Biomedical subjects

A S Mark

Publications and source records attributed to A S Mark.

66 records · Page 4Linked to original sources

PubMedDate not supplied

Common errors in the use of magnetic resonance imaging for neuro-ophthalmic diagnosis.

The optimal utilization of magnetic resonance imaging in neuro-ophthalmic diagnosis is limited by errors in prescribing and interpreting scans. In a review of case material, we discovered four common prescriptive errors: 1) failure to apply a dedicated study, 2) inappropriate use of a dedicated study, 3) omission of intravenous contrast, and 4) omission of specialized sequences. The four common interpretive errors were the following: 1) failure to detect the lesion because of misleading clinical information, 2) rejection of a clinical diagnosis because an expected imaging abnormality was absent, 3) assumption that a striking imaging abnormality accounted for the clinical abnormality, and 4) failure to consider the lack of clinical specificity of imaging abnormalities. Many of these errors could be avoided by improved communication between clinicians and radiologists.

Artifacts↗

PubMedDate not supplied

CT of aortoenteric fistulas.

We compared CT findings with endoscopic, angiographic and surgical results in ten patients suspected of having an aortoenteric fistula (AEF) because of gastrointestinal bleeding (seven) or recurrent sepsis (three). CT correctly diagnosed AEF in six patients and excluded it in the other four. CT findings of AEF consisted of perigraft fluid (PGF) (5/6) and/or gas within the bed of the graft (4/6) later than three months after graft surgery. All six patients with AEF had perigraft infections; PGF with gas was found in 50%, PGF alone in 33%, and in one patient perigraft gas alone was found. Angiography and endoscopy failed to identify AEF. Our findings indicate that CT should be the initial imaging procedure in patients with suspected AEF who do not require immediate surgical intervention.

Angiography↗

PubMedDate not supplied

MR imaging of acute transverse myelitis and AIDS myelopathy.

Acute transverse myelitis (ATM) is a well recognized clinical entity, though its etiology remains obscure. Only a few reports of magnetic resonance imaging of ATM appear in the literature. These reports describe conflicting findings with respect to the signal intensity of the spinal cord on long repetition time (TR) sequences. The purpose of this study is to present our experience with five cases of ATM in which long TR sequences demonstrated abnormal increase in signal intensity of the cord. Magnetic resonance imaging also demonstrated extension of abnormal cord signal intensity over at least six spinal segments and above the clinically determined sensory level in four of five cases. Cord expansion was noted in two of five cases with normal myelograms. A case of acquired immunodeficiency syndrome (AIDS) myelopathy that demonstrated a similar high signal intensity of the cord is also presented. Our findings suggest that both ATM and AIDS myelopathy should be considered in the list of conditions that may result in a diffuse increase in the signal intensity of the cord on long TR sequences.

Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

Postoperative complications in otospongiosis: usefulness of MR imaging.

BACKGROUND AND PURPOSE: Sensorineural hearing loss (SNHL) is a rare complication of stapes surgery that may arise for many reasons. Usually, the pathogenesis of SNHL can be established by clinical and CT examinations. The purpose of this study was to evaluate the utility of MR imaging when CT findings are normal or not contributive. METHODS: Eleven patients with SNHL (in some instances, associated with vertigo) after stapedectomy, in whom CT showed no well-defined cause, were examined by MR imaging. RESULTS: MR studies established the additional findings of reparative intravestibular granuloma (n = 2), intralabyrinthine hemorrhage (n = 1), and bacterial labyrinthitis (n = 1). In five cases, MR findings were similar to CT findings. In two cases, CT and MR results were normal. Revision surgery was performed in five patients and confirmed the MR findings in each case. CONCLUSION: If CT is not contributive as to the origin of SNHL and vertigo occurring after stapes surgery, then MR imaging may be helpful in these patients.

Adult↗

PubMedDate not supplied

Gd-DTPA enhancement of the cisternal portion of the oculomotor nerve on MR imaging.

