Posterior Cerebral Artery Stroke Treatment & Management

The treatment approach to stroke is determined by localizing the problem (identifying the vascular territory involved) and subsequently by using the patient’s history, the stroke subtype, and investigational tools to discover the stroke mechanism. The medical treatment of stroke can be divided into acute (within 3-4.5 hours of stroke onset), subacute, and chronic phases.

If possible, patients with acute stroke should be cared for in a stroke unit by staff familiar with stroke etiology, workup, and treatment, and with poststroke complications. Patients may require intensive care unit (ICU) monitoring if they have a large-volume stroke, significant concomitant brainstem infarcts or tissue at risk, or significant comorbid medical conditions (ie, myocardial infarction) or if they have received acute stroke therapies.

The management of acute stroke in general may be complicated and extensive. Various considerations need to be made regarding issues such as management of hypertension, hyperglycemia, cerebral edema with increased intracranial pressure, hemorrhagic transformation of cerebral infarction, infections, aspiration, deep venous thrombosis, myocardial infarction, and other stroke-associated conditions.

Isolated posterior cerebral artery (PCA) stroke may not have all the attendant complications as the associated disability or volume of infarction may be less than with other stroke syndromes (eg, MCA or BA stroke syndromes).

Multidisciplinary approach

As previously mentioned, in a single-blind cluster, randomized, controlled trial of stroke patients in acute stroke units, there was a decreased likelihood of death or dependence by 90 days after hospital admission in patients who received a multidisciplinary intervention focusing on evidence-based management of fever, hyperglycemia, and swallowing dysfunction, despite the severity of the stroke. ^[6]

Experimental therapies

Many experimental treatment modalities such as cognitive retraining, ^[12] neuropharmacologic therapy (amphetamines), ^[13] robot-assisted physical and occupational therapy, and virtual environments ^[14] are reported to aid stroke recovery, but further evidence is needed to confirm their benefit.

Rehabilitation goals

Patients with acute posterior cerebral artery (PCA) infarcts generally are hospitalized, unless, due to late diagnosis, they can be seen safely on an outpatient basis. Aggressive rehabilitation begins once the patient is medically stable. Goals include maintaining range of motion, promoting active movement of the hemiplegic side if applicable, improving the patient's functional mobility and self-care capabilities, and monitoring medical conditions affecting recovery and prevention of further disability.

Activity

Activity restriction varies depending on the patient's deficits, but the patient should be encouraged to remain mobile if possible. At discharge, activities may be limited by neurologic deficits. The patient may be required to give up driving.

Management of mobility-related concerns

Painful contractures develop rapidly in weakened limbs and may impede recovery. Early and frequent performance of range of motion can help to prevent this problem.

Weakened patients may fall and suffer traumatic head injury or fractured hips. Close monitoring of patients with cognitive impairment and training of family is important.

Although deep venous thrombosis (DVT) is unusual in patients with isolated posterior cerebral artery (PCA) stroke, any patient who has diminished mobility from stroke (ie, concurrent brainstem stroke) or a comorbid condition should receive prophylactic therapy for DVT. This includes early mobilization, subcutaneous heparin, pneumatic pressure, and elastic stockings.

Decubitus ulcers develop rapidly in immobilized patients. Wet bedclothes facilitate skin breakdown. Attentive nursing care is essential.

Postdischarge pharmacotherapy

Discharge medications may include specific agents for stroke prevention (eg, aspirin, clopidogrel, warfarin) that usually are recommended by the neurologist prior to transfer to a neurorehabilitation setting. Cholesterol-lowering drugs, antihypertensive therapies, muscle relaxants, and substances for treating rare thalamic pain or chronic headaches or depression may be prescribed.

IV tissue plasminogen activator (tPA) may be given to patients who present within 3 hours of developing a disabling ischemic stroke. Because of the increased risk for complicating intracerebral hemorrhage, there are rigid guidelines for administering tPA.

In 2009, the American Heart Association/American Stroke Association (AHA/ASA) published a science advisory recommending that the time window for tPA administration be increased to 4.5 hours after a stroke, although this change has not been approved by the US Food and Drug Administration (FDA). ^[15] Research indicates that tPA is effective in patients even when administered within the 3- to 4.5-hour window, ^{[16, 17, 18]} but the AHA/ASA stated that, despite its recommendation, the effectiveness of tPA administration in comparison with other treatments for thrombosis, within that time period, is not yet known.

