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: r.goncalves@liv.ac.ukReceived 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.

REFERENCES

1. Summers BA, Cummings JF, de Lahunta A. Tumours of the centralnervous system. In: Summers BA, Cummings JF, de Lahunta A (eds): Vet-erinary neuropathology. St. Louis: Mosby, 1995;352–355.

2. Wang Y, Gao X, Yao Z, et al. Histopathological study of five caseswith sporadic meningioangiomatosis. Neuropathology 2006;26:249–256.

3. Stebbins KE, McGrath JT. Meningioangiomatosis in a dog. VetPathol 1988;25:167–168.

4. Ribas JL, Carpenter J, Mena H. Comparison of meningioangio-matosis in a man and a dog. Vet Pathol 1990;27:369–371.

5. Pumarola M, Martin de Mulas J, Vilafranca M, Obach A. Meningio-angiomatosis in the brainstem of a dog. J Comp Pathol 1996;115:197–201.

6. Lorenzo V, Pumarola M, Munoz A. Meningioangiomatosis in a dog:magnetic resonance imaging and neuropathological studies. J Small AnimPract 1998;39:486–489.

7. Bishop TM, Morrison J, Summers BA, deLahunta A, Schatzberg SJ.Meningioangiomatosis in young dogs: a case series and literature review.J Vet Intern Med 2004;18:522–528.

8. Goates JJ, Dickson DW, Horoupian DS. Meningioangiomatosis: animmunocytochemical study. Acta Neuropathol 1991;82:527–532.

9. Wiebe S, Munoz DG, Smith S, Lee DH. Meningioangiomatosis:a comprehensive analysis of clinical and laboratory features. Brain1999;122:709–726.

10. Park MS, Suh DC, Choi WS, Lee SY, Kang GH. Multifocal men-ingioangiomatosis: a report of two cases. Am J Neuroradiol 1999;20:677–680.

11. Kim WY, Kim IO, Kim S, Cheon JE, Yeon M. Meningioangio-matosis: MR imaging and pathological correlation in two cases. PediatrRadiol 2002;32:96–98.

12. Tien RD, Osumi A, Oakes JW, Madden JF, Burger PC. Men-ingioangiomatosis: CT and MR findings. J Comput Assist Tomogr 1992;16:361–365.

13. Meltzer CC, Liu AY, Perrone AM, Hamilton RL. Meningioangio-matosis: MR imaging with histopathologic correlation. Am J Roentgenol1998;170:804–805.

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