Neurovascular and neurodegenerative disorders

Neurovascular disorders impair cerebral blood flow and may cause permanent physical deficits. Examples of neurovascular disorders include cerebral aneurysm and stroke. Neurodegenerative disorders are neurologic disorders that cause progressive deterioration of cerebral and motor function. Alzheimer’s disease, Creutzfeldt-Jakob disease, Huntington’s disease, multiple sclerosis, and Parkinson’s disease are neurodegenerative disorders.

NEUROVASCULAR DISORDERS

CEREBRAL ANEURYSM

Cerebral aneurysm is a localized dilation of a cerebral artery that results from a weakness in the arterial wall. The most common form is the saccular (berry) aneurysm, a saclike outpouching in a cerebral artery. (See Comparing types of aneurysms.) Cerebral aneurysms commonly rupture, causing subarachnoid hemorrhage.

Most cerebral aneurysms occur at bifurcations of major arteries in the circle of Willis and its branches. An aneurysm can produce neurologic symptoms by exerting pressure on the surrounding structures such as the cranial nerves. (See Common sites of cerebral aneurysm, page 268.)

Cerebral aneurysm results from a congenital defect of the vessel wall, head trauma, hypertensive vascular disease, advancing
age, infection, or atherosclerosis, which can weaken the vessel wall. Cerebral aneurysm is more common in women than in men; however, the opposite is true in children and adolescents, with a male to female ratio of 2:1. Additionally, cerebral aneurysm rupture is most prevalent in the 35- to 60-year-old age-group, with 50 being the mean age of occurrence.

COMPARING TYPES OF ANEURYSMS

Saccular (berry) aneurysm

Most common type
Secondary to congenital weakness of media
Usually occurs at major vessel bifurcations
Occurs at the circle of Willis
Has a neck or stem
Has a sac that may be partly filled with a blood clot

Giant aneurysm

Similar to saccular aneurysm, but larger-3 cm or more in diameter
Behaves like a space-occupying lesion, producing cerebral tissue compression and cranial nerve damage
Associated with hypertension

Fusiform (spindleshaped) aneurysm

Occurs with atherosclerotic disease
Characterized by irregular vessel dilation
Develops on internal carotid or basilar arteries
Rarely ruptures
Produces brain and cranial nerve compression or cerebrospinal fluid obstruction

Dissecting aneurysm

Caused by arteriosclerosis, head injury, syphilis, or trauma during angiography
Develops when blood is forced between layers of arterial walls, stripping intima from the underlying muscle layer

Traumatic aneurysm

Develops in the carotid system
Associated with fractures and intimal damage
May thrombose spontaneously

Charcot-Bouchard aneurysm

Microscopic
Associated with hypertension
Involves basal ganglia or brain stem

Mycotic (infectious) aneurysm

Rare
Associated with septic emboli that occur secondary to bacterial endocarditis
Develops when emboli lodge in arterial lumen, causing arteritis and weakening and dilation of arterial wall

The prognosis is usually guarded, but it depends on the patient’s age and neurologic condition, presence of other diseases, and the extent and location of the aneurysm. About half the patients who suffer subarachnoid hemorrhages die immediately. However, with new and better treatment, the prognosis is improving.

Pathophysiology

Blood flow exerts pressure against a congenitally weak arterial wall, stretching it like an overblown balloon and making it likely to rupture. Such a rupture is followed by a subarachnoid hemorrhage, in which blood spills into the space normally occupied by cerebrospinal fluid (CSF). Sometimes blood spills
into the brain tissue, where a large clot can cause potentially fatal increased intracranial pressure (ICP) and brain tissue damage.

Complications

Rupture
Subarachnoid hemorrhage
Brain tissue infarction
Cerebral vasospasm
Death
Rebleeding
Hydrocephalus

Assessment findings

Most cerebral aneurysms produce no symptoms until rupture occurs and include the following:

sudden onset of an unusually severe headache
nausea and vomiting
altered level of consciousness (LOC)
history of a period of activity, such as exercise, labor and delivery, or sexual intercourse, before the rupture.