PURPOSE: To describe a radiographic finding--enhancement of the cisternal portion of the third cranial nerve on postcontrast MR--and to correlate it with patients' clinical symptoms and ultimate diagnosis. MATERIALS AND METHODS: Thirteen consecutive patients with enhancement of the cisternal portion of the third cranial nerve on postcontrast MR were retrospectively identified; 50 control patients referred for pituitary microadenomas were also retrospectively reviewed. FINDINGS: The enhancement was bilateral in six patients and unilateral in seven patients. Four of the six patients with bilateral enhancement had unilateral oculomotor nerve palsies; none had bilateral third cranial nerve palsy. Five of the seven patients with unilateral enhancement had ipsilateral third nerve palsies. Of the nine patients with third nerve palsies, the pupil was involved in four patients. Follow-up studies were available in six patients, four of whom had third nerve palsy. Resolution of the enhancement correlated with resolution of the symptoms in two patients. The patients' underlying diagnoses were lymphoma (four), leukemia (one), viral meningitis (one), neurofibromatosis (two), inflammatory polyneuropathy-HIV related (one), ophthalmoplegic migraine (one), Tolosa-Hunt syndrome (one), coccidioidomycosis (one), and diabetes (one). No enhancement was seen in any of the controls. CONCLUSION: Enhancement of the cisternal segment of the third cranial nerve is always abnormal, revealing an underlying inflammatory or neoplastic process. However, it is not always associated with clinically apparent oculomotor nerve dysfunction.

Adult↗

PubMedDate not supplied

Aortic anastomotic pseudoaneurysms: US, CT, MR, and angiography.

Correlation of imaging and anatomic findings in seven men with abdominal aortic graft prostheses (four "end-to-end" anastomoses and three "end-to-side" anastomoses) was done to compare the value of different imaging modalities in detecting postoperative complications, especially aortic anastomotic pseudoaneurysms (AAPs). In all cases, angiographic and CT studies were carried out. In six patients ultrasound and MR examinations were also performed. Anatomic verification was obtained by surgery in six patients and autopsy in one case. Five patients had an AAP (four at surgery and one at autopsy), one had a true abdominal aortic aneurysm above the anastomosis, and one a nondetectable abnormality of the aortic suture line. Digital subtraction angiography diagnosed one of five AAPs, missed the true aneurysm in the sixth patient, and was normal in the patient without any aneurysm. Computed tomography correctly diagnosed the five AAPs and the true aneurysm and was normal in the last patient. Ultrasound correctly diagnosed the AAPs in three of four patients, incorrectly diagnosed an AAP in the patient who had the true aneurysm, and was normal in the patient without any aneurysm. Magnetic resonance diagnosed four of four AAPs and the true aneurysm and was normal in the last patient. Computed tomography seems to be the best imaging modality with which to diagnose and evaluate an aortic AAP in patients with aortoiliofemoral graft prosthesis.

Aged↗

PubMedDate not supplied

CNS sarcoidosis: evaluation with contrast-enhanced MR imaging.

Reports of findings on unenhanced MR images and contrast-enhanced CT scans in patients with intracranial sarcoidosis have suggested that MR imaging without contrast enhancement may miss meningeal involvement, which is a frequent and prominent finding in neurosarcoidosis. We studied 14 patients with CNS sarcoidosis with T1- and T2-weighted pre- and postcontrast sequences and T1-weighted postcontrast sequences. Eight of 12 patients with intracranial sarcoidosis and one of two with spinal sarcoidosis had meningeal involvement that was not apparent on the unenhanced scans. Eight of 12 patients had intraaxial areas of high signal intensity on T2-weighted images, although only two of these lesions enhanced. Three patients had enhancing extraaxial masses mimicking meningiomas on postcontrast T1-weighted images. In two patients, the lesions decreased markedly in size after steroid treatment. In one patient with sarcoidosis of the optic nerve, the lesion decreased in size and the patient's vision returned to normal after Cytoxan therapy. In five of 14 patients, CNS findings were the initial clinical manifestation of the disease. In nine of 14 patients, the diagnosis of neurosarcoidosis was suggested only after administration of contrast agent. Use of gadopentetate dimeglumine greatly enhances the sensitivity of MR imaging in the detection of CNS sarcoidosis.

