospective study was performed on 39 patients aged more than 70 years at the time of surgery (mean age 74.1 +/- 2.9 years) and with a minimum follow-up duration of 4 years at the time of the study. Thirty-one had a nonfunctioning pituitary adenoma, 5 had a GH-secreting adenoma and 3 a macroprolactinoma, respectively. The commonest presenting symptom was visual deterioration (60%), whereas hypopituitarism were present in 41% of patients. All patients underwent TSS without any major peri- and post-operative complications. Visual fields improved in 74% of patients. Post-operative radiotherapy was performed in 17 patients with partial surgical resection and/or persistent hormonal hypersecretion, whereas 22 patients with subtotal or total surgical resection were treated by surgery only. Long-term follow-up (mean 9.1 +/- 2.7 years) showed evidence for tumor regrowth in one irradiated (5.9%) and 3 non-irradiated patients (13.6%), respectively. A noticeable complication of radiotherapy was progressive hypopituitarism, which worsened or developed in 65% of patients. We conclude that TSS is safe and well tolerated even in elderly patients, with a low incidence of minor complications. The indications for post-operative radiotherapy in patients with incomplete tumor resection should be better defined.