Other findings vary with the location of the aneurysm and the extent and severity of hemorrhage and may include:

pain above or behind an eye
possible photophobia
nuchal rigidity
back and leg pain
fever
restlessness and irritability
seizures
blurred vision
ptosis and vision disturbances (aneurysm adjacent to the oculomotor nerve)
hemiparesis, unilateral sensory deficits, dysphagia, vision deficits, and altered LOC (bleeding into the brain tissue).

COMPLICATIONS OF A RUPTURED ANEURYSM

If your patient survives a ruptured cerebral aneurysm, monitor her closely for rebleeding, cerebral vasospasm, and acute hydrocephalus, which are life-threatening complications. This table lists the signs and symptoms of each complication and tells when it’s most likely to occur and how it should be treated.

COMPLICATION	SIGNS AND SYMPTOMS	ONSET	TREATMENT
Rebleeding	Deterioration of neurologic status, decrease in level of consciousness (LOC), intensifying headache	7 to 10 days after rupture	• Sedation, rest • Avoidance of Valsalva’s maneuver
Cerebral vasospasm	Decrease in LOC, motor weakness or paralysis, vision deficits, changes in vital signs (particularly respiratory patterns)	Several hours to days after rupture	• Intravascular volume expanders • Induced hypertensive therapy • Calcium channel blockers
Hydrocephalus	Mental changes, gait disturbances, general mental and physical deterioration	Can occur several hours to days later as a result	• Cerebrospinal fluid drainage via intraventricular catheter

COMPLICATION

SIGNS AND SYMPTOMS

ONSET

TREATMENT

Rebleeding

Deterioration of neurologic status, decrease in level of consciousness (LOC), intensifying headache

7 to 10 days after rupture

• Sedation, rest

• Avoidance of Valsalva’s maneuver

Cerebral vasospasm

Decrease in LOC, motor weakness or paralysis, vision deficits, changes in vital signs (particularly respiratory patterns)

Several hours to days after rupture

• Intravascular volume expanders

• Induced hypertensive therapy

• Calcium channel blockers

Hydrocephalus

Mental changes, gait disturbances, general mental and physical deterioration

Can occur several hours to days later as a result

• Cerebrospinal fluid drainage via intraventricular catheter

Additional findings may result from complications. (See Complications of a ruptured aneurysm.)

To better describe the condition of patients with ruptured cerebral aneurysm, the following grading system was developed.

Grade I (minimal bleeding): The patient is alert, with no neurologic deficit; she may have a mild headache and nuchal rigidity.
Grade II (mild bleeding): The patient is alert, with a mild to severe headache, nuchal rigidity and, possibly, third-nerve palsy.
Grade III (moderate bleeding): The patient is confused or drowsy, with nuchal rigidity and, possibly, a mild focal deficit.
Grade IV (severe bleeding): The patient is stuporous, with nuchal rigidity, early decerebrate rigidity and, possibly, mild to severe hemiparesis.
Grade V (moribund [usually fatal]): If not fatal, the patient is in a deep coma or is decerebrate.

Diagnostic test results

Angiography confirms the aneurysm’s location and displays the vessels’ condition.
Lumbar puncture may detect blood in the CSF, but this procedure is contraindicated if the patient shows signs of increased ICP.
Computed tomography scanning locates the clot and identifies hydrocephalus, areas of infarction, and the extent of blood spillage in the cisterns around the brain.
Magnetic resonance imaging and magnetic resonance angiography show the extent of bleeding and the vessels’ condition.

Treatment

Initial treatment includes supportive measures, such as oxygenation and ventilation. Surgical repair includes clipping, ligating, or wrapping the aneurysm neck and usually takes place as soon as the patient is stable enough, generally 7 to 10 days after the initial bleed. (See Aneurysm clip, page 272.) Although surgery has been the standard of treatment for ruptured and nonruptured cerebral aneurysms, new interventional procedures, using such devices as coils, balloons, and stents, are proving successful.

After surgical repair, treatment is based on the extent of damage from the initial bleed and the degree of success in treating the resulting complications. Surgery won’t improve the patient’s neurologic condition unless it removes a hematoma or reduces the compression effect.

