Congenital deformity of the internal auditory meatus and labyrinth associated with cerebrospinal fluid fistula

A type of inner ear deformity characterised by a tapering internal auditory meatus and dilated, dysplastic labyrinth was demonstrated by tomography in seven patients. Two of these developed cerebrospinal fluid fistulae through the oval window. The path of the fistula in this and other congenital deformities of the inner ear is discussed.

Maxillary sinus mucocele presenting as a late complication of a maxillary advancement procedure

Paranasal sinus mucoceles are benign, locally expansile cyst-like masses that are filled with mucus and lined with epithelium. Less than one per cent of them involve the maxillary sinus. Most of these are late complications of a Caldwell Luc procedure. A case is presented of a 31-year-old woman with a maxillary sinus mucocele who had undergone a Le Fort I maxillary advancement procedure 15 years previously - a complication never previously reported.

Neuro-otological findings in Pendred syndrome

Pendred syndrome is an autosomal recessive inherited disorder characterized by profound hearing impairment and inappropriate iodine release by the thyroid on perchlorate challenge. Thirty-three cases comprising members of 13 families and eight isolated cases were studied, with detailed audiological and vestibular investigation and computerized tomography. A uniform, profound, symmetrical sensorineural hearing loss was identified in all cases. Approximately one-third of the group reported progressive hearing impairment, in childhood or adolescence, associated with head injury, infection, or delayed secondary hydrops. Ninety per cent of the cases scanned showed dilated vestibular aqueducts, and all cases with progression of the hearing impairment demonstrated this structural abnormality. Approximately one-third of the cases had normal vestibular function, but a further third demonstrated a unilateral peripheral deficit, while the remaining third showed bilateral vestibular hypofunction. There was no intra-familial concordance of vestibular findings, and no correlation between vestibular abnormality and presence or absence of a dilated vestibular aqueduct, with or without a Mondini malformation. In older children and adults, Pendred syndrome was associated with a profound, symmetrical, sensorineural auditory impairment, and a variety of vestibular abnormalities, which are not uniform within families, or correlated with structural labyrinthine deformities.

Cochlear implants in children with craniofacial syndromes: assessment and outcomes

The aim of this retrospective study was to review the outcomes for children with craniofacial syndromes who had received a cochlear implant. The group comprised four children (three girls, one boy) aged between 3.3 and 10.1 years (mean 6.3 years) at time of implantation with the Cochlear CI-22M device. Two children had the CHARGE association. one had Goldenhar's syndrome and one had brachio-oculo-facial syndrome. All had full electrode insertion at time of surgery. At follow-up, three of the children demonstrated benefit in detection, recognition and identification of environmental sounds, and they continued to gain receptive spoken language skills, although none had intelligible speech. The group required careful mapping and higher levels of electrical stimulation of the implant compared to normal child implantees. Stimulation of the facial nerve was a problem with one child. The pre-implantation assessment of these children requires extensive interdisciplinary discussion and careful radiological investigation. Cases should be carefully selected. Parents should receive realistic counselling about outcomes and the time commitment necessary, as habilitation of these children can take twice as long as that of children without additional special needs. Post-implantation, these children continue to require well-coordinated medical and interdisciplinary management.

Hyrtl's fissure

Hyrtl's fissure is a transient anatomic landmark in the developing fetal petrous temporal bone and is usually closed by the normal progression of ossification in the 24th week of gestation. It occasionally persists into extrauterine life and has been reported as an unusual cause of a perilabyrinthine cerebrospinal fluid fistula. We present a case of a child presenting with bacterial meningitis because of a persistent Hyrtl's fissure. We have reviewed aspects of the fissure's developmental anatomy and previously published clinical cases. We have also explored the provenance of the eponym. We were unable to uncover evidence in support of the contention that Joseph Hyrtl was actually responsible for describing the structure commonly known as Hyrtl's fissure.

