Functional brain networks in Developmental Topographical Disorientation

Despite a decade-long study on Developmental Topographical Disorientation, the underlying mechanism behind this neurological condition remains unknown. This lifelong selective inability in orientation, which causes these individuals to get lost even in familiar surroundings, is present in the absence of any other neurological disorder or acquired brain damage. Herein, we report an analysis of the functional brain network of individuals with Developmental Topographical Disorientation ($n = 19$) compared against that of healthy controls ($n = 21$), all of whom underwent resting-state functional magnetic resonance imaging, to identify if and how their underlying functional brain network is altered. While the established resting-state networks (RSNs) are confirmed in both groups, there is, on average, a greater connectivity and connectivity strength, in addition to increased global and local efficiency in the overall functional network of the Developmental Topographical Disorientation group. In particular, there is an enhanced connectivity between some RSNs facilitated through indirect functional paths. We identify a handful of nodes that encode part of these differences. Overall, our findings provide strong evidence that the brain networks of individuals suffering from Developmental Topographical Disorientation are modified by compensatory mechanisms, which might open the door for new diagnostic tools.

Lost in space(s): Multimodal neuroimaging of disorientation along the Alzheimer's disease continuum

Orientation is a fundamental cognitive faculty and the bedrock of the neurologic examination. Orientation is defined as the alignment between an individual's internal representation and the external world in the spatial, temporal, and social domains. While spatial disorientation is a recognized hallmark of Alzheimer's disease (AD), little is known about disorientation beyond space in AD. This study aimed to explore disorientation in spatial, temporal, and social domains along the AD continuum. Fifty-one participants along the AD continuum performed an ecological orientation task in the spatial, temporal, and social domains while undergoing functional MRI. Disorientation in AD followed a three-way association between orientation domain, brain region, and disease stage. Specifically, patients with early amnestic mild cognitive impairment exhibited spatio-temporal disorientation and reduced brain activity in temporoparietal regions, while patients with AD dementia showed additional social disorientation and reduced brain activity in frontoparietal regions. Furthermore, patterns of hypoactivation overlapped different subnetworks of the default mode network, patterns of fluorodeoxyglucose hypometabolism, and cortical atrophy characteristic of AD. Our results suggest that AD may encompass a disorder of orientation, characterized by a biphasic process manifesting as early spatio-temporal and late social disorientation. As such, disorientation may offer a unique window into the clinicopathological progression of AD. SIGNIFICANCE STATEMENT: Despite extensive research into Alzheimer's disease (AD), its core cognitive deficit remains a matter of debate. In this study, we investigated whether orientation, defined as the ability to align internal representations with the external world in spatial, temporal, and social domains, constitutes a core cognitive deficit in AD. To do so, we used PET-fMRI imaging to collect behavioral, functional, and metabolic data from 51 participants along the AD continuum. Our findings suggest that AD may constitute a disorder of orientation, characterized by an early spatio-temporal disorientation and followed by late social disorientation, manifesting in task-evoked and neurodegenerative changes. We propose that a profile of disorientation across multiple domains offers a unique window into the progression of AD and as such could greatly benefit disease diagnosis, monitoring, and evaluation of treatment response.

The neural correlates of topographical disorientation-a lesion analysis study

Topographical disorientation refers to the selective inability to orient oneself in familiar surroundings. However, to date its neural correlates remain poorly understood. Here we use quantitative lesion analysis and a lesion network mapping approach in order to investigate seven patients with topographical disorientation. Our findings link not only the posterior parahippocampal gyrus (PHG) and retrosplenial cortex but also the lingual gyrus, the precuneus and the fusiform gyrus to topographical disorientation. We propose that topographical disorientation is due to the inability to integrate familiar landmarks within a framework of allocentric and egocentric orientation, supported by a neural network including the posterior PHG, the retrosplenial and the lingual cortex.

A neural circuit for spatial orientation derived from brain lesions

There is disagreement regarding the major components of the brain network supporting spatial cognition. To address this issue, we applied a lesion mapping approach to the clinical phenomenon of topographical disorientation. Topographical disorientation is the inability to maintain accurate knowledge about the physical environment and use it for navigation. A review of published topographical disorientation cases identified 65 different lesion sites. Our lesion mapping analysis yielded a topographical disorientation brain map encompassing the classic regions of the navigation network: medial parietal, medial temporal, and temporo-parietal cortices. We also identified a ventromedial region of the prefrontal cortex, which has been absent from prior descriptions of this network. Moreover, we revealed that the regions mapped are correlated with the Default Mode Network sub-network C. Taken together, this study provides causal evidence for the distribution of the spatial cognitive system, demarking the major components and identifying novel regions.

