Perspectives on Neuroradiology Medical Expert Testimony: Fact and Fiction

There are numerous misconceptions about serving as a medical malpractice expert witness. By maintaining an objective perspective based in the unbiased interpretation of the images provided (for both sides of the conflict), one can best serve society as a whole. Most cases for which a neuroradiology expert is recruited are the following: 1) not with the radiologist as a defendant, 2) resolved without court testimony, and 3) short-lived if frivolous. One can learn much about medicine, our nonradiology colleagues, and the litigation process by participating as an expert witness.

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.

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.

Intralabyrinthine schwannomas

OBJECTIVE

To describe characteristic features of intralabyrinthine schwannomas (ISs) that may be used to distinguish them from other otologic disorders with similar symptoms so that appropriate evaluation and management can be instituted.

STUDY DESIGN

This study was a retrospective case review.

SETTING

This study was conducted at a university-affiliated urban tertiary care medical center and a university medical center in the same city.

PATIENTS

Seven patients with ISs were included in this study.

INTERVENTIONS

Tumor removal versus observation and monitoring with periodic magnetic resonance imaging (MRI) scans was investigated.

MAIN OUTCOME MEASURES

Hearing, vertigo, and tumor growth were measured.

RESULTS

Four of seven patients with ISs underwent surgical excision with no evidence of tumor recurrence. The remaining three patients are being followed-up with repeat MRI that has demonstrated minimal or no tumor growth.

CONCLUSIONS

ISs can be detected in early stages if MRI is performed in patients with unilateral sensorineural hearing loss without vertiginous symptoms typical of Meniere's disease. Although complete surgical excision can be achieved readily with labyrinthectomy, observation and monitoring with rep--MRI is an option for some patients.

MRI in vitamin B12 deficiency myelopathy

BACKGROUND

Little is known about vitamin B12 deficiency myelopathy's magnetic resonance imaging (MRI) manifestations and their relationship to the onset, evolution, and resolution of neurologic signs and symptoms.

METHODS

We present a case and review eleven additional reported cases of subacute combined degeneration of the spinal cord detected by MRI.

RESULTS

Our patient had increased T2-weighted signal and gadolinium contrast enhancement of the posterior columns in the cervical and thoracic regions and enhancement of the lateral columns in the high cervical region. This is a case with imaging evidence for lateral column lesions. Two prior reports have shown posterior column enhancement. T1-weighted images may show decreased signal in the posterior columns and sometimes demonstrate reversible spinal cord swelling. MRI abnormalities typically improve after vitamin replacement therapy. However, clinical signs may persist despite resolution of imaging abnormalities, and these abnormalities do not always resolve completely. In addition, symptoms may precede the imaging abnormality.

CONCLUSIONS

Vitamin B12 deficiency may produce an increased T2-weighted signal, decreased T1-weighted signal, and contrast enhancement of the posterior and lateral columns of the spinal cord, mainly of the cervical and upper thoracic segments. Because the symptoms may precede any imaging abnormality, it is clear that spinal cord MRI may not be a highly sensitive, early test for subacute combined degeneration.

Sclerotic lesions of the cervical spine in sarcoidosis

Sarcoidosis is a common multisystem disorder characterized by noncaseating epithelial granulomata, with osseous involvement typically seen in 5% of patients. While the lace-like or cystic pattern frequently seen in radiographs of the phalanges is well appreciated, sclerotic lesions of the spine are uncommon. We review a case of sarcoidosis of the cervical spine with sclerotic changes that mimicked blastic metastatic disease.

Sudden hearing loss: frequency of abnormal findings on contrast-enhanced MR studies

BACKGROUND AND PURPOSE

Our purpose was to determine the frequency of abnormal findings on contrast-enhanced high-resolution MR imaging studies in patients with sudden hearing loss.

METHODS

Seventy-eight consecutive patients with sudden hearing loss underwent contrast-enhanced MR imaging of the temporal bone, cerebellopontine angle, and brain. Additional tests included audiologic examination, electrocochleography, fistula tests, and serologic tests for viral agents and autoimmune disorders.

