Transcript Usefulness of the multimodality imaging for the diagnosis

Usefulness of the
multimodality imaging for the
diagnosis of an atypical
lymphoma of the brainstem
ATTIA M, KOUKI S, LANDOULSI M,BOUGUERRA
S,AROUS Y, BOUJEMAA H, BEN ABDALLAH N
NEURORADIOLOGY : NR 17
INTRODUCTION

Primary central nervous system lymphoma(PCNSL) is
a rare tumor, making up only 1%-1.5% of all cranial
tumors.
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They occur sporadically or in association with
congenital or acquired immunodeficiency disorders.
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the diagnosis of primary central nervous system
lymphoma should always be considered as an
emergency because of the therapeutic consequences
it implies.
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There were reports that 55% of PCNSL occurred
at supratentorial corpus callosum and cerebral
white matter around the ventricles and 17%
occurred at basal ganglia, thalamus, and
subthalamus region, while only 11% were
located at posterior cranial fossa.

The case we report here illustrates the
contribution of MRS in the diagnostic approach of
a very atypical PCNSL of the brainstem.
Material and Method
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We report the case of a 24-year-old male with no
significant medical history presented with
swallowing disorder, fever, irregular
breathing and cerebellar syndrome.
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The patient had a brain MRI with the
conventional sequences and a multimodal
imaging including diffusion and spectroscopy
sequences.
Sagittal T2-weighted MRI
Diffuse hyperintensity on T2-weighted
images and flair involving the pons and
extending to the bulb
Axial FLAIR –weighted MRI
axial T2-weighted MRI
T1-weighted axial images before
and after intravenous contrast
administration : ring enhancement of the lesions
The mass lesion shows hyperintensity on
DWI
On ADC map, the solid lesions are
hypointenses.
Single-voxel 1H
MRS TE(30 ms)
Single-voxel 1H
MRS TE(135ms)
Single-voxel 1H MRS examination shows a decrease of the NAA peak
(2.0 ppm), an increase of the choline peak (3.2 ppm),and a lipid peak
(1.3 ppm).

Lumbar puncture for cerebrospinal fluid
(CSF) cytological examination detected B
lymphoid cells, the diagnosis of PCNSL
was later confirmed by a brain biopsy.
DISCUSSION

The incidence of primary central nervous system
lymphomas(PCNSL) , aggressive neoplasms with an
indeterminate pathogenesis, is increasing in
immunocompetent and immunocompromised patients.

They currently represent 6.6–15.4% of all primary brain
tumors.

