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Werner Hassler, Armin Thron and Ernst H. Grote

✓ Local hemodynamics were investigated during nine operations for spinal dural arteriovenous (AV) fistulas. In eight cases, microvascular Doppler sonography was used to measure flow velocities and vasomotor reactivity to CO2 changes. Intravascular pressure recordings of the draining veins on the medullary surface were performed in nine cases. The flow velocities in dural AV fistula feeding vessels were not as high as has been shown in cerebral angioma feeders. The AV fistula feeders often showed low end-diastolic flow velocities as a sign of increased vascular resistance, even in the presence of a downstream AV fistula, thus proving disturbance of venous outflow from the spinal canal. After excision of the fistula, the circulation of the spinal cord vessels improved, with higher inflow and outflow velocities. In the veins formerly draining the fistula, no further flow could be recorded; however, they did not collapse, indicating that some pressure remained. The mean venous pressure in the dural AV fistulas was about 74% of the systemic arterial pressure. It increased concomitantly with the arterial pressure, which may explain the clinical deterioration that occurs during physical activity. Fistulas with a high shunt volume on angiography showed only moderately increased venous pressures and a more pronounced pressure drop compared to low-volume fistulas. The CO2 reactivity of vessels supplying the spinal cord could be demonstrated in all cases, and was normal before and after removal of the fistula.

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Ruth Thiex, Armin Thron, Joachim M. Gilsbach and Veit Rohde

Object. Because of the rarity of spinal subdural hematomas (SDHs), the literature offers scarce estimates of the outcome and predictive factors in patients suffering from these lesions. In addition, single-institution surgical series are still lacking. Therefore, the authors retrospectively evaluated the early and long-term functional outcomes measured in eight patients with spontaneous and nonspontaneous spinal SDHs in whom the clot had been evacuated.

Methods. The patients' charts were evaluated for origin of the lesion, risk factors, and neurological deficits at symptom onset and at 28 days after extirpation of the spinal SDH. Long-term clinical outcome (Barthel Index [BI]) was evaluated by administering a telephone questionnaire to the patient or a relative.

Only one patient with a spontaneous spinal SDH was identified. Four patients were undergoing anticoagulant therapy, and three patients had undergone a previous anesthetic/diagnostic spinal procedure. Twenty-eight days postoperatively, neurological deficits improved in six of eight patients; however, in two of the six patients, the improvement did not allow the patients to become independent again. In two patients, surgery did not affect the complete sensorimotor deficits. In the long-term survivors (median 45 months) a median BI of 55 was achieved. The latency between symptom onset and surgery did not correlate with functional outcome in this series. The preoperative neurological condition and location of the hematoma correlated positively with early and long-term functional outcome.

Conclusions. To the best of their knowledge, the present study is the largest single-institutional study of patients with surgically treated spinal SDHs. Despite some postoperative improvement of sensorimotor deficits in most patients, the prognosis is poor because 50% of the patients remain dependent. Their outcome was determined by the preoperative sensorimotor function and spinal level of the spinal SDH.

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Uwe Spetzger, Jürgen Reul, Joachim Weis, Helmut Bertalanffy, Armin Thron and Joachim M. Gilsbach

✓ The authors present a detailed account of the microsurgical production of bifurcation aneurysms in chinchilla rabbits for basic studies of endovascular coil embolization of aneurysms. End-to-side anastomoses of both common carotid arteries (CCAs) were performed, and a venous pouch was fitted into the newly created bifurcation. These experimental aneurysms closely mimic human cerebral aneurysms in size and hemodynamic features. Sixty-three animals underwent operation. Fifteen animals died in the course of the experiment and 15 were excluded because of a CCA occlusion within the carotid bifurcation. Electrical detachable platinum coils, also known as Guglielmi detachable coils (GDCs), and tungsten mechanical detachable coils (MDCs) were used for the endovascular occlusion of 26 bifurcation aneurysms (16 rabbits were treated with GDCs and 10 with MDCs). Initially, complete angiographic obliteration (95%–100% occlusion of the aneurysm) was achieved in nine rabbits and incomplete obliteration (< 95% occlusion) was seen in 17 animals. Final angiography 3 to 6 months later demonstrated complete occlusion in only four and partial occlusion in 22 aneurysms. At present, the histopathological examination of 17 embolized aneurysms has revealed incomplete obliteration of all aneurysms, even in those three cases that were thought to be completely embolized according to angiographic criteria. A general overestimation of the radiological degree of aneurysm obliteration was found.

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Timo Krings, Marcus H. T. Reinges, Ruth Thiex, Joachim M. Gilsbach and Armin Thron

Object. During neurosurgical interventions, preservation of subcortical axons is as important as preservation of cortical neurons. The goal of this study was to assess the combined use of functional (f) and diffusion-weighted (DW) magnetic resonance (MR) imaging to assist in the preservation of the structure and function of the motor system.

Methods. The authors evaluated the combination of fMR imaging and DW MR imaging to detect cortical motor areas with their corresponding pyramidal tracts in 12 healthy volunteers and in 10 consecutive patients with various space-occupying lesions affecting the central motor system.

Activation within the primary motor cortex (M1) and white matter bundles originating from this cortical region was demonstrated in 21 of the 22 individuals examined. Additional activation was exhibited along the course of white matter tracts at the level of the pons and, in the contralateral hemisphere, in the M1. Fiber tract displacement was visualized in all patients in white matter that had appeared normal on routine T1- and T2-weighted MR images.

Conclusions. The combination of DW MR and fMR imaging allows visualization of the origin, direction, and functionality of large white matter tracts. This will prove helpful for imaging structural connectivity within the brain during functional imaging. Moreover, local relationships of cerebral tumors that encroach upon M1 and subcortical fiber tracts can be defined. This promises to decrease patient morbidity and to broaden the clinical applications of functional imaging.

