How Common is a Posterior Circulation Stroke?
Although PCS is less common than Anterior Circulation Stroke (ACS), which impacts the front part of the brain, it still represents a significant portion of stroke cases, accounting for approximately 20% of all strokes. In the United States alone, 70,000 to 100,000 people experience PCS annually.
The implications of a PCS can be profound, affecting various functions controlled by the posterior part of the brain, such as balance, coordination, vision, and consciousness. The severity of symptoms and the prognosis for individuals with PCS can vary widely.
Some patients may experience relatively mild effects and have a good chance of recovery, while others, particularly those with basilar artery occlusion (BAO), may face severe deficits or even death.
Mortality rates can be as high as 80% in severe cases, primarily when the occlusion affects the proximal or middle portions of the basilar artery, underscoring the critical nature of timely diagnosis and treatment.
Types and Locations of Posterior Circulation Stroke
PCS can manifest within the posterior part of the brain’s circulation system, primarily impacting the vertebral, cerebellar, and basilar arteries.
The diversity in the location of these strokes contributes to a broad spectrum of neurological symptoms, reflecting the complexity and critical functions of the affected areas.
Here’s a closer look at how strokes in these locations can influence brain function and patient symptoms:
Vertebral Arteries
The vertebral arteries are pivotal as they ascend through the neck and join at the base of the brain to form the single basilar artery. PCA strokes occurring in the vertebral arteries can lead to issues such as:
- Lateral Medullary Syndrome (Wallenberg’s Syndrome): Symptoms might include difficulty swallowing (dysphagia), hoarseness, dizziness, nausea, and a unique pattern of sensory loss – loss of pain and temperature sensation on the opposite side of the body and the same side of the face.
- Loss of Coordination: Affecting the cerebellum can lead to ataxia or a lack of muscle coordination, affecting the ability to perform voluntary movements like walking or picking up objects.
Cerebellar Arteries
The cerebellum, supplied by the cerebellar arteries, plays a crucial role in motor control and balance. Strokes in this region can cause:
- Ataxia: As mentioned, this is a lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and movements that are not smooth or precise.
- Nausea and Vomiting: The cerebellum’s role in balance can also influence the vestibular system, leading to vertigo, dizziness, and associated symptoms.
Basilar Artery
The basilar artery supplies blood to the brainstem and parts of the cerebellum, making strokes in this area particularly severe. Potential posterior stroke symptoms include:
- Quadriplegia: Loss of movement in all four limbs due to brainstem involvement.
- Locked-In Syndrome: A condition where the patient is awake and mentally aware but cannot move or communicate verbally due to paralysis of nearly all voluntary muscles in the body except for eye movement.
- Cranial Nerve Deficits: This leads to facial weakness, difficulty speaking (dysarthria), and swallowing problems.
How is a Posterior Circulation Stroke Diagnosed?
Diagnosing PCS is a multifaceted process that requires a combination of clinical acumen and advanced imaging techniques to identify and evaluate the extent of the stroke accurately.
The process typically unfolds in several key steps:
Initial Clinical Assessment
The first step in diagnosing PCS involves a comprehensive clinical evaluation beginning with a detailed patient history to gather information on symptom onset, duration, progression, and any potential risk factors like hypertension, atrial fibrillation, diabetes, smoking, or a history of previous strokes. This history helps assess the likelihood of a stroke and its possible type.
Neurological Examination
A more focused neurological examination assesses motor and sensory function, cranial nerve integrity, coordination, reflexes, and cognitive function. Specialized tests may also be conducted to evaluate balance, vision, speech, and swallowing. This comprehensive neurological evaluation helps localize the lesion within the central nervous system and supports the suspicion of PCS.
Imaging Tests
After the initial assessment suggests a PCS, imaging studies are pivotal in confirming the diagnosis and delineating the stroke’s location and extent.
- Magnetic Resonance Imaging (MRI): Highly sensitive for detecting ischemic strokes, including those in the posterior circulation. DWI can reveal ischemic changes within minutes to hours after symptom onset, making it a crucial tool in PCS diagnosis. MRI can also provide detailed information about the brainstem, cerebellum, and other PCS-affected structures.
- Computed Tomography (CT) Scan: Often the first imaging modality used in acute stroke settings due to their wide availability and speed. They can quickly rule out hemorrhagic strokes and other causes of similar symptoms.
