A 66-year-old woman presents to the emergency room after experiencing a tonic-clonic seizure. She has been having worsening headaches and intermittent nausea over the past 5 months. The headaches are constant and dull, and they typically worsen when she sneezes or laughs. Recently, she has become increasingly nauseous and has vomited twice in the past 10 days. Her medical history is significant for type 2 diabetes mellitus and hypertension for which she takes metformin and losartan. Her temperature is 98.6°F (37.0°C), blood pressure is 115/70 mmHg, pulse is 70/min, and respirations are 12/min. She is noted to have papilledema on fundoscopy, but physical exam is otherwise normal. Her CT scan findings are presented in Figure A. Which of the following is the most likely diagnosis?
Glioblastoma multiforme
Cerebral toxoplasmosis
Neurosarcoidosis
Hemorrhagic stroke
Glioblastoma multiforme
This patient is presenting with symptoms of increased intracranial pressure (i.e., positional headaches, nausea, vomiting, and papilledema). Combined with her CT finding of a space-occupying butterfly-shaped lesion, the most likely diagnosis is glioblastoma multiforme.

Glioblastoma multiforme is the most common malignant primary nervous system cancer, most commonly occurring in adults above the age of 65. The tumor arises from the cerebral hemispheres and classically crosses the corpus callosum, producing a butterfly appearance on CT/MRI. Pseudopalasading necrosis is seen on biopsy, and tissue biopsy is usually glial fibrillary acidic protein (GFAP) positive. It has an unfavorable prognosis with a life expectancy of 6 months to 1 year. Management of glioblastoma includes surgical resection and palliative radiotherapy/chemotherapy.

Stupp et al. studied the role of electrical field therapy (TTFields) in conjunction with temozolomide in the treatment of glioblastoma multiforme. The authors found that combination therapy improved median progression-free survival (6.7 vs. 4.0 months, p < 0.001). The authors recommend that clinicians consider the use of TTFields to treat selected patients with glioblastoma multiforme.

Figure/Illustration A demonstrates a non-contrast axial head CT showing the classic butterfly lesion characteristic of glioblastoma multiforme (red arrow).

Incorrect Answers:
Answer A: Cerebral toxoplasmosis presents on imaging with multiple ring-enhancing lesions and is most common in patients with acquired immunodeficiency syndrome (AIDS), especially with CD4 T-cell counts of less than 100 cells/mm^3. This patient has no signs of infection or ring-enhancing lesions.

Answer C: Hemorrhagic stroke presents acutely with hemiparesis, altered mental status, slurred speech, or sensorimotor symptoms. CT imaging would reveal a hemorrhage.

Answer D: Metastatic brain tumor often presents with imaging findings of multiple well-circumscribed lesions with surrounding edema. These lesions are generally found at the highly vascularized gray-white junction. In a patient with no smoking history, a single brain lesion, and no other extra-cranial symptoms, this is a less likely diagnosis.

Answer E: Neurosarcoidosis can be caused by infiltrative sarcoidosis and often presents with bitemporal hemianopsia due to infiltration of the pituitary gland. Patients with sarcoidosis typically also present with pulmonary symptoms (e.g., wheezing and coughing) which are absent in this patient.

Bullet Summary:
Glioblastoma multiforme should be suspected in patients presenting with symptoms of increasing intracranial pressure and classic CT/MRI findings of a butterfly shaped lesion with central necrosis.