CYSTIC 'MIRROR' BRAIN METASTASIS
Departments of Neurosurgery, All India Institute of
Medical Sciences, New Delhi-110029
ABSTRACT
We describe a
case of a 50-year-old male, nonsmoker, who presented with one-month history of
memory distubances and behavioural
changes. CECT head showed bilateral frontal 'mirror' cystic lesions with mild
peripheral enhancement. The patient was subjected to left frontal craniotomy,
cyst aspiration and biopsy of the cyst wall. As histopathalogical
examinanition revealed it to be a poorly
differentiated carcinoma of unknown origin, he was subsequently referred for
radiotherapy and chemotherapy. In difference to the recent enthusiasm for
radical excision of such lesions, we are of the opinion that a conservative
approach involving decompression of the cyst with biopsy of the cyst wall is
more suitable in such patients, as chances of neurological deterioration
following radical surgery are high, especially if the lesion is in proximity to
the eloquent areas.
KEY WORDS: cystic brain metastasis, mirror
lesions
Fig 1: Contrast enhanced CT head, axial image showing bifrontal cystic lesions with irregular ring enhancement.
INTRODUCTION
Cystic brain metastasis may prove to be a daignostic
and therapeutic challenge to the treating neurosurgeon. We report a case of
cystic brain metastasis with unknown primary managed by decompression of the
cyst along with biopsy of the cyst wall.
CASE REPORT
A 45-year-old male presented with one
month history of progressive dysphasia and alteration in behavior. He had right
hemiperesis of recent onset and was in altered
sensorium one day prior to presentation. There were no comorbid
medical problems and no history of any addictions could be elicited. On
examination patient was drowsy and dysphasic, with right hemipersis
of grade 4/5. A contrast enhanced CT head revealed bilateral frontal 'mirror' cystic lesions with mild peripheral
enhancement (fig 1). In view of the deteriorating clinical condition, he was
taken up for emergency surgery and a left frontal craniotomy with initial cyst
aspiration followed by biopsy of the cyst wall was performed. The opposite side
cystic lesion was not touched. Postoperatively, the patient’s sensorium
improved and the hemiperesis also resolved. As
histopathological examination of the cyst wall revealed a poorly differentiated
carcinoma of unknown origin, he was subsequently referred for radiotherapy and
chemotherapy.
Cystic
metastases in the brain are relatively rare and only few case reports are
available in literature.1-6The cystic changes may occur due to
necrosis in a solid lesion as a result of the tumor outgrowing its blood supply
or less commonly due to cyst formation by the tumor itself. Certain tumors such
as ductal carcinoma of the breast and adenocarcinoma of the lung are more frequently associated
with metastatic cyst formation, by virtue of their being the most common
primary tumors. 7 These cases can be difficult to diagnose, as radiologically, in absence of a known primary, the lesion
could be confused with brain abscess or a cystic astrocytoma. MR Spectroscopy
may provide some clue as to the pathology of the lesion, but by no means can be
taken as an infallible diagnostic aid. Though diffusion-wieighted
MRI has reported to be useful in differentiating between abscesses and cystic
or necrotic tumors, 8 recent reports have shown that findings on
diffusion-wieighted MRI during the early capsule
formation stage in abscesses and early tumor necrosis are probably similar and
must be interpreted with caution.9 Stereotactic biopsy may also not
be conclusive as a necrotic tissue and abscess may both contain polymorphs. The
differentiation is important as in cases of multiple cystic metastases,
directly subjecting the patient to radiotherapy and/or chemotherapy may avoid
the morbidity associated with a major surgical procedure. This becomes even
more relevant in view of the recent findings that cystic metastasis have a
worse prognosis as compared to their solid counterparts. 10 In our
patient the progressive hemiparesis and altered
sensorium made the decision to operate easier.
Treatment
protocols have ranged from conservative management with radiotherapy and
chemotherapy, to cyst aspiration and radical excision of its wall. 9
We believe that a middle path involving decompression of the cyst with biopsy
of the cyst wall is more suitable in such patients as chances of neurological
deterioration following radical surgery are high, especially if the lesion is
in proximity to the eloquent areas.
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