RESULTS

Probable causes of the sudden hearing loss in these patients included viral or immune-mediated disease, Meniere disease, vascular disorder, syphilis, neoplasm, multiple sclerosis, and perilymphatic fistula. Twenty-four (31%) of the 78 patients were found to have abnormal imaging results early in the course of their work up and treatment.

CONCLUSION

The prevalence of abnormal findings on contrast-enhanced MR studies is higher than previously reported in patients with sudden hearing loss.

Oculomotor motion disorders: current imaging of cranial nerves 3, 4, and 6

The eye movements are controlled by the cranial nerves 3, 4, and 6 working in close cooperation under the supervision of the voluntary cortex. Clinically, the most common presentation of abnormal ocular motor motion is double vision. A thorough clinical examination can usually separate a local orbital cause which can produce a restriction of the muscles moving the eye from a neurogenic cause due to an abnormality of one of the three nerves or their association pathways. Recent articles in the scientific literature have described major advances in our understanding of the anatomy and vascular relationships of the three ocular motor nerves (cranial nerves 3, 4, and 6) and of the diagnosis and treatment of a variety of pathological processes that damage these nerves, including ischemia, inflammation, and compression.

Solitary cerebellar metastasis from papillary thyroid carcinoma: a case report

Papillary thyroid carcinoma is a common thyroid malignancy that generally has a good prognosis. However, this type of cancer may give rise to distant metastasis and may behave more aggressively in older patients. Here we report clinical, radiological, and pathological findings of a patient with papillary thyroid carcinoma who had a solitary cerebellar metastasis. The patient was known to have metastatic thyroid cancer to the lungs, but this had been stable and the cerebellar metastasis presented an unanticipated significant problem. The rapid detection of cerebellar metastatic disease is critical because neurosurgical removal of the solitary lesion should be considered as the treatment of choice. This case also serves to remind us of the importance of considering possible metastatic brain lesions and their acute life-threatening complications in contrast to the relatively prolonged course associated with metastases of thyroid carcinoma to other organs.

Cervical spinal cord injury during cerebral angiography with MRI confirmation: case report

We report the first case of MRI-documented cervical spinal cord injury during cerebral angiography. A 54-year-old woman underwent an angiogram for subarachnoid hemorrhage. Her head was secured in a plastic head-holder. At the end of the procedure, she was found to have a left hemiparesis. MRI revealed high signal in the cervical spinal cord. The etiology may have been mechanical due to patient positioning, or toxic, from contrast medium injection in the vessels feeding the spinal cord, or a combination of both.

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.

Zoster myelitis: improvement with antiviral therapy in two cases

This report describes two patients with acquired immunodeficiency syndrome (AIDS) and herpes zoster myelopathy. Patient one had a T-8 myelitis that preceded the onset of T-8-distribution zoster and was followed by cervical myelopathy. Antibody to varicella zoster virus (VZV) was present in the CSF. He never received steroids or other immunosuppressive drugs, and his condition improved dramatically after treatment with intravenous acyclovir. The second patient had a rapidly progressive myelitis with paralysis of both legs. Detection of VZV DNA and antibody to VZV in his CSF led to successful treatment with famciclovir despite discontinuation of dexamethasone and earlier treatment failure with acyclovir. These cases support the idea that VZV myelopathy in the immunosuppressed host is caused by virus invasion. CSF analysis for antiviral antibody and for VZV DNA by polymerase chain reaction are helpful in establishing the diagnosis. Aggressive antiviral therapy is advised.

Endolymphatic duct/sac enhancement on gadolinium magnetic resonance imaging of the inner ear: preliminary observations and case reports

Twelve patients with auditory and/or vestibular symptoms were examined with a gadolinium magnetic resonance imaging (Gd-MRI) study. They all were found to have enhancement of only the endolymphatic duct/sac structures of the inner ear. Most of these findings were unilateral, but a few were bilateral. The patients underwent auditory, vestibular, and blood tests in an attempt to clarify the reason for this abnormal enhancement. Several specific etiologies were identified, but several cases had unknown causes. In this article we review the concept of inflammation of the inner ear structures with particular attention to the role of the endolymphatic duct/sac in the immune response of the inner ear. The idea of an inflammatory response of the inner ear leading to endolymphatic hydrops (Meniere's disease) is discussed, but these patients did not follow a clear path from inflammation of the endolymphatic duct/sac to endolymphatic hydrops. However, the longest follow-up was only 4 years, and our observations remain preliminary. Finally, the authors have found that Gd-MRI study of the inner ear provides valuable information in the investigation of patients with new auditory and/or vestibular symptoms.

