A 35-year-old man presents to the emergency department with altered mental status. He was found by his roommate to be disoriented this morning. He had complained of a right-sided headache for the past 5 days. He has a history of human immunodeficiency virus (HIV) infection being treated with bictegravir, emtricitabine, and tenofovir. His last CD4 cell count was 500/mm^3. He does not smoke tobacco and drinks alcohol socially. His temperature is 104.2°F (40.1°C), blood pressure is 110/70 mmHg, pulse is 110/min, and respirations are 22/min. Examination reveals 3/5 strength to right shoulder abduction and elbow flexion/extension and 4/5 strength to right hip flexion/extension. The remainder of the strength exam on the right and left sides is normal. Neck flexion does not elicit pain, and there are no tongue lacerations. During the exam, the patient’s eyes are seen to roll backward with repeated flexion/extension of his extremities and loss of urine. This stops after 1 minute. Which of the following is the most likely diagnosis?
Bacterial meningitis
Fungal meningitis
Brain abscess
Epilepsy
Brain abscess
This HIV-positive patient presents with fever, unilateral headache, altered mental status, focal neurological deficits (3/5 strength to right shoulder abduction, elbow flexion/extension, hip flexion/extension), and a generalized tonic-clonic seizure, suggestive of a brain abscess.

A brain abscess typically presents in patients with underlying risk factors for infection, such as positive HIV status or bacterial endocarditis with hematogenous bacterial seeding. Patients present with fever, unilateral headache, altered mental status, focal neurological deficits, and fevers. Work-up consists of blood cultures, CT scan, and confirmatory magnetic resonance imaging with gadolinium contrast, showing a focal, hyperintense lesion with restricted diffusion. Treatment is with empiric broad-spectrum antibiotic therapy (e.g., vancomycin, metronidazole, and cefepime for gram-positive, gram-negative, and Pseudomonas coverage in immunocompromised patients) and surgical drainage.

Brouwer et al. review the causes, diagnosis, and treatment of brain abscesses. They discuss the importance of rapid initiation of antimicrobial therapy in these patients.

Incorrect Answers:
Answers 1 & 5: Bacterial or fungal meningitis can present with fever, headache, focal neurological deficits, and seizures but patients typically have meningeal signs such as pain with neck flexion. Cryptococcal meningitis is commonly seen in HIV-positive patients with CD4 counts < 100/mm^3.

Answer C: Cytomegalovirus encephalitis can present with fever, altered mental status, headache, and focal neurological deficits in patients with HIV infection. It typically presents in patients with severe immunodeficiency, often with CD4 cell count < 50/mm^3. This patient’s CD4 cell count is 500/mm^3, making this less likely than an abscess.

Answer D: Epilepsy is a primary neurological disorder that can cause generalized tonic-clonic seizures but would not explain this patient’s fever or unilateral headache. While Todd paralysis (focal weakness after a seizure) can occur after seizures, this patient’s focal weakness predates his seizure. A primary seizure disorder is not diagnosed when seizures occur secondary to another process.

Bullet Summary:
Brain abscess presents with fever, altered mental status, unilateral headache, seizures, and focal neurological deficits in patients with risk factors for infection (for example HIV, bacterial endocarditis).