The Posterior Approach to a Series of Glomus (Type II) Intramedullary Spinal Cord Arteriovenous Malformations

OBJECTIVE: Intramedullary spinal cord arteriovenous malformations (AVMs) are comprised of those AVMs which in either glomus or nidal form are found partially or entirely within the substance of the spinal cord. An effort to subdivide these lesions into either glomus Type II or juvenile Type III spinal cord AVMs has underscored the diffuse, unresectable nature of the latter but has done little to suggest a logical management paradigm for the more well-defined, low-flow glomus lesion. METHODS: To address this shortcoming, 15 cases of glomus Type II spinal AVMs were identified from a larger series of a variety of spinal AVMs. Computed tomography, magnetic resonance imaging, and superselective angiography rendered the anatomic diagnosis of these lesions accurate in all cases. All lesions were approached posteriorly via a standard laminectomy, with the goal of total extirpation, and all patients underwent immediate postoperative angiography to verify cure. In the vast majority of cases, patients underwent follow-up imaging to confirm the durability of this cure, and long-term outcome was determined using both a subjective quality of life assay and a functional grading scale. Age, sex, mode of presentation, and radiographic features were subsequently analyzed with respect to functional outcome. RESULTS: Most glomus spinal AVMs presented with a rapid cascade of signs and symptoms (73%), often caused by subarachnoid hemorrhage (60%j and often leading to significant neurological deficits (47%). Initially, 14 of 15 patients (94%) were angiographically cured of their malformations. The remaining patient was neurologically improved after a 90% resection, and follow-up angiography demonstrated that the residual was thrombosed. However, not uncommonly, follow-up angiography and magnetic resonance imaging revealed recurrences, with three of the patients who underwent delayed imaging (23%) demonstrating new draining veins. Fortunately, in each case, the recurrence was asymptomatic. Therefore, the long-term cure rate (mean follow-up, 8.5 yr; range, 1-17 yr) was 80%, with no subsequent bleeding or progression of symptoms. Outcomes were generally good, with six patients (40%) demonstrating objective improvement, eight (53%) being neurologically stable, and one (7%) being worse. Sixty-six percent were independent, 20% required moderate assistance, and 14% remained entirely dependent. There were no deaths. Patients possessing lesions with large direct feeders off the anterior spinal artery and occupying a primarily anterior position in the cord fared somewhat worse, as did those with rapidly progressing symptomatology in the absence of subarachnoid hemorrhage. However, even in those with preserved or improved function, chronic pain was a significant problem, affecting one-third of all patients. Chronic pain was especially common in young women who had presented with significant preoperative pain that responded poorly to all subsequent therapeutic manipulations. CONCLUSION: With careful evaluation of high-quality superselective angiography and the judicious use of preoperative embolization, posterior surgical approaches can deliver results comparable with those achieved for other benign intramedullary lesions in terms of long-term cure (80%), control of symptom progression (100%), and good functional outcome (86%). Despite these results, chronic dysesthetic pain syndromes are not uncommon and continue to present a significant management problem.