Vascular Disorders Abstract Vascular disorders of the central nervous system encompass a variety of conditions that affect the brain and spinal cord. These conditions include ischemic and hemorrhagic stroke, aneurysms, and other neurovascular malformations such as cavernous malformations and arteriovenous malformations. Patients with vascular disorders require skillful, knowledgeable care. Nurses and the rest of the health care team should be aware of different types of vascular disorders and their associated symptoms, complications, and treatments. Keywords: aneurysm, arteriovenous malformation, carotid stenosis, cavernous malformation, ischemic cascade, reperfusion injury, stroke Vascular disorders of the central nervous system (CNS) include cerebrovascular malformations such as cavernous malformations and arteriovenous malformations (AVMs), aneurysms, and stroke. These disorders comprise a challenging set of conditions that can be life-changing for patients and their families. Patients with vascular disorders often present with a vast array of coexisting medical conditions, such as subarachnoid hemorrhage, seizures, hydrocephalus, sodium abnormalities, and cardiac and respiratory challenges. Malformations of the cerebrovascular system are believed to be embryonic anomalies. The most common types are cavernous malformations and AVMs. They can be located anywhere within the CNS. Cavernous malformations are clusters of abnormal sinusoidal vascular channels. Their characteristics include Dense fibrous tissue with little or no intervening brain parenchyma Variable size Blood in various amounts and stages of thrombus and degradation Well-circumscribed dimensions Color varying from dark red to purple Multilobulated masses described as having a “mulberry-like” appearance (▶ Fig. 8.1; ▶ Fig. 8.2) Historically, cavernous malformations were often misinterpreted as neoplastic lesions, such as hemangioblastomas, instead of malformations. They are also known as Cavernous angiomas Cavernous hemangiomas Capillary hemangiomas Cavernomas There are two types of cavernous malformations: sporadic and hereditary (familial). Multiple genes that are linked to both types of cavernous malformations have been identified. Fig. 8.1 Cavernous malformation. Both types of cavernous malformations have certain characteristics in common. These commonalities are as follows: Account for 1% of all intracranial mass lesions Account for 5 to 10% of all cerebrovascular lesions Found at autopsy or on routine imaging studies in about 0.4% of the population Hemorrhage rate is between 0.1 and 22.3% per lesion per year Hemorrhage rate for deep-seated lesions or lesions in the brainstem is higher Rehemorrhage rate is about 5% per year Found in patients of all ages but are most common between the second and fifth decades of life Most are asymptomatic Cavernous malformations usually hemorrhage in small amounts, because they are low-pressure lesions Episodes of hemorrhage may be separated by months or years For each episode, the patient may experience neurologic deficits that are worse at the onset and gradually improve as blood is reabsorbed, but the patient may never quite return to neurologic baseline Most cavernous malformations occur in the brain, but they can also occur in the spine. The breakdown of common locations is as follows: Supratentorial, 80% Infratentorial, 15% Evenly divided between the brainstem and the cerebellum Spine, 5% Symptoms associated with cavernous malformations depend on the size and location of the lesion. Patients with cavernous malformations commonly present with symptoms similar to those of patients with other neurologic disorders, including Seizure Headache Motor or sensory disturbances Cranial nerve deficits Depending on the location of the cavernous malformation, patients with hemorrhages present with varying degrees of neurologic deficits. A patient with a small frontal hemorrhage may present with subtle neurologic complaints, such as headache, whereas one with a hemorrhage in the cervical cord or brainstem may present with devastating neurologic deficits; see also Chapter 2: Assessment. Family history Recent and past medical history, including seizures Magnetic resonance imaging (MRI) is the most definitive type of imaging study (▶ Fig. 8.2) Imaging may be negative in up to 50% of MRI scans Computed tomography (CT) may show the