RIGHT -SIDED LATERAL MEDULLARY STROKE

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Figure 1.
A 34-year-old woman presents to the emergency department (ED) with a 3-day history of pain around the right ear extending to the temple. She was sitting at work today when she suddenly experienced dizziness, a feeling of discomfort in the throat, and a burning sensation in the left arm and leg. When she tried to stand and walk, her right arm and leg did not move in a normal, coordinated manner. The patient was previously healthy and does not take any regular medications. She does not smoke or drink. She does vigorous aerobic exercises on an almost daily basis. Her mother and a number of relatives on her mother's side suffer from hypertension.
On physical examination, the patient has an oral temperature of 98.6°F (37.0°C). Her pulse is regular with a rate of 86 bpm. Her blood pressure is 164/90 mm Hg, and her heart sounds are normal and without added sounds. There are no arterial bruits auscultated in her neck. She is noted to have prolonged bouts of hiccuping. She is unable to stand due to a severe feeling of imbalance. There is right-sided ptosis and miosis. She has a sustained horizontal gaze-evoked nystagmus looking to the left and right, with a downbeating nystagmus on downward gaze. There is decreased sensation of pinprick and temperature on the right side of the face. On the right side there is also reduced movement of the palate, and the gag reflex is diminished. The tongue movements are normal. The power is normal in all 4 limbs, the deep tendon reflexes are normal, and the plantar responses are downgoing bilaterally (there is no Babinski sign). There is a moderate degree of ataxia affecting the right arm and leg. There is decreased sensation to pinprick and temperature on the left arm, leg, and trunk. The joint position and vibration sense are intact bilaterally.
Routine laboratory analysis, including a complete blood cell count, a basic metabolic panel, and a lipid profile, is normal. A noncontrast computed tomography (CT) scan of the head is normal. Magnetic resonance imaging (MRI) of the brain is obtained.The patient in this case was diagnosed with a lateral medullary stroke on the right with Wallenberg syndrome.
Neurons relaying pain and temperature sensation from the right side of the face synapse in the descending spinal nucleus of the trigeminal nerve, which lies in the dorsolateral aspect of the brainstem (Figure 2). Thereafter, the pathway crosses (as the quintothalamic tracts) and ascends to the thalamus. For the limbs and trunk, the neurons of the spinothalamic tract from the left side of the body pass into the spinal cord, where they ascend for 1 or 2 levels (via Lissauer's tract) and then synapse. The second-order neurons then cross to the right side of the spinal cord (via the anterior commissure, just anterior to the central canal of the cord) and then ascend in the anterolateral aspect of the spinal cord up into the right side of the brainstem. In the brainstem, the spinothalamic tract lies laterally.
This patient had impairment of pain and temperature (ie, spinothalamic) sensation on the right side of the face and the left side of the body. These contralateral findings are characteristic of a right lateral medullary lesion. The patient also had reduced palatal movements and gag reflex on the right side indicative of involvement of the right IX (glossopharyngeal) and X (vagus) cranial nerves. These cranial nerves, as well as the descending sympathetic fibers (patient had a right-sided Horner's sign), are also found in the dorsolateral aspect of the right side of the medulla (Figure 2). The presence of vertigo and right-sided ataxia was due to involvement of the vestibular nucleus and cerebellar pathways (as they pass into the cerebellum through the inferior cerebellar peduncle), respectively, on the right side. The nucleus and the fascicles of the hypoglossal nerve lie medially within the medulla, and the pyramidal pathways lie anteromedially as they pass through the medulla. The joint position and vibration sense modalities pass up the spinal cord on the ipsilateral side and then synapse at the gracile and cuneate nuclei in the lower part of the medulla. The dorsal column pathways then cross (as the internal arcuate fibres) at the level of the lower medulla and then pass up the medial aspect of the brainstem as the medial lemnisci. The normal tongue movements and the preserved pyramidal and dorsal column function in this patient indicate that there is sparing of the medial medulla; therefore, this patient had a right-sided lateral medullary syndrome (ie, Wallenberg syndrome), which was determined by brain MRI to be a stroke. The T2-weighted coronal scan shows a high signal abnormality in the right side of the medulla (black arrow, Figure 1).
The presence of prominent right ear pain for 3 days prior to developing neurologic deficits is suggestive of a vertebral artery dissection. In fact, stroke preceded by headache or neck pain should always raise suspicion for cervical arterial dissection. The patient performed vigorous aerobic exercises on an almost daily basis, and these exercises included repetitive high-energy lateral neck flexions. This is likely to have been the cause of an arterial dissection. The diagnosis made was of a dissection of the right vertebral artery and a subsequent infarction of the dorsolateral aspect of the right medulla.
