IMAGING DIAGNOSIS—CANINE MENINGIOANGIOMATOSIS
RITA GONcALVES, PAMELA JOHNSTON, ANNETTE WESSMANN, JACQUES PENDERIS
Meningioangiomatosis is a rare proliferative disorder of the central nervous system. It occurs sporadically in
dogs and is characterized by a leptomeningeal plaque that extends from the subarachnoid space along the
perivascular spaces into the adjacent parenchyma. We describe the clinical presentation, magnetic resonance
(MR) imaging and neuropathologic characteristics of two additional dogs with meningioangiomatosis, and
document involvement of the thoracolumbar spinal cord, a site not previously described for this condition. MR
imaging findings were different from those previously described, most likely reflecting the degree of vascularity
and collagen deposition. The MR imaging features of meningioangiomatosis are not specific. r 2010Veterinary Radiology & Ultrasound, Vol. 51, No. 2, 2010, pp 148–151.
Key words: dog, meningioangiomatosis, MRI.
Signalment and Clinical Findings
Dog 1
A4-YEAR-OLD male Boxer was examined for a 2-month
history of progressive paraparesis and fecal
incontinence. There was paraparesis which was worse on
the left, with absent conscious proprioception in both pelvic
limbs, intact limb segmental spinal reflexes and a cutaneous
trunci reflex cut-off at the level of the first lumbar vertebra.
Dog 2
A 5-month-old female Labrador was examined for a 3-
month history of progressive central vestibular signs. There
was ataxia with leaning to the right and a head tilt to the
right. Conscious proprioception was reduced in all limbs.
There was also positional ventral strabismus in the right
eye as well as positional rotatory nystagmus with the fast
phase to the left. Anisocoria was present, with the left pupil
dilated and only partially light responsive. Cisterna magna
cerebrospinal fluid analysis was unremarkable.
Imaging
Magnetic resonance (MR) imaging was performed using
a 1.5T system.� The following pulse sequences were
acquired: T1-weighted pre- and postcontrast (0.1mmol/
kg gadopentetate dimeglumine),w T2-weighted, fluid atten-
uated inversion recovery (FLAIR) and gradient echo
sequences (GRE).
Dog 1
There was an intramedullary lesion at the level of the
13th thoracic vertebra, which was hyperintense on T2-
weighted images with a hypointense center on T2-weighted
and FLAIR images, mildly hyperintense on T1-weighted
and GRE images, and with homogenous contrast enhance-
ment (Fig. 1A–F). Considerations included a vascular
malformation, neoplastic, inflammatory, and infectious
disease.
Dog 2
There was a lesion on the left ventral aspect of the
brainstem that was hyperintense on T2-weighted, FLAIR
and GRE images and isointense on T1-weighted images,
with mild, patchy contrast enhancement (Fig. 2A–D). In-
flammatory and infectious disease were considered most
likely but a developmental anomaly and tumor were also
considered.
Outcome
Dog 1 underwent euthanasia immediately after imaging.
Dog 2 underwent euthanasia after not improving following
4 weeks of corticosteroid therapy.
Pathologic Findings
In Dog 1 a wedge-shaped lesion in the thoracolumbar
spinal cord extended from the leptomeninges on the leftAddress correspondence and reprint requests to Rita Goncalves, at the
above address. E-mail: [email protected] June 17, 2009; accepted for publication October 8, 2009.doi: 10.1111/j.1740-8261.2009.01640.x
From the Department of Veterinary Clinical Sciences, University ofLiverpool, Leahurst, Chester High Road, Neston CH64 7TE, UK(Goncalves), Division of Companion Animal Sciences (Johnston, Wessm-ann, Penderis), and Division of Pathological Sciences (Johnston), Facultyof Veterinary Medicine, University of Glasgow, Bearsden Road, GlasgowG61 1QH, UK.
�Gyroscan ACS NT, Philips Medical Systems, Eindhoven, the Neth-erlands.
wBerlex, Montville, NJ.
148
side to the midline, at the level of the cranial portion
of T13. There was infiltration that extended from the
leptomeninges into the spinal cord parenchyma (Fig. 1G–
I). The lesion was composed of high numbers of prolifer-
ating small blood vessels lined by flattened endothelial
cells admixed with spindloid cells (Fig. 3A). No mitotic
figures were seen. Centrally within the lesion, vessels and
spindloid cells were separated by collagen. The spindloid
cells were vimentin positive, establishing their mes-
enchymal origin, and were negative for von Willebrands
Factor, glial fibrillary acidic protein and S100. The com-
pressed spinal cord was characterized by loss of normal
architecture, gliosis, white matter vacuolation and loss of
large motor neurons. These findings were diagnostic of
meningioangiomatosis.
Dog 2: Histopatholigic findings were similar to those in
Dog 1 (Figs. 2E–F and 3B).