Adolescent↗

PubMedDate not supplied

Contrast enhancement of the labyrinth on MR scans in patients with sudden hearing loss and vertigo: evidence of labyrinthine disease.

The sudden onset of hearing loss and vertigo presents a difficult diagnostic problem. We describe the finding of labyrinthine enhancement on MR images in five patients with sudden unilateral hearing loss or vertigo or both and correlate the MR findings with audiologic and electronystagmographic studies. All patients were studied with T2-weighted axial images through the whole brain, contrast-enhanced 3-mm axial T1-weighted images through the temporal bone, and enhanced T1-weighted sagittal images through the whole brain. Cochlear enhancement, on the side of hearing loss only, was found in all five patients. The presence of associated vestibular enhancement correlates with objective measures of vestibular function on the electronystagmogram. In two patients, the resolution of symptoms 4-6 months later correlated with resolution of the enhancement on gadopentetate dimeglumine-enhanced MR images. Two patients had luetic labyrinthitis. No labyrinthine enhancement was seen in a series of 30 control subjects studied with gadopentetate dimeglumine-enhanced MR using the same protocol. Labyrinthine enhancement in patients with auditory and vestibular symptoms is a new finding and is indicative of labyrinthine disease. While abnormalities on electronystagmograms and audiograms are nonspecific and indicate only a sensorineural problem, gadopentetate dimeglumine-enhanced MR may separate patients with retrocochlear lesions, such as acoustic neuromas, from those in whom the abnormal process is in the labyrinth or is intraaxial. This group of patients underscores the importance of identifying and commenting on the structures of the membranous labyrinth when evaluating MR studies of the internal auditory canal and the cerebellopontine angle in individuals with hearing loss.

Adult↗

PubMedDate not supplied

[Identification of antinuclear, nucleolar and SS-A antibodies, using an immunoassay system].

In this paper we report a solid phase ELISA for screening of antinuclear, nucleolar, and SS-A antibodies. The test system was evaluated with 158 sera that were positive by immunofluorescence (IF), some of which were immunologically characterized as containing antibodies to Sm, RNP, SS-A, SS-B, nucleolar, and DNA, and 247 IF negative that were used as a control group. Ninety eight per cent of serum samples with an antibody of known specificity and/or positive IF, were positive by the ELISA system including antinucleolar samples. Reproducibility of the assay was demonstrated by using five sequentially prepared antigenic extracts. The lineal regression from the last experiment was between 0.75 and 0.91. With this system, positive and negative ANA can be identified as the screening procedure without the need of additional studies. To our knowledge this is the first ELISA system report for the screening of antinucleolar antibodies.

Antibodies, Antinuclear↗

PubMedDate not supplied

Segmental enhancement of the cochlea on contrast-enhanced MR: correlation with the frequency of hearing loss and possible sign of perilymphatic fistula and autoimmune labyrinthitis.

PURPOSE: To relate the finding of selective enhancement of different turns of the cochlea to the frequency range of the hearing loss measured by audiogram. METHODS: Six patients aged 23 to 53 years, four men and two women, who presented with sudden hearing loss and had segmental enhancement of different turns of the cochlea on contrast-enhanced MR imaging were included in this retrospective study. The patients were imaged on a 1.5 T MR imaging system using pre- and postcontrast axial T1-weighted images and postcontrast coronal T1-weighted images through the temporal bone. RESULTS: The basal turn of the cochlea enhanced selectively in five of the six patients and the apical turn enhanced in the sixth patient. All patients had sensorineural hearing loss. Three of the patients with basal turn enhancement had predominantly high-frequency hearing loss, whereas the patient with apical turn enhancement had predominantly low-frequency hearing loss. The two other patients with basal turn enhancement had complete hearing loss. Three patients had presumed autoimmune labyrinthitis. The other three patients had strong clinical and surgical evidence of a perilymphatic fistula. CONCLUSION: Contrast-enhanced MR imaging may demonstrate selective enhancement of different turns of the cochlea. In certain patients, the areas of enhancement may correlate with specific hearing loss in the frequencies mapped by the enhancing segment. Enhancement of the cochlea may represent radiologic evidence of cochlear inflammation secondary to a perilymphatic fistula.

