Biomedical subjects

M D Graham

Publications and source records attributed to M D Graham.

At least 55 records · Page 3Linked to original sources

PubMed1990

Promontory stimulation following labyrinthectomy: implications for cochlear implantation.

Transtympanic electric promontory stimulation is a psychoacoustic test used to assess residual acoustic neurons in profound sensorineural hearing loss. The test was performed in six patients who had previously undergone transmastoid (N = 5) or transcanal-oval window (N = 1) labyrinthectomy as a means of determining the feasibility of future cochlear implantation. Four patients had unilateral Meniere's disease, one had labyrinthitis, and one had delayed onset vertigo. All patients perceived a definite auditory sensation in the labyrinthectomized ear during stimulation. The results of threshold, dynamic range, and difference limen testing were similar to those obtained during preoperative stimulation of cochlear implant candidates (N = 12) who subsequently became successful users. There was no evidence of response degradations as the time following labyrinthectomy increased. The results of this study suggest the possibility of successful cochlear implantation following labyrinthectomy. Supporting histologic data are reviewed.

Acoustic Stimulation↗

PubMed1990

Comparison of three hexagonal tessellations through extraction of blood cell geometric features.

Although image data are almost universally acquired on rectangular sampling lattices, the regular hexagonal lattice offers important theoretical advantages for tessellation of images, particularly when subsequent processing involves operations on local image neighborhoods. The few systems capable of processing hexagonally tessellated images have approximated this tessellation by using image data acquired on a rectangular sampling lattice, from which six of the eight image samples were selected from each local neighborhood. This paper describes a simple method of directly acquiring image data in hexagonal image tessellations; the method is used to compare at constant sampling density the most common of these approximating image tessellations with both a nonregular and a regular hexagonal image tessellation. The test objects were human blood cells, from which features describing cellular geometry were extracted for each image tessellation. Compared to the approximating tessellation, the nonregular tessellation tended to decrease feature means and increase feature variances. In contrast, the regular tessellation tended to increase feature means and decrease feature variances. Consequently, the extracted features showed subtle but consistent differences, with decreasing anisotropic effects and data dispersion for the regular tessellation. In addition, cells contacting others near the 45 degree diagonals were more readily segmented when the image was tessellated on the regular lattice. Expected to be general, these trends recommend use of the regular tessellation, especially when classification accuracy may depend on small differences in several similar geometric features.

Blood Cells↗

PubMed1989

Transmastoid labyrinthectomy: reliable surgical management of vertigo.

Transmastoid labyrinthectomy has continued to be an important part of the surgical armamentarium for patients with vertigo and nonserviceable hearing loss. Continuing experience substantiates our earlier impression that the vestibular system usually accommodates rapidly to complete unilateral surgical ablation, regardless of age or degree of residual vestibular activity in the ear (as measured by preoperative bithermal caloric testing). Although the symptom of vertigo is reliably treated by transmastoid labyrinthectomy, a patient questionnaire has demonstrated a significant incidence of mild to moderate persisting postoperative dysequilibrium. Although this dysequilibrium is usually not debilitating, this questionnaire has demonstrated its existence more precisely than a retrospective review of the patients' clinical records. This study reviews 110 patients who underwent labyrinthectomy between 1978 and 1985. We remain impressed at the efficacy of the transmastoid labyrinthectomy in relieving the symptom of vertigo.

Adult↗

PubMed1989

Total facial nerve decompression for recurrent facial paralysis: an update.

Recurrent facial paralysis (RFP) is a rare disorder that in some individuals may lead to worsening sequelae. Melkersson-Rosenthal syndrome is a variant of RFP that is associated with recurrent facial edema. In the past, decompression of the mastoid segment of the facial nerve has not been successful in preventing recurrences. In 1981 we began performing total facial nerve decompression for RFP and in 1986 reported its efficacy in one patient with Melkersson-Rosenthal syndrome and in another in whom both nerves were decompressed for alternating bilateral paralysis. An additional four cases with 3 to 8 years of followup demonstrate no recurrences in any patient. Total facial nerve decompression for RFP in selected patients appears efficacious in preventing recurrences. Decompression will remain investigational until further followup is obtained. Furthermore, its salutary effect should not be extrapolated to Bell's palsy without further study.

Adolescent↗

PubMed1989

Normal auditory brainstem response in patients with acoustic neuroma.

