Secondary Headache Disorders

Introduction to Secondary Headaches

The International Classification of Headache Disorders, third edition, states that secondary headaches can be caused by various underlying medical conditions, and it is crucial to differentiate them from primary headaches because some secondary causes can be life-threatening 1.

Intracranial hemorrhage (intraserebral, subdural, subarachnoid, epidural) can cause "thunderclap headache" or the worst headache of a patient's life, according to the Journal of the American College of Radiology 2, 1.
Stroke or transient ischemic attack (TIA) is characterized by focal neurological deficits or atypical aura lasting >60 minutes, as noted by Nature Reviews Neurology 1, 3.

Brain tumors or space-occupying lesions can cause progressive headaches that wake patients from sleep, worsen with Valsalva or cough, as mentioned in Praxis Medical Insights: Practical Summaries of Clinical Guidelines 3.
Idiopathic intracranial hypertension is characterized by headache with papilledema, according to the Journal of Neurology, Neurosurgery and Psychiatry 6, 7.

Meningitis can cause headache with neck stiffness and unexplained fever, as stated by Nature Reviews Neurology 1, 3.

Hypoglycemia, hyperglycemia, and ketoacidosis can cause secondary headaches, according to Pediatrics 4.
Thyroid disease (hyperthyroidism, hypothyroidism) may require evaluation with morning TSH and free T4 if there are symptoms of cold intolerance or dizziness, as recommended by Praxis Medical Insights: Practical Summaries of Clinical Guidelines 3.

Low CSF pressure (<6 cm H2O) or CSF leak can cause postural headache, as mentioned in the Journal of the American College of Radiology 2.
Increased intracranial pressure can worsen with cough, sneeze, or exercise, according to Praxis Medical Insights: Practical Summaries of Clinical Guidelines 3.

Medication overuse headache is defined as headache ≥15 days/month with excessive use of non-opioid analgesics ≥15 days/month or other acute medications ≥10 days/month for >3 months, as stated by Nature Reviews Neurology 8, 9, 3.

Seizures can be a secondary cause of headache, often with atypical aura, as noted in the Journal of the American College of Radiology 5.

Giant cell arteritis can cause new-onset headache in patients >50 years with scalp tenderness, jaw claudication; ESR/CRP should be evaluated (although ESR can be normal in 10-36% of cases), as recommended by Praxis Medical Insights: Practical Summaries of Clinical Guidelines 3.

A comprehensive history should include age of onset, episode duration, frequency, location of pain, quality of pain, severity, exacerbating/relieving factors, associated symptoms, aura symptoms, and medication use, as stated by Nature Reviews Neurology 8, 9.
A complete neurological examination with attention to neurological, cardiac, and respiratory systems should be performed, according to Pediatrics 4.

MRI of the brain is preferred over CT for subacute presentation or suspicion of tumor/inflammatory process due to higher resolution and lack of ionizing radiation, as recommended by the Journal of the American College of Radiology 5, 3.
Non-contrast CT head is indicated if presentation is <6 hours from onset of acute severe headache (sensitivity 95% on day 0 for subarachnoid hemorrhage), according to Praxis Medical Insights: Practical Summaries of Clinical Guidelines 3.

Lumbar puncture may be necessary to confirm or rule out suspected secondary causes such as infection or abnormal CSF pressure, as stated by Nature Reviews Neurology 1.
ESR/CRP should be evaluated if giant cell arteritis is suspected in patients >50 years, as recommended by Praxis Medical Insights: Practical Summaries of Clinical Guidelines 3.
Morning TSH and free T4 should be evaluated if there are symptoms of cold intolerance or dizziness, according to Praxis Medical Insights: Practical Summaries of Clinical Guidelines 3.