Minimising radiation dose to the lens in axial computed tomography of the temporal

In this study, 25 randomly selected CT scans of temporal bones performed in a busy radiology department were retrospectively analysed with particular attention paid to the number of sections passing through the orbits. Thirteen examinations were found to include sections through the eyes, thereby resulting in unnecessary radiation to the lens. The importance of proper scanning technique is therefore emphasised. The mean radiation dose to the eyes in axial CT examination of the temporal bones was determined by the use of thermoluminescent dosimeters taped to the eyelids. The authors concluded that appropriate scanning techniques can reduce the radiation dose to the orbit whilst imaging the temporal bone. All the relevant information can usually be obtained without any of the sections passing through the lens. The radiation dose to the lens was increased when additional sections were performed to obtain information about the jugular fossa.

Congenital malformations of the ear and cochlear implantation in children: review and temporal bone report of common cavity

The objective of this review is to analyze aspects of congenital malformation of the ear in relation to cochlear implantation in children. Having briefly described the in utero development of the ear and the classification of types of external, middle and inner ear malformation, five practical aspects of these malformations are discussed. It seems likely that the combination of bilateral profound sensorineural deafness with bilateral microtia severe enough to make a surgical approach to the cochlea difficult will be extremely uncommon. No such cases have been reported, although Klippel-Feil deformity seems the syndrome most likely to produce this set of circumstances. Abnormalities in the intratympanic course of the facial nerve have been associated with cochlear malformation, emphasizing the benefit of intra-operative facial nerve monitoring, and a technique suggested for safely avoiding an abnormally placed nerve. Fistulae of cerebrospinal fluid (CSF) and perilymph can complicate surgery and are relatively common in common cavity and Mondini malformations. Strategies for facilitating surgery in the presence of 'gushers', for measuring the pressure of a gusher and for placement of the cochlear implant electrode array are reviewed, with reports of fluctuating levels of electric current when implants lie in dysplastic cochleas. The relationship of implant performance to VIIIth nerve tissue in malformed cochleas is discussed, with a description of the histological findings in a common cavity cochlea. Techniques for identifying the absence of the cochlear nerve are reviewed. Stimulation of the facial nerve by cochlear implants has been described in cases of congenital malformation of the labyrinth but is relatively uncommon. Case reports of the benefit received by implanted children with congenital cochlear malformation have appeared since 1988. Most cases reported have not yet been followed for long enough to establish a clear picture of the outcome following cochlear implantation in such children; no centre has yet built up a large series of cases, but there have been two multicentre postal surveys. It seems likely that in cochlear malformation the range of potential outcomes in terms of hearing threshold and the development of speech perception and production will be similar to the range found in implanted children without cochlear dysplasia. However there is, as yet, no clear picture of the mean level of performance within this range.

Imaging for cochlear implants

All patients in the Birmingham Cochlear Implant Programme underwent computerized tomography (CT) scanning and were assessed and images interpreted by the main author. Of the first 100 cases, 20 were considered to have abnormalities of the inner ears by CT imaging. It is concluded that the commonest abnormality was cochlear otospongiosis followed by labyrinthitis ossificans. Otospongiosis is well shown by CT which gives a good predicator of luminal patency. However, labyrinthus obliterans, although usually apparent on CT, is not reliably shown in all cases and T2 weighted magnetic resonance imaging (MRI) is better.

Enlarged vestibular aqueduct: a radiological marker of pendred syndrome, and mutation of the PDS gene

Although the textbook view of Pendred syndrome is that of an autosomal recessive condition characterized by deafness and goitre, it is increasingly clear that not all such patients present this classical clinical picture. Malformations of the inner ear, specifically enlargement of the vestibular aqueduct, are common in Pendred syndrome and mutations in the PDS (Pendred Syndrome) gene have been recorded in patients presenting with deafness and vestibular aqueduct dilatation only, without other features of Pendred syndrome. Since this is the most common radiological malformation of the cochlea in deaf patients, we investigated what proportion of such cases were due to mutation of the PDS gene. We assessed 57 patients referred with radiological evidence of vestibular aqueduct enlargement, by history, clinical examination, perchlorate discharge test and molecular analysis of the PDS locus. Forty-one patients (72%) had unequivocal evidence of Pendred syndrome. The finding of a single heterozygous mutation at the PDS gene in a further eight was strongly suggestive of a critical role for pendrin, the protein product of the PDS gene, in the generation of enlarged vestibular aqueducts in at least 86% (49/57 cases) of patients with this radiological malformation. Securing the diagnosis of Pendred syndrome may be difficult, especially in the single case. Goitre is an inconstant finding, and the perchlorate discharge test, although helpful, is of diagnostic value only if abnormal. Enlargement of the vestibular aqueduct should be considered as the most likely presentation of Pendred syndrome and should prompt specific investigation of that diagnostic possibility. Pendred syndrome might henceforth be recharacterized as deafness with enlargement of the vestibular aqueduct, which is sometimes associated with goitre.

