AJR:176, May 2001
1319
rimary central nervous system (CNS)
lymphoma refers to isolated involve-
ment of the craniospinal axis in the
absence of primary tumor elsewhere in the body.
Once considered a rare occurrence, primary lym-
phomatous disease of the CNS is now encoun-
tered frequently, in both immunocompetent and
immunocompromised patients. HIV infection
and AIDS are the leading risk factors [1]. By defi-
nition, diagnosis of primary CNS lymphoma in a
patient with HIV is an independent criterion for
AIDS. Congenital causes of immunodeficiency
(e.g., Wiskott-Aldrich syndrome, IgA deficiency,
and X-linked lymphoproliferative syndrome) and
acquired causes, including an immunosuppres-
sive regimen after organ transplantation, are also
associated with greater risk for primary lym-
phoma of the CNS. Recent epidemiologic data
show an increased incidence of primary CNS
lymphoma in low-risk immunocompetent pa-
tients as well [1, 2]. This pictorial essay illustrates
various imaging appearances of primary CNS
lymphoma and should aid in its early recognition.
Clinical Aspects
Primary CNS lymphoma may arise from
different parts of the brain, with deep hemi-
spheric periventricular white matter being the
most common; corpus callosum, cerebellum,
orbits, and cranial nerves may also harbor the
tumor. After the diagnosis is made, an exami-
nation is done that includes MR imaging of the
craniospinal tract; cerebrospinal fluid and bone
marrow examinations; and screening for pri-
mary tumor in the eye, chest, and abdomen
[1]. The presenting symptoms in primary CNS
lymphoma vary depending on the location of
the masses and the immune status of the pa-
tient. Primary CNS lymphoma in immuno-
competent patients tends to present with a
large solitary hemispheric mass. HIV-positive
patients often present with an acute change in
mental status and an encephalopathy-like pic-
ture, likely related to combined effects from
other concomitant infections and the side ef-
fects of antiretroviral drugs. The traditional
method of admini