Lateral medullary syndrome (LMS), also called Wallenberg syndrome or posterior inferior cerebellar artery syndrome results from a vascular event in the lateral part of the medulla oblongata. It was named after Adolf Wallenberg (1862-1949), who was a renowned Jewish neurologist and neuroanatomist who practiced in Germany. He first reported the case of LMS. The arteries commonly involved in LMS are the posterior inferior cerebellar artery (PICA) or the vertebral artery. Lateral medullary syndrome characteristically has varied neurologic manifestations. The damage is to the inferior cerebellar peduncle and dorsolateral medulla, descending spinal tract, the nucleus of the trigeminal nerve, nuclei, and fibers of the vagus nerves and glossopharyngeal, descending sympathetic tract fibers, spinothalamic tract, and vestibular nuclei.
Etiology of the lateral medullary syndrome include:
Posterior circulation strokes represent about 20% of all ischemic strokes. Lateral medullary infarcts occur more frequently in those who consume alcohol. Moreover, in a study, angiograms show that it is more common with vertebral artery disease (67%) as compared to posterior inferior cerebellar artery disease (10%). Also, PICA disease was seen to be more frequently related to cardiogenic embolism as compared to other causes. Between 51% and 94% of the patients with lateral medullary syndrome experience some degree of swallowing difficulty.
Pathological processes for the development of lateral medullary syndrome include large-vessel infarction (50%), arterial dissection (15%), small vessel infarct (13%), and cardioembolism (5%).
Dysphagia in LMS involves a lack of coordination in pharyngeal and esophageal phases of swallowing. Dysphagia is due to the involvement of swallowing centers in the dorsolateral medulla oblongata. These include the nucleus ambiguous and nucleus tractus solitarius and the reticular formation.
Hiccups are also a clinical feature of the lateral medullary syndrome. The neural structures related to hiccups are unknown, but nucleus ambiguus or adjacent areas that are involved in regulating respiration may have involvement in the generation of the hiccup.
Hyponatremia after a brain injury occurs due to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and cerebral salt wasting syndrome. Reports exist of SIADH in patients with lateral medullary infarction. The proposed pathophysiology includes the failure of propagation of non-osmotic stimuli from the carotid sinus through vagal nerve due to the nucleus tractus solitarius lesion in the medulla. This results in the disinhibition of antidiuretic hormone (ADH) secretion by the pituitary gland causing SIADH.
Spinothalamic tract - Contralateral impairment of pain and temperature in trunk and limbs
Trigeminal nerve (V) - Ipsilateral loss of pain and temperature on the face
Vestibular nucleus - Ipsilateral nystagmus, vertigo, nausea, and vomiting
Descending Sympathetic - Ipsilateral Horner syndrome
Cerebellum - Ipsilateral gait ataxia
Glossopharyngeal (IX) - Ipsilateral absent gag reflex and hoarseness
Vagus nerve (X) - Ipsilateral/ deficit of reflex cough test
Trigeminal nerve (V) - Trismus due to masseter and temporalis hyper contraction
The usual symptoms of lateral medullary infarction include vertigo, dizziness, nystagmus, ataxia, nausea and vomiting, dysphagia, and hiccups. Dysphagia is more profound in lateral medullary syndrome patients. Nevertheless, the manifestation is broad and includes dysphonia, facial pain, visual disturbance, and headaches. There is:
Study shows that the onset of the lateral medullary syndrome is sudden in 75% of patients and gradual in 25% of patients. Sensory signs and symptoms are the most frequent manifestations (96%). Less common clinical presentation includes facial paresis, dysarthria, and eye pathologies such as skew deviation, diplopia, and gaze deviation. Among those with gradual onset, patients usually first have headaches, vertigo, dizziness, or gait ataxia, while sensory clinical features, dysphagia, hoarseness, and hiccups usually occur later.
