Association of deep white matter infarction with chronic communicating hydrocephalus: implications regarding the possible origin of normal-pressure hydrocephalus.

The coexistence of cerebrovascular disease leading to deep white matter infarction and normal-pressure hydrocephalus has been noted previously in clinical studies, as both diseases can present with the triad of gait disturbance, dementia, and incontinence. The purpose of this MR study was to determine if the two diseases demonstrated a statistical association. Evidence of patchy periventricular hyperintensity representing presumed deep white matter infarction was sought in 20 patients shunted for normal-pressure hydrocephalus and in 35 additional consecutive patients with clinical symptoms and MR findings consistent with normal-pressure hydrocephalus. Deep white matter infarction was also sought in 62 consecutive age-matched control subjects. There was a statistically significant (p less than .001) higher association (58%) of marked infarction in the 55 patients with normal-pressure hydrocephalus than in the age-matched controls (24%). MR findings of communicating hydrocephalus (ventriculomegaly and increased aqueductal CSF flow void) were sought in 78 consecutive patients with presumed deep white matter infarction, and the degree of severity of the two diseases was also found to be statistically significant (p less than .05). In view of this association, the possibility that the two diseases are related was considered. A potential mechanism is discussed whereby deep white matter infarction leading to decreased periventricular tensile strength could result in communicating hydrocephalus. It is plausible that normal-pressure hydrocephalus may result from a number of different insults to the brain.

Magnetic resonance imaging of the larynx.

Rarely does any radiologic imaging modality play a significant role in reaching a diagnosis of malignancy in the larynx and hypopharynx. These regions are so readily accessible to clinical examination that the combination of cytology and visual inspection usually strongly indicates the diagnosis of cancer. Therefore, the primary role of MR is the same as that of CT in imaging the larynx and hypopharynx: to define the extent of the disease. Compared to CT, MR consistently shows superior soft tissue definition. The use of direct coronal and sagittal scan planes allows the visualization of intrinsic laryngeal musculature in addition to better defining cranial caudal tumor extension. Thus, MR is now the imaging study of choice for the evaluation of cancer of the larynx. The role of MR can also be extended to replace CT scanning in the evaluation of the laryngeal airway and benign lesions of the larynx.

Magnetic resonance imaging of the facial nerve.

Magnetic resonance imaging (MRI) of the facial nerve was evaluated by studying normal volunteers and patients with diseases of the facial nerve with a 0.3 Tesla permanent-magnet MRI system with special surface coils. The normal MR images were correlated with the anatomy of thin cryosection specimens of fresh cadavers. The seventh nerve was followed from its nucleus in the brainstem through the temporal bone to the parotid gland bed. The entire labyrinth and tympanic portions, as well as the geniculate ganglion, could be shown with appropriate scan planes. Examples of brainstem diseases affecting the facial nerve and nucleus, facial neuromas, parotid tumors involving the facial nerve, and other diseases were studied. MRI is a technique that allows unique evaluation of the entire course of the facial nerve. It produces superior images of the facial nerve with high-contrast resolution. Unlike computed tomography, there is no beam-hardening artifact from the temporal bone or exposure to ionizing radiation and contrast agents. MRI also allows visualization of the main trunks of the facial nerve in the parotid bed not possible with any other imaging technique.

Parotid masses: MR imaging.

Over a 2-year period 20 patients who presented with masses in the parotid gland were evaluated with magnetic resonance (MR) imaging. T1-weighted images were obtained on a high-resolution, thin-section MR imaging system. When "cystic-appearing" lesions were found, T2-weighted images were obtained in order to better characterize the tumor. As in other areas of the body, MR images of parotid tumors are not usually histologically specific. MR findings may be distinctive in rare cases and define the internal architecture of complex parotid masses. Although poor tumor margination was a clue to malignancy, this was not a consistent finding. The real advantage of MR imaging in evaluating parotid masses was its ability to accurately reveal the extraparotid or intraparotid location of a tumor and demonstrate the relationship of the tumor to the facial nerve. Small and medium-sized mass lesions could be seen as superficial or deep to the facial nerve. Larger masses producing some distortion of the normal course of the nerve made identification of the nerve more difficult, if not impossible. In malignant tumors with gross invasion of the facial canal, MR images can show the extent of nerve involvement.

