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Infectious diseases of the central nervous system vary in frequency in different locations in America and Europe. What is common in Brazil can be a sporadic presentation in Europe. Cooperative work gathering experiences from neuroradiologists working in various places can be achieved and will help to identify uncommon cases that can present in our daily practice.

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PURPOSE: To evaluate the role of stereotactic radiosurgery in the treatment of angiographically occult vascular malformations (AOVMs). METHODS AND MATERIALS: From 1987 to 1996, 21 patients, 10 males and 11 females, median age of 41 years (range: 7-75 years), with an intracerebral AOVM underwent stereotactic radiosurgery at our institution. All were considered at high risk for surgical intervention. The vascular lesions were located in the brainstem (17 patients), basal ganglia (2), occipital lobe (1), and cerebellum (1). Diagnosis was based on high-resolution magnetic resonance imaging (MRI). Clinical presentation at onset included previous intracerebral hemorrhage (20 patients) and epilepsy (1). All patients were treated with a linac-based radiosurgical technique. The median dose delivered was 25 Gy (range 13-50 Gy), typically prescribed to the 80-90% isodose surface (range 50-90%), which corresponded to the periphery of the vascular malformation. Patients were followed by clinical neurologic assessment and by MRI on a regular interval basis. RESULTS: Follow-up was obtained in 20 patients; clinical or MRI information was not available for 1 patient, and this patient was excluded from our analysis. At a median follow-up of 77 months (range: 4-141 months), follow-up MRIs postradiosurgery do not demonstrate any changes in the appearance of the AOVM. Four patients developed an intracranial bleed at 4, 8, 35, and 57 months postradiosurgery. Annual hemorrhage rates were considerably higher in the observation period preradiosurgery than postradiosurgery (30% vs. 3.2%, p < 0.001). Complications postradiosurgery were observed in 4 patients. Three patients developed mild to moderate edema surrounding the radiosurgical target, expressed at 5, 8, and 24 months, respectively. In all cases, the edema was transient and resolved completely on subsequent MRIs. One of the 4 patients developed radiation necrosis 8 months after radiosurgery. CONCLUSION: The use of stereotactic radiosurgery in the treatment of AOVM continues to be controversial. Our results appear to show a reduction in the risk of symptomatic hemorrhage post treatment. Patients with previous history of hemorrhage or progressive neurologic deficit and small, well circumscribed lesions may benefit from a trial of stereotactic radiosurgery.

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We present a case of an exophytic spinal primitive neuroectodermal tumor that, radiologically, simulated an extramedullary nerve sheath tumor, meningioma, or metastatic tumor deposit. MR imaging provided discrete anatomic localization of the tumor, enabling exclusion of multicentricity in the brain and spinal cord.

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PURPOSE: To characterize gliomatosis cerebri on computed tomographic (CT) and magnetic resonance (MR) images. MATERIALS AND METHODS: MR and CT studies of 22 patients with cerebral gliomatosis were reviewed retrospectively. Tumor was confirmed with autopsy (n=5) or biopsy. Distribution and extent of disease were assessed, and disease progression was followed. RESULTS: Tumor involved at least two lobes of the brain in all patients, with extension to the corpus callosum in 12, basal ganglia and thalamus in 17, brain stem in three, and cerebellum in two patients. Widespread invasion with hyperintensity was noted on proton-density- and T2-weighted MR images. At CT, areas of hypo- or isoattenuation were noted, and no contrast enhancement occurred. Extent of tumor was greater on MR images than on concurrent CT scans in all patients. The MR findings closely correlated with the autopsy findings. CONCLUSION: Gliomatosis cerebri is best detected with MR imaging. The pattern is infiltrative with enlargement of cerebral structures.

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The authors describe a 29-year-old woman who presented with Gerstmann syndrome secondary to underlying left atrial myxoma. The clinicoradiologic features of atrial myxoma, as well as its neurologic manifestations, are reviewed.

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To facilitate the study of cerebellar degenerative disorders, improved clinical diagnosis is needed. Cerebello-olivary atrophy is pathologically distinct, but until now its diagnosis has been thought to require postmortem examination. This condition was considered as a possible diagnosis in two patients from different families with dominantly inherited ataxia. The affected members of each family demonstrated a stereotyped, progressive, "pure" cerebellar syndrome, which began with gait ataxia followed years later by dysarthria and limb ataxia. The autopsy findings for the first patient's father revealed paleocerebellar and olivary atrophy, characteristic of cerebello-olivary atrophy. Magnetic resonance imaging (MRI) of the brain of both patients revealed medullary, vermian and, to a lesser extent, cerebellar hemispheric atrophy but a normal pons. Dominantly inherited cerebello-olivary atrophy was diagnosed in both patients. Characteristic clinical and MRI features thus permit a confident clinical diagnosis of dominantly inherited cerebello-olivary atrophy. Recognition of this entity during life should advance the classification of cerebellar degenerative disorders.

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Subarachnoid hemorrhage developed in a patient intoxicated with methanol. Computed tomography performed at the time of admission suggested this complication. The hemorrhage was definite and extensive by the 5th day after admission and was accompanied by left caudate and pontine hemorrhage, as well as severe cerebral edema. The authors are unaware of any previous reports of subarachnoid hemorrhage associated with ingestion of methanol.

