Wallenberg syndrome, also known as lateral medullary syndrome, is one of the most well-known neurological syndromes affecting the brainstem. It occurs when a lesion disrupts blood flow to the lateral region of the medulla oblongata, usually as a result of an ischemic stroke.
Its characteristic combination of sensory disturbances, balance problems, and difficulty swallowing allows relatively precise localization of the lesion.
What is Wallenberg syndrome?
Wallenberg syndrome is a neurological disorder caused by an infarction affecting the lateral region of the medulla oblongata.
It was described by the German neurologist Adolf Wallenberg and is one of the most common crossed brainstem syndromes.
The lesion affects several important structures, including:
- Vestibular nuclei.
- Nucleus ambiguus.
- Spinothalamic tract.
- Spinal trigeminal nucleus.
- Inferior cerebellar peduncle.
- Descending sympathetic fibers.
Simultaneous involvement of these structures accounts for the wide range of symptoms that may occur.
Where is the lesion located?
The lesion is located in the lateral portion of the medulla oblongata, a region involved in essential functions such as:
- Balance.
- Coordination.
- Swallowing.
- Facial sensation.
- Processing of pain and temperature.
Due to this location, the syndrome causes symptoms affecting both the face and the rest of the body.
What is the most common cause?
Most cases are caused by occlusion of the posterior inferior cerebellar artery (PICA) or the vertebral artery, which supply this region of the brainstem.
The most common causes include:
- Ischemic stroke.
- Vertebral artery dissection.
- Atherosclerosis.
- Embolism.
- Small vessel disease.
Less commonly, the syndrome may occur as a result of hemorrhage, tumors, or inflammatory processes.
Symptoms of Wallenberg syndrome
Symptoms usually have a sudden onset when the underlying cause is vascular.
Severe vertigo
One of the most common initial symptoms is:
- A spinning sensation.
- Nausea.
- Vomiting.
- Difficulty standing.
These manifestations result from involvement of the vestibular nuclei.
Balance problems
Involvement of the inferior cerebellar peduncle causes:
- Ataxia.
- Unsteady gait.
- Difficulty coordinating movements.
- A tendency to veer to one side while walking.
Difficulty swallowing
When the nucleus ambiguus is affected, the following symptoms may occur:
- Dysphagia.
- Dysarthria.
- Hoarseness.
- Difficulty coughing effectively.
These symptoms are particularly characteristic of Wallenberg syndrome.
Sensory disturbances
A crossed sensory pattern is commonly observed:
On the face, ipsilateral to the lesion:
- Reduced pain sensation.
- Reduced temperature sensation.
On the contralateral side of the body:
- Loss of pain sensation.
- Reduced temperature sensation.
This pattern is one of the most useful findings during neurological examination.
Horner syndrome
Damage to the descending sympathetic fibers may cause:
- Drooping of the eyelid (ptosis).
- Constriction of the pupil (miosis).
- Reduced sweating on one side of the face.
Not all patients present with this complete set of symptoms, but when present, it can help confirm the location of the lesion.
Other possible symptoms
Depending on the size of the infarction, other symptoms may also occur:
- Persistent hiccups.
- Abnormal eye movements.
- Nystagmus.
- Taste disturbances.
- Fatigue while walking.
Muscle strength is usually relatively preserved, as the corticospinal tract is generally not affected.
How is it diagnosed?
Diagnosis is based on neurological examination and imaging studies.
Brain magnetic resonance imaging (MRI) can identify the infarction in most cases, particularly using diffusion-weighted imaging (DWI).
Additional tests may include:
- Magnetic resonance angiography (MRA).
- Computed tomography angiography (CTA).
- Computed tomography (CT).
- Vascular imaging of the vertebral arteries.
The characteristic clinical pattern often helps guide the diagnosis even before imaging results are available.
Differences from other brainstem syndromes
Wallenberg syndrome may be confused with other neurological syndromes affecting the brainstem, although it has its own distinctive features.
These include:
Dejerine syndrome
It causes:
- Weakness on the contralateral side of the body.
- Paralysis of the tongue.
- Impairment of deep sensation.
Claude syndrome
Weber syndrome
Predominant features include:
- Oculomotor nerve palsy.
- Contralateral hemiplegia.
The precise location of the lesion determines which neural structures are affected and, consequently, which symptoms occur.
Clinical course and prognosis
The clinical course depends on factors such as:
- The size of the infarction.
- The timeliness of diagnosis.
- The patient’s age.
- The presence of other vascular conditions.
Many patients experience gradual improvement in balance and coordination during the following months, although some swallowing or sensory disturbances may persist for longer periods.
Rehabilitation
Rehabilitation is usually tailored to each individual’s specific deficits and includes different areas of treatment.
The most common interventions include:
- Physiotherapy to improve gait and balance.
- Occupational therapy to restore functional independence in daily activities.
- Speech and language therapy to address dysphagia and dysarthria.
- Exercises aimed at improving coordination.
Recovery is usually gradual and requires ongoing follow-up by a multidisciplinary team.
Conclusion
Wallenberg syndrome is a neurological syndrome usually caused by an infarction in the lateral region of the medulla oblongata. The combination of vertigo, balance disturbances, difficulty swallowing, sensory loss, and Horner syndrome constitutes a highly characteristic clinical pattern that helps localize the lesion within the brainstem. Early recognition of these signs is essential for guiding diagnosis and planning the most appropriate rehabilitation.
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