Postmortem MRI of the brain with neuropathological correlation

We prospectively correlated in vitro MRI of the brain with the neuropathological findings in patients with suspected intracranial disease. In vitro MRI was performed on 91 consecutive formalin-fixed whole-brain specimens. In 60 cases, the images were correlated with the neuropathological findings (number of lesions, lesion boundaries, spread of oedema and type of lesions). As compared with neuropathology, MRI showed an equal number of lesions in 50 cases, more in 5, and less in 5 specimens, resulting in a sensitivity of 83.3%. The extent of perilesional oedema was better seen on in vitro MRI than on gross pathology. Microscopic extent of glial tumours was underestimated on both T2-weighted images and macroscopic examination. Neuropathology remains the reference study, since on in vitro MRI primary brain tumours, metastatic deposits and non-neoplastic space-occupying lesions cannot be differentiated. However, in our study MRI had a specificity of 76.6%. MRI of postmortem specimens is sensitive to focal brain lesions, and can focus the attention of the neuropathologist to abnormal regions.

Influence of magnetic field strength on T2* decay and phase effects in gradient echo MRI of vertebral bone marrow

OBJECTIVE

The goal of this study was twofold: first, to quantify the influence of magnetic field strength (B0) on T2* and T2susceptibility relaxation rates in vertebral bone marrow; and second, to determine the significance of in-phase/out-of-phase phenomena in GE MRI as a function of TEs at different B0 values.

MATERIALS AND METHODS

Magnetic resonance imaging of the spine was performed at 1.5, 1.0, and 0.2 T using a GE sequence (2D-FLASH) with variable TE. Vertebral body signal intensities were measured and plotted against TE values. These curves were used to calculate T2* decay of bone marrow at different B0 values.

RESULTS

At all field strengths, we observed exponential signal decay, modulated by a cosine function, the periodicity of which was proportional to B0. The T2* values of vertebral bodies were 9.7 +/- 1.8 ms at 1.5 T, 17.2 +/- 2.4 ms at 1.0 T, and 53 +/- 5 ms at 0.2 T. True T2 relaxation time (independent of field strength) was 62 +/- 4 ms. The T2susceptibility was 11.7 ms at 1.5 T, 24.8 ms at 1.0 T, and 585 ms at 0.2 T.

CONCLUSION

We conclude that at low B0, susceptibility effects become less important and T2* approaches true T2 relaxation.

Intrasellar bony spine, a possible cause of hypopituitarism

A 39-year-old male patient with long-standing pituitary deficiency is reported. The onset of hypopituitarism was probably at about the age of 12 years, but diagnosis was not made until 6 years later. Since then he has received substitutive hormonal treatment and was referred with complaints suggestive of growth hormone deficiency. Retrospective study of a skull radiography performed at the age of 18 years revealed a calcified lesion in the sellar region. Additional radiological examinations showed the presence of a 9-mm intrasellar bony spine. Magnetic resonance examination showed a ventrally extending arrow-shaped bone deformation in continuity with the dorsum sellae, consisting of a hyperintense structure comparable with the intensity of the bone marrow of the dorsum and clivus. Computed tomography scanning confirmed in detail the morphology of the bony spine. This deformity probably represents the non-regressed cephalic segment of the notochord. Only in four reports has the existence of this congenital abnormality been described, but this is the first one in which hypopituitarism can be regarded as a complication of the intrasellar spine.

Low-field versus high-field MR imaging of the knee: a comparison of signal behaviour and diagnostic performance

A prospective study was undertaken to compare MR imaging of the knee obtained with low-field and high-field systems. In 10 subjects, MR imaging of the knee was performed on a 0.2 T permanent magnet and on a 1.5 T superconductive system. Similar spin echo (SE) and 3D-FISP (3D Fourier transform with steady state precession) acquisitions were obtained. Comparative image analysis was performed independently by four radiologists. Results show that the image quality and diagnostic performance delivered by state-of-the-art 0.2 T and 1.5 T systems is equivalent. Advantages of the 1.5 T system included: better signal-to-noise ratio, shorter scan times, better visualization of asymptomatic grade 1 meniscal degeneration on SE images. Advantages of 0.2 T images were: decreased chemical shift, susceptibility and flow artifacts, improved evaluation of subchondral bone on 3D-FISP images, slightly better patient tolerance. We conclude that, for MR imaging of the knee, a low-field system is a cost-effective alternative to more expensive superconducting units.