Pituitary Metastasis in a Patient with Pulmonary Adenocarcinoma Presenting with a Disturbance of Consciousness

BACKGROUND

Brain metastases are one of the main causes of morbidity and mortality of patients with oncological disease. In non-small cell lung carcinoma (NSCLC), the risk of CNS secondary development is 30-50%. An unusual diagnostic and therapeutic problem is the finding of suspicious pituitary lesions. Obtaining a differential diagnosis relies on evaluating the clinical course of the disease (visual disturbances, diabetes insipidus (DI), weakness etc.), and performing endocrinological examinations and imaging analyses (CT, but mainly MRI). Sometimes, however, definitive resolution of the problem requires histological assessment of the tumor.

CASE REPORT

A 65-year-old patient with a newly diagnosed metastatic lung adenocarcinoma was admitted to our department for a first cycle of chemotherapy consisting of cisplatin and navelbine. However, at the beginning of hospitalization, the patient developed qualitative disturbances in consciousness and disorientation. Emergency CT of the CNS revealed a tumor of the pituitary gland, and a subsequent MRI showed intraseller and suprasellar masses making contact with the optic chiasma. An endocrinological examination revealed panhypopituitarism. Pituitary metastasis of NSCLC was confirmed by tumor histology using the trans-sphenoid approach.

CONCLUSION

Lung and breast carcinomas are among the most common cancers to metastasize to the pituitary gland. The incidence of pituitary metastases is reported to be 0.4-28.1%. Clinically, they are mostly silent, but may manifest as endocrine disorders, such as DI, hypothyroidism, and hypocorticism, or as visual disturbances due to compression of the optic nerve. Management depends on the establishment of a correct diagnosis. Key words: hypopituitarism - magnetic resonance imaging - pituitary neoplasm - radiosurgery - targeted therapy The authors declare they have no potential confl icts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers. Submitted: 26. 4. 2018 Accepted: 27. 6. 2018.

June 2001: 61 year old woman with confusion and obtundation

The June COM. A 61 year old female presents with a three week history of increasing confusion, lethargy and headache. A neurological exam revealed disorientation, mild expressive aphasia, bilateral papilledema, and a right pronator drift. She had a craniotomy and resection of tumor. The tumor histologically was consistent with a solitary fibrous tumor displaying malignant features of hypercellularity, marked nuclear atypia, high mitotic activity, and a high proliferation index. This case is unique as the first malignant variant of solitary fibrous tumor to be reported intracranially.

81 year-old male with confusion and weakness

Glioblastoma, the most common primary brain tumor, is a highly infiltrative, malignant astrocytic neoplasm that demonstrates a wide spectrum of morphologic heterogeneity. Cases with a primitive neuroectodermal tumor (PNET)-like component are rare, but are being increasingly recognized and studied. The primitive component typically shows immunohistochemical features that are indicative of potential for divergent differentiation along glial and neuronal pathways; when present, the entire neuraxis may be at risk for involvement, portending a particularly poor prognosis. Recently, data from the largest case series studying malignant gliomas with a PNET-like component suggest that the primitive component likely arises from the malignant glial component. This report presents an example of glioblastoma with a prominent primitive neuroectodermal-like component in an 81 year-old male who, during the course of concurrent chemotherapy and radiation therapy, died five weeks following initial diagnosis.

Diagnostic yield of cerebral imaging in patients with acute confusion

OBJECTIVE

Acute confusion (AC) is a frequent reason for hospital admission in elderly patients. Although in majority of cases the cause is a systemic disorder (e.g., dehydration or septicaemia), patients are frequently subjected to cerebral imaging. This study was undertaken to find clinical predictors of normal cerebral computed tomography (CCT) or magnetic resonance imaging (MRI) scans in AC.

METHODS

Retrospective study of 294 patients admitted with AC of unknown origin, of whom 178 received cerebral imaging.

