Intracranial aneurysm size [Neurosurgery Wiki]

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====== Intracranial aneurysm size ======
[[Very small intracranial aneurysm]] (< 3 mm)

[[Small intracranial aneurysm]] (< 5 and ≥ 3 mm)

Normal sized [[intracranial aneurysm]] (5 and < 12 mm)

[[Large intracranial aneurysm]] (12-25 mm)

[[Giant intracranial aneurysm]] (> 25 mm).
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Maximal [[size]] and other morphological [[parameter]]s of [[intracranial aneurysm]]s (IAs) are used when deciding if an IA should be treated prophylactically. These parameters are derived from postrupture [[morphology]]. As time and [[rupture]] may alter the [[aneurysm geometry]], possible morphological predictors of a rupture should be established in prerupture aneurysms.

Twelve IAs that later ruptured were matched 1:2 with 24 control IAs that remained [[unruptured]] during a median follow-up time of 4.5 (interquartile range, 3.7-8.2) yr. Morphological parameters were automatically measured on 3-dimensional [[model]]s constructed from [[angiogram]]s obtained at time of [[diagnosis]]. Cases and controls were matched by [[aneurysm location]] and [[aneurysm size]], patient [[age]] and [[sex]], and the [[PHASES score]] (population, hypertension, age, size of aneurysm, earlier subarachnoid hemorrhage from another aneurysm, and site of aneurysm) did not differ between the 2 groups.

Only [[inflow angle]] was significantly different in cases vs controls in [[univariate analysis]] (P = .045), and remained significant in [[multivariable]] analysis. Maximal size correlated with size ratio in both cases and controls (P = .015 and <.001, respectively). However, maximal size and inflow angle were correlated in cases but not in controls (P = .004. and .87, respectively).

A straighter inflow angle may predispose an aneurysm to changes that further increase risk of rupture. Traditional parameters of aneurysm morphology may be of limited value in predicting IA rupture
((Skodvin TØ, Evju Ø, Sorteberg A, Isaksen JG. Prerupture Intracranial Aneurysm 
Morphology in Predicting Risk of Rupture: A Matched Case-Control Study.
Neurosurgery. 2019 Jan 1;84(1):132-140. doi: 10.1093/neuros/nyy010. PubMed PMID: 
29529238.
)).
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For a given [[geometry]], Cebral et al. 
((Cebral JR, Castro MA, Appanaboyina S, Putman CM, Millan D, Frangi AF. Efficient pipeline for image-based patient-specific analysis of cerebral aneurysm hemodynamics: Technique and sensitivity. IEEE Trans Med Imaging. 2005;24:457–467.)) 
showed that [[intracranial aneurysm hemodynamics]] do not vary significantly with physiological variations of [[flow rate]], [[blood pressure]], and [[waveform]]. Therefore, suitable parameters characterizing IA [[geometry]] can capture the characteristic hemodynamics and potentially predict [[rupture risk]]. 

The most ubiquitous parameter is IA size. Although aneurysms exceeding 10 mm in size are considered to be dangerous, several studies have shown that a large percentage of ruptured aneurysms are, in fact, smaller than 10 mm
((Beck J, Rohde S, el Beltagy M, Zimmermann M, Berkefeld J, Seifert V, Raabe A. Difference in configuration of ruptured and unruptured intracranial aneurysms determined by biplanar digital subtraction angiography. Acta Neurochir (Wien) 2003;145:861–865.))
((Forget TR, Jr, Benitez R, Veznedaroglu E, Sharan A, Mitchell W, Silva M, Rosenwasser RH. A review of size and location of ruptured intracranial aneurysms. Neurosurgery. 2001;49:1322–1326.))
((Raghavan ML, Ma B, Harbaugh RE. Quantified aneurysm shape and rupture risk. J Neurosurg. 2005;102:355–362.))
((Rinkel GJ, Djibuti M, Algra A, van Gijn J. Prevalence and risk of rupture of intracranial aneurysms: A systematic review. Stroke. 1998;29:251–256.))
((Ujiie H, Tachibana H, Hiramatsu O, Hazel AL, Matsumoto T, Ogasawara Y, Nakajima H, Hori T, Takakura K, Kajiya F. Effects of size and shape (aspect ratio) on the hemodynamics of saccular aneurysms: A possible index for surgical treatment of intracranial aneurysms. Neurosurgery. 1999;45:119–130.))
((Ujiie H, Tamano Y, Sasaki K, Hori T. Is the aspect ratio a reliable index for predicting the rupture of a saccular aneurysm? Neurosurgery. 2001;48:495–503.))
((Weir B, Disney L, Karrison T. Sizes of ruptured and unruptured aneurysms in relation to their sites and the ages of patients. J Neurosurg. 2002;96:64–70.)).