Primary thunderclap headache

This code represents a severe, sudden-onset headache that reaches maximum intensity within one minute, often described as the "worst headache of my life." It is considered primary when no underlying intracranial pathology is identified after thorough investigation.

Use this code for patients presenting with an abrupt, excruciating headache where diagnostic workup (e.g., CT scan, lumbar puncture) has ruled out secondary causes such as subarachnoid hemorrhage or cerebral venous thrombosis. Documentation should clearly state "primary thunderclap headache" and confirm the absence of other etiologies.

• Ensure documentation explicitly states "primary" to differentiate from secondary thunderclap headaches, which require coding the underlying cause.
• Do not use this code if an underlying cause for the thunderclap headache is identified; instead, code the specific etiology.
• Carefully review imaging and CSF results to confirm the primary nature of the headache before assigning this code.