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Economy class syndrome was first reported in 1988 and refers to an association between air travel and venous thromboembolism.1 Recently, three cases of stroke in young adults without risk factors other than a patent foramen ovale have been reported, presumably the result of paradoxical embolism.2 We now present an unusual case of medial medullary infarction caused by vertebral artery dissection associated with abnormal neck posture during a long haul flight—another health related reason to travel first class.
A 56 year old right handed insurance broker on a 7K hour economy class long haul flight returning to the United Kingdom fell asleep with his head uncomfortably twisted to the right. On waking he noticed pain in the left side of his neck and paraesthesia in the right arm. The episode resolved after 15 minutes, but recurred with a right hemiparesis affecting the arm and leg. He smoked 40 cigarettes a day and drank 24 units of alcohol a week. There was no significant past medical history and no family history of vascular disease.
On examination, conscious level, cognition, speech, and the cranial nerves were entirely normal, there was no facial weakness, and the tongue was normal. There was pyramidal weakness MRC grade 3 affecting the right arm and leg with right sided hyperreflexia and a right extensor plantar response. Joint position, vibration, and light touch sensations were normal, but pain and temperature sensation were diminished down the right side. Blood pressure was 150/90 and cardiorespiratory examination was otherwise normal. Fasting cholesterol was 5.5 mmol/l, but other routine blood tests and coagulation studies, autoantibody screen, treponemal serology, urinalysis, ECG, chest x ray, and transthoracic echocardiography were all normal.
Magnetic resonance imaging (MRI) of the brain (fig 1, panels A and B) showed signal abnormality of the left pyramid, part of the olive, and the lemniscal region of the medulla, confirmed on diffusion weighted imaging to represent an acute infarct. Doppler ultrasonography of the neck vessels was normal. Initial time-of-flight magnetic resonance angiography (MRA) showed a probable minor irregularity of the left vertebral artery in its proximal portion distal to the C2 vertebral body. Subsequent contrast enhanced magnetic resonance angiography (fig 1C) showed definite irregularity of calibre of the left vertebral artery from C2 to its junction with the basilar artery. Fat suppression axial MRI of the upper cervical spine and lower posterior fossa confirmed left vertebral artery dissection at the level of C2 and along its length to its junction with the basilar artery (ordinary T2 weighted image shown in fig 1, panel D). The patient was treated with aspirin, clopidogrel, and simvastatin. With rehabilitation he made a full recovery and was discharged home.
Medial medullary infarction accounts for less than 1% of cases of vertebrobasilar stroke and is usually thought to result from atherosclerosis of the vertebral artery, anterior spinal artery, or medullary perforating arteries.3–5 In the upper medulla the anteromedial medullary perforating arteries arise from the vertebral artery and the rostral limbs of the anterior spinal artery above their point of fusion anterior to the lower medulla. They supply the ipsilateral medial portion of the pyramidal tract, the medial lemniscus, and the medial longitudinal fasciculus, and extend dorsomedially to reach the hypoglossal nerve and central reticular formation.2,6 The distribution of the signal change in the axial T2 weighted sequence (fig 1A) corresponds exactly to the vascular territory of the anteromedial perforating branches off the left limb of the anterior spinal artery.6
Classically, medial medullary infarction, or Dejerine’s syndrome, results in contralateral hemiparesis sparing the face, with lemniscal sensory loss and ipsilesional lingual palsy. Several series have reported a greater heterogeneity of clinical features than previously documented, including nausea, vertigo, headache, somnolence, mild ipsilateral ptosis, upbeat and rotatory nystagmus, dysarthria, dysphagia, mild contralateral facial palsy, ipsilateral or contralateral decrease in sensation (most commonly pain and vibration), ipsilateral limb ataxia, and contralateral truncal lateropulsion.3–5 Dissociation of medial lemniscal sensory modes such as vibration and proprioception has also been described.5 Notably, although pain sensation is carried in the lateral lemniscal fibres, contralateral reduction in pain sensation in the arm and leg has been well documented after medial medullary infarction.3 Three main clinical pictures have emerged: sensorimotor stroke with ipsilesional lingual palsy, sensorimotor stroke without lingual palsy, as in this case, and pure motor stroke without lingual palsy. Two retrospective reviews of MRI proven medial medullary infarction reported 11 cases among 4200 (0.26%)3 and 2130 (0.52%)5 consecutive patients with ischaemic stroke. The proportion of cases of medial medullary infarction with ipsilateral lingual palsy has ranged from 11% to 64%.5
In most series, medial medullary infarction is attributed to atherothrombosis of vertebral artery, anterior spinal artery, or their medullary penetrating branches.45 Cardiovascular risk factors are usually present. Dissection of the vertebral artery leading to medial medullary infarction has only been postulated in four of over 80 cases of this condition reported previously,5 but included three of seven cases reported by Bassetti et al.4 Whatever the mechanism of occlusion of the anteromedial perforating branches of the medulla causing the medial medullary syndrome, it seems unlikely that it would often be the result of embolus from a distal site, as the branches usually arise as a series of small vessels off either the anterior spinal artery or the vertebral artery. Local occlusion of the anterior spinal artery or the vertebral artery by either dissection or atherothrombosis is a more appealing explanation. In the present case, the dissection is likely to have affected the vertebral artery along its entire distal length and to have included the origin of the anterior spinal artery. It seems probable—particularly in younger patients, and in the absence of cardiac embolism or widespread atheroma—that dissection is a more common cause of medial medullary infarction than previously acknowledged. We would therefore suggest that appropriate MRI sequences including axial images and contrast enhanced MRA of the vertebral arteries should be included in the investigation of the aetiology of medial medullary infarction. However, it may prove difficult to distinguish between dissection and atherothrombosis, especially once occlusion of the vessel has occurred.
Anticoagulation has been advocated to prevent thromboembolic complications of acute carotid or vertebral artery dissection; however, there are no reported controlled trials proving its efficacy.7 In the context of the rapid neurological recovery after initial treatment with antiplatelet agents, and in the absence of good evidence that anticoagulation started postacutely is effective, antiplatelet treatment alone was continued in the present case.
Our case adds to the literature of stroke precipitated by minor trauma, including ‘‘beauty parlour stroke’’, ‘‘bottoms up dissection’’, and hyperextension or rotation of the neck associated with chiropractic manipulations, practising yoga, painting a ceiling, prolonged telephone calls, roller coaster rides, coughing, vomiting, sneezing, routine anaesthesia, and the act of resuscitation.7 Apart from three cases recently reported of arterial stroke after air travel in association with a patent foramen ovale, presumably caused by paradoxical embolism,2 a Medline search over the last 35 years revealed only two cases of thromboembolic stroke,8 and no cases of vertebral artery or carotid dissection associated with air travel. Nevertheless, exhausted long haul passengers with cardiovascular risk factors should obviously request first class accommodation in which to fall asleep!