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Are localized abnormal dilation in cerebral arteries. It is usually located in the emergency zones of the branches of major arteries and especially during his tour of the cisternal subarachnoid space.
It is still the exact etiology discussion because there are factors that suggest etiology acquired while others support the genetic theory as in case of the occurrence of aneurysms in connective tissue diseases and cases of aneurysms in relatives.
Intracranial aneurysms are in relatively frequently autopsies, but to date are diagnosed mainly occur when broken and subarachnoid hemorrhage.
In these circumstances may result in death of 10 to 15% of people before receiving medical care (1), and the mortality rate at 30 days is 46% (2).
In autopsy series reported an average prevalence of 5% (3). By angiographic studies in volunteers found that 6.5% of people have aneurysms (4), but the frequency of aneurysms that rupture is much lower.
The presence of cerebral aneurysm and rupture phenomenon increases with age, especially between the fourth and seventh decade of life. In rare cases of aneurysms that occur in childhood: 2% (33).
The congenital theory considers that the basic cause of the formation of an aneurysm is the discontinuity of the smooth muscle layer of the tunica media of the arteries, especially in a branch. As there is less resistance in these outbreaks would occur over time and sacculation greater arterial degeneration.
The fact that there are families in intracranial aneurysms in identical twins and in patients with genetically determined as polycystic kidney disease, Marfan syndrome, Ehlers-Danlos syndrome type IV or pseudoxanthoma elasticum, a group suggests a genetic factor in origin (5).
The alternative theory proposes that the aneurysm formed is predominantly the result of degenerative changes in the arterial wall and that are acquired with age and sometimes arterial hypertension (6, 7). This can be seen intimal proliferation, degeneration of the elastic and atherosclerotic changes.
At present it is considered that aneurysms arise as a result of congenital deficiency of the muscular layer of the cerebral arteries, which is added in postnatal stages histological changes degenerative arterial wall, which include fragmentation of the internal elastic layer, apparently related to hemodynamic stress phenomenon.
Intracranial aneurysms can be classified according to different factors. -So:
According to its etiological to:
- Saccular aneurysms, which constitute 80 to 90%, and are located in the emergence of branches of the main vessels when run through the cisternal space. They have a sector that is the neck of the aneurysm and the other is the bottom (Figure 1).
- Or atherosclerotic fusiform aneurysms (Figure 2), which do not occur in output branches but undertake a whole segment of the blood vessel wall as primary intracranial carotid, vertebral artery or basilar. It aso
CIA frequently atherosclerosis and hypertension. Most frequently cause compression tables on cranial nerves, on the other vessels or brain parenchyma.
- Infectious aneurysms or "mycotic". This terminology is considered to injuries or rarely bacterial emboli fungal (8). He was found at a frequency of 4% (1) and is associated with subacute bacterial endocarditis, or in immunocompromised patients, or individuals who use drugs. Tend to be of distal movement, more frequently in distal branches of the middle cerebral artery (Figure 3 c) and more often multiple.
- Traumatic aneurysms are considered with a frequency less than 1%. Usually pseudoaneurysms is because its structure is part of cerebral tissue (9). They are associated with penetrating skull trauma (stab intended projectile or gun), but can also be seen in closed head injury. The latter is more common and can cause injury proximal main vessel as the carotid artery in petrous or cavernous or may occur in arteries distal cortical trauma suffered by depressed skull fracture.
According to their size (29):
- Small: less than 6 mm
- Medium: 6-15 mm
- Large: 16-25 mm
- Giant: over 25 mm
Saccular aneurysms are more common in the carotid system (85-95%) and the most common are:
a) internal carotid artery, the output level of the posterior communicating artery
b) anterior cerebral artery connecting region with anterior communicating artery
c) bifurcation or trifurcation of the middle cerebral artery
d) carotid bifurcation dea
Vertebrobasilar system aneurysms are present in 5-15% of cases (Figure 5a-c).
They are located most often in the basilar bifurcation or distal third, and in the emergence of the posterior inferior cerebellar artery (PICA) from the vertebral artery.