Histopathological findings suggest the diagnosis in an atypical case of Pendred syndrome

Radiological malformation of the labyrinth, specifically dilatation of the vestibular aqueduct, has been clearly established as a feature in the majority of patients with Pendred syndrome. Mutations of the Pendred syndrome (PDN) gene have been identified in this autosomal recessive form of deafness. There is no direct correlation between the nature of the underlying mutation and the clinical features of deafness, thyroid dysfunction and cochlear malformation. We report a family, the proband of which was thought to deafness secondary to congenital hypothyroidism. At autopsy, histopathological examination of this patient revealed a dilated vestibular aqueduct. Subsequent work on the family has confirmed the diagnosis of Pendred syndrome in the proband and her affected sister.

The common cavity deformity of the ear. A precursor of meningitis but now being implanted

The first succinct description of otogenic meningitis related to the common cavity deformity of the inner ear was made from a post mortem study of 150 years ago. Since then there has been much confusion with less severe malformations of the cochlea, but these patients can now be treated by cochlear implant. It is therefore necessary that an accurate appraisal of the state of the cochlea is made beforehand by computed tomography and by Magnetic Resonance Imaging.

Labyrinthine involvement in Langerhans' cell histiocytosis

BACKGROUND

Langerhans' cell histiocytosis, a rare condition caused by the proliferation of abnormal Langerhans' cells ('LCH cells') and an accompanying granulomatous infiltrate, can affect several organs including the ear. External and middle ear involvement are common with a reported incidence as high as 61%. The bony labyrinth is resistant to erosion by the granulation tissue, thereby protecting the cochlea and vestibular structures. Probably for this reason, involvement of the inner ear is rare, with few case reports in the literature.

PATIENTS

We report two girls, one with bilateral and the other with unilateral mastoid involvement, in whom there was invasion of the labyrinth. The first girl had 'single system' LCH affecting only bone and developed an acute hearing loss due to invasion of the cochlea, while the second had both bone and skin involvement and labyrinthine involvement was diagnosed on imaging prior to the onset of labyrinthine symptoms.

CONCLUSION

Inner ear involvement can lead to permanent deafness, which may be prevented by early institution of treatment. Threatened inner ear involvement requires urgent systemic medical therapy with steroids, possibly combined with chemotherapy.

Cochlear implant failure due to unexpected absence of the eighth nerve--a cautionary tale

We present a case of bilateral absence of the eighth cranial nerve in the internal auditory meatus (IAM). This caused total failure of responses after cochlear implantation in a six-year-old patient with congenital deafness. Pre-operative magnetic resonance (MR) imaging is important to show not only the anatomy of the middle and inner ears but also the structures in the IAM.

Molecular analysis of the PDS gene in Pendred syndrome

Pendred syndrome is an autosomal recessive disorder characterized by the association between sensorineural hearing loss and thyroid swelling or goitre and is likely to be the most common form of syndromic deafness. Within the thyroid gland of affected individuals, iodide is incompletely organified with variable effects upon thyroid hormone biosynthesis, whilst the molecular basis of the hearing loss is unknown. The PDS gene has been identified by positional cloning of chromosome 7q31, within the Pendred syndrome critical linkage interval and encodes for a putative ion transporter called pendrin. We have investigated a cohort of 56 kindreds, all with features suggestive of a diagnosis of Pendred syndrome. Molecular analysis of the PDS gene identified 47 of the 60 (78%) mutant alleles in 31 families (includes three homozygous consanguineous kindreds and one extended family segregating three mutant alleles). Moreover, four recurrent mutations accounted for 35 (74%) of PDS disease chromosomes detected and haplotype analysis would favour common founders rather than mutational hotspots within the PDS gene. Whilst these findings demonstrate molecular heterogeneity for PDS mutations associated with Pendred syndrome, this study would support the use of molecular analysis of the PDS gene in the assessment of families with congenital hearing loss.

