Lateral medullary syndrome
Synonyms and keywords: Wallenberg's syndrome; posterior inferior cerebellar artery syndrome (PICA)

# Overview
The lateral medullary syndrome is one of the most common clinical syndromes of brain stem caused by the decreased blood supply to the lateral medulla. It is also commonly known as Wallenberg's syndrome or posterior inferior cerebellar artery syndrome (PICA). The most common cause is thromboembolic occlusion of vertebral arteries. It was described in 1895. The lateral medullary syndrome is basically a manifestation of the vaso-occlusive disease of intracranial vertebral arteries (ICVA) such as vertebral artery or posterior inferior cerebellar artery. The various pathophysiologic mechanisms involved can include; atherosclerosis, athero-embolic phenomenon (heart, aorta, or vertebral arteries), dissection and increased vascular tortuosity, vascular insufficiency, Virchows triad play an important role in understanding the pathogenesis of Wallenberg's syndrome.

# Historical Perspective
- Gaspard Vieusseux, in 1808, was the first person to describe Wallenberg's syndrome.
- This syndrome was later on further elaborated by Adolf Wallenberg, in 1895.
- Thomas William was the first person to document extensive anatomy and physiology of brain stem, the cerebellum, and the ventricles in the 17th century. He performed necropsies and extensive dissections on his patient's brains.
- Joseph Jules Dejerine (18491917) and his wife  Dejerine-Klumpke demonstrated extensive visual illustrations of the various brain stem and cerebellar lesions.
- Charles Foix (18821927) was the first person to write an extensive case series on posterior cerebral arteries occlusion related syndromes and lateral medullary syndrome.
- Vertebral Basal Insufficiency (VBI) was first introduced by clinicians at the Mayo Clinic, Bob Siekert and Clark Millikan in 1970s.

# Pathophysiology
The lateral medullary syndrome is basically a manifestation of the vaso-occlusive disease of intracranial vertebral arteries (ICVA) such as vertebral artery or posterior inferior cerebellar artery. The various pathophysiologic mechanisms involved can include;
- Atherosclerosis
- Athero-embolic phenomenon (heart, aorta, or vertebral arteries)
- Dissection and increased vascular tortuosity
- Vascular insufficiency
- Virchows triad play an important role in understanding the pathogenesis of Wallenberg's syndrome
An abnormality of the intima and vascular wall
An abnormality of blood flow, and
An abnormality of blood coagulability
- An abnormality of the intima and vascular wall
- An abnormality of blood flow, and
- An abnormality of blood coagulability
Involvement of various structures in lateral medulla along with respective manifestation or clinical signs include;
- Nucleus ambiguous: dysphagia, dysphonia, and dysarthria, laryngeal, pharyngeal and palatal paralysis
- Trigeminal nucleus: ipsilateral facial and corneal anesthesia
- Spinothalamic tract: loss of pain and temperature sensation to the opposite side of the body
- Cerebellum: ataxia
- Hypothalamic fibers: sympathetic nervous system abnormal c/w Horners syndrome
- Deiters' nucleus and other vestibular nuclei: nystagmus and vertigo
- Central tegmental tract: palatal myoclonus

# Causes
- Atherosclerosis (VA>PICA>Medullary arteries)
- Embolism
- Dissection (especially in younger patients)
- Dolichoectasia
- Vasospasm

# Risk Factors
- Uncontrolled hypertension
- Smoking
- Diabetes
- Neck manipulation or injury
- Marfan syndrome
- Ehlers Danlos syndrome
- Fibromuscular dysplasia.

# Natural History, Complications and Prognosis
- The natural history, complications, and prognosis of Lateral medullary syndrome depends upon the size and location of the infarct/hemorrhagic area of the medulla.
- Some people may experience a gradual improvement in their symptoms with complete resolution of the symptoms within the week to months while others may worsen or show no improvement despite the treatment.
- Overall, the prognosis is good and most of the patients are able to return back to a normal baseline. Ataxia is seen as the most common sequelae.
- The most common complications seen are;
Aspiration pneumonia
Deep vein thrombosis
Pulmonary embolism
Myocardial infarction
- Aspiration pneumonia
- Deep vein thrombosis
- Pulmonary embolism
- Myocardial infarction

# Diagnosis

## History and Physical Examination
- Rostral lesions present as marked dysphagia and dysphonia (nucleus ambiguous)
- Caudal lesion present as vertigo, ataxia, nausea and vomiting, and Horner syndrome