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We report experience with 11 patients misdiagnosed for years, on the basis of computed tomography (CT) and angiography, as harbouring brainstem tumours in whom magnetic resonance imaging (MRI) demonstrated cavernous angiomas. Seven had undergone external irradiation, 2 had a ventriculo-peritoneal shunt, 2 developed aseptic femur necrosis following corticosteroid treatment, 1 had undergone a biopsy with a pathological diagnosis of glioma. CT had depicted ill-defined, hyperdense, faintly enhancing lesions. Angiography was normal, or showed an avascular mass or subtle venous pooling. MRI delineated discrete lesions, typical of cavernous angiomas, with a mixed hyperintense, reticulated, central core surrounded by a hypointense rim. Six patients subsequently underwent stereotactic radiosurgery without changes in clinical status or lesion. Although hemorrhagic neoplasms may mimic the clinical course and MRI appearance of cavernous angiomas, MRI is useful in the diagnosis of brainstem cavernous angiomas and should be performed in patients with suspected brainstem tumours.

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PURPOSE: To describe the clinical, radiographic, and neuropathologic features of bilateral thalamic glioma. METHODS: We searched our hospital records (1963 to present) to identify patients diagnosed as having the disease. RESULTS: Our search revealed eight patients, ranging in age from 8-63 years, with bithalamic tumor diagnosed by angiography, CT, and/or MR. All patients displayed personality changes and/or mental deterioration, including memory loss, inattention, confusion, hallucination, hyperphagia, or slow mentation. Unilateral motor weakness was also noted in six cases. The tumor always involved the medial aspect of the left and right thalami, but was often more extensive. The pathology was determined to be grades I-IV astrocytoma, confirmed by stereotactic biopsy or autopsy in six. Mild to moderate hydrocephaly occurred in some cases and was considered to be a contributing factor to mental deterioration. No correlation was found between age and type of tumor. CONCLUSIONS: Bilateral glioma of the dorsomedial and intralaminar nuclei of the thalamus can be a primary cause of dementia that has not been well-recognized in the past. CT and particularly MR should be considered for patients presenting with personality change or dementia, because of the possible presence of this unusual but devastating disease.

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Dysplastic gangliocytoma (Lhermitte-Duclos disease) is a rare entity. Usually presenting as a posterior fossa mass, dysplastic gangliocytoma is not a true neoplasm but a hard-to-characterize lesion that may represent an abnormality of cell migration or a phacomatosis. Previous reports of CT findings are rare in the radiologic literature, and high-field (1.5 Tesla) MR images have never been described in the pediatric age group. We present a case of dysplastic gangliocytoma in a one-year-old boy with CT and MR findings.

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Eight patients (seven women and one man) with multiple intracerebral cavernous angiomas (cavernomas), also known as angiomatosis cerebri, were examined with high-field magnetic resonance imaging (MRI). Although previous articles have referred to such cases, a series similar to the one reported here has apparently not been described in the radiology literature. The patients presented with seizures, progressive neurologic deficit or cerebral hemorrhage. In all eight cases the multiplicity of the lesions was an incidental finding in the magnetic resonance images. The MRI appearance of the cavernomas, although characteristic, is similar to that of other angiographically occult intracranial vascular malformations, in particular thrombosed arteriovenous malformations and mixed vascular malformations, as well as that of hemorrhagic metastases. Additional criteria, such as the absence of edema, the presence of calcifications and the temporal evolution of the cavernomas on serial scans, should allow cavernomas to be differentiated from hemorrhagic metastases. The exquisite sensitivity in detecting angiomatosis cerebri and the ability to show the evolution of internal hemorrhage in individual lesions make MRI the method of choice for diagnosing and following this condition.

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A characteristic appearance of occult cerebrovascular malformations (OCVMs) on high-field spin-echo magnetic resonance imaging (MRI) has been described previously. The authors report a series of 21 of these lesions located in the brain stem and examine the clinical and MRI characteristics. Most of these lesions display a prolonged, fluctuating clinical course, which suggests multiple sclerosis or brain-stem glioma. Although the possibility of hemorrhagic neoplasms mimicking the MRI appearance of OCVMs has been emphasized recently, distinguishing between these two groups of lesions should be possible in most cases. MRI should allow the diagnosis to be made with sufficient certainty to avoid unnecessary intervention for OCVMs in this delicate location.

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Spinal angiolipomas are rare benign tumors containing vascular and mature adipose elements. In greater than 90% of the cases they are located in the epidural space. The clinical symptomatology is nonspecific, but CT and particularly MR studies allow for a precise diagnosis. Computed tomography (four cases in the literature plus one explored in our department) showed a hypodense lesion in 80% of the cases. In one case the angiolipoma was isodense to the cord. Magnetic resonance (three cases in the literature plus two explored in our department) showed a more or less homogeneous mass with a signal in T1- and T2-weighted images close to that of the subcutaneous fat. The infusion of gadolinium (one case in the literature plus one of ours) is helpful as an indicator to the degree of vascularization of the angiolipoma.

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Agenesis of the corpus callosum is usually associated with brain malformations or with anomalies outside the central nervous system. A colloid cyst of the third ventricle may give rise to hydrocephalus and even sudden death. The authors report the case of a 23-year-old man in whom both these uncommon conditions coexisted. The findings on computed tomography and magnetic resonance imaging are described. The colloid cyst was completely excised through a frontal craniotomy and the patient made a smooth recovery.

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Although relatively uncommon, interhemispheric subdural hematoma (ISDH) occurs more frequently than was suspected before the advent of computerized tomographic (CT) scanning. When its mass is sufficiently large to compress the medial cerebral hemisphere, specific focal neurological abnormalities may occur. These include weakness of the contralateral leg, or contralateral hemiparesis with the leg being weaker than the arm. On the unenhanced CT scan ISDH is seen as a crescent shaped, midline hyperdensity. Treatment is dictated by the clinical course. Evacuation of the hematoma by parasagittal craniotomy is recommended if the symptoms are pronounced.

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We describe a patient who developed a persistent pleural effusion due to a subarachnoid-pleural fistula after operation for lung carcinoma and then review the literature on iatrogenic subarachnoid-pleural fistulas.

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