Unsecured MCA aneurysm with delayed cerebral ischaemia and hyponatraemia
A 58-year-old woman presents on day 0 with sudden severe headache and neck stiffness. She is WFNS grade 2 and Fisher grade 4 on CT, with diffuse subarachnoid blood and a right MCA bifurcation aneurysm measuring 7 mm, neck 5 mm, with both M2 branches incorporated. She smokes and has treated hypertension. On day 4 she becomes confused and develops new right arm weakness (MRC 4/5). TCD shows a right MCA mean velocity of 120 cm/s. Serum sodium is 128 mmol/L, urine sodium 60 mmol/L, and she is clinically euvolaemic. The aneurysm has not been secured. The unit has coiling and clipping available, but no on-site interventional neuroradiologist after 18:00. She has no fever, and CT on day 4 shows no rebleeding or hydrocephalus. Discuss the next 12 hours.
1. The aneurysm is unsecured and the patient has new weakness on day 4. How would you prioritise securing the aneurysm versus treating vasospasm?
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New confusion and arm weakness on day 4 with a Fisher grade 4 SAH and MCA velocity 120 cm/s is most likely delayed cerebral ischaemia until proven otherwise, but the aneurysm is still unsecured and the risk of rebleeding remains. I would secure the aneurysm first, within hours, because induced hypertension for vasospasm is dangerous before securing. The 7 mm MCA bifurcation aneurysm with a 5 mm neck and both M2 branches incorporated is anatomically favourable for clipping, especially after 18:00 when no interventional neuroradiologist is on site; coiling may be preferred if the neck were truly wide or branches arose from the dome, but here clipping gives durable branch preservation. After securing, I would treat vasospasm with induced hypertension guided by neurological response, maintain euvolaemia, continue oral nimodipine, and obtain CTA or DSA if deficits persist. I would not give prophylactic angioplasty or a large fluid load. The sodium of 128 needs attention but should not delay aneurysm securing; hypotonic fluids should be avoided.
2. How do you distinguish cerebral salt wasting from SIADH in this patient, and what fluid plan would you choose?
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Both cause hyponatraemia after SAH, but volume status and urine sodium differ. This patient is clinically euvolaemic with urine sodium 60 mmol/L and sodium 128; SIADH is more likely if she is euvolaemic or hypervolaemic with concentrated urine and no negative salt balance. CSW causes hypovolaemia, negative sodium balance, high urine output, and high urine sodium; it is a diagnosis of exclusion. I would check daily weights, strict input/output, serum and urine osmolality, and fractional excretion of sodium, and stop any hypotonic fluids. In SAH, the default is to avoid hypovolaemia because it worsens vasospasm. If SIADH is confirmed, I would restrict free water modestly, use isotonic saline if volume is needed, and consider fludrocortisone or hypertonic saline only for symptomatic hyponatraemia or sodium below 125 mmol/L. If CSW is present, replace salt and volume with isotonic saline. Rapid overcorrection should be avoided to prevent osmotic demyelination; the target is a rise of 8–10 mmol/L in 24 hours, not a normal sodium by morning.
3. What would you do if the patient deteriorates before the aneurysm is secured?
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If she deteriorates before securing, I would intubate and ventilate to normocapnia, maintain sedation, and obtain an urgent CT to exclude rebleeding, hydrocephalus, or infarct. If CT shows rebleeding, the priority is urgent securing, not medical vasospasm therapy; if it shows hydrocephalus, an EVD is placed with careful control of drainage to avoid aneurysmal rebleed from rapid decompression. I would not induce hypertension before the aneurysm is secured, because that can precipitate rebleeding. If the deficit is due to vasospasm and the aneurysm cannot be secured immediately, the team must weigh temporary hypertension against rebleeding risk; balloon-assisted coiling or clipping would be preferable. Dexamethasone is not routine. The sodium should be corrected slowly. The key judgement is that a new deficit in an unsecured aneurysm is not automatically vasospasm; rebleeding and hydrocephalus are the early killers, and CT plus securing the aneurysm come before aggressive hypertensive therapy.