Vestibular dysfunction in chronic inflammatory demyelinating polyneuropathy

Chronic inflammatory demyelinating polyneuropathy (CIDP) has occasionally been associated with clinical or laboratory evidence (magnetic resonance imaging,[MRI], visual evoked response, and brainstem auditory evoked response [BAER] of cranial neuropathy. In most cases, the relationship of cranial nerve involvement to CIDP remains unclear. A 45-year-old woman noted foot numbness, limb weakness, gait and postural instability, and oscillopsia. An IgG kappa monoclonal gammopathy of undetermined significance was found. Bilateral vestibulopathy was documented by clinical examination, bithermal calorics, rotary chair testing, BAERs, and dynamic posturography. MRI with gadolinium demonstrated enhancement of cranial nerve VIII bilaterally. Over the next 6 years, the patients's relapsing and remitting course of CIDP and vestibulopathy was assessed by quantitative muscle and vestibular function testing (clinically and neurophysiologically), and dynamic visual acuity. There was a striking synchronization between her CIDP and vestibulopathy with respect to clinical course including relapses and responses to immune therapy. The response to therapy, and evidence derived from clinical and laboratory investigations, suggest that the vestibular dysfunction was immune mediated.

Unilateral optic neuritis caused by Histoplasma capsulatum in a patient with the acquired immunodeficiency syndrome

PURPOSE

To evaluate the potential of Histoplasma capsulatum to cause optic neuritis in the setting of the acquired immunodeficiency syndrome (AIDS).

METHODS

We examined a 35-year-old man with a history of AIDS and disseminated histoplasmosis who developed a unilateral progressive optic neuritis of enigmatic origin. An optic nerve sheath biopsy was performed to provide a tissue diagnosis.

RESULTS

Histoplasma capsulatum was identified in both the optic nerve sheath and fungal culture.

CONCLUSION

Histoplasma capsulatum should be considered in the differential diagnosis of optic neuritis in patients with AIDS, even in the absence of chorioretinal findings.

MR of oculomotor nerve palsy

PURPOSE

To assess the utility of MR in third cranial nerve palsy.

METHODS

We reviewed precontrast and postcontrast MR of 50 patients with third cranial nerve palsy.

RESULTS

MR demonstrated an appropriate lesion in 32 cases. Of these patients, 6 had brain stem lesions and 15 had involvement of the nerve in the cavernous sinus; lesions of the cisternal segment of the nerve were present in 11 patients, with enhancement of this segment observed in 9 patients. An inflammatory or infiltrative source of the palsy was indicated in 19 of these 32 cases. Of 7 patients with pupillary involvement suggestive clinically of a compressive lesion, 4 demonstrated thickening and enhancement consistent with an infiltrative lesion of the nerve. Eighteen patients with pupil-sparing third cranial nerve palsies and a history of diabetes or vascular disease had normal MR findings, with no enhancement of the third cranial nerve observed.

CONCLUSIONS

Patients who do not have a history of diabetes or hypertension and in whom a complete or incomplete third cranial nerve palsy develops with or without pupil sparing should undergo MR imaging initially (unless there are clear symptoms or signs of subarachnoid hemorrhage) to exclude the presence of an infiltrative lesion or intraparenchymal process. Patients who have a history of vascular disease and a clinical presentation that is suggestive of an ischemic event may be observed initially, but should undergo imaging if improvement does not occur within 3 months.

MRI of the inner ear

The recent advances in MRI of the temporal bone brought about by the availability of intravenous contrast agents sensitive to the disruption of blood-brain barrier have further expanded the role of MRI in the evaluation of patients with vestibulocochlear symptoms. Not only can MRI be used to diagnose vestibular schwannomas (and other intracanalicular and cerebellopontine angle lesions mimicking it) with a high degree of accuracy, but it can now identify a variety of inflammatory and neoplastic processes of the membranous labyrinth which, in the past, were only made presumptively and occasionally confirmed by surgery and pathology. This enhanced diagnostic capacity of diseases of the vestibular cochlear system may help in the future to improve the management of these patients.

