Educational objective: Infection of the medial face, sinuses (ethmoidal or sphenoidal), or teeth may spread through the valveless facial venous system into the cavernous sinus, resulting in cavernous sinus thrombosis. Patients typically present with headache, fever, proptosis, and ipsilateral deficits in cranial nerves Ill, IV, VI, and V (ophthalmic and maxillary branches).

A 28-year-old man comes to the emergency department due to 2 weeks of headaches, fever, and episodes of inattentiveness. The patient has a history of Hodgkin lymphoma and is undergoing treatment with combination chemotherapy. Temperature is 38.2 C (100.8 F), blood pressure is 138/84 mm Hg, and pulse is 72/min. Lumbar puncture reveals an elevated opening pressure, and cerebrospinal fluid analysis shows moderately increased protein levels and low glucose levels. Light microscopy of the cerebrospinal fluid is shown in the image.

Educational objective: Patients with suspected cryptococcal meningitis can be diagnosed using India ink staining of the cerebrospinal fluid. Treatment with amphotericin B and flucytosine is required at first, followed by long-term fluconazole maintenance therapy.

A 55-year-old man with poorly controlled hypertension and type 2 diabetes mellitus comes to the emergency department due to difficulty seeing. He has had blurry vision for the last 2 weeks, and 1 day ago he suddenly noticed a shadow develop across the visual field of his left eye. The patient has no recent headache, double vision, vertigo, light sensitivity, or nausea. On examination, pupils are equal and reactive to light. There is an area of reduced vision in the left eye. Funduscopic examination reveals a flameshaped hemorrhage in the left temporal hemiretina.

Educational objective: Damage to the left temporal hemiretina will disrupt the transmission of visual information along the ipsilateral optic nerve, lateral optic chiasm, optic tract, lateral geniculate body, optic radiations, and primary visual cortex.

A 15-year-old girl is evaluated for recurrent episodes of focal onset seizures evolving to bilateral tonicclonic seizures over the past several months. She has also had headaches that are severe enough to keep her home from school. The patient has no prior medical conditions. MRI of the brain is shown in the exhibit.

Educational objective: Cerebral arteriovenous malformations (AVMs) are vascular malformations histologically characterized by a tangle of abnormal vessels, including large veins with thickened walls and irregular arteries. AVMs may present with intracranial hemorrhage, headache, and/or seizures. Radiologic findings include abnormal vasculature with a "bag of worms" appearance and multiple dark flow voids.

Educational objective: The C5-C6 spinal nerves mediate the biceps and brachioradialis reflexes.

68-year-old man with a history of Parkinson disease is hospitalized for pneumonia and sepsis. The patient is treated with intravenous (IV) fluids and antibiotics. He is also started on an infusion of IV dopamine for hemodynamic support. Although the manifestations of Parkinson disease are attributed to dopaminergic neuron degeneration in the substantia nigra, IV dopamine does not improve this patient's Parkinson symptoms.

Educational objective: The blood-brain barrier is formed by tight junctions between nonfenestrated capillary endothelial cells that prevent the paracellular passage of fluid and solutes. This barrier only permits the passage of substances from the blood to the brain via transcellular movement across the endothelial plasma membrane, which is limited by diffusion or carrier-mediated transport.

A 36-year-old woman comes to the office due to firm, nontender swelling of her right cheek for the past 4 months. The patient has had no fever, runny nose, sore throat, or cough. She drinks a glass of wine with dinner on most nights but does not use tobacco. Physical examination shows fullness of the preauricular space on the right side. An MRI of the region identifies a 2.2-cm mass in the right parotid gland, and a follow-up core needle biopsy shows the lesion to be neoplastic.