Multinodular and vacuolating neuronal tumor affecting amygdala and hippocampus: A quasi-tumor?

Multinodular and vacuolating neuronal tumors (MVNT) have been referred to as distinctive neuronal tumors whose characteristic features include multiple nodules localized in the subcortical white matter. MVNT are composed of vacuolating dysplastic neurons reactive to HuC/HuD. A significant overexpression of alpha-internexin (INA) limited to the stroma of nodules was reported in one tumor. Since genetic analyses have failed to demonstrate any consistent alterations, the nosological position as well as the nature of MVNT, namely, neoplastic or dysplastic, remains unclear. We herein present another example of MVNT involving the amygdala and anterior hippocampus in a 41-year-old man. In addition to the nodular lesions described earlier, we found INA-positive ribbon-like lesions that replaced neuropil and extended along the hippocampal gray matter. We also identified dysplastic neurons infiltrating into the CA4 hilus of the hippocampus. Intense INA expression was present in the stroma as well as the cytoplasmic membrane of dysplastic neurons and their processes. While the invasiveness suggested a neoplasm, a relatively restrictive, either nodular or ribbon-like growth pattern with INA-positive abnormal neuropil suggested a hamartoma. Such quasi-tumors should be accommodated in the World Health Organization classification of tumors of the central nervous system, as are dysembryoplastic neuroepithelial tumor and Lhermitte-Duclos disease.

Clinical and imaging characteristics of localized megalencephaly: a retrospective comparison of diffuse hemimegalencephaly and multilobar cortical dysplasia.

INTRODUCTION: Hemimegalencephaly is a well-known congenital malformation. However, localized megalencephaly, which may be one of the subtypes of hemimegalencephaly, has not been separately investigated. In the present study, we attempted to characterize the clinical and magnetic resonance (MR) imaging features of localized megalencephaly in comparison with ordinary diffuse hemimegalencephaly and multilobar cortical dysplasia. METHODS: MR findings for 43 patients with hemimegalencephaly and ten with multilobar cortical dysplasia, which is the differential diagnosis of localized megalencephaly, were retrospectively reviewed. Clinical findings such as the onset and severity of seizures and imaging findings including the affected area of the brain, structures outside of the hemisphere, and interval morphological changes were examined. RESULTS: Of the 43 patients, 11 showed signs of localized megalencephaly (25.6%). Localized megalencephaly was predominantly seen on the left side (72.7%) and had a tendency toward severe-grade seizures compared to multilobar cortical dysplasia. The frequencies of the extracerebral abnormalities in the diffuse hemimegalencephaly, localized megalencephaly, and multilobar cortical dysplasia groups were 84.4%, 36.4%, and 0.0%, respectively. There were three localized megalencephaly patients whose affected areas shrank and whose images were similar to those of multilobar cortical dysplasia. CONCLUSION: Localized megalencephaly accounts for one quarter of all hemimegalencephaly cases in this study. The incidence of extracerebral abnormalities in patients with localized hemimegalencephaly was almost half that of patients with diffuse hemimegalencephaly. Extracerebral abnormalities were absent in patients with multilobar cortical dysplasia. Associated extracerebral abnormalities may be a clue to differentiating localized megalencephaly from multilobar cortical dysplasia.

[Imaging of the brain malformations].

Cortical dysplasia (CD) is a malformation predominantly affected cerebral neocortex, resulting in disorganized brain cytoarchitecture. Normal cortical lamination is disturbed and neurons are abnormally located. Adjacent white matter is often involved. Chronic seizures are a clinical feature of developmental disorders of the brain, including CD and agenesis of the corpus callosum. A morphologically distinct form of CD is focal cortical dysplasia (FCD) characterized by the presence of cytomegalic neurons, seen in specimens resected from patients with partial epilepsy. The abnormal area usually appears normal externally, but may on occasion be represented by a wilder than normal gyrus, while the cut surface shows blurred grey-and white-matter demarcation. MR images of FCD show blurred grey-and white-matter demarcation and T2 elongation in the white matter. In our cases of FCD, no calcifications or mass effects were observed. The lesions of FCD also bear some resemblance to those of a forme fruste of tuberous sclerosis (solitary cortical tuber). The cytoarchitectual abnormalities in cortical tubers are, however, much more extensive and a characteristic feature of cortical tubers is the presence of subpial clusters of giant astrocytes and sheaves of astrocytic processes. CT images of a solitary cortical tuber show abnormal cortex with high density and frequently associated with calcifications and mass effect. An abnormal dilatated and oriented cerebral fissure is often observed around the lesion. White matter bands and blurred grey-and white-matter discrimination are occasionally seen in the white matter near the lesion. FCD is a different lesion from a solitary cortical tuber.

Diagnostic surgical neuropathology of intractable epilepsy.