[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.

Contrast-enhanced magnetic resonance imaging of the temporal bone

The recent advances in MR imaging of the temporal bone brought about by the availability of intravenous contrast agents sensitive to the disruption of the blood-brain barrier have further expanded the role of MR imaging in the evaluation of this region. The main applications of contrast-enhanced MR imaging in the temporal bone are the evaluation of inflammatory and neoplastic processes of the labyrinth (in the general context of patients with sensorineural hearing loss or vertigo) peripheral seventh nerve palsies, and miscellaneous inflammatory and neoplastic conditions of the temporal bone itself.

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.

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.

Focal hyperdense areas in endometriomas: a characteristic finding on CT

OBJECTIVE

To assess the value of a hyperdense focus seen on CT scans of endometrial cysts in the differential diagnosis of a lesion.

MATERIALS AND METHODS

The preoperative CT scans of 328 patients with 410 ovarian masses (54 patients with 62 pathologically proved endometriomas and 274 patients with 348 pathologically proved other ovarian masses) were retrospectively reviewed in a random fashion without knowledge of the pathologic findings to determine whether a hyperdense focus was visible inside a cyst.

RESULTS

In nine of 62 endometrial cysts (sensitivity, 15%), CT scans showed a hyperdense round or crescent-shaped focus, measuring 2 to 15 mm. This focus was located close to the inner border of the cyst in eight cases and in the central part of the cyst in one case. A hyperdense focus was not seen on CT scans of 348 other ovarian masses (specificity, 100%). An in vitro CT study of two specimens showed that this hyperdense area corresponded to a blood clot next to the inner wall of the cyst. This hyperdense area appeared as a nonspecific hyperechogenic focus on sonograms in five of nine cases and as a hypointense signal on T1- and/or T2-weighted MR images in four of five cases.

CONCLUSION

The finding on CT scans of a hyperdense focus inside an ovarian cyst is suggestive of endometrioma and should help distinguish endometrioma from other pelvic masses.

Neurosyphilis in HIV carriers: MR findings in six patients

Neurosyphilis, a sexually transmitted disease that can cause neurologic damage, has become increasingly prevalent in the AIDS era. HIV carriers can contract neurosyphilis without the presence of other concurrent opportunistic infections. Because MR findings of neurosyphilis are seldom reported, we retrospectively reviewed and evaluated contrast-enhanced MR images of six young (average age, 33 years) HIV-positive men with high serum and CSF VDRL titers indicative of neurosyphilis. All six patients tested negative for concurrent opportunistic infections. Five patients had acute or subacute strokelike symptoms involving the basal ganglia or middle cerebral arteries; one had a parietal convexity mass mimicking meningioma with headache and ataxia. Contrast-enhanced MR images showed patchy enhancement involving the basal ganglia and middle cerebral artery territories in the first five patients and the convexity mass in the sixth patient. On the basis of brain biopsy, a convexity mass was diagnosed in the patient with syphilitic gumma. The imaging findings of the remaining five patients represented ischemic infarct caused by meningovascular syphilis. After penicillin treatment, serum and CSF VDRL titers decreased, and neurologic signs and symptoms improved in all six patients. A follow-up MR study in the patient with the gumma showed that the lesion resolved almost completely. In young HIV patients with stroke symptoms or a convexity mass, neurosyphilis should be considered. Contrast-enhanced MR can reveal the extent of involvement by neurosyphilis and should be used to facilitate diagnosis and proper treatment.