Understanding chemical shift induced boundary artefacts as a function of field strength: influence of imaging parameters (bandwidth, field-of-view, and matrix size)

OBJECTIVE

To study the importance of chemical shift induced boundary artefact (CSA) at different field strengths and the implications for pulse sequence design with respect to receiver bandwidth (BW), field-of-view (FOV) and matrix size.

MATERIALS AND METHODS

A fat-water phantom was examined in MR systems of different field strength (1.5 T, 1.0 T and 0.2 T), using pulse sequences with different receiver BW, FOV, and matrix size. The chemical shift was quantified by measuring the width of the bright and dark misregistration rims seen at the planar fat-water interface. The measured chemical shift was compared with the theoretically calculated chemical shift.

RESULTS

Excellent correlations were found between predicted chemical shift and measurement results in our experiments. The width of the CSA (in millimetres) is directly proportional to field strength, inversely proportional to receiver BW and hence to the strength of the readout gradient, directly proportional to FOV, and inversely proportional to matrix size.

CONCLUSION

CSA occurs at all magnetic field strengths, but given a certain BW it is more pronounced at higher fields. Although the CSA in Hz is directly proportional to field strength, the visible CSA at low-field was slightly higher than theoretically expected. The relative lack of CSA in low-field strength images permits the application of narrow receiver BW sequences, resulting in increased signal to noise ratio.

Randomised double blind trial of the safety and efficacy of two gadolinium complexes (Gd-DTPA and Gd-DOTA)

The main difference between macrocyclic Gd-DOTA and linear Gd-DTPA complexes is the greater stability of the former which theoretically might reduce biological interactions in man. To evaluate the clinical relevance of this property, 300 unselected neurological patients were included in a randomised double-blind comparison involving five European centres, focused mainly on the tolerance of these two contrast media. Clinical tolerance was assessed immediately after the procedure and 24 h later. Adverse events were found with a similar frequency in the two groups (17.3% for Gd-DOTA and 19.3% for Gd-DTPA). Minor neurological symptoms were the most frequent (48.6%) headache being the most common (29.2% of adverse events). No difference in efficacy was found.

Magnetic resonance characterization of a long-standing pituitary abscess

A 56-year-old male patient with panhypopituitarism is presented. Magnetic resonance (MR) examination of the pituitary region revealed a pituitary mass with markedly increased signal intensity on T1-weighted images and low signal intensity on T2-weighted images. At surgery, a large amount of purulent material was removed. At light microscopy, the tissue was demonstrated to be a pituitary abscess occurring in an otherwise normal pituitary gland. The high signal intensity on T1-weighted images does not correspond to the only MR description of a pituitary abscess given until now, reporting a mass isointense to white matter. These signal characteristics could emanate from the presence of small amounts of blood breakdown products in the proteinaceous content of the abscess. MR appearance of a pituitary abscess is possibly aspecific and could depend on the pathological composition of the lesion.

Detection of herpes simplex virus in the cerebrospinal fluid of patients with encephalitis using the polymerase chain reaction

Herpes simplex encephalitis is a neurologic emergency demanding immediate institution of specific therapy in order to prevent mortality. Diagnosis, however, is a complex matter with controversy existing over the appropriateness of brain biopsy. We report the demonstration of herpes simplex virus DNA by means of the polymerase chain reaction (PRC) in the cerebrospinal fluid of 3 patients with herpes simplex encephalitis. One of the patients suffered from brain-stem encephalitis with high intensity signals in the pons on magnetic resonance imaging, the second reported case of this entity. The PCR for herpes simplex on a control series of cerebrospinal fluid of 20 patients with other central nervous system infections was negative. PCR of cerebrospinal fluid offers a sensitive, specific and rapid diagnosis of herpes simplex encephalitis, making brain biopsy unnecessary. Still, the importance of strict measures to prevent contamination cannot be stressed enough. It is possible that due to the high sensitivity of the PCR, herpes simplex may be found in other infectious syndromes of the central nervous system.