Auditory brainstem response testing has been a major breakthrough in audiologic screening for acoustic neuroma because of its high degree of sensitivity. Although it is not uncommon for other cerebellopontine angle masses to present with normal ABR findings, reports of eighth nerve tumors with false-negative auditory brainstem response tests are quite rare. A series of 120 acoustic neuromas resected at the University of Michigan was reviewed and revealed two such patients. These two patients presented with asymmetric sensorineural hearing loss and unilateral tinnitus and were found to have completely normal auditory brainstem response. The diagnosis of acoustic neuroma would have been delayed if a comprehensive evaluation had not been pursued.

Adult↗

PubMed1989

Neurophysiologic intraoperative monitoring: II. Facial nerve function.

Intraoperative facial nerve monitoring provides a potentially useful adjunct to recent surgical advances in neurotology and neurosurgery. These measures further aid the surgeon in preserving facial nerve function by enhancing visual identification with electrical monitoring of mechanically evoked facial muscle activation. Facial nerve monitoring in neurotologic surgery may achieve the following goals: (1) early recognition of surgical trauma to the facial nerve, with immediate feedback made available to the surgeon through monitoring of mechanical activation; (2) assistance in distinguishing the facial nerve from regional cranial nerves and from adjacent soft tissue and tumor with selective electrical stimulation; (3) facilitation of tumor excision by electrical mapping of portions of tumor that are remote from the facial nerve; (4) confirmation of nerve stimulability at the completion of surgery; and (5) identification of the site and degree of neural dysfunction in patients undergoing nerve exploration for suspected facial nerve neoplasm or undergoing decompression in acute facial palsy. This paper provides an overview of intraoperative facial nerve monitoring principles and methodology and reports a recent clinical investigation that demonstrates the utility of facial nerve monitoring in translabyrinthine acoustic neuroma surgery.

Electric Stimulation↗

PubMed1989

Magnetic stimulation of the facial nerve.

Electrical testing of the facial nerve has evolved into an important means of assessing neural injury. However, the inability to stimulate the intratemporal facial nerve electrically results in a delay in diagnosis, because axonal degeneration must progress distal to the stylomastoid foramen before testing can be meaningful. To circumvent this problem, we began an investigation of magnetic stimulation of the facial nerve, because pulsed magnetic fields can pass unattenuated through all body structures, including bone. Normal volunteers and one patient with acute facial paralysis were studied with both magnetic and electric stimulation of the facial nerve. The results indicate that (1) magnetic stimulation was more comfortable because high current levels were not required at the skin surface to assure indepth stimulation, (2) magnetic and electric stimulation of the extratemporal facial nerve resulted in nearly identical compound muscle action potentials, indicating that the sites and mechanisms of neural depolarization are similar, and (3) transtemporal magnetic stimulation appears to allow depolarization of the proximal intratemporal nerve. These preliminary results are encouraging and indicate that magnetic stimulation of the facial nerve warrants further investigation.

Action Potentials↗

PubMed1988

Bioactive glass ceramic in ossicular reconstruction: a preliminary report.

Current techniques for ossicular reconstruction include ossicular autografts and homografts, and plastic and ceramic prostheses. Experimental testing of ceramic materials has led to the development of a nonporous, bioactive form of glass ceramic (Ceravital) for tympanoplastic reconstruction. To determine the clinical usefulness of these implants, Ceravital ossicular reconstructions were evaluated in 37 patients treated at the University of Michigan Medical Center during an 18-month period. Thirty-two patients (86%) with chronic ear disease underwent Ceravital ossicular reconstruction with tympanoplasty with or without mastoidectomy. Five other patients (14%) underwent ossicular reconstruction--2 for congenital anomalies, 2 for temporal bone trauma, and 1 patient for glomus tympanicum removal. Patient follow-up ranged from 2.2 to 3.8 years, with a mean follow-up period of 2.9 years. Prosthesis extrusion occurred in one case (3%). Mean preoperative and postoperative (2-year) pure tone air-bone gaps were 41.6 dB and 21.3 dB, respectively. Hearing was improved in 35 of 37 patients (95%). Postoperative pure tone air-bone gap was closed to 20 dB or less in 23 patients (62%). Hearing gains were greater with partial rather than total reconstructions (p = 0.14) and significantly greater with intact canal wall rather than canal wall down tympanoplasties (p less than 0.05). Initial results obtained with the Ceravital ossicular prosthesis compare favorably with those obtained using other methods of alloplastic reconstruction. These preliminary data suggest that Ceravital is an effective alternative prosthetic material for ossicular reconstruction.

