WALLENBERG SYNDROME – SYMPTOMS, CAUSES, RISK FACTORS AND TREATMENT

As with other brainstem stroke syndromes, Wallenberg Syndrome highlights the importance of protecting the neck and head, as well as the health of the cardiovascular system.

The article below aims to describe Wallenberg Syndrome, the associated symptoms, and the brain structures involved. The following discussion also covers prognosis, causes, diagnosis, treatment, and prevention.

What is Wallenberg Syndrome?

Wallenberg Syndrome is one of the most common conditions that occur as a result of a brainstem stroke arising from ischemia of the Vertebral Artery (VA) or Posterior Inferior Cerebellar Artery (PICA). It is also known as  Lateral Medullary Syndrome or PICA syndrome. Lateral Medullary Syndrome is one of many brainstem stroke syndromes that occur due to ischemic strokes of the posterior circulation. The posterior circulation refers to the major arteries behind the carotid arteries that supply blood to the brain.[1]

Prevalence. Depending on the source, ischemic strokes account for up to 62-87% of all cases globally, averaging 7.6 million strokes per year.[2] Of these, 20-25% are posterior circulation strokes, which largely affect the brainstem and lead to brainstem stroke syndromes. It is estimated that Wallenberg Syndrome makes up half of brainstem syndrome cases, suggesting that there are roughly 750 000 - 950 000 new cases worldwide every year. Other sources suggest the global incidence is much lower, indicative of 152 000 - 228 000 (2-3% of ischemic strokes) per annum.

Anatomy. Those with Wallenberg Syndrome experience symptoms that arise from blood flow obstruction to the following arteries and brain areas:

• The Vertebral Artery (VA) is the main artery that supplies blood to the medulla oblongata in the brainstem and adjacent parts of the lower cerebellum. It runs through the spine in the neck and eventually becomes the basilar artery, which reaches the inner core regions of the upper cortices.
• The Posterior Inferior Cerebellar Artery (PICA) joins the VA just before it merges with the basilar artery, diverging into the lower cerebellum regions (the cerebellum tonsils and cortical branch segments).
• The Brainstem is responsible for coordinating involuntary physical processes and reflexes (e.g., heartbeat, respiration, blinking, etc.), as well as for rerouting sensory information to higher brain areas.
• The Cerebellum helps to coordinate physical movement, including speech, motor learning, fine motor control, posture, gait, and movement evaluation.[3]

Symptoms

The symptoms of Wallenberg Syndrome are usually acute, yet roughly 25% of patients may experience a gradual onset of symptoms over several hours to days. Patients with gradual onset tend to develop headaches or migraines first, coupled with dizziness and gait ataxia, while other symptoms typically develop later on. Rare cases of head and neck trauma may cause symptom manifestation to be delayed for as long as 3-6 months.

Wallenberg Syndrome symptoms usually consist of the following:

• Dizziness
• Vertigo (sensation of internal or external spinning)
• Nystagmus (involuntary eye movements)
• Ataxia (reduced muscle control, or coordination resulting from brain, nerve or muscle damage)
• Nausea or vomiting
• Hiccups

It is rare for Wallenberg Syndrome symptoms to present uniformly among patients as it depends on the location of the stroke along the arteries and which parts of the brainstem they affect. The below points detail symptoms in accordance with affected brainstem areas during a stroke.[4]

• Ipsilateral Side. Symptoms arising from the same side of the body  as the VA or PICA stroke include:
• Inferior Vestibular Nucleus: Vertigo, Nystagmus, double vision (Diplopia), misalignment of the eyes (skew deviation), nausea, vomiting, and hiccups.
• Medullary and Pons Fibers: Difficulty in speaking and swallowing, as well as loss of voice, hoarseness, and gag reflex.
• Sympathetic Fibers: Horner Syndrome characteristic of a constricted pupil (Miosis), drooping eyelid (Ptosis), and sweat impairment (Anhidrosis).