Radiological malformations of the ear in Pendred syndrome

Pendred syndrome comprises the association of severe congenital sensorineural deafness with thyroid pathology. Although it is the commonest form of syndromic hearing loss, the primary genetic defect remains unknown. The variable clinical presentation allied to the difficulty in securing the diagnosis have resulted in relatively poor documentation of the radiological features of this syndrome. We now present data on 40 patients, all complying with strict diagnostic criteria for the disorder, and describe our experience of the prevalence of specific malformations of the inner ear as well as comparing the relative merits of computed tomography (CT) and magnetic resonance imaging (MRI) in the investigation of this inherited condition. Deficiency of the interscalar septum in the distal coils of the cochlea (Mondini deformity) was found to be a common but probably not a constant feature of Pendred syndrome. However, enlargement of the endolymphatic sac and duct in association with a large vestibular aqueduct was present in all 20 patients examined by MRI. We conclude that thin section high resolution MRI on a T2 protocol in the axial and sagittal planes is the imaging investigation of choice.

Large endolymphatic sac. A congenital deformity of the inner ear shown by magnetic resonance imaging

Fluctuant and progressive hearing impairment in a patient with a wide vestibular aqueduct has been called the 'large vestibular aqueduct syndrome'. Recently reports of magnetic resonance imaging (MRI) studies describe enlargement of the endolymphatic sac and duct in patients shown to have large vestibular aqueducts by computed tomography (CT). A patient with progressive deafness was shown to have borderline or slightly enlarged vestibular aqueducts by re-formatted sagittal CT. However, MRI in axial and sagittal planes gave a more satisfactory demonstration of both aqueduct and endolymphatic sac enlargement.

Pendred syndrome--100 years of underascertainment?

Pendred syndrome is an autosomal recessive condition classically characterized by deafness and goitre. Since both cochlear and thyroid pathology are required to secure the diagnosis, it is unclear whether the condition might present without the classical features. The perchlorate discharge test, the gold-standard investigation for Pendred syndrome, is non-specific, and in the absence of alternative means of confirming the diagnosis, its sensitivity is unknown. We used the recent mapping of the gene to chromosome 7q to identify pedigrees with a likely diagnosis of Pendred syndrome, and assessed the prevalence of clinical parameters of disease in affected patients. Thirty-six familial cases showed co-segregation between disease and the Pendred syndrome locus on chromosome 7q. Clinical and investigative findings were compared in index cases (n = 18) vs. affected siblings (n = 18). The overall prevalence of goitre was 73%, higher in index cases (94%) than in siblings (56%), many of whom had not previously been considered to have the condition. One perchlorate discharge test was false-negative (2.9%). Radiological malformations of the cochlea were identified in 86% of cases. Securing a diagnosis of Pendred syndrome may be difficult, especially in the single case. The perchlorate discharge test, although valuable, is difficult to undertake in the younger patient, and radiology may assist in diagnosing such patients.

Pendred syndrome: evidence for genetic homogeneity and further refinement of linkage

Pendred syndrome is the association between congenital sensorineural deafness and goitre. The disorder is characterised by the incomplete discharge of radioiodide from a primed thyroid following perchlorate challenge. However, the molecular basis of the association between hearing loss and a defect in organification of iodide remains unclear. Pendred syndrome is inherited as an autosomal recessive trait and has recently been mapped to 7q31 coincident with the non-syndromic deafness locus DFNB4. To define the critical linkage interval for Pendred syndrome we have studied five kindreds, each with members affected by Pendred syndrome. All families support linkage to the chromosome 7 region, defined by the microsatellite markers D7S501-D7S523. Detailed haplotype analysis refines the Pendred syndrome linkage interval to a region flanked by the marker loci D7S501 and D7S525, separated by a genetic distance estimated to be 2.5 cM. As potential candidate genes have as yet not been mapped to this interval, these data will contribute to a positional cloning approach for the identification of the Pendred syndrome gene.