They are comprised of non- Hodgkin’s lymphoma, mostly
of B-cell origin, and may appear as solitary or multiple
nodular tumors, or as diffusely infiltrative perivascular
neoplasms .
DISCUSSION
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80% of primary CNS lymphomas locate in the
supratentorial region, while 11% of the cases involve the
posterior cranial fossa, and are mainly in the cerebellum.
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Optimal management of primary CNS lymphoma requires a
correct diagnosis, since steroids may alter or even
eliminate the ability to obtain histological diagnosis.
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large B cell lymphoma is highly responsive to radiotherapy
and steroid, causing complete regression and clinical
remission.
In addition, chemotherapeutic agents can cross the
impaired blood-brain barrier, leading to complete response
to chemotherapy in some patients.
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Nevertheless, the tumor may recur in 80–95% of cases
Imaging in immunocompetent
patients
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PCNSL is typically a solitary and supratentorial lesion. In a
study of 100 immunocompetent patients with PCNSL, the
most common locationwas the cerebral hemispheres seen
in 38% of cases.
Less commonly the cerebellum and brainstem may be
infiltrated.
Contrast-enhanced magnetic resonance imaging (MRI) is
the optimal imaging technique.22 PCNSL is typically
isohypointense on T1-weighted imaging. It is isohypointense to grey matter on T2-weighted imaging PCNSL
can also demonstrate T2-weighted hyperintensity.
Contrast enhancement tends to be homogeneous. In
immunocompetent patients, necrotic, thus ring-enhancing,
lesions are rare.
Imaging in immunocompromised
patients
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Some features are more typical in the
immunocompromised population.
Here, multiple lesions are more common and seen in up to
60% of patients,25 a higher percentage than the 38%
found in immunocompetent patients.
These lesions also tend to be smaller.
PCNSL in the immunocompromised demonstrates rapid
growth.
The tumour outstrips its blood supply and becomes
necrotic centrally.
This leads to ring enhancement after the administration of
contrast medium.
The ring-like enhancement may be irregular and nodular
Advanced imaging techniques
DIFFUSION
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The effect of diffusion-weighted imaging (DWI) is based on
the diffusion of water molecules.
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Diffusion-weighted imaging is a kind of modern molecular
imaging and gives a picture of molecular motion.
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It is based on Brownian motion of water molecules and
thus provides information on the mobility of water
molecules.
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Cellular relatively dense packed and organized tissue as
cerebral cortex restricts movement and diffusion of water
molecules.
DIFFUSION
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DWI provides useful additional information about tissue
characterization, and may be helpful to differentiate CNS
lymphomas from other cerebral neoplasms.
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Water diffusion is often restricted in lymphoma as it is
hypercellular and made up of large lymphoid cells.
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PCNSL is therefore hyperintense on diffusion-weighted
imaging (DWI) and hypointense on apparent diffusion
coefficient (ADC) maps (low ADC values).
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Ninety percent of pre-treatment patients in one study
demonstrated restricted diffusion, but PCNSL may also
demonstrate unrestricted diffusion. After treatment,
restricted diffusion is more variable.
Spectroscopy
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1H-magnetic resonance spectroscopy (MRS) provides
information on metabolic change in vivo.
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PCNSL cases demonstrates raised choline (Cho)
resonances relative to creatine (Cr) and N-acetyl aspartate
(NAA), which are non-specific and are also demonstrated in
other brain tumors.
Spectroscopy
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The most specific finding for PCNSL on MRS is an increase
in lipid resonance.
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This is typically a signature of cell death; however, a lipid
dominated spectrum is found in PCNSL that is not
macroscopically necrotic.
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This appears to be due to numerous macrophages and the
increased turnover of membrane components in
transformed lymphoid cells.
PERFUSION
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the maximum rCBV ratios is often less than 2.3.
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Contrary to the strong enhancement, the maximum rCBV
ratios of CNS lymphomas were significantly lower than
those of high grade gliomas, metastases, or meningiomas.
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Strong enhancement without CBV increment in lymphoma
is attributed to the blood brain barrier destruction without
neovascularization in contrast to the marked contrast
enhancement with increased vascularity in high grade
gliomas.
CONCLUSION
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PCNSL may present with a wide range of established
imaging findings.
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This makes diagnosis with imaging alone challenging.
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Additionally, the radiologist needs to be aware of the rare
PCNSL variants that present with their own unique imaging
features.
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Much interest has been placed on advanced imaging
techniques, including MR perfusion, MRS, and nuclear
medicine, to aid diagnosis.
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Their findings have been shown to complement
conventional MRI findings, supporting a diagnosis of PCNSL
References

Imaging of primary central nervous system lymphoma. Y.Z.
Tang et al. Clinical Radiology 66 (2011) 768-777.

Analysis of perfusion weighted image of CNS lymphoma. In Ho
Lee and al. European Journal of Radiology 76 (2010) 48–51.
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Diffusion-weighted imaging of primary brain lymphomas:
Effect of ADC value and signal intensity of T2-weighted
imaging. Masuma Akter and al. Computerized Medical Imaging
and Graphics 32 (2008) 539–543.

Conventional MRI and 1H MR spectroscopy in primary central
nervous system lymphoma. Stefan Martin Golaszewski.
European Journal of Radiology Extra 74 (2010) e5–e8.