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Unruptured middle cerebral artery aneurysm


Neurosurgery Department, University General Hospital of Alicante, Foundation for the Promotion of Health and Biomedical Research in the Valencian Region (FISABIO), Alicante, Spain

Unruptured middle cerebral artery aneurysm are regularly treated by both microsurgical clipping and endovascular coiling.


Kumar et al. subclassified into 5 types based on the similarities in their morphological features which influenced the techniques of clipping as recorded from their preoperative 3D CTA and intraoperative view. These types and the distinctive feature of each type are described. The various techniques of clipping are discussed based on these subgroups. The groups outlined make possible the establishment of a common technical approach to clipping within the groups. This classification, based on preoperative 3D CTA and intraoperative morphological features of the aneurysm and parent vessels, helps in the intraoperative choice of technique and type of clip application to tackle these lesions

I simple weak aneurysmal wall, well-circumscribed to the site of maximum hemodynamic stress, no extension to M1 proximally

II central type weak aneurysmal wall extending on to the M1 proximally

III complicated neck branch at the neck of the aneurysm

IV complex M2 seen to be arising from the aneurysm rather than M1

V blister aneurysms 1).



For a systematic metaanalysis to compare the safety and efficacy of these two methods, literature was reviewed for all studies reporting angiographic occlusion and/or functional outcomes in adults with unruptured MCAA treated by endovascular coiling or microsurgical clipping. All studies that reported results for adults (≥ 18 years) with unruptured MCAA, from 1990-2011 in English were considered for inclusion.

Twenty-six studies involving 2295 aneurysms undergoing clipping or coiling for unruptured MCA aneurysms were included for analysis. There were 1530 aneurysms which were treated with clipping, and 765 aneurysms treated with coiling. Pooled analysis revealed failure of aneurysmal occlusion in 3.0% (1.2-7.4% 95% CI) of clipped cases. Pooled analysis of 15 studies (606 aneurysms) involving coiling and occlusion revealed lack of occlusion rates of 47.7% (43.6-51.8% 95% CI) with the fixed-effects model and 48.2% (39.0-57.4% 95% CI) with the random-effects model. Thirteen studies examined neurological outcomes after clipping and were pooled for analysis. Both fixed- and random-effect models revealed unfavourable outcomes in 2.1% (1.3-3.3% 95% CI) of patients. There were 17 studies evaluating potential unfavourable neurological outcomes after coiling that were pooled for analysis. Fixed- and random-effect models revealed unfavourable outcomes in 6.5% (4.5-9.3% 95% CI) and 4.9% (3.0-8.1% 95% CI) of patients respectively.

Based upon this systematic review and meta-analysis of unruptured MCAA, after careful consideration of patient, aneurysmal, and treatment center factors, Smith et al. recommend surgical clipping for unruptured MCAA 2).


A systematic review was conducted to determine morbidity of the procedure by performing a meta-analysis of the literature. The authors used a PubMed and J-stage search from 2000 to 2011 for studies containing the surgical clipping of the unruptured MCA AN. There were 21 articles, containing a total 1,323 cases of unruptured AN with morbidity specifically located in the MCA. 54 cases indicated significant neurological deficits for a morbidity rate of 4.1% (95% CI; 3.0-5.1). A limited number of studies disclosed an incremental increase in morbidity with the size of the aneurysm. Smaller MCA AN (7±3 mm) presented a lower morbidity of 1.48%, whereas giant MCA AN (>25 mm) corresponded with a higher morbidity of 27.8%. Factors consistently associated with high morbidity included incorporated MCA branches, plaque at the neck of the AN, an unclippable configuration, and M1 superior wall AN. Complex aneurysms required a wide array of intracranial bypass procedures, yielding morbidity of 23.4% (95% CI; 20.9-25.9). This is the first systematic review and quantitative meta-analysis of the surgical complications related to unruptured MCA AN 3).

Case series


411 patients with single unruptured MCA aneurysms treated with simple microsurgical clipping were enrolled. Patients were divided into two groups based on the application of somatosensory evoked potential (SSEP) monitoring during surgery.

The Ischemic complications (ICs) rate was 0.9% and 5.6% in the SSEP and non-SSEP groups, respectively. Univariate analysis revealed that age≥62.5years, aneurysm size≥4.15mm, temporary clipping, history of hyperlipidemia and stroke, and no-SSEP monitoring were risk factors for ICs. Multivariate logistic regression analysis showed that age≥62.5years (odds ratio [OR]=7.7; 95% confidence interval [95% CI]=1.5-37.7; P=0.011), previous stroke (OR=26.8, 95% CI=2.4-289.2, P=0.007), and inversely SSEP monitoring (OR=0.14, 95% CI 0.02-0.72, P=0.019) were independent risk factors for ICs.