RESULTS

The rate of pathological imaging studies was 14%. The best single predictor of a normal brain scan was the absence of focal signs. Patients without focal abnormalities and either fever or dehydration had a probability of 0.96 of having a normal CCT or MRI. In demented patients without focal signs, the predictive value for a normal brain scan was 0.98, and if either patients with drowsiness were excluded or the existence of fever or dehydration was added as a selection criterion, all patients had normal scans.

CONCLUSIONS

Patients with AC without focal signs and with either evidence for a medical aetiology of delirium or prediagnosed dementia are at a very low risk of having focal lesions in their CCT or MRI.

Directional disorientation following left retrosplenial hemorrhage: a case report with fMRI studies

We report a 55-year-old right-handed man who presented with topographical disorientation following left retrosplenial hemorrhage. His directional information about familiar places, encoded by previous navigation, was severely impaired, and he could not learn the direction to new places in large-scale spaces beyond the range of visual surveillance. By contrast, he had no difficulties with directional information encoded in a tabletop manner: he could locate major cities or countries on a map, and he also could memorize the spatial relationship of objects in a room. Six months after the ictus, when he had recovered from his directional disorientation, a functional magnetic resonance imaging (fMRI) study of mental navigation demonstrated prominent activation in the retrosplenial area along the right parieto-occipital sulcus and the circumference of the injured area on the left side. The present study, together with previous investigations including clinical case reports, functional neuroimaging, and anatomical and physiological studies on monkeys, suggests that the 'sense of direction' in a large-scale locomotor environment is subserved by the visual area along the parieto-occipital sulcus, and that bilateral deterioration of this function causes directional disorientation.

Assessment and treatment of childhood topographical disorientation: A case study

Topographical disorientation refers to individuals who are unable to find their way around large-scale environments in a normal manner. Childhood topographical disorientation is rarely investigated or reported. Treatment of topographical disorientation is also rare with only one reported treatment study in an adult (Davis & Coltheart, 1999) and no known description of treatment in a child. This paper reports a detailed case analysis of CA, a 6-year-old child with topographical disorientation, and a description of a treatment programme focused on training orientation in the school environment. Assessment of CA revealed mild to moderate visual agnosia in conjunction with severe impairments in general spatial learning and memory, topographical new learning and memory, and a total inability to learn new topographical routes. CA was also unable to use a mental image of his environment, a simple visual plan of his environment or a simple visual map, but was able to follow verbally mediated topographical instructions. The treatment programme focused on improving CA's topographical orientation in the school environment. The programme first involved training in recognition of major school buildings and landmarks and then focused on practical training in route finding along commonly used routes in the school environment. Clear benefits from treatment were evident. The assessment and treatment methods employed provide practical and useful ideas for management of this condition in other children.

Left size distortion (hyperschematia) after right brain damage

OBJECTIVE

To quantitate a size distortion involving the side of space contralateral to the lesion (contralesional) in two right-brain-damaged patients.

METHODS

We studied two right-brain-damaged patients with lesions sparing the occipital lobe and a mild left neglect on target cancellation or line bisection. The lesions involved the temporoparietal region (Patient 1) and the basal ganglia and the insula (Patients 1 and 2). Patients were given drawing tasks and tasks requiring perceptual and visuomotor judgments of horizontal extent.

RESULTS

In drawing objects such as a daisy both from memory and by copying, patients exhibited a disproportionate enlargement of the left-hand side of objects and added more left-sided petals to the drawn daisy. This pathologic behavior persisted when the patients were blindfolded and was likely to reflect a perceptual, rather than premotor, size distortion. In a task requiring the perceptual matching of two rectangles, patients underestimated the left-sided stimulus. In a visuomotor task requiring the reproduction of the horizontal extent of a segment, patients exhibited a hyperextension, when a leftward movement was required.

CONCLUSIONS

We showed a disordered representation of extrapersonal space, possibly involving a contralesional relaxation of the spatial medium. The deficit does not arise at the level of retinotopic coordinate frames and is independent of unilateral spatial neglect.

Clinical and radiographic features of peritumoral infarction following resection of glioblastoma

Focal areas of restricted diffusion adjacent to high-grade glioma resection cavities were detected in 70% of patients on immediate postoperative MRI studies. Follow-up studies demonstrated cystic encephalomalacia in 91% of these foci, suggesting the presence of infarction, and the infarcted tissue demonstrated enhancement in 43% of cases. New postoperative deficits correlated well with the anatomic region of infarction in six patients. Enhancement in perioperative infarcts can mimic tumor progression on follow-up imaging studies.

