Arteriovenous (AV) fistulas of cerebral and spinal arteries are characterized angiographically by an immediate AV transition without a capillary bed or "nidus" as occurs in AV malformations (AVM's). The clinical presentation, morphology, radiology, and treatment of 12 patients with cerebral AV fistulas and of 12 patients with spinal AV fistulas are reviewed. In the patients with cerebral lesions, headache and seizure disorders were the most common presentations followed by subarachnoid hemorrhage, cardiac failure, progressive neurological dysfunction, and incidental detection on prenatal ultrasound study. In patients with spinal AV fistulas, weakness and sensory disturbance in the lower extremities were the most frequent clinical presentations followed by back pain, disturbances of micturition, and grand mal seizure. The etiology of the symptom complex produced by AV fistulas in each of these locations differed, with venous hypertension being important in spinal cord lesions. Of the patients with cerebral lesions, nine had a single AV fistula, one had two fistulas, and two had multiple fistulas. An AVM was observed in five patients with fistulas (two large, three small). Nine patients exhibited extramedullary AV fistulas of the spine, of whom eight had a single fistula and one had three fistulas; three patients had intramedullary spinal AV fistulas. An arterial aneurysm was found in association with two fistulas, one cerebral and one spinal. Venous ectasias or varices, frequently exhibiting mural calcification, were observed to be prominent in all AV fistulas involving cerebral arteries and in two involving spinal arteries. The location and size of the venous complexes reflected the diameter of the fistula. In addition to conventional imaging techniques (cerebral angiography, computerized tomography, and magnetic resonance (MR) imaging), MR angiography was a helpful adjunct in the evaluation of fistulas. Treatment strategies employed for AV fistulas in both locations included open surgical and endovascular procedures, frequently used in combination. A satisfactory outcome was observed in all patients.
Small asymptomatic cysts of the pineal gland represent a common incidental finding in adults undergoing computerized tomography or magnetic resonance (MR) imaging or at postmortem examination. In contrast, large symptomatic pineal cysts are rare, being limited to individual case reports or small series. The authors have reviewed 24 cases of large pineal cysts. The mean patient age at presentation was 28.7 years (range 15 to 46 years); 18 were female and six male. Presenting features in 20 symptomatic cases included: headache in 19; nausea and/or vomiting in seven; papilledema in five; visual disturbances in five (diplopia in three, "blurred vision" in two, and unilateral partial oculomotor nerve palsy in one); Parinaud's syndrome in two; hemiparesis in one; hemisensory aberration in one; and seizures in one. Four lesions were discovered incidentally. Magnetic resonance imaging typically demonstrated a 0.8- to 3.0-cm diameter mass (mean 1.7 cm) with homogeneous decreased signal intensity on T1-weighted images, increased signal intensity on T2-weighted images, and a distinct margin. Hydrocephalus was present in eight cases. The cysts were surgically excised via an infratentorial/supracerebellar approach (23 cases) or stereotactically biopsied (one case). Histological examination revealed a cyst wall 0.5 to 2.0 mm thick comprised of three layers: an outer fibrous layer, a middle layer of pineal parenchymal cells with variable calcification, and an inner layer of hypocellular glial tissue often exhibiting Rosenthal fibers and/or granular bodies. Evidence of prior hemorrhage, mild astrocytic degenerative atypia, and disorganization of pineal parenchyma were often present. Postoperative follow-up review in all 24 cases (range 3 months to 10 years) revealed no complications in 21, mild ocular movement deficit in one, gradually resolving Parinaud's syndrome in one, and radiographic evidence of a postoperative venous infarct of the superior cerebellum with ataxia of 1 week's duration in one. Of the patients referred for study, the cysts were most often initially misdiagnosed as a pineocytoma in eight and a pilocytic astrocytoma in three. Only two patients were correctly diagnosed as having pineal cysts. This stresses the importance of recognizing the histopathological spectrum of pineal cysts, as well as correlation with radiographic findings, if a correct diagnosis is to be attained.
Biologically malignant pilocytic astrocytomas are rare. Precise morphologic criteria permitting their identification and clinically meaningful distinction from more ordinary pilocytic astrocytomas have not been developed. The histologic grading schemes applied to fibrillary astrocytomas--ones based on nuclear atypia, increased cellularity, mitotic activity, endothelial proliferation, and necrosis--are thought not to correlate with prognosis in pilocytic astrocytomas. Nonetheless, these features were systematically sought in 107 cerebellar pilocytic astrocytomas, four of which were histologically malignant. The clinical, morphologic, and flow cytometric features of these cases were studied. The incidence of histologic malignancy occurring spontaneously in otherwise typical pilocytic astrocytomas was 0.9%; that occurring after radiation was 1.8%. The four histologically malignant tumors occurred in two males and two females, ages 6 to 18 years. All showed increased mitotic activity (three to five mitoses per high-power microscopic field [250x]). Endothelial proliferation and necrosis were present in three and two cases each. DNA ploidy analysis showed the spontaneously occurring malignant-appearing tumors to be aneuploid, whereas both previously radiated tumors were tetraploid; 5% to 11% of cells were in S phase. The appearance of histologic malignancy in pilocytic astrocytoma is rare and less reliably correlated with prognosis than in patients with fibrillary astrocytomas. Essential features of such tumors include a high mitotic index and perhaps a high percentage of cells in S phase.
Serial postoperative magnetic resonance (MR) studies were obtained in 21 patients who underwent somatotopically placed stereotactic radiofrequency (rf) ventralis lateralis thalamotomy for the control of movement disorders. The MR studies were reviewed to determine the MR characteristics of early-phase (less than or equal to 7 days) and late-phase (8 days to 5 months) lesions. Surgery was performed for the control of parkinsonian tremor (14 cases), intention tremor (six cases), and essential tremor (one case). Single rf lesions were made with an electrode (1.6 mm in diameter, 3 mm in tip length) heated to 78 degrees C for 60 seconds. On MR images of the lesions, three distinct concentric zones were identified, described as follows (from the center outward). Zone 1 gives increased signal on long-relaxation time (TR) (T2-weighted) MR images in early- and late-phase lesions and decreased signal on short-TR (T1-weighted) MR images in early-phase lesions only. Zone 2 gives decreased signal on long-TR (T2-weighted) images in early- and late-phase lesions; it gives isointense signal on short-TR (T1-weighted) images in early-phase lesions only. Zone 3 gives increased signal on long-TR (T2-weighted) images in early-phase lesions only and decreased signal on short-TR (T1-weighted) MR images in early-phase lesions only. It is considered that in early-phase lesions, Zone 2, with a mean diameter of 7.3 mm on axial long-TR (T2-weighted) imaging, represents an area of hemorrhagic coagulation necrosis. In late-phase lesions, Zone 2, with a mean diameter of 5.0 mm on axial long-TR (T2-weighted) imaging, represents hemosiderin deposition. Zone 3 likely represents edema, and this zone disappears between the early and late periods. From regression analysis, lesion size began to stabilize at approximately 7 months with a mature lesion diameter of 3.3 mm. Long-term follow-up monitoring (median 16 months) showed good tremor control. Based on clinical and radiological findings, the authors conclude that forms of hemoglobin are suitable markers to assess the size of rf lesions. Serial MR imaging provides a noninvasive means of studying the evolution of rf thalamotomy lesions.
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