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David Bervini, Michael Kerin Morgan, Marcus Andrew Stoodley and Gillian Ziona Heller

OBJECTIVE

The occurrence of transdural arterial recruitment (TDAR) in association with brain arteriovenous malformation (bAVM) is uncommon, and the reason for TDAR is not understood. The aim of this cohort study was to examine patient and bAVM characteristics associated with TDAR and the implications of TDAR on management.

METHODS

A prospective surgical database of bAVMs was examined. Cases previously treated elsewhere or incompletely examined by digital subtraction angiography (DSA) assessment were excluded. Three studies of this cohort were performed, as follows: characteristics associated with TDAR, the relationship between TDAR and neurological deficits unassociated with hemorrhage (NDUH), and the impact of TDAR on outcome from surgery. Regression models were performed.

RESULTS

Of 769 patients with complete DSA who had no previous treatment, 51 (6.6%) were found to have TDAR. The presence of TDAR was associated with increasing age (p < 0.01; OR 1.05; 95% CI 1.02–1.07); presentation with NDUH (p < 0.01; OR 2.71; 95% CI 1.29–5.71); increasing size of the bAVM (p < 0.01; OR 1.57; 95% CI 1.29–1.91); and combined supply from both anterior and posterior circulations (p = 0.02; OR 2.37; 95% CI 1.17–4.78). Further analysis of TDAR cases comparing those with and without NDUH found an association of larger size (6.6 cm [2.9 SD] compared with 4.7 cm [1.8 SD]; p < 0.01) and combined supply from both anterior and posterior circulations (relative risk 2.5; 95% CI 1.0–6.2; p = 0.04) to be associated with an NDUH presentation.

For the 632 patients undergoing surgery there was an increased risk of complications (where this produced a new permanent neurological deficit at 12 months represented by a modified Rankin Scale score of > 1) with the following variables: size; location in eloquent brain; deep venous drainage; increasing age; and no presentation with hemorrhage. The presence of TDAR was not associated with an increased risk of complications from surgery.

CONCLUSIONS

The authors found that TDAR occurs in older patients with larger bAVMs, and that TDAR is also more likely to be associated with bAVMs presenting with NDUH. The likely explanation for the presence of TDAR is a secondary recruitment arising as a consequence of shear stress, rather than a primary vascular supply present from the earliest development of the bAVM.

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Marcus Stoodley, R. Loch Macdonald, Bryce Weir, Linda S. Marton, Lydia Johns, Zhen Du Zhang and Andrew Kowalczuk

Object. It is not known whether the factors responsible for vasospasm after subarachnoid hemorrhage (SAH) cause the cerebral arteries to be narrowed independent of the subarachnoid blood clot or whether the continued presence of clot is required for the entire time of vasospasm. The authors undertook the present study to investigate this issue.

Methods. To distinguish between these possibilities, bilateral SAH was induced in monkeys. The diameters of the monkeys' cerebral arteries were measured on angiograms obtained on Days 0 (the day of SAH), 1, 3, 5, 7, and 9. The subarachnoid blood clot was removed surgically on Day 1, 3, or 5 or, in control animals, was not removed until the animals were killed on Day 7 or 9. The concentrations of hemoglobins and adenosine triphosphate (ATP), substances believed to cause vasospasm, were measured in the removed clots and the contractile activity of the clots was measured in monkey basilar arteries in vitro. If the clot was removed 1 or 3 days after placement, vasospasm was significantly diminished 4 days after clot removal. Clot removal on Day 5 had no marked effect on vasospasm. There was a significant decrease over time in hemoglobin and ATP concentrations and in the contractile activity of the clots, although substantial hemoglobin and contractile activity was still present on Day 7.

Conclusions. The authors infer from these results that vasospasm requires the presence of subarachnoid blood for at least 3 days, whereas by Day 5 vasospasm is less dependent on subarachnoid blood clot. Because the clot still contains substantial amounts of hemoglobin and contractile activity after 5 days, there may be an adaptive response in the cerebral arteries that allows them to relax in the presence of the stimulus that earlier caused contraction.

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Michael Kerin Morgan, Marcus Andrew Stoodley and John William Fuller