Prospective, population-based detection of intracranial vascular malformations in adults: the Scottish Intracranial Vascular Malformation Study (SIVMS).

BACKGROUND AND PURPOSE: Intracranial vascular malformations (IVMs) are an important cause of intracranial hemorrhage, epilepsy, and long-term disability in adults. There are no published prospective, population-based studies dedicated to the detection of any type of IVM (cavernous malformations, venous malformations, and arteriovenous malformations [AVMs] of the brain or dura). Therefore, we established the Scottish Intracranial Vascular Malformation Study (SIVMS) to monitor detection and long-term prognosis of people with IVMs. METHODS: We used multiple overlapping sources of case ascertainment to identify adults (aged >or=16 years) with a first-ever-in-a-lifetime diagnosis of any type of IVM made between January 1, 1999, and December 31, 2000, while resident in Scotland (mid-1999 adult population estimate 4,110,956). RESULTS: Of 418 notifications to SIVMS, 190 adults (45%) were included, 181 (95%) of whom were deemed to harbor a definite IVM after review of diagnostic brain imaging and/or reports of autopsy/surgical excision pathology. The crude detection rate (per 100,000 adults per year) was 2.27 (95% CI, 1.96 to 2.62) for all IVMs, 1.12 (95% CI, 0.90 to 1.37) for brain AVMs, 0.56 (95% CI, 0.41 to 0.75) for cavernous malformations, 0.43 (95% CI, 0.31 to 0.61) for venous malformations, and 0.16 (95% CI, 0.08 to 0.27) for dural AVMs. CONCLUSIONS: In addition to providing data on the public health importance and comparative epidemiology of IVMs, continuing recruitment and follow-up of this prospective, population-based cohort will provide estimates of IVM prognosis.

Scottish Intracranial Vascular Malformation Study (SIVMS): evaluation of methods, ICD-10 coding, and potential sources of bias in a prospective, population-based cohort.

BACKGROUND AND PURPOSE: The rarity of intracranial vascular malformations (IVMs) and the infrequency of their outcomes make large, prolonged cohort studies the best means to evaluate their frequency and prognosis. METHODS: The Scottish Intracranial Vascular Malformation Study (SIVMS) is a prototype prospective, population-based study of adults resident in Scotland and diagnosed for the first time with an IVM after January 1, 1999. We evaluated the design of SIVMS using 2 complete years of data for adults with arteriovenous malformations (AVMs) of the brain. RESULTS: A collaborative network of clinicians, radiologists, and pathologists, combined with coding of hospital discharge data and death certificates, recruited a cohort distributed in proportion to the Scottish population. Coding (with International Classification of Diseases, 10th Revision [ICD-10] codes Q28.2 and I60.8) had a sensitivity of 72% (95% CI, 61% to 80%) and a positive predictive value of 46% (95% CI, 38% to 55%) for detecting incident brain AVMs. Adults who were detected by coding alone were significantly (P<0.05) younger, more likely to present with hemorrhage, more frequently investigated with catheter angiography, and more likely to be treated. Adults recruited from tertiary referral centers were significantly more likely to be investigated with catheter angiography and to be treated. Using catheter angiography as a diagnostic requirement for brain AVMs significantly biases the cohort toward younger adults presenting with hemorrhage and receiving treatment. CONCLUSIONS: Population-based studies of IVM frequency and prognosis should use multiple overlapping sources of case ascertainment, and such studies of brain AVMs should not require catheter angiography to be the diagnostic standard.