✓ Among 91 patients with unruptured intracranial arteriovenous malformations (AVM's), 16 patients had 26 unruptured intracranial saccular aneurysms. An actuarial analysis showed the risk of intracranial hemorrhage among patients with coexisting aneurysm and AVM to be 7% per year at 5 years following diagnosis compared to 1.7% for patients with AVM alone. The difference in length of survival free of hemorrhage was significant (log-rank, p < 0.0007). Several angiographic and clinical parameters were investigated to better understand the relationship of these lesions. The aneurysms occurred in similar percentages in patients with small, medium, and large AVM's. Twenty-five aneurysms were on arteries feeding the malformation system, almost equally distributed proximally and distally. Eleven aneurysms were atypical in location, and all arose from primary or secondary branch feeders to the malformation; 24 were on enlarged feeding arteries. Eleven (16%) of the 67 patients with high-flow AVM's had associated aneurysms, compared with five (21%) of the 24 patients with low-flow AVM's. Four (16%) of 25 low-shunt malformations and 12 (18%) of 65 high-shunt malformations had associated aneurysms. All five aneurysms associated with low-shunt malformations were on a direct arterial feeder of the malformation. These data suggest that the intracranial AVM's predispose to aneurysm formation within AVM feeding systems and that the mechanism is not simply based upon the high blood flow or high arteriovenous shunt in these systems.
Robert D. Brown Jr., David O. Wiebers and Glenn S. Forbes
Daniela Lombardi, Bernd W. Scheithauer, David Piepgras, Fredric B. Meyer and Glenn S. Forbes
✓ The term “angioglioma” denotes a highly vascular glioma, most of which are low-grade lesions associated with a favorable prognosis. The authors encountered an example of this pathology, a cystic oligodendroglioma associated with prominent vasculature which both clinically and histologically mimicked an occult arteriovenous malformation (AVM). This case and reports of the association of AVM and glioma prompted a histological review of 1034 surgically resected AVM's, both angiographically occult and visible, among which no oligodendroglial or astrocytic forms of “angioglioma” were found. Eight cases were observed, however, wherein oligodendroglial cells were increased in number within or about the malformation. Two basic histological patterns of oligodendroglial cell excess were seen; one appeared to be malformative in nature with abnormal disposition of oligodendroglial cells being an integral part of the AVM, whereas in the other an apparent increase in cellularity seemed the result of chronic ischemia with condensation of white matter. It appeared that the areas of increased oligodendrocyte content seen in association with AVM are non-neoplastic lesions that exhibit two rather distinct histological patterns of differing origin.
In an effort to determine the frequency of “angioglioma,” the authors examined Tissue Registry data for several glioma groups in which highly vascular examples are prone to occur. Tumors selected for study included 104 cerebellar-type (pilocytic) astrocytomas, 82 oligodendrogliomas, and 51 supratentorial pilocytic astrocytomas. Histological hypervascularity mimicking a vascular malformation (that is, an “angioglioma”) was encountered in 5%, 4%, and 12% of the cases, respectively. Based upon clinical, radiological, and pathological reviews of these cases, as well as a careful review of the literature, it was concluded that 1) “angiogliomas” are neither rare nor represent a distinct clinicopathological entity; 2) in histological but not necessarily angiographic surgical terms, they represent simply highly vascular gliomas, usually of low grade; and 3) the clinicopathological and angiographic features as well as the prognosis of such lesions do not differ from those of similar gliomas without angioma-like vasculature. Finally, “angiogliomas” must not be confused with gliomas of high-grade malignancy which, due to neovascularity, may be highly vascular at angiography and at surgery.
O. Wayne Houser, Burton M. Onofrio, Glenn S. Forbes and H. L. Baker Jr.
✓ Chemonucleolysis was performed in 103 patients for lumbar disc prolapse. Multiple (two) interspaces were injected in only seven patients. Radiographically, all patients had myelographic or computerized tomography evidence of disc prolapse. Eighty-seven of 100 patients who were available for follow-up review had improved. Ten of 13 patients with persistent symptoms required a laminectomy. Altered spinal alignment was evident in five of the 13 patients with persistent symptoms: retrolisthesis in three and myelographic disc defect on the convex aspect of the scoliosis in two. Review of radiographic studies was carried out in an attempt to establish guidelines for patient selection so as to decrease the rate of failure in chymopapain treatment.
