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Pulmonary oedema is a well recognized complication of various neurological disorders but has seldom been reported in multiple sclerosis.
A previously healthy woman of 46 became acutely dyspnoeic, without chest pain or palpitations. Two days earlier she had noted mild ankle swelling. On admission, heart rate was 110/min, respiratory rate 25/min and blood pressure 100/60 mmHg. A 12-lead electrocardiogram (ECG) showed ST depression in the lateral chest leads but no Q-waves or other evidence of acute myocardial infarction. A chest X-ray revealed generalized pulmonary oedema with bilateral small pleural effusions (Figure 1). There was no evidence of infection and a ventilation-perfusion scan was normal. An echocardiogram showed an akinetic intraventricular septum and anterior left ventricle wall with ejection fraction (EF) 39%. There was a small posterior pericardial effusion. It was noted that the basal and anterior wall impairment did not conform with standard coronary anatomy. Believed to be in cardiogenic shock, she was transferred to Harefield Hospital in case mechanical circulatory support became necessary.
With intravenous inotropes and diuretics her condition improved; an angiotensin converting-enzyme inhibitor was introduced and the inotropic support was gradually tapered off. A coronary angiogram demonstrated normal coronary vasculature. Clinically, she made an excellent recovery, and myocardial recovery was likewise rapid: six days after the initial echocardiogram the EF had risen to 55% and on discharge 3 weeks later it was 69%.
While in hospital, the patient complained of a constant tingling in both hands and intermittent slurring of speech. She had no numbness or weakness and there was no reported visual or sphincter disturbance. On further inquiry she revealed that, in the week before admission, she had had an episode of visual disturbance: when driving, everything had appeared to be ‘moving up and down’. The effect was binocular and not affected by the direction of gaze. After two days this had subsided spontaneously. She also recalled neurological symptoms 10 years previously. She had woken one morning with weakness in the left arm and leg and poor coordination which caused her to fall over twice. At that time her leg and arm, but not her face, were numb and her speech was slurred as now. The symptoms resolved over a few days. Visual evoked potentials (VEPs) and a CT brain study were normal. 2 years before the current admission she had had paroxysms of head pain radiating to her left arm and associated with slurred speech but no limb weakness. More recently she had complained of similar pains in the right side of the head for several months. There was no history of Lhermitte's phenomenon.
On neurological examination there were no objective abnormalities. Routine blood and biochemistry results were normal. The VEPs were still within normal limits but the cerebrospinal fluid (CSF) showed oligoclonal bands which were not matched in serum. An MRI brain study showed diffuse periventricular white matter changes consistent with multiple sclerosis. There were similar lesions in the brainstem and cerebellum (Figure 2) and in particular there was a large enhancing lesion in the medulla, in the region of the nucleus tractus solitarius.
The neurological conditions that can be complicated by pulmonary oedema include subarachnoid haemorrhage, seizures, head injury, stroke, bulbar poliomyelitis and acute hydrocephalus1,2. There are few case studies of pulmonary oedema in patients with brainstem demyelination. Melin et al.2 reviewed the published work and noted that the pulmonary oedema was commonly preceded (by some weeks) by diffuse brainstem neurological symptoms such as dizziness, ataxia and paraesthesia. In one report the patient, like ours, had a preceding episode of oscillopsia. ECG findings are variable and non-specific although intermittent atrial fibrillation has been described3. Echocardiographic indices, when reported, have been judged normal, though patients were studied after the abnormal findings had largely resolved3,4. Similarly with MRI, few studies have been performed in the acute stage of disease1.
What is the mechanism of neurogenic pulmonary oedema? One theory is that lesions in the preoptic hypothalamus, or diffuse intracranial hypertension, affect the medullary autonomic pathways, inducing bradycardia and hypertension5,6; MRI studies suggest an area in or near the nucleus of tractus solitarius (NTS) as the more likely origin1. A lesion in the caudal medulla adjacent to the obex has been described in two patients with multiple sclerosis and pulmonary oedema1,2. The authors point out that efferent signals from the NTS terminate in the thoracic spinal cord and that lesions of the NTS in laboratory animals have generated increases in pulmonary arterial pressure in the absence of a rise in systemic and left atrial pressures. Increased intravascular pressures in the lung, they speculate, would result in unbalanced precardiac and postcardiac loads, leading to fluid movement into the alveolar spaces. In the largest single series of patients in which pulmonary oedema fluid was evaluated, the primary mechanism was believed to be hydrostatic7. This contrasts with a previously suggested mechanism of increased pulmonary capillary permeability8,9. The lesion in the region of the NTS in the medulla of our patient supports the idea that this is the key site. But in addition, at least part of the mechanism was the left ventricular dysfunction and a consequent rise in pulmonary capillary wedge pressure.
Initially we thought that our patient might be having multiple cerebrovascular episodes, so we started her on warfarin and arranged a coronary angiogram. A CT scan was uninformative. It was early MR imaging that yielded the diagnosis.