### Ipsilateral (same side of lesion):
- Ageusia or loss of taste on one side of the tongue
- Ataxia or incoordination
- Diplopia or double vision
- Oscillopsia
- Dizziness
- Dysphagia or difficulties with swallowing
- Dysphonia or hoarseness
- Dysarthria or slurred speech
- Ipsilateral sensory  deficits (pain and temperature sensation) affecting the face and cranial nerves
absence of pain on the ipsilateral side of the face, as well as an absent corneal reflex (Damage to the spinal trigeminal nucleus)
- absence of pain on the ipsilateral side of the face, as well as an absent corneal reflex (Damage to the spinal trigeminal nucleus)
- Horner's syndrome
- Ipsilateral vocal fold paralysis
- Palatal and pharyngeal paresis
- Palatal myoclonus
- Hiccups
- Hoarseness
- Nystagmus
- Vertigo

### Contralateral (opposite side of lesion):
- Contralateral sensory deficits (pain and temperature sensation) affecting the trunk and extremities
- No or minimal hemiparesis

## Evaluation:

### Differential Diagnosis:
- Hemorrhagic stroke
- Multiple sclerosis
- Acute labyrinthitis
- Chronic pain syndrome
- Middle cerebral artery stroke
- Migraine headache
- Posterior reversible encephalopathy syndrome
- Subarachnoid hemorrhage
- Subdural hematoma
- Systemic lupus erythematosus

### Diagnostic Tests:
- MRI is the best diagnostic test to establish the diagnosis of Wallenberg's syndrome resulting from an infarct.
- CTA and MRA can also be done to determine the vascular occlusion sites and to rule out dissection.
- An EKG should be done to rule out any underlying thromboembolic phenomenon such as afib.

## Localization of the Lesion

# Treatment
- An interprofessional approach, aiming at a rapid response and coordinated team effort, involving neurologist, neurology specialty nurse, and the pharmacist has shown improved outcomes.
- Treatment of Wallenberg's syndrome, like other stroke management, is aimed to achieve 3 goals
Reducing the size of infarction
Preventing any medical complication
Improving patient outcome and prognosis
- Reducing the size of infarction
- Preventing any medical complication
- Improving patient outcome and prognosis
- Management includes:
IV Thrombolytics
Tissue plasminogen activator (TPA) within 3-4.5 hours
Endovascular revascularization
For larger intracranial vessels
Carotid endarterectomy
For larger extracranial vessels
Antithrombotics has a controversial role in the setting of an acute stroke but have shown improved outcomes when combined with aspirin
Oral anticoagulants and antiplatelet agents should be considered upon discharge for secondary prevention of stroke
High dose statins
Close ICU monitoring for first 24 hrs after giving TPA
Blood pressure monitoring, allow permissive hypertension and lower the BP only if,
BP > 220/120 mmHg
Patient receives IV TPA
Normal saline is preferred for IV fluids and hypotonic fluids should be avoided to prevent cerebral edema
Speech therapy to assess the risk of aspiration. A feeding tube or PEG tube may be considered for patients with severe dysphagia.
Low dose heparin or low molecular weight heparin (LWMH) for DVT prophylaxis
Physical therapy and Occupational therapy
- IV Thrombolytics
Tissue plasminogen activator (TPA) within 3-4.5 hours
- Tissue plasminogen activator (TPA) within 3-4.5 hours
- Endovascular revascularization
For larger intracranial vessels
- For larger intracranial vessels
- Carotid endarterectomy
For larger extracranial vessels
- For larger extracranial vessels
- Antithrombotics has a controversial role in the setting of an acute stroke but have shown improved outcomes when combined with aspirin
Oral anticoagulants and antiplatelet agents should be considered upon discharge for secondary prevention of stroke
- Oral anticoagulants and antiplatelet agents should be considered upon discharge for secondary prevention of stroke
- High dose statins
- Close ICU monitoring for first 24 hrs after giving TPA
Blood pressure monitoring, allow permissive hypertension and lower the BP only if,
BP > 220/120 mmHg
Patient receives IV TPA
Normal saline is preferred for IV fluids and hypotonic fluids should be avoided to prevent cerebral edema
- Blood pressure monitoring, allow permissive hypertension and lower the BP only if,
BP > 220/120 mmHg
Patient receives IV TPA
- BP > 220/120 mmHg
- Patient receives IV TPA
- Normal saline is preferred for IV fluids and hypotonic fluids should be avoided to prevent cerebral edema
- Speech therapy to assess the risk of aspiration. A feeding tube or PEG tube may be considered for patients with severe dysphagia.
- Low dose heparin or low molecular weight heparin (LWMH) for DVT prophylaxis
- Physical therapy and Occupational therapy