MR imaging of the intraparotid facial nerve: normal anatomy and pathology.

Three normal volunteers, 58 normal patients, and three patients with parotid tumors were studied with a 0.3 T permanent-magnet imaging system to directly image the intraparotid facial nerve. On T1-weighted images the nerve appeared as a curvilinear structure of relatively low signal intensity within the fatty, high-signal parotid parenchyma. Its major divisions and branches could be imaged only with specially angled axial scan planes. To verify our observations MR imaging was compared with whole-organ cryomicrotome sections cut at the same angles. Normal variations in the appearance of the nerve and pitfalls in its visualization are discussed. Three cases of parotid tumors, with surgical confirmation of the relationship of the facial nerve to the tumor, are presented. MR is the only imaging technique capable of direct imaging of the facial nerve in the parotid bed: it may assist materially in the surgical management of tumors of the parotid gland.

The "notch" sign: meniscal contour deformities as indicators of tear in MR imaging of the knee.

Conventional magnetic resonance (MR) criteria for meniscal tearing emphasize intrameniscal signal and its communication with the articular surface. In this retrospective study, the value of a focal contour deformity of the meniscal articular surface, termed a "notch," as an additional MR sign of meniscal tearing was assessed. One hundred fifty-four menisci were evaluated. Twenty-three of 24 notches correlated with the site of tear at arthroscopy. Seven notches improved the reading confidence from possible to definite tear; in eight notches, the diagnosis of tear would otherwise not have been considered. Five tears occurred without intrameniscal signal, four following recent trauma. The notch sign improved the sensitivity from 79.8 to 87.8%. Notches are useful additional signs of meniscal tearing, increasing the confidence of a reading when occurring near grade 1 or 2 meniscal signal, and are the only MR sign present in some tears.

Production of maximally acid urine by the isolated dog kidney.

The isolated kidney has not been reported to acidify urine maximally. To study this defect, kidneys from dogs fed NH4Cl were perfused with autologous blood. Perfusate pH was 7.20 +/- 0.03 [HCO3] was 14 +/- 1 mEq/L, and urine pH was abnormally high, 6.60 +/- 0.08. When corrected for difference in GFR, UNH4+V was similar to that seen in vivo, but UTAV and UNet H+V were low. FEHCO3- was 2.3% +/- 0.8% and HCO3- excretion persisted to a small degree at perfusate [HCO3-] of 8 to 9 mEq/L. In response to HCO3- infusions, large increases in excretion were not seen until perfusate values were over 24 to 26 mEq/L. HCO3- Tmax was 2.94 +/- 0.07 mEq/dl of glomerular filtrate. The isolated kidney failed to raise U-B PCO2 with HCO3- infusion secondary to low urine [HCO3-] and [Pi]. During perfusion in another group of kidneys from dogs fed NH4Cl and given DOC, perfusate pH and [HCO3-] were similar to those in the first group. Urine pH was also inappropriately high, 7.12 +/- 0.09, and there was no UNet H+V. In response to Na2SO4 infusion, urinary pH fell to 5.00 +/- 0.27. Log10UUAV was correlated to urine pH during the control perfusions in both groups and after Na2SO4 in the NH4Cl + DOC group. Thus production of a low urine pH in the isolated kidney may be mediated by changes in transtubular potential difference resulting from increased distal nephron delivery of Na+ and nonabsorbable anion. The defect in acidification is similar to that observed in incomplete forms of clinical type 1 (distal) renal tubular acidosis.

Intravenous digital subtraction angiography of arteriosclerotic vertebrobasilar disease.