When surgical correction poses too much risk (in very elderly patients and those with heart, lung, or other serious diseases), when the aneurysm is in a particularly dangerous location, or when vasospasm necessitates a delay in surgery, the patient may receive conservative treatment, including:

bed rest in a quiet, darkened room (may last for 4 to 6 weeks)
avoidance of coffee, other stimulants, and aspirin
codeine or another analgesic, as needed
hydralazine (Apresoline) or another antihypertensive, if needed
a vasoconstrictor to maintain blood pressure at the optimum level (20 to 40 mm Hg above normal), if needed
corticosteroids to reduce meningeal irritation
phenytoin (Dilantin) or another anticonvulsant
phenobarbital (Luminal) or another sedative to relax the patient
nimodipine (Nimotop), a calcium channel blocker, to decrease cerebral vessel vasospasm
albumin for volume expansion, to decrease vasospasm
aminocaproic acid (Amicar), a fibrinolytic inhibitor, to minimize the risk of rebleeding by delaying blood clot lysis. (However, this drug’s effectiveness has been disputed.)

Nursing interventions

Maintain a patent airway and provide oxygen and ventilation, as needed.
Monitor the patient’s neurologic status.
Suction the patient cautiously (less than 20 seconds) to avoid increased ICP.
Monitor vital signs and pulse oximetry readings.
Provide frequent nose and mouth care.
Initiate aneurysm precautions: a quiet room, bed rest in the dark (with the head of the bed flat or elevated less than 30 degrees, as ordered), limited visitors, avoidance of such stimulants as coffee, avoidance of Valsalva’s maneuver and other strenuous activity, and restricted fluid intake.
Monitor for signs of rebleeding, intracranial clot, vasospasm, or other complications.
Administer medications, as ordered, and monitor effects.
Provide emotional support to the patient and his family. Encourage them to talk about their concerns. Listen carefully and answer their questions honestly and completely.
Reposition the patient every 2 hours and assess skin condition. Provide skin care.
Assist with active range-of-motion (ROM) exercises; if the patient is paralyzed, perform passive ROM exercises.
Administer I.V. fluids and monitor intake and output. Maintain fluid volume to decrease the risk of vasospasm.
Assess swallowing ability and assist with meals, as appropriate; administer enteral feedings, if ordered.

DISCHARGE TEACHING

TEACHING THE PATIENT WITH A CEREBRAL ANEURYSM

Before discharge, be sure to cover with the patient and his family:

the disorder and its implications
treatment options, such as surgery and therapy
medication administration, dosage, and possible adverse effects, and when to notify the physician
the importance of good nutrition and what types of food may be best based on swallowing ability
range-of-motion exercises to improve muscle tone and strength
types of therapy that would be beneficial, such as physical therapy, speech therapy, and occupational therapy
signs and symptoms of complications
the importance of follow-up care
the benefit of utilizing available community support groups such as the local chapter of the Brain Aneurysm Foundation.

Initiate seizure precautions, if indicated.
Monitor head dressings and provide wound care.
Monitor ICP and cerebral perfusion pressures, and provide measures to maintain adequate readings.
Monitor for postoperative complications, including sudden hemiplegia, psychological changes (disorientation, amnesia, Korsakoff’s syndrome, personality impairment), fluid and electrolyte disturbances, and GI bleeding.
Provide appropriate education to the patient and his family before discharge. (See Teaching the patient with a cerebral aneurysm.)

STROKE

Also known as brain attack or cerebrovascular accident, stroke is a sudden impairment of cerebral circulation in one or more blood vessels supplying the brain. Stroke interrupts or diminishes
oxygen supply and commonly causes serious damage or necrosis in brain tissues. The sooner circulation returns to normal after stroke, the better chances are for complete recovery. About half of those who survive stroke suffer a disability and experience a recurrence within weeks, months, or years.

Causes of stroke include cerebral thrombosis, embolism, and hemorrhage. (See Types of stroke, page 276.)

Thrombosis is the most common cause of stroke in middleage and elderly people. Embolism, the second most common cause of stroke, is especially prevalent among patients with a history of rheumatic heart disease, endocarditis, posttraumatic valvular disease, or myocardial fibrillation and other cardiac arrhythmias. It may also occur after open-heart surgery. Hemorrhage, the third most common cause of stroke, results from chronic hypertension or aneurysms.

