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Biomedical subjects

M F Mafee

Publications and source records attributed to M F Mafee.

At least 19 recordsLinked to original sources
PubMed2001

Analysis of magnetic resonance imaging-based blood and cerebrospinal fluid flow measurements in patients with Chiari I malformation: a system approach.

OBJECT: A pilot study was performed to assess noninvasively the change in intracranial compliance (ICC) and intracranial pressure (ICP) in patients with Chiari I malformation who undergo foramen magnum decompression. The working hypothesis was that the main effect of the decompressive surgery is a change in ICP. Noninvasive cine phasecontrast magnetic resonance (MR) imaging is a motion-sensitive dynamic MR imaging technique that allows for visualization and quantitation of tissue motion and flow. The authors' group has used dynamic phase-contrast MR imaging to visualize and quantify pulsatile blood and cerebrospinal fluid (CSF) flow in the craniospinal system. METHODS: A system approach has been used to characterize the hemodynamic-hydrodynamic coupling in the craniospinal system and to derive measures for ICC and ICP. Magnetic resonance imaging-based ICC and ICP values are derived from the ratio of the volume and pressure changes that occur naturally during each cardiac cycle. The authors conducted a prospective study of four patients, three of whom were studied before and after decompressive surgery; significant change in MR imaging-derived ICC and ICP values was documented in only one of the three surgically treated patients. A significant change in the dynamics of the intracranial volume change (ICVC) during the cardiac cycle, however, was observed in all three patients. In healthy individuals the ICVC waveform usually consists of the following sequence: monotonic increase in intracranial volume (ICV) during the systolic phase due to increased blood inflow, monotonic decrease in ICV caused by the onset of CSF outflow into the spinal canal, and increase in the venous outflow. A nonmonotonic decline in the ICVC waveform has been observed in all patients with headaches, and a relatively normal waveform was found in those without headaches or whose headaches were resolved or alleviated by the surgery. A "partial-valve" mechanism is proposed as an explanation for the abnormal ICVC dynamics. The monotonic decline in ICVC is interrupted by a "premature" reduction in the CSF outflow. This may be caused by a displacement of the hindbrain into the cervical spinal canal during the systolic phase. This obstructs the CSF flow at the later part of the systolic phase such that the ICV does not continue its gradual decline. Postsurgery, the ICVC waveforms presented a more normal-appearing ICVC dynamics profile. CONCLUSIONS: Magnetic resonance imaging measurement of transcranial CSF and blood flow may lead to a better understanding of the pathophysiology of Chiari malformations and may prove to be an important diagnostic tool for guiding for the treatment of patients with Chiari I malformation.

Adult↗
PubMed2000

Glomus faciale, glomus jugulare, glomus tympanicum, glomus vagale, carotid body tumors, and simulating lesions. Role of MR imaging.

In summary, MR imaging characteristics of a case of paraganglioma of the facial nerve are reported. The relationship of paragangliomas and the chromaffin system have been discussed. There are many reports of cases of synchronous paragangliomas and pheochromocytomas. These reports, along with simultaneous involvement in familial MEN syndromes, and the common embrylogic origin (neural crest) and similar histopathologic relationships between paragangliomas and pheochromocytoma, all support the fact that they are part of the chromaffin system.

Adrenal Gland Neoplasms↗
PubMed2000

Effect of interference of metallic objects on interpretation of T1-weighted magnetic resonance images in the maxillofacial region.

PURPOSE: Metallic objects produce artifacts on magnetic resonance (MR) images. However, studies on typical dental materials in this area are scant. This study was conducted to describe and measure the magnitude of such artifacts. MATERIALS AND METHODS: Samples of various dental materials (dental gold, amalgam, stainless steel, titanium, silver-palladium, and vitallium) were embedded in bovine muscle and then subjected to T1-weighted MR imaging. The materials were of the typical morphology and composition encountered in routine maxillofacial practice. The MR artifacts were measured and compared with the original specimen measurements. RESULTS: All metallic objects were found to produce artifacts and to interfere with the interpretation of MR images. Artifacts were most pronounced in the central plane of the object. Gold produced the greatest artifact, and amalgam produced the least. CONCLUSION: Because metals commonly used in the maxillofacial region all produce artifacts on MR images, avoidance measures should be used to minimize the effect of these artifacts.

Animals↗
PubMed2000

Magnetic resonance imaging of the normal temporal bone.

Recent advances in magnetic resonance imaging (MRI) technology has allowed the development of imaging sequences tailored to the assessment of exquisite anatomic detail of the temporal bone structures. This article describes MRI of the normal temporal bone anatomy, with emphasis on common anatomic variants and clinically relevant structures.