Cerebellum Structures: Ataxia

• Trigeminal Nerves: Pain, numbness, and loss of sensation in the face
• Nucleus Tractus Solitarius: Loss of taste and hyponatremia due to reduced antidiuretic hormone

Contralateral Side. Symptoms that occur on the side of the body opposite to the stroke site include:

• Spinothalamic Tract: Loss of pain and temperature sensation in arms and legs
• Ventral Corticospinal Fibers: Little to no weakness in the side of the body opposite to the stroke side.

Non-conventional symptoms and complications are also known to occur in those with Wallenberg Syndrome, including hypoventilation syndrome[5], facial paresis[6], and more.

Causes

Causes of Wallenberg Syndrome pertain to occlusion of the VA or PICA, with 80% of cases being attributable to the former. The occlusion usually occurs as a result of a cardiovascular condition coupled with other risk factors or as a result of injury. However, injury is a more common cause in younger individuals.

Atherothrombosis is the most common primary cause of arterial occlusion and is usually linked to atherosclerosis. In atherosclerosis, fats, and other substances create plaques in the walls of blood vessels, which narrow them and lower blood flow. Atherothrombosis can occur when a plaque disrupts, creates a lesion and a thrombus, which can occlude arteries and lead to an ischemic stroke of the brainstem and Wallenberg Syndrome.[7] Small vessel disease, in which similar processes happen in the small blood vessels, is also a prevalent cause of Wallenberg Syndrome and often also promotes Hypertension.

Risk Factors

Risk factors for Wallenberg Syndrome are the same as those for all other types of ischemic stroke, including:

Hypertension is quoted to be the most important risk factor for any kind of stroke. Up to half of those with stroke are estimated to have a history of Hypertension. Dietary and lifestyle factors that chronically increase blood pressure can promote Hypertension. Certain health conditions can predispose people to higher blood pressure, Hypertension, and Stroke. Fibromuscular Dysplasia is a condition in which the arteries are too large, causing blood flow compression and higher blood pressure. In some patients, symptoms overlap with Wallenberg Syndrome and may increase the risk.[8]

Smoking is known to double the risk of stroke while stopping can reduce the risk caused by smoking within 2-4 years.

Obesity, Metabolic Syndrome, Diabetes, and Heart Disease. Individuals who have metabolic syndrome are predisposed to a number of serious chronic lifestyle disorders.These include high blood pressure, Hyperglycemia, Hyperinsulinemia, Obesity, Hypercholesterolemia, and Dyslipidemia[9]. Patients with Hypertension, Diabetes, cardiovascular disease, and non-alcoholic fatty liver disease often have metabolic syndrome first. These diseases are considered to be various manifestations of advanced metabolic syndrome. Metabolic syndrome and its related diseases can increase the risk of stroke, especially with regard to Dyslipidemia and Hypertension. Diabetes is the most common manifestation of metabolic syndrome associated with Wallenberg Syndrome.

History of Stroke, Heart Attack, or Cardiac Anomalies. Those with a history of either stroke or heart attack are usually at an increased risk of contracting another in the future. Cardiac risks specific to those with Wallenberg Syndrome include large artery disease or Atherothrombosis, as well as Cardioembolism and related Atrial Fibrillation. Atrial Fibrillation and other unusual cardiac activity may also elevate the risk, which increases with age and the presence of metabolic syndrome factors.

Head and Neck Injury or Trauma. Injuries or traumatic wounds can impact the blood flow of the arteries in the spinal column of the neck, as well as in the base of the head. This is a more prevalent cause of Wallenberg Syndrome in younger individuals, who tend to sustain neck and head injuries more on average than the elderly. Infants and young children are more sensitive to injuries of the neck and head due to immature bone formation. They commonly present with wounds lower down by comparison to adults. Neck injuries may also occur as a result of neck manipulation, which can increase the risk of arterial occlusion and Wallenberg Syndrome. In some circumstances, injuries may cause symptoms of lateral medullary syndrome to occur only 3 - 6 months after as a result of the mildly reduced posterior circulation.[10]

Surgery. The VA and PICA are exposed during various types of brain surgeries. They may accidentally become occluded as a surgical complication, which can greatly increase the risk of developing Wallenberg Syndrome.

Rare Conditions. Atypical strain within or growth of blood vessels due to connective tissue disorders can heighten the chance of brainstem strokes.