presence and location of a lesion but does not indicate the type of lesion (i.e., cavernous malformation or tumor) Angiograms are not diagnostic, because cavernous malformations are low-flow lesions that do not image well with angiography. Fig. 8.2 Magnetic resonance image of cavernous malformation. Observation may be appropriate for patients with small cavernous malformations if the lesions are asymptomatic; however, they should undergo serial MRI scans to monitor the growth of the lesion Associated seizures may be treated with antiepileptic drugs; see also Chapter 6: Seizures The goals of surgery are to obliterate the lesion to prevent rebleeding and to manage neurologic symptoms such as seizures (Box 8.1 Hemorrhage of Cavernous Malformations and Neurologic Function). Radiosurgery is not a standard treatment for cavernous malformations. Indications for surgery include Refractory or worsening seizures Neurologic deterioration Hemorrhage or rehemorrhage Mass effect Box 8.1 Hemorrhage of Cavernous Malformations and Neurologic Function Neurologic function after hemorrhage from a cavernous malformation or postoperatively may be worse than prehemorrhage or preoperative status Improvement is expected, but it rarely returns to baseline Genetics appear to play a part in the incidence of familial cavernous malformations Autosomal dominant pattern of inheritance Familial cavernous malformations are associated with multiple lesions and a family history of seizures More prevalent in families of Mexican American heritage Serial monitoring of family members with annual MRI Genetic counseling of children and siblings of patients with familial cavernous malformations Surgical indications for single and multiple lesions are the same, but in patients with multiple lesions, the symptomatic lesion is usually surgically targeted An AVM is a mass of abnormal blood vessels in which arterial blood flows directly into the venous system through a nidus (central portion), with no intervening capillary bed (▶ Fig. 8.3). AVMs appear as tangled mass of vessels The nidus is the center or focus of the AVM Blood vessels within an AVM do not have normal characteristics AVMs do not contain normal brain tissue An AVM is a high-flow system with arterial blood flowing directly into the venous system Hemorrhage is often the first symptom of an AVM. Fig. 8.3 Arteriovenous malformation. Incidence is 3 per 100,000 persons AVMs affect male patients slightly more often than female patients AVMs account for approximately 8.6% of all cases of subarachnoid hemorrhage (SAH) AVMs can be located anywhere within the CNS Hemorrhage is frequently the first symptom This space-occupying lesion displaces normal brain tissue as it grows, so symptoms may progress slowly for slow-growing lesions Mass effect or vascular steal may cause neurologic symptoms, even if the AVM has not hemorrhaged Vascular steal occurs when rapid blood flow through the AVM draws blood away from the normal brain The rapid-onset effects of hemorrhage may cause severe neurologic compromise, coma, or death as the presenting symptom Severity of associated neurologic deficits depends on size of the hemorrhage and eloquence of the affected brain. Seizures are common Arteriovenous malformations have three important characteristics: Size Eloquence of the affected brain Presence of draining veins The Spetzler-Martin Grading Scale was created to help clinicians make decisions when treating AVMs (▶ Fig. 8.4). The presence of associated aneurysms must also be taken into account when determining treatment. The Spetzler-Martin Grading Scale assigns points for size, eloquence, and draining veins Each AVM is given a grade based on those points Lower-grade AVMs have lower morbidity; higher-grade AVMs have higher morbidity (▶ Table 8.1). Fig. 8.4 Spetzler-Martin Grading Scale. (Reproduced with permission from Spetzler RF, Martin NA. A grading system for arteriovenous malformations. J Neurosurg 1986;65:476–483, with permission from the American Association of Neurological Surgeons.) Graded feature Points Size Small (<3 cm) 1 Medium (3–6 cm) 2 Large (>6 cm) 3 Eloquence of adjacent brain Noneloquent 0 Eloquent 1 Draining veins Superficial 0 Deep 1 Source: Used with permission from Spetzler RF, Martin NA. A proposed grading system for arteriovenous malformations. J Neurosurg 1986; 65:476–483. History Imaging studies MRI