Ear, Inner↗
PubMed2000

Congenital sensorineural hearing loss and enlarged endolymphatic sac and duct: role of magnetic resonance imaging and computed tomography.

During the past 20 years, there have been significant advances in cochlear implants as the treatment of choice for profoundly hearing-impaired children. The increasing application of cochlear implant has brought with it an increase in the investigational use of computed tomography and magnetic resonance imaging. In this article, the author reviews (a) the anatomy and embryology of the inner ear, (b) the pathological changes associated with congenital sensorineural hearing loss (SNHL), and (c) the spectrum of imaging findings in patients with SNHL.

Child↗
PubMed2000

Magnetic resonance imaging for evaluation of otic labyrinth pathology.

The auditory (cochlear) labyrinth, the cochlea, holds the hearing sensory receptors. The vestibular labyrinth contains the sensory receptors for balance, which lie in the three semicircular canals and in the otolithic organs (the saccule and utricle). Pure tone audiometry and brain stem evoked audiometry can help to differentiate a peripheral cochlear disorder from central lesion. The type of nystagmus, severity of postural instability, and neurological evaluation can help to differentiate a peripheral vestibular disorder from a central vestibular lesion. The decision whether to perform an appropriate imaging such as brain imaging versus labyrinthine imaging depends on the clinical and paraclinical information provided to the radiologist by the neurotologist, neurologist, or other clinicians. The magnetic resonance imaging characteristics of peripheral cochlear and vestibular lesions are the main focus of this article.

Cochlear Diseases↗
PubMed2000

Value of imaging in disorders of the facial nerve.

Imaging of the facial nerve has proved its usefulness to physicians in the evaluation of pathological conditions of this nerve. Magnetic resonance imaging (MRI) of the facial nerve should always be obtained selectively and should include the parotid gland in case of peripheral facial nerve palsy. Gadolinium-DTPA contrast pulse sequence is the most informative MRI study for evaluation of facial nerve pathology. This article reviews the imaging anatomy of the facial nerve and describes the clinical features and MR characteristics of common disorders of the facial nerve.

Contrast Media↗
PubMed2000

Otogenic intracranial inflammations: role of magnetic resonance imaging.

The clinical course of acute otitis media is usually short, and the process terminates because of the host's immune system, the infection-resistant properties of the mucosal linings, and the susceptibility of the major organisms (beta-hemolytic streptococcus or pneumococcus) to penicillin. However, a small proportion (1% to 5%) of untreated or inadequately treated patients may experience complications. Prior to the development of an intracranial complication of otomastoiditis, warning symptoms or signs may be evident; these include severe earache, severe headache, vertigo, chills and fever, and meningeal symptoms and signs. Increasing headache, particularly temporoparietal headache near the affected ear, often indicates an impending intracranial complication. This symptom, often the only indication of an epidural abscess, demands prompt investigation and medical and surgical intervention. In our experience, computed tomography (CT) permits accurate diagnosis of acute coalescent or latent (masked) mastoiditis and its associated complications. However, magnetic resonance imaging (MRI) remains the study of choice to evaluate otogenic intracranial complications. This article demonstrates the important role of MRI in diagnosing various stages of acute otomastoiditis and its associated complications.

Brain Diseases↗
PubMed2000

Role of magnetic resonance imaging and diagnostic and interventional angiography in vascular and neoplastic diseases of the skull base associated with vestibulocochlear symptoms.

There are many vascular and neoplastic diseases as well as normal variants that produce the vestibulocochlear symptoms of pulsatile tinnitus, hearing loss, dizziness, and ataxia. Magnetic resonance imaging may be diagnostic, and magnetic resonance angiography/magnetic resonance venography have added to the ability of magnetic resonance to image vascular abnormalities. The extent of neoplasms is accurately assessed and complication of vascular lesions are clearly seen. However, detailed vascular anatomy requires high-quality selective angiography. This enables optimal treatment planning. Endovascular therapeutic intervention has a major role to play in conjunction with surgery of skull base lesions and may be curative in certain conditions, avoiding major surgical procedures. The interventionalist, however, must have an excellent knowledge of the external carotid circulation and all of its potential communications with the internal circulation to avoid serious embolic complications.

Angiography↗
PubMed2000

Pneumosinus dilatans of the sphenoid sinus presenting with visual loss.

