Selective amygdalohippocampectomy for hippocampal sclerosis: postoperative MR appearance.

PURPOSETo analyze the anatomic consequences of selective amygdalohippocampectomy (AH) in patients with hippocampal sclerosis and to correlate the clinical outcome with the MR appearance.METHODSSeventeen patients were examined with clinical and neuropsychologic examination and cranial MR after AH (7 transcortical AH, 10 trans-Sylvian AH). The clinical and neuropsychologic outcomes after AH were compared with those of anterior lobectomy (ATL).RESULTSThere was no significant difference in seizure cure between transcortical or trans-Sylvian AH and ATL. However, patients with left AH fared significantly better in terms of verbal IQ and nonverbal memory when compared with those with left ATL. Verbal memory and cognition were not significantly different in the two AH groups. Variable amounts of hippocampal and amygdala remnants were found in both AH groups and did not correlate with seizure cure. White matter change consistent with gliosis probably secondary to wallerian degeneration was demonstrated in the anterior temporal lobe to a mean distance of 4.5 cm after transcortical AH and to a lesser degree as a consequence of trans-Sylvian AH. Nine patients (53%) (4 transcortical All, 5 trans-Sylvian AH) demonstrated wallerian degeneration in the optic radiations after surgery. All had incomplete contralateral quadrantanopia.CONCLUSIONSThere is more secondary damage to the temporal lobe after AH than was previously recognized. The extent of hippocampal and amygdala resection in AH do not seem to be directly related to seizure cure. Visual field defects are common in AH because of the anterior but variable course of the optic radiations     

MR of hippocampal sclerosis: comparison of qualitative and quantitative assessments.

PURPOSEOur goal was to compare the diagnostic accuracy of subjective visual assessment versus MR volumetry in evaluating hippocampal sclerosis and to determine whether MR volumetry is needed in the lateralization of this disease process.METHODSMR imaging findings were studied retrospectively in 48 patients who underwent surgery for temporal lobe epilepsy and were compared with findings at MR volumetry on an Allegro workstation. Both visual assessment and volumetry were carried out in a blinded fashion with oblique coronal T1-weighted three-dimensional MP-RAGE images obtained on either 1.0-T or 1.5-T units. Normal right-left volumetric differences were recorded in 30 control subjects. The optimum cutoff threshold value for right-left volumetric differences in the sensitivity and specificity of volumetric measurement was obtained from receiver operating characteristic analysis.RESULTSSensitivity, specificity, positive and negative predictive values, and accuracy of visual assessment were 86%, 83%, 86%, 83%, and 85%, respectively. For MR volumetry, with the optimum cutoff threshold value of right-left difference at 0.3 cm3, sensitivity, specificity, positive and negative predictive values, and accuracy were 81%, 82%, 87%, 83%, and 85%, respectively.CONCLUSIONVisual assessment was slightly superior to or similar to MR volumetry in assessing unilateral hippocampal sclerosis. MR volumetry of the hippocampus may not be needed for the evaluation of most cases of suspected hippocampal sclerosis.     

Fast spin-echo MR in hippocampal sclerosis: correlation with pathology and surgery.

PURPOSETo identify the extent of hippocampal sclerosis in temporal lobe epilepsy with fast spin-echo MR and correlate it with histopathologic findings and surgical outcome.METHODSMR images of 30 patients with temporal lobe epilepsy and pathologically proved hippocampal sclerosis and 30 control subjects were obtained using a fast spin-echo technique with 4000/100/4 (repetition time/echo time/excitations), 16 echo train, 2- to 3-mm section thickness with interleave, 256 x 256 matrix, and 18-cm field of view. Criteria for MR diagnosis of hippocampal sclerosis included hippocampal atrophy diagnosed with MR volumetry and/or T2-weighted signal change. Hippocampal sectional areas were plotted, and T2 signal changes were topographically evaluated to identify the extent of hippocampal sclerosis, which was subsequently correlated with histopathologic findings and surgical outcome.RESULTSHippocampal sclerosis was diffuse, involving both hippocampal head and body, in 96.7% of patients (29 of 30 patients). One patient had normal MR findings. Focal hippocampal sclerosis was not seen. Histopathologic findings of hippocampal sclerosis were present in all 29 patients who had abnormal MR findings. Eighty-six percent of patients (18 of 21 patients), who were followed for at least 1 year after temporal lobectomy, were seizure free (81%, 17 of 21 patients) or significantly improved (5%, 1 of 21 patients).CONCLUSIONFast spin-echo MR enables accurate definition of the extent of hippocampal sclerosis in patients with temporal lobe epilepsy. All cases of hippocampal sclerosis identified in this study involved the hippocampus diffusely. However, leaving the posterior portion of the hippocampus during surgery does not seem to be a major factor influencing surgical outcome.     