The eligibility criteria for treatment between 3 and 4.5 hours are similar to those employed for treatment prior to 3 hours, as established in the AHA/ASA's 2007 guidelines, ^[19] but with the exclusion criteria expanded to include any of the following patient characteristics:

• Age older than 80 years

• Use of oral anticoagulants

• Baseline NIH Stroke Scale score of greater than 25

• History of both minor stroke and diabetes

If a clear time of onset can be established, stroke in the PCA territory may be treated with IV TPA. However, because isolated PCA territory symptoms may be subtle or underappreciated, patients may mistake the time of stroke onset. Patients who experience significant motor, sensory, or language symptoms (middle cerebral artery [MCA] or basilar artery syndromes) are more likely to present urgently and with more precise time of onset. Administration of TPA beyond the recommended time limits likely offers no benefit to patients and exposes them to increased risk of intracerebral hemorrhage.

Angioplasty, stenting, mechanical embolectomy, and intra-arterial thrombolysis are enjoying ever-expanding application and use in acute stroke, although their roles continue to be defined. However, their application in the posterior cerebral artery (PCA) distribution is uncommon compared with other vascular distributions (internal carotid artery [ICA], middle cerebral artery [MCA], basilar artery, vertebral artery). This is likely due to the small size of the PCAs, low NIH Stroke Scale scores in which treatment benefit may be offset by procedural risk, delayed recognition of isolated PCA stroke syndromes, and other factors. Numerous mechanical embolectomy devices have been studied, and few have allowed or incorporated isolated PCA stroke for inclusion.

Endovascular therapies are more likely to be used if there is significant vertebrobasilar disease as the cause of PCA stroke or if the patient fails to respond to medical management. When the ICA is the source of stroke via a fetal PCA variant, surgical endarterectomy or endovascular stenting of the ICA may be appropriate.

More recently, treatments such as vertebral artery stenting have been used and may replace the medical-treatment-only approach to intrinsic vertebral artery disease.

In a study of treatment of 25 cases of PCA aneurysm, the authors found that treating PCA aneurysms with microsurgical or endovascular options can achieve comparable outcomes. In this study, endovascular treatment showed excellent anatomical and clinical outcomes for non-mass compressing, non-giant, saccular aneurysms. However, the authors noted that given the propensity for large-giant, dysplastic PCA aneurysms to develop in younger patients, microsurgical competence should be maintained. They also suggested that along with careful evaluation of the anatomic collaterals over the PCA territory, therapeutic parent artery sacrifice may be an appropriate option without adding bypass. There was no mortality in either group. Microsurgical treatment was the primary treatment in 15 aneurysms. Endovascular coil embolization was performed in 6 aneurysms, stent-assisted coil embolization in 2 aneurysms, and endovascular occlusion of the parent artery in 2 aneurysms. ^[20]

In unusual circumstances, vertebral artery bypass may be considered; however, this surgical procedure remains an unproven therapy. Extracranial (EC)-to-intracranial (IC) vertebral artery bypass may be undertaken by connection of the occipital artery to the vertebral, superior cerebellar, anterior internal carotid artery (ICA), or posterior ICA. The superficial temporal artery has also been used as a donor artery. Shunting to the posterior cerebral artery (PCA) may be accomplished by using veins or synthetic grafts. In general, EC-to-IC circulation shunting has been relegated to use in extenuating circumstances since the publication of the negative EC-IC bypass trial. ^[21]

Patients with posterior cerebral artery (PCA) stroke experience a dramatic alteration of visual function, requiring modification of ADL. Homonymous field loss makes these patients prone to burns, motor vehicle accidents, mechanical injury from falls, and walking into objects. Explain these risks clearly to the patient and his/her family. Do not allow driving until follow-up evaluations of visual-field loss have been completed and occupational therapists and clinicians have tested the patient for visual function. The patient must learn conscious scanning into the visual-field deficit.

The hemiparetic patient who has sustained a posterior cerebral artery (PCA) stroke must learn transfer techniques, walking with mechanical assistance (if feasible), and modified ADL (eg, dressing, bathing, cooking). Some patients require a significant amount of assistance. The patient's caregiver should meet with therapists to learn how best to help the patient at home without causing personal or other injury.

Depending on the degree of motor loss, available insurance coverage, and other variables, such as social situation, the patient may qualify for continued outpatient or home therapy.

Physical therapy

A small percentage of patients with a PCA infarct suffer chronic motor deficits. Approximately 5% of patients who do may require transfer, gait, and stair training with an assistive device. Orthotic devices (eg, ankle-foot orthosis) also may be beneficial.

Patients with PCA infarcts may demonstrate delayed postural reactions due to sensorimotor deficits. Programs designed to improve postural control and balance may be helpful.