Intravenous digital subtraction angiography (DSA) was performed in 111 patients with vertebrobasilar ischemia. Ninety percent of the vertebral images were of diagnostic quality; 23% of the basilar images were good quality and 53% fair quality; and 58% of the posterior cerebral images were poor. Compared with selective film arteriography in 23 patients, DSA tended to underestimate the degree of atheromatous disease. Segments of the basilar artery were often poorly seen, which could result in false-negative errors. DSA can provide a general assessment of atheromatous disease of the brachiocephalic vessels, including the vertebral and carotid arteries, and in many cases can exclude occlusion or critical stenosis of the vertebrobasilar system. However, it does not adequately image the posterior cerebral or cerebellar artery.

MR imaging of experimental demyelination.

Seventeen rabbit sciatic nerves undergoing experimental demyelination and 17 control nerves were imaged in vivo with a 0.3-T MR imaging system using a silicone chamber wrapped around the nerves to isolate them from surrounding tissues. Three pulse sequences were used for each nerve: (1) spin-echo 500/28 (TR/TE), (2) spin-echo 2000/56, and (3) inversion recovery 1000/300/30 (TR/TI/TE). Image intensity data were acquired for each nerve by placing a region of interest over the nerve and measuring pixel brightness within the region of interest by means of a computer algorithm. The mean signal intensity of the experimental nerve was then compared with the mean signal intensity of the contralateral control nerve on the same image. Histologic sections of the nerves were stained with Loyez's stain for myelin and thionin for glial cells. MR findings were then compared with histopathologic data. Experimental nerves showed distinct stages of demyelination. Two fundamental observations were surmised from the data: (1) Perceptible MR signal changes are associated with early nerve degeneration, in which there is demyelination in the absence of glial cell proliferation; these changes are appreciated as increased intensity on heavily T2-weighted sequence. In these nerves no signal changes are seen on T1-weighted sequences. (2) Perceptible MR signal changes are associated with more advanced nerve degeneration, in which there is an increase in the number of glial cells in the absence of further demyelination; these changes are appreciated as decreased intensity on T1-weighted sequences and markedly increased intensity on T2-weighted sequences, respectively. The results show that MR can distinguish stages of demyelination in degenerating nerves, thereby providing a powerful method for the diagnosis and characterization of demyelinating disease.

Magnetic resonance imaging of bioabsorbale polylactic acid interference screws during the first 2 years after anterior cruciate ligament reconstruction.

Bioabsorbable screws composed of poly(L-lactic acid) (PLA) were used for graft fixation and studied prospectively with serial magnetic resonance imaging (MRI) scans at 8, 16, and 24 months after autogenous patellar tendon anterior cruciate ligament (ACL) reconstruction in 10 patients. Conventional spin echo, proton density, and T2-weighted double echo sequences were obtained, as well as T2-weighted fat-saturated fast spin echo sequences. All but one of the screws (19 of 20) were evident in all serial scans. These showed minimal decrease in size over time. The one screw that had completely disappeared 8 months after reconstruction had cracked during insertion. None of the reconstructed ACL grafts showed clinical instability, persistent effusions, or detectable adverse reactions to the screws. Two patients developed abnormal signal in the tibial tunnel: one developed fluid anterior to the graft, and the other developed increased signal within the graft. The abnormal signal resolved with time in both patients. Other than the preceding changes, no abnormalities were detected on conventional sequences. Fat-saturated fast spin echo sequences showed a variable amount of increased signal around the tunnels, suggesting edema or fibrovascular marrow changes. The changes noted near the tunnels on the fat-suppressed scans most probably represent a general reaction to surgical insult rather than a reaction to the bioabsorbable screws, as similar changes were noted at the patellar harvest site.

Effect of arm rotation on MR imaging of the rotator cuff.