Labyrinthine enhancement on gadolinium-enhanced magnetic resonance imaging in sudden deafness and vertigo: correlation with audiologic and electronystagmographic studies

Sudden deafness with or without vertigo presents a difficult diagnostic problem. This article describes 12 patients with enhancement of the cochlea and/or vestibule on gadolinium-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (MRI), correlating the enhancement with the auditory and vestibular function. All patients were studied with T2-weighted axial images taken through the whole brain, enhanced 3-mm axial T1-weighted images taken through the temporal bone, and enhanced T1-weighted sagittal images taken through the whole brain. Cochlear enhancement on the side of hearing loss was found in all the patients. The vestibular enhancement correlated with both subjective vestibular symptoms and objective measures of vestibular function on electronystagmography. In 2 patients, the resolution of symptoms 4 to 6 months later correlated with resolution of the enhancement on MRI. No labyrinthine enhancement was seen in a series of 30 control patients studied with the same MRI 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 only indicate a sensorineural problem, enhanced MRI may separate patients with retrocochlear lesions, such as acoustic neuromas, from those in whom the abnormal process is in the labyrinth or the brain.

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.

Traumatic lesions of the suprasellar region: MR imaging

The authors studied nine patients with injuries to the suprasellar region with 1.5-T magnetic resonance (MR) imaging. Five patients had chiasmal injuries diagnosed by means of clinical examination. MR imaging demonstrated complete transection in two of these five patients, contusion of the chiasm by inferior herniation of the gyrus rectus in one, and a normal chiasm in two. Two patients had large tears of the floor of the third ventricle resulting in wide communication between the third ventricle and the prepontine cistern. One of these patients also had an avulsed third nerve. Transection of the pituitary stalk was seen in two patients. MR imaging can demonstrate injuries to the suprasellar structures. The MR imaging appearance of optic chiasm correlates with different types of injury to the chiasm described in the clinical literature and may alleviate the need for additional diagnostic studies to help explain the patient's symptoms.

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.

Deafness after bilateral midbrain contusion: a correlation of magnetic resonance imaging with auditory brain stem evoked responses

A 46-year-old woman became deaf after a closed head injury. When a computed tomographic scan failed to disclose the cause, conversion disorder was suspected. Magnetic resonance imaging, however, showed bilateral contusions of the inferior colliculi, providing objective evidence for an organic cause of hearing loss. Auditory brain stem evoked responses and stapedial reflexes also provided objective evidence of brain stem injury. This case illustrates the phenomenon of dorsal midbrain injury after head trauma. It indicates the sensitivity of magnetic resonance imaging for small focal lesions after head trauma, and it demonstrates some difficulties in the diagnosis of "hysterical" deafness.

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.

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.

Abnormal magnetic-resonance scans of the cervical spine in asymptomatic subjects. A prospective investigation

Previous investigations with plain radiography, myelography, and computed tomography have shown that degenerative disease of the cervical spine frequently occurs in the absence of clinical symptoms. We studied the magnetic resonance-imaging scans of sixty-three volunteers who had no history of symptoms indicative of cervical disease. The scans were mixed randomly with thirty-seven scans of patients who had a symptomatic lesion of the cervical spine, and all of the scans were interpreted independently by three neuroradiologists. The scans were interpreted as demonstrating an abnormality in 19 per cent of the asymptomatic subjects: 14 per cent of those who were less than forty years old and 28 per cent of those who were older than forty. Of the subjects who were less than forty, 10 per cent had a herniated nucleus pulposus and 4 per cent had foraminal stenosis. Of the subjects who were older than forty, 5 per cent had a herniated nucleus pulposus; 3 per cent, bulging of the disc; and 20 per cent, foraminal stenosis. Narrowing of a disc space, degeneration of a disc, spurs, or compression of the cord were also recorded. The disc was degenerated or narrowed at one level or more in 25 per cent of the subjects who were less than forty years old and in almost 60 per cent of those who were older than forty. The prevalence of abnormal magnetic-resonance images of the cervical spine as related to age in asymptomatic individuals emphasizes the dangers of predicating operative decisions on diagnostic tests without precisely matching those findings with clinical signs and symptoms.

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.