Congenital anomalies of the inferior vena cava: embryogenesis and MR features.

This article describes the MR appearances of the six most common congenital anomalies of the inferior vena cava. As a basis for understanding those anomalies, it describes the embryology of the inferior vena cava, based on an actual study of embryos and fetuses. The article takes a fresh look at the original research in this area, discusses the possible embryogenesis of the relevant anomalies, and describes different opinions on that subject, where different opinions exist.     

Congenital anomalies of the inferior vena cava: Embryogenesis and MR features

This article describes the MR appearances of the six most common congenital anomalies of the inferior vena cava. As a basis for understanding those anomalies, it describes the embryology of the inferior vena cava, based on an actual study of embryos and fetuses. The article takes a fresh look at the original research in this area, discusses the possible embryogenesis of the relevant anomalies, and describes different opinions on that subject, where different opinions exist.     

Congenital nasal masses: CT and MR imaging features in 16 cases

The imaging studies of 16 children with pathologically proved nasal encephaloceles (eight), nasal dermal sinuses/nasal dermoids (seven), and nasal cerebral heterotopias, more commonly known as nasal gliomas (one), were retrospectively reviewed and compared with normal control subjects to define the normal anatomy and analyze deformities caused by these lesions. Nasal encephaloceles were always identified as complex masses of mixed soft tissue and CSF intensity that were contiguous with intracranial structures. The nasal glioma appeared as a mixed-intensity mass that, on the basis of the CT scan, appeared to be continuous with intracranial structures. Nasal dermal sinuses could only be identified as they coursed through the skin and subcutaneous soft tissue. They could not be identified when intraosseous. Moreover, on CT and, particularly, on MR, a number of potential diagnostic pitfalls were encountered. The most important of these was the normal fat deposition that occurs within bone during normal maturation and during aeration of the frontal sinuses and nasal bones. These fatty changes can easily be mistaken for fatty tumors if they are not recognized as normal anatomic changes. Interestingly, the classic plain film findings for congenital nasal masses were present only in the encephaloceles and nasal glioma; dermoids and dermal sinuses showed none of the classic plain film findings. In the six patients who had both CT and MR, the masses were easily identified and characterized by each imaging method. Congenital nasal masses are well characterized by both CT and MR. It is important to understand the normal changes in the anatomy of the nasofrontal region in the pediatric age group to avoid false-positive diagnoses in this region.     

In vivo MR imaging of hippocampal lesions in multiple sclerosis

PURPOSE: To investigate whether a recently improved version of the three-dimensional double inversion-recovery (3D-DIR) technique enables the in vivo detection of hippocampal lesions in multiple sclerosis (MS). MATERIALS AND METHODS: Magnetic resonance images of 16 patients and nine healthy control subjects were acquired at 1.5T. Lesions were scored on 3D-DIR images and were anatomically classified as white matter (WM), cortical, or hippocampal lesions. Associations between hippocampal, cortical, and WM lesion numbers were evaluated. Also, hippocampal lesions were retrospectively assessed on 3D-T2 and hippocampal and brain volumes were measured. RESULTS: No hippocampal lesions were detected in control subjects. By contrast, 14 out of 16 MS patients had at least one hippocampal lesion. The mean number (+/-SD) of hippocampal lesions detected with 3D-DIR was 2.6 +/- 1.8 in MS patients; only 56% of these lesions could be observed on 3D-T2. CONCLUSION: Hippocampal lesions can be visualized in vivo with 3D-DIR and occur frequently in MS. The ability to visualize hippocampal lesions in vivo is of fundamental importance to future studies focusing on the role of gray matter (GM) damage in cognitive deficits, which are common in MS.     

Incidental detection of hippocampal sclerosis on MR images: is it significant?

BACKGROUND AND PURPOSE: The prevalence of hippocampal sclerosis in the general nonepileptic patient population is not well described. While reports of its association with partial complex seizures are abundant, its absence in nonafflicted patients is generally presumed but not well documented. To test the hypothesis that hippocampal sclerosis is specific for epilepsy, we reviewed the MR imaging studies of 207 patients referred for hearing loss to determine whether high-resolution MR imaging could detect unsuspected hippocampal sclerosis in nonepileptic patients. METHODS: Our institution screens patients with hearing loss by using high-resolution coronal and axial temporal bone MR imaging that includes the hippocampus within the imaging volume. We retrospectively reviewed 207 studies randomly selected from this database. RESULTS: The hippocampus was normal in 205 patients; in the remaining two patients we identified one or more primary determinants for hippocampal sclerosis. Subsequent retrospective chart review revealed that both patients had had previously diagnosed seizure disorders. CONCLUSION: The imaging determinants of hippocampal sclerosis are not prevalent in nonepileptic patients. Incidental identification of hippocampal sclerosis on MR images is uncommon and significant, and should prompt further clinical investigation to exclude a seizure disorder.     