is the best method for diagnosis Cerebral angiography determines the involvement of cerebral vasculature, including the presence of any associated aneurysms Treatment options include surgery, endovascular embolization, radiosurgery, and conservative treatment such as management of symptoms and observation. The best treatment can be determined using the Spetzler-Martin Grading Scale. Grades I and II: Surgical resection is the treatment of choice and should be performed at a center where large numbers of cerebrovascular procedures are routinely done Grade III: Resection, embolization, or radiosurgery, depending on analysis of the individual case (e.g., characteristics of the AVM, patient age and comorbidities, and the availability of a center where such complex procedures are routinely performed) Grades IV and V: Alternate treatments such as embolization, radiosurgery, and observation are preferred, as surgical resection of higher-grade AVMs has a relatively high morbidity and mortality, even if performed by the most experienced surgeon The goal of medical management is to treat the symptoms of the AVM This may include seizure control and pain management The goal of surgery is to occlude associated aneurysms and other high-flow areas within the AVM. It is not uncommon to treat AVMs, especially higher-grade AVMs, with more than one surgical intervention, either as a staged procedure or as surgery in conjunction with an endovascular procedure or radiosurgery. Craniotomy for resection of AVM (may also require clipping of associated aneurysms) Neuroendovascular; see also Chapter 14: Neuroradiology and Neuroendovascular Interventions Coil Embolization Gamma Knife radiosurgery; see also Chapter 16: Radiotherapy; May be used to treat surgically inaccessible lesions May be used in combination with surgery to treat large or higher-grade AVMs Arteriovenuous fistulas (AVFs) are dilated arterioles that connect directly to a vein (▶ Fig. 8.5) High-flow, high-pressure lesions Low incidence of hemorrhage Usually amenable to endovascular intervention Fig. 8.5 Arteriovenous fistula. Dural AVFs (DAVFs) are a type of AVF that is directly associated with the dura (▶ Fig. 8.6) Most AVFs are DAVFs Fig. 8.6 Dural arteriovenous fistula. Carotid cavernous fistulas are direct high-flow shunts between the internal carotid artery and the cavernous sinus Frequently occurs as a result of rupture in the cavernous portion of the internal carotid artery Most often result from trauma but may also be spontaneous Symptoms include eye pain, proptosis, and decreased visual acuity Intervention may be surgical or endovascular Capillary telangiectasias are small capillary lesions composed of clusters of vessels Most common in the pons Appear as dilated capillaries Carry little clinical significance The word aneurysm comes from the Greek aneurysma, which means widening. An aneurysm is an outpouching of an artery, often described as resembling a sac, blister, or balloon. The most common type of aneurysm is the saccular, or berry, aneurysm. Type Saccular (berry) (▶ Fig. 8.7) Has a distinctive neck Most common type of aneurysm Fusiform (▶ Fig. 8.8) A portion of the vessel wall appears to expand outward Has no defined neck Size Usually less than 10 mm Can be more than 25 mm (“giant” aneurysm) Location Anterior circulation, 85% Most anterior circulation aneurysms occur in the circle of Willis (▶ Fig. 8.9) Posterior circulation, 15% (Box 8.2 Common Locations of Aneurysms) Box 8.2 Common Locations of Aneurysms Anterior communicating artery Posterior communicating artery Middle cerebral artery Internal carotid artery Basilar tip Ophthalmic artery Fig. 8.7 Saccular aneurysm. Fig. 8.8 Fusiform aneurysm. Fig. 8.9 Common locations of aneurysms. Occurs in approximately 5% of population (Box 8.3 Risk Factors for Cerebral Aneurysms) Mean age at diagnosis is about 50 years Slightly higher female prevalence About 7 to 20% are the familial form About 10 to 20% of patients with aneurysms have more than one aneurysm Familial aneurysms are those that occur in two first- or second-degree relatives May be ruptured or unruptured Incidence is about 10% A genetic component is most likely involved Box 8.3 Risk Factors for Cerebral Aneurysms Smoking Hypertension Family history of aneurysms Age (more than 40 years) Diagnosis of connective tissue disorder Blood vessel injury (dissection) Slight