Home exercise programs and family/caregiver training are important for sustaining improvement after discharge from therapy. ^[1]

Occupational therapy

The occupational therapist helps the patient adapt to homonymous hemianopia and visual-spatial function abnormalities. The patient benefits from scanning into the field deficit. A small percentage of patients who have suffered a PCA stroke require therapy for motor deficits of the upper limb.

Speech therapy

Speech therapy usually is not required for patients who have had a PCA stroke. However, in infrequent cases in which there is neuropsychological deterioration or memory-language deficits, ^[9] a speech therapist should be consulted.

Although dysphagia typically is not associated with PCA infarcts (unless there are concomitant brainstem infarcts), evaluation of swallowing may be useful in patients who may be at risk for aspiration.

Recreational therapy

Recreational therapy helps patients with posterior cerebral artery (PCA) stroke to adapt to visual deficits and facilitates a healthy affect (since depression is a common occurrence in stroke patients).

Acute stroke patients should undergo a bedside sips test to grossly assess for dysphagia (excepting those who have frank severe dysarthria/dysphagia or altered mental status).

A speech pathologist and dietitian may provide advice on diet immediately and in the long term. Enteral nutrition may need to be provided by alternative means, such as a nasogastric device or a percutaneous enteric gastrostomy tube in patients who have severe dysphagia. As mentioned previously, however, dysphagia is generally not an issue with PCA strokes unless there are concomitant brainstem infarcts.

Visual issues may need to be addressed, because patients may not be able to see one side of the plate and may neglect some of their food. In such cases, patients need to have the plate turned and must eventually be taught to turn their head to see the blind hemifield.

A heart-healthy diet is really an antiatherosclerosis diet and may be applicable depending on stroke mechanism and underlying risk factors. This prescription should be based on follow-up testing and investigation.

Stroke care is a multidisciplinary process. Participants may include a neurointensivist, a neurointerventionalist, a vascular surgeon, a neurologic surgeon, a stroke nurse specialist, a physical therapist, an occupational therapist, a speech therapist, a physiatrist or rehabilitation neurologist, and a case manager or social worker.

Ophthalmologists accurately plot visual-field loss in patients with posterior cerebral artery (PCA) stroke and can recommend corrective lenses and compensation techniques.

Pain specialists use many strategies to treat rare, intractable thalamic pain, including the employment of anticonvulsants (carbamazepine [Tegretol], gabapentin [Neurontin]) and tricyclic medications (amitriptyline [Elavil]). In addition, topiramate (Topamax) has been found to be helpful in treating headache and painful dysesthesias.

A psychiatrist may assist with treatment of mood disorders and psychotic symptoms. A neuropsychologist can help to assess and document cognitive function, which is especially important for persons returning to professional duties, considering living alone, or applying for disability.

Early attention to rehabilitation and eventual reintegration into the community speeds recovery and shortens the length of hospital stay.

Patients who have had a posterior cerebral artery (PCA) stroke should be observed on an outpatient basis to ensure that cerebrovascular risk factors are treated chronically, that changes in medication management following stroke are well tolerated, and that chronic disability is appropriately addressed.

Attention to rehabilitation should begin early. Involvement of a speech-language therapist may be required if alexia is present, with or without aphasia. An occupational therapist should be able to help teach patients to turn in order to view a blank visual hemifield.

An issue that frequently arises with infarction of the visual cortex or its afferent fibers is patient competency to drive a vehicle. Patients with infarction in the territory of the left PCA may have preserved macular vision but severe restriction of peripheral vision, as well as an inability to read in any visual field. Patients with infarction in the territory of the right PCA may have significant visual hemineglect.

Careful examination of the patient and knowledge of local laws governing the right to drive are a necessity. Repeated visual-field testing is required (some recovery of vision may occur), as well as further assessment by occupational therapists and clinicians.

Patients often have to relinquish their driver’s license because of the visual field loss. This may result in considerable loss of independence and provoke anger and grief in the patient, for which counseling may be required.

Treatments for recurrent stroke prevention should be instituted as soon as possible. The identified etiology of the stroke will determine what treatments are indicated (medical, surgical, endovascular) for preventing recurrent events.

Anticoagulant and antiplatelet therapies

Long-term anticoagulation with warfarin is indicated in several settings—including atrial fibrillation, selected cases with significant global or regional cardiac hypokinesis (ejection fraction < 35%), patent foramen ovale with documented hypercoagulable condition, and arterial hypercoagulable state—for prevention of recurrent strokes.  Novel anticoaguants, including dabigatran, rivaroxaban and apixaban, may be used for stroke prevention in the context of non-valvular atrial fibrillation.  The risks of recurrent stroke have to be balanced with the risk of oral anticoagulation therapy. For patients in whom no cause for recurrent strokes can be found despite extensive work-up, antiplatelet therapy is generally recommended instead of anticoagulation therapy.

