A new, treatable source of recurrent meningitis: basioccipital meningocele.

A 19-month-old boy suffered eight episodes of bacterial meningitis. During the ninth episode a meningocele of the basioccipital clivus communicating with the nasopharynx was discovered. Identification of the organism causing the episodes of meningitis was not helpful in pointing to the site of this congenital anatomic defect. Surgical closure of the defect has prevented further recurrences.

Cephaloceles.

The meningoceles and encephaloceles of the calvaria and base of the skull are reviewed with regard to origin and local behavior. An additional variant is added to the subgroup of nasopharyngeal cephaloceles, the basioccipital nasopharyngeal cephalocele, which only recently has become recognized. The clinical importance, techniques for its identification, and surgical management are discussed with the aid of a case report.

Solitary (unicameral) cysts involving the temporal bone.

The primary unicameral cyst which involves the temporal bone is very rare. Only about 30 patients have been reported in the literature during the past ten decades. The lesion is most frequently encountered in the first and second decade of life. In contrast to the other locations in the skeleton, it usually remains asymptomatic for a long time until it causes a deformity or dysfunction. The etiology has so far remained obscure. Its occasional association with malformations of the ears and nasopharynx and other developmental anomalies, its incidental bilateral occurrence, and certain histological aspects may suggest a congenital origin or a localized defect in bone formation and remodeling.

Epidermoids involving the temporal bone: clinical, radiological and pathological aspects.

Epidermoids or congenital cholesteatomas arise from aberrant epithelial remnants and are, therefore, considerd blastomatous malformations. Their predilective sites are the intracranial cavity, the diploe of the skull and the spinal canal. In the base of the skull the temporal bone is the most frequent site. Epidermoids account for about 0.2-1.5 percent of all intracranial tumors. The majority originate in the cerebello-pontine angle where they account for 6-7 percent of all tumors. Their age incidence reveals a great scatter from birth to 80 years. The majority are recognized during the third and fourth decades with the onset of clinical symptoms occurring much earlier. They affect males more frequently than females. Their delicate capsule with a whitish mother-of-pearl sheen lends them a typical appearance. Epidermoids are generally slow growing lesions which may remain asymptomatic for years. The irritative effect of their content, however, can produce symptoms of dysfunction and intense inflammation. Malignant changes occur infrequently. Diploic epidermoids are easily recognized, whereas, intradural epidermoids are more difficult to identify. Epidermoids may arise in the vicinity, on the outer aspect or within the temporal bone. Epidermoids originating in any of these locations have certain characteristic features which may arouse suspicion of their presence. Examples of an epidermoid with origin in the typical locations within the temporal bone and cerebello-pontine angle are discussed to portray their individual characteristics.

Dehiscence or thinning of bone overlying the superior semicircular canal in a temporal bone survey.

OBJECTIVE: To determine the incidence and etiology of dehiscences of bone overlying the superior semicircular canal in a temporal bone archive. DESIGN: A microscopic study was performed of 1000 temporal bones from 596 adults in a university hospital registry. Specimens were sectioned vertically in the plane of the superior semicircular canal. Measurements of minimum bone thickness over the superior canal were made in a subset of 108 randomly chosen specimens. All bones were examined for thinning or dehiscence relative to these norms. Clinical histories, when available, were reviewed. RESULTS: Complete dehiscence of the superior canal was identified in 5 specimens (0.5%), at the middle fossa floor (n = 1) and where the superior petrosal sinus was in contact with the canal (n = 4). In 14 other specimens (1.4%), the bone at the middle fossa floor (n = 8) or superior petrosal sinus (n = 6) was no thicker than 0.1 mm, significantly less than values measured in the control specimens (P<.001). Abnormalities were typically bilateral. Specimens from infants demonstrated uniformly thin bone over the superior canal in the middle fossa at birth, with gradual thickening until 3 years of age. CONCLUSIONS: Dehiscence of bone overlying the superior canal occurred in approximately 0.5% of temporal bone specimens (0.7% of individuals). In an additional 1.4% of specimens (1.3% of individuals), the bone was markedly thin (< or =0.1 mm), such that it might appear dehiscent even on ultra-high-resolution computed tomography of the temporal bone. Sites affected were in the middle fossa floor or a deep groove for the superior petrosal sinus, often bilaterally. These abnormalities may arise from failure of postnatal bone development. Thin areas of bone over the superior canal may be predisposed to disruption by trauma.

Fibrous dysplasia involving the skull base and temporal bone.