CT screening for temporal bone abnormalities in idiopathic bilateral sensorineural hearing loss

Bilateral sensorineural hearing loss can be caused by a variety of temporal bone abnormalities including primary cochlear otosclerosis, local and systemic bony diseases and some metabolic conditions. These may be identified using computerized tomography (CT), with attenuation recordings taken across the cochlear capsule (CT densitometry). Eighty patients with bilateral sensorineural hearing loss were screened over a period of six and a half years using this technique, and only three cases (3.8 per cent) of treatable disease were detected. Positive yields may be increased by screening selected cases with other clinical or biochemical stigmata of temporal bone disease.

Enhanced magnetic resonance imaging and subtraction techniques in postoperative evaluation of craniofacial resection for sinonasal malignancy

The use of magnetic resonance imaging (MRI) enhanced with gadolinium. and diethylenetriamine pentaacetic acid (DTPA) in the preoperative evaluation of sinonasal malignancy is well established and has an accuracy of over 98%. Since 1979, 208 patients have undergone craniofacial resection at London's Institute of Laryngology & Otology, primarily for sinonasal neoplasia affecting the anterior skull base. Thirty-five "high-risk" patients had MRI at follow-up. The MRI scans were assessed before the patients were examined under anesthesia. MRI was assessed before examination under anesthesia and the results compared with histologic findings demonstrating a reasonable degree of positive correlation but one which is inferior to that found preoperatively (80%). An extension of this technique using the subtraction of T1-weighted MRI with Gd-DTPA highlights areas of increased vascularity, which significantly improves the ability to predict recurrence at the skull base and above the surgical repair in the anterior cranial fossa (94%).

Phenotypic manifestations of branchio-oto-renal syndrome

Branchiootorenal (BOR) syndrome is a variable, autosomal-dominant disorder of the first and second embryonic branchial arches, kidneys, and urinary tract. We describe the phenotype in 45 individuals, highlighting differences and similarities reported in other studies. Characteristic temporal bone findings include cochlear hypoplasia (4/5 of normal size with only 2 turns), dilation of the vestibular aqueduct, bulbous internal auditory canals, deep posterior fossae, and acutely-angled promontories.

The common cavity congenital deformity of the inner ear. An important precursor of meningitis described in 1838

Congenital deformity of the osseous labyrinth of the inner ear is well recognized as being associated with a fistulous communication with the intracranial subarachnoid space in some cases, leading to meningitis or a spontaneous 'stapes gusher'. Such cases have been described inappropriately as 'Mondini's dysplasia'. We cite 2 patients who both died of meningitis and had an accurate postmortem anatomical appraisal of the deformed temporal bones, one recently described by us and one by Cock more than 150 years ago. The use of eponyms is to be deprecated but should faithfully reflect the original description. The 'common cavity' lesion of the inner ear is a most important precursor of otogenic meningitis readily assessed by computed tomography and needing surgery to prevent the egress of cerebrospinal fluid or ingress of pathogens causing meningitis.

Case report: greatly enlarged jugular fossa with progressive sensorineural hearing loss

A case of a five-year-old child with a greatly enlarged jugular fossa and high jugular bulb with associated progressive sensorineural hearing loss is presented. While various forms of this anatomical variant have been described by many authors, this is an extreme example, and progressive symptoms are most unusual.

A comparison of different imaging modalities and direct inspection after periosteal stripping in predicting the invasion of the mandible by oral squamous cell carcinoma

OBJECTIVE

To compare the predictability of orthopantomograms (OPG), bone scans, computerised tomography (CT), magnetic resonance imaging (MRI) and periosteal stripping with direct inspection in predicting both the presence and extent of tumor invasion of the mandible.

DESIGN

Prospective study.

SETTING

Queen Elizabeth Hospital, Birmingham; Wordsley Hospital, Stourbridge; North Staffordshire Royal Infirmary, Stroke-on-Trent.

SUBJECTS

35 consecutive patients requiring a mandibular resection as part of their treatment for oral squamous cell carcinoma.

MAIN OUTCOME MEASURES

The prediction of the extent of bone invasion for each of the investigations and direct inspection after periosteal stripping. The actual extent of invasion of the mandible from a detailed histological assessment.