As neurosurgical treatments have been increasingly applied to patients who have intractable epilepsy, much knowledge on pathological changes in surgically removed brain tissues have become clearer in recent years, as well as on the neuroimaging findings which are analyzed with a variety of techniques, including computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), single photon emission computed tomography (SPECT) in combination with digital imaging and communication in medicine (DICOM), statistical parametric mapping (SPM), subtraction ictal SPECT coregistered to MRI (SISCOM) and/or PET-guided intraoperative navigation system, as mentioned in detain in another article in this issue by Maehara et al. Representative and relatively common diseases, treated by epilepsy-surgery, are as follows; hippocampal sclerosis, amygdaloid sclerosis, coarse and macroscopic brain malformation (focal cortical dysplasia, hemimegalencephaly, tuberous sclerosis), tumors (dysembryoplastic neuroepithelial tumor, ganglioglioma, etc.), destructive lesions and the others. It is a fact, however, that there remains many problems in the diagnostic criteria or histological grading systems, especially in various cortical dysplasias described above. On the other hand, histologically minor but clinically serious lesions have become to be known through careful observations on surgically removed tissues which showed no neuroradiological findings. A good well-known example is microdysgenesis of the cerebrum which is characterized by the presence of both the white mater ectopic neurons and the vascular meandering abnormalities with glial satellitosis. There must be another important histological phenotypes of microdysgenesis, except the above-mentioned ones, that are not yet established at present. Therefore, it is believed that there remains various problems on the diagnostic neuropathology of epileptic lesions with or without neuroimaging findings in which we have to give answers in a few days to come.

[The presyrinx state due to adhesive arachnoiditis: a case report].

We report a 66-year-old woman with a presyrinx state due to adhesive arachnoiditis. She had a history of subarachnoid hemorrhage one year ago. She became aware of gait disturbance and abnormal sensation at the chest 6 months ago. Neurological examination revealed weakness of the both lower extremities and sensory disturbance below the T6 level. MR images of the thoracic spine revealed swelling of the thoracic cord at the T3-4 level, with an intramedullary hyperintensity on T2 weighted images (WI) and hypointensity on T1-WI. The intramedullary hypointensity on T1-WI was less than the CSF intensity. In addition, the thoracic cord lower than T5 level was compressed by an arachnoid cyst in the spinal canal. The preoperative diagnosis was the presyrinx state due to adhesive arachnoiditis. An operation for detachment of arachnoidal adhesion and restoration of CSF flow pathway was performed. After one month from the operation, neurological findings were improved. Postoperative MR images revealed improvement of swelling of the thoracic cord and intramedullary abnormal intensity. The arachnoid cyst in the spinal canal was decreased in the size. The presyrinx state is recently recognized condition before the formation of syringomyelia and that is known to resolve with proper treatment. We wish to emphasize we could prevent a progression to syringomyelia by a proper treatment for the presyrinx state.

[Imaging of Sturge-Weber syndrome: cranial CT and MR findings].

Sturge-Weber syndrome (SWS) is a phakomatosis characterized by vascular nevus flammeus, leptomeningeal venous angiomatosis, seizures, dementia, hemiplegia, hemianopsia, and glaucoma. Various imaging findings (gyriform calcification, atrophy of the ipsilateral hemisphere, leptomeningeal enhancement, ipsilateral choroid plexus enlargement, thickened calvarium, enlargement of paranasal sinuses and mastoid air cells, enlargement of deep veins, and white matter change adjacent to leptomeningeal enhancement) are seen in SWS. We examined the efficacy of CT and MR imaging in making the diagnosis in 14 patients. All patients underwent CT and MRI, and 11 of 14 patients underwent contrast-enhanced MRI. The most specific finding was leptomeningeal enhancement. Gyriform calcification, atrophy of the ipsilateral hemisphere, and ipsilateral chroid plexus enlargement were seen at high frequencies. Thickened calvarium was more frequent in adult patients. Enlargement of paranasal sinuses and mastoid air cells, enlargement of deep veins, and white matter change adjacent to leptomeningeal enhancement were seen in some (3-5) patients. A combination of findings of plain CT and MRI (including postcontrast MRI and MR venography) are useful for diagnosing SWS.

Clinical outcomes after corpus callosotomy in patients with bihemispheric malformations of cortical development.

