Primary angiitis of the central nervous system presenting as unilateral optic neuritis.

A middle-aged woman who experienced recurrent episodes of unilateral vision loss and eye pain. On presentation, magnetic resonance imaging (MRI) demonstrated left optic nerve enhancement with patchy hyperintensities in the white matter of both frontal lobes and ill-defined enhancement in a lenticulostriate distribution. Ophthalmologic examination revealed left optic disc edema with a macular scar consistent with neuroretinitis. Her subsequent clinical course was notable for 2 episodes of painful vision loss, without associated neurologic symptoms, which resolved with intravenous and oral steroids. More than 1 year after her initial presentation, the patient developed right facial weakness and slurred speech, and shortly thereafter suffered a fatal intracerebral hemorrhage. Histopathology on autopsy confirmed a diagnosis of primary angiitis of the central nervous system (PACNS). This is an unusual case of PACNS presenting with recurrent unilateral optic neuritis. The vascular enhancement pattern on MRI suggesting inflamed cerebral blood vessels is a rarely described pattern, which likely reflects intracerebral extension of the ocular pathology. The combination of neuroretinitis and perivascular MRI enhancement pattern may represent a subtype of PACNS.

Quality initiatives: blind spots at brain imaging.

Radiologists face the daily challenge of analyzing and interpreting a high volume of images in a timely manner. Minimizing errors, whether perceptual or cognitive in nature, is paramount for high-quality diagnostics and patient care. There are certain areas within the head encountered at routine brain imaging in which the interpreting radiologist is most prone to make perceptual errors. These areas, or "blind spots," include the cerebral sulci, dural sinuses, orbits, cavernous sinuses, clivus, Meckel cave, brainstem, skull base, and parapharyngeal soft tissues. In addition, the use of an inappropriate window width and level for the evaluation of computed tomographic (CT) scans can be a virtual, rather than an anatomic, blind spot. The inclusion of a comprehensive checklist for evaluation of these blind spots as part of every brain imaging study is crucial for avoiding false-negative results. Knowledge of the anatomic features of these blind spots is also crucial, as well as familiarity with the normal CT and magnetic resonance imaging findings in these areas. In addition, the radiologist should be aware of possible interpretation pitfalls that may lead to false-positive results (eg, normal anatomic variants that may be mistaken for pathologic conditions). Finally, a well-developed differential diagnosis will help ensure correct interpretation and appropriate patient treatment.

Atypical imaging appearance of toxoplasmosis in an HIV patient as a butterfly lesion.

In acquired immunodeficiency syndrome (AIDS) patients, differentiating toxoplasmosis and primary central nervous system (CNS) lymphoma remains a clinical and radiographic dilemma. The presence of butterfly lesions crossing the corpus callosum is customarily used to exclude the possibility of toxoplasmosis. We present an AIDS patient who had Epstein-Barr virus (EBV) polymerase chain reaction (PCR) -positive cerebrospinal fluid studies with a butterfly toxoplasmosis lesion confirmed by multiple methods signifying the importance of including toxoplasmosis in the differential diagnosis of butterfly lesions.