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Biomedical subjects

G T Nager

Publications and source records attributed to G T Nager.

At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

Sclerosteosis involving the temporal bone: clinical and radiologic aspects.

Sclerosteosis is one of the rare, potentially lethal, autosomal recessive, progressive, craniotubular sclerosing bone dysplasias. Syndactyly of the second and third or other fingers is evident at birth. Hyperostosis and sclerosis are most prominent in the skull and tubular bones, and are frequently associated with excessive height and weight. The typical facial deformity is apparent by the age of 5 years. The changes involving the temporal bone include a marked increase in overall dimensions, extreme sclerosis, and narrowing and constriction of the external ear canal, middle ear cleft, internal acoustic meatus, and falloppian canal. Impairment of hearing, as a rule bilateral, is a frequent presenting symptom which may manifest in early childhood. Initially it is an expression of interference with sound conduction; later it may become associated with a loss of sound perception. Impairment of facial nerve function is another salient feature which occasionally is present at birth. As a rule, it manifests initially as a unilateral, recurrent paresis, eventually progressing to a bilateral permanent partial loss of facial nerve function. Since impairments of hearing and facial nerve function are two of the salient features, present at birth or in early childhood, the responsibility for recognizing the disease often falls upon the otolaryngologist. The clinical and radiologic features permit not only early recognition of the disorder but also differentiation from similar bony dysplasias. Hyperosteosis and sclerosis of the skull lead to thickening and distortion of the calvaria, cranial base, and foramen magnum resulting in reduction of the intracranial volume, interference with the cerebral blood flow, resorption of cerebrospinal fluid, and gradual increase of intracranial pressure. Severe headaches resulting from this mechanism often develop in early adulthood, and several patients have died suddenly from impaction of the medulla oblongata in the foramen magnum. Decompression of the transverse sigmoid sinus and jugular bulb may be lifesaving, combined with a posterior, and if necessary, an anterior, craniectomy for decompression. Early decompression of the internal acoustic meatus and falloppian canal may help in the preservation of cochlear and facial nerve function.

Adult↗
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Meningiomas invading the temporal bone with extension to the neck.

Meningiomas are the second largest group of brain tumors after gliomas. They account for 13 to 18 per cent of all primary intracranial neoplasms. The majority occur in the cerebral chamber; only 8 to 9 per cent are located in the cerebellar chamber. Meningiomas are hamartomatous, not truly neoplastic tumors, which arise from dural fibroblasts and particularly from arachnoid cells that tend to cluster around the tips of the arachnoid villi. Their preferential sites correspond closely with the locations where arachnoid villi are most frequently encountered, namely, along the major venous sinuses and their contributory veins, at the foramina of exit of the cranial nerves, and where arachnoid cell clusters are found within the trunk or the perineural sheaths of cranial nerves within or adjacent to the basal foramina. Of all intracranial meningiomas, 20 per cent eventually develop an extracranial extension. These extracranial extensions project, in order of decreasing frequency, to 1) the orbit, 2) the external table of the calvaria, 3) the nasal cavity and paranasal sinuses, and 4) the parapharyngeal (cervical) space. Once a meningioma has gained access to the temporal bone, its tendency to extend beyond the confinements of the skull increases to 43 per cent. The most frequent pathway is through the jugular and lacerate foramina into the parapharyngeal space, where it may manifest as a nasopharyngeal, oropharyngeal, retromaxillary, retromandibular, or cervical neck mass. A meningioma in the parapharyngeal area can represent 1) an extracranial extension of a primary intracranial tumor, 2) a neoplasm arising in the jugular foramen, 3) a neoplasm originating from an arachnoid cell cluster within the trunk of a cranial nerve or its perineural sheaths within or near a neural foramen, or 4) a metastasis to a cervical lymph node from a primary intracranial meningioma. Meningiomas extending to the neck are unique because of their tendency toward extracranial expansion, higher incidence of local recurrence, multicentric growth, and frequent combination with other neoplasms of the central nervous system. They are frequently an expression of the central form of neurofibromatosis (von Recklinghausen's disease).