RESULTS

The OPG underpredicted the width and depth of invasion by on average 13 mm and 2 mm. There were 5 false negative reports. Bone scans overpredicted the width and depth by 14 mm and 15 mm with 1 false negative. CT scans underpredicted the width of invasion by 5 mm and overpredicted depth by 3 mm, but 7 false negatives were returned. MRI scans overpredicted width and depth of invasion by 19 mm and 10 mm with 1 false negative. Direct inspection after periosteal stripping underpredicted the width and depth of invasion by 5 mm and 3 mm with 1 false negative.

CONCLUSION

OPG's and bone scans are useful for the initial assessment of all tumours in the region of the mandible. MRI is a more useful investigation than CT in the assessment of mandibular invasion by oral squamous cell carcinomas. Exploratory periosteal stripping at the time of resection can accurately predict the presence of tumour invading the mandible.

Cochlear dysplasia and meningitis

Congenital dysplasias of the labyrinth of the inner ear are associated with varying degrees of hearing loss. There is a risk of a fistulous communication between the subarachnoid space and the middle ear cavity in some cases that present either as cerebrospinal fluid otorhinorrhea or as recurrent attacks of meningitis. The types of deformity where such a fistula is likely have not been clearly defined. The authors correlated the hearing state with the imaging assessment in 20 patients with congenital malformation of the labyrinth and, in particular, the cochlea. In addition the postmortem histologic findings from one patient with severe cochlear dysplasia who died from otogenic meningitis are described. The key to the assessment is the basal turn of the cochlea. If the basal turn is present and of normal caliber then some hearing is possible and there is no risk of a major fistula. However, if the basal turn is wider than normal or replaced by an undeveloped sac then there is anacusis and very real risk of fistula. In such cases the deformed labyrinth needs to be packed with fibrofatty tissues after just one attack of meningitis.

Ear dysplasia after Mondini

An historical account of descriptions of malformation of the inner ear.

Fast spin echo MRI in otology

Magnetic resonance imaging (MRI) using a fast spin echo protocol (FSE) gives greatly improved spatial resolution for the inner ear and its central connections. Excellent contrast resolution between bone, neural tissue and intracranial fluids is obtained on the heavily T2 weighted images. The contents of the internal auditory meatus (IAM) are shown more clearly than on T1 weighted images, even with gadolinium enhancement. Use of the technique for congenital, vascular, granulomatous and obliterative lesions of the inner ear is described. The cochlear and vestibular nerves can be seen side by side in the majority of cases thereby excluding the presence of even an intrameatal acoustic neuroma. This means that FSE can be used as a first line investigation to exclude small vestibular schwannomas without the need for gadolinium. Gadolinium-enhanced T1 weighted sequences are still necessary for confirmation of some tumours or for inflammatory lesions.

Vocal fold palsy: a re-evaluation of investigations

With easier access to more sophisticated imaging techniques, the investigation of vocal fold palsy is reassessed. A questionnaire was sent to all ENT surgeons in the UK to establish which imaging techniques are available to ENT departments and which tests are currently requested during the investigation of vocal fold palsy. An extensive literature review established the aetiology of vocal fold palsy and the sensitivity and specificity of radiological investigations. A simple protocol is proposed which would be suitable to implement in the majority of ENT departments in the UK.

Imaging of ear deformities in Treacher Collins syndrome

Conductive deafness is a common feature of the Treacher Collins syndrome. The bilateral, essentially symmetrical hypoplastic deformities of middle and external ears, are characteristic. Improved imaging of the deformities using high resolution computed tomography (HRCT) has accompanied a present reluctance to explore surgically these middle ears because of poor results and the increasing success of bone anchored hearing aids. We describe the results of HRCT in 13 patients with Treacher Collins syndrome. An unpneumatized mastoid and a greatly reduced attico-antral region are almost constant findings, but a proportion of patients have a patent external auditory meatus, and, only in these is exploratory surgery feasible. Correction of ossicular deformities may be possible. Patients with atresia of the external auditory meatus are not suitable for exploration and need bone anchored hearing aids. Imaging for these children should be limited with regard to radiation dose and sedation.