OBJECT: Epilepsy in patients with bihemispheric malformations of cortical development (MCD) is typically medically intractable. Focal resection has been reported to be ineffective. Corpus callosotomy has been advocated as a treatment option, but the results have been reported only in several case reports. The authors describe a series of 10 patients with bihemispheric MCDs who underwent total corpus callosotomy. METHODS: The MCDs in these patients included lissencephaly, band heterotopia, perisylvian polymicrogyria, and tuberous sclerosis. Preoperatively all patients suffered disabling drop attacks or intense head drop seizures that caused frequent physical injuries. The follow-up period ranged from 1.4 to 5.8 years (median 3.2 years). Seizure outcome, parental assessment of daily function, and parental satisfaction with outcome were assessed postoperatively. Drop attacks disappeared completely during the entire follow-up period in eight patients and decreased to less than 10% of baseline in one. Other types of seizures were resolved completely in one patient and decreased in seven. Overall daily function improved and parents were satisfied with the surgery-related results in all patients except one who experienced a recurrence of drop attacks. There were no signs of significant and persistent neurological deficits in any case. CONCLUSIONS: Results of total corpus callosotomy in patients with bihemispheric MCDs were favorable in most cases. The procedure was particularly effective against drop attacks causing physical injuries and impaired quality of life in these patients.

[Progress in MR imaging: differential diagnosis of infectious and inflammatory diseases with MR imaging].

MR imaging is useful for diagnosis of infectious and inflammatory diseases. Diffusion weighted images (DWI) and fluid-attenuated inversion recovery (FLAIR) images revealed hyperintense signal changes in the anterior striata and cortices in patients with Creutzfeldt-Jakob disease, which were characteristic. In patients with nonherpetic and non-paraneoplastic acute limbic encephalitis, DWI and FLAIR images showed hyperintense changes in the hippocampi, amygdales, cingulate gyri, and occasionally claustrum, but not in the anterior and lateral temporal cortices, which were often involved in herpes simplex encephalitis. In ventriculitis, DWI and FLAIR images showed high signal intensity changes with niveau formation in the lateral ventricle, which indicated the presence of pus in the ventricle. In Japanese encephalitis, T2-weighted images showed high signal intensity changes in the thalami and substantia nigra, which were most often involved by Japanese encephalitis. In idiopathic cranial hypertrophic pachymeningitis, thallium-201 SPECT showed a remarkable accumulation in the abnormal dura matter. Furthermore, the abnormal uptake of thallium-201 returned to normal after treatment with corticosteroid. Thallium-201 SEPCT was useful for the evaluation of disease activity in patients with hypertrophic cranial pachymeningitis.

Abnormal hyperintensity within the subarachnoid space evaluated by fluid-attenuated inversion-recovery MR imaging: a spectrum of central nervous system diseases.

A variety of central nervous system (CNS) diseases are associated with abnormal hyperintensity within the subarachnoid space (SAS) by fluid-attenuated inversion-recovery (FLAIR) MR imaging. Careful attention to the SAS can provide additional useful information that may not be available with conventional MR sequences. The purpose of this article is to provide a pictorial essay about CNS diseases and FLAIR images with abnormal hyperintensity within the SAS. We present several CNS diseases including subarachnoid hemorrhage, meningitis, leptomeningeal metastases, acute infarction, and severe arterial occlusive diseases such as moya-moya disease. We also review miscellaneous diseases or normal conditions that may exhibit cerebrospinal fluid hyperintensity on FLAIR images. Although the detection of abnormal hyperintensity suggests the underlying CNS diseases and narrows differential diagnoses, FLAIR imaging sometimes presents artifactual hyperintensity within the SAS that can cause the misinterpretation of normal SAS as pathologic conditions; therefore, radiologists should be familiar with such artifactual conditions as well as pathologic conditions shown as hyperintensity by FLAIR images. This knowledge is helpful in establishing the correct diagnosis.

Cortical perivascular satellitosis in intractable epilepsy; a form of cortical dysplasia?

This report describes two cases of cortical dysplasia in patients with intractable epilepsy: the first case presents a 12-year-old male with a simple partial seizure of his left arm (case 1), while the second case presents an 8-year-old female with a complex partial seizure (case 2). Magnetic resonance images showed high signal intensity on T2-weighted and fluid attenuated inversion-recovery images in the cerebral cortex of right frontal convexity in case 1 and in the medial temporal lobe and anterior amygdala in case 2. The latter lesion showed focal contrast enhancement. Light microscopy revealed perivascular clustering of small round cells accompanied by dysplastic neurons in the second to sixth layers of the cerebral cortex. The perivascular small cells had uniformly round nuclei and plump, ground-glass-like cytoplasm. These cells closely apposed each other and were adhered to the capillaries. In case 2, a ganglioglioma was also found in the amygdala. Immunohistochemistry revealed that the perivascular small cells were vimentin and focally S-100 protein positive, but were negative for glial fibrillary acid protein, synaptophysin, neurofilament protein, microtubule-associated protein 2, neuronal nuclei antigen, nestin, carbonic anhydrase II, myelin basic protein, CD68, factor VIII, cytokeratin, epithelial membrane antigen, alpha-smooth muscle actin, CD20, CD45 and CD45RO. These data suggest that this is a previously undescribed form of cortical dysplasia comprising dysplastic neurons and immature perivascular cells of possible oligodendroglial or meningothelial lineage. We suggest the term cortical perivascular satellitosis be used to describe this lesion.