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Biomedical subjects

W W Lo

Publications and source records attributed to W W Lo.

At least 19 recordsLinked to original sources
PubMed2000

Jacobson's nerve schwannoma presenting as middle ear mass.

Schwannoma is one of the common benign middle ear space tumors. Middle ear space schwannomas may originate from the nerves of the tympanic cavity or by extensions from outside the middle ear space. In the English-language literature, the facial nerve and chorda tympani nerve, but not yet the tympanic branch of glossopharyngeal nerve (Jacobson's nerve), have been reported as the origins of intrinsic middle ear space schwannomas. We present the clinical and radiologic features of a middle-space schwannoma originating from Jacobson's nerve, and suggest that such a tumor be included in the differential diagnosis of middle ear tumors.

Cranial Nerve Neoplasms↗
PubMed1999

Spontaneous CSF otorrhea caused by abnormal development of the facial nerve canal.

In two patients with surgically proved CSF fistula through the facial nerve canal, MR and CT examinations showed smooth enlargement of the geniculate fossa with CSF signal. In the clinical setting of CSF otorrhea or rhinorrhea, the presence of an enlarged labyrinthine facial nerve canal and enlarged geniculate fossa on CT scans and CSF intensity on MR images strongly suggests a CSF fistula through the facial nerve canal.

Adult↗
PubMed1998

Iatrogenically induced cortical blindness associated with leptomeningeal enhancement.

Leptomeningeal enhancement is usually infective or neoplastic in origin. We present a case in which a patient received total parenteral nutrition via a catheter unknowingly placed within the right vertebral artery. We postulate that the hyperosmolar nature of the infused solution induced temporary osmotic disruption of the blood-brain barrier, resulting in cortical blindness associated with localized leptomeningeal enhancement.

Adult↗
PubMed1997

Papillary endolymphatic sac tumors: CT, MR imaging, and angiographic findings in 20 patients.

PURPOSE: To determine the computed tomographic (CT), magnetic resonance (MR) imaging, and angiographic findings of papillary endolymphatic sac tumors. MATERIALS AND METHODS: Clinical and imaging studies in 20 patients (aged 17-65 years) with histopathologically proved papillary endolymphatic sac tumors were retrospectively reviewed. Patients underwent CT (n = 18), MR imaging (n = 15), or angiography (n = 12). CT scans were evaluated for bone erosion and calcification; MR images, for signal intensity, enhancement patterns, and flow voids; and angiograms, for tumoral blood supply. RESULTS: All tumors were destructive and contained calcifications centered in the retrolabyrinthine region at CT. The MR imaging appearance varied with lesion size; 12 of 15 tumors showed increased signal intensity at T1-weighted imaging. The high-signal-intensity area was circumferential in lesions 3 cm or smaller and was scattered throughout the lesion in advanced tumors. Only tumors larger than 2 cm had flow voids. The blood supply arose predominantly from the external carotid artery. Large tumors had additional supply from the internal carotid and posterior circulation. CONCLUSION: Papillary endolymphatic sac tumors are destructive, hypervascular lesions that arise from the temporal bone retrolabyrinthine region. Increased signal intensity at unenhanced T1-weighted MR imaging is common and may help distinguish these lesions from more common, aggressive temporal bone tumors.

Adenocarcinoma↗
PubMed1995

Metastatic melanoma to the cerebellopontine angle. Clinical and imaging characteristics.

OBJECTIVE: To describe the clinical and imaging features of metastatic melanoma to the cerebellopontine angle (CPA). DESIGN: A case series study with world literature review. SETTING: House Ear Clinic and St Vincent's Hospital, Los Angeles, Calif. PATIENTS: Three cases of metastatic CPA tumors operated on at the House Ear Clinic. INTERVENTIONS: All patients underwent surgical removal of CPA metastatic melanoma. MAIN OUTCOME MEASURE: Survival and duration of disease-free interval are reported. RESULTS: Two patients died of melanoma within 5 months of diagnosis and resection of CPA melanoma metastases. One patient survived for 5 years after undergoing total resection of an isolated CPA melanoma metastasis. Magnetic resonance imaging features were not uniform. CONCLUSIONS: Metastatic melanoma to the CPA should be suspected in patients with a history of melanoma and a rapid progression of audiovestibular or facial nerve symptoms. Surgical removal of solitary metastases to the CPA may be valuable in patients without other melanoma focus; however, the long-term prognosis for patients with CPA melanoma is grim.

Adult↗
PubMed1995

A simple CT method for location of auditory brain stem implant electrodes.

A method for locating auditory brain stem implant electrodes that have been placed in the lateral recess of the fourth ventricle is described. CT bone window images are "inverted" to black on white, then manually superimposed onto soft-tissue window images to enable identification of electrodes in relation to soft-tissue structures.

Brain Stem↗
PubMed1994

High-resolution computed tomography in evaluation of cochlear patency in implant candidates: a comparison with surgical findings.