OBJECTIVE: To gain a broader appreciation of the clinical presentation, operative treatment, and outcome of patients with fibrous dysplasia involving the skull base. DESIGN: Retrospective review of a clinical case series. SETTING: A single tertiary academic medical center. PATIENTS: Twenty-one patients with histopathologically confirmed fibrous dysplasia involving the skull base cared for over a 15-year-period (1983-1998). MAIN OUTCOME MEASURES: Clinical and radiographic location of the fibrous dysplasia lesions within the skull base, clinical presentation, surgical intervention, and clinical outcome were tabulated for each patient. RESULTS: The ethmoids were most commonly involved (71%), followed by the sphenoid (43%), frontal (33%), maxilla (29%), temporal (24%), parietal (14%), and occipital (5%) bones. The most common presenting features included atypical facial pain and headache, complaints referable to the sinuses, proptosis and diplopia, hearing loss, and facial numbness. Surgical treatment, guided by clinical presentation, ranged from simple biopsy with conservative follow-up to craniofacial resection. CONCLUSIONS: Fibrous dysplasia can present in myriad ways within the skull base. Modern imaging modalities and histopathologic analysis have made diagnosis relatively straightforward. Surgery, particularly in such a challenging region as the skull base, should be reserved for patients with functional impairment or a cosmetic deformity. Because of the benign nature of the condition, the surgery itself should be relatively conservative, with the primary goal being preservation of existing function.

The jugular bulb in otologic surgery: anatomic, clinical, and surgical considerations.

The jugular bulb varies widely in position and dimensions. In certain pathologic conditions there is an increased incidence of jugular bulb enlargement, but such enlargement also occurs without an obvious underlying cause. Jugular bulb enlargment may lead to clinical symptoms for the patient and particular difficulties for the otologic surgeon, not only in the middle ear but also in neurotologic approaches. The different clinical aspects and problems associated with jugular bulb enlargement are discussed with illustrative cases and temporal bone histologic findings.

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.

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.

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.

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.

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.

Relationship of the utriculus and sacculus to the stapes footplate: anatomic implications for sound-and/or pressure-induced otolith activation.

One hundred thirty human temporal bones that were sectioned in the vertical plane were examined to evaluate the relationship between the stapes footplate and the otolith organs. The shortest distance between the footplate and the utriculus was 0.58+/-0.10 mm in the posterior third of the oval window, 1.04+/-0.20 mm in the middle third, and 1.51+/-0.20 mm in the anterior third. The distance from the sacculus to the footplate was 1.33+/-0.20 mm in the middle third of the oval window and 1.31+/-0.18 mm in the anterior third. Membranous connections extending between the utriculus and the footplate were found in 26% of temporal bones. These membranous connections in coexistence with additional anatomic factors such as stapes hypermobility and/or dehiscence of bone within labyrinthine structures may predispose patients to sound- and/or pressure-induced otolith activation. The findings may have implications for different causes of the Tullio phenomenon.

Anatomic variations and anomalies involving the facial canal.

Congenital bony dehiscences in the facial canal result from incomplete closure during development and are observed in approximately 55% of temporal bones. Anomalies involving the facial canal frequently are encountered in malformations of the temporal bone. These anomalies include aberrations of the course of one or all of the segments of the canal; abnormal relation to the oval and round window; bifurcations and trifurcations of the nerve; and associations with dysplasia of the stapes, oval window, external ear canal, and auricle. Rarely, the facial nerve may be hypoplastic or totally absent. Two abnormal vessels occasionally may accompany the facial nerve in the Fallopian canal: a persistent stapedial artery and a persistent lateral capital vein.

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.

The facial canal: normal anatomy, variations and anomalies. I. Normal anatomy of the facial canal.

Modern otologic surgery revolves around the use of the operating microscope. The surgeon must have a thorough knowledge of all structures in the temporal bone, particularly since surgery may now be directed to areas in its deeper portions. Of concern here is the whereabouts of the facial canal in its complex course through the temporal bone. A detailed descriptive anatomy with emphasis on the relations of the facial canal to adjacent structures is presented. The variations in the course of the facial canal are discussed. The location of dehiscences in the bony canal wall are described. Finally, great stress is laid upon presentation of these anomalies known to us which can occur in the course of the facial nerve through the temporal bone. These anomalies have clinical and surgical significance.

Fibrous dysplasia: a review of the disease and its manifestations in the temporal bone.

Fibrous dysplasia is a fairly common, localized misdifferentiation of the bone-forming mesenchyme affecting a single or many bones, in which skeletal aberrations represent the cardinal feature, but in which certain endocrinopathies, abnormal pigmentation of skin and mucous membrane, and occasionally other abnormalities form part of the entire disease process. The craniofacial skeleton is one of its predilective sites and therefore the temporal bone may become involved. In such instances the disease manifests itself with 1) progressive loss of hearing, 2) increasing obliteration of the external ear canal, and 3) enlargement and distortion of the temporal bone. The first part of this communication is concerned with a review of the clinical and pathological aspects of the disease in general. The second part is concerned with a discussion of the clinical manifestations in the temporal bone, based upon analysis of the entire literature and the authors' personal experience. The indications for surgical intervention include 1) maintenance of a normal outer ear canal, 2) preservation of cochlear and vestibular function, and 3) prevention of secondary complications.