In 101 consecutive patients cerebral aneurysms, served for a year in the Department of Neurosurgery Hospital Edgardo Rebagliati Martins National Social Health Insurance Lima-Peru, we found a total of 144 aneurysms. Of these, 111 (90.97%) were located in the carotid system 13 (9.03%) in the vertebrobasilar.
The most common location was at the level of the internal carotid artery junction with posterior communicating artery, 35 aneurysms of a total of 144 (26.3%).
Multiple aneurysms were found in 20 patients (19.8%).
The association of aneurysm (s) and arteriovenous malformation was seen in 10 patients (9.9%).
The frequency location of aneurysms as is shown in Figure 6.
In 15-33% of cases of multiple aneurysms are HSA, considering any cases of patients with two or more lesions (17).
4. Natural history of brain aneurysms
Unruptured brain aneurysm, asymptomatic
These lesions can be diagnosed in two situations. An aneurysm is found in a patient who has never had HSA and fortuitous discovery was to investigate a nonspecific symptom with any diagnostic procedure or, in cases of suspected aneurysm screening by family.
Another situation occurs when fortuitously show arterial aneurysms addition tree aneurysm has ruptured.
In these circumstances it has been shown by studies of Jane (18) that the annual breakage rate is 1% and the risk significantly dependent on the size of the aneurysm. The more than 10 mm in size are most at risk.
Figure 6. Diagram showing the localization of aneurysms 101 consecutive patients with SAH cerebral aneurysm(peri-od February 98 Jan 99 HNERM).
-NÂ ° of patients with multiple aneurysms:20.
-° In patients with aneurysms asociacióon association MAV:10(9.9%)
Symptomatic cerebral aneurysms, not broken
In monitoring by angiography of patients with cerebral aneurysm has been shown that most increases in size over time (19, 20). They may cause compression of neighboring neural structures. Así, aneurysms in the intracavernous segment of the carotid artery can produce a picture of installing insidious pain and dysesthesia in area by compressing the trigeminal cranial nerve V and diplopia for its effect on compression or distortion III, IV o VI jitters cranial.
In cases of aneurysms of the ophthalmic segment of the internal carotid artery (between the ceiling of the cavernous sinus and out of the posterior communicating artery can occur disorder of visual field due to rejection of the optic nerve against the falciform ligament, withdrawal of dura covering the upper face of the optic nerve at the channel, o incluso, if the aneurysm projecting medially on sella, to produce such a chiasmatic syndrome caused by a pituitary tumor (Figure 7 a-b).
Aneurysms of the posterior communicating artery is especially directed backwards and because of the proximity to the oculomotor nerve (III), when compressed it, may occur dependent paresis or paralysis of the nerve muscles, ptosis Palpebral y midriasis.
The event of aneurysm rupture and SAH is therefore an absolutely negative and devastating situation for a patient. It is considered that despite the advances in care in intensive care units (UCI) and advances in surgery and endovascular treatment, almost half of patients die within two months after the stroke (10). Half of the deaths occur as a result of the initial hemorrhage. Among the survivors are good results in the 40%, because many suffer residual neurological morbidity or neuropsychological (11).
Aneurysms occur when breaking Bleeding subaracnoidea or intracerebral hemorrhage dominance. The weakest sector of the aneurysmal wall is the background, and if the location of the aneurysm is entirely cisternal, subarachnoid bleeding will, which is the most common, but if the bottom is inside the brain parenchyma, be intracerebral bleeding, or even intraventricular.
Aneurysms of the anterior cerebral artery junction with anterior communicating, hematoma frequently originates at the base of the frontal lobe (Figura 8a-b) and the middle cerebral artery aneurysms (ACM) internal carotid or do to the temporal lobe (Figura 9a-b).
Aneurysms of the vertebrobasilar system, especially PICA, to invade the fourth ventricle bleeding-ass and, secondarily, other ventricles (Figura 10a-b).
5. Complications postruptura aneurysmal
It is the most dramatic and critical event post HSA. The mortality is greater than postresangrado 70% (21). The peak of rebleeding is in primerras 24-48 hours.