Craniocerebral plasmacytoma: MR features.

We report the MR imaging findings in two patients with solitary craniocerebral plasmacytoma, a benign plasma cell tumor that can arise from the skull, the dura, or, rarely, the brain. In both patients, the lesion was extraaxial and nearly isointense with gray matter on T2-weighted MR images, and diffusely enhanced after administration of contrast material, bearing some similarities to meningioma. A diagnosis of solitary craniocerebral plasmacytoma should be considered when a mass with these imaging features is seen, because total excision may not be necessary for this radiosensitive tumor.     

Clinical significance of asymmetry of the fornix and mamillary body on MR in hippocampal sclerosis.

PURPOSETo investigate the clinical significance of MR-defined asymmetry of the fornix and mamillary body for presurgical determination of the side of hippocampal sclerosis in patients with temporal lobe epilepsy.METHODSFast spin-echo MR images were evaluated for evidence of an asymmetrically small fornix and mamillary body in 33 patients with pathologically proved hippocampal sclerosis (presurgical hippocampal sclerosis group), 7 patients who had undergone anterior temporal lobectomy (mean, 3 years from surgery) because of hippocampal sclerosis (postsurgical hippocampal sclerosis group), and 34 healthy subjects (control group). Fast spin-echo hippocampal volumetry was performed in each patient.RESULTSIn the control group, 6% (2 of 34) of subjects had MR evidence of asymmetrically small fornix and none (0 of 34) of the subjects had asymmetrically small mamillary body. In the patient population, an asymmetrically small fornix was seen in 42% of presurgical hippocampal sclerosis group, 39% (13 of 33) ipsilateral, and 3% (1 of 33) contralateral, and in 71% of the postsurgical hippocampal sclerosis group (5 of 7), all ipsilateral. In the presurgical hippocampal sclerosis group, hippocampal atrophy measured with MR was more severe in patients with an ipsilaterally small fornix than in patients without. An asymmetrically small mamillary body was found ipsilaterally in 3% (1 of 33) of the presurgical hippocampal sclerosis group and in 57% (4 of 7) of the postsurgical hippocampal sclerosis group; all patients with an asymmetrically small mamillary body in the postsurgical hippocampal sclerosis group also had an asymmetrically small fornix on the same side.CONCLUSIONIn presurgical hippocampal sclerosis patients, an asymmetrically small fornix can be seen ipsilaterally on the side of the hippocampal sclerosis; however, its low frequency, its association with severe hippocampal atrophy only, and the possibility of false-positive results limit its clinical usefulness in determining the side of the seizure focus. An asymmetrically small mamillary body is too rare to be used for presurgical location of hippocampal sclerosis. However, an asymmetrically small fornix and mamillary body are frequently seen on MR images after temporal lobectomy.     

Spinal angiolipomas: MR features.

PURPOSETo determine the MR features of spinal angiolipomas and to compare these findings with their histologic appearance.METHODSThe MR examinations of three patients with surgically proved angiolipomas were reviewed for tumor location and extent, signal characteristics, and pattern of contrast enhancement, and were then compared with the histologic findings.RESULTSFour tumors were found in the three patients, all located in the posterior epidural compartment, averaging about 2.5 vertebral bodies in length. On noncontrast T1-weighted images, all lesions were inhomogeneous and hypointense relative to epidural fat. Inhomogeneous enhancement was seen in three lesions on postcontrast T1-weighted images obtained with fat-saturation techniques. Angiolipomas were least conspicuous on T2-weighted images. A high vascular content correlated with the presence of large hypointense regions on T1-weighted images.CONCLUSIONSpinal angiolipomas are typically hyperintense on noncontrast T-1-weighted images relative to other tumors. Angiolipomas that contain large hypointense foci on noncontrast T1-weighted images can be expected to have a high degree of vascularity.     

Intracranial hemangiopericytomas: MR and CT features.