Adult↗

PubMedDate not supplied

Sensorineural hearing loss: more than meets the eye?

PURPOSE: To assess the value of MR in patients with sensorineural hearing loss (SNHL) caused by lesions other than acoustic neuromas. METHODS: MR studies of 51 patients with SNHL were retrospectively reviewed; patients with acoustic neuroma were excluded to focus on the more uncommon causes. RESULTS: Twenty patients had labyrinthine lesions. Six patients had viral labyrinthitis, one patient had bacterial labyrinthitis, and one patient had luetic labyrinthitis. Three patients had hemorrhage in the labyrinth, two posttraumatic and one spontaneous from an adjacent temporal bone tumor. Only one of the two patients with traumatic labyrinthine hemorrhage had evidence of a fracture on high-resolution CT. In one patient with CT-proved cochlear otosclerosis, peri-cochlear foci of enhancement were seen on contrast-enhanced MR. Four patients had presumed labyrinthine schwannomas. A middle ear cholesteatoma in one patient invaded the cochlea and resulted in marked cochlear enhancement due to granulation tissue. Thirteen patients had intracanalicular and cerebellopontine angle lesions. The lesions included arteriovenous malformations (three patients), sarcoidosis (three patients), metastasis (two patients), lymphoma (two patients), lipomas (two patients), and postshunt meningeal fibrosis (one patient). Eighteen patients had intra-axial lesions responsible for SNHL. The most common intra-axial lesions were brain stem infarcts and multiple sclerosis. Traumatic lesions in the inferior colliculi, sarcoidosis, lymphoma, and extrinsic compression of the colliculi from a pineal tumor were also noted. CONCLUSION: MR can demonstrate numerous lesions responsible for SNHL other than acoustic neuromas. The entire acoustic pathways, including the labyrinth, internal auditory canal, cerebellopontine angle, and brain stem should be carefully scrutinized for lesions in patients with SNHL. The use of contrast media markedly increases the yield of MR in this clinical situation by demonstrating inflammatory and neoplastic labyrinthine lesions and meningeal pathology (both neoplastic and inflammatory) in the internal auditory canal and cerebellopontine angle cistern.

Adolescent↗

PubMedDate not supplied

Ophthalmoplegic migraine: reversible enhancement and thickening of the cisternal segment of the oculomotor nerve on contrast-enhanced MR images.

BACKGROUND AND PURPOSE: Ophthalmoplegic migraine is a rare condition characterized by the association of headaches and an oculomotor nerve palsy. We report six patients with typical clinical features of this disorder in whom enhancement of the cisternal segment of the oculomotor nerve developed during the acute phase, followed by resolution of enhancement over several weeks as the symptoms resolved. METHODS: Six patients, ages 3 to 27 years, underwent MR imaging during the acute phase of ophthalmoplegic migraine and at the time of recovery several weeks later. The MR studies, performed on a 1.5-T MR unit, included noncontrast and contrast-enhanced axial and coronal T1-weighted sequences. Sagittal images were obtained in two patients, with and without contrast enhancement. RESULTS: Enhancement of the cisternal segment of the oculomotor nerve was seen in all patients at initial presentation. Contrast-enhanced studies also showed focal thickening at the exit of the nerve in the interpeduncular cistern in five of six patients. No patient had enhancement of the cavernous sinus or adjacent dura. Enhancement was almost completely resolved on follow-up studies 7 to 9 weeks later. CONCLUSION: Our findings confirm an intrinsic transient abnormality in the cisternal segment of the third nerve in patients with a typical clinical presentation of ophthalmoplegic migraine.

Adolescent↗