OBJECTIVE: To report 3 cases of pneumosinus dilatans of the sphenoid sinus associated with visual loss. MATERIALS AND METHODS: Retrospective case series describing history of visual loss, visual examination, visual field deficits, and radiologic imaging. RESULTS: Three patients developed visual loss associated with pneumosinus dilatans of the sphenoid sinus. CONCLUSIONS: Pneumosinus dilatans of the sphenoid sinus is a rare disorder that should be considered in patients presenting with unexplained visual loss.

Adult↗
PubMed1999

Bilateral orbital emphysema from compressed air injury.

PURPOSE: To describe a patient who developed bilateral subconjunctival and orbital emphysema after an automobile tire explosion. METHOD: Case report. RESULTS: A 60-year-old man sustained bilateral ocular injury after a tire explosion. Ophthalmic examination disclosed bilateral subconjunctival air, with no visible conjunctival laceration. Computed tomography showed orbital emphysema, with no evidence of orbital fracture. Follow-up examination 2 weeks after the injury disclosed resolution of the subconjunctival air. Best-corrected visual acuity in the right eye was decreased after the explosion but improved to the baseline level of 20/40 2 weeks after the injury. CONCLUSION: Subconjunctival and orbital emphysema can occur from high-pressure air injury in the absence of an obvious entry site.

Air↗
PubMed1999

Optic nerve sheath meningiomas. Role of MR imaging.

Optic nerve meningiomas usually are seen in middle-aged and elderly women, and present as a slowly progressing axial proptosis and loss of vision. CT and MR imaging are the most valuable diagnostic tools to evaluate these tumors. This article reviews the MR imaging and CT characteristics of optic nerve sheath meningiomas and discusses features that may distinguish optic nerve sheath meningiomas from simulating lesions.

Aged↗
PubMed1999

Sarcoidosis of the eye, orbit, and central nervous system. Role of MR imaging.

Sarcoidosis, a systemic disease of unknown cause, frequently involves the eye, orbit, and central nervous system. The MR imaging findings of orbital and optic pathway sarcoidosis may closely resemble several other orbital and intracranial diseases. This article reviews MR imaging findings of sarcoidosis when it involves the eye, orbit, and visual pathways. Careful review of MR findings and other neuroimaging findings and clinical characteristics will reduce the incidence of mistaking optic nerve and chiasmal sarcoidosis for meningioma or glioma.

Adolescent↗
PubMed1999

Peripheral nerve tumors of the orbit.

Neurofibromas and schwannomas are orbital neoplasms with similar clinical and radiologic features. Solitary or circumscribed neurofibromas and schwannomas demonstrate slow progressive growth with ocular displacement and are amenable to surgical resection. Plexiform and diffuse neurofibromas are diffusely infiltrative in the orbit and periocular region, they are difficult to resect, and they have a high rate of recurrence. Malignant peripheral nerve tumors are rare, but they have a very high rate of recurrence and a low 5-year survival rate because of extension through the superior orbital fissure to the midbrain region. This article describes the clinical and radiologic features of peripheral nerve sheath tumors.

Disease Progression↗
PubMed1999

Lacrimal gland tumors and simulating lesions. Clinicopathologic and MR imaging features.

The lacrimal gland region can be involved in a wide spectrum of orbital pathology, including inflammatory, lymphoproliferative, and epithelial tumors. This article focuses on benign and malignant epithelial tumors of lacrimal gland and simulating lesions. The clinical presentations, MR imaging, and pathologic findings of lacrimal gland tumors are reviewed.

Dacryocystitis↗
PubMed1999

Magnetic resonance imaging in ocular pathology.

MRI has become a major diagnostic tool in ophthalmology for evaluation of ocular pathology. There is excellent delineation of anatomy of the ocular globe with MRI, and specific characteristics of derangement of anatomy by pathological processes are well delineated by MRI. Optimum MRI technique for evaluation of ocular pathology were discussed. Various entities of the ocular globe where MRI is useful in the detection and estimation of the extent of the pathological process and their specific MRI characteristics were discussed, including retinoblastoma, ROP, PHPV, uveal melanoma, choroidal hemangioma, and simulating lesions.

Eye Diseases↗
PubMed1998

Uveal melanoma, choroidal hemangioma, and simulating lesions. Role of MR imaging.

Malignant uveal melanomas are the most common primary intraocular malignant tumors in adults. Choroidal hemangiomas are congenital, benign, vascular lesions that may be confused with malignant uveal melanomas on clinical examination. The MR imaging characteristics of uveal melanomas and choroidal hemangiomas are different, making diagnostic differentiation possible with a high degree of accuracy. This article describes the MR imaging features of uveal melanoma, choroidal hemangioma, and other simulating lesions.

Adult↗