Lateral medullary syndrome

Lateral medullary syndrome is a neurological disorder causing a range of symptoms due to ischemia in the lateral part of the medulla oblongata in the brainstem. The ischemia is a result of a blockage most commonly in the vertebral artery or the posterior inferior cerebellar artery.

Other Names

Lateral medullary syndrome; Posterior inferior cerebellar artery syndrome; PICA syndrome

Clinical features

Wallenberg syndrome is a condition that affects the nervous system. Signs and symptoms may include swallowing difficulties, dizziness, hoarseness, nausea and vomiting, nystagmus, and problems with balance. Some people have uncontrollable hiccups, loss of pain and temperature sensation on one side of the face, and/or weakness or numbness on one side of the body. Wallenberg syndrome is often caused by a stroke in the brain stem. Treatment addresses each symptom and may include a feeding tube for swallowing problems, speech and/or swallowing therapy, and medication for pain. While some people's symptoms may improve within weeks or months, others may have long-term neurological problems.

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Clinical B1000 diffusion weighted MRI image showing an acute left sided dorsal lateral medullary infarct

Symptoms

Wallenberg syndrome may cause a variety of symptoms depending on the specific cause and the exact location of the damage to the brain.

Symptoms may include:

• pain and temperature sensory loss on one side of the face as well as on the opposite side of the body
• rapid involuntary movements of the eyes (nystagmus)
• problems with balance and gait (walking) coordination
• vomiting
• vertigo
• nystagmus
• dysphagia
• hoarseness
• uncontrollable hiccups

Horner syndrome (decreased pupil size, a drooping eyelid and decreased sweating on the affected side of the face) with visual deficits

Cause

The most common underlying cause of Wallenberg syndrome is a brain stem stroke in the vertebral or posterior inferior cerebellar arteries of the brain stem. However, several other disorders or conditions reportedly have been associated with Wallenberg syndrome, including:

• mechanical trauma to the vertebral artery in the neck
• vertebral arteritis (inflammation of the wall of the artery)
• metastatic cancer
• hematoma
• aneurysm of the vertebral artery
• herpetic brainstem encephalitis (relating to herpes)
• head injury
• arteriovenous malformations (AVMs)
• multiple sclerosis
• varicella infection
• brainstem tuberculoma (a rare form of tuberculosis)

Based on location

Features of lateral medullary syndrome

Dysfunction	Effects
Vestibular nuclei	Vestibular system: Vomiting, vertigo, nystagmus
Inferior cerebellar peduncle	Ipsilateral cerebellar signs including ataxia, dysmetria (past pointing), dysdiadochokinesia
Central tegmental tract	Palatal myoclonus
Lateral spinothalamic tract	Contralateral deficits in pain and temperature sensation from body (limbs and torso)
Spinal trigeminal nucleus & tract	Ipsilateral deficits in pain and temperature sensation from face
Nucleus ambiguus - (which affects vagus nerve and glossopharyngeal nerve) - localizing lesion (all other deficits are present in lateral pontine syndrome as well)	Ipsilateral laryngeal, pharyngeal, and palatal hemiparalysis: dysphagia, hoarseness, absent gag reflex (efferent limb—CN X)
Descending sympathetic fibers	Ipsilateral Horner's syndrome (ptosis, miosis, & anhidrosis)

Diagnosis

Since lateral medullary syndrome is often caused by a stroke, diagnosis is time dependent. Diagnosis is usually done by assessing vestibular-related symptoms in order to determine where in the medulla that the infarction has occurred. Head Impulsive Nystagmus Test of Skew (HINTS) examination of oculomotor function is often performed, along with computed tomography (CT) or magnetic resonance imaging (MRI) to assist in stroke detection. Standard stroke assessment must be done to rule out a concussion or other head trauma.

Treatment

Treatment for lateral medullary syndrome is dependent on how quickly it is identified. Treatment for lateral medullary syndrome involves focusing on relief of symptoms and active rehabilitation to help patients return to their daily activities. Many patients undergo speech therapy. Depressed mood and withdrawal from society can be seen in patients following the initial onslaught of symptoms.

In more severe cases, a feeding tube may need to be inserted through the mouth or a gastrostomy may be necessary if swallowing is impaired. In some cases, medication may be used to reduce or eliminate residual pain. Some studies have reported success in mitigating the chronic neuropathic pain associated with the syndrome with anti-epileptics such as gabapentin. Long term treatment generally involves the use of antiplatelets like aspirin or clopidogrel and statin regimen for the rest of their lives in order to minimize the risk of another stroke. Warfarin is used if atrial fibrillation is present. Other medications may be necessary in order to suppress high blood pressure and risk factors associated with strokes. A blood thinner may be prescribed to a patient in order to break up the infarction and reestablish blood flow and to try to prevent future infarctions.

One of the most unusual and difficult to treat symptoms that occur due to Wallenberg syndrome are interminable, violent hiccups. The hiccups can be so severe that patients often struggle to eat, sleep and carry on conversations. Depending on the severity of the blockage caused by the stroke, the hiccups can last for weeks. Unfortunately there are very few successful medications available to mediate the inconvenience of constant hiccups.

For dysphagia symptoms, repetitive transcranial magnetic stimulation has been shown to assist in rehabilitation. Overall, traditional stroke assessment and outcomes are used to treat patients, since lateral medullary syndrome is often caused by a stroke in the lateral medulla.

Treatment for this disorder can be disconcerting because some individuals will always have residual symptoms due to the severity of the blockage as well as the location of the infarction. Two patients may present with the same initial symptoms right after the stroke has occurred, but after several months one patient may fully recover while the other is still severely handicapped. This variation in outcome may be due to but not limited to the size of the infarction, the location of the infarction, and how much damage resulted from it.

Prognosis

The outlook for someone with lateral medullary syndrome depends upon the size and location of the area of the brain stem damaged by the stroke. Some individuals may see a decrease in their symptoms within weeks or months. Others may be left with significant neurological disabilities for years after the initial symptoms appeared.

See also

• Alternating hemiplegia of childhood
• Benedikt syndrome
• Lateral pontine syndrome
• Medial medullary syndrome
• Weber's syndrome

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