Multiple pterygium syndrome with body asymmetry

We report on a fetus with multiple pterygia in the popliteal, antecubital, intercrural, axillary, and nuchal region, arthrogryposis, camptodactyly, anal atresia, hypospadias, ambiguous genitalia, and neonatal death. Arthrogryposis was much more pronounced at the left than at the right side. Moreover, there was gross body asymmetry with hypoplasia of the left arm, leg, pelvis, and kidney. As this spectrum of anomalies does not fit any of the known multiple pterygium syndromes, this patient adds another clinical entity to the already wide spectrum of multiple pterygium syndromes.

MRI of acoustic schwannoma: a retrospective study of 89 tumours

Magnetic resonance imaging (MRI) is now considered the diagnostic study of choice for evaluation of patients with suspected acoustic schwannoma. This retrospective study of 118 MR examinations presents an analysis of the MR findings of 89 acoustic tumours in 86 patients. The method of examination included precontrast and gadolinium(Gd)-enhanced MRI in 72 and plain MRI in 14 patients. The common MR-appearances of acoustic schwannomas were: on T1-weighted images (WI) isointense (36%) or slightly hypointense (64%) relative to the brainstem; intense and homogeneous contrast enhancement in 62%; the shape of the tumour was round or oval in 71%; the tumour was centred at/or located in the internal auditory canal (IAC) in 80%. The small acoustic schwannomas were mostly round or oval in shape and showed homogeneous signal intensity (SI) both before and after Gd. The larger acoustic tumours were more heterogeneous in morphology and SI. The significance of these and other signs, early diagnosis and differential diagnosis are discussed.

Tuberous sclerosis: CT and MRI characteristics

Tuberous sclerosis is a disease characterized by the presence of hamartomatous nodules in various organs, including the brain. Thirteen CT scans and four MR investigations were performed in 13 patients. CT is superior to MR in demonstrating the presence of subependymal nodules, thereby confirming or establishing the diagnosis of tuberous sclerosis. MR is superior to CT in demonstrating the peripheral lesions, which are characterized by a long T2-relaxation time. Differentiation between cortical tubers and subcortical lesions is not yet accurate.

Stereotactic indications for neuroradiological differential diagnosis

The modern neurodiagnostic techniques of MR imaging, CT scanning and angiography provide valuable morphological information that, although highly sensitive to tumour localisation, still lacks comparable specificity as to the exact histological nature of those lesions demonstrated. Biopsy remains necessary. To patients with potentially inoperable lesions or lesions best treated by chemotherapy or irradiation, modern techniques of neurosurgery now offer the option of precise stereotactic biopsy through small twist-drill burr holes as opposed to open biopsy. The interrelationships between MR, CT, angiography and stereotactic biopsy and their respective roles in the establishment of a definitive diagnosis are discussed.

Stereotaxic target calculation. Theory and practice

Modern neuro-imaging techniques have significantly increased the accuracy of stereotactic procedures and have thereby generated a renewed interest in guided brain surgery. This paper describes the neuroradiological aspects of stereotaxic target calculation (x-, y-, z- coordinates) using the Riechert-Mundinger (Fisher) frame for computed tomography (CT). Selected cases are shown, illustrating patient positioning, CT technique, target identification and calculation. The importance of obtaining pre- and post-stereotaxic CT examinations is emphasized. Finally, future developments such as magnetic resonance (MR) guided stereotaxis and integrated functional-anatomical computer generated 3-dimensional maps, are briefly discussed.

