What are the effects of a lesion in the lateral medulla (lateral medullary syndrome)?

From the Guidelines

The lateral medullary syndrome, also known as Wallenberg syndrome, is typically caused by occlusion of the posterior inferior cerebellar artery (PICA) or vertebral artery, resulting in a lesion in the lateral part of the medulla oblongata, and its management should focus on treating the underlying cause, typically with antiplatelet therapy or anticoagulation for ischemic events, along with supportive care for specific symptoms 1. The lateral medullary syndrome affects several important structures including the vestibular nuclei, inferior cerebellar peduncle, nucleus ambiguus, spinal trigeminal nucleus and tract, sympathetic fibers, and spinothalamic tract. Some key points to consider in the management of lateral medullary syndrome include:

• The classic clinical presentation includes ipsilateral facial sensory loss, ipsilateral cerebellar signs (ataxia, dysmetria), ipsilateral Horner's syndrome (ptosis, miosis, anhidrosis), ipsilateral palatal weakness causing dysphagia and dysarthria, and contralateral loss of pain and temperature sensation in the body.
• Patients may also experience vertigo, nausea, vomiting, and hiccups.
• Rehabilitation including speech therapy for swallowing difficulties and physical therapy for ataxia is often necessary.
• The prognosis varies, with many patients experiencing improvement over time, though some deficits may persist, as noted in the acr appropriateness criteria® cranial neuropathy: 2022 update 1. It is essential to tailor imaging protocols to evaluate the suspected region of anatomy affected, and a thorough neurologic examination evaluating for associated signs such as long tract signs, nystagmus, vertigo, ataxia, nausea, and vomiting can help localize a process to the brainstem 1.

From the Research

Clinical Presentation of Lateral Medullary Syndrome

• The syndrome is characterized by damage to the corresponding cranial nerve nuclei and the nucleus tractus solitarius, with symptoms including vertigo, ipsilateral ataxia, crossed sensory disturbances, Horner's sign, bulbar palsy, and other underlying symptoms or signs 2.
• Patients with lateral medullary syndrome classically present with crossed hemisensory disturbance, ipsilateral Horner syndrome, and cerebellar signs, all of which are attributable to infarction of the lateral medulla 3.
• The most pathognomonic symptoms of LMS include pain and temperature deficits on ipsilateral facial side and contralateral side of rest of the body, ipsilateral ataxia, vertigo, nystagmus, dysphagia, hoarseness, hiccups, and Horner's syndrome 4.

Causes and Risk Factors

• Lateral medullary syndrome is the most common type of brainstem infarction, often caused by thrombosis, embolization, or dissection of vertebral or posterior inferior cerebellar artery (PICA) 3, 4.
• In younger patients, vertebral artery dissection is the most common cause of lateral medullary syndrome 2.
• Stroke is the most common cause of LMS, which may result from a failure in either the vertebral artery or the posterior inferior cerebellar artery 5.

Diagnosis and Management

• Clinical management of patients with lateral medullary syndrome should be prioritized, with close cardiac monitoring at the early stages of observation and pacemaker placement and tracheal intubation as required to prevent adverse events 2.
• An approach to diagnosis and management of the lateral medullary syndrome should integrate clinical information with an understanding of brainstem anatomy to determine which patients require urgent neuroimaging and acute stroke therapies 3.
• Rehabilitation and physiotherapy action strategies, including chest physiotherapy and a four-week physiotherapy program, can help improve the patient's condition and achieve bronchial hygiene 5.

Complications and Prognosis

• Dysphagia is a common clinical feature of lateral medullary syndrome and is clinically relevant because it is related to aspiration pneumonia, malnutrition, increased mortality, and prolonged hospital stay 6.
• Patients with lateral medullary syndrome may suffer from life-threatening arrhythmia and even cardiac arrest, and vital signs should be closely monitored to prevent sudden death 2.
• With optimal therapy, the prognosis for recovery from lateral medullary syndrome is good, and most patients with dysphagia in LMS have a relatively good prognosis 3, 6.