The effect of humeral rotation on the appearance of the rotator cuff tendon in oblique coronal magnetic resonance images was evaluated in 70 such images. Internal rotation produced overlap of the supraspinatus and infraspinatus tendons with soft-tissue interposition or apparent discontinuity of the tendon in 22 cases, including 14 of 15 shoulders positioned in the first 30 degrees between extreme internal and external rotation. Imaging in internal rotation makes assessment of the tendon difficult and should be avoided.

Cervical spine hyperextension injuries: MR findings.

Cervical hyperextension injuries are common and often show minimal radiographic abnormalities, even with severe or unstable lesions. Fourteen patients, nine with acceleration hyperextension "whiplash" injuries and five injured by direct frontal head trauma, underwent magnetic resonance (MR) imaging within 4 months of injury. Five of seven patients with anterior spinal column injuries showed characteristic separation of the disk from the vertebral end plate, lesions still evident as late as 9 months after injury. The demonstration of this type of lesion and its delayed resolution may have prognostic and surgical implications. These lesions, anterior longitudinal ligament injuries, anterior annular tears, and occult anterior vertebral end-plate fractures usually occurred at multiple levels except when preexistent degenerative disk narrowing reduced spine mobility. Seven patients had acute cervical disk herniations causing cord impingement. Radiographically occult injuries are well demonstrated with MR imaging, and findings correspond to previously described surgical and anatomical pathologic conditions.

Asymptomatic degenerative disk disease and spondylosis of the cervical spine: MR imaging.

Evidence on magnetic resonance (MR) images of disk degeneration and herniation, as well as of cord and root impingement, may be regarded either as normal, age-related changes or as causative of symptoms. Individuals referred for MR examinations of the larynx without symptoms referable to the cervical spine were studied retrospectively (35 patients) or prospectively (65 patients) over a 2-year period. With a solenoid surface coil, 5-mm-thick sections were acquired in sagittal, axial, and coronal planes with T1-weighted spin-echo pulsing sequences. Disk protrusion (herniation/bulge) was seen in five of 25 (20%) patients aged 45-54 and 24 of 42 (57%) patients older than 64 years of age. Posterolateral protrusions were seen in only nine of 100 patients and occurred with greatest frequency in patients over 64 years of age. In no patient was obliteration of the intraforaminal fat seen. Spinal cord impingement was observed in nine of 58 (16%) patients under 64 years of age, and in 11 of 42 (26%) patients over 64 years of age. Cord compression was observed in seven of 100 patients and occurred solely secondary to disk protrusion in all cases. The percentage of cord area reduction never exceeded 16% and averaged approximately 7%.

MR imaging of the nasopharynx and floor of the middle cranial fossa. Part I. Normal anatomy.

The normal anatomy of the nasopharynx and floor of the middle cranial fossa was analyzed with magnetic resonance (MR) imaging. MR images from five healthy volunteers were correlated with whole-organ cryomicrotome sections from three cadavers. Anatomic connections exist between the paranasopharyngeal spaces and the surface structures of the skull base. These anatomic connections include the intimate relationship between the eustachian tube and the pharyngobasilar fascia, the attachment of the muscles of mastication and deglutition to the skull base, and vascular and nervous structures in the foramina. The inherent contrast between the soft tissues of the nasopharynx and related structures and the bone of the floor of the middle cranial fossa allowed excellent visualization of these anatomic connections.

MR imaging of the nasopharynx and floor of the middle cranial fossa. Part II. Malignant tumors.

The intracranial extension of tumors of the nasopharynx and related spaces presents a difficult imaging problem. Unlike computed tomography (CT) scans, magnetic resonance (MR) images are not limited by beam-hardening artifacts from bone or dental amalgam. Forty-six patients with malignant tumors of the nasopharynx and related spaces affecting the skull base underwent MR imaging. MR images were obtained with a 0.3-T permanent-magnet imaging system in axial, sagittal, and coronal planes. MR findings were compared with clinical records, plain radiographs, CT scans, and pathologic correlates when available. MR imaging could demonstrate neoplastic invasion of the bone of the floor of the middle cranial fossa and the vital soft-tissue structures related to it as well as or better than CT. Tumor extension was viewed directly as a continuous mass or indirectly by marrow replacement or displacement of normal structures. Specific anatomic routes through which tumors extend from the nasopharynx to the middle cranial fossa were inferred from MR findings.