Andrew Mitchell, Bernd W. Scheithauer, Patrick J. Kelly, Glenn S. Forbes and Jon E. Rosenblatt
✓ The tapeworm Spirometra mansonoides infects man worldwide, particularly in Asian countries. Rarely, the central nervous system is involved; such a case is presented here. In the total of 12 reported cases, including the case described, the worm presented clinically as a mass suspicious for neoplasm or chronic abscess cavity. Surgical removal was invariably curative in each case. Although infrequent, the possibility of tapeworm infection should be entertained in the evaluation of intracranial masses in patients who have visited exotic locales.
Daniela Lombardi, Bernd W. Scheithauer, Fredric B. Meyer, Glenn S. Forbes, Edward G. Shaw, Donna J. Gibney and Jerry A. Katzmann
✓ Twenty-one intracranial subependymomas were reviewed with regard to presentation, diagnosis, operative findings, and long-term follow-up data. The histopathological features were critically reviewed, and deoxyribunucleic acid analysis was performed by flow cytometry. The patients' mean age was 48.5 years (range 32 to 72 years). In 14 cases the tumor was located in the fourth ventricle, in six within a lateral ventricle, and in one in the third ventricle with extension into the lateral ventricle. Radiographic characteristics included isodensity with minimal enhancement on computerized tomography, frequent dystrophic calcification, and isointensity on T1-weighted or slight hyperintensity on T2-weighted magnetic resonance images. The predominant histological features in all cases were those of classic subependymoma. Nonetheless, pathological examination showed a minor (< 20%) ependymoma component in five cases, significant cytological atypia in seven, mitoses in 11, endothelial prominence in four, and focal hemorrhage-associated necrosis in two. Flow cytometry revealed a diploid pattern in 12 patients, tetraploidy in two, and aneuploidy in one.
Two patients died in the perioperative period. Of the remaining 19, 12 underwent gross total resection (two of whom received postoperative irradiation) and seven underwent subtotal resection (five of whom received irradiation). None of the 12 non-irradiated patients developed tumor progression or died of direct tumor-related causes. Of the seven irradiated patients, follow-up imaging studies demonstrated their tumors to be radioresponsive, particularly with doses of 5000 cGy or greater. Despite the presence of cytological atypia and mitotic activity in the majority of cases, the prognostic effects of such factors as tumor location and the extent of surgical resection outweighed those of the standard histopathological parameters. Routine postoperative irradiation is not recommended, but should be reserved for cases with a symptomatic residual or recurrent subependymomas following surgery.
Robert D. Brown Jr., David O. Wiebers, Glenn Forbes, W. Michael O'Fallon, David G. Piepgras, W. Richard Marsh and Robert J. Maciunas
✓ The authors conducted a long-term follow-up study of 168 patients to define the natural history of clinically unruptured intracranial arteriovenous malformations (AVM's). Charts of patients seen at the Mayo Clinic between 1974 and 1985 were reviewed. Follow-up information was obtained on 166 patients until death, surgery, or other intervention, or for at least 4 years after diagnosis (mean follow-up time 8.2 years). All available cerebral arteriograms and computerized tomography scans of the head were reviewed. Intracranial hemorrhage occurred in 31 patients (18%), due to AVM rupture in 29 and secondary to AVM or aneurysm rupture in two. The mean risk of hemorrhage was 2.2% per year, and the observed annual rates of hemorrhage increased over time. The risk of death from rupture was 29%, and 23% of survivors had significant long-term morbidity. The size of the AVM and the presence of treated or untreated hypertension were of no value in predicting rupture.
Treatment by CSF shunting and radiotherapy
Eustaquio O. Abay II, Edward R. Laws Jr., Gordon L. Grado, James E. Bruckman, Glenn S. Forbes, Manuel R. Gomez and Mark Scott
✓ Tumors of the pineal region account for 3% to 8% of pediatric intracranial tumors. The treatment of such tumors has been in a state of flux between conservative therapy (cerebrospinal fluid shunting and radiotherapy) and direct surgical removal. A brief history and review of the literature with analysis of both approaches is given, and the Mayo Clinic's experience with conservative treatment of tumors in the pineal region in patients 20 years old and younger (27 cases) is studied and analyzed. The series comprises 21 boys and six girls, with an age range of 1 to 20 years (mean 13.7 years). Follow-up examinations are complete and range from 1 to 24 years, with a mean follow-up period of 7.8 years. The median survival time for these patients treated with shunt and radiotherapy is 17.7 years. There was no mortality from treatment and complications were rare. The details of the clinical presentation, diagnostic findings, pathology, therapy, recurrence, and survival are presented.
All patients under 6 years of age (six cases) had recurrences, 50% in other areas in the brain and 50% in the spinal cord, perhaps pointing to the need for whole-brain and spinal-axis irradiation in patients in this age group. The results of this study of the conservative approach form a standard against which results of any other type of therapy may be compared.