Antiplatelet therapies are often the mainstay of recurrent stroke prevention. In most cases, they can be instituted immediately, and evidence suggests that doing so decreases recurrent events immediately and chronically. Aspirin, 325 mg daily, has been shown to reduce the rate of acute recurrence of stroke (ie, in the first 14 days after first stroke) when administered within 48 hours of the first stroke.

Ticlopidine, clopidogrel, and aspirin plus extended-release dipyridamole (Aggrenox) also prevent recurrent stroke, although ticlopidine is rarely used due to a higher risk of side effects. These agents produce platelet inhibition by a number of different mechanisms.

Early anticoagulation with heparin

Anticoagulation is infrequently indicated in the acute phases of posterior cerebral artery (PCA) stroke. While historically, early anticoagulation (generally with heparin infusion) has been used in acute stroke, significant supporting data have been absent.

Indeed, early anticoagulation, particularly with heparin, has been studied in a number of diagnostic settings but has not been demonstrably proven to be beneficial. Cochrane reviews of studies totaling more than 20,000 patients have suggested that early anticoagulation does not produce a mortality or morbidity benefit. ^{[22, 23]} In specific cases (large vessel, high-grade stenosis), some benefit may have been seen; however, this was offset by increased hemorrhagic complications.

The rationale for the acute use of anticoagulant therapy lies in preventing acute recurrence of stroke; however, trials have shown that this risk of early recurrent stroke is low and that heparin does not provide any functional or survival advantage. Nonetheless, this remains a controversial area, with some stroke experts having strong opinions about acute anticoagulation.

In general, the stroke mechanism should be identified so that a better, informed decision can be made before long-term anticoagulation is chosen. PCA strokes that arise from vertebral artery dissection are more frequently treated with anticoagulation, although again there is a paucity of data to support this use.

Early anticoagulation may be the most appropriate preventive strategy in specific circumstances that are considered high-risk, such as the presence of an intracardiac thrombus or a dissection with visualized large intraluminal thrombus. Strokes caused by atrial fibrillation do not require early anticoagulation with heparin. Studies have demonstrated that the risk of recurrent stroke within the first weeks is approximately 1%. ^[24] Early heparinization in this setting is associated with no clear stroke prevention benefit but is associated with increased hemorrhagic complications.

LMWH

Heparin and low-molecular-weight heparin (LMWH) should be titrated individually based on aPTT. A heparin bolus is infrequently given due to concerns of hemorrhage. This approach may be justifiable given evidence that heparin does not provide an acute advantage in nonselective use in ischemic stroke.

The optimal dosing regimen for heparin in stroke has not been established. LMWHs, also known as fractionated heparins, have become available in the last few years and have revolutionized therapy of venous thrombosis and acute coronary syndromes.

LMWH therapy in the acute setting should be cautiously considered because no antidote is available for quick reversal of anticoagulation in the event of intracerebral hemorrhage. In the subacute setting, LMWH may be used as a bridge to long-term anticoagulation with warfarin.

Other prophylactic measures

Effective treatment of hypertension has been proven to reduce the risk of recurrent stroke. In addition, emphasis should always be placed on smoking cessation, moderation of alcohol use, and discontinuation of illicit substance use.

In patients with elevated cholesterol, sustained reduction in cholesterol levels may also reduce the chances of stroke. Numerous studies have demonstrated a modest stroke risk-reduction benefit in patients with coronary heart disease; however, the results of the Stroke Prevention by Aggressive Reduction in Cholesterol levels (SPARCL) study suggest that patients without CHD also have a lower incidence of stroke on statin therapy. ^[25]

Numerous statins (eg, lovastatin, simvastatin, pravastatin, atorvastatin) are available. All inhibit the enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in the anabolism of cholesterol. These drugs are effective in reducing levels of low-density lipoprotein (LDL) cholesterol but have less effect on high-density lipoprotein (HDL) cholesterol and triglycerides.

The statins may have other, pleiotropic effects in stroke prevention, such as plaque stabilization, reduction of free radical formation, and anti-inflammatory, immunomodulatory, and antiplatelet effects. Additionally, prestroke use of statins may be associated with smaller infarct or better outcomes. Large vessel atherosclerosis may undergo regression in patients treated with statin therapy.