Marked cerebrospinal fluid void: indicator of successful shunt in patients with suspected normal-pressure hydrocephalus.

The authors blindly reviewed the charts of 20 patients with normal-pressure hydrocephalus (a disease of unknown cause characterized radiologically as chronic communicating hydrocephalus and clinically by gait apraxia, dementia, and incontinence) who had undergone creation of a ventriculoperitoneal shunt. The initial clinical response to surgery was graded excellent, good, fair, or poor; 5-year follow-up was available in 55% of cases. The magnetic resonance (MR) images obtained in these patients were also blindly reviewed for the magnitude of cerebrospinal fluid (CSF) flow void (graded on the basis of extent rather than degree of signal loss) in the cerebral aqueduct. A significant (P less than .003) correlation existed between good or excellent response to surgery and an increased CSF flow void. The presence of associated deep white matter infarction on MR images did not correlate with a poor response to surgery. On the basis of these findings, it is suggested that patients who fulfill the clinical criteria of NPH and have an increased CSF flow void undergo creation of a shunt.

Improving the diagnostic accuracy of MR in the detection of infraspinatus tendon injuries.

PURPOSE: Our goal was to determine the accuracy of MRI in the diagnosis of infraspinatus tendon injury and more specifically to determine if the antero-posterior extent of a rotator cuff tear is predictive of infraspinatus tearing. METHOD: The MR images of 41 shoulders with surgically proven supraspinatus tears at surgery were retrospectively reviewed. The following were assessed for each of the 41 studies: the number of oblique coronal images on which a tendon defect could be seen, the angle subtended by the tear on axial images (the rotator cuff "axial angle"), and the extent of signal abnormality on sagittal images. RESULTS: The rotator cuff axial angle was 75.6 degrees in patients with infraspinatus tendon tears (ITTs) versus 40 degrees in those without ITTs, and this difference was significant (p < 0.001, t = 3.06). The mean number of oblique coronal images (obtained with a 4 mm slice and 1 mm gap) showing signal abnormality was 5.4 in the ITT group versus 2.9 in those without ITTs, and this difference was also significant (p < 0.001, t = 4.45). The mean sagittal extent of the tendon abnormality was 24.6 mm in the ITT group and 11.6 mm in those without ITTs, but the difference was not significant (p > 0.05, t = 1.1364). CONCLUSION: The axial angle and the number of oblique coronal images in which signal abnormality was present were significantly related to a higher incidence of infraspinatus tears.

Bone contusions of the knee: increased lesion detection with fast spin-echo MR imaging with spectroscopic fat saturation.

PURPOSE: To demonstrate that T2-weighted fast spin-echo (FSE) imaging with spectroscopic fat saturation (FS-FSE) increases the conspicuity between normal marrow and bone contusions in posttraumatic knees. MATERIALS AND METHODS: Seventy-six magnetic resonance (MR) studies of the knee were prospectively evaluated in 73 consecutive patients with knee pain. Conspicuity of regions of microtrabecular trauma (bone contusions) was evaluated with conventional T2-weighted imaging in the sagittal plane, T2-weighted FSE imaging in the coronal plane, T2-weighted FS-FSE imaging in the sagittal plane, and conventional T1-weighted imaging in the sagittal plane. RESULTS: Twenty-six foci of bone contusion were identified in 21 knees with the FS-FSE technique. Only 16 foci were demonstrated with conventional T2-weighted imaging. Six of the sites of bone contusion were not demonstrated with the FSE technique alone (without fat saturation). Four of the bone contusions were not seen on T1-weighted images; these sites of bone contusion were substantially more conspicuous on the FS-FSE images. In addition, FS-FSE imaging was more sensitive in demonstrating the extent of microtrabecular trauma. CONCLUSION: T2-weighted FS-FSE imaging is a sensitive and rapid method of identifying and assessing the extent of microtrabecular trauma about the knee.