Biocompatible Materials↗

PubMed1988

Use of bacitracin for neurotologic surgery.

Wound infection, cerebrospinal fluid leak, and meningitis are serious potential complications of neurotologic procedures that transgress the posterior cranial fossa dura. A study of 236 patients was made to determine the effect of perioperative intravenous antibiotics and topical bacitracin irrigation on the incidence of these complications. Of the 236 patients, 170 (72%) underwent translabyrinthine resection of acoustic tumors, while 66 (28%) underwent retrolabyrinthine vestibular nerve section. Patients were divided into four groups: those who received no antibiotics, those who received perioperative intravenous antibiotics only, those who received topical bacitracin irrigation only, and those who received a combination of perioperative intravenous antibiotics and topical bacitracin irrigation. There were no untoward effects of either perioperative intravenous antibiotics or topical bacitracin. The results indicate that bacitracin irrigation reduced the incidence of wound infection from 9% to 2% (p less than 0.05); of cerebrospinal fluid leak from 12% to 5% (p less than 0.04); and of all targeted complications combined from 22% to 9% (p less than 0.006). Furthermore, the topical bacitracin irrigation only group showed a statistically significant reduction in wound infections compared to the perioperative intravenous antibiotic only group (p less than 0.02). The incidence of meningitis was statistically unaffected by any of our treatment protocols.

Bacitracin↗

PubMed1987

Improving splintage techniques in pyeloplasty.

One hundred patients undergoing pyeloplasty were studied and the outcome assessed with particular reference to the splintage technique used. A double J stent was used in 16 patients instead of a more traditional external drainage technique. The use of the double J stent for splintage of a pyeloplasty anastomosis was associated with a marked reduction in hospital stay and with fewer post-operative complications when compared with external drainage techniques. The double J stent is recommended in cases where a pyeloplasty anastomosis is to be splinted.

Adolescent↗

PubMed1987

Primary adenocarcinoma of the temporal bone mimicking paragangliomas: radiographic and clinical recognition.

Three cases of primary adenocarcinoma of the temporal bone which simulated a glomus jugulare tumor (on the basis of a thorough preoperative evaluation) are detailed. In each case, a vascular mass was seen beneath an intact tympanic membrane and angiography revealed the presence of a highly vascular mass centered on the jugular bulb. Computed tomography revealed erosive changes within the jugular fossa that were characteristic of a glomus jugulare tumor; in two cases, a significant posterior fossa extension was documented. The intraoperative findings failed to suggest a lesion different from paraganglioma in two of the cases; in the remaining case, the erosion of both bone and dura was diffuse and more suggestive of a malignant neoplasm. A discussion of the clinical behavior of adenocarcinomas of the middle ear is included in order to emphasize the importance of differentiating these lesions preoperatively from the more commonly encountered paragangliomas.

Adenocarcinoma, Papillary↗

PubMed1987

Electroneurography: preoperative facial nerve assessment for tumors of the temporal bone.

Tumors of the temporal bone and cerebellopontine angle may be associated with subclinical facial nerve degeneration, despite clinically normal facial function. To determine if preoperative neurophysiologic testing might predict postoperative facial function after tumor surgery, preoperative facial electroneurography (ENoG) was performed in 82 patients with confirmed tumors of the temporal bone and cerebellopontine angle. In patients with acoustic neuroma, preoperative ENoG amplitude reduction varied directly with tumor size. In addition, a statistically significant association between impaired postoperative facial function and acoustic neuroma size greater than 2.5 cm was found. However, preoperative ENoG amplitude reduction did not accurately predict postoperative facial function. These findings suggest that factors, such as the type and size of tumor, the microanatomic relationship between the facial nerve and the neoplasm, and/or desynchronization of the evoked motor-unit volley, may effect results obtained with ENoG in this setting.

Cerebellar Neoplasms↗

PubMed1986

Magnetic resonance imaging of temporal bone and cerebellopontine angle lesions.