Strokes are classified according to their course of progression. The least severe is the transient ischemic attack (TIA), which results from a temporary interruption of blood flow, most often in the carotid and vertebrobasilar arteries. (See Transient ischemic attack: A warning sign of stroke, page 277.)

A progressive stroke, or stroke-in-evolution (thrombus-inevolution), begins with a minor neurologic deficit and worsens over the course of 2 days. In a complete stroke, neurologic deficits are at the maximum at the onset.

Risk factors for stroke include:

atrial fibrillation
TIA
atherosclerosis
hypertension
renal disease
carotid stenosis
diabetes mellitus
cardiac or myocardial enlargement
sickle cell anemia
hypercoagulable states
hyperlipidemia

TYPES OF STROKE

Strokes are typically classified as ischemic or hemorrhagic, depending on the underlying cause. This chart describes the major types of stroke.

TYPE OF STROKE	DESCRIPTION
*ISCHEMIC*
Thrombotic	• Most common type of stroke • Commonly the result of atherosclerosis; also associated with hypertension, smoking, or diabetes (disease process similar to myocardial infarction [MI]) • Thrombus in extracranial or intracranial vessel blocks blood flow to the cerebral cortex • Carotid artery most commonly affected extracranial vessel • Common intracranial sites include bifurcation of carotid arteries, distal intracranial portion of vertebral arteries, and proximal basilar arteries • May occur during sleep or shortly after awakening, during surgery, or after an MI
Embolic	• Second most common type of stroke • Embolus from heart or extracranial arteries floats into cerebral bloodstream and lodges in middle cerebral artery or branches • Embolus commonly originates during atrial fibrillation • Typically occurs during activity • Develops rapidly
Lacunar	• Subtype of thrombotic stroke • Hypertension creates cavities deep in white matter of the brain, affecting the internal capsule, basal ganglia, thalamus, and pons • Lipid coating lining of the small penetrating arteries thickens and weakens wall, causing microaneurysms and dissections
*HEMORRHAGIC*
	• Third most common type of stroke • Typically caused by hypertension or aneurysm rupture • Blood supply to area from the ruptured artery diminished and surrounding tissue compressed by accumulated blood

TRANSIENT ISCHEMIC ATTACK: A WARNING SIGN OF STROKE

A transient ischemic attack (TIA) is an episode of neurologic deficit lasting less than 1 hour without permanent neurologic defects. It’s usually considered a warning sign of an impending stroke and may be recurrent. TIAs are reported in 50% to 80% of patients who had a cerebral infarction from such thrombosis. The age of onset varies. Incidence increases dramatically after age 50 and is highest among blacks and males.

With a TIA, microemboli released from a thrombus may temporarily interrupt blood flow, especially in the small distal branches of the brain’s arterial tree. Small spasms in those arterioles may impair blood flow and also precede a TIA. Predisposing factors are the same as those for thrombotic strokes.

Clinical features

The most distinctive characteristics of a TIA are the transient duration of neurologic deficits and the complete return of normal function. The signs and symptoms of a TIA correlate with the location of the affected artery. They include double vision, speech deficits (slurring or thickness), unilateral blindness, staggering or uncoordinated gait, unilateral weakness or numbness, falling because of weakness in the legs, and dizziness.

Treatment

During an active TIA, treatment aims to prevent a completed stroke and consists of aspirin, antiplatelet drugs, or anticoagulants to minimize the risk of thrombosis. After or between attacks, preventive treatment includes carotid endarterectomy or cerebral microvascular bypass.

individual history of stroke
family history of stroke
advanced age
smoking
use of hormonal contraceptives
lack of exercise.

Pathophysiology

Stroke that results from thrombosis causes ischemia, congestion, and edema in the brain tissue supplied by the affected
vessel; edema may produce more clinical effects than thrombosis itself, but these effects subside along with the edema. (See How stroke affects the body.)

HOW STROKE AFFECTS THE BODY

Stroke affects not only the brain and nervous system but other major body systems as well, which are outlined here. In addition, the patient with an acute stroke requires multidisciplinary care.

Nervous system

Pathophysiologic processes vary depending on the type of stroke.