Diagnosis

Diagnosis of brainstem stroke syndromes is considered to be difficult due to the wide symptom presentation. The patient will be examined by a healthcare practitioner, who will assess their symptoms and medical history. The physician will need to rule out other conditions and may carry out blood tests as well. Wallenberg Syndrome can sometimes be confused for acute demyelination in Multiple Sclerosis or Neuromyelitis Optica. Treatment may begin once a stroke has been diagnosed, even before the patient is diagnosed with a brainstem stroke or Wallenberg Syndrome.

Imaging Techniques are used to confirm the site of occlusion and the degree of brain damage. CT scans are often used for the initial diagnosis, while MRIs are able to further detail the stroke’s location. Diffusion-weighted MRI is able to detect the onset of a brainstem stroke early on. Digital Subtraction Angiography is the golden standard for diagnosing VA injury as it is one of the most accurate imaging techniques, able to give the precise location of the lesion. However, it may increase the risk of stroke by 0.5%. CT and MR angiography proved to be better imaging methods with a higher accuracy and lower risk involvement.

Treatment Options

The treatment of Wallenberg Syndrome is similar to that of any other ischemic stroke, aiming to lower the size of the blood vessel blockage and minimize the risk of post-stroke complications. Treatment is divided into acute treatment and long-term treatment.

Acute Treatment starts within the first 3 - 4.5 hours after stroke onset if symptoms are acute and the patient has been accurately diagnosed. The patient will be monitored for the development of any further complications in the ICU, usually for a period of 24 hours until stable. During that time, treatment often includes the following:

• Anticoagulants and Antihypertensives. It is common for the IV administration of potent anticoagulants and antihypertensives to occur within the first 3 - 4.5 hours of stroke onset. This helps to dissolve the obstruction, improve blood flow, and prevent further tissue damage to oxygen-deprived areas. Studies indicate that IV Thrombolysis may improve outcomes by as much as 30% on average.
• General Critical Care. After the patient has been stabilized, they are monitored and prescribed medications to control for risk factors that may detract from successful recovery. These often include additional anticoagulants and antidiabetic medications that control excess blood glucose levels. Blood thinning medications are contraindicated in the case of severe Traumatic Brain Injury or Aneurysm. The patient may require a respirator, postural support, or feeding assistance if unable to speak, swallow, or breathe optimally.
• Stents. If a head or neck injury was implicated in causing Wallenberg Syndrome and anticoagulant treatment proves ineffective or is contraindicated, surgical stents may be recommended to improve blood flow to affected areas.

Long-Term Treatment and Secondary Stroke Prevention. After the patient’s condition has been stabilized, long-term treatment aims to prevent future stroke occurrences and correct any residual complications. Common and novel rehabilitation and prevention strategies are described below:

• Speech Therapy. Some patients may lose their ability to swallow, which can affect drinking, eating, and talking. Speech therapy is often recommended for such patients. Limited evidence suggests that it benefits many post-stroke patients with dysphagia[11] and that it may help to restore normal swallowing function within 3 months. During that time, the patient may need to remain hospitalized and be dependent on an orogastric tube to facilitate feeding.
• Rehabilitation. Besides speech therapy, rehabilitation often consists of any number of interventions that help to restore or improve functions that were lost as a result of Stroke, such as the ability to walk properly, maintain posture and balance, or think, comprehend, or solve problems. These may include physical therapies, cognitive training, physical exercise, and psychosocial support. Similar to speech therapy, improvement in response to physical therapies tends to show within 3 months[12]. Certain supplements and medications may help to enhance rehabilitation by promoting Neurogenesis and Neuroplasticity, referred to as Neuromodulators.
• Dietary and Lifestyle Modifications. Wallenberg Syndrome is considered to be a type of posterior circulation ischemic stroke. The patient is often advised to make dietary and lifestyle changes that promote their recovery and limit future strokes from occurring. These include quitting smoking, regular physical activity, and consuming a balanced diet (low in refined carbs and fat) that does not increase the risk of Hypertension or Diabetes, such as the DASH or Mediterranean diets.[13] Anti-inflammatory dietary nutrients may also promote Stroke prevention by helping to regulate Neuroinflammation.
• Pharmaceutical Management. Some patients may be prescribed routine anticoagulants, antihypertensives, anti-glycemic medications, or painkillers to treat post-Stroke complications or causes.
• Stem Cell Therapy. Stem cells may greatly enhance the regeneration of blood vessels and damaged brain cells after a Stroke. Pre-clinical trials have shown that stem cell therapies promote Neurogenesis as well as help regulate Neuroinflammation that can perpetuate post-stroke damage[14]. Animal studies have shown similar efficacy for less invasive Platelet-Rich Plasma injections in models of Stroke[15] to that of highly invasive intracerebral stem cell transplantation. The effects of stem cell therapy have the potential to greatly improve the outcomes of physical rehabilitation[16], which can serve to guide the process of regeneration toward full recovery.
• Non-Invasive Brain Stimulation. Several forms of non-invasive brain stimulation have been developed over the years, all of which have shown promise in improving parameters of brain regeneration, vascular repair, cerebral blood flow, and neurologic function. Studies suggest that Transcranial Magnetic Stimulation and direct current stimulation may increase the benefit of physical rehabilitation in stroke survivors. Vagal nerve stimulation, which stimulates the brain via the Vagus nerve, has been shown to improve sensory and motor functions in Stroke patients.[17]