Tricho-rhino-phalangeal syndrome type I (TRP I) due to an apparently balanced translocation involving 8q24

Tricho-rhino-phalangeal (TRP) syndromes type I and II are caused by a defective gene located on chromosome 8q24.1. We report a family with 2 sibs affected with TRP type I in combination with an apparently balanced chromosome (8;18) translocation involving 8q24.11. It is very likely that the 8q24 translocation breakpoint is physically linked to the TRP gene(s), thereby facilitating future efforts to clone the TRP gene(s).

Epidural and subdural contrast in myelography and CT myelography

A retrospective study of 624 lumbar myelographic and CT myelographic procedures was undertaken to evaluate the frequency, radiographic and clinical relevance of contrast medium outside the dural sac. Our findings indicate that epidural contrast is frequently identified on CT scans with highly sensitive window settings (in 35.4% of all CT myelographic studies). Standard myelographic films are less sensitive for the detection of epidural contrast (9.6%). Subdural contrast is far less often encountered (in 2.4% of CT myelographic studies and in 3.2% of standard myelographic films). We believe leakage of contrast to occur through the puncture site into the epidural and subdural space.

Acoustic schwannoma: MR findings in 84 tumors

MR imaging is the study of choice for the examination of patients with suspected acoustic schwannoma, because of its high sensitivity, especially after the use of contrast material. This essay illustrates the common MR features of acoustic schwannomas as seen in a study of 84 tumors. We pay special attention to the role of MR imaging in the distinction between acoustic schwannoma and meningioma.

The association of meningioma and pituitary adenoma: report of seven cases and review of the literature

Seven patients with the co-occurrence of meningioma and pituitary adenoma are reported. Diagnosis was based on histological examination and if not available on MR imaging. Extensive review of the literature reveals only 18 other cases with this association if meningiomas appearing after radiation therapy for pituitary tumors are excluded. As in isolated meningiomas, the female-to-male ratio is high. A preponderance of perisellar meningiomas is apparent. Another distinct characteristic of this combination is not revealed, since no specific typing of the meningioma and no specific endocrine syndrome is uncovered. Two patients presented with multiple meningiomas, of which one showed two histologically different tumor types. The presence of other tumors in association with pituitary adenomas and meningiomas in our series is striking and could suggest a genetic dysregulation leading to the development of these tumors.

Transient musical hallucinosis of central origin: a review and clinical study

A 52 year old, right handed, hearing impaired woman was admitted with headache and neck stiffness. The only neuropsychological symptom was transient auditory perceptions in the left ear, which were musical, seemed familiar and were not influenced by verbal communication. CT and MRI showed a right subarachnoid haemorrhage, while brainstem auditory evoked potentials failed to reveal a brainstem lesion. In patients with organic cerebral disease, unilateral auditory hallucinations (AHs) may indicate a lesion in the contralateral hemisphere. However, according to this review the type of AHs (verbal versus musical) is not consistently associated with a cerebral lesion on either side.

MR imaging of tuberculous spondylitis

This case report describes a patient presenting with symptoms of progressive paresis of both legs. An X-ray of the thorax demonstrated an aspect consistent with miliary tuberculosis. Magnetic resonance imaging (MRI) of the thoracic spine revealed medullary compression. The patient underwent a laminectomy and the diagnosis of spinal epidural tuberculoma was made. The patient has been treated with isoniazid, rifampicin and pyrazinamide. After a period of six months, she made a complete recovery.

MR and CT imaging of paraspinal textiloma (gossypiboma)

This report describes two cases of textiloma (gossypiboma, foreign body granuloma). These so-called "cottonoids" (Codman, U.S.A.) were inadvertently left behind in the operation wound following spinal surgery for an intervertebral disk herniation. Both textilomas were located paraspinally. These relatively uncommon lesions should be differentiated from paraspinal tumors, as well as from other postoperative complications, such as scar formation. Although plain radiography generally gives a characteristic image due to a marking filament, the CT and especially MR findings are less well known.