Ring Enhancing Lesions
in a patient with AIDS
Submitted by Marion
Brody, MD
·
Diagnoses to consider in
anyone with multiple
ring-enhancing lesions:
o
Metastatic
disease
o
Demyelinating disease
o
Infection
·
Leading
diagnoses in patients
with advanced AIDS who
have CNS abnormality:
o
Toxoplasma
encephalitis (T. Gondii)
o
Primary
CNS Lymphoma (EBV)
o
PML (JC)
o
HIV
Encephalopathy (HIV)
o
CMV
Encephalitis (CMV)
·
Other
diagnoses to consider in
patients with advanced
AIDS who have CNS
abnormality:
o
TB (in
developing countries)
o
Staphylococcus,
Streptococcus,
Salmonella, Nocardia,,
Rhodococcus, Listeria;
o
Cryptococcus;
Histoplasmosis;
Candidiasis;
Coccidioidomycosis;
Aspergillosis;
Trypanosomiasis;
Herpetic
meningoencephalitis;
Neurocysticercosis;
Meningovascular
syphilis; Amebic
abscesses
·
How
does the physician avoid
a brain biopsy?
·
Leading
diagnoses in patients
with advanced AIDS who
have “Mass Lesions”:
o
Toxoplasma
encephalitis (T. Gondii)
§
50% of all
brain lesions in AIDS
patients.
o
Primary
CNS Lymphoma (EBV)
§
30% of all
brain lesions in AIDS
patients
o
(PML,
HIV-associated
encephalopathy, and CMV
encephalitis usually do
not cause mass lesions)
·
History
o
Toxo
§
Headache,
confusion, +/- fever;
focal weakness,
seizures; if advanced,
dull affect
o
Lymphoma
§
All of
above and constitutional
symptoms (night sweats,
weight loss)
o
PML
§
Rapid
neurologic decline (hemiplegia,
visual field defects,
ataxia, aphasia)
o
HIV
Encephalopathy
§
Progressive memory loss,
depression, movement
disorders
o
CMV
encephalitis
§
Confusion,
focal deficits
·
Laboratory tests
o
Blood:
§
Anti-toxoplasma
IgG antibodies are
almost always positive
if patient has toxo
encephalitis
§
Toxo IgM
Abs generally
are
not detectable in acute
infxn; Toxo IgG
quantitative levels
do not reflect
disease activity.
§
Patients
with toxo usually
have CD4 < 100
§
Patients
with CMV encephalitis
usually have CD4< 50
o
A
lumbar puncture is
contraindicated if
patient has lesions
producing mass-effect
and has focal signs
o
CSF:
§
Toxo,
PCNSL, and PML shows
<500 lymphs/uL,
increased protein,
normal glucose.
§
Lymphoma
may or may not show
abnormal lymphocytes
o
Toxo
PCR
is 50% sensitive,
up to 100% specific.
o
EBV PCR
sensitivity/specificity
varies with testing
center
o
JC virus
PCR is up to 93%
sensitive and specific
o
CMV PCR
is 80% sensitive, 90%
specific
·
Imaging
on CT and MRI
o
Toxoplasma
Encephalitis
§
Thin-walled
ring-enhancing lesions,
surrounding edema;
rarely diffuse
encephalitis
§
Multiple
lesions 80%
§
Usually
hyperintense with
hypointense rim on T2
(can have decreased
signal in central areas
from calcium and
hemorrhage)
§
Basal
Ganglia, G/W junction;
parietal, frontal,
thalamus
§
More
likely to appear in
posterior fossa than
PCNSL
§
< 4 cm
T1 weighted,
gadolinium-enhanced
sagittal MRI images of
the brain demonstrate
two
ring-enhancing lesions,
one (red arrows) in the
thalamus and the other
(yellow arrow)
in the cerebellum.
For a version of this
photo without the arrows, click here
o
Primary
CNS Lymphoma
§
Ring-enhancing lesions,
surrounding edema
§
Multiple
lesions 50%
§
Variable
signal on T2; isointense
or hypointense on T1
§
Basal
Ganglia, deep white
matter
§
More
likely to cross corpus
callosum or occur in
periependymal areas than
TE
§
Can be >
4cm
o
PML:
·
Multiple
areas of demyelination,
without
contrast-enhancement or
edema
·
Bilateral,
asymmetric; hypointense
on T1, hyperintense on
T2
·
Can see
atypical enhancing
lesions with immune
reconstitution syndrome
·
Periventricular and
subcortical white matter
(rarely grey matter)
o
HIV
Encephalitis:
§
Indistinct
lesions in subcortical
white matter
§
Symmetric;
hyperintense on T2
o
CMV
Encephalitis:
§
Scattered
micronodules in the
cortex, BG, brain stem,
and cerebellum; or
§
Large
ventricles with
periventricular
enhancement/hyperintensity
on T2; or
§
Ring-enhancing lesions
with edema
·
Other
imaging modalities:
o
SPECT –
lymphoma greater
thallium uptake than
Toxo
o
PET –
lymphoma greater glucose
+ methionine uptake than
Toxo
o
Perfusion
MRI – Increased flow in
lymphoma, decreased in
Toxo
o
MR
Spectroscopy – TBA
·
Take
home points
o
90%
likelihood it’s Toxo if
all of the following
criteria are met:
§
Toxo IgG
(+) in serum.
§
Patient
with a CD4 < 100 is not
receiving prophylaxis
for Toxo
§
Multiple
ring enhancing lesions
on CT or MRI
o
In these
cases, often patient is
treated presumptively
for Toxo
o
If it’s
Toxo, should see
clinical improvement in
1 week (caveat: steroids
can improve immediate
symptoms by reducing
brain edema without any
true reduction in
severity of infection)
o
If it’s
Toxo, should see
radiographic improvement
within 2 weeks