Severe cochlear dysplasia causing recurrent meningitis: a surgical lesson

Meningitis may be the sole presenting sign of a cerebrospinal fluid (CSF) fistula of the temporal bone. An eight-year-old boy suffering from recurrent meningitis was found to have bilateral severe cochlear dysplasia. Bilateral tympanotomies were performed, planning to obliterate each vestibule. In the right ear a stapedectomy was performed, resulting in a torrential 'CSF gusher' and difficulty in packing the vestibule. CSF rhinorrhoea requiring revision surgery and two episodes of gram-negative bacterial meningitis complicated the post-operative management, resulting in a prolonged hospital stay. Subsequently, the left ear was managed in a different fashion, leaving the stapes in situ, with grafts placed to seal the oval window niche. We would recommend this alternative procedure in cases of severe cochlear dysplasia, where abnormalities of the vestibule and basal turn of the cochlea mean that performing a stapedectomy to pack the vestibule may result in a severe 'CSF gusher', by opening directly into the subarachnoid space.

Congenital cerebrospinal fluid fistula through the inner ear and meningitis

Congenital deformities of the labyrinth of the inner ear can be associated with a fistulous communication between the intracranial subarachnoid space and the middle ear cavity. We describe seven such cases, six confirmed by high resolution CT and one by postmortem histological section. The seven patients all presented with meningitis although a cerebrospinal fluid fistula was demonstrated at subsequent surgery or postmortem. The lesions were bilateral in three patients, unilateral in three and probably bilateral in the postmortem case although only one temporal bone was obtained. In every case there was a dilated sac instead of the normal two and a half turn cochlea on the affected side and this was confirmed at surgery. The demonstration of the basal cochlear turn is of paramount importance in any deaf child presenting with meningitis. A true Mondini deformity with a normal basal turn and some hearing is not at risk of developing a fistula.

Laryngeal imaging by computerized tomography and magnetic resonance following radiation therapy: a need for caution

For patients with laryngeal tumours, the use of computerized tomography (CT) or magnetic resonance imaging (MR) may facilitate accurate staging by the demonstration of cartilage invasion or tumour extension to areas such as the pre-epiglottic space. The role of imaging in the follow-up of patients after radiotherapy, however, has not been examined. A prospective study of 18 patients undergoing laryngectomy was performed. The results of pre-operative CT and MR imaging were correlated with the pathological findings from whole organ axial sections of the laryngeal specimens. In five patients (28 per cent) both CT and MR images were significantly impaired by movement artefact. In the eight patients without previous radiotherapy, seven had adequate quality imaging and both CT and MR accurately demonstrated the site, size and extent of laryngeal tumour. In eight of the ten patients following radiation therapy the presence of tumour was correctly identified, however there was a poor correlation between the imaging and pathological findings. Two patients had radionecrosis alone. Neither CT nor MR imaging could differentiate between radionecrosis and recurrent tumour.

Subtraction gadolinium enhanced magnetic resonance for head and neck imaging

The subtraction method of Des Plantes has been applied to gadolinium enhanced magnetic resonance imaging (GdMR). Using short acquisition times, T1 weighted spin echo pulse sequences are made immediately before and after the intravenous administration of gadolinium DTPA. To avoid moving the patient from the scanning tunnel the venipuncture is made into the dorsum of the foot. The needle is placed in the vein prior to putting the patient into the scanner and is irrigated with saline while the control series is obtained. 42 patients with naso-sinus or skull base tumours have been successfully investigated by this technique and satisfactory subtraction studies are now obtained on all patients other than the claustrophobic. Subtraction GdMR provides the best demonstration of the effects of gadolinium DTPA on the magnetic resonance signal for both normal and abnormal tissues. The signal recorded on the subtraction image is dependent on tissue blood supply and provides a more accurate record of tumour extent than that shown by unsubtracted GdMR scans.

Cochlear implants for congenital deformities

There have been few accounts of multi-channel cochlear implants in patients with congenital structural deformities of the inner ear which are associated with severe and sometimes progressive deafness. These malformations can now be recognized easily on 2 plane thin section high resolution CT studies which are mandatory for the pre-implantation assessment. However, no attempt seems to have been made to describe which of these malformations would be suitable for an implant or for which would this procedure be contra-indicated. True Mondini deformity of both the cochlea and dilated vestibular aqueduct type would appear suitable for a multi channel implant, but this type of implant should not be used for a primitive otocyst, severe labyrinthine dysplasia or the characteristic X-linked deformity.