PURPOSETo describe the MR and CT imaging features of hemangiopericytoma and to identify the characteristics that might distinguish them from meningioma.METHODSWe retrospectively reviewed the CT and MR findings in 34 pathologically proved cases of hemangiopericytoma. We evaluated the size, shape, and location of the tumor; the presence of hydrocephalus, edema, and mass effect; the type of dural attachment (broad-based or narrow-based) and bone changes (erosion, hyperostosis); and the tumor''s density, signal, and contrast-enhancement characteristics.RESULTSThirty of 34 tumors were 4 cm or more in greatest dimension, 32 were lobular, and only seven were in the posterior fossa. Hydrocephalus was present in 18, edema in 30, and mass effect in 33. Twenty-three had broad-based dural attachment and 11 had narrow-based attachment. All 26 unenhanced CT scans showed hyperdense tumors; 19 were heterogeneous and seven homogeneous. All 27 contrast-enhanced CT scans showed enhancement; 17 were heterogeneous and 10 homogeneous. Bone erosion was present in 17 of 29 hemangiopericytomas imaged with CT. None had hyperostosis or tumor calcifications. On T1-weighted MR images, 13 of 17 tumors were isointense with cortical gray matter; on T2-weighted image, 10 of 17 were isointense. All 14 tumors imaged with contrast enhanced T1-weighted MR imaging showed enhancement, and 13 of these were heterogeneous; eight of the 14 had a "dural tail" sign.CONCLUSIONIntracranial hemangiopericytomas are multilobulated, extraaxial tumors, sometimes associated with narrow-based dural attachment and bone erosion. Unlike with meningiomas, hyperostosis and intratumoral calcification are not present.     

MR spectroscopic evidence for thalamic and hippocampal, but not cortical, damage in multiple sclerosis.

Gray matter (GM) damage is an important pathophysiological feature in Multiple Sclerosis (MS), and may be related to clinical, including cognitive, deficits. Quantitative single-voxel (1)H-Magnetic Resonance Spectroscopy (TR/TE 6000/20 ms) was performed in 33 MS patients (11 per disease subtype; mean age 48 years, 16 females) and 10 healthy controls (mean age 43 years, 7 females). No overall spectroscopic changes were found in MS cortex. In MS thalamus, a 9% decrease of N-acetyl aspartate (NAA; P=0.005) and a 31% increase of myo-inositol (Ins; P=0.002) were found. A 21% Ins increase was observed (P=0.02) in MS hippocampus. Reduced NAA and increased Ins concentrations are thought to reflect neuro-axonal damage or loss and gliosis, respectively. Significant correlations between Ins concentrations and total-brain T(2) lesion load were found for MS thalamus (r=0.65, P<0.001) and hippocampus (r=0.57, P=0.001). MS thalamic and hippocampal Ins concentrations also correlated with each other (r=0.68; P<0.001). Cortical Gln correlated with thalamic NAA (r=-0.38; P=0.03) in MS. Thalamic and hippocampal Ins increases were most prominent in secondary-progressive (SP) patients (37% and 34%, respectively), whereas the largest thalamic NAA decrease (14%) was found in primary-progressive (PP) patients. In conclusion, thalamic and hippocampal GM pathology are important features of (progressive) MS.     

Dural cavernous angioma: MR features.

The imaging features of a cavernous angioma, which originated from the meninges, are presented. The patient harbored a second cavernous angioma within the brain parenchyma. Cavernous angioma should be included in the differential diagnosis of dural lesions, especially when other cavernous angiomas are present.     

Congenital absence of extraocular muscles: MR demonstration.

We describe a case of an infant with complete congenital absence of the extraocular muscles, noted at surgery and confirmed by multiplane MR, which found no evidence of extraocular muscle tissue. This almost certainly represents an extreme form of bilateral congenital fibrosis syndrome.     

Congenital disorders of sexual differentiation: MR findings.

A broad spectrum of anomalies of sexual differentiation may exist at birth. These include male and female pseudohermaphroditism, gonadal dysgenesis, and true hermaphroditism. When ambiguous genitalia are present, expedient identification of the anomaly is required for proper gender assignment and appropriate surgical or hormonal correction. As the appearance of the external genitalia often is not distinctive enough to make a specific diagnosis, this must be accomplished by clinical findings along with a combination of cytogenetic, biochemical, and radiologic studies. Because the causes of abnormal sexual differentiation are diverse and often exhibit incomplete expression, they produce much anatomic variability. Sonographic and radiographic studies are often used initially to evaluate such conditions. The noninvasive multiplanar nature of MR imaging makes it a useful alternative method with which to characterize the abnormal anatomy in this group of disorders, as we illustrate in this pictorial essay.