Differential Diagnosis for Headache, Fever, and Altered Mental Status
The combination of headache, fever, and altered mental status can be caused by a variety of conditions, ranging from benign to life-threatening. Here's a categorized differential diagnosis:
Single Most Likely Diagnosis
- Meningitis: This is a common and serious condition that presents with headache, fever, and altered mental status. The inflammation of the meninges, which can be caused by viral, bacterial, or fungal infections, leads to these symptoms. Meningitis is a medical emergency and requires prompt treatment.
Other Likely Diagnoses
- Encephalitis: An inflammation of the brain tissue, usually caused by viral infections, which can present with headache, fever, altered mental status, and sometimes seizures or focal neurological deficits.
- Sepsis: A systemic infection that can lead to fever, altered mental status, and headache due to the body's inflammatory response. Sepsis can progress to septic shock, which is life-threatening.
- Brain Abscess: A localized infection within the brain that can cause headache, fever, and altered mental status, along with focal neurological signs depending on the location of the abscess.
Do Not Miss Diagnoses
- Subarachnoid Hemorrhage: Although typically presenting with a sudden, severe headache, altered mental status can occur, especially if the hemorrhage is large or if the patient has a pre-existing condition that affects mental status. Fever might not be a primary symptom but can occur due to associated complications.
- Cerebral Venous Thrombosis: This condition involves a blood clot in the brain's venous sinuses and can present with headache, fever (if there's an associated infection), and altered mental status. It's crucial to consider this diagnosis, especially in patients with risk factors for thrombosis.
- Status Epilepticus: Prolonged or recurrent seizures without full recovery between them can lead to altered mental status. Fever might be present due to the seizure activity itself or an underlying cause. Headache can occur post-ictally.
Rare Diagnoses
- Neuroleptospirosis: A rare infection caused by Leptospira bacteria that can affect the central nervous system, leading to symptoms including headache, fever, and altered mental status.
- Cerebral Malaria: Caused by Plasmodium falciparum, this condition can lead to cerebral symptoms including headache, fever, and altered mental status, especially in travelers to or residents of endemic areas.
- Hashimoto's Encephalopathy: A rare condition associated with Hashimoto's thyroiditis, characterized by altered mental status, headache, and sometimes fever, which improves with corticosteroid treatment.
Each of these diagnoses has distinct features and requires a thorough clinical evaluation, including history, physical examination, laboratory tests, and imaging studies, to determine the underlying cause of the symptoms.