Progressive multifocal leukoencephalopathy in patients with AIDS: appearance on MR images

Progressive multifocal leukoencephalopathy (PML) is an uncommon demyelinating disease that occurs in immunocompromised patients. The authors evaluated magnetic resonance (MR) images of 10 patients with pathologically proved PML and clinically diagnosed acquired immunodeficiency syndrome (AIDS) to determine the MR characteristics of this disorder. All patients had asymmetric cerebral involvement. Lesions were distributed throughout the brain, including the brain stem and basal ganglia. White matter was affected in all 10 patients; gray matter was also involved in five. In one patient the lesion enlarged and crossed the corpus callosum and contained focal hemorrhage. The authors conclude that, contrary to reported findings on computed tomographic scans, PML in patients with AIDS has a variable appearance on MR images and has many characteristics that differ from those previously thought to be typical on imaging studies.

B-cell lymphoma marking only with anti-epithelial membrane antigen

A large cell malignancy identified as a B-lymphoma only by virtue of mu and kappa chain gene rearrangement additionally displayed profuse plasmalemma marking with anti-epithelial membrane antigen (EMA). Affinity absorption of the antibody with N-acetyl-galactosamine but not with N-acetylglucosamine or d-galactose effectively removed the lymphoma reactive antibodies. Soy bean agglutinin but not wheat germ agglutinin demonstrated lectin activity towards an epitope on the lymphoma membrane. Finally, digestion of cryostat sections of the lymphoma with N-acetylgalactosaminidase effectively removed the sugar epitope involved in EMA marking. Such data taken together would tend to indicate a membrane positioned complex carbohydrate with galactosamine dominancy. By analogy to the purported "late differentiation antigen secretory function" of EMA this lymphoma may be close to plasma cell stage.

Posterior fossa hemangioblastomas: MR imaging

The magnetic resonance (MR) imaging findings of 18 surgically proved posterior fossa hemangioblastomas (15 patients) were retrospectively analyzed and correlated with computed tomographic (ten patients) and angiographic (eight patients) findings. Thirteen tumors were located in the cerebellar hemisphere, three in the vermis, and two in the medulla with associated syrinxes. Three patients had von Hippel-Lindau disease, two of whom had multiple cerebellar hemangioblastomas. Seven hemangioblastomas appeared as solid tumors, six as solid masses with central cysts, and five as cysts with mural nodules. Abnormal tumor vessels, with characteristic signal void, were demonstrated in 13 tumors. Associated hemorrhage was present in four tumors. Although angiography is usually required for the diagnosis and preoperative assessment of this tumor, MR imaging demonstration of a posterior fossa mass with abnormal vessels should suggest the diagnosis of hemangioblastoma. Moreover, the combination of a peripheral posterior fossa cyst with a mural nodule supplied by enlarged vessels may be pathognomonic.

Aqueductal stenosis: evaluation with gradient-echo rapid MR imaging

To assess the utility of gradient echo (GRE) magnetic resonance (MR) imaging in documenting aqueductal patency, spin-echo (SE) and GRE axial images were obtained with a 1.5-T system in 26 patients with aqueductal or periaqueductal lesions and in 26 control subjects. All SE images with a long repetition time (TR) were obtained with first-order gradient moment nulling. GRE imaging was performed with the use of the sequential section acquisition technique called gradient recalled acquisition in the steady state (GRASS), with a TR of 150 msec, an echo time of 14-17 msec, and a flip angle of 50 degrees, so to depict stationary cerebrospinal fluid (CSF) as low intensity and flowing CSF as high intensity. All patent aqueducts were seen as high intensity on GRE images. In 18 of 20 obstructed aqueducts, low intensity was seen within the aqueducts on GRE images. SE images obtained with gradient moment nulling did not allow confident distinction between patent and obstructed aqueducts. It appears that GRE imaging is useful in rapidly assessing aqueductal patency.

Vascular intracranial lesions: applications of gradient-echo MR imaging

To investigate the role of the gradient-echo (GRE) technique in clinical intracranial magnetic resonance (MR) imaging, 63 patients with a variety of vascular intracranial lesions were examined at 1.5 T with the use of spin-echo (SE) and GRE sequences. In all cases, the sequential section acquisition technique called gradient recalled acquisition in the steady state (GRASS) was employed; a repetition time of 150-200 msec, an echo time of 13-16 msec, and a flip angle of 50 degrees-60 degrees were used to optimize the depiction of blood flow as high intensity and the depiction of stationary fluid as low intensity. In 61 of 63 cases, gradient moment nulling was utilized to compensate for first-order flow effects. Although GRE images rapidly demonstrated flow in vascular intracranial lesions as high intensity, the vascular nature of these lesions was also clearly evident on SE images in most cases. In some cases, GRE images can be used to clarify the vascular nature of a lesion or to characterize a neoplasm. Other applications include the detection of vascular thrombosis, occult vascular malformations, and hemorrhagic complications of vascular lesions.