Adolescent↗
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Neurinomas of the trigeminal nerve.

Trigeminal neurinomas account for about 0.2 per cent of all intracranial tumors and for about 2 to 3 per cent of all intracranial neurinomas. Trigeminal neurinomas occur most frequently in persons in the middle decades of life, with the highest incidence between the ages of 38 and 40 years. They show no sex predilection. Although very rare, trigeminal neurinomas are of considerable interest to the neurotologist because of their relation to the temporal bone, skull base, sphenoid and maxillary sinuses, nasopharynx, infratemporal fossa, and, in rare instances, the oral cavity. In addition to producing disturbances of fifth nerve sensory and motor function, these tumors are often associated with other symptoms, such as occlusion of the eustachian tube (sensation of fullness and conductive hearing loss), otalgia, exophthalmos, paralysis of the third, fourth, and sixth cranial nerves, and signs of posterior fossa involvement (sensorineural hearing loss, tinnitus, cerebellar ataxia, and involvement of cranial nerves VII and IX through XI), any of which may be the initial clinical manifestation of the neurinoma. Symptoms depend on the site of origin and course of development. Bilateral trigeminal neurinomas are a manifestation of the central form of neurofibromatosis.

Adult↗
PubMedDate not supplied

Sclerosteosis involving the temporal bone: histopathologic aspects.

Sclerosteosis is a rare, potentially lethal, autosomal recessive, progressive craniotubular sclerosing bone dysplasia with characteristic facial and skeletal features. The temporal bone changes include a marked increase in overall size, extensive sclerosis, narrowing of the external auditory canal, and severe constriction of the internal auditory meatus, fallopian canal, eustachian tube, and middle ear cleft. Attenuation of the bony canals of the 9th, 10th, and 11th cranial nerves, reduction in size of the internal carotid artery, and severe obliteration of the sigmoid sinus and jugular bulb also occur. Loss of hearing, generally bilateral, is a frequent symptom. It often manifests in early childhood and initially is expressed as sound conduction impairment. Later, a sensorineural hearing loss and loss of vestibular nerve function often develop. Impairment of facial nerve function is another feature occasionally present at birth. In the beginning, a unilateral intermittent facial weakness may occur which eventually progresses to a bilateral permanent facial paresis. The histologic examination of the temporal bones from a patient with sclerosteosis explains the mechanisms involved in the progressive impairment of sound conduction and loss of cochlear, vestibular, and facial nerve function. There is a decrease of the arterial blood supply to the brain and an obstruction of the venous drainage from it. The histopathology reveals the obstacles to decompression of the middle ear cleft, ossicular chain, internal auditory and facial canals, and the risks, and in many instances the contraindications, to such procedures. On the other hand, decompression of the sigmoid sinus and jugular bulb should be considered as an additional life-saving procedure in conjunction with the prophylactic craniotomy recommended in all adult patients.

Adult↗
PubMedDate not supplied

Paget's disease of the temporal bone.

Osteitis deformans Paget is a fairly common, heritable, sometimes progressive disease of bone which affects primarily the axial skeleton and may lead to deformity and weakness. It affects 3% of the population over forty years of age and males more frequently than females. The skull and temporal bones become involved in about two-thirds of the patients. Progressive involvement of the temporal bones may lead to alteration of position, increase in size and change of architecture of the petrous pyramid, external canal, middle ear and inner ear capsule. These changes in turn may produce impairment of hearing (about 30-50% of cases) and vestibular function (20-25%). The clinical, radiological, and pathological manifestations of Paget's disease of the temporal bone are discussed in detail and explained with photomicrographs. Examples of tumor formations and vascular changes are presented.

Age Factors↗
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Cholesterol granuloma involving the temporal bone.