Prognosis

The overall prognosis for Wallenberg Syndrome is positive, with a high recovery rate.

Complications and Rehabilitation. Many patients with Wallenberg Syndrome recover within 3 - 6 months, especially with the aid of current rehabilitation strategies. Recovery from acute symptoms may be worse for patients with multiple lesions, while long-term outcomes may be worse for those with larger areas of damage in critical regions of the brainstem and cerebellum.[18]

Mortality. By comparison to other strokes of the Medulla Oblongata and posterior circulation, the Lateral Medullary Ssyndrome is not associated with a significant long-term risk of mortality. Outcomes are known to be worse for older patients, those with a history of recurrent Stroke, and those who have developed swallowing problems, which can impact both breathing and digestive function.[19]

Conclusion

Wallenberg Syndrome is one of the most common types of brainstem Stroke syndromes, primarily affecting the Vertebral Artery and sometimes the Posterior Inferior Cerebellar Artery. Acute symptoms pertain to the brainstem and cerebellar ischemia and often include dizziness, vertigo, hiccups, swallowing difficulties, and muscle weakness. Patients with Wallenberg Syndrome usually have a better prognosis than those with other brainstem stroke syndromes. After initial stabilization in the hospital, recovery usually demands restoring postural coordination, balance, speech, and swallowing ability. Speech and physical therapy are indispensable for these patients, as are classic lifestyle modifications for stroke prevention. Stem cell therapy and non-invasive brain stimulation may substantially enhance outcomes for stroke survivors in recovery.

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Sources:

• [1] https://www.ncbi.nlm.nih.gov/books/NBK470174/
• [2] https://www.world-stroke.org/assets/downloads/WSO_Global_Stroke_Fact_Sheet.pdf
• [3] https://www.ncbi.nlm.nih.gov/books/NBK538167/
• [4] https://www.ncbi.nlm.nih.gov/books/NBK551670/
• [5] https://ejnpn.springeropen.com/articles/10.1186/s41983-021-00326-z
• [6] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3271596/
• [7] https://www.sciencedirect.com/science/article/abs/pii/S1544319115318525
• [8] https://www.ninds.nih.gov/health-information/disorders/fibromuscular-dysplasia
• [9] https://www.mayoclinic.org/diseases-conditions/metabolic-syndrome/symptoms-causes/syc-20351916
• [10] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3175894/
• [11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2846331/
• [12] https://pubmed.ncbi.nlm.nih.gov/24119775/
• [13] https://www.sciencedirect.com/science/article/abs/pii/S0002962922000301
• [14] https://pubmed.ncbi.nlm.nih.gov/31381876/
• [15] https://pubmed.ncbi.nlm.nih.gov/25452023/
• [16] https://pubmed.ncbi.nlm.nih.gov/34572529/
• [17] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9724451/
• [18] https://pubmed.ncbi.nlm.nih.gov/29558752/
• [19] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7969705/

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