Ischemic stroke

An ischemic stroke, which can be thrombotic or embolic, causes ischemia. Some of the neurons served by the occluded vessel die from lack of oxygen and nutrients.
Neuron death results in cerebral infarction, in which tissue injury triggers an inflammatory response that increases intracranial pressure (ICP).
Injury to surrounding cells disrupts metabolism and leads to changes in ionic transport, localized acidosis, and free radical formation.
Calcium, sodium, and water accumulate in the injured cells, and excitatory neurotransmitters are released.
Consequent continued cellular injury and swelling set up a cycle of further damage.

Hemorrhagic stroke

Impaired cerebral perfusion causes infarction, and the blood itself acts as a space-occupying mass, exerting pressure on brain tissues.
The brain’s regulatory mechanisms attempt to maintain equilibrium by increasing blood pressure to maintain cerebral perfusion pressure.
The increased ICP forces cerebrospinal fluid out, thus restoring the balance. If the hemorrhage is small, the patient may live with only minimal neurologic deficits. If the bleeding is heavy, ICP increases rapidly and perfusion stops. Even if the pressure returns to normal, many brain cells die.
Initially, the ruptured cerebral blood vessels may constrict to limit the blood loss.
This vasospasm further compromises blood flow, leading to more ischemia and cellular damage.
If a clot forms in the vessel, decreased blood flow promotes ischemia.
If the blood enters the subarachnoid space, meningeal irritation occurs.
Blood cells that pass through the vessel wall into the surrounding tissue may break down and block the arachnoid villi, causing hydrocephalus.

Cardiovascular system

Cerebral ischemia and infarction can ultimately affect the autonomic nervous system, which can alter blood vessel constriction and dilation, heart rate, blood pressure, and cardiac contractility.
Cardiovascular effects are increasingly problematic if the patient has an underlying disorder, such as heart disease or hypertension.

Musculoskeletal system

Cerebral infarction can lead to a disturbance in impulse transmission via the cranial and peripheral nerves, altering motor and sensory function.
Changes in sensation or mobility can lead to pressure areas, especially with prolonged bed rest or limited activity. In addition, the ability of the blood vessels to constrict and dilate as necessary may be altered, increasing the risk of impaired blood flow to the area. Subsequently, pressure ulcers may develop.

Respiratory system

If infarction resulting from increased ICP and decreased perfusion involves the respiratory center in the medulla, respiration—including the depth and rate—can be affected because nerve impulse transmission via the phrenic nerves to the diaphragm and intercostal nerves to the intercostal muscles is interrupted.
If the pons (the location for apneustic and pneumotaxic centers) is affected, breathing patterns become altered and impulse transmission via the cranial nerves (CN) may be interrupted.
If the glossopharyngeal (CN IX) and vagus nerves (CN X) are affected, swallowing may be impaired and aspiration may occur.

Collaborative management

Typically, emergency services personnel are involved in confirming the signs and symptoms of an acute stroke, completing the primary survey, and transporting the patient to the health care facility. A speech therapist may assist the patient with defects in swallowing as well as speaking. A physical therapist helps the patient relearn basic activities of daily living, such as dressing, bathing, and cooking. The patient and his family may benefit from pastoral or spiritual counseling and support groups. Social services ensures continuity of care after discharge to the patient’s home or to a rehabilitation facility and assists with follow-up care and financial and emotional concerns.

An embolism usually develops rapidly—in 10 to 20 seconds—and without warning. When an embolus reaches the cerebral vasculature, it cuts off cerebral circulation by lodging in a narrow portion of an artery, most commonly the middle
cerebral artery, causing necrosis and edema. If the embolus is septic and infection extends beyond the vessel wall, encephalitis or an abscess may develop.

Hemorrhage diminishes blood supply to the area served by the ruptured artery. In addition, blood accumulates deep within the brain, further compressing neural tissue and causing even greater damage.

Complications

Sensory impairment
Motor impairment
Altered level of consciousness (LOC)
Aspiration
Contractures
Complications of immobility
Deep vein thrombosis (DVT)
Pulmonary emboli
Depression
Malnutrition

Assessment findings

Clinical features of stroke vary with the artery affected and, consequently, the portion of the brain it supplies; the severity of the damage; and the extent of collateral circulation that develops to help the brain compensate for a decreased blood supply. The examination may reveal: