Introduction and historical background 27 with MRA.454 In the mean follow-up period of six years (range 4.5 – 12.9 years), recanalization was found in 11 aneurysms (2.5%), three of which were retreated. Treatment of the other eight aneurysms was not performed due to the recanalization being too small, co-morbidity, unfavorable morphology or because the patient refused retreatment. Independent predictors for late reopening were found to be aneurysm size greater than 10 mm (OR 4.7; 95% CI, 1.3–16.3), and location of aneurysm on basilar tip (OR 3.9; 95% CI, 1.1–14.6). This confirms findings of other studies in which an aneurysm size of more than 10 mm was found to be a strong predictor of aneurysm recurrence.393,447 In order to assess the rate of late recanalization in the subgroup of patients from our own hospital we performed a sub analysis on the LOTUS data from this group. The results of the patient subgroup analysis from the Maastricht University Medical Centre are described in Chapter 7: Late reopening of adequately coiled intracranial aneurysms. Apart from the risk of rebleed of treated aneurysms, the risk of a bleed from de novo aneurysms or from already existing additional aneurysms elsewhere necessitates monitoring of patients with treated intracranial aneurysms.455,456 These patients are thought to have a higher risk of new aneurysm formation,455 although a recent study from Sprengers et al showed most de novo aneurysms to be very small and not requiring treatment.457 In a literature review, Ferns et al found an annual incidence of de novo aneurysm formation between 0.3 and 1.8%.458 In their cohort of 276 patients they found two de novo aneurysms at five year follow-up after treatment of another aneurysm, or a cumulative five-year incidence of 0.75%. Regrowth of additional aneurysms, identified at the time of treatment of the index aneurysm, had a cumulative five-year incidence of 7.9% (five of 63 previously known but untreated aneurysms were seen to have grown at the five-years follow-up). In their literature review Ferns et al. reported annual risk of growth of additional aneurysms to be ranging from 1.5 to 22.7%. The annual incidence of SAH from unruptured aneurysms is low, ranging from 0.6 to 1.3%.24,459 Results of long-term follow-up data from the ISAT study suggest an annual rupture rate from de novo and known additional aneurysms in patients with a coiled aneurysm of 0.036% each323 and an older study found an incidence of rupture of de novo aneurysms to be 0.06% per patient-year in patients with a clipped aneurysm.460 Ferns et al concluded that: ‘the risk of de novo aneurysm formation and significant enlargement of additional untreated aneurysms is low, with a subsequent extremely low risk of subarachnoid hemorrhage from these aneurysms …. especially in the first five years.’ And: ‘screening of all patients within the first five years after aneurysm treatment does not seem beneficial in terms of preventing subarachnoid hemorrhage or for detection of aneurysms that need treatment’.458 However, even if long term follow-up has a low yield in terms of hemorrhage prevention or aneurysm detection, it is advisable if disadvantages are minimal. Disadvantages in terms of side effects or complications have been reduced since MRA has become the accepted modality for follow-up, but other aspects, like psychology and finance, have hardly been investigated. One study did assess the impact of long term follow-up with MRA on mood and anxiety of the patient and concluded that, even though long term follow-up did not induce a temporary major increase in anxiety or depression at the time of follow-up,
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