A surprising cause of hallucinations. A pathognomonic sign is a finding that is so characteristic it essentially confirms a diagnosis. Lee and Pedregosa present a striking Images in Clinical Medicine case in the New England Journal of Medicine demonstrating a classic "dot-in-hole" sign of neurocysticercosis, where the bright dot represents the scolex, or head, of a tapeworm living within a brain cyst. Key points: - A previously healthy 52-year-old woman developed progressive headaches, visual hallucinations, language dysfunction, and likely seizures over several months. - Brain MRI revealed multiple cystic lesions throughout the cerebral hemispheres and cerebellum containing an eccentric bright nodule, the classic "dot-in-hole" sign that is considered pathognomonic for parenchymal neurocysticercosis. - Treatment with praziquantel, albendazole, glucocorticoids, and levetiracetam led to clinical improvement and shrinkage of the cysts within one month. My take: One of the greatest lessons in neurology is to keep an open mind. Not every person with cognitive changes, seizures, hallucinations, or abnormal imaging has a neurodegenerative disease. Geography, travel history, exposure risks, and careful interpretation of neuroimaging remain critical. This image is a wonderful reminder that pattern recognition still matters, even in the era of biomarkers and artificial intelligence. Here are 5 points that resonated w/ me: 1- Neurocysticercosis remains one of the most common causes of acquired epilepsy worldwide and should remain on the differential diagnosis when evaluating new-onset seizures and multiple brain lesions. 2- The "dot-in-hole" sign is one of the most recognizable imaging findings in neurology because it directly visualizes the scolex within a cyst, making the diagnosis highly specific. 3- Careful review of MRI often provides the answer before invasive testing is needed. 4- Appropriate antiparasitic therapy, combined w/ anti-inflammatory treatment and seizure management, can lead to substantial clinical improvement. 5- Every neurologist should remember that uncommon diseases are not rare when practicing in a global community. Careful history-taking, thoughtful imaging review, and broad clinical reasoning remain among our most powerful diagnostic tools. nejm.org/doi/full/10.1056/NE…