AJR 2004; 182:1543-1546
© American Roentgen Ray Society
Cerebellar Endometriosis
Dipanka Sarma1,
Pratibha Iyengar2,
Thomas R. Marotta1,3,
Karel G. terBrugge1,
Fred Gentili4 and
William Halliday5
1 Division of Neuroradiology, Fell 3-210, Toronto Western Hospital, University
Health Network, University of Toronto, 399 Bathurst St., Toronto M5T 2S8, ON,
Canada.
2 Department of Laboratory Medicine and Pathobiology, Banting Institute, 100
College St., Rm. 110, Toronto M5G 1L5, ON, Canada.
3 Division of Neuroradiology, St. Michael's Hospital, 30 Bond St., Toronto M5B
1W8, ON Canada.
4 Division of Neurosurgery, Toronto Western Hospital, University Health Network,
University of Toronto, Toronto M5T 2S8, ON, Canada.
5 Division of Neuropathology, Toronto Western Hospital, University Health
Network, University of Toronto, Toronto M5T 2S8, ON, Canada.
Received June 24, 2003;
accepted after revision October 8, 2003.
Address correspondence to K. G. terBrugge.
Introduction
Endometriosis is defined as the presence of functional endometrial tissue
located in extrauterine sites. The disease is a common one, frequently
involving the ovary and other pelvic organs. Extrapelvic disease may involve
the gastrointestinal and genitourinary tracts and less commonly the thorax,
cutaneous tissues, surgical scars, bone, and breast. Central nervous system
involvement is rare [1,
2]. We describe a cystic mass
involving the cerebellar vermis, with MRI features of intracystic hemorrhage
similar to that described in pelvic endometriomas
[3]. Histologic examination was
consistent with a diagnosis of endometriosis. To our knowledge, only two
previous case reports of cerebral endometriosis are found in the
English-language literature [4,
5], and cerebellar involvement
has not before been described.
Case Report
A 40-year-old woman presented with a recent history of gait disturbance and
headaches. She had a history of congenital hydrocephalus secondary to
aqueductal stenosis. Over the years, she had undergone multiple shunt
revisions since her first ventriculoperitoneal shunt at 2 months old. Her most
recent shunt revision was performed 2 years previously.
Suspecting shunt blockage, we initially obtained an unenhanced CT scan,
which showed no significant interval increase in the size of the ventricles.
The CT scan revealed a midline posterior fossa mass lesion (Figs.
1A and
1B). MRI showed a
multiloculated cystic mass arising from the superior vermis with a lobulated
component projecting into the superior cerebellar cistern (Figs.
1C,
1D,
1E). Mild enhancement of the
rim was present, with an enhancing nodule superiorly
(Fig. 1E). Fluid–fluid
levels were noted in the cystic loculi, the dependent layer being hyperintense
on T1-weighted and hypointense on T2-weighted images, suggesting previous
hemorrhage (Figs. 1C and
1D). A hemangioblastoma with
intracystic hemorrhage was considered as a possibility, although we recognized
that the appearance and degree of enhancement was not typical for this
diagnosis. Cavernous angioma with hemorrhage and cystic change has been
described in the posterior fossa but was thought unlikely with the lobulated
projections extending into the superior cerebellar cistern.
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Fig. 1A. —40-year-old woman with history of congenital hydrocephalus
and recent onset of headaches and gait disturbance. Unenhanced axial CT scan,
initially obtained to assess ventricular size, shows midline posterior fossa
mass (arrowheads).
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Fig. 1B. —40-year-old woman with history of congenital hydrocephalus
and recent onset of headaches and gait disturbance. Unenhanced axial CT scan
obtained at higher level than A shows superior pole of mass
(arrowhead) and part of ventriculoperitoneal shunt
(arrow).
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Fig. 1C. —40-year-old woman with history of congenital hydrocephalus
and recent onset of headaches and gait disturbance. Unenhanced sagittal
T1-weighted spin-echo MR image shows lobulated superior vermian mass with
fluid–fluid levels (arrows) indicating its cystic nature.
Dependent fluid is hyperintense.
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Fig. 1D. —40-year-old woman with history of congenital hydrocephalus
and recent onset of headaches and gait disturbance. Axial T2-weighted fast
spin-echo MR image again shows fluid–fluid levels in cystic mass,
dependent fluid being hypointense on this sequence (arrows). These
features are suggestive of previous intracystic hemorrhage, and this MRI
appearance is similar to that described in pelvic endometriomas
("shading" sign).
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Fig. 1E. —40-year-old woman with history of congenital hydrocephalus
and recent onset of headaches and gait disturbance. Enhanced coronal
T1-weighted MR image shows solid enhancing nodule superiorly and mild rim
enhancement around cystic mass.
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At surgery, the multiloculated cystic nature of the mass was confirmed, as
was the solid nodule. The mass was in contact with the vein of Galen and the
basal vein of Rosenthal from which it was separated; the tumor was completely
excised. The cyst contents were a chocolate-colored fluid with flecks of
yellow.
Her symptoms markedly improved after surgery. On reviewing her history, she
denied any cyclical headaches or seizures. She did not have a history of
pelvic pain or infertility and had given birth to a healthy baby by cesarean
delivery 3 years previously. Follow-up imaging or laparoscopy for pelvic
endometriosis has not yet been performed because she has been asymptomatic in
this regard.