- Magnetic Resonance Angiography (MRA) and CT Angiography (CTA): Used to visualize the blood vessels and can identify occlusions or stenoses in the vertebral and basilar arteries, confirming the presence of a posterior circulation blockage.
- Digital Subtraction Angiography (DSA): Considered the gold standard for detailed vascular imaging. It is instrumental when other imaging studies are inconclusive or when endovascular treatment options are being considered.
Understanding Crossed Symptoms
Crossed symptoms are common in PCS cases. These posterior circulation stroke symptoms manifest as a combination of cranial nerve dysfunctions on one side of the body (ipsilateral) and sensory or motor deficits on the opposite side (contralateral). This occurrence is directly linked to the brainstem’s unique anatomical structure and the crossing (decussation) of various neural pathways within the central nervous system.
The brainstem, a critical structure affected in PCS, houses the origins of most cranial nerves and is a conduit for long nerve tracts that relay motor and sensory information between the brain and the rest of the body.
Because some of these pathways cross to the opposite side before entering or after exiting the brainstem, a lesion in this area can impact the cranial nerves (affecting functions like facial movement or swallowing) and the long tracts (affecting sensation and movement in the limbs).
Crossed symptoms in PCS cases pose a significant diagnostic challenge for healthcare professionals. Unlike more straightforward instances in which deficits are localized to one side of the body, the dual nature of crossed symptoms can obscure the clinical picture, leading to potential misdiagnosis or delays in identifying the underlying stroke.
The Causes of Misdiagnosis
Regrettably, cases of PCS are frequently misdiagnosed, with substantial clinical studies indicating that a significant proportion of PCS cases are initially missed or incorrectly identified as other conditions.
In fact, between 28% and 59% of cerebellar strokes, a specific type of PCS, are initially misdiagnosed. According to a recent study involving 465 stroke patients, the misdiagnosis rate for those with PCS was 38%, which is 2.5 times more likely than those with ACS, who had a rate of 16%.
Causes of Misdiagnosis in PCS
- Nonspecific and Overlapping Symptoms: Patients with PCS may experience symptoms similar to those of ACS and other non-stroke conditions. These symptoms are common and may not necessarily indicate a stroke, making it challenging for clinicians to diagnose PCS accurately.
- Lack of Lateralizing Symptoms: One of the difficulties in diagnosing PCS is the absence of clear lateralizing signs, especially in younger patients. The sudden onset of neurological symptoms without clear lateralization can mislead clinicians to overlook stroke as a potential diagnosis.
- Commonality of Presenting Symptoms: The PCA symptoms, such as dizziness and sensory disturbances, are commonly observed in emergency department patients, most of whom are not experiencing a stroke. Consequently, it can be hard to identify PCS, as these symptoms are prevalent and may not necessarily indicate a stroke.
- Younger Age and Unusual Causes: A higher risk of misdiagnosis is associated with younger patients and those with vertebral artery dissection as the cause, mainly presenting with dizziness. This could be because stroke is believed to be less likely in younger individuals and the unique presentation of VAD-related strokes.
- Transient Symptoms: Diagnostic errors may result from misconceptions about transient ischemic attacks (TIAs), especially isolated transient dizziness. A considerable proportion of patients experiencing posterior circulation TIAs present with isolated vertigo or non-focal symptoms, which may not meet traditional criteria for TIA but still indicate a significant risk for subsequent stroke.
- Imaging Limitations: Although advanced imaging techniques such as diffusion-weighted imaging (DWI) MRI are essential for diagnosing PCS, there are limitations. In some cases, early imaging may fail to capture the stroke, contributing to a misdiagnosis.
Entrust Your Stroke Recovery Journey to Trusted Experts
Navigating the aftermath of a stroke can feel overwhelming, but you don’t have to face it alone. At Moody Neurorehabilitation, we specialize in providing compassionate and comprehensive post-stroke care, understanding the unique challenges of recovery, and recognizing and managing Posterior Circulation Stroke symptoms.
Our dedicated team of experts employs a patient-centered approach, crafting personalized treatment plans that address the physical and emotional aspects of recovery. We believe in empowering our patients and their families with knowledge, support, and the latest rehabilitative therapies.
Embark on your journey to recovery with Moody Neurorehabilitation. Let us guide you through each step with expertise and empathy, ensuring you feel supported in your rehabilitation journey.
Contact us today to schedule a consultation and discover how our specialized care can make a difference in your life or that of a loved one.
Sources:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6170115/
https://www.rcpjournals.org/content/clinmedicine/23/3/219
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4530423/