female preponderance Most aneurysms do not elicit symptoms until they rupture; thus, few are found incidentally (Box 8.4 Clinical Manifestations of Aneurysms [Ruptured and Unruptured]; Video 8.1). Aneurysms may occasionally be found due to vague, subtle complaints (e.g., frequent headache, nausea and vomiting, and lethargy) Larger aneurysms may cause mass effect, with focal neurologic symptoms resulting from the pressure exerted on surrounding brain tissue Symptoms of ruptured aneurysms include Severe headache Sudden loss of function in one or more parts of the body Seizures Decreased level of consciousness (LOC) Death Box 8.4 Clinical Manifestations of Aneurysms (Ruptured and Unruptured) Unruptured aneurysms: New or unusual headache Unexplained nausea and vomiting New neurologic impairment Ruptured aneurysms: Headache with stiff neck Sudden severe neurologic impairment Sudden “worst headache of my life.” New onset seizure Numerous complications are associated with cerebral aneurysms. Blood enters the subarachnoid space after an intracerebral aneurysm has ruptured (▶ Table 8.2 and ▶ Fig. 8.10) Blood may extend into the ventricles (intraventricular hemorrhage) Amount of blood present in the subarachnoid space determines the Hunt and Hess classification scale score, discussed later Fatality rate of SAH is about 40 to 50% In the United States, 30,000 cases occur annually Hallmark complaint of patients at the time of SAH rupture is “worst headache of my life.” Fig. 8.10 Subarachnoid hemorrhage. Problem Indication Nursing action Rationale Decline in neurologic assessment Hemorrhage Perform thorough neurologic assessment, compare to baseline, and repeat at appropriate intervals Watch for signs of ICP; see also Chapter 3: Principles of Intracranial Pressure Patients with SAH are at risk for rebleeding if aneurysm is present and not clipped or coiled Check laboratory values, especially serum sodium (desired parameters for serum sodium may be higher than normal [>145 mm Hg]) Hyponatremia, usually caused by cerebral salt wasting in SAH, may facilitate cerebral edema and raise ICP Vasospasm May need cerebral angiogram to rule out vasospasm Patients with SAH are at risk for vasospasm for 3–10 days after hemorrhage Hydrocephalus May need CT of head Patients with SAH are at risk for developing hydrocephalus due to poor absorption of CSF Seizure Check laboratory values, especially drug levels, if appropriate Obtain EEG Report new abnormal changes in assessment Nonconvulsive status epilepticus may appear as a decrease in LOC Hypertension/ Triple-H therapy Be aware of desired blood pressure parameters for patient on triple-H therapy Most patients with SAH benefit from blood pressure higher than their average (MAP 20–30 mm Hg above baseline) Vasopressors, as ordered, to maintain blood pressure parameters, as ordered May require vasopressors and appropriate hemodynamic monitoring Watch for “overshoot” Potential to “overshoot” desired target Avoid hypotension at all costs Adequate blood pressure, which may be at higher levels than usual, is needed to maintain adequate CBF Hypotension puts brain at risk for inadequate CBF and further neuronal damage Hypervolemia Triple-H therapy Intravenous fluids, as ordered Strict intake and output Monitor laboratory values, especially serum sodium and osmolality Watch for signs of cardiac overload due to extra fluid Increases CBF Hemodilution Triple-H therapy Monitor laboratory values, especially complete blood count (hematocrit) Increases CBF Abbreviations: CBF, cerebral blood flow; CSF, cerebrospinal fluid; CT, computed tomography; EEG, electroencephalogram; ICP, intracranial pressure; LOC, level of consciousness; MAP, mean arterial pressure; SAH, subarachnoid hemorrhage. Occurs only in arteries and is triggered by the presence of blood in the subarachnoid space Causes arteries to constrict, restricting blood flow (▶ Fig. 8.11) May result in decreased neurologic function (Box 8.5 Clinical Manifestations of Vasospasm) Risk for vasospasm is reflected by Fisher Grading Scale score (see next section); greater amount of blood present represents higher risk for vasospasm Greatest risk of vasospasm is 4 to 14 days after SAH Accounts for about 20% of morbidity and disability in patients with SAH Detected by angiography or transcranial Doppler study Triple-H therapy is gold standard for prevention of vasospasm