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Magnetic resonance imaging of spinal meningiomas and neurinomas

Improvement of imaging by paramagnetic contrast enhancement

Gerhard Schroth, Armin Thron, Lothar Guhl, Karsten Voigt, Hans-Peter Niendorf and Luis Rios-Nogales Garces

The detection and delineation of spinal tumors by magnetic resonance imaging (MRI) after intravenous administration of gadolinium (Gd)-diethylenetriaminepenta-acetic acid (DTPA) is demonstrated in eight cases of neurinoma or meningioma. The advantages of Gd-DTPA-enhanced MRI over other MRI techniques used in more than 100 cases of spinal cord diseases are described.

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Azize Boström, Timo Krings, Franz J. Hans, Johannes Schramm, Armin K. Thron and Joachim M. Gilsbach

Object

Glomus-type spinal arteriovenous malformations (AVMs) are rare. In the literature only small series and anecdotal reports can be found, and there are no prospective series elucidating the natural course or the superiority of 1 treatment regimen over another (such as surgery versus embolization versus conservative treatment). Microsurgical treatment of spinal AVMs often seems difficult because many lesions are not anatomically suitable for primary microsurgical occlusion and are therefore treated with first-line neuroradiological interventions or not at all.

Methods

Between 1989 and 2005, 20 patients with glomus-type AVMs underwent microsurgical treatment at 2 major neurosurgical centers in Germany. The history of symptoms in these patients ranged from 2 days to 11 years. Four patients presented with subarachnoid hemorrhage, 2 with intramedullary hematoma, 4 with paresthesia or pain, and 10 with clinical signs of myelopathy. Seven patients underwent partial embolization prior to microsurgery. The authors only operated on AVMs accessible from a dorsal or dorsolateral approach. Neurological status was assessed with the McCormick classification scheme. Follow-up data were obtained from outpatient records. Three patients were interviewed over the telephone and 4 patients were not available for follow-up evaluation.

Results

Surgery was performed via a laminectomy in 14 and hemilaminectomy in 6 patients. The microsurgical technique used consisted of retrograde dissection of the AVM from the venous side in most cases. Four (20%) of 20 patients showed worsening of neurological symptoms to a worse McCormick grade, probably caused by suspected venous stasis directly after surgery, however only 1 patient (5%) suffered permanent deterioration after surgery. In 14 patients postoperative angiography proved complete occlusion in 11 patients, including the presence of a remnant requiring a second operation with complete occlusion thereafter in 1 patient. In 3 patients occlusion was incomplete: a small residual AVM remained in 1 patient, and a discrete feeding vessel without a vein was evident in 2 patients.

Conclusions

Spinal cord AVMs are rare. If embolization is not possible, surgery may be indicated in selected cases. Spinal AVMs behave differently after incomplete occlusion either surgically or with embolization. A postoperative reduction in symptoms is frequent despite the presence of small remnants, and the risk of neurological deficits seems relatively low even in residual AVMs. Therefore, treatment need not necessarily aim at complete occlusion if that would be associated with an unacceptably high risk of neurological deficits.

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Timo Krings, Volker A. Coenen, Martin Weinzierl, Marcus H. T. Reinges, Michael Mull, Armin Thron and Veit Rohde

✓ Among spinal cord vascular malformations, dural arteriovenous fistulas (DAVFs) must be distinguished from intradural malformations. The concurrence of both is extremely rare. The authors report the case of a 35-year-old man who suffered from progressive myelopathy and who harbored both a DAVF and an intradural perimedullary fistula. During surgery, both fistulas were identified, confirmed, and subsequently obliterated. The fistulas were located at two levels directly adjacent to each other. Although the incidence of concurrent spinal DAVFs is presumed to be approximately 2%, the combination of a dural and an intradural fistula is exceedingly rare; only two other cases have been reported in the literature. One can speculate whether the alteration in venous drainage caused by the (presumably congenital) perimedullary fistula could possibly promote the production of a second dural fistula due to elevated pressure with concomitant venous stagnation and subsequent thrombosis. The authors conclude that despite the rarity of dual pathological entities, the clinician should be aware of the possibility of the concurrence of more than one spinal fistula in the same patient.

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Spinal epidural arteriovenous fistula with perimedullary drainage

Case report and pathomechanical considerations

Timo Krings, Michael Mull, Azize Bostroem, Juergen Otto, Franz J. Hans and Armin Thron

✓ The classic angiographically demonstrated features of spinal dural arteriovenous fistulas are shunts of radiculomeningeal branches with radicular veins draining exclusively in the direction of perimedullary veins and thereby causing venous congestion. These shunts are located at the point where the radicular vein passes the dura mater. Spinal epidural arteriovenous shunts, however, normally do not drain into the perimedullary veins and are, therefore, asymptomatic, presumably because of a postulated reflux-impeding mechanism between the dural sleeves. The authors report on a patient in whom an epidural arteriovenous shunt showed delayed retrograde drainage into perimedullary veins, leading to the classic clinical (and magnetic resonance imaging–based) findings of venous congestion. Intraoperatively the angiographically established diagnosis was confirmed. Coagulation of both the epidural shunt zone and the radicular vein resulted in complete obliteration of the fistula, as confirmed on repeated angiography.

This rare type of fistula should stimulate considerations on the role of valvelike mechanisms normally impeding retrograde flow from the epidural plexus to perimedullary veins and suggest that, in certain pathological circumstances, epidural fistulas can drain retrogradely into perimedullary veins as an infrequent variant of spinal arteriovenous shunts.