SAQ 249 – Neurology – Ottawa SAH rule and early CT

Question 2. Ottawa SAH rule and early CT.

a. Application requirements

• Alert patient.
• Age over 15 years.
• New headache.
• Severe headache.
• Non-traumatic headache.
• Maximum intensity reached within one hour.

b. Exclusion criteria

• New neurological deficit.
• Previous aneurysm.
• Previous subarachnoid haemorrhage.
• Previous brain tumour.
• Recurrent headache history, defined as at least three similar episodes over at least six months.

c. High-risk variables

• Age 40 years or older.
• Neck pain or stiffness.
• Witnessed loss of consciousness.
• Onset during exertion.
• Thunderclap headache with instant peak intensity.
• Limited neck flexion on examination.

d. Negative CT brain alone

• Patient is alert with GCS 15.
• Headache is non-traumatic.
• Headache reached peak intensity within one hour.
• CT is performed within six hours of onset.
• CT is interpreted as normal by an experienced consultant or neuroradiologist.