Hypertension Vasopressors increase mean arterial pressure to about 20 to 30 mm Hg above baseline Hemodilution Accomplished by increasing fluids Hypervolemia Increases volume by use of fluids Box 8.5 Clinical Manifestations of Vasospasm May be asymptomatic Confusion Decreased LOC Focal neurologic deficits, including aphasia and motor deficits, depending on the location of vessel in spasm May appear as stroke Fig. 8.11 Vasospasm. All ruptured aneurysms are at risk for rehemorrhage Risk increases over time Risk is highest within 24 hours of initial hemorrhage; 4 to 10% of aneurysms rebleed within 24 hours of initial hemorrhage A total of 20 to 25% rebleed within 2 weeks of initial hemorrhage Hypertension increases the risk Potentially life-threatening Likelihood of survival is reduced when aneurysms rehemorrhage Early treatment, aimed at aneurysm obliteration, is essential to prevent rehemorrhage Occurs when blood in the subarachnoid space causes poor absorption of cerebrospinal fluid (CSF) by the arachnoid granulations; see also Chapter 4: Hydrocephalus May initially require an external ventricular drain to control and monitor hydrocephalus One-third of patients with SAH will develop hydrocephalus Most patients with hydrocephalus will require a permanent shunt Occur in about 20 to 40% of patients with SAH May be temporary Treated with antiepileptic drugs; see also Chapter 6: Seizures Hyponatremia occurs when the amount of sodium in blood is too low (Box 8.6 Hyponatremia in Subarachnoid Hemorrhage). See also Chapter 5: Electrolyte Disturbances. Cerebral salt wasting Most commonly seen in patients with SAH Occurs when levels of natriuretic peptide are increased, resulting in leakage of salt and water from the body Depletes fluid and sodium stores in the body Treatment is administration of sodium (oral or intravenous [IV]) Syndrome of inappropriate antidiuretic hormone Caused by oversecretion of antidiuretic hormone Results in dilution of sodium in blood Treatment is fluid restriction Box 8.6 Hyponatremia in Subarachnoid Hemorrhage Confusion, lethargy, or seizure may be the sign of hyponatremia Monitor serum sodium level Monitor intake and output, as well as which IV fluids are running, if any Report sodium level of less than 135 mg/L or desired parameter Patients with hyponatremia are at risk for seizures Cerebral salt wasting is more common than syndrome of inappropriate antidiuretic hormone; see also Chapter 5: Electrolyte Disorders Occurs in about 5% of patients with SAH May present as transient disturbance on electrocardiogram (ECG), life-threatening arrhythmia, or myocardial infarction Mechanism of cardiac stunning is unclear History Lumbar puncture to determine the presence of SAH Imaging studies CT or MRI will reveal a large aneurysm or SAH Cerebral angiogram is gold standard to determine the exact artery on which the aneurysm is located and whether the aneurysm is ruptured or unruptured (▶ Fig. 8.12 and ▶ Fig. 8.13). Fig. 8.12 Unruptured aneurysm. Arrow indicates base of aneurysm where it arises from the V4 segment of the vertebral artery. Fig. 8.13 Ruptured aneurysm (arrow) within a focus of subarachnoid hemorrhage.
8.1 Vascular Disorders
8.2 Cerebrovascular Malformations
8.2.1 Cavernous Malformations
Epidemiology of Cavernous Malformations
Location of Cavernous Malformations
Clinical Manifestations of Cavernous Malformations
Diagnosis of Cavernous Malformations
History
Imaging Studies
Treatment of Cavernous Malformations
Medical
Surgical
Familial Cavernous Malformations
Treatment
8.2.2 Arteriovenous Malformations
Epidemiology of Arteriovenous Malformations
Clinical Manifestations of Arteriovenous Malformations
Classification of Arteriovenous Malformations
Spetzler-Martin Grading Scale
Diagnosis of Arteriovenous Malformations
Treatment of Arteriovenous Malformations
Medical
Surgical
8.2.3 Other Vascular Malformations
Arteriovenous Fistulas
Dural Arteriovenous Fistulas
Carotid Cavernous Fistulas
Capillary Telangiectasias
8.3 Intracerebral Aneurysms
8.3.1 Classification of Aneurysms
8.3.2 Epidemiology of Aneurysms
8.3.3 Clinical Manifestations of Aneurysms
8.3.4 Common Complications of Aneurysms
Subarachnoid Hemorrhage
hypotension
Vasospasm
Rehemorrhage
Hydrocephalus
Seizures
Hyponatremia
Cardiac Stunning
8.3.5 Diagnosis of Aneurysm and Subarachnoid Hemorrhage
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