Clinicians should consider the possibility of IC during microsurgical clipping of unruptured MCA aneurysms in patient ≥ 62.5years and/or a history of stroke. Intraoperative SSEP monitoring is an effective and feasible tool for preventing IC 4).

Fifty unruptured middle cerebral artery aneurysms were analyzed. Spatial and temporal maximum pressure (Pmax) areas were determined with a fluid-flow formula under pulsatile blood flow conditions. Intraoperatively, thin walled regions (TWRs) of aneurysm domes were identified as reddish areas relative to the healthy normal middle cerebral arteries; 5 neurosurgeons evaluated and divided these regions according to Pmax area and TWR correspondence. Pressure difference (PD) was defined as the degree of pressure elevation on the aneurysmal wall at Pmax and was calculated by subtracting the average pressure from the Pmax and dividing by the dynamic pressure at the aneurysm inlet side for normalization.

In 41 of the 50 cases (82.0%), the Pmax areas and TWRs corresponded. PD values were significantly higher in the correspondence group than in the noncorrespondence group (P = .008). A receiver-operating characteristic curve demonstrated that PD accurately predicted TWRs at Pmax areas (area under the curve, 0.764; 95% confidence interval, 0.574-0.955; cutoff value, 0.607; sensitivity, 66.7%; specificity, 82.9%).

A high PD may be a key parameter for predicting TWRs in unruptured cerebral aneurysms 5).


416 patients treated between March 2003 and February 2014. All patients met the following criteria: 1) microsurgical clipping of an unruptured MCA bifurcation aneurysm was performed, and 2) clinical and radiographic follow-up data were available including preoperative digital subtraction angiography. The incidence of and risk factors for procedure-related complications were retrospectively evaluated.

Procedure-related complications occurred in 15 (3.6%) patients, including asymptomatic complications in 10 (2.4%) patients and symptomatic complications in 5 (1.2%) patients. Multivariate logistic regression analysis showed that posteroinferior projection of the aneurysm (odds ratio = 2.814, 95% confidence interval = 0.995-6.471, P = 0.042), distance between the internal carotid artery bifurcation and the MCA bifurcation (Dt) in a linear line (odds ratio = 1.813, 95% confidence interval = 0.808-6.173, P = 0.043), and horizontal angle between the vertical line to the base of the skull and Dt (odds ratio = 2.046, 95% confidence interval = 1.048-10.822, P = 0.048) were independent risk factors for procedure-related complications.

When performing clipping of unruptured MCA bifurcation aneurysms, the procedure-related complication rate was 3.6%. Patients with MCA bifurcation aneurysms with posteroinferior projection, shorter Dt, and larger horizontal angle may be at a higher risk of procedure-related complications when performing microsurgical clipping 6).


Clinical and radiological data of 103 patients interdisciplinary treated for unruptured MCA aneurysms over a 5-year period were analyzed in endovascular (n = 16) and microsurgical (n = 87) cohorts. Overall morbidity (Glasgow Outcome Score <5) after 12-month follow-up was 9 %. There was no significant difference between the two cohorts. Complete or “near complete” aneurysm occlusion was achieved in 97 and 75 % in the microsurgical, respective endovascular cohort. A “complex” aneurysm configuration had a significant impact on complete aneurysm occlusion in both cohorts, however, not on clinical outcome. Treatment of unruptured MCA aneurysms can be performed with a low risk of repair using both approaches. However, the risk for incomplete occlusion was higher for the endovascular approach in this series 7).


Individualized surgical simulation using three-dimensional (3D) imaging to allow safe performance of clipping surgery for unruptured middle cerebral artery (MCA) aneurysm via pterional keyhole mini-craniotomy was performed in 100 consecutive patients.

3D images were reconstructed of the skin, skull, cerebral arteries and veins, and aneurysm. The size, shape, and location of the scheduled keyhole and the patient's head position were individually optimized using this preoperative simulation system. The site of opening of the sylvian fissure was also preoperatively determined according to the spatial relationships between the aneurysm and sylvian veins. 110 pterional keyhole clipping surgeries were consecutively performed in 100 patients.

The mean diameter of the pterional keyhole was 25±2 mm. Magnetic resonance imaging detected lacunar infarction in 4 cases (3.6%) but no other abnormalities. 1 patient suffered a reversible ischemic neurological deficit and 1 patient (79 years old) showed mild dementia. The modified Rankin scale at 3 months after the operation was grade 0 in all cases except 1 patient with mild dementia (grade 1). Mini-mental state examination, Hamilton rating scale for depression, and Beck depression inventory were all significantly improved (p<0.01) after the operations.

Pterional keyhole clipping surgery based on careful surgical simulation with 3D images is a safe and less invasive means to treat relatively small unruptured MCA aneurysms 8).