Conspicuity of tumors of the head and neck on fat-suppressed MR images: T2-weighted fast-spin-echo versus contrast-enhanced T1-weighted conventional spin-echo sequences.

OBJECTIVE: The purpose of this study was to compare the conspicuity of tumors of the head and neck on MR images acquired with T2-weighted fat-suppressed fast-spin-echo and contrast-enhanced T1-weighted fat-suppressed conventional spin-echo sequences. MATERIALS AND METHODS: The MR images of 29 patients with 36 pathologically proved tumors of the head and neck were retrospectively analyzed. The conspicuity of these tumors was assessed on the T2-weighted sequence (4700/108 [TR/TE]) and on the contrast-enhanced T1-weighted sequence (500/16) with a 1.5-T system. Qualitative tumor-to-background contrast was graded separately against background muscle, fat, and mucosa (0 = not visualized, 1 = poorly visualized, 2 = fairly well visualized, 3 = well visualized), and the best overall sequence was noted for each tumor. Quantitative tumor-to-background ratios were measured for 10 of the tumors by using the same background markers. RESULTS: The mean overall qualitative tumor-to-background contrast grades for the T2-weighted sequence were tumor/muscle = 2.84, tumor/fat = 2.20, and tumor/mucosa = 1.23, and for the contrast-enhanced T1-weighted sequence, they were tumor/muscle = 2.02, tumor/fat = 1.58, and tumor/mucosa = 0.73. Overall, 86% of the tumors were better or equally well visualized on the T2-weighted images. The mean overall quantitative tumor-to-background ratios for the T2-weighted sequence were tumor/muscle = 7.93, tumor/fat = 3.34, and tumor/mucosa = 0.68, and for the contrast-enhanced T1-weighted sequence, they were tumor/muscle = 2.43, tumor/fat = 2.28, and tumor/mucosa = 0.85. CONCLUSION: The T2-weighted fat-suppressed fast-spin-echo sequence offers better contrast between tumors and adjacent muscle, fat, and mucosa than does the contrast-enhanced T1-weighted fat-suppressed spin-echo sequence and thus improves overall tumor conspicuity. In addition, the T2-weighted sequence does not require IV contrast material and can be performed more rapidly than can the contrast-enhanced T1-weighted sequence. The contrast-enhanced T1-weighted sequence may offer complementary information on the precise characterization of complex tumors and on the potential determination of tumor extent.

Patterns of contrast enhancement in the pediatric spine at MR imaging with single- and triple-dose gadolinium.

PURPOSE: To assess patterns of nerve root and spinal cord contrast enhancement in the pediatric spine at magnetic resonance (MR) imaging with single- and triple-dose gadolinium. MATERIALS AND METHODS: In three control patients with no suspected pathologic spinal condition and 19 patients with a suspected condition, spinal cords were evaluated prospectively for potential spread of tumor to cerebrospinal fluid ("drop metastases") (n = 18) or Guillain-Barré syndrome (n = 1). After enhancement with 0.1 mmol/kg gadolinium, patients without definite drop metastases (n = 8) received a booster of 0.2 mmol/kg gadolinium 30-40 minutes later; clinical follow-up was obtained 12 1/2 to 19 months later. RESULTS: Drop metastases appeared as nodular areas of enhancement in 11 patients. Vascular enhancement related to the spinal cord surface and emerging nerve roots was observed in images obtained in all control patients, as well as in patients with negative findings at lumbar puncture and at clinical or MR imaging follow-up examination (n = 6). Vascular and nerve root enhancement increased with triple-dose gadolinium and was greater in patients after radiation therapy (n = 17) than in control patients (n = 3). CONCLUSION: Use of triple-dose gadolinium did not result in detection of additional cases of drop metastases.