Intracranial hemorrhage: gradient-echo MR imaging at 1.5 T. Comparison with spin-echo imaging and clinical applications

Fifty-seven patients with hemorrhagic intracranial lesions were examined with magnetic resonance (MR) imaging at 1.5 T with use of both spin-echo (SE) and gradient-echo-acquisition (GEA) techniques to assess the clinical applications and limitations of GEA in evaluation of intracranial hemorrhage at high field strength. All GEA images were obtained with a long echo time and short flip angle to emphasize T2*-based contrast. In 30 of 61 cases, GEA images demonstrated more hemorrhagic lesions than SE images. In 14 of 61 cases, GEA images failed to depict the lesion or obscured the specific diagnosis (as depicted by SE MR imaging). The authors believe that GEA imaging in its current form has a limited but definite adjunctive role in the evaluation of intracranial hemorrhage at high field strength.

MR evaluation of large intracranial aneurysms using cine low flip angle gradient-refocused imaging

MR imaging has proved to be useful in evaluating large intracranial aneurysms. The parent artery and patent lumen can be identified as flow voids and differentiated from thrombus. However, in the presence of slow flow, even-echo rephasing, and motion artifact, increased intraluminal signal may be present, which may be difficult to distinguish from thrombus. Aneurysms are also dynamic lesions and exert pulsatile mass effect on adjacent structures. Further definition of vascular anatomy and physiology may aid in therapeutic planning and assessment. Cine MR is a new technique using a movie loop of sequential GRASS (gradient-recalled acquisition in the steady state) images obtained during various points in the cardiac cycle. The combination of GRASS images and cardiac gating thus allows cinegraphic display of vascular structures. A comparison of this method with routine T1- and T2-weighted MR imaging and angiography was made in a group of 13 patients with intracranial aneurysms greater than 1.5 cm in diameter. Eight of these patients underwent transvascular detachable balloon occlusion. With cine MR, flowing blood has high intensity due to flow-related enhancement. Turbulent and high-velocity flow can be recognized on the basis of signal loss, which occurs during systole. Thrombus demonstrated variable signal intensity, which remained unchanged during the cardiac cycle. Compared with routine MR sequences, there was less image degradation from phase-encoding artifacts and improved visualization of the neck of the aneurysm. Pulsatile mass effect was uniquely assessed. After transvascular embolization, cine MR demonstrated improved conspicuity of acute thrombus and higher contrast between flowing blood and the occlusion balloon when compared with routine MR. Confirmation of flow within the parent vessel, residual aneurysm lumen, and distal arterial branches is possible. If the parent vessel was occluded, cine MR yielded greater information than angiography. Cine MR provides additional anatomic and physiologic data in the evaluation and assessment of therapy of intracranial aneurysms. Information can be obtained that is not available with either routine MR or angiography. The inherent limitations of this new technique include partial-volume artifacts, less than optimal flow-related enhancement or spatial resolution, and poor data acquisition due to cardiac arrhythmias.

Magnetic resonance imaging of the TMJ disc in asymptomatic volunteers

Forty-two temporomandibular joints (TMJs) in 21 asymptomatic volunteers were visualized by magnetic resonance imaging (MRI). The subjects, 12 males and nine females, were between 23 and 43 years of age and had no history of TMJ pain, joint noise, limited opening, or previous treatment for TMJ disorder. A cephalometric head-holder was designed to position the TMJ in an accurate and reproducible manner and multisection parasagittal images were obtained perpendicular to the longitudinal axis of the condyle. MR images depicted anterior disc position in 32% of the asymptomatic joints (8/24 males, 5/18 females). Anterior disc position in asymptomatic subjects may be a predisposing factor to TMJ dysfunction or simply an anatomic variant whose prevalence must be considered when evaluating TMJ dysfunction.