High-resolution computed tomography (HRCT) is important in the evaluation of cochlear implant candidates. This study examines the accuracy of radiological assessment of cochlear patency in relation to findings at the time of surgery. Older and newer HRCT methods and attending and senior radiologist interpretations are compared in a large series of cochlear implant patients. Subjects were 50 adults (22 to 74 years) and 31 children (2.4 to 11.7 years) who received either a 3M/House or a Nucleus 22-channel cochlear implant. Attending radiologist reports were obtained by chart review and the scans were re-reviewed for this study by a senior radiologist. Accuracy in detecting cochlear ossification ranged from 86.4 per cent for attending radiologists, with all HRCT scans, to 94.7 per cent for the senior radiologist with newer HRCT scans. False positives were rare, but false negatives did occur. Overall, best results were obtained with newer HRCT scans and a senior radiologist. Knowledge of the presence and extent of cochlear ossification is important to the implant surgeon and for patient counselling. Technical guidelines and a check list for interpretation of results are presented.

Adult↗
PubMed1993

Lateral extent of internal auditory canal involvement by acoustic neuromas: a surgical-radiologic correlation.

The sensitivity of gadolinium-enhanced magnetic resonance imaging (MRI) is such that inflamed areas of individual nerves can be visualized. Given this, might the lateral extent of an acoustic neuroma in the internal auditory canal be inaccurately depicted by MRI with gadolinium contrast due to variable enhancement in inflamed neural tissues? The authors studied the correlation between preoperative MRI and intraoperative observation of the lateral extent of tumor in the internal auditory canal (IAC) of 82 patients with acoustic neuromas. The surgeon made a visual determination of tumor extent when the lateral-most aspect of the tumor was exposed. The radiologist, blind to surgical findings, noted the degree of extension into the IAC based on the MRI. The majority (83%) of the tumors involved the lateral third and fundus of the IAC. Agreement between scans and surgical findings was excellent for tumors extending into the lateral third of the IAC, with a test sensitivity of 94 percent and a positive predictive value of 98.5 percent. Knowledge of the accuracy of MRI in demonstrating extent of tumor in the IAC is important in making decisions regarding surgical approach.

Animals↗
PubMed1993

Endolymphatic sac tumors: radiologic appearance.

PURPOSE: To evaluate the radiologic appearance of endolymphatic sac tumors (ELSTs). MATERIALS AND METHODS: Four patients with ELST underwent computed tomography (CT), and two of the four also underwent magnetic resonance (MR) imaging. Their radiologic studies were reviewed for characteristic findings of ELST. RESULTS: Retrolabyrinthine bone destruction was centered at the external aperture of the vestibular aqueduct in all four patients. CT showed irregular bone margins and prominent intratumoral bone in all four patients. At MR imaging, one tumor was almost homogeneous and isointense to gray matter with T1 weighting, and the other was heterogeneous and contained hyper-, hypo-, and isointense foci with T1 and T2 weighting. CONCLUSION: These radiologic changes may help distinguish ELSTs from other tumors of the temporal bone and posterior fossa.

Adenocarcinoma↗
PubMed1993

Auditory brainstem implant: II. Postsurgical issues and performance.

The auditory brainstem implant (ABI) restores some hearing sensations to patients deafened by bilateral acoustic tumors. Electrodes are stable for more than 10 years. In most cases nonauditory side effects can be avoided by judicious selection of the stimulating waveform and electrode configuration. Most perceptual measurements demonstrate that the ABI produces psychophysical and speech performance similar to that of single-channel cochlear implants. ABI patients receive suprasegmental information in speech and significant enhancement of speech understanding when the sound from the ABI is combined with lipreading.

Brain Stem↗
PubMed1993

Reclassification of aggressive adenomatous mastoid neoplasms as endolymphatic sac tumors.

The emerging concept that aggressive adenomatous tumors of the temporal bone arise from the endolymphatic sac and constitute a distinct clinicopathologic entity merits wider recognition. These tumors share a common clinical pattern and exhibit consistent imaging and histopathologic features. Endolymphatic sac tumors (ELSTs) have been mistaken for other neoplasms such as paragangliomas, adenomatous tumors of mixed histology, ceruminomas, and choroid plexus papillomas. A review of the literature shows similarities among case studies of these aggressive adenomatous lesions. An analysis of the data supports the endolymphatic sac as an origin for these tumors. This report also presents an additional case of a less differentiated variant of this rare but important clinicopathologic entity.

Adenoma↗
PubMed1992

Meningiomas of the jugular foramen.

Meningiomas of the jugular foramen manifest the same signs and symptoms as glomus jugulare tumors. They arise from arachnoid cells lining the jugular bulb and grow slowly, infiltrating the temporal bone and posterior fossa. These lesions, however, are more clinically treacherous than glomus tumors. Meningiomas infiltrate surrounding bone and nerve tissue and require wide margins of resection to prevent recurrence. Eight of these lesions have been managed in the past 5 years at the House Ear Clinic using modern imaging and skull base techniques. Two have recurred after "total" microsurgical removal. Presentation, radiologic evaluation, and management guidelines are reviewed.

Adult↗