The closure of the aneurysm to prevent rebleeding and surgery sooner becomes greater the potential reduction during the high risk period.
If surgery is performed there is an incidence of approximately. 20% possibility of rebleeding in the first 2 weeks (22).
Antifibrinolytic therapy reduces the rate of rebleeding but is associated with increased complications from ischemic neurological deficit (31).
It is the leading cause of disability after SAH. Generally, ischemic deficit vasospasm develops between the 12th and 5.Â ° ° day after the initial hemorrhage. The peak is 7.mo I gave-a (23). Although the incidence of angiographic vasospasm is 60-70%, The incidence of neurologic-related symptoms is approximately vasospasm 30% (24) (Figure 11).
The surgery performed before this stage allows to remove blood from the tanks and therefore reduce spasmogenic substances, also be used to hypertensive hypervolemic therapy if signs of ischemia occur postoperatively.
It can be acute obstruction of the ventricular system by extravasated blood or occur later and in an insidious manner by disorder in CSF absorption. It looks at a frequency of 15 a 21% (1, 32).
Figura 7a. Paraclinoideo aneurysm of left internal carotid artery location intrasupraselar. The symptoms presented by the patient was progressive vision deficits.
While axial computed tomographic (TAC) is the highest value for the diagnosis of HSA, cerebral angiography so far is the method of choice for identifying brain aneurysms and vascular malformations. It is considered the definitive technique for surgical planning of these lesions (30).
Angiography should be initiated by the side of suspected vascular injury is based on the clinical and brain CT.
Overall angiography should be both carotid arteries and two vertebral. With this diagnosis of multiple aneurysms or arteriovenous malformation association with also described is achieved.
This study should analyze the morpho-logical characteristics of the lesion, size and direction of the aneurysm, relationship with pot afferent, vessels of periferie (especially perforating), neck size. All these data will serve for surgical planning.
It should also be sectorial if there is evidence of vascular spasm or diffuse, luminal defects likely atherosclerotic plaques and collateral circulation via the circle of Willis.
The risks of angiography are low but should be considered. Stroke include, aneurysm rebleeding, hematoma formation in the area PSANS puncture, reaction to contrast material and renal failure. The mortality rate for the exam is 0,1% and the rate of permanent neurological deficit is 0,5% (25).
The angiografí-a for resonance nuclear magnética (JG) or magnetic resonance angiography is an effective method for obtaining diagnostic and vascular morphological and physiological information of high resolution. At the present moment is a noninvasive alternative, virtually risk, High specificity and sensitivity for diagnosis of vascular malformations, cerebral aneurysms (34).
S able to show aneurysms 2-3 mm in diameter, but prospective studies have found that the critical size is 5 mm (26).
b. The method of endovascular aneurysm occlusion therapy with platinum filaments lumen (coils), constitutes an alternative treatment for selected patients.
8. QUIRI TREATMENT?RGICO
There are two positions on the time that surgery should be performed, so that some level of controversy still remains.
One is to surger- "early" it is performed before the 48-72 Subarachnoid hours posthemorragia.
The other is to surger- "Deferred" o tardía , usually made from the 10 a 14 días post HSA.
The reasons behind early surgery or "early" its:
a. If the surger-a is successful, eliminates the risk of rebleeding in a group of patients who have this complication statistically.
b. Once the surgery is much easier to treat vasospasm that occurs in a percentage of patients post HSA, especially after 6 a 8 I gave-as happened the HSA.
c. Washing allows basal cisterns with clot removal, achieving better circulation of cerebrospinal fluid and a decreased risk of hydrocephalus (27).
d. Although the greater surgical mortality, shows that there is a lower mortality in the overall care of patients in whom surgery was performed early (28).
The questioning of early surgery are mainly by the following factors:
- The surgery is performed on more difficult technical conditions for intracranial hypertension, cerebral edema, friable parenchyma and dense clots in tanks. There is increased risk of edema and generate increased parenchymal contusion after surgery.
- There is greater possibility of postoperative vasospasm.
- The risk of intraoperative aneurysm rupture is greater.
