Regarding the diagnosis of SAH, which ONE of the following is TRUE?
Answer: A: When performed within 12 hours of the onset of symptoms, the sensitivity of non-contrast CT in detecting subarachnoid blood is up to 98%. MRI is not as sensitive as non-contrast CT in detecting acute blood in the brain. It is generally believed that a reducing number of RBCs in CSF tubes 1–4 would indicate a traumatic tap. This has not been proven. It has been reported that there could be a 25% reduction in the RBC count in successive tubes in patients with SAH. Consequently, a reducing RBC count in tubes should be interpreted with caution. Xanthochromia from a traumatic tap can develop as early as 2 hours. Otherwise, xanthochromia from SAH may take 6–12 hours to develop. Xanthochromia is due to the presence of bilirubin. Bilirubin degradation can occur when a CSF sample is exposed to light, hence less xanthochromia. It has a negative predictive value – when CT is normal, negative xanthochromia and up to a few RBCs (0–5) reliably excludes SAH. Currently, there is inadequate evidence to suggest the use of CTA as a first-line investigation for the diagnosis of SAH as there are only a few studies comparing CTA with non-contrast CT and LP for the diagnosis. CTA may detect an unruptured aneurysm and a systematic review found the risk of rupture of such an aneurysm in patients symptomatic with headache to be 8.3%.
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Regarding complications associated with Subarachnoid Haemorrhage (SAH), which ONE of the following is TRUE?
Answer: C: Cerebral vasospasm is most common in 2 days to 3 weeks. There is moderate protective benefit with nimodipine, and this should be started within 96 hours. The need for seizure prophylaxis is controversial. One in 5 patients with SAH will have at least one seizure. Delayed cerebral ischaemia is known to be associated with hyperglycaemia, hypothermia and hyperthermia. Rebleeding can be reduced by adequate BP control. Ideal target BP is unsure. Premorbid BP or MAP < 130 mmHg may be reasonable targets. Antiemetics, analgesia or IV titratable antihypertensives may be needed.
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A 56-year-old woman presents to the ED with a 2-day history of sudden onset severe headache.
Which ONE of the following findings is MOST likely to suggest Subarachnoid Haemorrhage (SAH)?
Answer: A: Usually the maximal headache in SAH occurs within a few hours (approximately 2 hours) after the onset of headache. If headache maximizes after 6 hours it is less likely to be SAH. Often the opening pressures at LP is high but normal pressure does not exclude SAH. White cells may be present if red cell count is high (1 WBC for every 500 RBC). Homogenously bloody CSF in successive tubes is more likely to occur in SAH.
A 34-year-old man presents with an ongoing moderately severe headache that had a sudden severe onset 8 days ago.
Which ONE of the following statements is TRUE regarding investigations to exclude Subarachnoid Haemorrhage (SAH)?
Answer: D: Careful selection of investigations and interpretation of results to rule out a SAH is important in a patient with a suspicious headache who presents late. The sensitivity of the CT scan to detect subarachnoid blood reduces to 50% by day 7 from the onset of symptoms. By 2 weeks most blood is reabsorbed. During this period when the initial non-contrast CT is negative it should be followed with an LP to detect xanthochromia in the CSF. Xanthochromia can result from the presence of bilirubin and oxyhaemoglobin in the CSF due to the haemoglobin degradation. Bilirubin is formed in vivo only but oxyhaemoglobin can be formed in the CSF both in vivo and in vitro. Red cells due to a traumatic tap can produce oxyhaemoglobin in vitro in case of a prolonged storage. This can be reduced by prompt transportation and centrifugation in the laboratory. This prevents the contribution of in-vitro formed oxyhaemoglobin towards xanthochromia. Traumatic taps occur in up to 15% of all LPs. Progressive reduction of RBC count in successively collected tubes (e.g. tubes 1–4) alone is not sufficient to rule out a traumatic tap because this has been shown to occur in some cases of SAH. Current opinion is when xanthochromia is negative and CSF RBC count is <5, it is sufficient to rule out SAH. When RBC count is >5, even though the xanthochromia is negative, the patient will require further evaluation to rule out SAH. CT angiography should be the next step.
Which ONE of the following clinical features is LEAST likely to be associated with an embolic stroke?
Answer: C: Embolic stroke is the result of obstruction of a cerebral arterial branch by material originating from a remote intravascular site. The common causes include: mural thrombus associated with a previous myocardial infarction, atrial fibrillation, dislodgement of fragments from valvular vegetations and atherosclerotic plaques in major arteries. Also, paradoxical embolization may occur through a patent foramen ovale. In intravenous drug users, embolic stroke may occur as a result of embolization of foreign material injected intravenously or a result of septic emboli. The symptom onset in embolic stroke is usually sudden. In thrombotic stroke, the symptoms are often of gradual onset and fluctuation of symptom severity may occur. Previous transient neurological deficits involving more than one vascular area suggests an embolic cause.
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