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Biomedical subjects

P D Phelps

Publications and source records attributed to P D Phelps.

At least 19 recordsLinked to original sources
PubMed1992

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.

Child↗
PubMed1992

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.

Adult↗
PubMed1992

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.

Carcinoma, Adenoid Cystic↗
PubMed1992

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.

Adolescent↗
PubMed1992

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.

Cholesteatoma↗
PubMed1992

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.

Cochlea↗
PubMed1992

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.

Calcinosis↗
PubMed1991

X-linked deafness, stapes gushers and a distinctive defect of the inner ear.

The association of X-linked mixed deafness with stapes gusher has been recognized for 20 years, and imaging studies by polytomography have shown dilatation of the lateral end of the internal auditory meatus (IAM) in some cases. We have made genetic linkage studies in 7 pedigrees in whom deafness was inherited in an X-linked manner. All patients had a full range of audiometric and vestibular function tests. Thin section high resolution CT in two planes was used to assess the state of the middle and inner ears. We found a distinctive inner ear deformity in some of the deaf males characterised not only by a wide bulbous IAM but more importantly, by deficient or absent bone between the lateral end of the IAM and the basal turn of the cochlea. We believe that this results in a communication between the subarachnoid space in the IAM and the perilymph in the cochlea, leading to perilymphatic hydrops and a "gusher" if the stapes is disturbed. Moreover, some of the obligate female carriers seem to have a milder form of the same anomaly associated with slight hearing loss. Genetic studies on some of the deaf males with apparently normal inner ear anatomy suggest a different locus on the X chromosome and hence a different pathogenesis for the deafness.

Audiometry↗
PubMed1991

The investigation of acoustic neuroma.

Gadolinium-enhanced magnetic resonance (GdMR) is the long awaited, easy and definitive investigation for imaging or excluding small acoustic neuromas. However, on the grounds of cost alone it is unrealistic to submit every patient with mild unilateral sensorineural deafness to GdMR. A screening regime is described which combines simple but effective imaging studies of the internal auditory meatus with clinical testing of vestibular function and objective audiometry. The 'two out of three positive' approach based on these tests has proved to be a reliable screening regime for selecting patients for GdMR.

Audiometry, Evoked Response↗
PubMed1990

Imaging jugulotympanic glomus tumors.

Traditionally, jugulotympanic tumors, also called chemodectomas or paragangliomas, have been evaluated by conventional imaging to show bone erosion and angiography for the definitive diagnosis, location, and extent. More recently, computed tomography has been used to show these features as well as the intracranial extension. Magnetic resonance imaging has added a new dimension, particularly for assessment of intracranial spread and growth downward into the neck. We examined 20 jugulotympanic glomus tumors by computed tomography and magnetic resonance imaging with gadolinium enhancement and believe that these two imaging modalities, combined with clinical assessment, can provide all the necessary information regarding diagnosis, situation, and extent in the majority of jugulotympanic glomus tumors. Gadolinium-enhanced magnetic resonance imaging was particularly effective for the detection of small tumors confined to the middle ear and for confirmation that the jugular bulb was not involved. Consequently, angiography is no longer a first-line imaging investigation but rather a preoperative evaluation only in those tumors in which preoperative embolization is required or occasionally when the extent of the tumor, especially in the jugular bulb, cannot be confidently predicted by noninvasive imaging.

Aged↗
PubMed1990

Imaging cholesteatoma.

Acquired cholesteatoma of the middle ear is usually diagnosed by otoscopy and treated by exploratory surgery. The role of imaging for such cases is as controversial now as it was 10 years ago, despite significant improvements in spatial and contrast resolution resulting from computerised sectional imaging. We examined 16 cases of straightforward acquired middle ear cholesteatomas with MR as well as high resolution CT scanning to assess the possibilities for tissue characterisation. Cases of the much rarer but more important congenital cholesteatoma of the petrous pyramid with a normal eardrum were also diagnosed by CT and MRI. Magnetic resonance will distinguish cholesteatoma from granulation tissue, fluid and the cholesterol granuloma in the middle ear but this differentiation is of no practical value. An expansile lesion in the petrous apex is most likely to be a cholesteatoma or cholesterol granuloma and is well shown but not differentiated by CT. The two types have quite different characteristics on MR protocols and this is important for planning surgical procedures.

Child↗
PubMed1990

Glomus tumours of the ear: an imaging regime.

Jugulotympanic glomus tumours usually present in the middle ear either primarily or as a result of extension upwards from the jugular fossa. Usually they are the initial responsibility of the otologist. If the jugular fossa is involved, special head and neck surgical expertise is required in treatment and spread into the cranial cavity will involve the neurosurgeon. Previously, angiography was used for diagnosis and assessment of the extent of the tumour but it possesses disadvantages. A new protocol has been evolved using high resolution CT combined with MRI including sequences before and after gadolinium-DTPA enhancement. This regimen has been applied successfully in 25 glomus tumours (14 tympanicum and 11 jugulare).

Ear Neoplasms↗
PubMed1990

Adenoid cystic carcinoma: a comparison between CT, MR and Gd MR imaging techniques.

Nasopharyngeal carcinoma continues to be a difficult diagnostic problem in many patients. It is well known that amongst the many and varied manifestations of this disease, a unilateral middle ear effusion in an adult should be regarded with suspicion. Such a case in a 42-year-old patient is presented. In this case the benefit of Gadolinium enhanced magnetic resonance imaging over and above computerized tomography is demonstrated.

Adult↗