Evaluation of the clinical presentations in neurobrucellosis

BACKGROUND

Brucellosis is a multisystem disease that may present with a broad spectrum of clinical manifestations and complications. Neurobrucellosis is one of the complications.

METHODS

In this study, we describe our experience in the diagnosis, treatment, and the final outcomes of 20 patients with neurobrucellosis out of 305 patients with brucellosis, within a five-year period between January 1999 and June 2004.

RESULTS

The rate of neurobrucellosis was 6.6%. Twelve males and eight females with a mean age of 37.4 years were investigated. Fever, headache, confusion, and gait disorders were the main complaints. The duration of their complaints varied between one week and six months. On physical examination, 13 patients had fever, six had neck stiffness and confusion, three had motor deficit on either their upper or lower extremities, and four of them had diplopia. The Rose-Bengal test and standard tube agglutination tests were positive in all of the patients. Brucella melitensis was isolated from the blood of six of the 20 (30%) patients. Cerebrospinal fluid (CSF) was analyzed in 18 patients. Pleocytosis with a mean value of 244x10(6)cells/L, and high protein levels were detected in all. A low glucose level in the CSF was detected in ten patients. Patients were treated medically and a complete resolution was achieved in all.

CONCLUSION

Patients with a Brucella infection occasionally manifest central nervous system involvement. Clinicians, especially serving in endemic areas or serving patients coming from endemic areas should consider the likelihood of neurobrucellosis in the patients with unexplained neurological and psychiatric symptoms, and should perform the necessary tests on blood and CSF.

Consciousness and altered consciousness

The notion of consciousness in the English scientific literature denotes a global ability to consciously perform elementary and intellectual tasks, to reason, plan, judge and retrieve information as well as the awareness of these functions belonging to the self, that is, being self-aware. consciousness can also be defined as continuous awareness of the external and internal environment, of the past and the present. The meaning of consciousness is different in various languages, but it invariably includes, the conscious person is capable to learn, retrieve and use information. Disturbance or loss of consciousness in the Hungarian medical language indicates decreased alertness or arousability rather than the impairment of the complex mental ability. Awareness denotes the spiritual process of perception and analysis of stimuli from the inner and external world. Alertness is a prerequisite of awareness. Clinical observations suggest that the lesions of specific structures of the brain may lead to specific malfunction of consciousness, therefore, consciousness must be the product of neural activity. "Higher functions" of human mental ability have been ascribed to the prefrontal and parietal association cortices. The paleocerebrum, limbic system and their connections have been considered to be the center of emotions, feelings, attention, motivation and autonomic functions. Recent evidence indicates that these phylogenetically ancient structures play an important role in the processes of acquiring, storing and retrieving information. The hippocampus has a key role in regulating memory, learning, emotion and motivation. Impaired consciousness in the neurological practice is classified based on tests for conscious behavior and by analyzing the following responses: 1. elementary reactions to sensory stimuli--these are impaired in hypnoid unconsciousness, 2. intellectual reactions to cognitive stimuli--these indicate the impairment of cognitive contents in non-hypnoid unconsciousness. Obviously, disturbance of elementary reactions related to alertness and disturbance of intellectual performance overlap. In conditions with reduced ability to react to or to perceive external stimuli the cognitive disturbance of consciousness cannot fully be explored.

Dural arteriovenous fistulas with aggressive course: clinical and angiographic correlations in two patients

Cranial dural arteriovenous fistulas (DAVFs) usually present with non-aggressive symptoms. We here report two patients who presented a peculiar clinical picture related to DAVFs, with focal neurological signs and haemorrhagic (case 1) or ischaemic lesions (case 2) respectively. The clinical and angiographic findings and putative pathophysiological mechanisms are discussed.