Due to these factors, currently managing patients better oriented post clinical conditions HSA (grados To The Hunt II & Hess) and no complex aneurysms, to perform in them-a surger "early".
Delayed surgery is reserved for patients in levels III, IV y V de Hunt & Hess, those with poor systemic medical conditions, complex aneurysm carriers, Giant vertebrobasilar system or, those showing signs of large cerebral edema in the presence of CT or angiographic vasospasm important.
9. GENERAL TREATMENT OF QUIRI?RGICO
The patient enters the operating room under effect of premedication with mild sedation and anticholinergic effect. The anesthesiologist placed under monitoring of cardiovascular parameters in blood pressure, heart rate, electrocardiographic, arterial oxygen and carbon dioxide. If you put the saw-central venous.
Thumbnail radial arterial route preference and invasive blood pressure monitoring. At all times sudden changes in blood pressure to be avoided especially in the moment of intubation and placement cranial fixation system.
Administer antibiotic prophylaxis (can be Cefazolin 2 gr I.V.)
Anesthetic induction prior oxygenation. Administration of sodium pentobarbital in increments of progressive 50 a 150 mg hasta 1 gr total. Once the patient asleep, anesthetic agents will be administered by mask. Before intubation muscle relaxant is administered.
Intubation should be very smooth. Keep controlled ventilation mode with approx figures PCO2. 30 mmHg.
During Reconstruction Surgery-a, anesthesiologist be administered at the time that the craniotomy is performed at a dose of mannitol 20% of 0.5 g / kilo / dosis, in order to obtain complete relaxation of the cerebral parenchyma before dural opening.
In some circumstances it is useful to have a spinal catheter to vent opening prior LCR dural, especially in those cases where seen in the cerebral blood occluded by TAC cisterns. In most patients it is enough that the surgeon removes LCR cisterns supported by
Relaxation of brain parenchyma that provides technical tesiológica anes-. Ultimately can be performed if evacuation ventricular puncture CSF is ineffective.
The attitude of the anesthesiologist should be to maintain communication with the surgeon. Especially blood pressure control at critical times such as neck dissection or aneurysm sac should be taken into account, These circumstances in which it is preferable to have a state of controlled hypotension Mean arterial pressure (PAM) of 60 mmHg. In case of abrupt rupture aneurismática, MAP will have to go down to figures 20 a 25 mmHg por 2 a 3 minutes, if it is insufficient temporary clipping the afferent vessel.
10. They?TECHNICAL QUIRI?RGICA
Neuroanestesiológicas modern techniques aim to reduce the stress the brain parenchyma while maintaining adequate perfusion pressure while allowing the surgeon exposure and dissection of the aneurysm in the safest way.
Aneurysm surgery should aim to minimize brain damage at the time of dissection and exposure microquirúgica aneurysm and especially ensure total vasopermeability, not only the afferent vessels to injury, but also small perforators are in the periphery.
Position of patient
Most aneurysms surgeries are performed in supine position. This position is the physiological from the point of view of cardiovascular and cerebral perfusion.
Must discreetly raised his head 15 to 20's to enhance venous drainage.
In case of aneurysms of the vertebral artery may be in position laterally oblique (position park bench) or very occasionally seated.
The head position varies according to the location of the aneurysm to operate (Figure 13).
Cranial most frequently used approaches are: Pterional of Yasargil, allowing expose the entire anterior circle of Willis. Should be supplemented with adequate removal of the lesser wing of the sphenoid, in order to realize the least shrinkage of the cerebral parenchyma. Are useful in communicating artery aneurysms previous, internal carotid artery bifurcation, sector proximal middle cerebral artery and basilar bifurcation aneurysms high position.
Frontotemporal craniotomy comprehensive gives more exposure to distal middle cerebral artery aneurysms.
The coronal craniotomy is mainly for aneurysms of the pericallosal artery (portion A2, A3).
The craniotomy-a temporary Drake, extension to the middle fossa floor, allows subtemporal approach to aneurysms of the basilar artery tip.