Patients with lateral medullary syndrome show conjugate deviation of eyes towards the side of the lateral medullary infarct. Various types of eye problems correlate with LMS. These are nystagmus, gaze-evoked nystagmus, skew deviation, and ipsipulsion. Among these, ipsipulsion is more specific to LMS.
Evaluation should include a detailed clinical history, physical exam, and appropriate testing, including:
Computed tomography (CT) scan of the brain: Brain CT is typically the initial imaging test for lateral medullary syndrome patients. CT gives suboptimal visualization of the posterior fossa structures due to obscuration by artifacts (bony structures), and early ischemic changes may not be visible.
Brain magnetic resonance imaging (MRI): MRI provides better visualization of the soft tissue structures as compared to CT scan. MRI aids in diagnosis by improved visualization of the medullary infarction. For example, by the use of imaging protocol fluid attenuation inversion recovery sequences (FLAIR) in the evaluation of infarction.
Diffusion-weighted magnetic resonance imaging (DWI): can detect infarct early.
Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) examination are advanced imaging studies. They identify the exact location of the lesion.
Management includes resuscitation and intensive care unit monitoring. Respiratory failure should remain in mind, and patients followed in the intensive care unit.
Patients should have clinically monitoring for signs of increased intracranial pressure. These include disorientation, lethargy, headache, vomiting. Look for bradycardia, hypertension, or irregular respiratory pattern. Management includes head elevation to 30 degrees, blood-pressure management to maintain cerebral perfusion, hyperventilation, osmotherapy, and sedation. Surgery may be a consideration.
Reperfusion/Thrombolytic therapy: Intravenous thrombolysis with IV recombinant tissue-plasminogen activator (IV-rt-PA), and endovascular thrombectomy may be an option.
Secondary stroke prevention: With antiplatelets, antihypertensives, and statins. Treatment of the cause and vascular risk factors.
Evaluation of enteral nutrition: Patients may require a nasogastric tube.
Dysphagia management: Dietary and/or postural modifications are required. If severe dysphagia is prolonged, conversion to percutaneous endoscopic gastrostomy (PEG) may be required. Swallowing treatment: Active exercises to strengthen swallowing musculature. Botulinum toxin type-A injections have been used to treat severe dysphagia associated with trismus.
Low-molecular-weight heparin prophylaxis of deep vein thrombosis.
Speech therapy assessment
Hiccups: There are reports of the use of gabapentin in the treatment of persistent hiccups in cases of LMS.
Medullary infarction can cause autonomic abnormalities leading to acute heart failure. A pacemaker may be required.
Keratitis in LMS can occur due to loss of corneal sensitivity caused by trigeminal neuropathy leading to epithelial erosions. These patients need multidisciplinary management, artificial tears, night creams, autologous serum, and rarely surgical procedures.
The lateral medullary syndrome may cause chronic disabling facial pain. Gabapentin is an option for these patients.
Periodic follow up of the patient to evaluate speech and motor activity.
Lateral medullary syndrome patients require physical and occupational therapy until they gradually develop their physical strength. Patients should be aware of secondary stroke prevention strategies. Those with dysphagia should go through dysphagia rehabilitation. Severe dysphagia cases may require a gastrostomy tube. Regular follow up is necessary for a speech evaluation.
Lateral medullary syndrome management requires an interprofessional therapeutic approach. Healthcare professionals should focus on stroke prevention. These include control of risk factors such as smoking and hypertension. Additionally, blood pressure-lowering medication, antithrombotic therapy, and statins are required. Physiotherapy is an essential cornerstone in the management of LMS patients. Inpatient rehabilitation is also necessary. Speech and occupational therapy are crucial for daily living activities. Patients who are not able to swallow my need to see a dietitian. Some patients may need a temporary feeding tube. Long term follow-up is necessary by a neurology nurse to ensure that the patient is recovering. The social worker should be consulted to ensure that the patient's home environment is safe, and there are support services available. Some patients may have had a severe stroke, and the end of life committee should speak to the caregiver about future decisions regarding care. Patients should be followed up by the interprofessional team after hospital discharge until they improve functionally.
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