[Acute headache].

Sudden, explosive headache is rather rare. Though dramatic for the patient and the physician, it does not necessarily herald an intracranial catastrophe. Benign and dangerous thunderclap headaches cannot be distinguished from the features of headache itself, but rather on the basis of the situation, the additional symptoms and the findings. This means that every sudden headache should be considered potentially dangerous and be investigated immediately. The dangerous forms comprise intermittent hydrocephalus, acute bacterial meningitis and above all vascular complications. Subarachnoid hemorrhage frequently must be ruled out by computed tomography and lumbar puncture. Intracerebral, especially cerebellar hemorrhage, as well as hypertensive crisis require immediate treatment. Fatal cerebral embolism complicating spontaneous dissection of craniocervical arteries (carotid or vertebral arteries) can be prevented by early anticoagulant therapy. To confirm diagnosis, additional investigations such as CT, lumbar puncture or cerebrovascular ultrasound, and in rare cases MRI, should be performed early as the available time for effective therapy in many situations is short. Many of the benign forms of sudden headache can be diagnosed with a focused interview (cold or drug induced and food dependent headaches, sinusitis, glaucoma). Others, such as neuralgia, cough and coital headache, can be diagnosed as benign only when additional investigations have ruled out symptomatic forms.