A 33-year-old man is admitted to the hospital due to new-onset seizures. He has no significant medical history. Vital signs are normal. Neurologic examination shows no abnormalities. CT scan of the head reveals a 3-cm cystic lesion in the temporal lobe. The mass is excised, and histopathology is shown in the image below: Which of the following is the most likely diagnosis?

Question

A 33-year-old man is admitted to the hospital due to new-onset seizures.  He has no significant medical history.  Vital signs are normal.  Neurologic examination shows no abnormalities.  CT scan of the head reveals a 3-cm cystic lesion in the temporal lobe.  The mass is excised, and histopathology is shown in the image below:  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec160b_384b_dd9b_9249_3b25c5a2191b_MD0001_00 Histopathology of this cystic brain lesion shows an invaginated scolex, the anterior portion of a tapeworm. The scolex has refractile hooklets and suckers, which allow attachment to host tissue. These findings are consistent with neurocysticercosis (NCC). NCC occurs after humans ingest Taenia solium (pork tapeworm) eggs in contaminated food or water. The eggs hatch into embryos, invade the intestinal mucosal border, and lodge in tissue (eg, brain, muscle, eye), where they form cysts with larvae. When the cystic lesions degenerate months or years later, it can cause inflammation and edema of the surrounding tissue, leading to symptomatic disease. The most common manifestation is adult-onset seizures due to intraparenchymal brain lesions. Although the diagnosis is usually made based on neuroimaging findings (eg, ≥1 cystic lesion) and serology, brain biopsy is sometimes performed due to concern for malignancy. (Choice B) Meningioma is the most common CNS neoplasm and often presents with seizure. However, imaging reveals an extraaxial, dural-based mass that compresses brain tissue. In addition, histopathology often shows whorls of uniform, oval tumor cells with eosinophilic cytoplasm, as well as psammoma bodies. (Choice C) Brain metastases (eg, melanoma) often cause seizures due to focal brain edema. However, imaging usually reveals multiple masses with surrounding edema at the gray-white matter junction, not a single cystic temporal lobe lesion. Histopathology is usually similar to the primary tumor. (Choice D) Protozoal infections such as toxoplasmosis and amoebic encephalitis can cause brain infection with seizure. However, toxoplasmosis appears as ring-enhancing lesions on imaging, and histology shows spherical cysts and tachyzoites, not a scolex. Amoebic encephalitis typically appears as nonspecific brain edema on imaging, and histology shows trophozoites and cysts. (Choice E) Tuberculosis can spread to the meninges or CNS. Tuberculomas in the brain can cause seizures, but imaging reveals ring-enhancing intraparenchymal lesions, not cysts. In addition, histopathology would show caseating granulomas with acid-fast bacilli. Educational objective: Neurocysticercosis is a helminth infection that occurs after the ingestion of Taenia solium eggs. It often presents with adult-onset seizure in patients from an endemic area. Imaging reveals ≥1 cystic brain lesions. The presence of a scolex, the anterior portion of the worm with hooks and suckers, is diagnostic.

A 33-Year-Old Man Is Admitted to the Hospital Due to New-Onset