The surgical specimen, consisting of multiple reddish thin-walled cystic
fragments, was submitted to pathology for routine processing. Microscopic
examination revealed cystic spaces lined by simple cuboidal epithelium that
strongly resembled atrophic endometrium. In focal areas, squamous metaplasia
of the epithelium was present, composed of cytologically bland cells with
eosinophilic cytoplasm and some squamous morules. In certain areas, the
epithelium also took on an extensive papillary appearance with true
fibrovascular cores. Although no endometrial stroma was present, the walls of
the cystic spaces were lined by fibrous tissue that contained multiple foci of
previous hemorrhage, characterized by the presence of hemosiderin-laden
macrophages that stained positively with an iron stain. The surrounding
cerebellum showed chronic gliosis, including Rosenthal fibers.
Immunohistochemical studies confirmed that the endometrial-type epithelium
stained positively for cytokeratin 7 and vimentin, estrogen, and progesterone
receptors (nuclear). CD10 staining did not highlight any endometrial stroma
but there was strong luminal staining of the endometrial-type epithelium. The
presence of both the endometrial-type epithelium and hemosiderin-laden
macrophages meets the criteria for diagnosing endometriosis. The extensive
metaplastic changes seen have been previously reported in the endometrium
[6] and in benign lesions
strongly associated with endometriosis
[7], such as ovarian
müllerian mucinous papillary borderline
tumors.
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Fig. 1F. —40-year-old woman with history of congenital hydrocephalus
and recent onset of headaches and gait disturbance. Photomicrograph of
histopathologic specimen shows hemosiderin-laden macrophages
(arrowhead) adjacent to papillary structures covered by endometrial
epithelium, with scattered squamous morules (arrows), which meet
criteria for diagnosis of endometriosis.
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Discussion
Endometriosis affects millions of women worldwide. Prevalence figures
quoted are 0.5–5% in fertile and 25–40% in infertile women
[1] or 10% of all women in the
reproductive age group [2].
Although endometriosis is one of the most common human diseases, central
nervous system involvement is rare.
To our knowledge, only two previous cases of cerebral endometriosis have
been described. The first was a 20-year-old woman with intermittent headaches
and seizures. CT showed a ring-enhancing lesion, and a chocolate-colored cyst
was resected from the right parietal lobe
[4]. The second was a
31-year-old woman with a right inferior posterior parietal lesion causing
catamenial partial seizures
[5]. To our knowledge, our case
is the first report of endometriosis in the cerebellum.
Central nervous system involvement is slightly more frequent in the spine.
Cyclical symptoms related to menstruation are often present in patients with
central nervous system involvement. One report describes menstruation-related
headaches, papilledema, and unresponsiveness caused by cryptogenic
subarachnoid hemorrhage from ectopic endometrial tissue in the spine
[8]. However, our patient did
not have cyclical symptoms, and the possibility of endometriosis was not
considered on imaging.
Endometriotic cysts (or endometriomas) are generally described in the
pelvis, resulting from repeated cyclic hemorrhage in a deep implant
[2]. The MRI diagnosis of
pelvic endometriosis relies on detection of hemorrhagic products, with signal
characteristics varying according to stage. Typically, hemorrhagic lesions are
hyperintense on T1-weighted images and hypointense on T2-weighted images. This
T2 shortening is known as the "shading" sign and has been
described as a distinguishing feature of endometriomas on MRI
[3]. The most common
manifestations are complete loss of signal or layering with a dependent fluid
level that is hypointense.
Such hypointense dependent fluid levels were seen in our patient on MRI
(Figs. 1C and
1D), although preoperatively it
was not recognized as endometriosis. In retrospect, the imaging appearance of
this rare example of endometriosis in the brain bears remarkable similarity to
the MRI features of endometriomas in the pelvis. The shading sign, or any
evidence of hemorrhage in a cystic lesion, should alert radiologists to the
possibility of endometriosis even in rare locations.
It is interesting to speculate on the pathogenesis of the endometrial
tissue found in the central nervous system in these isolated cases. Although
endometriosis is one of the most frequent problems in gynecology, its
pathogenesis remains controversial and poorly understood. The earliest
hypothesis is the metaplastic theory, which acknowledges the putative
müllerian potential of the pelvic peritoneum. This theory, however, does
not explain endometriosis in tissues in which müllerian potential does
not exist. The theory most frequently cited is autotransplantation, which is
thought to occur by retrograde menstruation through the fallopian tubes into
the peritoneal cavity and by lymphatic, vascular, and iatrogenic
dissemination. A third hypothesis is a combination of the first two,
suggesting that tissue factors released by shed endometrium can induce
undifferentiated mesenchyme to form endometrial tissue.
Iatrogenic transplantation of endometrial tissue is a known phenomenon, as
seen with the involvement of surgical scars. The presence of a
ventriculoperitoneal shunt in our patient raises the possibility of the shunt
serving as a conduit for endometrial cells to reach the brain. To our
knowledge, such an occurrence has never before been reported, and the lack of
ventricular involvement does argue against this possibility.
Autotransplantation through a hematogenous route therefore appears to be a
more plausible theory. Although our patient had no pelvic symptoms,
asymptomatic pelvic implants are known to occur. The exact pathogenesis of
endometriosis in this rare location, however, remains a source of
speculation.
In summary, endometriosis of the brain is a rare condition that can occur
without cyclical symptoms related to menstruation. This example in the
cerebellum has features bearing remarkable similarity to MRI appearances of
pelvic endometriomas. The shading sign on MRI or any other evidence of
hemorrhage in a cystic lesion in a female patient, should alert the
radiologist to the possibility of endometriosis even in unusual sites. The
final diagnosis in such rare locations can, of course, only be made by
pathologists.
Acknowledgments
We thank our gynecologic pathologists William Chapman and Patricia Shaw for
reviewing the slides and offering their thoughts on the diagnosis.
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Introduction
Case Report