The lateral medullary syndrome (also called Wallenberg or posterior inferior cerebellar artery [PICA] syndrome) was first described by Gaspard Vieusseux in 1808. Subsequent clinical (1895) and autopsy (1901) descriptions by Wallenberg led to the syndrome being associated with his name. The loss of pain and temperature sensation on the ipsilateral side of the face and contralateral side of the body is characteristic of this condition. Other clinical features include intractable hiccups, vertigo, Horner syndrome, nystagmus, dysarthria, dysphagia, and ipsilateral ataxia. The blood supply to the medulla is mainly from the vertebral arteries. At the level of the lower medulla, each vertebral artery gives off a variable branch named the posterior inferior cerebellar artery (which may be absent in up to 25% of the population) that supplies the dorsolateral aspects of the medulla. At a higher level, approaching the pontomedullary junction, each vertebral artery also contributes branches to form the anterior spinal artery, which descends over the anterior surface of the medulla and supplies the medial aspects of the medulla. The majority of cases of Wallenberg syndrome are therefore due to vascular events, whereby the dorsolateral aspect of the medulla may be involved, with sparing of the medial medulla due to an intact anterior spinal artery supply. Definitive pathologic[1] and more recent MRI[2] studies indicate that lateral medullary infarctions occur due to involvement of the vertebral artery in 38% of cases. PICA is involved 14%-24% of the time, and both arteries are involved in 26% of cases. No abnormality is found in either vessel only 12%-19% of the time.
Intravenous thrombolysis (IVT) is an acute treatment of the lateral medullary syndrome. Although still very controversial, some studies show that IVT using recombinant tissue plasminogen activator (tPA) is efficacious for acute ischemic stroke.[3] Dissection is not an absolute contraindication to IVT; however, if a vertebral artery dissection extends intracranially (which is uncommon), caution is advised due to an increased risk for bleeding. The ECASS 3 trial recently demonstrated benefit of IVT given up to 4.5 hours after symptom onset in ischemic stroke, although certain patients were excluded from this trial and this practice is not standard of care.[4] Newer, invasive stent-based techniques exist for stroke and dissection treatment, though they are available at very few centers. If a patient with a nonhemorrhagic stroke is seen beyond the time window for IVT, then aspirin may be given. In this case, because there was a vertebral artery dissection, anticoagulation with heparin and subsequently warfarin was indicated.
The mechanism of the intractable hiccups that is often observed in the lateral medullary syndrome is poorly understood. Occasionally, gabapentin or chlorpromazine is effective. Patients may experience disturbed vision due to persistent nystagmus, and this may be helped by gabapentin or memantine.[5]
Cervical artery dissections (CADs) may involve the carotid or vertebral arteries. They are implicated in 2% of all ischemic strokes but in up to 10%-25% of cases in young and middle-aged patients. CAD may occur spontaneously, and several inheritable connective tissue disorders (eg, Ehlers-Danlos syndrome type IV, Marfan syndrome, autosomal dominant polycystic kidney disease, and osteogenesis imperfecta) are associated with an increased risk. Familial arterial dissections have been associated with generalized lentiginosis, coarctation of the aorta, bicuspid aortic valve, and aortic root dilatation. Traumatic CAD occurs most frequently following motor vehicle accidents. Less violent forms of trauma have also been implicated in CAD, especially cervical spine chiropractic manipulations. Other forms of trauma implicated in CAD include contact sports, yoga, calisthenics, vigorous aerobic exercise, ceiling painting, tonic-clonic seizures, and riding on roller coasters. The mechanism of stroke in CAD is usually thromboembolic due to disruption of normal blood flow in the region of dissection. Less commonly, there may be partial or total occlusion of the vessel, which then results in low blood flow and watershed ischemia. The presence of a CAD may be confirmed by formal cerebral angiography, but less invasive procedures such as MR angiography, CT angiography, or duplex Doppler studies are diagnostic in a high proportion of patients.
The patient in this case presented acutely to the ED, had a normal CT head scan, and was within the time window to receive treatment with IVT. She was given 0.9 mg/kg of recombinant tPA intravenously 3 hours and 15 minutes after the onset of her stroke. She remained well, and 24 hours later she was started on oral aspirin therapy. Her intractable hiccups were treated with oral chlorpromazine and resolved after 2 weeks. Because she was experiencing an intrusive burning sensation affecting the left side of her body as well as disturbed vision due to persistent nystagmus, she was started on gabapentin therapy. Both of these symptoms were controlled well with gabapentin at 1800 mg per day. The patient's dysphagia and right-sided limb ataxia improved such that she was able to eat a normal diet and walk within 1 week of hospital admission. The patient was discharged to home and was able to return to her employment as an accountant 10 weeks after her stroke.You are seeing a patient in whom you suspect a brainstem stroke due to a vertebral artery dissection. Which of the following investigations is most appropriate after an initial noncontrast CT scan of the head?
MRI studies are considered the noninvasive imaging modality of choice in this situation. CT angiography is also acceptable but will not identify the stroke. The images obtained from the MRI scan of the head may directly detect the pathologic lesion. In the patient presented in the case, the T1-weighted and fluid-attenuated inversion recovery (FLAIR) sequences of the MRI showed a bright signal across the right vertebral artery wall. It also demonstrated the right lateral medullary infarction. These features are highly suggestive of fresh blood and/or recent thrombus throughout the vessel wall seen in arterial dissection. Conditions associated with an arterial dissection may be demonstrated by an echocardiogram and appropriate genetic testing (eg, for Marfan syndrome) but will not help in confirming the presence of an arterial dissection. A lumbar puncture has no role in stroke or dissection evaluation.
The patient described above is found to have a vertebral artery dissection and stroke with Wallenberg syndrome. Which symptom or sign would you expect to find in this patient?The loss of pain and temperature sensation on the ipsilateral side of the face and contralateral side of the body is characteristic of Wallenberg syndrome. Other clinical features include intractable hiccups, vertigo, Horner syndrome, nystagmus, dysarthria, dysphagia and ipsilateral ataxia.