Primary Cerebral Angiitis Containing Marked Xanthoma Cells With Massive Intraparenchymal Involvement-Case Report-

A 27-year-old woman was referred to our hospital with mild disorientation, bilateral abducens nerve palsy, and mild left hemiparesis. Magnetic resonance (MR) imaging revealed diffuse mass lesions resembling malignant glioma in the right frontal intraparenchymal region, with enhancement of multiple meningeal and intraparenchymal nodules. Partial resection of the frontal lesion was performed. Histological examination revealed that the specimens consisted of brain tissue, with marked perivascular infiltration of histiocytes and sheets of xanthomatous cells. The diagnosis was primary cerebral angiitis containing marked xanthoma cells. Steroid therapy was administered over 1 week. MR imaging showed that the remaining lesions resolved gradually, and had disappeared 2 years after surgery. No neurological symptoms or recurrence of the tumor has been observed during the 6-year period since the operation.

Mycobacteriosis in patients with fever of unknown origin

Fever of unknown origin (FUO) is a common syndrome. A total of 94 patients (57 men and 37 women; mean age, 56.3 +/- 19 years, range, 18-86 years) who met the criteria of FUO were included in this study. Mycobacteriosis was diagnosed in 22 (23%) of these patients (13 men and 9 women), including 9 with disseminated disease and 13 with pulmonary disease. There was no significant statistical difference in age, sex, short-term survival status (3 months), and other clinical parameters between patients with and without mycobacteriosis. Clinical manifestations may be specific or nonspecific. The most common initial presentations in patients with mycobacteriosis were respiratory tract symptoms, mainly of cough and dyspnea, observed in 11 (50%) patients, and disturbance of consciousness in 6 (27%). The associated conditions included malnutrition (4 patients, 18%), diabetes mellitus (3, 14%), and renal failure (3, 14%). Four (18%) patients had a history of pulmonary tuberculosis or tuberculous spondylitis in their early adulthood. The 2 most common findings on chest radiograph were interstitial (41%) and nonspecific infiltrative (32%) patterns. In conclusion, mycobacteriosis remains the leading cause of FUO in southern Taiwan and it is important to screen for this treatable disease in all cases of FUO.

Effect of posterior temporal-parietal hematoma on orbital frontal chemistry in relation to a cognitive and anxiety state: a combined 1H-MRS and neuropsychological study of an unusual case as compared with 16 healthy subjects

The authors report the unusual case of a 58-year-old woman (MJP) suffering from left temporal throbbing headache, associated with confusion. Magnetic resonance imaging showed a 5 x 3 x 2 cm hematoma at the left posterior temporal--parietal junction (PTPJ). Repeated MRI of MJP's brain performed during a 4-month follow-up period showed decrease in hematoma size (2.3 x 1.5 x 1) with evidence for development of encephalomalacia and resorption of blood products involving the area of hemorrhage. MJP had mild transcortical sensory aphasia characterized by difficulty with reading and processing, with semantic paraphasic errors while speaking and some difficulty with repetition. MJP had remained normotensive and seizure free, on Vasotec therapy and Dilantin prophylaxis. An in vivo proton magnetic resonance spectroscopy (1H-MRS) performed during an 8-month follow-up period showed reduced concentration for N-acetyl aspartate (NAA) by 19.3% (F=4.09, P<0.04), and myo-inositol by 32.0% (F=5.16, P<0.02) in the left orbital frontal cortex (OFC) as compared with 16 healthy subjects (age- and sex-matched). Cognitive tests (the Wechsler abbreviated scale of intelligence (WASI) and the Stroop color--word interference) showed a significant impairment suggesting involvement of higher-order cognitive functioning (memory, learning, and general intelligence) and attentional system. The Spielberger state-trait anxiety inventory (STAI) showed increased anxiety at the moment of the current examination and decreased tendency to be anxious over a long period of time. The Beck Anxiety and Depression Inventory revealed minimal anxiety and mild to moderate levels of depression. It is hypothesized that the PTPJ hematoma triggered long-distance pathways linking PTPJ area and frontal lobe, including OFC, which resulted in abnormal chemical changes in the left OFC and in cognitive tests impairment, and in long-term anxiety state changes.

Recovery from spontaneous confabulations parallels recovery of temporal confusion in memory

BACKGROUND

In previous studies, the authors found that patients with spontaneous confabulation differ from those with nonconfabulating amnesia by 1) temporal context confusion (TCC) in memory based on an inability to suppress intrusions of currently irrelevant memory traces into ongoing thinking; and 2) lesions involving the orbitofrontal cortex, basal forebrain, or amygdala and perirhinal cortex.