The suboccipital craniotomy with removal of the arch of C1 allows adequate exposure of vertebral artery aneurysms.
The combined subtemporal craniectomy suboccipital craniotomy + petrosectomí the partial-, allows a better approach to aneurysms of the distal third of the basilar artery.
Opening tanks is performed with support of the surgical microscope. CSF is removed from tank carotid-dea, chiasmatic, Sylvian fissure and opens wide.
If paraclinoid aneurysms should be performed exeresis the anterior clinoid apophyses, the posterior third of the roof of the orbit and optic canal (Figure 14). This allows for maximum exposure of the optic nerve in its course by optical channel and to better expose carotidooftálmicos aneurysms (Figure 15).
In case of aneurysms of the anterior communicating artery is convenient to carry corticectomía of gyrus rectus.
For aneurysms of internal carotid artery bifurcation corticectomía discrete front lid can be performed in the most proximal portion of the Sylvan fissure, taking care not to injure the perforating arteries.
Exposure of the aneurysm
Dissecting aneurysm neck is the most critical time of surgery. Coagulated and sectioned shall arachnoid adhesions and properly dissected afferent vessels.
The placement of the clip should be very accurate, trying to see how far cross enter at least one branch of the clip. If there is resistance must withdraw the clip, as it can be counterpart aneurysm sac and it can be drilled. Additional dissection must be carried out to reposition the clip and.
Figura 14b. Right internal carotid angiogram showing the giant AP incidence aneurysmal lesion seen in Figure 14a.
After placing the clip should be reviewed if the clipping was right and if it is not compressed to the main vessel or one of its branches. Revise even perforating vessels (Figure 16).
If in doubt regarding the proper clipping sac incision and suction recommended content (Figures 17 and 18). Of active bleeding occur should be amended to add additional clipping or clip.
In case of breakdown intraoperatoria, if small, should be placed on one area cotonoid bleeding and vacuum. Generally subsides bleeding and dissection may be resumed.
If bleeding should be sought much volume the afferent vessel and perform temporary clipping of the same, quickly dissecting aneurysm and cliparlo.
If tear proximal aneurysmal neck sector, no option to use Sugita or Yasargil clips, consider Sundt clips or Slim Kees Kees.
Check the condition of the vessels. If postoperative vasospasm can be placed local papaverine solution or Nimodipine.
Leave pieces of Surgicel in cortisectomía area and ensure hemostasis neatly. Cierre the Views', Bone replacement platelet, fragments can be left hemostatic sponge (Gelfoam) epidural level. Closing muscle, galea and skin.
If considered taking into account the patient's neurological conditions prior, that has a high probability of maintaining a Glasgow Coma Scale of less than 8 points, or if the patient has also developed obstructive hydrocephalus, it is preferable to leave a measurement system intracranial pressure for better handling of the same, intermittent withdrawal of CSF and pulsed administration of Mannitol, according to the degree of intracranial hypertension.
Keep light state of hypervolemia. Central venous pressure must be maintained 10 cm water.
Administer medication against him vasoespasmo with intravenous Nimodi-pin for the SNG.
Always maintain mean arterial pressure 90-95 mmHg. Hypotension Avoid the risk of ischemia and irreversible brain injury.
Steroids, Antacid, H2 blockers.
Mantener profilaxis with antibiotic Cefazolin 1 gr each 8 hours 24 a 48 additional hours.
11. THERAPY endovascular
They represent a wide range of innovative therapeutic strategies that target occlusion or exclusion of a cerebral aneurysm through the intraarterial route.
These techniques include the following:
- Participation in internal aneurysm of small metallic filaments: Guglielmi coils and mechanical detachable coils (12)
- Thumbnail minibalones (13)
- Balloon occlusion of the proximal artery in cases of giant aneurysms (14)
- Placing microstent (Covers) intraarterial occlusion for lateral aneurysms (31, 35).
The technique that is offering the best results is the occlusion of the aneurysm with platinum filaments (coils). Aneurysms are most appropriate pedicle.
The current indications for endovascular therapy are referred to cases of aneurysms presenting an excessive surgical difficulty; in cases of instability or neurologic cases with high risk systemic (36).
