1. The differential for thunderclap headaches Neurology Resident Teaching Series

2. -itis ----- inflammation -oma ----- mass effect -emia ----- vascular Other -itis, -oma, -emia

3. -itis CNS vasculitis -oma Colloid cyst (third ventricle) Pituitary apoplexy -emia Cervical artery dissection Cerebral venous sinus thrombosis Hypertensive encephalopathy Subarachnoid hemorrhage or Sentinel hemorrhage Reversible cerebral vasoconstriction syndrome Other Migraine Primary thunderclap headache Spontaneous intracranial hypotension -itis, -oma, -emia

4. -itis CNS vasculitis -oma Colloid cyst (third ventricle) Pituitary apoplexy -emia Cervical artery dissection Cerebral venous sinus thrombosis Hypertensive encephalopathy Subarachnoid hemorrhage or Sentinel hemorrhage Reversible cerebral vasoconstriction syndrome Other Migraine Primary thunderclap headache Spontaneous intracranial hypotension permanent neurologic deficit

5. -itis CNS vasculitis -oma Colloid cyst (third ventricle) Pituitary apoplexy -emia Cervical artery dissection Cerebral venous sinus thrombosis Hypertensive encephalopathy Subarachnoid hemorrhage or Sentinel hemorrhage Reversible cerebral vasoconstriction syndrome Other Migraine Primary thunderclap headache Spontaneous intracranial hypotension sudden or rapid death

6. -itis CNS vasculitis ----- CT, MR, or conventional angiography, +/- brain biopsy -oma Colloid cyst (third ventricle) ----- CT or MRI Head (third ventricle cyst, lateral ventricle dilation) Pituitary apoplexy ----- CT or MRI Head (hemorrhage) -emia Cervical artery dissection ----- CT, MR, or conventional angiography Cerebral venous sinus thrombosis ----- CT or MR venography +/- MRI Head (edema, ischemia, hemorrhage) Hypertensive encephalopathy ----- MRI Head (CT is insensitive) Subarachnoid hemorrhage or Sentinel hemorrhage ----- CT Head, +/- Lumbar puncture Reversible cerebral vasoconstriction syndrome ----- MRI Head +/- MRA Head Other Migraine ----- normal clinical examination Primary thunderclap headache ------ normal clinical examination Spontaneous intracranial hypotension ----- lumbar puncture, +/- MRI Head (pachymeningeal enhancement) Diagnostic testing

7. Thunderclap headaches can be categorized by basic pathologic mechanisms: -itis (inflammation), -oma (mass), and -emia (vascular). Some thunderclap headaches result in permanent neurologic damage, whether by ischemia, hemorrhage, or mass effect. It is important to exclude these possibilities before settling on a benign diagnosis. Subarachnoid hemorrhage and third ventricle occlusion by a colloid cyst can rapidly progress to death. Advanced diagnostic imaging can be useful in confirming or excluding diagnoses for thunderclap headache. Summary