OBJECTIVES

To study the long-term clinical course of spontaneous confabulations, determine whether TCC in memory also parallels the clinical course of spontaneous confabulations, and study the impact of lesion site on clinical course.

METHODS

Eight patients with spontaneous confabulation were re-examined 18 months after onset. Tests of memory and executive functioning and measurement of TCC in memory were again applied. MRI according to a standard protocol was performed to determine areas of permanent damage.

RESULTS

Seven patients eventually stopped confabulating. TCC, but not common memory or executive tests, precisely paralleled the course of spontaneous confabulations. Patients with isolated, less extensive, orbitofrontal lesions stopped confabulating first and had the best neuropsychological outcome. Patients with basal forebrain lesions continued to confabulate for several months and remained amnesic. One patient with extensive orbitofrontal damage and perirhinal cortex damage continues to confabulate after more than 3 years, continuing to confuse memory traces.

CONCLUSIONS

Temporal context confusion in memory is not only the sole feature reliably separating patients with spontaneous confabulation from those with nonconfabulating amnesia in the acute stage, it is also the only feature that precisely parallels the clinical course of spontaneous confabulations. Most patients eventually stop confabulating but duration of confabulations depends on the lesion site.

[Malignant angioendotheliomatosis associated with an acute confusional syndrome: a case report and review of the literature]

We present a case of malignant angioendotheliomatosis (MAE) localized at the central nervous system (CNS) in a 74-years-old male, manifested as an acute confusional syndrome with fever, characteristics of lymphocytic meningitis in the cephalorhachidian liquid (CRL) and dilatation of the left lateral ventricle according to the cranial computerized tomography (CT). The diagnosis was established using post-mortem immunohistological techniques, concluding that it was an intravascular lymphomatous process with secretion of immunoglobulins.

[Multifocal encephalopathy as the principle manifestation of an occult cancer]

We present a patient with an occult adenocarcinoma which manifested clinically as a confusional syndrome due to multiple cerebral infarctions associated to pericarditis and immunological abnormalities. Neurological involvement was secondary to nonbacterial thromboembolic endocarditis (NBTE) which did not provoke cardiac murmurs nor was detected in type B echocardiogram. Malignant cells were not observed in the pericardial effusion or in the pericardial biopsy (1.5 x 1 cm). The clinical picture mimicked an atypical lupous syndrome. The positive diagnosis was established on necropsy. The cardiovascular complications are not frequent in cancer. NBTE usually shows up clinically as a neurologic syndrome due to multiple cerebral infarctions: the normality of complementary exams and the lack of demonstration of an underlying disease do not rule out its diagnosis. When suspecting an NBTE treatment with heparin should be promptly started.

Acute confusional states in the elderly: a radiological evaluation

Computered tomography of the head was carried out on 35 patients who received a hospital diagnosis of delirium according to the DSM-III, and 25 controls without cognitive disturbance. There were no statistically significant differences in the mean age of the groups or in the cortical atrophy score as measured by the mean width of the four largest sulci in the three uppermost tomographic cuts. Instead, the delirious patients differed from the controls in the frontal horn and cella media indices, in the width of the third ventricle and Sylvian fissure at insula on the left side. There was also a significant excess of low attenuation, brain infarct-type areas in the delirious patients. The study confirms the marked predisposing role of the structural brain diseases (primary degenerative and multi-infarct type dementias, Parkinsonism) in the development of acute delirium in elderly patients.

Bilateral and limited amygdalohippocampal lesions causing a pure amnesic syndrome

A pure amnesic syndrome of 21 months' duration occurred in a 36-year-old man following a transient confusional state. The patient died of Hodgkin's disease. At postmortem examination, bilateral and symmetrical neuronal loss, without inflammatory changes, was restricted to the hippocampus and amygdaloid bodies.

Influence of site of origin of lung carcinomas on clinical presentation and central nervous system metastases

A retrospective survey of 100 patients dying from carcinoma of the lung showed that neurological presentation and central nervous system metastases are more frequently present when the primary carcinoma is situated in the peripheral lung tissue (including lung apex). The high incidence of cases presenting neurologically and the high incidence of single secondary deposits involving the central nervous system from peripheral or apical growths suggest a difference in the mode of spread or other properties of such growths compared with the more common central carcinoma.