Aneurysms with excessive surgical difficulty are the trunk of the bifurcation of the basilar artery, Aneurysms of the vertebro basilar junction, aneurysms of the anterior inferior cerebellar artery emergency and aneurysms in the intracavernous carotid artery segment.
Neurological cases include patients instability in degrees 4-5 Ratings Hunt & Hess, with increased pressure intracaneal, or patients with symptomatic vasospasm deterioration.
The high systemic risk include patients with aneurysmal rupture also have box hemodynamic instability, are. respiratory distress, hipoxemia, coagulopatí treatment-as, sepsis, cardiac ischemia, liver failure, renal failure or other multisystem.
The advantage of this technique is that it requires prolonged deep anesthesia, craneotomía, brain retraction. Anyway procedures are not without limitations as aneurysms incompletely occluded especially the wide-necked or giant (Complete closure is obtained in less than 40% case) (15), recanalization of the aneurysm due to remodeling of the material used (16% case) (16), or complications inherent to the procedure.
Embolization with balls is equally encouraging results with preservation of afferent vessel in cases of aneurysms do not have fresh clots and is being achieved because there are better diagnostic techniques as MRI, best fluoroscopic equipment to, development of new types of balloons and microcatheters. But it is necessary that these techniques are centralized in specialized centers to develop the most in the future this therapeutic alternative.
Advantages of surgical clipping
- Known durability of treatment. Known durability of treatment.
- This may be another pathological to present.
- Parenchyma decompresses: Removal
hematoma, L.C.R. the cerebral tejido.
- Blood is removed subarachnoid.
- If woe the anatomí th: main vessel, art. collaterals and perforating.
- If intraoperative contralateral Sangrado.
- A rapidly evolving technolo-.
- Others: Neuroprotection, anesthesia, exposures of the skull base.
Disadvantages of surger-a
- In cases of high-grade patients waiting period for surgery exposes patients to a rebleeding.
- Injury direct vessels piercing.
- The temporary occlusion can be risky in segment perforating.
- Brain Shrinkage (difficult and can cause problems in patients with high grade).
- Many exposures require significant retraction (A.Com.ant, apex tronco basilar).
- Spe-cific surgeon: learning curve, experience, training.
Benefits of Therapy Coil
- Possibility of treating poor-grade patients.
- Under anesthesia time.
- It can treat multiple aneurysms in different vascular territories.
- Very acceptable risk of complications.
- Can be combined with angioplastí-a..
- It may be only palliative (obliterate the area rota).
- Technolo-a rapidly developing and mejorí-a.
Disadvantages of therapy Coil
- Durability of treatment not yet known.
- During the procedure can lead to complications (the injury hemorrhagic stroke the vasoespasmo).
- Recurrence can be high in certain types of aneurysm.
- Increased risk of thromboembolic complications.
- Substantial risk of need for retreatment.
- More expensive than surger-whether requires repeated.
- Potential need for anticoagulation.
- Spe-cific endovascular therapist: learning curve, experience, training.
What treatment to choose: the surgery, the endovascular therapy
To date there are no randomized studies comparing surgery and endovascular therapy with coils.
Should thus advantages and disadvantages of each treatment modality be considered (draw 1 and 2), the clinical condition of the patient and the anatomical features of the aneurysm to choose one or the other therapy.
b. Aneurysm (*) exposed to the surger-, arises from the anterior aspect of the carotid artery.
Because the surgical treatment of cerebral aneurysms has evolved over decades as a way of becoming highly effective and safe therapy and current endovascular therapy techniques have limitations, particularly in treating large aneurysms or wide neck those, the current generation of endovascular techniques can not be considered as a replacement to existing surgical methods.
Endovascular techniques should be considered complementary to surgical techniques should also be seen as an option to extend the treatment to patients with inoperable aneurysms or high surgical risk (Figure 19).
With the availability of both treatments â??microsurgical high quality and endovascularâ?? for treating aneurysms, may expect better results in future clinical, superior to those achieved with one of the methods performed in isolation (37, 38).