Phenotypic evidence for a common pathogenesis in X-linked deafness pedigrees and in Xq13-q21 deletion related deafness

A structural cochlear abnormality has been observed by high resolution CT scanning in some families where X-linked deafness is segregating. We now present evidence that the same abnormality is present in a deaf patient who has a deletion within Xq21. This observation provides phenotypic evidence that the genotypic basis of deafness is the same in both patient groups. It is also likely that the perilymphatic fluid "gusher" abnormality may be common to both.

The foramen lacerum--a route of access to the cranial cavity for malignant tumours below the skull base

Thirteen malignant neoplasms (seven different tumour types) arising in the postnasal space or surrounding soft tissues extended upwards through the skull base into the middle cranial fossa. Gadolinium-enhanced magnetic resonance imaging (GdMRI) clearly revealed the route of the tumour into the cavernous sinus, parasellar region and floor of the middle cranial fossa. Since this extension alters both management and prognosis, GdMRI in the coronal plane is a necessary investigation for persistent and unexplained facial pain in order to demonstrate such lesions of the trigeminal nerve. Differentiation between neoplasms and aggressive inflammatory disease may be difficult.

The imaging characteristics of naso-sinus chondrosarcoma

Eighteen patients with histologically-verified naso-sinus chondrosarcomata are reviewed, emphasizing their CT and MRI appearances. These tumours present with a soft tissue mass expanding and destroying bone and typically (89%) showing areas of nodular or plaque-like calcification on CT. The magnetic resonance characteristics are more specific and when present with the typical CT features are diagnostic of chondrosarcoma. They combine high signal on T2-weighted sequences, with differential enhancement on post-Gadolinium T1-weighted scans. The contrast enhancement is seen at the periphery of the tumour and the central chondromatous core does not enhance. These changes are dependent upon the vascularity of the tissues concerned and have been correlated exactly with the histopathology of the resected tumour specimens.

The basal turn of the cochlea

The coils of the cochlea are now readily demonstrated by thin-section high-resolution computed tomography (CT) in the axial plane. This assessment has become important in severely deaf patients who are candidates for cochlear implant surgery. The commonest abnormality shown in these cases is post-meningitic or tympanogenic labyrinthitis ossificans, which can obstruct the passage of the electrode. Severe otosclerosis can cause a similar problem. Congenital deformities of the labyrinth are rarely suitable for implantation, but the procedure may be indicated for the true Mondini deformity. Implantation is contraindicated for severe dysplasia of the cochlea and for the recently described variety of x-linked deafness with deficient bone at the fundus of the internal auditory meatus.

Detection of recurrent cholesteatoma by computerized tomography after 'closed cavity' mastoid surgery

Pre-operative Computerized Tomography was performed prior to second look operations in 10 cases to check for cholesteatoma after combined approach tympanoplasty. Three independent opinions were obtained on the CT scans and compared with the operative findings. This small series failed to demonstrate reliable pre-operative radiological detection of cholesteatoma. There was disappointing inter-observer agreement in interpretation of the CT scans.

The demonstration of glomus tumours by subtraction MRI

Thirteen patients with 14 glomus tumours have been examined by subtraction gadolinium-enhanced magnetic resonance imaging (MRI), with T1-weighted MR sequences before and after intravenous gadolinium-DTPA. To eliminate movement between subtraction pairs, the patient remains in the tunnel of the imager during administration of the contrast medium, and the venepuncture is made into the dorsum of the foot. The effect of the subtraction process is to remove the NMR signal from the final image so that the photographic densities recorded are dependent on the vascularity of the tissue concerned, normal or abnormal. A particular advantage is the removal of fat signal: the low vascularity of adipose tissue ensures that it is recorded as of minimal density. The extent of skull base glomus tumours has been shown optimally by this technique. Subtraction can also help differentiate glomus tympanicum from glomus jugulare lesions, which may be of crucial importance when deciding the surgical approach. In addition to diagnosis, the technique is also important post-operatively, when imaging is needed to show residual or recurrent tumour and to monitor the effects of radiotherapy.