The cholesterol granuloma does not represent an independent clinical or pathological entity, rather it is a term used for the description of a tissue response of the temporal bone, to the presence of a particular foreign body, i.e., cholesterol crystals. Three factors are considered to play an important role in its development: 1) interference with drainage, 2) hemorrhage, and 3) obstruction of ventilation. The cause of the initial hemorrhage may be a hemorrhagic inflammation or diathesis, a trauma or some other form of vascular disorder. Interference with air exchange and clearance can be caused by: tubal blockage, persistent mesenchyme, polypoid changes, scar formations, tympanosclerosis, cholesteatoma, etc. The cholesterol granuloma may develop in any portion of the pneumatic system of the temporal bone and it can be associated with a variety of middle ear disorders. Its principal precursor is the chronic middle ear effusion or serous otitis media. Its clinical expression and hallmark is the "idiopathic hemototympanum," the dark bluish discoloration of the tympanic membrane. Osteitis and bone erosion are manifestations of an unusual, more advanced stage. Resorption of bone, in a rare instance, may lead to extensive destruction of the temporal bone.

Adult↗
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Experimental viral infections of the inner ear. II. Simian virus 40 induced tumors of the temporal bone.

Pathological and virological studies were performed on temporal bones of 23 hamsters which developed tumors subsequent to neonatal inoculation of simian virus 40 (SV40). Four to five months after viral inoculation, 22 hamsters developed undifferentiated sarcomas in the subcutaneous space adjacent to the temporal bone. Nine tumors invaded the temporal bone, occassionally extending to the subarachnoid space but not to the inner ear. Choroid plexus papillomas developed in four animals, with one tumor demonstrating invasion of the cochlear aqueduct, internal auditory canal, and cochlear modiolus. Cells grown from a sarcoma and a choroid plexus papilloma contained tumor antigen and established that the tumors were SV40 virus induced.

Animals↗
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Fibrous dysplasia of the temporal bone. Update with case reports.

Fibrous dysplasia is a fairly common, well demarcated, misdifferentiation of the bone-forming mesenchyme affecting a single, several, or many bones, in which skeletal changes are the salient feature, but in which certain endocrinopathies, abnormal pigmentation of skin and mucous membranes, and occasionally other abnormalities form part of the entire disease process. The clinical and pathological aspects of the disease and its involvement with the temporal bone have been previously discussed. Two recent case histories are added here.

Adult↗
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Osteogenesis imperfecta of the temporal bone and its relation to otosclerosis.

Osteogenesis imperfecta (OI) designates a heterogeneous group of heritable disorders of connective tissue that in addition to bone may affect tendons, ligaments, fascia, skin, sclerae, blood vessels, teeth, and hearing. The current classification identifies at least four major syndrome groups or types. It also recognizes a considerable number of additional syndromes that may represent supplementary types or subgroups. Loss of hearing is the least constant of the prominent features of OI. Its incidence varies between 26% and 60%. In OI, formation and remodelling of bone are variously affected. In the temporal bone the development of the inner ear capsule may be involved severely. In the stapes the disturbance in lamellar bone formation can lead to extreme thinness, dehiscence, and nonunion of the stapedial superstructure with the footplate. Osteogenesis imperfecta can be associated with otosclerosis, another bone dysplasia with a different morphology. Otosclerosis, in turn, may interfere with sound conduction and perception. Thus, the hearing loss encountered in OI may be the result of OI, otosclerosis, or a combination of both.

Adolescent↗
PubMedDate not supplied

Acoustic neurinomas.

Eight nerve tumors account for about 8 to 10% of all intracranial tumors, and for about 71 to 75% of all cerebello-pontine angle tumors. They occur particularly in the middle decades of life and are twice as frequent in females as in males. They originate from the distal neurolemmal portion of the nerve, in most instances, from the vestibular division, and represent a neoplasia of the cells of Schwann. Two prominent types of tissue "A" and "B" of Antoni can be distinguished histologically. Regressive changes are frequent and lend them a colorful appearance. Bilateral eighth nerve tumors occur in about 4%. These tumors reveal certain characteristic differences. The differential diagnosis must include: meningiomas, epidermoids and gliomas, as well as a number of other space-occupying lesions.

Adult↗