Lesions of the temporal bone and cerebellopontine angle present a diagnostic challenge because of the complex anatomy, multiplicity of lesions, and difficulty in imaging the dense bone of this area. Magnetic resonance imaging, a new, nonionizing imaging modality, dependent on monitoring a radiofrequency signal emitted by excited nuclei in an external magnetic field, has shown promise in imaging of the temporal bone and posterior fossa.

Adult↗

PubMed1986

Spontaneous encephalocele of the temporal bone.

Postsurgical and posttraumatic encephaloceles of the tegmen tympani and tegmen mastoideum are well-recognized occurrences. Less frequently recognized, however, is the spontaneous occurrence of an encephalocele associated with cerebrospinal fluid otorrhea or rhinorrhea. This cerebral herniation into the middle ear and the mastoid cavity in adults is associated with a loss of both bony and dural support, and surgical management must deal with both the cerebrospinal fluid leak and herniation of the brain.

Adult↗

PubMed1986

Anatomic basis for labyrinthine preservation during posterior fossa acoustic tumor surgery.

Earlier diagnosis of acoustic tumors promises to increase our opportunity to identify patients with serviceable hearing. Critical to a posterior fossa transmeatal approach for acoustic tumor resection is preservation of the underlying labyrinth. Although the labyrinth has been recognized as a limiting factor in exposure of tumor in the internal auditory canal, few reports have detailed the microscopic surgical anatomy posterior to the internal auditory canal. An anatomic study was undertaken to determine consistent relationships between critical structures within the temporal bone relevant to hearing preservation surgery. The results of this study indicate that, whereas topographic landmarks are helpful for orientation, the more consistent relationship of the labyrinth to the vestibular aqueduct and singular canal allows a more accurate localization of the underlying labyrinth. Although the vestibule frequently prevents direct visualization of the transverse crest, a dissection based upon the microsurgical anatomy will maximize visualization of the lateral fundus while preserving the integrity of the labyrinth.

Cochlea↗

PubMed1986

Electroneurography: preoperative facial nerve assessment in acoustic neuroma surgery: a preliminary study.

Preservation of facial nerve function during acoustic tumor resection is an important goal. Patients with acoustic tumors who present with facial weakness may be at increased risk of postoperative facial paralysis. Subclinical tumor involvement of the facial nerve may be more frequent than is commonly recognized. A preliminary study was undertaken to assess the incidence of subclinical involvement of the facial nerve and to discern if such involvement had prognostic implications. Preoperative facial electroneurography (ENoG) was performed in thirteen patients undergoing surgical resection of acoustic tumors. Three of thirteen patients demonstrated preoperative facial weakness and ENoG was abnormal in all three of these patients. Of the ten patients with normal facial function preoperatively, eight revealed amplitude reduction on ENoG testing. Further study is required to discern the prognostic value of preoperative ENoG abnormalities.

Ear Neoplasms↗

PubMed1986

Total facial nerve decompression in recurrent facial paralysis and the Melkersson-Rosenthal syndrome: a preliminary report.

Recurrent facial paralysis is an infrequent problem for the otolaryngologist. This paralysis may be associated with the Melkersson-Rosenthal syndrome, a triad of recurrent facial paralysis, relapsing facial edema, and associated fissured tongue. Most patients do not have the accompanying stigmata of this syndrome. This paralysis may occur unilaterally or bilaterally. The usual sequelae of recurrent facial paralysis are progressive synkinesis and increasing residual paresis with each episode, and total facial paralysis may be the final outcome. Two patients, one with unilateral Melkersson-Rosenthal syndrome and the other with a bilateral recurrent idiopathic facial paralysis, were treated with combined transmastoid and middle cranial fossa total facial nerve exposure, decompression, and slitting of the fibrous nerve sheath. Postoperatively they have not suffered from facial paralysis during a follow-up period of three years. It appears that this surgical management safely and effectively prevents recurrent facial paralysis unilaterally or bilaterally, whether or not it is associated with the Melkersson-Rosenthal syndrome. Until further experience with this particular management of recurrent facial paralysis is reported, however, caution should be used in recommending it. Additionally, it should not be assumed from this experience that surgical treatment for idiopathic facial paralysis in Bell's palsy is necessarily implied.

Adolescent↗

PubMed1986

The wet ear.

Management of the wet ear is a frustrating problem. Essential to the management of the draining ear is the ability to determine the site of origin and the underlying cause of this drainage. Management of these problems frequently requires acute medical or surgical management followed by long-term therapy to keep the ear dry.

Acute Disease↗