Case reports


Spontaneous complete thrombosis of an unruptured intracranial aneurysm leading to ischemic stroke is rare. Fomenko et al., present a case of a 56-year-old man who suffered an acute left middle cerebral artery (MCA) infarction, attributable to complete thrombosis of an unruptured saccular MCA bifurcation aneurysm with occlusion of the parent artery. The presenting hemiparesis and aphasia partially improved over a long hospital rehabilitation stay. Follow-up imaging demonstrated no recanalization of the aneurysm or parent vessels. This is the first documented case of isolated MCA territory infarction due to complete spontaneous thrombosis of a saccular aneurysm 9).


A 82-year-old female with no neurological deficits underwent a clipping for a giant middle cerebral artery (MCA) aneurysm. Immediately after surgery, she presented with hemichorea-hemiballismus (HC-HB) on the left side. Postoperative angiograms and single-photon emission computed tomography demonstrated the hyperperfusion in the right frontal cortex and the decreased perfusion in the basal ganglia, indicating that the abrupt hemodynamic changes due to the obliteration of the giant aneurysm caused the dysfunction of the frontal cortical and subcortical pathway and the basal ganglia. Administration of tiapride hydrochloride was dramatically effective in controlling the HC-HB until the hyperperfusion resolved. Single-photon emission computed tomography obtained 8 weeks after surgery revealed that the cerebral blood flow had been normalized in the right frontal cortex. The relative hypoperfusion of the right basal ganglia was also resolved. Then tiapride hydrochloride was discontinued without a relapse of HC-HB.

This case appears consistent with the theory that the connecting fibers responsible for the development of HC-HB are also located in the frontal lobe. The treatment of giant aneurysms involving the M1 portion can cause abrupt hemodynamic changes in both frontal cortex and the basal ganglia, which can potentially induce postoperative movement disorders 10).


A 69-year-old woman undergoing elective stent-assisted coiling of an unruptured right middle cerebral artery (MCA) bifurcation aneurysm, who was found to have severe attenuation of somatosensory evoked potential (SSEP) and electroencephalography (EEG) during the procedure. Intra-operative DynaCT showed hypodense cortical vessels consistent with cerebral air embolism 11).


Progressive visual field defect caused by an unruptured middle cerebral artery aneurysm 12)


Kim et al. present a rare case of delayed symptomatic thromboembolism in an ischemic stroke patient who had undergone coil embolization for unruptured middle cerebral artery (MCA) aneurysm 13).

A 22-year-old female patient presented to the Emergency Department of a tertiary care hospital with symptoms of headache and nausea. She has been on a regular follow-up for the preceding three and a half years after being diagnosed as systemic lupus erythematosus (SLE). She had been treated earlier for SLE nephritis in the same institution, and had two relapses of nephrotic syndrome in the last three and a half years for which she had been treated and had achieved complete remission. All possibilities of headaches in background of SLE were considered. CNS examination was inconclusive. There was no nuchal rigidity or no cranial nerve deficits. Fundoscopy and Plain CT scan of brain were normal. The possibility of CNS-lupus was considered considering the high values of antiphospholipid antibodies (APLA). Treatment was initiated accordingly; however, there was no improvement in her symptoms. Although being rare in a patient with SLE, the possibility of an aneurysm was considered. Four vessel digital substraction angiography revealed two unruptured aneurysms of 7.2 mm and 3.9 mm in the left middle cerebral artery (MCA) territory. Craniotomy and aneurysmal clipping was done successfully, and the patient was relieved of her symptoms. A high degree of suspicion towards a rarer cause clinched the diagnosis of a left MCA territory stem artery aneurysm. This rationale of strong suspicion and discussion of differential diagnosis brought a change in the management of the patient 14).


A case with unruptured MCA aneurysm associated with DMCA and a dolichoectasic anterior cerebral artery. In this case, surgical intervention was not prioritized because of the narrowed and calcified parent artery of the aneurysm. In selecting treatment for a patient with multiple vascular anomalies, the pathophysiology of each anomaly should be estimated carefully 15).


A 73-year-old man with an unruptured aneurysm of the left middle cerebral artery. The initial sign was complex partial seizures. A standard scalp electroencephalogram was normal while neuropsychological tests revealed a slight deficit of episodic memory. Brain MRI showed an aneurysm at the left middle cerebral artery bifurcation. Cerebral angiography confirmed the presence of a saccular aneurysm at the left middle cerebral artery bifurcation, with a maximum diameter of 12 mm. This case had two main characteristic features: seizures had a quite late onset and were the only symptom the patient experienced 16).

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unruptured_middle_cerebral_artery_aneurysm.txt · Last modified: 2017/06/15 00:34 by administrador