Discussion
Meningioangiomatosis is a rare, benign, focal lesion of
the leptomeninges and underlying neural parenchyma
characterized by leptomeningeal and meningovascular pro-
liferation. Grossly, there is a visible plaque composed of
proliferative meningothelial or fibroblastic spindle-shaped
cells that extends from the subarachnoid space along the
perivascular spaces into the adjacent parenchyma.1 Men-
ingioangiomatosis was first described in 1915 and there are
only about 100 documented occurrences in humans, either
sporadically or in association with neurofibromatosis type
2.2 There are eight reports of meningioangiomatosis in
dogs.3–7
The origin of meningioangiomatosis is not known. It has
been classified by some as a hamartomatous proliferation
of meningothelial cells, blood vessels and fibroblasts in
variable proportions. Because of the abnormal local vas-
cularization, others consider it to be a vascular malforma-
tion that induces perivascular meningothelial proliferation
of cells from vessel walls or from pluripotent arachnoid cap
cells in Virchow–Robin spaces. Immunohistochemical
studies have not supported a meningothelial origin for
the perivascular cells and suggested that pluripotent cells
could differentiate into the various cell types.8,9 It has also
been suggested to result from direct invasion of brain by a
leptomeningeal meningioma, despite the lack of character-
istic features of malignancy.
In humans, lesions of meningioangiomatosis are usually
located in the frontal or temporal lobe, but are occasionally
in the brainstem; spinal cord involvement has not been
identified in people.9 These lesions are typically solitary but
multifocal lesions have been reported.10 Similar to dog 2,
most intracranial lesions of meningioangiomatosis are lo-
cated in the brainstem, which is the proposed predilection
site in dogs.7 In Dog 1, the thoracic spinal cord was
affected, demonstrating that lesions of meningioangio-
matosis can affect both the intracranial and spinal com-
ponents of the central nervous system.
Fig. 1. Sagittal (A–C) and transverse (D–F) T2-weighted (A, D), T1-weighted (B, E) and T1-weighted postcontrast images (C, F) of the thoracolumbar spineof Dog 1. There is a T1- and T2-heterogeneous intramedullary lesion at the level of T13 on the left side, with marked contrast enhancement. The histopathologicsections are stained with H&E (G), modified Masson’s Trichrome (H), and immunohistochemistry with von Willebrands factor (I). The lesion is welldemarcated (G), with increasing amounts of collagen toward the center (H) and proliferation of endothelial cells (I) (�1.5).
149MRI OF MENINGIOANGIOMATOSIS IN DOGSVol. 51, No. 2
The MR imaging findings of meningioangiomatosis are
variable. In humans, the most common findings are
T1-isointensity or T1-hypointensity and a heterogeneous
appearance on T2-weighted images, with low or mixed
T2-signal surrounded by an area of T2-hyperintensity and
variable contrast enhancement, depending on the vascu-
larity of the lesion.2,11 The T1-hypointensity is often
the result of areas of calcification, which is not a feature
of the canine lesions, or in regions with a dense fibrovas-
cular component.12 The T2-hypointense center is thought
to be attributable to dense collagen13 and the T2-
hyperintense rim to edema or gliosis.11 Not all human
patients with meningioangiomatosis have lesions on MR
images.9
MR imaging features of intracranial meningioangio-
matosis in dogs include T1-hyperintensity or T1-isointen-
sity, T2-hyperintensity, and strong contrast enhancement.6,7
Our dog with the brainstem lesion differed due to the
lack of homogenous contrast enhancement, with MR
images most suggestive of an ill-defined inflammatory
lesion rather than a mass lesion. The degree of contrast
enhancement is likely to vary according to the degree of
vascularity of the lesion. The MR features of spinal lesions
have not been previously reported. The lesion in our dog
had mixed T2-signal, with the hypointense center coincid-
ing with collagen deposition, mild T1-hyperintensity and
strong contrast enhancement. The MR imaging features of
meningioangiomatosis are dependent on the developmen-
tal histologic status of each individual lesion and are not
specific.2
The variability in the clinical presentation and imaging
features of meningioangiomatosis can impede reaching the
Fig. 2. Sagittal T2-weighted (A), and T1-weighted postcontrast (B), transverse T2-weighted (C) and transverse FLAIR (D) images of the brain of Dog 2.There is an ill-defined T2-hyperintense lesion, with patchy contrast enhancement. The histopathologic sections are stained with H&E (E) and immunohis-tochemistry with vimentin (F). The lesion is also relatively well demarcated and diffusely expresses vimentin (F) (�1.5).
150 GONc� ALVES ET AL. 2010
correct diagnosis. Meningioangiomatosis should be con-
sidered in dogs with progressive central nervous system
disease, an MR lesion, but absence of an inflammatory
component. Most notably, it is important to recognize that
the MR imaging features of meningioangiomatosis are
variable and not specific.
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Fig. 3. (A) Left lateral aspect of T13 spinal cord segment of dog 1; the leptomeninges are expanded by a plaque of spindloid cells and small blood vessels.(B) Ventromedial aspect of the midbrain of dog 2. Note the leptomeningeal plaque of spindloid cells and small blood vessels, which invade the neuralparenchyma along the perivascular spaces (H&E, �200).
151MRI OF MENINGIOANGIOMATOSIS IN DOGSVol. 51, No. 2
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