CARDIOVASCULAR DISORDERS

Historically, neurology developed apart from general medicine and other specialties. However, it is clear that disease of any body system can cause disturbance of function in the nervous system. Neurologists, general physicians and other specialists need to be familiar with the many neurological manifestations of medical disorders. This is especially important because the complications of medical disorders include some of the most readily treatable neurological presentations. This chapter summarizes the clinical neurological manifestations of the disorders of other body systems, outlining basic elements of pathophysiology, diagnosis and management.



The neurological consequences of cardiovascular disease include stroke and transient ischaemic attack (TIA), which are considered in detail in Chapter 23. Some additional aspects relating to aortic, great vessel and spinal cord arterial diseases are considered here, as are neurological complications of cardiac surgery and some acquired cardiac diseases.



Cerebral ischaemia due to aortic disease



Aortic atherosclerosis, aortitis or aneurysm, can cause ischaemic stroke, transient ischaemic attack and hypoperfusion syndromes.



About one in 100 strokes affect the spinal cord. The most important vascular syndrome is infarction in the territory of the anterior spinal artery, with loss of pain and temperature (spinothalamic) sensation and paraparesis below the lesion; preserved vibration and joint position (carried in the dorsal columns which are supplied by the posterior spinal arteries); and loss of sphincter control. Symptoms may develop abruptly, or evolve over several hours, typically following severe, radicular-type thoracic pain at the onset.



Coronary artery bypass grafting (CABG) is still a common operation in developed countries, and peri-operative stroke occurs in up to 5 per cent of patients. A more subtle late encephalopathy may develop. These complications result from microemboli and hypoperfusion during surgery, and from postoperative atrial fibrillation. Embolism accounts for most (up to 60 per cent) cases of stroke; previous cerebrovascular disease increases the risk.



Aortic atheroma is increasingly recognized as a cause of embolism to the brain and can be well-visualized by transoesophageal echocardiography. Steal syndromes are due to stenosis of the innominate or subclavian vessels proximal to the origin of the vertebral artery, three times more often on the left than the right. Reverse flow in a vertebral artery is typically exacerbated by exercising the ipsilateral arm, thus increasing blood flow to the arm or, less commonly, by neck movement. The great majority of cases of steal are asymptomatic. The term ‘subclavian steal syndrome’ should only be used if symptoms are present; these are those of posterior circulation ischaemia including vertigo, visual disturbances and ataxia, and may respond to endovascular treatment of stenosis.



Spinal cord ischaemia due to aortic disease



The mid to lower thoracic region is most vulnerable to ischaemia. Anterior spinal infarcts are often due to aortic disease or surgery, but in about half of cases no cause is identified; there is an association with conventional vascular risk factors (hypertension, smoking, diabetes and hypercholesterolae-mia). The diagnosis of spinal infarction is clinical, although magnetic resonance imaging (MRI) usually shows signal abnormalities. Atherosclerosis, aortitis, dissection, aneurysms and coarctation can all cause spinal cord ischaemia, but generally only if the suprarenal aorta is involved.



Dissection of the thoracic aorta classically causes searing interscapular pain, hypotension and asymmetric arm pulses, with a thoracic sensory level. Cardiac or aortic surgery requiring prolonged clamping of the aorta, and aortic angiography can also cause anterior spinal infarction; the risk for suprarenal procedures is up to 10 per cent; infrarenal interventions are safer.



Aortitis can cause neurological symptoms via the development of aneurysms, aortic stenosis or atherosclerosis. Syphilitic aortitis is now rare, but typically causes aneurysms of the thoracic aorta. By contrast, atherosclerosis causes abdominal aneurysmal dilatation. Takayasu disease is a rare cause of aortitis, typically in female patients under 30; a ‘pre-pulseless phase’ with fever, weight loss, arthralgia, myalgia, night sweats and chest pain develops into the ‘pulseless phase’, in which there is occlusion of the major vessels of the aortic arch with aortic regurgitation, aneurysm formation and hypertension. Cerebral ischaemia is uncommon.



Neurological complications of cardiac surgery_



Carotid stenosis is associated with an increased risk of postoperative stroke, but this is probably because it is a marker of generalized vascular disease, rather than a direct cause. In symptomatic patients with carotid stenosis of greater than 70 per cent, intervention (carotid endarterectomy or stenting) prior to cardiac surgery is recommended. Treatment of asymptomatic carotid stenosis remains controversial and is generally avoided unless the stenosis is very severe.


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